Peripheral Nerve Repair and Regeneration

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Hyperbaric oxygenation in peripheral nerverepair and regeneration

E Cuauhtemoc Sanchez

Hyperbaric Medicine Department Hospital Angeles del Pedregal Mexico City DF Mexico

Peripheral nerves are essential connections between the central nervous system and musclesautonomic structures and sensory organs Their injury is one of the major causes for severe andlongstanding impairment in limb function Acute peripheral nerve lesion has an importantinflammatory component and is considered as ischemia-reperfusion (IR) injury Surgical repairhas been the standard of care in peripheral nerve lesion It has reached optimal technicaldevelopment but the end results still remain unpredictable and complete functional recovery israre Nevertheless nerve repair is not primarily a mechanical problem and microsurgery is notthe only key to success Lately there have been efforts to develop alternatives to nerve graftWork has been carried out in basal lamina scaffolds biologic and non-biologic structures incombination with neurotrophic factors andor Schwann cells tissues immunosuppressiveagents growth factors cell transplantation principles of artificial sensory function genetechnology gangliosides implantation of microchips hormones electromagnetic fields andhyperbaric oxygenation (HBO) HBO appears to be a beneficial adjunctive treatment for surgicalrepair in the acute peripheral nerve lesion when used at lower pressures and in a timely fashion(6 hours) [Neurol Res 2007 29 184ndash198]

Keywords Peripheral nerve injury nerve repair nerve regeneration hyperbaric oxygenationgrowth factors ischemia-reperfusion injury

INTRODUCTIONReports of acute nerve injury can be traced to3500 years ago in a biblical story1 In the seventhcentury Paulus Aegineta was the first to report the useof suture and agglutination to repair nerves2 Thepioneer of peripheral nerve surgery was GabrieleFerrara who described the technique of suturing stumpsof a transected nerve3

Dysfunction of peripheral nerves results from damageto the neuron to the Schwann cells or to the myelinsheath4 Many mechanisms of injury to peripheralnerves exist including mechanical damage crushinjury lacerations penetrating trauma stretch injuryhigh-velocity trauma frostbites and iatrogenic injury5Peripheral nerve injuries are relatively common6 Theyare one of the major causes for severe and longstandingimpairment of limb function and remain as one of themost challenging and difficult reconstructive problems Iwill classify the degree of injury describe the surgicalrepair options and discuss adjunctive therapies includ-ing hyperbaric oxygen

CLASSIFICATION OF PERIPHERAL NERVE INJURYThe classification of nerve injury was described bySeddon7 and later expanded by Sunderland and

Bradley2 and Mackinnon and Dellon8 The first-degreeneuropraxia involves a temporary conduction blockwith demyelination of the nerve at the site of injury It is adysfunction andor paralysis without loss of nerve sheathcontinuity and peripheral Wallerian degenerationElectrodiagnostic study results are normal above andbelow the level of injury and no denervation musclechanges are present No Tinelrsquos sign is present Completerecovery occurs once the nerve has remyelinated at thedamage area Recovery may take up to 12 weeks59

A second-degree injury axonotmesis results from amore severe trauma or compression The internalarchitecture is relatively preserved and can guideproximal axonal regeneration to reinnervate distal targetorgans10 This causes Wallerian degeneration distal tothe level of injury and proximal axonal degeneration to atleast the next node of Ranvier In more severe traumaticinjuries it could extend beyond the next node Electro-diagnostic studies demonstrate denervation changes inthe affected muscles and in cases of reinnervation motorunit potentials (MUPs) are present5

In the third-degree injuries axon continuity isdisrupted by loss of endoneurial sheaths but theperineurium is preserved9 It is a more severe injurythan the second-degree Wallerian degeneration occursand electrodiagnostic studies demonstrate denervationchanges with fibrillations in the affected musclesBecause the endoneurial tubes are not intact theregenerating axons may not reinnervate their originalmotor and sensory targets5

Correspondence and reprint requests to E Cuauhtemoc Sanchez MDHyperbaric Unit Director Hyperbaric Medicine Department HospitalAngeles del Pedregal Mexico City DF 10700 Mexico [crosatimedovatecom] Accepted for publication 27 April 2006

184 Neurological Research 2007 Volume 29 March 2007 W S Maney amp Son Ltd101179016164107X181824

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In the fourth-degree injury the nerve fasciculi aredamaged but nerve sheath continuity is preserved59 Itresults in a large area of scar at the site of nerve injuryand precludes any axon from advancing distal to thelevel of nerve injury Electrodiagnostic studies revealthat denervation changes the affected muscles and noMUPs are present No improvement of function is notedand the patient requires surgery to restore neuralcontinuity thus permitting axonal regeneration andmotor and sensory reinnervation5

In the fifth-degree injuries there is a complete tran-section of the nerve They correspond to Seddonrsquosclassification of a neurotmesis lesion It requires surgeryto restore neural continuity Electrodiagnostic studiesare the same as in the fourth-degree injury59Mackinnon introduced a sixth-degree injury to describea complex peripheral nerve injury It is a mixed nerveinjury that combines the other degrees of injury9

PATHOPHYSIOLOGYThe physiologic response is different depending on thetype of injury If the axon is spared as in the first-degreeinjury conduction is interrupted due to demyelinationbut is reinstated whenever the aggravating stimulus isremoved and the myelin layers are restored If the axonor more is transected causing a second- to fifth-degreeinjury the response has two main phases degenerationand regeneration and takes substantially longer11Pathologically three phases were identifiable phase 1(0ndash3 hours) minimal pathologic changes and minimaledema phase 2 (7ndash14 days) prominent fiber degenera-tion and endoneurial edema and phase 3 (28ndash42 days)abundant small regenerating fiber clusters and minimaledema12

The first phase of axon injury degeneration was firstdescribed by Waller in 1850 (Ref 13) Following injurychanges occur in the cell body axon and the Schwanncell Both distally and proximally the axon begins todisintegrate and undergoes apoptosis Local Schwanncells and macrophages clean up the apoptotic debriscreating long clean endoneurial tubes Once the debrishas been removed Schwann cells proliferate andorganize themselves into columns that lie within theendoneurial tubes creating the bands of Bunger81114

After injury there is a great increase in the productionof mRNA and proteins15 These products are transporteddown the axon providing the material and energyfor nerve elongation to the distal tip The severedaxons begin to sprout and contain an expanded regionknown as the growth cone This is the site of axonelongation and sends out many small processes thatseek specific markers which influence the axon in itsmovements to preferentially select neural tissue andeven exhibit a preference for endoneurial tubes with thesame function16

The axonrsquos response is regulated by neurotrophicfactors that direct and attract the axon17 Neurotrophicfactors induce maturation and elongation of the axon14They are released by macrophages Schwann cells andother supporting cells

If the nerve is too far away the axons are not stronglyattracted to the distal end and eventually stop advan-cing causing aberrant innervation at the end organlevel1417

Large gaps greater than 15 mm cannot be crossedreliably by axons This is usually because proliferatingSchwann cells or fibroblasts grow between the severenerve ends and form a physical blockage18 If the axonsprouts stop proliferating and take residence in a dif-ferent tissue they will form a neuroma19

Neuroinflammation in primary demyelination andWallerian degeneration is an ischemia-reperfusion(IR) injury and is mediated by cytokines and otherimmune mediators (Figure 1)121320ndash36 IR injury con-tributes to both axonal degeneration and regeneration13Reperfusion by oxidative injury worsened nerve func-tion and aggravated fiber degeneration but in the longertime frame permitted fiber regeneration to occur12

During peripheral nerve injury hypoxia createsseveral cellular shock stages that could be reversibleor irreversible The reversibility depends on the cellscapability to maintain adenosine-5rsquo-triphosphate (ATP)production3738 Once ATP production is stopped thecell can no longer maintain the homeostatic functionsThis produces cytotoxic edema and release of calciumby the mitochondria39

ATP has many important functions on peripheralnerve repair and regeneration It is important tomaintain cellular functions and is also the energy sourcefor axoplasmic transport It is indispensable for thetransport of nerve growth factors (NGF)40 There is apotential interplay between ATP and NGF in thesignaling pathways triggered on their target cells41ATP has neuritrogenic and trophic effects which arecomparable to those sustained by NGF and involveseveral overlapping pathways42 ATP exerts a protectiveeffect on the neurons which is valuable for nerveregeneration after nerve injury42

NERVE REPAIRThe surgical reconstruction of peripheral nerve damageis crucial Although the surgical procedure may beoptimal and an excellent rehabilitation program isconducted the end results still remain unpredictableand complete functional recovery is still rare43 A nervelesion is different from other tissue injury because itrequires more than only local processes Transection ofaxons has implications for the whole length of theneuron and the repair process involves outgrowth ofneurites over very long distances In addition a nerveinjury in contrast to most other injuries of the body hasimmediate functional consequences for the brain interms of rapid functional reorganization in braincortex43

From the biologic point of view the physiologic resultfollowing nerve injury and repair is dependent onfactors such as the extent of nerve cell survival after theinjury the rate and quality of axonal outgrowth theorientation and specificity in growth of regenerationaxons the survival and state of end organs and cortical

HBO in peripheral nerve repair and regeneration E C Sanchez

Neurological Research 2007 Volume 29 March 185

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reorganizational processes in somatosensory and motorbrain cortex From the clinical viewpoint the outcomeis often incomplete as expressed in symptoms such aspoor and abnormal sensory function deficient motorfunction cold intolerance pain impaired functionquality of life and problems at work leisure and insocial life43

The surgical approximation of severed nerve ends hasreached the most desirable technical refinementNevertheless nerve repair is not primarily a mechanicalproblem and microsurgery is not the only key tosuccess At most the surgeon can manage to co-aptindividual groups of fascicles but the behavior of theseparate axons inside individual fascicles cannot beaddressed as they are regulated by biologic mechanismsat the molecular level43

Autologous nerve graft remains the standard of carehowever much effort is now focused on developingalternatives directed to the biologic mechanisms insideWork has been carried out in basal lamina scaffoldsbiologic and non-biologic structures in combinationwith neurotrophic factors andor Schwann cells tissues

immunosuppressive agents reimplantation of avulsednerve roots (brachial plexus surgery) and end-to-sideanastomosis

Other biologic factors may also be important tools topromote survival and regeneration processes of thesevered ends and improve the functional results Thishas spearheaded new research into growth factors celltransplantation principles of artificial sensing genetechnology gangliosides implantation of microchipshormones electromagnetic fields and hyperbaric oxy-genation (HBO) as potential adjuvant therapiesNevertheless these therapies have gained very limitedclinical application

SURGICAL ASPECTS OF NERVE REPAIRThe purpose of the surgical reconstruction is to align theproximal and distal nerve segments In the last 30 yearsthere has been great advancement in the technicalaspects of nerve reconstruction44ndash56 Direct muscularneurotization has been used for cases where the nervehas been avulsed from the muscle and the repair is

Figure 1 The core of the inflammatory cascades is the reduction of energy and subsequent mitochondrial dysfunction They are verycomplicated and have several interactions between them The only feasible way to stop the cascades is the timely restitution ofenergy before they all lsquokick inrsquo This could be accomplished with the prompt application of hyperbaric oxygenation (HBO) It couldexplain the efficacy of HBO in the ischemia-reperfusion injury


186 Neurological Research 2007 Volume 29 March

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impossible49 The reimplantation of avulsed nerve rootswith subsequent functional recovery has been tried forbrachial plexus lesions in selected cases5057

Autologous nerve graftsAlthough this remains the gold standard in peripheral

nerve repair and regeneration autologous nerves are inlimited supply with the sural nerve graft being theprimary source58 The purpose of such grafts is toprovide a guide or conduit consisting of a basal laminaand Schwann cells that support axonal regenerationThe thickness of the graft is important so that itguarantees enough Schwann cells to synthesize neuro-trophic factors laminin and fibronectin in the basallamina59ndash61 They have also been used in combinationwith autologous fibrin glue containing large number ofplatelets62

Another technique developed to improve axonaloutgrowth is the pre-degeneration of the nerve graftthat reduces the latency of repair63 Vascularized nervegrafts have also been described for extensive gapsespecially in crush injuries with massive skin defectsand poor blood supply Selective regeneration of motorand sensory axons has also been attempted64

Nerve allograftsNerve allografts have been extensively investigated

but they require heavy immunosuppression to avoidrejection and failure65ndash68 Normally this is accom-plished with the use of cyclosporine and prednisoneAcellular allografts have been tried to reduce immuno-genicity There is still limited clinical experience of itsuse69

Basal lamina scaffolds from muscleAny biologic tissue that contains basal lamina may

serve as a bridge for nerve regeneration Frozen andthawed muscle grafts have been used to bridge gaps innerve continuity7071 Regenerating axons grow readilyinto the empty basal lamina cylinders of such graftscontaining laminin and fibronectin4372 Migration ofSchwann cells into the grafts is essential73 There is acritical length for the use of such grafts however withthe introduction of a small nerve segment in the middleof the muscle graft the conduits can be provided withan intermediate depot of Schwann cells to improve itsregenerating potential74 There have been some clinicaltrials that have failed once they reach a critical lengthprobably due to insufficient supply of cells andneovascularization75

Other types of conduitsVenous grafts have been successful in bridging gaps

in nerve continuity76 Various types of bioreabsorbabletubes have been used to bridge defects77 Silicone tubescan only be used together with various types of factorscells and materials to improve regeneration78 Animalmodels with multiple longitudinal synthetic filaments inthe lumen have been used successfully to bridge

extended nerve gaps79 Good results have also beenreported in experimental models using biologic materi-als such as collagen as an extracellular matrix80 Otherbiologic grafts successfully used are biodegradablecollagen grafts81 with laminin82 and fibronectin83 whichproduce neurite-promoting factor84 and axonal enloga-tion85 teased tendons formed into a loose collagenroll86 freeze-dried alginate gels87 chitosan-PLA com-posite88ndash90 90 PLA10 PLG nerve guides9192 glutar-aldehyde cross-linking gelatin conduit93 and expandedpolytetrafluoroethylene tubes with autogenous vein94

Terminolateral anastomosisEnd-to-side anastomosis has been proposed in situa-

tions in which the proximal segment of a severed nervetrunk is not available95 It is used to induce collateralsprouting from intact axons in the healthy nerve Thecollateral sprouts from the donor nerve will reinnervatethe distal segment of the injured nerve trunk96 Animalexperimental models have shown good ingrowth insensory and motor fibers97ndash101

NEUROTROPHIC FACTORSThere has been substantial development in the field ofneurotrophic factors The cellular and molecular basisfor the survival and outgrowth of neurons shows anenormous complexity102ndash104 The key factor for theregeneration following axotomy is the survival of nervecell bodies which is facilitated by multiple neurotrophicfactors These factors are divided into three majorgroups the neurotrophins neuropoietic cytokines andfibroblast growth factors105ndash108 There are additionalgroups of neurotrophic factors such as the insulin-likegrowth factor epidermal growth factor109110 leukemia-inhibiting factor glial-derived neurotrophic factor111transforming growth factor-beta 1 (TGF-b1)112 andpleiotrophin113

The actions of growth factors are exerted by theirbinding to particular classes of tyrosine kinase (Trk)receptors and a low-affinity NGF present on the surfaceof the responsible cells Intracellular signaling andsubsequent gene activation follow the activation of thereceptor site (ATP is needed for this process)

The neurotrophin family includes NGF brain-derivedneurotrophic factor (BDNF) neurotrophin-3 (NT-3)neurotrophin-45 (NT-45) and neurotrophin-6 (NT-6)43 NGF mRNA is constituently expressed in healthynerves and up-regulated following nerve injury in thedistal segments114 Trophic factors are transmitted bythe retrograde transport along the axon and used tosustain survival and essential activities of the nerve cellbody115 Macrophages are important not only in myelindegradation and nerve remodeling but also in theproduction of neurotrophic factors after nerve injuryprobably through the release of interleukin-1b (IL-1b)116 Schwann cells in the injured nerve trunk alsoproduces growth factors such as NGF117 insulin-likegrowth factor118 ciliary neurotrophic factor119 andBDNF120 Glial cell line-derived neurotrophic factor



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(GDNF) stimulates Schwann cells to migrate andenhances myelination121

NGF has a key role in sensory neurons survival andneurite outgrowth but has almost no influence on motorneurons122 NGF can only influence neurons with high-affinity NGF receptor (TrkA) Motor neurons do notcontain TrkA receptor genes and they respond only toTrkB and TrkC

BDNF supports survival of motor neurons in cultureand acts as a trophic factor123 In anterior spinal horns itprevents cell death following axotomy124 Its effects aremediated by TrkB and TrkC receptors

NT-3 binds to TrkC receptors and promotes survivalin sensory and motor neurons and differentiation res-ponses in sensory and parasympathetic neurons41121NT-45 binds to TrkB receptors in motor neurons sup-ports survival and increases the ability of motor neuronsto innervate skeletal muscle fibers in co-cultures in ratspinal cord and human muscle124125 NT-6 acts pre-ferably on sympathetic and sensory neurons126

OTHER FACTORSSeveral other factors can facilitate the regeneration ofnerve cell bodies and are being developed as putativeadjunctive therapies to autologous nerve grafts

BetamethasoneBetamethasone has been systemically administered

perioperatively to enhance nerve recovery after inducednerve crush injury Short-term perioperative administra-tion of betamethasone has a beneficial effect on therecovery of the injured rat sciatic nerve127

Pyrroloquinoline quinonePyrroloquinoline quinone (PQQ) has been tested in

animal models to promote nerve regeneration oftransected sciatic nerve It has a remarkable effect onnerve regeneration sciatic nerve function sciatic nervefunction index electrophysiologic index and morpho-logic appearance128

Hypothalamic proline-rich peptideProline-rich peptide-1 (PRP-1) is produced by neuro-

secretory cells of hypothalamic nuclei (paraventricularnucleus and supraoptic nucleus) 3 and 4 weeks follow-ing rat sciatic nerve transection Histochemical andelectrophysiologic findings provide evidence for rein-nervation of the injured side by complete coalescenceof transected fibers together with restoration of themotor activity129

Low-dose FK506 and anti-CD40 ligandLow-dose immunomodulatory agents (FK506) in

combination with anti-CD40 ligand used in mice withtibial nerve grafting exhibited robust nerve regenerationwithout disrupting immune unresponsiveness130

Thrombin and peptide thrombin receptor agonist PAR1Experiments demonstrate a dose-dependent facilitat-

ing effect of thrombin and thrombin receptor agonistPAR1 (TRAP6) on regeneration of mouse peripheralnerve after crush injury The maximal neurotrophiceffect was observed at low concentrations131

TriiodothyronineLocal administration of triiodothyronine (T3) at the

level of transected rat sciatic nerve increases thenumber and diameter of regenerated axons Local T3treatment significantly enhances the expression ofsuperior cervical ganglion 10 a regulator of micro-tubule dynamics in growth cones that could provide amechanism by which T3 enhances peripheral nerveregeneration132

Neuroactive steroidsProgesterone dihydroprogesterone tetrahydropro-

gesterone dihydrotestorenone and 3 alpha-diol stimu-late the expression of two important proteins of themyelin of peripheral nerves the glycoprotein Po andthe peripheral myelin protein 22 Neuroactive steroidsnot only control the expression of these proteins butalso influence the morphology of myelin sheaths andaxons133

Peripheral benzodiazepine receptorPeripheral benzodiazepine receptor (PBR) expression

increases in small dorsal root ganglion sensory neuronsafter peripheral nerve injury It has a role in the earlyregenerative response of small caliber sensory axons134

Activating transcription factor 3Peripheral nerve compression induces nuclear trans-

location of activating transcription factor 3 (ATF3) atranscription factor associated with survival and regen-eration of sensory neurons The response is related toduration of compression and partly correlated tofunction135

Cell adhesion moleculesAdhesion molecules such as N-CAM L1 the myelin-

associated glycoprotein and transient axonal glycopro-tein-1 correlate with axonal growth advancement andregeneration136137

77 kDa muscle-derived proteinHistologic and immunohistochemical evaluations

suggested that 77 kDa muscle-derived protein(MDP77) treatment accelerates Schwann cell migrationfollowed by enhanced maturation of regeneratingaxons resulting in functional recovery of both thenerves and the atrophied denervated muscle in rats138

Galectin-1Galectin-1 (gal-1) was the first identified member

of the galectin family of beta-galactosidase-binding



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proteins released by Schwann cells It has beenimplicated in the regenerative response of axonsfollowing peripheral nerve injury Gal-1 has beenshown to promote axonal regeneration through theactivation of macrophages to secrete an axonalregeneration-promoting factor139ndash141

Transplanted cellsTransplantation of Schwann cells bone marrow

stromal cells mesenchymal cells and pluripotentembryonic stem cells has demonstrated contributionto myelin repair142ndash149

Regeneration-associated geneAfter peripheral nerve axotomy a sequence of

events including glial activation and axonal regrowthleads to functional recovery of the afflicted pool ofmotoneurons As a consequence of nerve injurythere is an increase in the expression of 60 genes withthe sustained up-regulation of one specific geneencoding the hematological and neurological expressedsequence-1 It is associated with nervous systemdevelopment and nerve regeneration150

ElectroacupunctureIn a model of crushed sciatic nerve in rabbits

electroacupuncture promoted nerve regeneration151

Low-frequency pulsed electromagnetic fieldLow-frequency pulsed electromagnetic field (PEMF)

was ineffective on rat sciatic nerve regeneration in amodel of crushed sciatic nerve in rats152

Low intensity ultrasoundLow intensity ultrasound (LIUS) in combination with

poly(DL-lactic acid-co-glycolic acid) conduits wasfound to have significantly greater number and area ofregenerated axons at the mid-conduit of implantedgrafts LIUS stimulation on silicone groups was found toinduce a mass of fibrous tissues that covered the nerveconduits and retarded axon regeneration153

HBOHBO is an approved adjunctive treatment for severalconditions154 It has proven to be an effective treatmentin the IR injury155ndash158 HBO reduces the IR injurythrough several mechanisms First through hyperox-ygenation its primary mechanism of action it maintainsthe viability of the marginal tissue (penumbra)159 Thishyperoxygenation also creates other secondarymechanisms that are responsible for wound healingand neovascularization159 When used in a timelyfashion it can modify the pathophysiology of the IRinjury155

Increase in oxygen tensions allows the tissues tomaintain ATP and other high energy compounds levelsIt re-establishes aerobic metabolism and inhibits theelevation of lactate levels Others have shown that HBO

restores not only ATP levels but also creatine phos-phokinase guanosine triphosphate and uridine tripho-sphate160ndash162 HBO promotes the production ofgluthathione the principal non-enzymatic body defenseagainst reactive oxygen species (ROS)160

HBO reduces the liberation of calcium and thus theincrease in phospholipase A2 and cyclooxygenase-2The protection exerted through the blockage of thearachidonic acid cascade with the subsequent reduc-tion of leukotrienes thromboxanes and prostaglandinsprotects against the no flow state of the IR injury163164By blocking nuclear transcription factor kappa B HBOreduces the inflammatory response created by its up-regulation It reduces substantially the production of theproinflammatory cytokines especially IL-1 IL-6 IL-8tumor necrosis factor alpha (TNFa) interferon gamma(IFNc) and platelet activating factor (PAF)165ndash179

HBO can inhibit the conversion of xanthine oxidasereducing the oxidative stress in the reperfusion stage ofIR injury177 This effect prevents the production of ROSand tissue damage HBO also prevents endothelialdamage and the expression of intercellular adhesionmolecule-1 (ICAM-1) soluble intercellular adhesionmolecule-1 (slCAM) and integrin beta2 (Refs 156ndash158and 180ndash182) These effects occur at both the local andsystemic levels183ndash185

HBO has protective effects over mitochondrialdysfunction It restores the electron flux through the IndashIV complex and reduces the formation of ROS anddamage of mitochondrial DNA By reducing theoxidative stress and concomitant oxidative damage itprevents apoptosis and damage created by the gluta-mate cascade and down-regulates the Nogo-A NG-Rand RhoA system preventing further damage to thenervous system186

Besides the favorable effects that hyperbaric oxygenexerts through oxygenation and protection against IRinjury it could have a very important protective effectthrough the antioxidant response that hyperbaric oxy-gen itself produces Thus the oxidative stress caused byHBO could indeed inhibit an oxidative damage187188This could be considered as the lsquohyperbaric oxygenparadoxrsquo in the IR injury

HBO also promotes the production of enzymaticantioxidants such as Mn CuZn superoxide dismutasegluthathione peroxidase and catalase189ndash193 There isalso an elevation of the most important non-enzymaticantioxidant system the glutathionecysteine system160This protective effect appears after the first hour ofexposure and can still be found 24ndash72 hours after thelast HBO treatment It is also well known that apreconditioning with hyperbaric oxygen can preventdamage caused by IR injury190

Among the key protective antioxidant effects we canfind increase production of anti-inflammatory cytokines(IL-10) reduced production of inducible neuronal nitricoxide synthase and neuronal nitric oxide synthasereduction in ROS production and up-regulation of keyantioxidant and anti-apoptotic factors such as BCL-2heme oxygenase-1 and heat-shock protein 70 and 72(Refs 194ndash205)



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The antioxidant response to HBO may be asimportant as the oxygenation effects of breathing100 oxygen at pressure especially in the acuteconditions that exhibit IR injury This dual processcould have an important protective effect in acuteconditions It appears that the energy crisis caused bythe reduction of the cellular ATP could also be part ofthe pathophysiology of chronic degenerative dis-eases206 The difference would be then in the magnitudeand speed of the decline of ATP In the acute and rapidfall of ATP necrosis and apoptosis results but in the mildchronic reduction of ATP cellular dysfunction and amore subtle cellular damage occur207

HBO can also exert its beneficial effect in peripheralnerve repair and regeneration by enhancing or prevent-ing the production of growth factors Yu et al found thatHBO reduced the gene expression of GDNF after 1 dayof injury in the HBO group as confirmed by immuno-histochemical staining208 Some of the growth factorssuch as basic fibroblast growth factor (bFGF) areineffective in stimulating healing under ischemic con-ditions even at high doses But when treated with HBOgrowth factors recover their function and become highlyeffective again (p005)209 HBO increases the produc-tion of bFGF vascular endothelial growth factor andTGF-b1 They have the ability to respond to hyperoxiadirectly which causes changes in cell signaling path-ways involved in cellular proliferation and growth factorproduction210 HBO has a synergistic effect with severalgrowth factors211 Another factor that is influenced byHBO is NT-3 It reduces the ischemia-induced down-regulation of NT-3 mRNA level 4 hours post-ischemiaand significantly increased cell survival 7 days afterreperfusion As mentioned previously NT-3 is animportant neurotrophic factor involved in peripheralnerve repair and regeneration212

HBO used for peripheral nerve injury started morethan 30 years ago213 Several studies have documentedthe effectiveness of HBO in models of acute anddelayed crush injury and regeneration Zhao214 reported114 patients treated microsurgically Fifty-four of themwere given HBO with good results in 89 of thecases (p005) compared with the control group(n560) He suggested the importance of promptcombined treatment

Zamboni et al215 used a rat sciatic nerve model(n536) The nerve was mobilized stripped of extrinsicblood supply transected and repaired in an epineuralfashion with microsurgical technique The animals werethen randomized into two groups with and withoutHBO The protocol used was 25 ATA90 minBID7 days Nerve recovery was assessed weekly for10 weeks [walking track analysis from which the nervefunction index (SFI) was calculated for each animal] SFIreached statistical significance at weeks 7ndash10 Theresults suggested functional recovery with the protocolused

Bradshaw et al216 tried a sciatic nerve crush model inrabbits (n530) Six different oxygen environments wereused and HBO was started 4 days after injury Theregenerative morphology of the nerves was evaluated

with transmission electron microscopy and light micro-scopy At week 7 the HBO groups resembled normaluncrushed nerves with nerve fibers uniformly distrib-uted throughout the section Myelination was alsosimilar to normal nerves Collagen and blood vesselswere more evident in the HBO treatments at lowerpressures than at higher pressures The nerves of thesurface oxygen and ambient or hyperbaric air groupswere edematous and contained disarrayed nerve fibers(Table 1) HBO can accelerate a peripheral nerverecovery from a crush injury

Santos et al conducted two studies In the first one217they used HBO in rats with transected peroneal nervesand entubulated with a Silastic channel The changesevaluated were acute edema functional recovery andhistology The protocol used was 25 ATA90 minBID7 days and then four times a day for other 7 daysThirteen weeks after the initial injury elicited muscleforce measurements demonstrated no significantimprovement from hyperbaric oxygen treatment ofinjured nerves There were no significant differencesbetween groups in histologic evaluation of nerve areamyelinated axon number myelinated axon area myelinthickness and blood vessel number In the secondstudy218 Santos et al also developed a reliable hypoxicnerve injury model They used 48 rats in a controlledand blinded trail of the injury model followed bytreatment with hyperbaric oxygen and the model wasevaluated with a functional model In the HBO group a12 improvement in function 5 days after treatmentwas demonstrated (p003) but no long-term orhistologic benefit was seen

Haapaniemi et al did several models for sciatic ratnerve regeneration219 axonal outgrowth in grafts insciatic rat nerves220 nerve regeneration in acellularnerve and muscle grafts in rats221 and early regenera-tion in nerve injury222 Nerve regeneration was eval-uated using a pinch-reflex test 3 4 and 5 days followingsurgery and with neurofilament staining at day 4 Theregeneration distance was significantly longer in theHBO group (33 ATA45 min0 4 and 8 hours post-operativelyTID) They concluded that HBO stimulatedaxonal outgrowth following a nerve crush lesion

In the axonal outgrowth grafts model (n540) thesciatic nerve was transected and a 10 mm long segmentfrom the opposite side was immediately sutured as anerve graft The HBO group (n517) was treated with32 ATA45 min repeated 4 and 8 hours post-operatively and the TID for 7 days The outgrowth was

Table 1 Excerpted from Bradshaw (216)

Group O2 () Pressure (kPa) (ATA) Edema Myelination

Control 21 101 (1) 0 3

I 21 101 (1) 2 1

II 100 101 (1) 3 1

III 21 202 (2) 1 1

IV 100 202 (2) 1 2

V 100 242 (24) 1 2

VI 100 303 (3) 0 2



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evaluated by immunohistochemical staining of neuro-filaments in the nerve grafts It was significantly longerin animals treated with HBO

In the acellular nerve and muscle grafts model bothgrafts were made acellular by freeze-thawing and thenused to bridge a 10 mm gap in the sciatic nerve on theleft and right sides respectively The HBO protocolused was 25 ATA90 minBID7 days Ten days aftersurgery the Schwann cell migration and invasion ofmacrophages were examined It was concluded thatHBO had no effect on regeneration process in acellularnerve grafts in contrast with fresh cellular nerve grafts

In the last report they compared two models a crushinjury model to a nerve transection and repair modelThe protocol used was 25 ATA90 minBID7 daysThe animals were evaluated with walking track analysisup to twice weekly The experiments were terminatedafter 90 days when the tetanic force was measured inthe tibial anterior and gastrocnemius muscles Nostatistically significant differences were found Theyconcluded that HBO was not effective in the restorationof gait or the muscular strength after 90 days in thenerve-injured rats

Tuma et al223 used a crush sciatic rat nerve modelthat was assessed by functional evaluation usingwalking track analysis The functional indexes did notdiffer from the untreated group They concluded thatHBO had no effect on functional recovery after nerveinjuries

Perez-Bolde et al224 used a rat sciatic nerveanastomosis model (n518) The functional evaluationwith electromyography was carried out before and afterneurorraphy and every 5 days up to 20 days when theanimals were killed and a histologic analysis wasperformed The HBO protocol was 20 ATA90 minBID7 days and then QD for 7 more days There was astatistical significance in the treatment group by day 10(p005) and by day 20 (p001) In the histologicanalysis there was conservation of the Schwann cell

architecture discrete demyelination and little edema inthe HBO group in contrast with the control group thathad marked reduction of Schwann cells large edemademyelination and loss of Schwann cell architectureThere was also moderate to severe infiltration of macro-phages and neutrophils within the formation of granu-lomas (Figure 2) They concluded that early HBO couldhelp reduce the peripheral nerve damage in crushinjuries

Eguiluz et al225 used a transection rat sciatic nervemodel with repair by microsurgical technique (n540)Nerve recovery was assessed by nerve conductionstudies 7 and 14 weeks after surgery Histopathologicanalysis was carried out after 7 and 14 weeks In theHBO groups there was a statistical significance atweek 7 (p003) in conduction velocities and ampli-tude and in the number of blood vessels The footankleangle showed better response at weeks 7 and 14Nevertheless the untreated group had a higher numberof axons and vessels at week 7 (p5003) whereas atweek 14 there was no significant difference Althoughthere were more axons and myelins it appeared to beless functional than in the HBO-treated group(Figure 3) They suggested that HBO could improvefunctional recovery in this model

CONCLUSIONSAcute peripheral nerve injury is one of the major causesfor severe and longstanding impairment of limb func-tion Up to now the surgical repair has been the goldenstandard of care Acute peripheral nerve lesion has avery important inflammatory component and is con-sidered as an IR injury Nevertheless nerve repair is notprimarily a mechanical problem and microsurgery is notthe only key to success There are many biologic aspectsthat contribute to nerve repair and regeneration and canimprove the functional results HBO has been proposedas one of the adjunctive treatments that could enhancethese processes

Figure 2 (A) Histology of Non-treated group There is characteristic of Wallerian degeneration of the nerve There is also reductionof the Schwann cells edema demyelination and loss of cytostructure There is moderate to severe infiltration of macrophages andneutrophils with formation of granuloma (B) Histology of HBO2 Group There is conservation of the Schwann cell architecture dis-crete demyelination and little edema There is no inclusion of neutrophils or macrophages and no granuloma is observed in thenerve fibers Although the fibers appear to be thinner probably due to remodelling



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Figure 3 (A) At week 7 there was a significant increase in latency (p003) in the non-treated group The sig-nificance was lost at week 14 (B) There was a statistical significance in the HBO2 group at week 7 in the num-ber of blood vessels (C) The amount of myelin was higher in the HBO2 group throughout the 14 weeks (D)Number of axons There is a statistical significant increase (708) in the number of axons at week 7 in theHBO2 The significance was lost at week 14 (E) Representative histological features from sciatic rat nerveNumerous middle size axons covered by myelin (black rings) and occasional small blood vessels from the scia-tic rat nerve at 7 weeks in the control group (F) Sciatic nerve at week 7 in the HBO2 group showing numerousaxons and small blood vessels (G) An apparent lower number of axons and blood vessels in the control groupat 14 weeks (H) Increased number of axons in the HBO2 group (magnification 6200 toluidin blue staining)



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HBO will promote survival of marginal tissue(penumbra) reduce the edema and improve the micro-circulation brake the vicious cycle of edemandashhypoxiandashedema enhance healing promote the up-regulation ofgrowth factors and improve neovascularization At thecellular level it will maintain the tissue levels of ATPrestore mitochondrial dysfunction inhibit prevent orreduce the IR injury and have significant antioxidantand anti-apoptotic effects

All of these mechanisms will enhance acute periph-eral nerve repair and regeneration Nevertheless aswith other treatments tried before the research successcannot be directly extrapolated into clinical benefitsThere have been non-favorable results when HBO hasbeen employed for this injury

It appears that the non-favorable results are encoun-tered in those research protocols that use pressureshigher than 20 ATA (202 kPa) The possibleexplanation is the importance of ATP and other highenergy compounds in the regeneration of peripheralnerve226ndash231 Almost 30 years ago Holbach et al232

proved that ATP production was reduced when treat-ment pressures were above 15 ATA This could explainwhy results are less favorable when pressures higherthan 20 ATA are used Actually Bradshaw et al des-cribed that the best results in the multiple groups usedwere found at lower pressures (20 ATA) This couldalso correlate with the lsquooxygen balancersquo If too highpressures are used for an IR injury the balance could tiltto the oxidative stress side and could generate too muchROS that could not be sufficiently compensated by theantioxidant capabilities at the time needed In this caseHBO could have even deleterious effects

Timing is also very important The treatment windowfor acute peripheral nerve lesions appears to be6 hours If HBO treatment is started after this windowit could also create negative effects on the tissue Thiscould also explain the contradictory results encounteredwith the use of HBO

We have found that if applied early HBO enhancesnerve repair regeneration and functional recovery asearly as 10 days after the lesion The effects aremaintained after 14 weeks which suggests that it isnot a short-term effect What was interesting was thatthe number of axons myelin blood vessels andfunctional tests were statistically significant at the7 week mark but lost significance at week 14 exceptfor the functional test that remained unchanged

It appears that there is a remodelling process at thesite of neurorraphy in the HBO-treated group which didnot occur in the non-treated group Apparently therewas a persistent effect of growth factors andor otherstimuli that did not end in functional recovery for thegroup that did not receive HBO

HBO could affect the pathophysiology of acuteperipheral nerve injury that seems to translate to abetter correlation between research studies and clinicaloutcome In conclusion HBO holds much promise asan effective therapy however more prospective rando-mized controlled studies are needed to establish the

utility of HBO in improving outcomes in peripheralnerve injury

ACKNOWLEDGEMENTI am in debt with Constanza Rosati for reviewing the article and for herpertinent comments regarding it

REFERENCES1 Cornwall R Radomisli TE Nerve injury in traumatic dislocation

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nerve trunks devoted to nerve fibers Brain 1949 72 428ndash4493 Artico M Cervoni L Nucci F et al Birthday of peripheral nervous

system surgery The contribution of Gabrielle Ferrara (1543ndash1627) Neurosurgery 1996 39 380ndash382

4 Berkow R ed The Merck Manual of Medical InformationWhitehouse Station NJ Merck amp Co 1997 p 330

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6 Colohan AR Pitts LH Rosegay H Injury to the peripheral nervesIn Feliciano DV Moore EE Mattox KL eds Trauma 3rd ednStamford CT Appleton amp Lange 1996 pp 853ndash862

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York Thieme Medical 19889 Grant GA Goodkin R Kliot M Evaluation and surgical manage-

ment of peripheral nerve problems Neurosurgery 1999 44 825ndash839

10 Schwartz SI Principles of Surgery 7th edn New York McGraw-Hill 1999 pp 2048ndash2053

11 Diao E Vannuyen T Techniques for primary nerve repair HandClin 2000 16 53ndash66

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14 Rafols FJ Orenstein HH Hand II Peripheral nerves and tendonstransfers Selected Readings Plast Surg 1999 8 1ndash40

15 Mira JC The biology of regeneration in peripheral nerves InTubiana R ed The Hand Vol 3 Philadelphia PA WB Saunders1988 pp 383ndash404

16 Brushart TM Gerber J Kessens P et al Contributions of pathwayand neuron to preferential motor reinnervation J Neurosci 19988 8674ndash8681

17 Drago J Kilpatrick TJ Koblar SA et al Growth factors Potentialtherapeutic applications in neurology J Neurol NeurosurgPsychiatry 1994 57 1445ndash1450

18 Lundborg G Rydevik B Effects of stretching the tibial nerve of therabbit A preliminary study of the intraneural circulation and thebarrier function of the perineurium J Bone Joint Surg Br 1973 55390ndash401

19 Birch R Raji AR Repair of median and ulnar nerves Primarysuture is best J Bone Joint Surg Br 1991 73 154ndash157

20 Fets Pa Woolston AM Fernando HB et al Inflammation andprimary demyelination induced by the intraspinal injection oflipopolysaccharide Brain 2005 128 1649ndash1666

21 Zelenka M Schafers M Sommer C Intraneural injection ofinterleukin-1beta and tumor necrosis factor-alpha into rat sciaticnerve at physiological doses induces signs of neuropathic painPain 2005 116 257ndash263

22 Gonzalez-Hernandez T Rustioni A Expression of three forms ofnitric oxide synthase in peripheral nerve regeneration J NeurosciRes 1999 55 198ndash207

23 Levy D Kubes P Zochodne DW Delayed peripheral nervedegeneration regeneration and pain in mice lacking induciblenitric oxide synthase J Neuropathol Exp Neurol 2001 60 411ndash421

24 Gupta R Lin YM Bui P et al Macrophage recruitment followsthe pattern of inducible nitric oxide synthase expression in a



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25 Keilhoff G Fansa H Wolf G Nitric oxide synthase an essentialfactor in peripheral nerve regeneration Cell Mol Biol (Noisy-le-grand) 2003 49 885ndash897

26 de la Hoz CL Oliviera AL Queiroz Lde S et al Walleriandegeneration in C57BL6J and AJ mice Differences in timecourse of neurofilament and myelin breakdown macrophagerecruitment and iNOS expression J Anat 2003 203 567ndash578

27 Conti G Rostami A Scarpini E et al Inducible nitric oxidesynthase (iNOS) in immune-mediated demyelination andWallerian degeneration of the rat peripheral nervous systemExp Neurol 2004 187 350ndash358

28 Yamamoto Y Henrich M Snipes RL et al Altered production ofnitric oxide and reactive oxygen species in rat nodose ganglionneurons during acute hypoxia Brain Res 2003 961 1ndash9

29 Sakaue G Shimakoa M Fukuoka T et al NF-kappa B decoysuppresses cytokine expression and thermal hyperalgesia in a ratneuropathic pain model Neuroreport 2001 12 2079ndash2084

30 Qi WN Yan ZQ Whang PG et al Gene and protein expressionsof nitric oxide synthases in ischemia-reperfused peripheral nerveof the rat Am J Physiol Cell Physiol 2001 281 C849ndashC856

31 Chen CW Lee ST Wu WT et al Signal transduction forinhibition of inducible nitric oxide synthase and cycloxygenase-2induction by capsaicin and related analogs in macrophages Br JPharmacol 2003 140 1077ndash1087

32 Siebert H Bruck W The role of cytokines and adhesionmolecules in axon degeneration after peripheral nerve axotomyA study in different knockout mice Brain Res 2003 960 152ndash156

33 Shin SJ Qi WN Cai Y et al Inhibition of inducible nitric oxidesynthase promotes recovery of motor function in rat after sciaticnerve ischemia and reperfusion J Hand Surg [Am] 2005 30826ndash835

34 Grunenfelder J Miniati DN Murata S et al Up-regulation of Bcl-2 through hyperbaric pressure transfection of TGF-beta1 amelio-rates ischemia-reperfusion injury in rat cardiac allografts J HeartLung Transplant 2002 21 244ndash250

35 Mizusawa I Abe S Kanno K et al Expression of cytokinesneurotrophins neurotrophin receptors and NOS mRNA in dorsalroot ganglion of a rat tourniquet model Leg Med (Tokyo) 2003 5(Suppl 1) S271ndashS274

36 Trump BF Croker BP Mergner WJ The role of energymetabolism ion and water shifts in the pathogenesis of cellinjury In Richter GW Scarpelli DG eds Cell MembranesBiological and Pathological Aspects Baltimore MD Willimas ampWilkins 1971 pp 84ndash128

37 Pentilla A Trump BF Extracellular acidosis protects Ehrlichascites tumor cells and rat renal cortex against anoxic injuryScience 1974 185 227ndash228

38 Nicholls DG Budd SL Mitochondria and neuronal survivalPhysiol Rev 2000 80 315ndash360

39 Ferencsik M Garay K Mihaly A et al Cobalt-complex ATPenhanced regeneration in the dorsal horn of the rat spinal cordExp Brain Res 1989 76 409ndash416

40 DrsquoAmbrosi N Murra B Cavaliere F et al Interaction betweenATP and nerve growth factor signalling in the survival andneuritic outgrowth from PC12 cells Neuroscience 2001 108527ndash534

41 DrsquoAmbrosi N Murra B Vacca F et al Pathways of survivalinduced by NGF and extracellular ATP after growth factordeprivation Prog Brain Res 2004 146 93ndash100

42 Wang T Hong G Wang S et al Effects of extracellular ATPon survival of sensory neurons in the dorsal root ganglia of ratsJ Tongji Med Univ 2001 21 44ndash47

43 Lundborg G A 25-year perspective of peripheral nerve surgeryEvolving neuroscientific concepts and clinical significanceJ Hand Surg [Am] 2000 25 391ndash414

44 Kurze T Microtechniques in neurological surgery ClinNeurosurg 1964 11 128ndash137

45 Smith JW Microsurgery Review of the literature anddiscussion of microtechniques Plast Reconstr Surg 1966 37227ndash245

46 Edshage S Peripheral nerve suture A technique for improvedintraneural topography Evaluation of some suture material ActaChir Scand Suppl 1964 331 1ndash104

47 Bertelli JA Mira JC Nerve repair using freezing and fibrin glueImmediate histologic improvement of axonal coaptationMicrosurgery 1993 14 135ndash140

48 Millesi H Terzis JK Nomenglature in peripheral nerve surgeryCommittee report of the International Society of reconstructivesurgery Clin Plast Surg 1984 11 3ndash8

49 Brunelli G Monini L Direct muscular neurotization J Hand Surg[Am] 1985 10 993ndash997

50 Carlstedt T Grane O Hallin RG et al Return of function afterspinal cord implantation of avulsed spinal nerve roots Lancet1995 346 1323ndash1325

51 Lundborg G Hansson HA Nerve regeneration through pre-formed pseudosynovial tubes A preliminary report of a newexperimental model of studying the regeneration and reorganiza-tion capacity of peripheral nerve tissue J Hand Surg [Am] 19805 35ndash38

52 Danielsen N Regeneration of the rat sciatic nerve in the siliconechamber model Restor Neurol Neurosci 1990 1 253ndash259

53 Archibald SJ Shefner J Krarup C et al Monkey median nerverepaired by nerve graft or collagen nerve guide tube J Neurosci1995 15 4109ndash4123

54 Lundborg G The tube concept in nerve repair Techn HandUpper Extrem Surg 1997 1 120ndash124

55 Lundborg G Rosen B Abrahamson SO et al Tubular repair ofthe median nerve in the human forearm Preliminary findingsJ Hand Surg [Br] 1994 19 273ndash276

56 Lundborg G Nerve repair Current concept and future prospec-tives Br J Hand Ther 1999 4 5ndash7

57 Carlstedt TP Hallin RG Hedstrom KG et al Functional recoveryin primates with brachial plexus injury after spinal cordimplantation of avulsed ventral roots J Neurol NeurosurgPsychiatr 1993 56 649ndash654

58 Weber RB Mackinnon SE Bridging the neural gap Clin PlastSurg 2005 32 605ndash616

59 Gulati AK Evaluation of acellular and cellular nerve grafts inrepair of rat peripheral nerve J Neurosurg 1988 69 117ndash123

60 Bailey SB Eichler ME Villadiego A et al The influence offibronectin and laminin during Schwann cell migration andperipheral nerve regeneration through silicon chambersJ Neurocytol 1993 22 176ndash184

61 Wang GY Hirai K Shimada H et al Behavior of axons Schwanncells and perineurial cells in nerve regeneration within trans-planted nerve grafts Effects of anti-laminin and anti-fibronectinantisera Brain Res 1992 583 216ndash226

62 Choi BH Han SG Kim SH et al Autologous fibrin glue inperipheral nerve regeneration in vivo Microsurgery 2005 25495ndash499

63 Kerns JM Danielsen N Holmquist B et al The influence ofpredegeneration on regeneration through peripheral nerve graftsin the rat Exp Neurol 1993 122 28ndash36

64 Maki Y Yoshizu T Tsubokawa N Selective regeneration ofmotor and sensory axons in an experimental peripheral nervemodel without endorgans Scand J Plast Reconstr Surg Hand Surg2005 39 257ndash260

65 Evans PJ Midha R Mackinnon SE The peripheral nerve allograftA comprehensive review of regeneration and neuroimmunologyProg Neurobiol 1994 43 187ndash233

66 Lassner F Schaller E Steinhoff G et al Cellular mechanisms ofrejection and regeneration in peripheral nerve allograftsTransplantation 1989 48 386ndash392

67 Gulati AK Cole GP Nerve graft immunogenicity as a factordetermining axonal regeneration in the rat J Neurosurg 1990 72114ndash122

68 Sondell M Lundborg G Kanje M Regeneration of the rat sciaticnerve into allografts made acellular through chemical extractionBrain Res 1998 795 44ndash54

69 Dubernard JM Owen E Herzberg G et al Human hand allograftReport on first 6 months Lancet 1999 353 1315ndash1320

70 Fawcett JW Keynes RJ Muscle basal lamina A new graft materialfor peripheral nerve repair J Neurosurg 1986 65 354ndash363



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71 Glasby MA Carrick MJ Hems TE Freeze-thawed skeletal muscleautografts used for the brachial plexus repair in the non-humanprimate J Hand Surg [Br] 1992 17 526ndash535

72 Hall SM The effect of inhibiting Schwann cell mitosis on the re-innervation of acellular autografts in the peripheral nervoussystem of the mouse Neuropathol Appl Neurobiol 1986 12401ndash414

73 Enver MK Hall SM Are Schwann cells essential for axonalregeneration into muscle autografts Neuropathol Appl Neurobiol1994 20 587ndash598

74 Alder JS Green CJ Nerve-muscle sandwich grafts The impor-tance of Schwann cells in peripheral nerve regeneration throughmuscle basal lamina conduits J Hand Surg [Br] 1995 20 423ndash428

75 Hems TE Glasby MA The limit of graft length in the experimentaluse of muscle grafts for nerve repair J Hand Surg [Br] 1993 18165ndash170

76 Foidart-Dessalle M Dubuisson A Lejeune A et al Sciatic nerveregeneration through venous or nervous grafts in the rat ExpNeurol 1997 148 236ndash246

77 Fields RD Le Beau JM Longo FM et al Nerve regenerationthrough artificial tubular implants Prog Neurobiol 1989 33 87ndash134

78 Willimas LR Varon S Modification of fibrin matrix formation insitu enhances nerve regeneration in silicone chambers J CompNeurol 1985 231 209ndash220

79 Lundborg G Kanje M Bioartificial nerve grafts A prototypeScand J Plast Reconstr Hand Surg 1996 30 105ndash110

80 Rosen JM Padilla JA Nguyen KD et al Artificial nerve graft usingcollagen as an extracellular matrix for nerve repair comparedwith sutured autograft in a rat model Ann Plast Surg 1990 25375ndash387

81 Phillips JB Bunting SC Hall SM et al Neural tissue engineeringA self-organizing collagen guidance conduit Tissue Eng 200511 1611ndash1617

82 Masaki T Matsumura K Saito F et al Association of dystroglycanand laminin-2 coexpression with myelinogenesis in peripheralnerves Med Electron Microsc 2003 36 221ndash239

83 Liesi P A laminin graft replaces neurorrhaphy in the restorativesurgery of the rat sciatic nerve Exp Neurol 1993 123 181ndash191

84 Davis GE Manthorpe M Willimas LR et al Characterization of alaminin-containing neurite promoting factor and a neurono-trophic factor for peripheral nerve and related sources Ann NYAcad Sci 1986 486 194ndash205

85 Hall S Axonal regeneration through acellular muscle grafts J Anat1997 190 57ndash71

86 Tong XJ Hirai K Shimada H et al Sciatic nerve regenerationnavigated by lamininndashfibronectin double coated biodegradablecollagen grafts in rats Brain Res 1994 663 155ndash162

87 Ohsumi H Hirata H Nagakura T et al Enhancement ofperineural repair and inhibition of nerve adhesion by viciousinjectable pure alginate sol Plast Reconstr Surg 2005 116 823ndash830

88 Cai J Peng X Nelson KD et al Permeable guidance channelscontaining microfilament scaffolds enhance axon growth andmaturation J Biomed Mater Res A 2005 75A 374ndash386

89 Xie F Li QF Zhao LS [Study on using a new biodegradableconduit to repairing ratrsquos peripheral nerve defect] ZhonghuaZheng Xing Wai Ke Za Zhi 2005 21 295ndash298

90 Cao W Cheng M Ao Q et al Physical mechanical anddegradation properties and Schwann cell affinity of cross-linkedchitosan films J Biomater Sci Polym Ed 2005 16 791ndash807

91 Rodrigues JM Luis AL Lobato JV et al Determination of theintracellular Ca2z concentration in the N1E-115 neuronal cellline in perspective of its use for peripheric nerve regenerationBiomed Mater Eng 2005 15 455ndash465

92 Chang CJ Hsu SH The effect of high outflow permeability inasymmetric poly(dl-lactic acid-co-glycolic acid) conduits forperipheral nerve regeneration Biomaterials 2006 27 1035ndash1042

93 Chen MH Chen PR Chen MH et al An in vivo study oftricalcium phosphate and glutaraldehyde crosslinking gelatinconduits in peripheral nerve repair J Biomed Mater Res B ApplBiomater 2006 77 89ndash97

94 Mersa B Agir H Aydin A et al Comparison of expandedpolytetrafluoroethylene (ePTFE) with autogenous vein as a nerveconduit in rat sciatic nerve defects Kulak Burun Bogaz Ihtis Derg2004 13 103ndash111

95 Viterbo F Trindade JC Hoshini K et al Latero-terminalneurorrhaphy without removal of the epineural sheathExperimental study in rats Rev Paul Med 1992 110 267ndash275

96 Adelson PD Bonaroti EA Thampson TP et al End-to-sideneurorrhaphies in a rodent model of peripheral nerve injury Apreliminary report of a novel technique J Neurosurg 2004 101(Suppl 1) 78ndash84

97 Viterbo F Trindade JC Hoshino K et al End-to-side neuror-rhaphy with removal of the epineurial sheath An experimentalstudy in rats Plast Reconstr Surg 1994 94 1038ndash1047

98 Noah EM Williams A Fortes W et al A new animal model toinvestigate axonal sprouting after end-to-side neurorrhaphyJ Reconstr Microsurg 1997 13 317ndash325

99 Al-Qattam MM Al-Thunyam A Variables affecting axonalregeneration following end-to-side neurorrhaphy Br J Plast Surg1998 51 238ndash242

100 Tarasidis G Watanabe O Mackinnon SE et al End-to-sideneurorrhaphy A long term study of neural regeneration in a ratmodel Otolaryngol Head Neck Surg 1998 119 337ndash341

101 Frey M Giovanoli P Girsch W Clinical application of end-to-side nerve coaptation for sensory or motor reinervation J HandSurg [Br] 1999 24 (Suppl 1) 9

102 Yin Q Kemp GJ Frostick SP Neurotrophins neurones andperipheral nerve regeneration J Hand Surg [Br] 1998 23 433ndash437

103 Fu SY Gordon T The cellular and molecular basis of peripheralnerve regeneration Mol Neurobiol 1997 14 67ndash116

104 Terzis JK Sun DD Thanos PK Historical and basic sciencereview Past present and future of nerve repair J ReconstrMicrosurg 1997 13 215ndash225

105 Hagiwara N Ikeda K Higashida H et al Induction of tumornecrosis factor-alpha in Schwann cells after gradual elongation ofrat sciatic nerve J Orthop Sci 2005 10 614ndash621

106 Hermann GE Holmes GM Rogers RC TNF(alpha) modulation ofvisceral and spinal sensory processing Curr Pharm Des 2005 111391ndash1409

107 Wieseler-Frank J Maier SF Watkins LR Immune-to-braincommunication dynamically modulates pain Physiological andpathological consequences Brain Behav Immun 2005 19 104ndash111

108 Haastert K Lipokatic E Fisher M et al Differentially promotedperipheral nerve regeneration by grafted Schwann cells over-expressing different FGF-2-isoforms Neurobiol Dis 2005 21138ndash153

109 Koprivisca V Cho KS Park JB et al EGFR activation mediatesinhibition of axon regeneration by myelin and chondroitin sulfateproteoglycans Science 2005 310 106ndash110

110 Hermann PM Nicol JJ Nagle GT et al Epidermal growth factor-dependent enhancement of axonal regeneration in the pond snailLymnaea stagnalis Role of phagocyte survival J Comp Neurol2005 492 383ndash400

111 Angelov DN Guntinas-Lichius O Wewetzer K et al Axonalbranching and recovery of coordinated muscle activity aftertransection of facial nerve in adult rats Adv Anat Embryol CellBiol 2005 180 1ndash130

112 Pei YY Duan SB Cai WJ et al [Effect of transforming growthfactor-beta 1 on the peripheral nerve regeneration of rats] ZhongNan Da Xue Xue Bao Yi Xue Ban 2005 30 447ndash451

113 Blondet B Carpentier G Lafdil F et al Pleiotrophin cellularlocalization in nerve regeneration after peripheral nerve injuryJ Histochem Cytochem 2005 53 971ndash977

114 Saika T Senba E Noguchi K et al Effect of nerve crush andtransection on mRNA levels for nerve growth factor receptor inthe rat facial motoneurons Brain Res Mol Brain Res 1991 9157ndash160

115 Sahenk Z Nagaraja HN McCracken BS et al NT-3 promotesnerve regeneration and sensory improvement in CMT1A mousemodels and in patients Neurology 2005 65 681ndash689



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118 Hansson HA Dahlin LB Danielsen N et al Evidence indicatingtrophic importance of IGF-1 in regenerating peripheral nervesActa Physiol Scand 1986 126 609ndash614

119 Rende M Muir D Ruoslahti E et al Immunolocalization ofciliary neuronotrophic factor in adult rat sciatic nerve Glia 19925 25ndash32

120 Meyer M Matsuoka I Wetmore C et al Enhanced synthesis ofbrain-derived neurotrophic factor in the lesioned peripheralnerve Different mechanisms are responsible for the regulationof BDNF and NGF mRNA J Cell Biol 1992 119 45ndash54

121 Iwase T Jung CG Bae H et al Glial cell line-derivedneurotrophic factor-induced signaling in Schwann cellsJ Neurochem 2005 94 1488ndash1499

122 Braun S Croizat B Lagrange MC et al Neurotrophins increasemotoneuronsrsquo ability to innervate skeletal muscle fibers in ratspinal cord-human muscle cocultures J Neurosci 1996 136 17ndash23

123 Marcol W Kotulska K Larysz-Brysz M et al Extracts obtainedfrom predegenerated nerves improve functional recovery aftersciatic nerve transection Microsurgery 2005 35 486ndash494

124 Yan Q Elliot J Snider WD Brain-derived neurotrophic factorrescues spinal motor neurons from axotomy-induced cell deathNature 1992 360 753ndash755

125 Henderson CE Camu W Mettling C et al Neurotrophinspromote motor neuron survival and are present in embryoniclimb bud Nature 1993 363 266ndash270

126 Gotz R Koster R Winkler C et al Neurotrophin-6 is a newmember of the nerve growth factor family Nature 1994 372266ndash269

127 Al-Bishri Dahlin L Sunzei B et al Systemic betamethasoneaccelerates functional recovery after a crush injury to rat sciaticnerve J Oral Maxillofac Surg 2005 63 973ndash977

128 Li HH Liu SQ Peng H et al Pyrroloquinoline quinone enhancesregeneration of transected sciatic nerve in rats Chin J traumatol2005 8 225ndash229

129 Galoyan AA Sarkissian JS Sulkhayan RM et al PRP-1 protectiveeffect against central and peripheral neurodegeneration followingn ischiadicus transection Neurochem Res 2005 30 487ndash505

130 Brenner MJ Machinnon SE Rickman SR et al FK506 and anti-CD40 ligand in peripheral nerve allotransplantation RestorNeurol Neurosci 2005 23 237ndash249

131 Balezina OP Gerasimenko NY Dugina TN et al Study ofneurotrophic activity of thrombin on the model of regeneratingmouse nerve Bull Exp Biol Med 2005 139 4ndash6

132 Voria I Hauser J Axis A et al Improved sciatic nerveregeneration by local thyroid hormone treatment in adult rat isaccompanied by increased expression of SCG10 Exp Neurol2005 197 258ndash267

133 Melcangi RC Cavaretta IT Ballabio M et al Peripheral nerves Atarget for the action of neuroactive steroids Brain Res Brain ResRev 2005 48 328ndash338

134 Mills CD Bitler JL Woolf CJ Role of the peripheral benzodia-zepine receptor in sensory neuron regeneration Mol CellNeurosci 2005 30 228ndash237

135 Isacsson A Kanje M Dahlin LB Induction of activatingtranscription factor 3 (ATF3) by peripheral nerve compressionScand J Plast Reconstr Surg Hand Surg 2005 39 65ndash72

136 Martini R Schachner M Immunoelectron microscopic localiza-tion of neural cell adhesion molecules (L1 N-CAM and myelin-associated glycoprotein) in regenerating adult mouse sciaticnerve J Cell Biol 1988 106 1735ndash1746

137 Zhang Y Bo X Schoepfer R et al Growth-associated proteinGAP-43 and L1 act synergistically to promote regenerativegrowth to Purkinje cell axons in vivo Proc Natl Acad Sci USA2005 102 14883ndash14888

138 Itoh S Fujimori KE Uyeda A et al Long term effects of muscle-derived protein with molecular mass of 77 kDa (MDP77) onnerve regeneration J Neurosci Res 2005 81 730ndash738

139 Gaudet AD Steeves JD Tetzlaff W et al Expression andfunctions of galectin-1 in sensory and motoneurons Curr DrugTargets 2005 6 419ndash425

140 Horie H Kadoya T Sango K et al Oxidized galectin-1 is anessential factor for peripheral nerve Curr Drug Targets 2005 6385ndash394

141 Kadoya T Horie H Structural and functional studies of galectin-1 A novel axonal regeneration-promoting activity for oxidizedgalectin-1 Curr Drug Targets 2005 6 375ndash383

142 Radtke C Akiyama Y Lankford KL et al Integration of engraftedSchwann cells into injured peripheral nerve Axonal associationand nodal formation on regenerated axons Neurosci Lett 2005387 85ndash89

143 Choi BH Zhu SJ Kim BY et al Transplantation of cultured bonemarrow stromal cells to improve peripheral nerve regenerationInt J Oral Maxillofac Surg 2005 34 537ndash542

144 Fox IK Schewtye KE Keune JD et al Schwann-cell injection ofcold-preserved nerve allografts Microsurgery 2005 25 502ndash507

145 Zhang PX He XJ Zhao FQ et al EGFP expression controlled byGFAP promoter in mesenchymal cells An efficient tool for gliallineage selection and transplantation Artif Cells Blood SubstitImmobil Biotechnol 2005 33 307ndash317

146 Perez-Bouza A Glaser T Brustle O ES cell-derived glialprecursors contribute to remyelination in acutely demyelinatedspinal cord lesions Brain Pathol 2005 15 208ndash216

147 Fukunaga S Sasaki S Fu T et al Experimental study of neuralrepair of the transected spinal cord using peripheral nerve graftJ Orthop Sci 2004 9 605ndash612

148 Zhang P He X Zhao F et al Bridging small-gap peripheral nervedefects using biodegradable chitin conduits with culturedSchwann and bone marrow stromal cells in rats J ReconstrMicrosurg 2005 21 565ndash572

149 Pluchino S Martino G The therapeutic use of stem cells formyelin repair in autoimmune demyelinating disorders J NeurolSci 2005 233 117ndash119

150 Zujovic V Luo D Baker VH et al The facial motor nucleustranscriptional program in response to peripheral nerve injuryidentifies HN1 as a regeneration-associated gene J Neurosci Res2005 82 581ndash589

151 La JL Jalai S Shami SA Morphological studies on crushed sciaticnerve of rabbits with electroacupuncture or diclofenac sodiumtreatment Am J Chin Med 2005 33 663ndash669

152 Guven M Gunay I Ozgunen K et al Effect of pulsed magneticfield on regenerating rat sciatic nerve An in vitro electrophysio-logic study Int J Neurosci 2005 115 882ndash892

153 Chang CJ Hsu SH Lin FT et al Low-intensity-ultrasound-accelerated nerve regeneration using cells-seeded poly(DL-lacticacid-co-glycolic acid) conduits An in vivo and in vitro studyJ Biomed Mater Res B Appl Biomater 2005 75 99ndash107

154 Feldmeier J ed Hyperbaric Oxygen 2003 Indications andResults Hyperbaric Oxygen Therapy Committee ReportKensington MD Undersea and Hyperbaric Medical Society2003

155 Buras J Basic mechanisms of hyperbaric oxygen in the treatmentof ischemia-reperfusion injury Int Anesthesiol Clin 2000 38 91ndash109

156 Buras JA Stahl GL Svoboda KH et al Hyperbaric oxygendownregulates ICAM-1 expression induced by hypoxia andhypoglycemia The role of NOS Am J Physiol Cell Physiol2000 278 C292ndashC302

157 Chen Q Banick PD Thom SR Functional inhibition of ratpolymorphonuclear leukocyte B2 integrins by hyperbaric oxygenis associated with impaired cGMP synthesis J Pharmacol ExpTher 1996 276 929ndash933

158 Thom SR Mendiguren I Hardy K et al Inhibition of humanneutrophil beta2-integrin-dependent adherence by hyperbaricO2 Am J Physiol 1997 272 C770ndashC777

159 Garcia-Covarrubias L Sanchez EC Terapia con oxigenacionhiperbarica conceptos basicos Gac Med Mex 2000 136 45ndash56

160 Haapanemi T Sirsjo A Nylander G et al Hyperbaricoxygen treatment attenuates glutathione depletion and improves



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metabolic restitution in postischemic skeletal muscle Free RadicRes 1995 23 91ndash101

161 Harris A Morgan JI Pecot M et al Regenerating motor neuronsexpress Nna1 a novel ATPGTP-binding protein related to zinccarboxypeptidases Mol Cell Neurosci 2000 16 578ndash596

162 Gysbers JW Guarnieri S Mariggio MA et al Extracellularguanosine 5rsquo triphosphate enhances nerve growth factor-inducedneurite outgrowth via increases in intracellular calciumNeuroscience 2000 96 817ndash824

163 Yuan LJ Ueng SW Lin SS et al Attenuation of apoptosis andenhancement of proteoglycan synthesis in rabbit cartilage defectsby hyperbaric oxygen treatment are related to the suppression ofnitric oxide production J Orthop Res 2004 22 1126ndash1134

164 Pedoto A Nandi J Yang ZJ et al Beneficial effect of hyperbaricoxygen pretreatment on lipopolysaccharide-induced shock inrats Clin Exp Pharmacol Physiol 2003 30 482ndash488

165 Sakoda M Ueno S Kihara K et al A potential role of hyperbaricoxygen exposure through intestinal nuclear factor-kappaB CritCare Med 2004 32 1722ndash1728

166 Weisz G Lavy A Adir Y et al Modification of in vivo and in vitroTNF-alpha IL-1 and IL-6 secretion by circulating monocytesduring hyperbaric oxygenation treatment in patients with perianalCrrohnrsquos disease J Clin Immunol 1997 17 154ndash159

167 Bitterman N Bitterman H Kinarty A et al Effect of a singleexposure to hyperbaric oxygenation on blood mononuclear cellsin human subjects Undersea Biomed Res 1993 20 197ndash204

168 Inamoto Y Okuno F Saito K et al Effect of hyperbaricoxygenation on macrophage function in mice BiochemBiophys Res Commun 1991 172 885ndash891

169 Yamashita M Yamashita M Hyperbaric oxygen treatmentattenuates cytokine induction after massive hemorrhage Am JPhysiol Endocrinol Metab 2000 278 E811ndashE816


171 Benson RM Minter LM Osborne BA et al Hyperbaric oxygeninhibits stimulus-induced proinflammatory cytokine synthesis byhuman blood-derived monocyte-macrophages Clin ExpImmunol 2003 134 57ndash62

172 Rocco M Antonelli M Letizia V et al Lipid peroxidationcirculating cytokines and endothelin-1 levels in healthy volun-teers undergoing hyperbaric oxygenation Minerva Anesthesiol2001 67 393ndash400

173 Granowitz EV Skulsky EJ Benson RM et al Exposure toincreased pressure or hyperbaric oxygen suppresses interferon-gamma secretion in whole blood cultures on healthy humansUnderesea Hyperb Med 2002 29 216ndash225

174 MacKenzie DA Sollinger HW Hullet DA Role of CD4z

regulatory T cells in hyperbaric oxygen-mediated immunenonresponsiveness Hum Immunol 2000 61 1320ndash1331


176 Yang ZJ Bosco G Montante A et al Hyperbaric O2 reducesintestinal ischemia-reperfusion-induced TNF-alpha productionand lung neutrophil sequestration Eur J Appl Physiol 2001 8596ndash103

177 Van den Blink B Van der Kleij AJ Verteeg HH et alImmunomodulatory effect of oxygen and pressure CompBiochem Physiol A Mol Integr Physiol 2002 132 193ndash197

178 Lin HC Wan FJ Wu CC et al Hyperbaric oxygen protectsagainst lipopolysaccharide-stimulated oxidative stress and mor-tality in rats Eur J Pharmacol 2005 508 249ndash254

179 Tsai HM Gao CJ Li WX et al Resuscitation from experimentalheatstroke by hyperbaric oxygen therapy Crit Care Med 200533 813ndash818

180 Angel MF Vander K Im MJ et al Effect of hyperbaric oxygenpreservation on xanthine oxidase activity in skin flaps Present atSymposium on Oxidative Stress and Infections 1992 BethesdaMD USA

181 Fildissis G Venetsanou K Myrianthefs P et al Whole bloodpro-inflammatory cytokines and adhesion molecules post-lipopolysaccharides exposure in hyperbaric conditions EurCytokine Netw 2004 15 217ndash221

182 Shinomiya N Suzuki S Hashimoto A et al Effect of hyperbaricoxygen on intercellular adhesion molecule-1 (ICAM-1) expres-sion in murine lung Aviat Space Environ Med 1998 69 1ndash7

183 Tjarnstrom J Wilkstrom T Bagge U et al Effects of hyperbaricoxygen treatment on neutrophil activation and pulmonarysequestration in intestinal ischemia-reperfusion in rats Eur SurgRes 1999 31 138ndash146

184 Chen HM Shyr MH Ueng SW et al Hyperbaric oxygen therapyattenuates pancreatic microcirculatory derangement and lungedema in an acute experimental pancreatitis model in ratsPancreas 1998 17 44ndash49

185 Chen MF Chen HM Ueng SW et al Hyperbaric oxygenpretreatment attenuates hepatic reperfusion injury Liver 199818 110ndash116

186 Zhou C Li Y Nanda A et al HBO suppresses NOGO-A NG-Ror RhoA expression in the cerebral cortex after global ischemiaBiochem Biophys Res Commun 2003 309 368ndash376

187 Nie H Xiong L Lao N et al Hyperbaric oxygen preconditioninginduces tolerance against spinal cord ischemia by upregulation ofantioxidant enzymes in rabbits J Cereb Blood Flow Metab 200626 666ndash674

188 Dong H Xiong L Zhu Z et al Preconditioning with hyperbaricoxygen and hyperoxia induces tolerance against spinal cordischemia in rabbits Anesthesiology 2002 96 907ndash912

189 Yasar M Yildiz S Mas R et al The effect of hyperbaric oxygentreatment on oxidative stress in experimental acute necrotizingpancreatitis Physiol Res 2003 52 111ndash116

190 Speit G Dennog C Radermacher P et al Genotoxicity ofhyperbaric oxygen Mutat Res 2002 512 111ndash119

191 Shaw FL Handy RD Bryson P et al A single exposure tohyperbaric oxygen does not cause oxidative stress in isolatedplatelets No effect on superoxide dismutase catalase or cellularATP Clin Biochem 2005 38 722ndash726

192 Wang W Xu R Lu R et al [A reappraisal of hyperbaricoxygenation effect and study on serum malondialdehyde andsuperoxide dismutase in patients with sudden deafness]Zhonghua Er Bi Yan Hou Ke Za Zhi 2000 35 356ndash358

193 Benedetti S Lamorgese M Piersantanelli M et al Oxidativestress and antioxidant status in patients undergoing prolongedexposure to hyperbaric oxygen Clin Biochem 2004 37 312ndash317

194 Kurata S Yamashita U Nakajima H Hyperbaric oxygenationreduces the cytostatic activity and transcription of nitric oxidesynthetase gene of mouse peritoneal macrophages BiochimBiophys Acta 1995 1263 35ndash38

195 Speit G Bonzheim I Genotoxic and protective effects ofhyperbaric oxygen in A549 lung cells Mutagenesis 2003 18545ndash548

196 Rothfuss A Speit G Investigations on the mechanisms ofhyperbaric oxygen (HBO)-induced adaptive protection againstoxidative stress Mutat Res 2002 508 157ndash165

197 Dennog C Gedik C Wood S et al Analysis of oxidative DNAdamage and HPRT mutations in humans after hyperbaric oxygentreatment Mutat Res 1999 43 351ndash359

198 Dennog C Radermacher P Barnett YA et al Antioxidant statusin humans after exposure to hyperbaric oxygen Mutat Res 1999428 83ndash89

199 Wada K Miyazawa T Nomura N et al Preferencial conditionsfor and possible mechanisms of induction of ischemic toleranceby repeated hyperbaric oxygenation in gerbil hippocampusNeurosurgery 2001 49 160ndash166

200 Rosenthal RE Silbergleit R Hof PR et al Hyperbaric oxygenreduces neuronal death and improves neurological outcome aftercanine cardiac arrest Stroke 2003 34 1311ndash1316

201 Shyu WC Lin SZ Saeki K et al Hyperbaric oxygen enhances theexpression of prion protein and heat shock protein 70 in a mouseneuroblastom cell line Cell Mol Neurobiol 2004 24 257ndash268

202 Wada K Miyasawa T Nomura N et al MnndashSOD and BCL-2expression after repeated hyperbaric oxygenation ActaNeurochir Suppl 2000 76 285ndash290

203 Rothfuss A Radermacher P Speit G Involvement of hemeoxygenase-1 (HO-1) in the adaptive protection of humanlymphocytes after hyperbaric oxygen (HBO) treatmentCarcinogenesis 2001 22 1979ndash1985



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204 Yu Y Matsumaya Y Yanase M et al Effects of hyperbaric oxygenon GDNF expression and apoptosis in spinal cord injuryNeuroreport 2004 15 2369ndash2373

205 Grunenfelder J Miniati DN Murata S et al Up-regulation ofBCL-2 through hyperbaric pressure transfection of TGF-beta1ameliorates ischemia-reperfusion injury in rat cardiac allograftsJ Heart Lung Transplant 2002 21 244ndash250

206 Jordan J Cena V Prehn JH Mitochondrial control of neurondeath its role in neurodegenerative disorders J Physiol Biochem2003 59 129ndash141

207 Tanaka S Takehashi M Iida S et al Mitochondrial impairmentinduced by poly (ADP-ribose) polymerase-1 activation in corticalneurons after oxygen and glucose deprivation J Neurochem2005 95 179ndash190


209 Wu L Pierce GF Ladin DA et al Effects of oxygen on woundresponses to growth factors Kaposirsquos FGF but not basic FGFstimulates repair in ischemic wounds Growth Factors 1995 1229ndash35

210 Kang TS Gorti GK Quan SY et al Effect of hyperbaric oxygen onthe growth factor profile of fibroblasts Arch Facial Plast Surg2004 6 31ndash35

211 Zhao LL Davidson JD Wee SC et al Effect of hyperbaric oxygenand growth factors on rabbit ear ischemic ulcers Arch Surg 1994129 1043ndash1049

212 Yang JT Chang CN Lee TH et al Hyperbaric oxygen treatmentdecreases post-ischemic neurotrophin-3 mRNA down-regulationin the rat hippocampus Neuroreport 2001 12 3589ndash3592

213 Yu WY Shim SS The effects of hyperbaric oxygen on nerveregeneration An experimental study in the femoral nerve ofrabbits Present at the 5th International Congress on HyperbaricMedicine 1973 Vancouver BC Canada

214 Zhao DW [Therapeutic effect of hyperbaric oxygen on recoveryof surgically repaired peripheral nerve injury] Zhonghua Wai KeZa Zhi 1991 29 118ndash120

215 Zamboni WA Brown RE Roth AC et al Functional evaluation ofperipheral-nerve repair and the effect of hyperbaric oxygenationJ Reconstr Microsurg 1995 11 27ndash29

216 Bradshaw PO Nelson AG Fanton AG et al Effect of hyperbaricoxygenation on peripheral nerve regeneration in adult malerabbits Undersea Hyperb Med 1996 23 107ndash113

217 Santos PM Zamboni WA Williams SL et al Hyperbaric oxygentreatment after rat peroneal nerve transection and entubulationOtolaryngol Head Neck Surg 1996 114 424ndash434

218 Santos PM A functional model system of a hypoxic nerve injuryand its evaluation Laryngoscope 2000 110 845ndash853

219 Haapaniemi T Nylander G Kanje M et al Hyperbaric oxygentreatment enhances regeneration of the rat sciatic nerveExp Neurol 1998 149 433ndash438

220 Haapaniemi T Nishiura Y Dahlin LB Functional evaluation afterrat sciatic nerve injury followed by hyperbaric oxygen treatmentJ Peripher Nerv Syst 2002 7 149ndash154

221 Haapaniemi T Nishiura Y Dahlin LB Effects of hyperbaricoxygen treatment on axonal outgrowth in sciatic nerve grafts inrats Scand J Plast Reconstr Surg Hand Surg 2001 35 7ndash11

222 Nishiura Y Haaapaniemi T Dahlin LB Hyperbaric oxygentreatment has different effects on nerve regeneration inacellular nerve and muscle grafts J Peripher Nerv Syst 2001 673ndash78

223 Tuma P Jr Dias MD Arrunategui G et al Effect ofhyperbaric oxygen on the regeneration of experimental crushinjuries on nerves Rev Hosp Clin Fac Med Sao Paulo 1999 5481ndash84

224 Perez-Bolde A Mendoza J Sanchez EC Hyperbaric oxygentherapy in the peripheral nerve regeneration Undersea HyperbMed (Suppl) 1999 26 39ndash40

225 Eguiluz R Sanchez EC Venegas A et al Effects of hyperbaricoxygen on peripheral nerves Plast Reconst Surg 2006 118 350ndash357

226 Chada SR Hollenbeck PJ Hollenbeck PJ Mitochondrial move-ment and positioning in axons The role of growth factorsignaling J Exp Biol 2003 206 1985ndash1992

227 Austin L Watterson JG Hearn MT Regenerating neuronsChanges in protein phosphorylation Mol Neurobiol 1992 687ndash93

228 Van Hooff CO De Graan PN Oestreicher AB et al B-50phosphorylation and polyphosphoinositide metabolism in nervegrowth cone membranes J Neurosci 1988 8 1789ndash1795

229 Arteaga MF Gutierrez R Avila J et al Regenerationinfluences expression of the Naz Kz-atpase subunit isoformsin the rat peripheral nervous system Neuroscience 2004 129691ndash702

230 Gunther A Manaenko A Franke H et al Hyperbaric andnormobaric reoxygenation of hypoxic rat brain slices impact onpurine nucleotides and cell viability Neurochem Int 2004 451125ndash1132

231 Gunther A Manaenko A Franke H et al Early biochemical andhistological changes during hyperbaric or normobaric reoxygena-tion after in vitro ischaemia in primary corticoencephalic cellcultures of rats Brain Res 2002 946 130ndash138

232 Holbach KH Caroli A Wassmann H Cerebral energy metabo-lism in patients with brain lesions at normo- and hyperbaricoxygen pressures J Neurol 1977 217 17ndash30



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In the fourth-degree injury the nerve fasciculi aredamaged but nerve sheath continuity is preserved59 Itresults in a large area of scar at the site of nerve injuryand precludes any axon from advancing distal to thelevel of nerve injury Electrodiagnostic studies revealthat denervation changes the affected muscles and noMUPs are present No improvement of function is notedand the patient requires surgery to restore neuralcontinuity thus permitting axonal regeneration andmotor and sensory reinnervation5

In the fifth-degree injuries there is a complete tran-section of the nerve They correspond to Seddonrsquosclassification of a neurotmesis lesion It requires surgeryto restore neural continuity Electrodiagnostic studiesare the same as in the fourth-degree injury59Mackinnon introduced a sixth-degree injury to describea complex peripheral nerve injury It is a mixed nerveinjury that combines the other degrees of injury9

PATHOPHYSIOLOGYThe physiologic response is different depending on thetype of injury If the axon is spared as in the first-degreeinjury conduction is interrupted due to demyelinationbut is reinstated whenever the aggravating stimulus isremoved and the myelin layers are restored If the axonor more is transected causing a second- to fifth-degreeinjury the response has two main phases degenerationand regeneration and takes substantially longer11Pathologically three phases were identifiable phase 1(0ndash3 hours) minimal pathologic changes and minimaledema phase 2 (7ndash14 days) prominent fiber degenera-tion and endoneurial edema and phase 3 (28ndash42 days)abundant small regenerating fiber clusters and minimaledema12

The first phase of axon injury degeneration was firstdescribed by Waller in 1850 (Ref 13) Following injurychanges occur in the cell body axon and the Schwanncell Both distally and proximally the axon begins todisintegrate and undergoes apoptosis Local Schwanncells and macrophages clean up the apoptotic debriscreating long clean endoneurial tubes Once the debrishas been removed Schwann cells proliferate andorganize themselves into columns that lie within theendoneurial tubes creating the bands of Bunger81114

After injury there is a great increase in the productionof mRNA and proteins15 These products are transporteddown the axon providing the material and energyfor nerve elongation to the distal tip The severedaxons begin to sprout and contain an expanded regionknown as the growth cone This is the site of axonelongation and sends out many small processes thatseek specific markers which influence the axon in itsmovements to preferentially select neural tissue andeven exhibit a preference for endoneurial tubes with thesame function16

The axonrsquos response is regulated by neurotrophicfactors that direct and attract the axon17 Neurotrophicfactors induce maturation and elongation of the axon14They are released by macrophages Schwann cells andother supporting cells

If the nerve is too far away the axons are not stronglyattracted to the distal end and eventually stop advan-cing causing aberrant innervation at the end organlevel1417

Large gaps greater than 15 mm cannot be crossedreliably by axons This is usually because proliferatingSchwann cells or fibroblasts grow between the severenerve ends and form a physical blockage18 If the axonsprouts stop proliferating and take residence in a dif-ferent tissue they will form a neuroma19

Neuroinflammation in primary demyelination andWallerian degeneration is an ischemia-reperfusion(IR) injury and is mediated by cytokines and otherimmune mediators (Figure 1)121320ndash36 IR injury con-tributes to both axonal degeneration and regeneration13Reperfusion by oxidative injury worsened nerve func-tion and aggravated fiber degeneration but in the longertime frame permitted fiber regeneration to occur12

During peripheral nerve injury hypoxia createsseveral cellular shock stages that could be reversibleor irreversible The reversibility depends on the cellscapability to maintain adenosine-5rsquo-triphosphate (ATP)production3738 Once ATP production is stopped thecell can no longer maintain the homeostatic functionsThis produces cytotoxic edema and release of calciumby the mitochondria39

ATP has many important functions on peripheralnerve repair and regeneration It is important tomaintain cellular functions and is also the energy sourcefor axoplasmic transport It is indispensable for thetransport of nerve growth factors (NGF)40 There is apotential interplay between ATP and NGF in thesignaling pathways triggered on their target cells41ATP has neuritrogenic and trophic effects which arecomparable to those sustained by NGF and involveseveral overlapping pathways42 ATP exerts a protectiveeffect on the neurons which is valuable for nerveregeneration after nerve injury42

NERVE REPAIRThe surgical reconstruction of peripheral nerve damageis crucial Although the surgical procedure may beoptimal and an excellent rehabilitation program isconducted the end results still remain unpredictableand complete functional recovery is still rare43 A nervelesion is different from other tissue injury because itrequires more than only local processes Transection ofaxons has implications for the whole length of theneuron and the repair process involves outgrowth ofneurites over very long distances In addition a nerveinjury in contrast to most other injuries of the body hasimmediate functional consequences for the brain interms of rapid functional reorganization in braincortex43

From the biologic point of view the physiologic resultfollowing nerve injury and repair is dependent onfactors such as the extent of nerve cell survival after theinjury the rate and quality of axonal outgrowth theorientation and specificity in growth of regenerationaxons the survival and state of end organs and cortical



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Control 21 101 (1) 0 3

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Peripheral Nerve Repair and Regeneration

Documents

Transcript of Peripheral Nerve Repair and Regeneration