The low level laser therapy (LLLT) operating in 660 nm reduce gene expression of inflammatory mediators in the experimental model of collagenase-induced rat tendinitis

Shedding Light on Photobiomodulation Therapy for Age-Related Macular Degeneration: A Narrative Review

BACKGROUND

Photobiomodulation (PBM) relies on the pathophysiological mechanism whereby red to near-infrared light can target mitochondrial activity and promote ATP synthesis. Preclinical and clinical studies have shown promising results in treating intermediate age-related macular degeneration (AMD), since PBM can produce photochemical reactions in endogenous retinal chromophores. Currently, PBM is approved by the Food and Drug Administration and by the European Medicines Agency for the treatment of intermediate AMD. This narrative review aimed to evaluate the available evidence on the effectiveness and safety of PBM in treating intermediate AMD.

METHODS

A comprehensive search was conducted using the PubMed database, employing the keywords "photobiomodulation" and "age-related macular degeneration." All English-language studies published up to June 2023 were reviewed, and the search was expanded to include relevant references from selected articles. The included publications were analyzed for this review.

RESULTS

The available studies on PBM in AMD demonstrated promising but inconsistent results. PBM showed potential in improving best-corrected visual acuity (BCVA) and contrast sensitivity (CS) in patients with AMD. Some studies also suggested a reduction in AMD lesions, such as drusen volume. However, the long-term efficacy and optimal treatment parameters of PBM in AMD remained to be fully determined due to the limitations of the available studies. These included variations in irradiation techniques, wavelengths, exposure times, and treatment sessions, making it challenging to generalize the effectiveness of PBM. Furthermore, the lack of accurate classification of AMD phenotypes in the available studies hindered the understanding of which phenotypes could truly benefit from this treatment. Finally, the strength of evidence varied among studies, with limited sample sizes, unpublished results, and only three randomized sham-controlled trials.

CONCLUSIONS

Currently, the effectiveness of PBM in promoting drusen resorption or preventing progression to advanced forms of AMD, as observed in the cited studies, remains uncertain.

Histological, Physiological and Biomechanical Effects of Low-Level Laser Therapy on Tendon Healing in Animals and Humans: A Systematic Review

Low-level Laser Therapy (LLLT) was widely used in clinical practice for tendon disorders. However, the underlying mechanisms and effectiveness of LLLT in treating tendon injury remain unclear. Therefore, the present study was conducted aiming to summarize the evidence regarding the histological, physiological, and biomechanical effects of LLLT on tendon healing in animal and human models. Four databases were searched for relevant literature. Four independent reviewers screened abstracts and full-text articles, extracted relevant data, evaluated the risk of bias, and quantified the quality of evidence. Database searches yielded 1400 non-duplicated citations. Fifty-five studies were included (50 animal and five human studies). Animal studies revealed that LT had stimulating effects on collagen organization, collagen I and collagen II formation, matrix metalloproteinase (MMP)-8, transforming growth factor β1, vascular endothelial growth factor, hydroxyproline, maximum load, maximum elongation before breaking, and tendon stiffness. However, LLLT had inhibitory effects on the number of inflammatory cells, histological scores, relative amount of collagen III, cyclooxygenase-2, prostaglandin E2 (PGE2), interleukin-6, tumor necrosis factor-α, MMP-1, and MMP-3. Although one human study found that LLLT reduced the concentration of PGE2 in peritendinous tissue of the Achilles tendon, other human studies revealed that the effects of LLLT on the physiology and biomechanics of human tendons remained uncertain. LLLT facilitates tendon healing through various histological, physiological, and biomechanical effects in animal models. Only post-LLLT anti-inflammatory effects were found in human studies.

The Mechanisms and Efficacy of Photobiomodulation Therapy for Arthritis: A Comprehensive Review

Rheumatoid arthritis (RA) and osteoarthritis (OA) have a significant impact on the quality of life of patients around the world, causing significant pain and disability. Furthermore, the drugs used to treat these conditions frequently have side effects that add to the patient's burden. Photobiomodulation (PBM) has emerged as a promising treatment approach in recent years. PBM effectively reduces inflammation by utilizing near-infrared light emitted by lasers or LEDs. In contrast to photothermal effects, PBM causes a photobiological response in cells, which regulates their functional response to light and reduces inflammation. PBM's anti-inflammatory properties and beneficial effects in arthritis treatment have been reported in numerous studies, including animal experiments and clinical trials. PBM's effectiveness in arthritis treatment has been extensively researched in arthritis-specific cells. Despite the positive results of PBM treatment, questions about specific parameters such as wavelength, dose, power density, irradiation time, and treatment site remain. The goal of this comprehensive review is to systematically summarize the mechanisms of PBM in arthritis treatment, the development of animal arthritis models, and the anti-inflammatory and joint function recovery effects seen in these models. The review also goes over the evaluation methods used in clinical trials. Overall, this review provides valuable insights for researchers investigating PBM treatment for arthritis, providing important references for parameters, model techniques, and evaluation methods in future studies.

The effect of low-level red and near-infrared photobiomodulation on pain and function in tendinopathy: a systematic review and meta-analysis of randomized control trials

Background

Tendinopathy is a common clinical condition that can significantly affect a person’s physical function and quality of life. Despite exercise therapy being the mainstay of tendinopathy management, there are many potential adjunct therapies that remain under investigated, one of which is photobiomodulation (PBM). PBM uses varied wavelengths of light to create a biological effect. While PBM is used frequently in the management of tendinopathy, high quality evidence supporting its utility is lacking.

Methods

A systematic search of the Pubmed, CINAHL, SCOPUS, Cochrane Database, Web of Science and SPORTSDICUS databases was performed for eligible articles in August 2020. Randomized Control Trials that used red or near-infrared PBM to treat tendinopathy disorders that made comparisons with a sham or ‘other’ intervention were included. Pain and function data were extracted from the included studies. The data were synthesized using a random effects model. The meta-analysis was performed using the mean difference (MD) and standardized mean difference (SMD) statistics.

Results

A total of 17 trials were included (n = 835). When compared solely to other interventions PBM resulted in similar decreases in pain (MD -0.09; 95% CI − 0.79 to 0.61) and a smaller improvement in function (SMD -0.52; 95% CI − 0.81 to − 0.23). When PBM plus exercise was compared to sham treatment plus exercise, PBM demonstrated greater decreases in pain (MD 1.06; 95% CI 0.57 to 1.55) and improved function (MD 5.65; 95% CI 0.25 to 11.04). When PBM plus exercise was compared to other interventions plus exercise, no differences were noted in pain levels (MD 0.31; 95% CI − 0.07 to 0.70). Most studies were judged as low-risk of bias. The outcome measures were classified as very low to moderate evidence quality according to the Grading of Recommendation, Development and Evaluation tool.

Conclusion

There is very-low-to-moderate quality evidence demonstrating that PBM has utility as a standalone and/or adjunctive therapy for tendinopathy disorders.

Trial registration

PROPERO registration number: CRD42020202508.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-021-00306-z.

Photobiomodulation: A review of the molecular evidence for low level light therapy

Light energy is harnessed for therapeutic use in a number of ways, most recently by way of photobiomodulation (PBM). This phenomenon is a cascade of physiological events induced by the nonthermal exposure of tissue to light at the near infrared end of the visible spectrum. Therapeutic PBM has become a highly commercialized interest, marketed for everything from facial rejuvenation to fat loss, and diode-based devices are popular in both the clinic setting and for use at home. The lack of regulatory standards makes it difficult to draw clear conclusions about efficacy and safety but it is crucial that we understand the theoretical basis for PBM, so that we can engage in an honest dialogue with our patients and design better clinical studies to put claims of efficacy to the test. This article presents a summary of the science of PBM and examines the differences between laser light, on which much of the preclinical evidence is based and light from diodes, which are typically used in a clinical setting.

Photobiomodulation therapy on expression of HSP70 protein and tissue repair in experimental acute Achilles tendinitis

The aim of the present study was to investigate the effects of photobiomodulation (PBM) therapy on the expression of heat shock protein 70 (HSP70) and tissue repair in an experimental model of collagenase-induced Achilles tendinitis. Thirty Wistar rats (aged 12 weeks) were randomly distributed among control group (n = 8), tendinitis group (n = 11), and LED group (n = 11). Tendinitis was induced in the tendinitis and LED groups through a peritendinous injection of collagenase (100 μl). The LED group animals received the first irradiation 1 h after injury. A 630 ± 20 nm, 300-mW continuous wave light-emitting diode (LED), spot size 1 cm², was placed in contact with the skin. One point over the tendon was irradiated for 30 s, delivering 9 J (9 J/cm²). LED irradiation was performed once daily for 7 days, with the total energy delivered being 63 J. The tendons were surgically removed and expression of the HSP70 protein was calculated using semi-quantitative analyses of immunohistochemistry (HSCORE). Number of fibroblasts and amount of collagen were measured using histological and histochemical analyses. An increase in the mean HSCORE for HSP70, in the number of fibroblasts, and in the amount of collagen were found in the LED group compared with those in the tendinitis and control group (P ≤ 0.05). PBM therapy increased the expression of the HSP70, number of fibroblasts, and amount of collagen in the acute Achilles tendinitis in rats.

Molecular and Cellular Mechanisms of Arthritis in Children and Adults: New Perspectives on Applied Photobiomodulation

Juvenile idiopathic arthritis and adult rheumatoid arthritis are two major groups with chronic joint pain and inflammation, extra-articular manifestations, and high risk of comorbidities, which can cause physical and ocular disability, as well as create great socio-economic pressure worldwide. The pathogenesis of arthritis manifested in childhood and adulthood is multifactorial, unclear, and overly complex, in which immunity plays an important role. Although there are more and more biological agents with different mechanisms of action for the treatment of arthritis, the results are not as expected, because there are partial responses or non-responsive patients to these compounds, high therapeutic costs, side effects, and so on; therefore, we must turn our attention to other therapeutic modalities. Updating knowledge on molecular and cellular mechanisms in the comparative pathogenesis of chronic arthritis in both children and adults is necessary in the early and correct approach to treatment. Photobiomodulation (PBM) represents a good option, offering cost-effective advantages over drug therapy, with a quicker, more positive response to treatment and no side effects. The successful management of PBM in arthritis is based on the clinician’s ability to evaluate correctly the inflammatory status of the patient, to seek the optimal solution, to choose the best technology with the best physical parameters, and to select the mode of action to target very precisely the immune system and the molecular signaling pathways at the molecular level with the exact amount of quantum light energy in order to obtain the desired immune modulation and the remission of the disease. Light is a very powerful tool in medicine because it can simultaneously target many cascades of immune system activation in comparison with drugs, so PBM can perform very delicate tasks inside our cells to modulate cellular dysfunctions, helping to initiate self-organization phenomena and finally, healing the disease. Interdisciplinary teams should work diligently to meet these needs by also using single-cell imaging devices for multispectral laser photobiomodulation on immune cells.

Systematic Review of Photobiomodulation Therapy (PBMT) on the Experimental Calcaneal Tendon Injury in Rats

This systematic review analyzed the light parameters and the effects of photobiomodulation therapy (PBMT) through low-level laser therapy (LLLT) and/or LED (light-emitting diode) on tendon repair of rats submitted to calcaneal injury. This study was conducted in accordance with the guidelines of the Preferred Reporting Items for Meta-Analysis, and PubMed and MEDLINE databases were accessed to search eligible studies published in English. The search terms were as follows: "Achilles tendon" or "Calcaneal tendon" or "tendon injuries" or "soft tissue injuries" and "tendinopathy" or "tendinitis" and "low-level light therapy" or "low-level laser therapy" or "low intensity power therapy" or "light-emitting diode" or photobiomodulation." The SYRCLE (SYstematic Review Center for Laboratory animal Experimentation) risks of bias was used to assess the risk of bias for selected studies. A total of 225 studies were found based on the descriptors used, and only 33 studies were eligible. Light parameters identified per point of irradiation were approximately 60 mW (continuous mode at infrared spectra), 2 W cm^-2 , 2 J and 45 J cm^-2 . Light parameters at red spectra, continuous versus pulsed mode, and PBMT combined or compared with other therapies such as ultrasound, and studies using unhealthy rats (ovariectomized and/or diabetic models) were also identified and grouped according to these similarities. The main effects found were decreased inflammatory markers and signs of inflammatory process. PBMT (laser/LED) has positive effects in reducing the inflammatory and time for tissue repair in animal models of tendon injury and/or tendinitis using parameters identified.

Effect of photobiomodulation and exercise on early remodeling of the Achilles tendon in streptozotocin-induced diabetic rats

The aim of this study was to compare the treatment effects of laser photobiomodulation (LPBM) therapy and aerobic exercise on the biomechanical properties, tissue morphology and the expression of tendon matrix molecules during early remodeling of Achilles tendon (AT) injury in diabetic rats. Animals were randomly assigned to five groups: injured non diabetic (I, n = 15), injured diabetic (ID, n = 15), injured diabetic plus LPBM (IDL, n = 16), injured diabetic plus aerobic exercise (IDE, n = 16) and injured diabetic plus aerobic exercise and LPBM (IDEAL, n = 17). Type 1 diabetes was induced via a single intravenous injection of Streptozotocin at a dose of 40 mg/kg. A partial tenotomy was performed in the right AT. LPBM was performed with an indium-gallium-aluminum-phosphide 660 nm 10 mW laser device (spot size 0.04 cm², power density 250 mW/cm², irradiation duration 16 s, energy 0.16 J, energy density 4 J/cm²) on alternate days for a total of 9 sessions over 3 weeks (total energy 1.44 J), using a stationary contact technique to a single point over the dorsal aspect of the AT. Moderate aerobic exercise was performed on a motorized treadmill (velocity 9 m/min for 60 minutes). At 3 weeks post-injury, biomechanical analyzes as well as assessment of fibroblast number and orientation were performed. Collagen 1 (Col1) and 3 (Col3) and matrix metalloproteinases (MMPs) -3 and 13 protein distributions were studied by immunohistochemistry; while Col1 and Col3 and MMP-2 and 9 gene expression were assessed by quantitative RT-PCR (qRT-PCR). IDEAL exhibited significant increases in several biomechanical parameters in comparison to the other groups. Moreover, IDEAL presented stronger Col1 immunoreactivity when compared to ID, and weaker Col3 immunoreactivity than IDE. Both IDL and IDEAL demonstrated weaker expression of MMP-3 in comparison to I, while IDL presented no expression of MMP-13 when compared to ID. ID, IDL and IDE showed an increased number of fibroblasts in comparison to I, while IDEAL decreased the number of these cells in comparison to ID and IDE. IDL and IDEAL groups exhibited decreased angular dispersion among the fibroblasts when compared to I. The gene expression results showed that IDE demonstrated a downregulation in Col1 mRNA expression in comparison to I and ID. IDEAL demonstrated upregulation of Col1 mRNA expression when compared to IDL or IDE alone and increased MMP-2 expression when compared to IDL and IDE. MMP-9 expression was upregulated in IDEAL when compared to I, IDL and IDE. Our results suggest a beneficial interaction of combining both treatment strategies i.e., aerobic exercise and LPBM, on the biomechanical properties, tissue morphology and the expression of matrix molecules in diabetic tendons.

Modulation of immune response to induced-arthritis by low-level laser therapy

As low-level laser therapy immune cells responses are not always clarified, this study aimed to evaluate cytokines and immune cells profile after low-level laser therapy (LLLT) on arthritis-induced model. Arthritis was induced in C57BL/6 mice divided into five groups: euthanized 5 hours after inflammation induction; untreated; dexamethasone treated; LLLT at 3 Jcm^-2 ; LLLT at 30 Jcm^-2 . Cytokine measurements by enzyme-linked immunosorbent assay and mRNA cytokine relative levels by real-time quantitative polymerase chain reaction were performed with arthritic ankle (IL-1β, IL-6, TNF-α, IL-10 and TGF-β). Macrophages, dendritic cells, natural killer cells, lymphocytes CD4⁺ , CD8⁺ , Treg and costimulatory proteins were quantified in proximal lymph node by flow cytometry. Data showed decrease in all cytokine levels after LLLT and alteration in mRNA relative levels, depending on the energy density used. LLLT was able to increase of immune cell populations analyzed in the lymph node as well as costimulatory proteins expression on macrophages and dendritic cells. Treg TCD4⁺ and TCD8⁺ population enrichment were observed in LLLT at 3 and 30 Jcm^-2 groups, respectively. Furthermore, Treg TCD8⁺ cells expressing higher levels of CD25 were observed at LLLT at 30 Jcm^-2 group. Our results indicate that LLLT could change the inflammatory course of arthritis, tending to accelerate its resolution through immune cells photobiostimulation.

Wound-healing effects of 635-nm low-level laser therapy on primary human vocal fold epithelial cells: an in vitro study

Low-level laser therapy (LLLT) has been promoted for its beneficial effects on tissue healing and pain relief for skin and oral applications. However, there is no corresponding literature reporting on vocal fold wound healing. Our purpose was to assess the potential wound-healing effects of LLLT on primary human vocal fold epithelial cells (VFECs). In this study, normal vocal fold tissue was obtained from a 58-year-old male patient who was diagnosed with postcricoid carcinoma without involvement of the vocal folds and underwent total laryngectomy. Primary VFECs were then cultured. Cells were irradiated at a wavelength of 635 nm with fluences of 1, 4, 8, 12, 16, and 20 J/cm² (50 mW/cm²), which correspond to irradiation times of 20, 80, 160, 240, 320, and 400 s, respectively. Cell viability of VFECs in response to varying doses of LLLT was investigated by the Cell Counting Kit-8 (CCK-8) method. The most effective irradiation dose was selected to evaluate the cell migration capacity by using the scratch wound-healing assay. Real-time polymerase chain reaction (RT-PCR) was used to detect the gene expression of TGF-β1, TGF-β3, EGF, IL-6, and IL-10. Irradiation with doses of 8 J/cm² resulted in 4% increases in cell proliferation differing significantly from the control group (p < 0.05). With subsequent doses at 48 and 72 h after irradiation, the differences between the experimental and the control groups became greater, up to 9.8% (p < 0.001) and 19.5% (p < 0.001), respectively. It also increased cell migration and the expression of some genes, such as EGF, TGF-β1, TGF-β3, and IL-10, involved in the tissue healing process. This study concludes that LLLT at the preset parameters was capable of stimulating the proliferation and migration of human vocal fold epithelial cells in culture as well as increase the expression of some genes involved in tissue healing process. Additionally, successive laser treatments at 24 h intervals have an additive beneficial effect on the healing of injured tissues.

Aging of lymphoid organs: Can photobiomodulation reverse age-associated thymic involution via stimulation of extrapineal melatonin synthesis and bone marrow stem cells?

Thymic atrophy and the subsequent reduction in T-cell production are the most noticeable age-related changes affecting lymphoid organs in the immune system. In fact, thymic involution has been described as "programmed aging." New therapeutic approaches, such as photobiomodulation (PBM), may reduce or reverse these changes. PBM (also known as low-level laser therapy) involves the delivery of non-thermal levels of red or near-infrared light that are absorbed by mitochondrial chromophores, in order to prevent tissue death and stimulate healing and regeneration. PBM may reverse or prevent thymic involution due to its ability to induce extrapineal melatonin biosynthesis via cyclic adenosine monophosphate (AMP) or NF-kB activation, or alternatively by stimulating bone marrow stem cells that can regenerate the thymus. This perspective puts forward a hypothesis that PBM can alter thymic involution, improve immune functioning in aged people and even extend lifespan.

Evaluation of the therapeutic effects of led (λ627 ± 10 nm) on the initial phase of ankle sprain treatment: a randomised placebo-controlled clinical trial

Various therapies for the treatment of sprains have emerged as advances occur in biomedical engineering and photobiology. Therapy with coherent and non-coherent light is a treatment modality for various musculoskeletal injuries. The main certified phototherapy benefits are the reduction of nociceptive processes and the modulation of the inflammatory process, among others. The objective of this study was to analyse the changes caused by the use of light-emitting diodes (LED) (λ627 ± 10 nm) with an energy density of 10 J/cm² in 40 subjects divided into two groups (20 placebo and 20 LED). All of the volunteers had acute ankle sprains by inversion of grade II treated with the PRICE (protection, rest, ice, compression and elevation) technique and were treated for 6 days with LED therapy and LED therapy turned off (placebo). Pain assessment was performed on the 1st, 3rd and 6th days using the visual analogue scale (VAS) of pain, the McGill Pain Questionnaire and volumetry. The group treated with LED showed statistically decreased pain compared to the placebo group in both the VAS (85.79 vs 55.73%) and McGill questionnaire (83.33 vs 52.52%). The reduction of oedema in the LED group on the 3rd and 6th days after therapy was statistically superior to that in the placebo (p < 0.0001). Based on the results of this study, treatment with LED, using the tested dose, is effective for pain and oedema in the initial phase of ankle sprains.

Cytokines in tendon disease: A Systematic Review

OBJECTIVES

Emerging evidence indicates that tendon disease is an active process with inflammation that is critical to disease onset and progression. However, the key cytokines responsible for driving and sustaining inflammation have not been identified.

METHODS

We performed a systematic review of the literature using MEDLINE (U.S. National Library of Medicine, Bethesda, Maryland) in March 2017. Studies reporting the expression of interleukins (ILs), tumour necrosis factor alpha (TNF-α) and interferon gamma in diseased human tendon tissues, and animal models of tendon injury or exercise in comparison with healthy control tissues were included.

RESULTS

IL-1β, IL-6, IL-10, and TNF-α are the cytokines that have been most frequently investigated. In clinical samples of tendinopathy and tendon tears, the expression of TNF-α tended not to change but IL-6 increased in tears. Healthy human tendons showed increased IL-6 expression after exercise; however, IL-10 remained unchanged. Animal tendon injury models showed that IL-1β, IL-6, and TNF-α tend to increase from the early phase of tendon healing. In animal exercise studies, IL-1β expression showed a tendency to increase at the early stage after exercise, but IL-10 expression remained unchanged with exercise.

CONCLUSIONS

This review highlights the roles of IL-1β, IL-6, IL-10, and TNF-α in the development of tendon disease, during tendon healing, and in response to exercise. However, there is evidence accumulating that suggests that other cytokines are also contributing to tendon inflammatory processes. Further work with hypothesis-free methods is warranted in order to identify the key cytokines, with subsequent mechanistic and interaction studies to elucidate their roles in tendon disease development.Cite this article: W. Morita, S. G. Dakin, S. J. B. Snelling, A. J. Carr. Cytokines in tendon disease: A Systematic Review. Bone Joint Res 2017;6:656-664. DOI: 10.1302/2046-3758.612.BJR-2017-0112.R1.

Achilles Tendinopathy: Current Concepts about the Basic Science and Clinical Treatments

Achilles tendinopathy is one of the most frequently ankle and foot overuse injuries, which is a clinical syndrome characterized by the combination of pain, swelling, and impaired performance. The two main categories of Achilles tendinopathy are classified according to anatomical location and broadly include insertional and noninsertional tendinopathy. The etiology of Achilles tendinopathy is multifactorial including both intrinsic and extrinsic factors. Failed healing response and degenerative changes were found in the tendon. The failed healing response includes three different and continuous stages (reactive tendinopathy, tendon disrepair, and degenerative tendinopathy). The histological studies have demonstrated an increased number of tenocytes and concentration of glycosaminoglycans in the ground substance, disorganization and fragmentation of the collagen, and neovascularization. There are variable conservative and surgical treatment options for Achilles tendinopathy. However, there has not been a gold standard of these treatments because of the controversial clinical results between various studies. In the future, new level I researches will be needed to prove the effect of these treatment options.

Photobiomodulation therapy on collagen type I and III, vascular endothelial growth factor, and metalloproteinase in experimentally induced tendinopathy in aged rats

This study investigates the effect of photobiomodulation therapy (PBMT) on collagen type I and III, matrix metalloproteinase (MMP), and vascular endothelial growth factor (VEGF) in experimentally induced tendinopathy in female aged rats. Tendinopathy was induced by the Achilles tendoncollagenase peritendinous. Forty-two Wistar rats (Norvegicus albinus) were used; groups consisted of 36 aged animals (18 months old; mean body weight, 517.7 ± 27.54 g) and 6 adult animals (12 weeks old; mean body weight, 266± 19.30 g). The animals were divided into three groups: control, aged tendinopathy, and aged tendinopathy PBMT; the aged groups were subdivided based on time to euthanasia: 7, 14, and 21 days. PBMT involved a gallium-arsenide-aluminum laser (Theralaser, DMC®) with active medium operating at wavelength 830 ± 10 nm, 50 mW power, 0.028 cm² laser beam, 107 J/cm² energy density, 1.8 W/cm² power density, and an energy of 3 J per point. The laser was applied by direct contact with the left Achilles tendon during 60 s per point at a frequency of three times per week, until the euthanasia date (7, 14, and 21 days). VEGF, MMP-3, and MMP-9 were analyzed by immunohistochemistry, and collagen type I and III by Sirius red. PBMT increased the deposition of collagen type I and III in a gradual manner, with significant differences relative to the group aged tendonitis (p < 0.001), and in relation to VEGF (p < 0.001); decreased expression of MMP-3 and 9 were observed in group aged tendinopathy (p < 0.001). PBMT, therefore, increased the production of collagen type I and III, downregulated the expression of MMP-3 and MMP-9, and upregulated that of VEGF, with age and age-induced hormonal deficiency.

Adipose-Derived Stem Cells Improve Collagenase-Induced Tendinopathy in a Rat Model

BACKGROUND

Tendinopathy is a common and highly prevalent musculoskeletal disorder characterized by repetitive activity-related pain and focal tendon tenderness. Histopathologically, tendinopathic tissue mainly shows degenerative changes. Therefore, tendinopathy is not affected by anti-inflammatory therapies. A novel approach, including a stem cell-based therapy, may be beneficial for its treatment.

PURPOSE/HYPOTHESIS

The purpose of this study was to evaluate the effects of adipose-derived stem cells (ASCs) on tendon healing in a rat tendinopathy model. The hypothesis was that ASC transplantation would improve degeneration in collagenase-induced tendinopathy.

STUDY DESIGN

Controlled laboratory study.

METHODS

Sixteen F344/NSlc rats underwent collagenase injection into the Achilles tendon to induce tendinopathy. At 1 week after collagenase injection, 8 rats received ASCs (ASC group) and 8 received phosphate-buffered saline alone (PBS group). Animals were sacrificed at 4 or 12 weeks after ASC administration, and the degree of degeneration in each tendon was histologically evaluated according to the Bonar scale. The microstructure of healing tendons was observed by scanning electron microscopy. Reverse-transcription polymerase chain reaction (RT-PCR) was performed to measure the ratio of type III collagen messenger RNA (mRNA) to type I collagen mRNA in tendons.

RESULTS

The median Bonar scale score in the ASC and PBS groups was 2.5 and 5.33 at 4 weeks after treatment and 1.0 and 4.0 at 12 weeks after treatment, respectively. Histologically, the ASC group showed a significantly lower degree of tendon degeneration than the PBS group at both time points. In the RT-PCR analysis, the ratio of type III collagen to type I collagen was significantly lower in the ASC group than in the PBS group at 12 weeks after treatment. Moreover, this ratio decreased over time in the ASC group, whereas it increased over time in the PBS group.

CONCLUSION

The study findings demonstrate that the application of ASCs results in significant improvement in the pathological findings associated with tendinopathy and the normalization of collagen ratios within the affected tendon.

CLINICAL RELEVANCE

Subcutaneous adipose tissue can be harvested easily, and ASC administration might have the potential to rapidly treat tendinopathy.