PhotoBioModulation (PBM) and diabetic wounds

There is still no ”cure” for diabetes and PBM is not a cure but certainly a very promising treatment modality to control the side effects of diabetes. One of these is the poor wound healing capacity of diabetic tissues and the majority of PBM studies has been focusing on this topic. So is there any evidence? A rodent study by al-Watban (1) has the challenging title Laser therapy converts diabetic wound healing to normal healing. The author has previously identified the red laser light around 633 nm as the most effective wavelength (2) and in this more recent study, the conclusion is as follows:

In this induced-diabetes model, wound and burn healing were improved by 40.3% and 45%, respectively, in 633-nm laser dosimetry experiments, and diabetic wound and burn healing was accelerated by phototherapy. This indicates that the healing rate was normalized in the phototherapy-treated diabetic rats. In view of these interesting findings, 633-nm laser therapy given three times per week at 4.71 J/cm2 per dose for diabetic burns, and three times per week at 2.35 J/cm2 per dose for diabetic wound healing are recommended as actual doses for human clinical trials, especially after major surgery in those with impaired healing, such as diabetics and the elderly.

The results of this study suggests that wounds in diabetic patients can heal in a similar fashion to those in healthy individuals. And it is only too well known that wound healing is one of the major problems in diabetic patients. Adding PBM could then be a very valuable adjunctive method for this large and fast growing group of patients. The al-Watban study has indeed an animal model and wounds in rodents and humans have different healing mechanisms. This puts focus on a problem in this field: In spite of more than 500 studies on PBM and wound healing, the vast majority of these are based upon in vitro or animal models, while very few are clinical. And in addition to that, several of the clinical studies are of questionable quality (3).

So what about the clinical side? Two studies by Obradović (4,5) conclude that the wound healing in patients treated for periodontal disease had a more favorable outcome when PBM was used as an adjunctive method. The diabetic foot ulcer is a common complication, difficult to treat and not infrequently leading to amputations. A clinical study by Feitosa (6) reports: Sixteen type II diabetic patients, ulcer carriers in the lower limbs, participated in the research from which eight were in the control group and eight were submitted to the low-level laser therapy with a pulsed wave form, visible ray, wave length of 632.8 nm, 30 mW peak power. The application time was of 80 (4J/cm2) seconds. The application was punctual without contact (approximately 1mm of distance), the pen being held in a perpendicular position related to the wound, in equidistant points. There were 12 appointments, of which three were done weekly in alternated days. Photograph records and an application of the brief inventory of pain were done before and after 30 days of follow-up. There was a significant decrease in the size of the wound when compared to the control group (p<0.05). The pain was also reported as having an intense improvement in the treated group. The low-level laser treatment seems to be an efficient method, viable, painless and of low costs concerning the tissue repair ulcers in a diabetic foot.

In a literature review Tchanque-Fossuo (7) concludes: LLLT is an emerging and promising treatment modality to current alternatives that are costly and have shown limited success. Based upon the published evidence, we envision additional research may allow for

stronger recommendation with LLLT for treatment of diabetic foot ulcers. In another review of the literature, Beckmann (8) writes: The majority of clinical studies show a potential benefit of LLLT in wound healing of diabetic ulcers. But there are a lot of aspects in these studies limiting final evidence about the actual output of this kind of treatment method. In summary, all studies give enough evidence to continue research on laser therapy for diabetic ulcers, but clinical trials using human models do not provide sufficient evidence to establish the usefulness of LLLT as an effective tool in wound care regimes at present. Further well designed research trials are required to determine the true value of LLLT in routine wound care.

Both reviewers point to the same fact: The number of clinical studies is low and the parameters used are heterogeneous, making a safe conclusion difficult. So indeed, more research is called for. As pointed out by Tchanque-Fossuo (7): Diabetic foot ulcers (DFU) represent a significant complication of diabetes mellitus (DM). DFU affect one in four patients with DM and treatments of DFU are limited and challenging. The management of DFU remains a significant healthcare and socioeconomic burden ($245 billion). There is a wide range of advanced therapies for DFU, but these are costly and have demonstrated only minimal efficacy in limited published studies. In the light of this information, PBM apparently has a very promising potential of lowering not only patient suffering but also health care costs.

So, the literature is still inconclusive, but sometimes seeing is believing. The photo below shows a diabetic foot treated with PBM as an adjuncts treatment modality.

Courtesy of Dr. Kazemi-Khoo (9).

Which are the mechanisms behind the effect of PBM in the healing of diabetic wounds? Here is initially a brief list of observations:

Schindl [10] presented already 15 years ago a study aimed at evaluating the possible protective effect of LPT against high glucose-induced delay in proliferation of human endothelial cells. Human umbilical vein endothelial cells were cultured with either standard or elevated concentrations of glucose and were irradiated with a 670 nm diode laser. Irradiation was performed every other day for one week. Cell proliferation was evaluated on

days two, four and seven. The results demonstrated a dose-dependent protective effect of laser irradiation on high glucose-induced reduction of cell counts on day seven. These data provide further evidence of the beneficial effects of LPT on patients with diabetic microangiopathy.

Houreld (11) showed that wounded diabetic WS1 cells irradiated with 5 J/cm2

showed increased cellular repair when irradiated with an adequate amount of time between irradiations, allowing time for cellular response mechanisms to take effect. Therefore, the irradiation interval was shown to play an important role in wound healing in vitro and should be taken into account. Ideal results were obtained when irradiated 30 minutes and 72 hrs post injury. Thus, the irradiation protocol is important.

Another study by Houreld (12) aimed at determining the effect on cellular proliferation, migration, and cytokine interleukin-6 expression in diabetic and diabetic wounded fibroblast cells (WS1) post-laser irradiation. Diabetic and diabetic wounded WS1 cells were irradiated at 632.8 nm (23 mW) with 5 J/cm2 or 16 J/cm2. IL-6 level, cellular proliferation (neutral red assay), and morphology were then determined. Diabetic cells irradiated with 5 J/cm2 showed no significant changes, while diabetic wounded cells showed an increase in IL-6 level, proliferation, and migration. On the other hand, diabetic and diabetic wounded cells irradiated with 16 cm2 showed a significant decrease in proliferation and evidence of cellular damage, and wounded cells showed no migration. This study showed that phototherapy at the correct fluence level stimulates IL-6 expression, proliferation, and cellular migration in diabetic wounded cells. The study underlines the importance of balancing between stimulation and inhibition.

Wound healing was assessed by Byrnes (13) according to wound closure and histological characteristics of healing. Optimal treatment parameters were then used to treat type 2 diabetic Sand Rats, while a diabetic control group received no irradiation. In order to elucidate the mechanism behind an improvement in wound healing, the expression of basic fibroblast growth factor (bFGF) was assessed. Significant improvement in wound healing histology and wound closure were found following treatment with 4 J/cm2 (16 mW, 250-sec treatments for four consecutive days). The 4 J/cm2 dosage significantly improved histology and closure of wounds in the diabetic group in comparison to the non-irradiated diabetic group. Quantitative analysis of bFGF expression at 36 h post-injury revealed a threefold increase in the diabetic and non-diabetic Sand Rats after LPT.

In a study by Maiya (14) diabetes was induced in rats by streptozotocin 30 days after its injection. Two sets of skin samples were extracted under sterile conditions. Fibroblasts that were extruded from the samples were proliferated in vitro, and another set of samples were cultured as organ culture. A 24-well culture medium containing Dulbecco's modified minimum essential medium was supplemented by 12% fetal bovine serum. There were five laser-treated and five sham-exposed groups. A HeNe laser was used, and 0.9-4 J/cm2 energy densities were applied four times to each organ culture and cell culture. The organ cultures were analyzed by light microscopy and transmission electron microscopy examinations. Statistical analysis revealed that 4J/cm2 irradiation significantly increased the fibroblast numbers compared to the sham-exposed cultures.

The aim of a study by Simões (15) was to evaluate the effect of laser irradiation on the amylase and the antioxidant enzyme activities, as well as on the total protein concentration of submandibular glands (SMG) of diabetic and non-diabetic rats. Ninety-six

female rats were divided into eight groups: D0, D5, D10, and D20 (diabetic animals), and C0, C5, C10, and C20 (non-diabetic animals), respectively. Diabetes was induced by administering streptozotocin and confirmed later by the glycemia results. Twenty-nine days after diabetes induction, the SMG of groups D5 and C5, D10 and C10, and D20 and C20 were irradiated with 5, 10, and 20 J/cm2, respectively. A diode laser (660 nm/100 mW) was used. On the day after irradiation, the rats were euthanized and the SMG were removed. Catalase, peroxidase, and amylase activities, as well as protein concentration, were assayed. Diabetic rats without irradiation (D0) showed higher catalase activity when compared to C0. However, laser irradiation of 5, 10, and 20 J/cm2 reduced the catalase activity of diabetic groups (D5 and D20) to non-diabetic values. In conclusion, laser irradiation decreased catalase activity in diabetic rats' SMG.

The objective of another study by Simões (16) was to evaluate the effect of LPT on the glycemic state and the histological and ionic parameters of the parotid and submandibular glands in rats with diabetes. One hundred twenty female rats were divided into eight groups. Diabetes was induced by administration of streptozotocin and confirmed later according to results of glycemia testing. Twenty-nine days after the induction, the parotid and submandibular glands of the rats were irradiated with 5, 10, and 20 J/cm2 using diabetes: D5, D10, and D20, respectively). On the following day, the rats were euthanized, and blood glucose determined. Histological and ionic analyses were performed. Rats with diabetes without irradiation (D0) showed lipid droplets accumulation in the parotid gland, but accumulation decreased after 5, 10, and 20 J/cm2 of laser irradiation. A decrease in fasting glycemia level from 358.97+/-56.70 to 278.33+/-87.98 mg/dL for D5 and from 409.50+/-124.41 to 231.80+/-120.18 mg/dL for D20 was also observed. In conclusion, LPT could be explored as an auxiliary therapy for control of complications of diabetes because it can alter the carbohydrate and lipid metabolism of rats with diabetes.

Quotes from some studies

The studies above are just a few examples of recent research but to demonstrate the conclusions of recent studies, here are some quotes:

LLLT confers a protective effect against excessive inflammatory tissue response; it stimulates neovascularization and the early formation of collagen fibres.

The HeNe laser was effective in altering the inflammatory reaction and increasing TGF-β1 gene production.

Our study demonstrates that infrared LLLT can improve wound healing in diabetic rats.

LLLT improved the periodontal ligament and alveolar bone remodelling activity in diabetic rats during dental movement.

Laser photostimulation on tensile strength in diabetic wound suggests that such therapy facilitates collagen production in diabetic wound healing

According to this study, LLLT has a beneficial effect on the IR muscle injury treatment in the diabetic rats.

Laser therapy may have a beneficial effect for diabetic patients via decreasing arginase expression and activation of the NOS/NO pathway which increases NO production and vasodilation, and decreasing EGFR expression which may reduce neuro-inflammation and its secondary damages.

LLLT with He-Ne laser compared to Ga-Al-As laser has a positive healing effect on hard palate gingival wounds in STZ-D mice.

hBM-MSCs CM or LLLT alone increased the survival of HG HDFs cells. However, the combination of hBM-MSCs CM and LLLT improved these results in comparison to the conditioned medium.

Using LLLT with STSG might be a promising treatment for burn victims, especially diabetic patients.

We conclude that 980-nm GaAlAs low-intensity diode laser irradiation is beneficial for the initial stages of alveolar bone healing and for further calcification in both diabetic and normal rats when applied every day at a dose of 13.95 J/cm2 for 60 s.

Thus, 670nm LLLT may be broadly applicable to the amelioration of renal complications induced by diabetes that disrupt antioxidant defence mechanisms.

The study provides evidence that LLLT can accelerate the healing process of chronic diabetic foot ulcers, and it can be presumed that LLLT may shorten the time period needed to achieve complete healing.

The study demonstrates that diabetes-linked skin lesions have a special pattern in Egyptians and are apparently caused by deranged skin blood flow .The deficit is measurable by laser flowmetry and can be partially reversed by LILT.

LLLT at 2.9J/cm2 to the tenotomized Achilles tendons in the non-diabetic and diabetic rats significantly increased the strength and MS of repairing Achilles tendons in our study.

Low-level laser therapy increased the serum levels of alkaline phosphatase and improved bone healing in alloxan-induced diabetic rats.

This study shows that LILI stimulates Col-I synthesis in diabetic wound healing in vitro at 660 nm.

Laser treatments with a pulsed infrared laser at 0.2J/cm2 significantly accelerated wound healing in both healthy and diabetic rats.

To conclude, the results also showed that LLLT was able to alter the expression of MMP-9 as well as accelerate the production of collagen and increase the total percentage of collagen type III in diabetic animals.

The number of granulated mast cells was significantly higher than that of degranulated mast cells for all laser-treated mast cells and placebo mast cells of the non-diabetic and diabetic groups.

Treating the actual condition?

The studies above have evaluated the effect of PBM in wound healing under diabetic conditions. So much for the secondary phenomena of diabetes – the wounds. But can PBM influence the diabetic condition itself. A rodent study by Peplow (17) compared diabetic and non-diabetic rats and although the wound healing effect of PBM was demonstrated, the mean blood plasma glucose level was not significantly different between the two groups; glycated hemoglobin A1c was not detected in the samples But couldn’t PBM then be used to improve the diabetic condition in itself? In another study Peplow (18) still comes up with such a suggestion:

Forty-seven diabetic mice were used. Body weight and water intake of the mice were measured daily for 7 days prior to start of treatment (day 0). Mice were irradiated on the left

inguinal region with 810 nm laser 20.4 J/cm2 (n=15) or 40.8 J/cm2 (n=15) for 7 days, or were not irradiated (control, n=17). Body weight and water intake were measured to day 7. On day 7, mice were fasted for 5 h, anesthetized with sodium pentobarbitone (i.p.), and blood plasma was collected. The blood plasma was assayed for glucose and fructosamine. Water intake was significantly increased on day 7 compared with day 0 for diabetic mice receiving laser treatment. Blood plasma glucose levels on day 7 for diabetic mice irradiated 20.4 and 40.8 J/cm2 were not significantly different than for non-irradiated controls. The blood plasma fructosamine level of diabetic mice irradiated with 20.4 J/cm2 was significantly lower than for non-irradiated controls, whereas that for diabetic mice irradiated with 40.8 J/cm2 was not significantly different than for non-irradiated controls. Irradiation (810 nm, 10.2-20.4 J/cm2) to the left inguinal region of diabetic mice for 7 days has the potential to ameliorate diabetes, as is shown by decreased blood plasma fructosamine.

Contraindications?

In old literature, diabetes is sometimes listed as a contraindication for PBM. This is a complete misunderstanding, but stubbornly surviving in some circles. As can be seen from the above reports, PBM is a very promising therapy for diabetic ulcers. So are there no contraindications at all? Well, we do not know everything, so there are caveats. Bäckström (19) reports one case where lower blood sugar levels where observed directly after laser treatment. The diabetic patient was taking a new diabetes drug, Victoza (liraglutid). This pattern has been repeated and in this individual it seems to be a negative side effect to be taken into account. Except from that anecdotal observation, no negative effects have been reported.

Cost effectiveness

A new method needs to be at least as effective as traditional methods to be considered. This requirement is fulfilled. But preferably it should also be cost effective. So far there is no study proving this, but for radiation-induced oral mucositis it is. Diabetic wounds and oral mucositis are both conditions where wound healing is counteracted by downregulation of several mechanisms in the body. Two clinical evaluations (20, 21) have found PBM treatment of oral mucositis very cost effective.

Before PBM and after eight sessions. Courtesy Chrisse Bäckström, RN, Finland

Conclusion

Diabetic ulcers constitute a major health care problem with no very effective traditional treatment options. PBM has a fair scientific documentation, has hardly any side effects and is cost effective. Considering the poor treatment options at hand and the cumbersome situation for diabetic patients, it is time to seriously consider the introduction of PBM into mainstream medicine.

References:

1. Al-Watban FA. Laser therapy converts diabetic wound healing to normal healing. Photomed Laser Surg. 2009 Feb;27(1):127-35.

2. Al-Watban FA, Zhang XY, Andres BL. Low-level laser therapy enhances wound healing in diabetic rats: a comparison of different lasers. Photomed Laser Surg. 2007 Apr;25(2):72-7.

3. Tunér J. The Laser Wound Healing Contradiction. Photomed Laser Surg. 2015 Jun;33(6):343-4.

4. Obradović R, Kesić L, Mihailović D, Jovanović G, Antić S, Brkić Z. Low-level lasers as an adjunct in periodontal therapy in patients with diabetes mellitus. Diabetes Technol Ther. 2012 Sep;14(9):799-803.

5. Obradović R, Kesić L, Mihailović D, Antić S, Jovanović G, Petrović A, Peševska S. A histological evaluation of a low-level laser therapy as an adjunct to periodontal therapy in patients with diabetes mellitus. Lasers Med Sci. 2013 Jan;28(1):19-24.

6. Feitosa MC, Carvalho AF, Feitosa VC, Coelho IM, Oliveira RA, Arisawa E. Effects of the Low-Level Laser Therapy (LLLT) in the process of healing diabetic foot ulcers. Acta Cir Bras. 2015;30(12):852-857.

7. Tchanque-Fossuo CN, Ho D, Dahle SE, Koo E, Isseroff RR, Jagdeo J. Low-level Light Therapy for Treatment of Diabetic Foot Ulcer: A Review of Clinical Experiences. J Drugs Dermatol. 2016 Jul 1;15(7):843-8.

8. Beckmann KH, Meyer-Hamme G, Schröder S. Low level laser therapy for the treatment of diabetic foot ulcers: a critical survey. Evid Based Complement Alternat Med. 2014;2014:626127.

9 Kazemi-Khoo N. Successful treatment of diabetic foot ulcers with low-level laser therapy. The Foot. 2006; 16 (4): 184-187.

10. Schindl A, Merwald H, Schindl L. Low intensity laser irradiation stimulates endothelial cell proliferation in an in vitro model of diabetic microangiopathy. Laser Surg Med. 2001; Suppl 13: 7.

11. Houreld N, Abrahamse H. Effectiveness of Helium-Neon Laser Irradiation on Viability and Cytotoxicity of Diabetic-Wounded Fibroblast Cells. Photomed Laser Surg. 2007; 25 (6): 474-481.

12. Houreld N, Abrahamse H. Irradiation with a 632.8 nm helium-neon laser with 5 J/cm2

stimulates proliferation and expression of interleukin-6 in diabetic wounded fibroblast cells. Diabetes Technol Ther. 2007; 9 (5): 451-459.

13. Byrnes K R, Barna L, Chenault V M et al. Photobiomodulation improves cutaneous wound healing in an animal model of type II diabetes. Photomed Laser Surg. 2004; 22 (4):281-290.

14. Maiya G A, Kumar P, Rao L. Effect of low intensity helium-neon (He-Ne) laser irradiation on diabetic wound healing dynamics. Photomed Laser Surg. 2005; 23 (2): 187-190.

15. Simões A, Nogueira FN, Eduardo CD, Nicolau J. Diode Laser Decreases the Activity of Catalase on Submandibular Glands of Diabetic Rats. Photomed Laser Surg. 2010 Feb;28(1):91-5.

16. Simões A, de Oliveira E, Campos L, Nicolau J. Ionic and histological studies of salivary glands in rats with diabetes and their glycemic state after laser irradiation. Photomed Laser Surg. 2009; 27( 6): 877-883.

17. Peplow PV, Baxter GD. Testing infrared laser phototherapy (810 nm) to ameliorate diabetes: irradiation on body parts of diabetic mice. Lasers Surg Med. 2013 Apr;45(4):240-5.

18. Peplow PV, Baxter GD. Defining a therapeutic window for laser irradiation (810 nm) applied to the inguinal region to ameliorate diabetes in diabetic mice. Photomed Laser Surg. 2014 Sep;32(9):500-4.

19. Bäckström C. Personal information, 2015.

20. Bezinelli L M, de Paula Eduardo F, da Graca Lopes R M, Biazevic M G, de Paula Eduardo C, Correa L, Hamerschlak N, Michel-Crosato E. Cost-effectiveness of the introduction of specialized oral care with laser therapy in hematopoietic stem cell transplantation. Hematol Oncol. 2014; 32 (1): 31-39.

21. Antunes HS, Schluckebier LF, Herchenhorn D, Small IA, Araújo CM, Viégas CM, Rampini MP, Ferreira EM, Dias FL, Teich V, Teich N, Ferreira CG. Cost-effectiveness of low-level laser therapy (LLLT) in head and neck cancer patients receiving concurrent chemoradiation. Oral Oncol. 2016; 52:

Further reading

- Ibuki FK, Simões A, Nicolau J, Nogueira FN. Laser irradiation affects enzymatic antioxidant system of streptozotocin-induced diabetic rats. Lasers Med Sci. 2013 May;28(3):911-8.

- Simões A, Nogueira FN, de Paula Eduardo C, Nicolau J. Diode laser decreases the activity of catalase on submandibular glands of diabetic rats. Photomed Laser Surg. 2010 Feb;28(1):91-5.

- Basso FG, Oliveira CF, Kurachi C, Hebling J, Costa CA (2013) Biostimulatory effect of low-level laser therapy on keratinocytes in vitro. Lasers Med Sci 28:367-74.

- Houreld NN, Sekhejane PR, Abrahamse H (2010) Irradiation at 830 nm stimulates nitric oxide production and inhibits pro-inflammatory cytokines in diabetic wounded fibroblast cells. Lasers Surg Med 42:494-502.

- Bicalho Rabelo S, Balbin Villaverde A , Amadei Nicolau R, Castillo Salgado M A et al. Comparison between Wound Healing in Induced Diabetic and Nondiabetic Rats after Low- Level Laser Therapy. Photomed Laser Surg. 2006; 24 (4): 474-479.

- Sekhejane PR, Houreld NN, Abrahamse H (2011) Irradiation at 636 nm positively affects diabetic wounded and hypoxic cells in vitro. Photomed Laser Surg 29:521–530.

- Takhtfooladi HA, Asghari A, Amirkamali S, Hoseinzadeh HA, Takhtfooladi MA. Evaluation of low-level laser therapy on skeletal muscle ischemia-reperfusion in streptozotocin-induced diabetic rats by assaying biochemical markers and histological changes. Lasers Med Sci. 2016 Aug;31(6):1211-7.

- Fahimipour F, Houshmand B, Alemi P, Asnaashari M, Tafti MA, Akhoundikharanagh F, Farashah SE, Aminisharifabad M, Korani AS, Mahdian M, Bastami F, Tahriri M. The effect

of He-Ne and Ga-Al-As lasers on the healing of oral mucosa in diabetic mice. J Photochem Photobiol B. 2016 Jun;159:149-54.

- Hendudari F, Piryaei A, Hassani SN, Darbandi H, Bayat M. Combined effects of low-level laser therapy and human bone marrow mesenchymal stem cell conditioned medium on viability of human dermal fibroblasts cultured in a high-glucose medium. Lasers Med Sci. 2016 May;31(4):749-57.

- Dahmardehei M, Kazemikhoo N, Vaghardoost R, Mokmeli S, Momeni M, Nilforoushzadeh MA, Ansari F, Amirkhani A. Effects of low level laser therapy on the prognosis of split-thickness skin graft in type 3 burn of diabetic patients: a case series. Lasers Med Sci. 2016 Apr;31(3):497-502.

- Góralczyk K, Szymańska J, Szot K, Fisz J, Rość D. Low-level laser irradiation effect on endothelial cells under conditions of hyperglycemia. Lasers Med Sci. 2016 Jul;31(5):825-31.

- Mao Z, Wu JH, Dong T, Wu MX. Additive enhancement of wound healing in diabetic mice by low level light and topical CoQ10. Sci Rep. 2016 Feb 2;6:20084.

- Nascimento MF, Almeida BM, Cunha JL, Valois RB, Pinheiro JC, Ribeiro MA, Lima SO, Albuquerque-Júnior RL. Improvement of bone repair in diabetic rats subjected to ƛ780 nm low-level laser therapy. Acta Cir Bras. 2015 Oct;30(10):660-7.

- Fekrazad R, Mirmoezzi A, Kalhori KA, Arany P. The effect of red, green and blue lasers on healing of oral wounds in diabetic rats. J Photochem Photobiol B. 2015 Jul;148:242-5.

- KazemiKhoo N, Ansari F. Blue or red: which intravascular laser light has more effects in diabetic patients? Lasers Med Sci. 2015 Jan;30(1):363-6.

- Lau PS, Bidin N, Krishnan G, Nassir Z, Bahktiar H. Biophotonic effect of diode laser irradiance on tensile strength of diabetic rats. J Cosmet Laser Ther. 2015 Apr;17(2):86-9.

- Dancáková L, Vasilenko T, Kováč I, Jakubčová K, Hollý M, Revajová V, Sabol F, Tomori Z, Iversen M, Gál P, Bjordal JM. Low-level laser therapy with 810 nm wavelength improves skin wound healing in rats with streptozotocin-induced diabetes. Photomed Laser Surg. 2014 Apr;32(4):198-204.

- Aliodoust M, Bayat M, Jalili MR, Sharifian Z, Dadpay M, Akbari M, Bayat M, Khoshvaghti A, Bayat H. Evaluating the effect of low-level laser therapy on healing of tentomized Achilles tendon in streptozotocin-induced diabetic rats by light microscopical and gene expression examinations. Lasers Med Sci. 2014 Jul;29(4):1495-503.

- Kilík R, Lakyová L, Sabo J, Kruzliak P, Lacjaková K, Vasilenko T, Vidová M, Longauer F, Radoňak J. Effect of equal daily doses achieved by different power densities of low-level laser therapy at 635 nm on open skin wound healing in normal and diabetic rats. Biomed Res Int. 2014;2014:269253.

- Aparecida Da Silva A, Leal-Junior EC, Alves AC, Rambo CS, Dos Santos SA, Vieira RP, De Carvalho Pde T. Wound-healing effects of low-level laser therapy in diabetic rats involve the modulation of MMP-2 and MMP-9 and the redistribution of collagen types I and III. J Cosmet Laser Ther. 2013 Aug;15(4):210-6.

- Fathabadie FF, Bayat M, Amini A, Bayat M, Rezaie F. Effects of pulsed infra-red low level-laser irradiation on mast cells number and degranulation in open skin wound healing of healthy and streptozotocin-induced diabetic rats. J Cosmet Laser Ther. 2013 Dec;15(6):294-304.

- França CM, de Loura Santana C, Takahashi CB, Alves AN, De Souza Mernick AP, Fernandes KP, de Fátima Teixeira da Silva D, Bussadori SK, Mesquita-Ferrari RA. Effect of laser therapy on skeletal muscle repair process in diabetic rats. Lasers Med Sci. 2013 Sep;28(5):1331-8.

- Ayuk SM, Houreld NN, Abrahamse H. Collagen production in diabetic wounded fibroblasts in response to low-intensity laser irradiation at 660 nm. Diabetes Technol Ther. 2012 Dec;14(12):1110-7.

- Kazemi Khoo N, Iravani A, Arjmand M, Vahabi F, Lajevardi M, Akrami SM, Zamani Z. A metabolomic study on the effect of intravascular laser blood irradiation on type 2 diabetic patients. Lasers Med Sci. 2013 Nov;28(6):1527-32.

- Dadpay M, Sharifian Z, Bayat M, Bayat M, Dabbagh A. Effects of pulsed infra-red low level-laser irradiation on open skin wound healing of healthy and streptozotocin-induced diabetic rats by biomechanical evaluation. J Photochem Photobiol B. 2012 Jun 4;111:1-8.

- Nouruzian M, Alidoust M, Bayat M, Bayat M, Akbari M. Effect of low-level laser therapy on healing of tenotomized Achilles tendon in streptozotocin-induced diabetic rats. Lasers Med Sci. 2013 Feb;28(2):399-405.

- Park JJ, Kang KL. Effect of 980-nm GaAlAs diode laser irradiation on healing of extraction sockets in streptozotocin-induced diabetic rats: a pilot study. Lasers Med Sci. 2012 Jan;27(1):223-30.

- Saied GM, Kamel RM, Labib AM, Said MT, Mohamed AZ. The diabetic foot and leg: combined He-Ne and infrared low-intensity lasers improve skin blood perfusion and prevent potential complications. A prospective study on 30 Egyptian patients. Lasers Med Sci. 2011 Sep;26(5):627-32.

- Kaviani A, Djavid GE, Ataie-Fashtami L, Fateh M, Ghodsi M, Salami M, Zand N, Kashef N, Larijani B. A randomized clinical trial on the effect of low-level laser therapy on chronic diabetic foot wound healing: a preliminary report. Photomed Laser Surg. 2011 Feb;29(2):109-14.

- Lim J, Sanders RA, Snyder AC, Eells JT, Henshel DS, Watkins JB 3rd. Effects of low-level light therapy on streptozotocin-induced diabetic kidney. J Photochem Photobiol B. 2010 May 3;99(2):105-10.

- Chung TY, Peplow PV, Baxter GD. Laser photobiomodulation of wound healing in diabetic and non-diabetic mice: effects in splinted and unsplinted wounds. Photomed Laser Surg. 2010 Apr;28(2):251-61.

- Stadler I, Lanzafame RJ, Evans R, Narayan V, Dailey B, Buehner N, Naim JO. 830-nm irradiation increases the wound tensile strength in a diabetic murine model. Lasers Surg Med. 2001;28(3):220-6.

- Yu W, Naim JO, Lanzafame RJ. Effects of photostimulation on wound healing in diabetic mice. Lasers Surg Med. 1997;20(1):56-63.

- Rabelo SB, Villaverde AB, Nicolau R, Salgado MC, Melo Mda S, Pacheco MT. Comparison between wound healing in induced diabetic and nondiabetic rats after low-level laser therapy. Photomed Laser Surg. 2006 Aug;24(4):474-9.

- Carvalho PT, Mazzer N, dos Reis FA, Belchior AC, Silva IS. Analysis of the influence of low-power HeNe laser on the healing of skin wounds in diabetic and non-diabetic rats. Acta Cir Bras. 2006 May-Jun;21(3):177-83.

- Reddy GK. Comparison of the photostimulatory effects of visible He-Ne and infrared Ga-As lasers on healing impaired diabetic rat wounds. Lasers Surg Med. 2003;33(5):344-51.

- Zinman LH, Ngo M, Ng ET, Nwe KT, Gogov S, Bril V. Low-intensity laser therapy for painful symptoms of diabetic sensorimotor polyneuropathy: a controlled trial. Diabetes Care. 2004 Apr;27(4):921-4.