Update on Biologics in Update on Biologics in Orthopedic Orthopedic

SportsmedicineSportsmedicineCells and Growth Cells and Growth

FactorsFactorsWilliam F Bennett MDWilliam F Bennett MD

Injured Tissue-The Basics of Injured Tissue-The Basics of HealingHealing

Requires Requires CellsCells and and Growth FactorsGrowth Factors Tissue repair relies on vascularity and cellular Tissue repair relies on vascularity and cellular

migrationmigration Blood escapes, hematomaBlood escapes, hematoma Platelets, pluripotential stem cells form scaffold Platelets, pluripotential stem cells form scaffold

for neocellular proliferationfor neocellular proliferation Cells respond to Growth Factors(Bioactive Cells respond to Growth Factors(Bioactive

agents)agents) Some cells respond different to growth factors Some cells respond different to growth factors

based upon tissuebased upon tissue

Growth Factors/Bioactive Growth Factors/Bioactive AgentsAgents

At the time of injury released, Gfs bind to At the time of injury released, Gfs bind to receptors and effect cellular function.receptors and effect cellular function.

Part of inflammatory response.Part of inflammatory response. ProteinsProteins Anabolic/catabolicAnabolic/catabolic Cytokines-extracellular proteinsCytokines-extracellular proteins

• Effect cell to cell mediationEffect cell to cell mediation Examples- Interferon/interleukin/tumor necrosis Examples- Interferon/interleukin/tumor necrosis

factorfactor

Growth FactorsGrowth Factors

Transforming Growth factor-Transforming Growth factor-beta(TGFB)-Largest groupbeta(TGFB)-Largest group

• Over 100 membersOver 100 members• Anabolic effect on all components ofAnabolic effect on all components of

Musculoskeletal tissueMusculoskeletal tissue

Common Types of TGF-BetaCommon Types of TGF-Beta

Bone Morphogenic proteins-BMPBone Morphogenic proteins-BMP’’ss• Osteoprogenitor derived cells-promote bone Osteoprogenitor derived cells-promote bone

growthgrowth Platelet Derived Growth Factor-PDGFPlatelet Derived Growth Factor-PDGF

• From platelets and stimulates angiogenesis, From platelets and stimulates angiogenesis, chemotactic influence and mitogenicchemotactic influence and mitogenic

Insulinlike Growth Factor-IGF-1Insulinlike Growth Factor-IGF-1• From variable cells, broad anabolic effectFrom variable cells, broad anabolic effect

Fibroblast Growth factor-bFGFFibroblast Growth factor-bFGF• Early differentiation of cells and tissue and in Early differentiation of cells and tissue and in

repair processrepair process

Common Types of TGF-BetaCommon Types of TGF-Betacontcont’’dd

Epidermal Derived Growth Factor-Epidermal Derived Growth Factor-EGFEGF• Proliferates ectoderm and mesodermProliferates ectoderm and mesoderm

Growth and differentiation Factor-Growth and differentiation Factor-GDF-5GDF-5• Chondrocyte, fibroblast and Chondrocyte, fibroblast and

mesenchymal cell expansionmesenchymal cell expansion

Bone HealingBone Healing

Two clinically available Two clinically available BMPBMP’’ss-stimulates bone growth-stimulates bone growth• rhBMP2-Recombinant BMP- rhBMP2-Recombinant BMP- (Infuse, Medtronic Sofamor (Infuse, Medtronic Sofamor

Danek, Minneapolis, Mn.)Danek, Minneapolis, Mn.)• BMP 7-BMP 7-(osteogenic protein-1- OP1)(osteogenic protein-1- OP1)

Stryker, Biotech, Hopkinton, Ma,Stryker, Biotech, Hopkinton, Ma, LMP1LMP1-Lyophilized Mineral protein-Lyophilized Mineral protein

• Stimulates BMPStimulates BMP PDGF and Platelet Rich Plasma PDGF and Platelet Rich Plasma may interfere with bone may interfere with bone

healinghealing BMPs BMPs help reduce non-union rate, spinal fusion rate and help reduce non-union rate, spinal fusion rate and

possibly open wedge osteotomy non-healingpossibly open wedge osteotomy non-healing

Bone To Tendon HealingBone To Tendon Healing

BMP2 and OP1 BMP2 and OP1 have been shown to have been shown to aid in the tendon to bone healingaid in the tendon to bone healing

Although the exact mechanism for Although the exact mechanism for this repair process is not well knownthis repair process is not well known

Tendon To TendonTendon To Tendon

Mechanism not well definedMechanism not well defined GDF5 GDF5 may play a rolemay play a role IGF1 and PDGF2IGF1 and PDGF2

• Increased collagen synthesisIncreased collagen synthesis These factors can be found in These factors can be found in

augmentation tissues like porcine augmentation tissues like porcine submucosa, bovine, equine collagen and submucosa, bovine, equine collagen and human allograft dermishuman allograft dermis

CascadeCascade- shows to repair tissue- platelet - shows to repair tissue- platelet rich plasmarich plasma !!!!!!!!!!!!!!! !!!!!!!!!!!!!!!

Ligament HealingLigament Healing

Cell Proliferation, Type 1 CollagenCell Proliferation, Type 1 Collagen• and proteoglycan synthesis are and proteoglycan synthesis are

stimulated stimulated by bFDF, PDGF and bTGFby bFDF, PDGF and bTGF

Method of delivery will be a gene-Method of delivery will be a gene-enhanced delivery system via enhanced delivery system via fibroblast cells transduced by fibroblast cells transduced by plasmid or virus carrying these plasmid or virus carrying these growth factorsgrowth factors

Meniscus HealingMeniscus Healing Meniscal tears heal better when ACL Meniscal tears heal better when ACL

reconstruction is done at the same time.reconstruction is done at the same time. Suggests that something in the blood Suggests that something in the blood

augments healingaugments healing Arnozcky has shown a fibrin clot to help Arnozcky has shown a fibrin clot to help

healing.healing. Platelet Rich Fibrin Matrix(PRFM)Platelet Rich Fibrin Matrix(PRFM)

• Cascade- ultracentrifuge of bloodCascade- ultracentrifuge of blood• Platelt rich ultracentrifugate is further Platelt rich ultracentrifugate is further

centrifuged down to a volume-stable suturable centrifuged down to a volume-stable suturable fibrin matrixfibrin matrix

Articular CartilageArticular CartilageHealing is not regenerationHealing is not regeneration

Articular cartilage is Hyaline cartilageArticular cartilage is Hyaline cartilage• Type 2 collagenType 2 collagen

Heals to injury with fibrocartilageHeals to injury with fibrocartilage• Type 1 collagenType 1 collagen• No vascular supplyNo vascular supply• No nervesNo nerves• More of a scar tissue than normal tissueMore of a scar tissue than normal tissue

Articular Cartilage RepairArticular Cartilage Repair

Fissuring- chondroplasty, smooths Fissuring- chondroplasty, smooths edges only, no healingedges only, no healing

Osteochondral defects- microfracture Osteochondral defects- microfracture technique or marrow stimulation technique or marrow stimulation techniques-forms fibrocartilagetechniques-forms fibrocartilage

Cartilage-growth factorsCartilage-growth factors• Bmp2/1IGF/bTGFBmp2/1IGF/bTGF• Add these to cell colonies, like genzyme Add these to cell colonies, like genzyme

cell cultures- get better hyaline cartilagecell cultures- get better hyaline cartilage

Cartilage Systems-U.S.Cartilage Systems-U.S.

Lavage and debridementLavage and debridement ChondroplastyChondroplasty MicrofractureMicrofracture OatsOats Polymer bone plugsPolymer bone plugs Osteochondral allograftsOsteochondral allografts Cartilage cultures- Genzyme onlyCartilage cultures- Genzyme only

• Cambridge MaCambridge Ma

Cartilage CulturesCartilage Cultures

Carticel- Genzyme-using Carticel- Genzyme-using chondrocytes, cartilage cells as chondrocytes, cartilage cells as opposed to stem cells.opposed to stem cells.• Bx, 4-6 weeks later can replant with Bx, 4-6 weeks later can replant with

cultured cells, use periosteal patch, open cultured cells, use periosteal patch, open surgery, collagen membrane 2surgery, collagen membrane 2ndnd generation……using presently.generation……using presently.

• Next gen Carticel, MACI-matrix Next gen Carticel, MACI-matrix impregnated with cells, no periosteal impregnated with cells, no periosteal patchpatch

Other source of Cells than Other source of Cells than chondrocyteschondrocytes

Stem CellsStem Cells Both an evolution and a revolution in Both an evolution and a revolution in

modern biomedicine.modern biomedicine. Concept is rather than introduce organ Concept is rather than introduce organ

transplant, one would implant certain transplant, one would implant certain population of cells to allow regenerationpopulation of cells to allow regeneration

Bone marrow transplantation is Bone marrow transplantation is intermediate between organ and stem cell intermediate between organ and stem cell transplant.transplant.

Present ApplicationsPresent Applications

Bone Marrow transplant- for radiation Bone Marrow transplant- for radiation loss of blood cells and their loss of blood cells and their progenitor lines.progenitor lines.

Stem cell skin grafts for burn victims.Stem cell skin grafts for burn victims. Corneal stem cell implants.Corneal stem cell implants. Pancreatic islet cell implantation.Pancreatic islet cell implantation.

Applications in genetically Applications in genetically defective cell linesdefective cell lines

Genetically corrected stem cells used Genetically corrected stem cells used to treat;to treat;• Muscular dystrophyMuscular dystrophy• Other disease processesOther disease processes• Future will be in musculoskeletal areas Future will be in musculoskeletal areas

as well.as well.

Stem Cell TypesStem Cell TypesMyth and FactMyth and Fact

Adult stem cells identified from brain to Adult stem cells identified from brain to muscle.muscle.

Fetal Stem cells- aborted fetuses or Fetal Stem cells- aborted fetuses or umbilical chordumbilical chord

Embryonic stem cells-Embryonic stem cells-• Discarded from in vitro fertilizationDiscarded from in vitro fertilization• Somatic Nuclear Transfer- Somatic Nuclear Transfer- a nucleus from a a nucleus from a

normal body cell is placed into a fertilized egg normal body cell is placed into a fertilized egg with its nucleus removed.with its nucleus removed.

The fertilized egg has the effect of The fertilized egg has the effect of ““resettingresetting”” the the nucleus to a primordial state.nucleus to a primordial state.

No ethical considerations with fetuses here!No ethical considerations with fetuses here!

Embryonic-Embryonic-• Ubiquitous component Ubiquitous component

of the embryo.of the embryo.• Defined by position in Defined by position in

the embryothe embryo• Divide in culture Divide in culture

without changing without changing charcteristics.charcteristics.

• Single cell can give rise Single cell can give rise to a colony of cells.to a colony of cells.

Adult-

-rare, difficult to identify, unknown origin, partially understood function and life history

-defined by complex list of features.

-can not divide indefinitely.

Embryonic versus AdultEmbryonic versus Adult

Stem CellsStem Cells

Maintain undifferentiated phenotype Maintain undifferentiated phenotype until exposed to appropriate signals.until exposed to appropriate signals.

With signals can differentiate into With signals can differentiate into specialized cells that have structure specialized cells that have structure and functionand function

Mesenchymal Stem cells are of this Mesenchymal Stem cells are of this type-MScs- bone marrow.type-MScs- bone marrow.

Mesenchymal is from a layer in the Mesenchymal is from a layer in the developing embryo.developing embryo.

What we know and do not knowWhat we know and do not know

Know some signalsKnow some signals DonDon’’t know all intermediate stepst know all intermediate steps DonDon’’t know how exactly how one cell t know how exactly how one cell

changes to another.changes to another. DonDon’’t understand the microenvironment t understand the microenvironment

completely.completely. Adult and MSC have limited differentiation Adult and MSC have limited differentiation

potential compared to embryonic stem potential compared to embryonic stem cells and limited number of replication cells and limited number of replication cycles.cycles.

Stem Cell ExhaustionStem Cell Exhaustion

Stem cells may be exhaustedStem cells may be exhausted Has been shown to happen in Has been shown to happen in

degenerative conditions, especially degenerative conditions, especially osteoarthritis.osteoarthritis.

FutureFuture

Over next 5-10 years there will be Over next 5-10 years there will be major commercial development in major commercial development in the area of stem cell enterprises.the area of stem cell enterprises.