Low level laser therapy accelerates the extracellular matrix reorganization of inflamed tendon

Histopathology Findings of Low-Level Laser Therapy Effectiveness on Achilles Tendon Repair in Rabbit Model

BACKGROUND

Low-level laser therapy (LLLT) has been utilized to treat tendinitis and various other musculoskeletal conditions. The current study assessed the impact of LLLT (650 and 750 nm) on tendon repair in rabbits.

MATERIALS AND METHODS

Fifteen 2-year-old male New Zealand White rabbits were divided into three groups: control, 650 nm laser and 750 nm laser therapy. After applying Achilles tendon-destructive surgery on their right legs, rabbits underwent LLLT, and tendon repair was assessed using histopathology and immunohistochemistry (IHC) findings. All data were analysed using SPSS version 21, considering a significant level <0.05.

RESULTS

The study's histopathological and immunohistochemical analysis revealed that LLLT at 650 and 750 nm significantly improved tendon healing compared to the control group (p < 0.05). The treated groups exhibited better organized tendon fibres with reduced discontinuity, collagen fibre waviness, and inflammatory response (p < 0.05). Both laser wavelengths showed similar results with no significant differences between them (p > 0.05), but both were notably better than the control group in reducing inflammation, enhancing fibre structure, and lowering levels of collagen type I (Col-I); collagen type III (Col-III); transformer growth factor beta (TGF-β); galectin-3 (galectin-3); VGF nerve growth factor inducible; vascular endothelial growth factor (VEGF), indicating a more effective healing process with LLLT.

CONCLUSION

Due to our findings, LLLT at 650 and 750 nm effectively reduced inflammation, improved structural integrity, and enhanced the organization of collagen fibres for Achilles tendon repair in rabbits.

Effects of photobiomodulation therapy (660-nm laser) on median nerve function in Wistar rats

This study investigates the effects of photobiomodulation (PBM) with a 660-nm laser on nerve regeneration and muscle morphometry following median nerve axonotmesis in rats. Sixteen Wistar rats were divided into a control group and laser-treated group, with the latter receiving 10 applications of PBM (660 nm; 20 mW; 10 J/cm2; 0.4 J; and 20 s) over 2 weeks. Functional analysis was performed using the grasping test, which measures the grip strength of the forelimb digits to evaluate motor function of the median nerve. Morphometric analyses were conducted on the median nerve, flexor digitorum (FD) muscle, and flexor carpi radialis (FCR) muscle. PBM led to functional improvement, with significant differences observed on the 21st day post-injury. However, no significant differences between groups were found in nerve morphometry. Morphometric analysis of the FD muscle revealed significant improvements in the PBM group, but with no significant differences regarding the FCR muscle. These findings suggest that 660-nm laser with the parameters used produced functional improvement as well as significant improvements in the morphometry of the FD muscle, but did not have significant effects on the morphometry of the FCR muscle or nerve regeneration.

Treatment options for Achilles tendinopathy: a scoping review of preclinical studies

Background

Achilles tendinopathy (AT) management can be difficult, given the paucity of effective treatment options and the degenerative nature of the condition. Innovative therapies for Achilles tendinopathy are therefore direly needed. New therapeutic developments predominantly begin with preclinical animal and in vitro studies to understand the effects at the molecular level and to evaluate toxicity. Despite the publication of many preclinical studies, a comprehensive, quality-assessed review of the basic molecular mechanisms in Achilles tendinopathy is lacking.

Objectives

This scoping review aims to summarize the literature regarding in vitro and in vivo animal studies examining AT treatments and evaluate their effect on tendon properties. Also, a quality assessment of the included animal studies is done. We provide a comprehensive insight into the current state of preclinical AT treatment research which may guide preclinical researchers in future research.

Eligibility criteria

Treatment options of Achilles tendinopathy in chemically or mechanically induced in vivo or in vitro Achilles tendinopathy models, reporting biomechanical, histological, and/or biochemical outcomes were included.

Sources of evidence

A systematically conducted scoping review was performed in PubMed, Embase.com, Clarivate Analytics/Web of Science, and the Wiley/Cochrane Library. Studies up to May 4, 2023 were included.

Charting Methods

Data from the included articles were extracted and categorized inductively in tables by one reviewer. The risk-of-bias quality assessment of the included animal studies is done with Systematic Review Centre for Laboratory Animal Experimentation risk-of-bias tool.

Results

A total of 98 studies is included, which investigated 65 different treatment options. 80% of studies reported significant improvement in the Achilles tendon characteristics after treatment. The main results were; maximum load and stiffness improvement; fibre structure recovered and less inflammation was observed; collagen I fibrils increased, collagen III fibrils decreased, and fewer inflammatory cells were observed after treatment. However, 65.4% to 92.5% of the studies had an uncertain to high risk of bias according to the risk-of-bias tool of the Systematic Review Centre for Laboratory Animal Experimentation.

Conclusions

Despite promising preclinical treatment outcomes, translation to clinical practice lags behind. This may be due to the poor face validity of animal models, heterogeneity in Achilles tendinopathy induction, and low quality of the included studies. Preclinical treatments that improved the biomechanical, histological, and biochemical tendon properties may be interesting for clinical trial investigation. Future efforts should focus on developing standardized preclinical Achilles tendinopathy models, improving reporting standards to minimize risk of bias, and facilitating translation to clinical practice.

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.

Influence of Three Laser Wavelengths with Different Power Densities on the Mitochondrial Activity of Human Gingival Fibroblasts in Cell Culture

Phototherapy plays a key role in wound healing and tissue regeneration. The use of lasers has the potential to become an effective and minimally invasive treatment in periodontal and peri-implant disease. The aim of this study was to evaluate the influence of three laser wavelengths with the combination of parameters such as power density and energy density on human gingival fibroblasts (hGFs) in vitro culture. Isolated cells were seeded in 96-well plates with culture medium (DMEM, Dulbecco's modified Eagle's medium) supplemented with 10% fetal bovine serum (FBS). After 24 h cells were irradiated (1064, 980 and 635 nm, various energy density value). After 24, 48 and 72 h, cells were evaluated for viability. Data were analyzed by ANOVA followed by Tukey's HSD test. We found the best outcomes for hGFs irradiated with laser 1064 nm for all combinations of power output (50/400/1000 mW) and energy dose (3/25/64 J/cm²) after 48 h and 72 h compared with control group. Cell viability increase ranged from 0.6× (3 J/cm², 50 mW) to 1.3× (64 J/cm², 1000 mW). Our findings indicate that the appropriate use of low-level laser irradiation (LLLI) can increase the proliferation rate of cultured cells. The use of LLLI can be extremely useful in tissue engineering and regenerative medicine.

The Therapeutic Effect of iMSC-Derived Small Extracellular Vesicles on Tendinopathy Related Pain Through Alleviating Inflammation: An in vivo and in vitro Study

Background

Tendinopathy is a common cause of tendon pain. However, there is a lack of effective therapies for managing tendinopathy pain, despite the pain being the most common complaint of patients. This study aimed to evaluate the therapeutic effect of small extracellular vesicles released from induced pluripotent stem cell-derived mesenchymal stem cells (iMSC-sEVs) on tendinopathy pain and explore the underlying mechanisms.

Methods

Rat tendinopathy model was established and underwent the injection of iMSC-sEVs to the quadriceps tendon one week after modeling. Pain-related behaviors were measured for the following four weeks. Tendon histology was assessed four weeks after the injection. To further investigate the potential mechanism, tenocytes were stimulated with IL-1β to mimic tendinopathy in vitro. The effect of iMSC-sEVs on tenocyte proliferation and the expression of proinflammatory cytokines were measured by CCK-8, RT-qPCR, and ELISA. RNA-seq was further performed to systematically analyze the related global changes and underlying mechanisms.

Results

Local injection of iMSC-sEVs was effective in alleviating pain in the tendinopathy rats compared with the vehicle group. Tendon histology showed ameliorated tendinopathy characteristics. Upon iMSC-sEVs treatment, significantly increased tenocyte proliferation and less expression of proinflammatory cytokines were observed. Transcriptome analysis revealed that iMSC-sEVs treatment upregulated the expression of genes involved in cell proliferation and downregulated the expression of genes involved in inflammation and collagen degeneration.

Conclusion

Collectively, this study demonstrated iMSC-sEVs protect tenocytes from inflammatory stimulation and promote cell proliferation as well as collagen synthesis, thereby relieving pain derived from tendinopathy. As a cell-free regenerative treatment, iMSC-sEVs might be a promising therapeutic candidate for tendinopathy.

Light Emitting Diodes Photobiomodulation Improves Cardiac Function by Promoting ATP Synthesis in Mice With Heart Failure

Heart failure (HF) is the common consequences of various cardiovascular diseases, often leading to severe cardiac output deficits with a high morbidity and mortality. In recent years, light emitting diodes-based therapy (LEDT) has been widely used in multiple cardiac diseases, while its modulatory effects on cardiac function with HF still remain unclear. Therefore, the objective of this study was to investigate the effects of LED-Red irradiation on cardiac function in mice with HF and to reveal its mechanisms. In this study, we constructed a mouse model of HF. We found that LED-Red (630 nm) was an effective wavelength for the treatment of HF. Meanwhile, the application of LED-Red therapy to treat HF mice improved cardiac function, ameliorate heart morphology, reduced pulmonary edema, as well as inhibited collagen deposition. Moreover, LED-Red therapy attenuated the extent of perivascular fibrosis. Besides, LED-Red irradiation promoted calcium transients in cardiomyocytes as well as upregulated ATP synthesis, which may have positive implications for contractile function in mice with HF. Collectively, we identified that LED-Red exerts beneficial effects on cardiac function in HF mice possibly by promoting the synthesis of ATP.

Photobiomodulation does not influence maturation and mildly improves functional healing of mouse achilles tendons

Tendon rupture can occur at any age and is commonly treated nonoperatively, yet can result in persisting symptoms. Thus, a need exists to improve nonoperative treatments of injured tendons. Photobiomodulation (PBM) therapy has shown promise in the clinic and is hypothesized to stimulate mitochondrial-related metabolism and improve healing. However, the effect of PBM therapy on mitochondrial function during tendon maturation and healing are unknown, and its effect on tendon structure and function remain unclear. In this study, near-infrared light (980:810 nm blend, 2.5 J/cm² ) was applied at low (30 mW/cm² ) or high (300 mW/cm² ) irradiance to unilateral Achilles tendons of CD-1 mice during postnatal growth (maturation) as well as adult mice with bilateral Achilles tenotomy (healing). The chronic effect of PBM therapy on tendon structure and function was determined using histology and mechanics, and the acute effect of PBM therapy on mitochondrial-related gene expression was assessed. During maturation and healing, collagen alignment, cell number, and nuclear shape were unaffected by chronic PBM therapy. We found a sex-dependent effect of PBM therapy during healing on mechanical outcomes (eg, increased stiffness and Young's modulus for PBM-treated females, and increased strain at ultimate stress for PBM-treated males). Mitochondria-related gene expression was marginally influenced by PBM therapy for both maturation and healing studies. This study was the first to implement PBM therapy during both growth and healing of the murine tendon. PBM therapy resulted in marginal and sex-dependent effects on the murine tendon. Clinical significance: PBM may be beneficial for tendon healing because functional remodeling improves without adverse effects.

High-Frequency Near-Infrared Diode Laser Irradiation Attenuates IL-1β-Induced Expression of Inflammatory Cytokines and Matrix Metalloproteinases in Human Primary Chondrocytes

High-frequency near-infrared diode laser provides a high-peak output, low-heat accumulation, and efficient biostimulation. Although these characteristics are considered suitable for osteoarthritis (OA) treatment, the effect of high-frequency near-infrared diode laser irradiation in in vitro or in vivo OA models has not yet been reported. Therefore, we aimed to assess the biological effects of high-frequency near-infrared diode laser irradiation on IL-1β-induced chondrocyte inflammation in an in vitro OA model. Normal Human Articular Chondrocyte-Knee (NHAC-Kn) cells were stimulated with human recombinant IL-1β and irradiated with a high-frequency near-infrared diode laser (910 nm, 4 or 8 J/cm²). The mRNA and protein expression of relevant inflammation- and cartilage destruction-related proteins was analyzed. Interleukin (IL) -1β treatment significantly increased the mRNA levels of IL-1β, IL-6, tumor necrosis factor (TNF) -α, matrix metalloproteinases (MMP) -1, MMP-3, and MMP-13. High-frequency near-infrared diode laser irradiation significantly reduced the IL-1β-induced expression of IL-1β, IL-6, TNF-α, MMP-1, and MMP-3. Similarly, high-frequency near-infrared diode laser irradiation decreased the IL-1β-induced increase in protein expression and secreted levels of MMP-1 and MMP-3. These results highlight the therapeutic potential of high-frequency near-infrared diode laser irradiation in OA.

Penetration Profiles of a Class IV Therapeutic Laser and a Photobiomodulation Therapy Device in Equine Skin

Photobiomodulation therapy (PBMT) effects depend on the energy settings and laser penetration. We investigated the penetration time profiles of two different light therapy devices, at the dark and light skin regions in horses. Six light skin and six dark skin adult clinically healthy Arab and Quarter horses were used. A cutometer was used to measure the width of the skin fold from both sides of the cervical area, followed by three measurements of the thickness of the same skin fold by transversal and longitudinal ultrasonography (US). The depth of light penetration was compared based on the percentage of penetration versus power, between a portable PBMT device versus a class IV laser device. The laser mean power output was measured with an optical power meter system for 120 seconds after penetrating the skin. Skin width and laser penetration were compared among equipment by paired "t" test. There was no difference in the width of the skin fold between measurements acquired by the cutometer against either longitudinal or transversal US or between the US measurements at cervical versus metacarpus area. Light penetration was greater in both kinds of skins in the PBMT (0.01303 ± 0.00778) versus class IV laser (0.00122 ± SD 0.00070) (P < .001). The PBMT device provided a greater energy penetration than the class IV laser in unclipped light and dark skin, suggesting that the former may produce a better therapeutic effect. The color of the skin changes penetration profiles of PBMT.

Evaluation of metalloproteinases-2, -9, and -13 post photobiomodulation in mice talocrural joint

The extracellular matrix (ECM) is the main constituent of connective tissue with structural and regulatory functions, stimulating cell differentiation and proliferation. Moreover, ECM is a dynamic structure in the constant remodeling process, which is controlled by a balance between metalloproteinases (MMPs) and their inhibitors (TIMPs). Photobiomodulation (PBM) is widely described in the literature and applied in clinical practices, although its effects on ECM have not yet been elucidated. Therefore, it was evaluated if PBM could alter ECM components, such as MMP-2, -9, -13, and TIMP-2 from mice talocrural joints. Mice were divided into 3 groups (n = 6): control, PBM 3 J cm^-2, and PBM 30 J cm^-2. A low-level laser (830 nm, 10 mW, 0.05 irradiated area, energy densities 3 J cm^-2 and 30 J cm^-2, the irradiation time of 15 and 150 s, respectively, continuous wave) was applied on the joint for 4 consecutive days. mRNA levels of metalloproteinases genes (MMP-2, MMP-9, and MMP-13), their regulator (TIMP-2), and protein expressions of MMP-13 and TIMP-2 were quantified. PBM can alter only mRNA relative levels of MMP-2 at 30 J cm^-2 (p < 0.05), while MMP-9, MMP-13, and TIMP-2 mRNA relative levels did not demonstrate statistical differences for any of the groups (p > 0.05). Regarding protein expressions, MMP-13 demonstrated positive-labeled cells, only in articular cartilage, although the cell quantification did not demonstrate statistical differences when compared with the control group (p > 0.05). TIMP-2 did not present positive-labeled cells for any tissues evaluated. Our results indicate that PBM can alter MMP-2 mRNA relative level but cannot alter MMP-9, MMP-13, and TIMP mRNA relative levels. Moreover, both MMP-13 and TIMP-2 proteins were also unaltered after PBM.

Photobiomodulation of Matrix Metalloproteinases in Rat Calcaneal Tendons

Objective: The main objective was to verify the modulatory effects of MMP-1, MMP-3, and MMP-13 levels on the partially injured calcaneal tendons of rat exposure to photobiomodulation. Background: Photobiomodulation has been shown to have anti-inflammatory and regenerative effects on tendon injuries. However, there is still uncertainty regarding the beneficial effects in matrix metalloproteinase (MMP) levels, especially MMP-1, -3, and -13. Materials and methods: Sixty-five male Wistar rats were used. Sixty were submitted to a direct trauma on the calcaneal tendons and were randomly distributed into the following six groups: LASER 1, 3, and 7 (10 partially injured calcaneal tendons in each group treated with photobiomodulation for 1, 3, and 7 days, respectively) and Sham 1, 3, and 7 (same injury, with simulated photobiomodulation). The remaining five animals were allocated to the normal group (no injury or treatment procedure). The 780 nm low-level laser was applied with 70 mW of mean power and 17.5 J/cm² of fluency for 10 sec, once a day. The tendons were surgically removed and analyzed for MMP-1, MMP-3, and MMP-13 through immunohistochemistry. Results: MMP-3 levels remained close to normal in all experimental groups (p > 0.05); however, reductions (p < 0.05) in MMP-1 and MMP-13 levels were detected in the groups submitted to one, three, and seven low level laser therapy applications. Conclusions: The photobiomodulation protocol was able to reduce MMP-1 and MMP-13 levels in injured calcaneal tendons.