Low-level laser irradiation promotes the recovery of atrophied gastrocnemius skeletal muscle in rats

Pulsed Red and Blue Photobiomodulation for the Treatment of Thigh Contusions and Soft Tissue Injury: A Randomized Controlled Trial

CONTEXT

Contusion and soft tissue injuries are common in sports. Photobiomodultion, light and laser therapy, is an effective aid to increase healing rates and improve function after various injury mechanisms. However, it is unclear how well photobiomodulation improves function after a contusion soft tissue injury. This study aimed to determine the effects of a pulsed red and blue photobiomodulation light patch on muscle function following a human thigh contusion injury.

DESIGN

Single-blinded randomized control trial design.

METHODS

We enrolled 46 healthy participants. Participants completed 5 visits on consecutive days. On the first visit, participants completed a baseline isokinetic quadriceps strength testing protocol at 60°/s and 180°/s. On the second visit, participants were struck in the rectus femoris of the anterior thigh with a tennis ball from a serving machine. Immediately following, participants were treated for 30 minutes with an active or placebo photobiomodulation patch (CareWear light patch system, CareWear Corp). Following the treatment, participants completed the same isokinetic quadriceps strength testing protocol. Participants completed the treatment and isokinetic quadriceps strength test during the following daily visits. We normalized the data by calculating the percent change from baseline. We used a mixed model analysis of covariance, with sex as a covariate, to determine the difference between treatment groups throughout the acute recovery process.

RESULTS

We found the active photobiomodulation treatment significantly increased over the placebo group, quadriceps peak torque during the 180°/s test (P = .030), and average power during both the 60°/s (P = .041) and 180°/s (P ≤ .001) assessments. The mean peak torque and average power of 180°/s, at day 4, exceeded the baseline levels by 8.9% and 16.8%, respectively.

CONCLUSIONS

The red and blue photobiomodulation light patch improved muscle strength and power during the acute healing phase of a human thigh contusion injury model.

Effect of 650 nm laser photobiomodulation therapy on the HT-7 (shenmen) acupoint in the Mus musculus model of Parkinson's disease

Background

Parkinson's disease is one of the neurodegenerative conditions that impacts 1-2% of the world's population. The only effective therapy for this condition today is to restore the biochemical function of the diseased dopamine neurons by giving them Levodopa or L-3,4-dihydroxyphenylalanine (l-DOPA). The risk of progenitor stem cells, though, is the growth of teratomas or the uncontrolled growth of cells. As a result, an alternative or additional method is needed, such as photobiomodulation therapy using a laser diode. In this research, male mice (Mus musculus), which were used as models for Parkinson's disease in an in vivo paraquat study, to determine the optimal dose of photobiomodulation therapy and a laser diode was used as a treatment.

Methods

The three sample groups are Group P-L- (control group, induced by 0.9% NaCl), Group P + L- (only caused by paraquat), and Group P + L+. (Treatment group, treated by paraquat and photobiomodulation therapy with a laser diode). Photobiomodulation treatment doses of 0.14 J, 0.29 J, 0.37 J, 0.76 J, 1.14 J, and 1.52 J were used in the P+L+ subgroups (6 groups). The laser diode generated a continuous wave with a wavelength of 658 nm, a beam spot of 2.10 mm, and an output power of 15.42 mW. After treatment, the histopathology results of each sample were inspected under a microscope.

Result

In Parkinson's disease-affected mice, paraquat has been shown to reduce the number of neurons. According to the results of the histopathological examination, photobiomodulation therapy using a laser diode (P + L+) on the HT-7 (Shenmen) may raise the quantity of neurons and the proportion of healthy cells in the mouse brain.

Conclusion

The effective radiated energy of the photobiomodulation therapy using laser diode treatment on the muscle musculus cell model of Parkinson's disease is 0.76 J.

Pilates Method and/or Photobiomodulation Therapy Combined to Static Magnetic Field in Women with Stress Urinary Incontinence: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

This clinical trial aims to provide evidence about the effectiveness of the Pilates method on stress urinary incontinence (SUI), as well as to elucidate the effects of photobiomodulation therapy associated with static magnetic field (PBMT/sMF) alone or associated with the Pilates Method on Pelvic floor muscle (PFM) in women affected by SUI. For that, a three-arm, parallel randomized, double-blinded, placebo-controlled trial was conducted (NCT05096936). We recruited thirty-three women diagnosed with SUI, randomly allocated to three groups: placebo PBMT/sMF plus method Pilates, PBMT/sMF active plus method Pilates and only PBMT/sMF active. The evaluation consisted of anamnesis and physical examination, muscle strength, completion of the ICIQ-SF questionnaire, and urinary loss. The evaluation of muscle strength and filling the ICIQ-SF were performed on the first and last days, while the Pad test was applied in baseline, one month, two months, and three months of intervention. We observed an increase in strength (p < 0.01), tone (p < 0.01), and quality of life (p < 0.01), in addition to a decrease in urinary lost (p < 0.01) for all groups comparing the pre and post-intervention. The PBMT/sMF alone, the Pilates, and the combination of the two therapies proved to be effective in improving the signs and symptoms of women with SUI.

Vascular photobiomodulation increases muscle fiber diameter and improves the gait during compensatory hypertrophy of plantar muscle in rats

The local photobiomodulation (LPBM) has demonstrated positive effects during compensatory hypertrophy (CH) in skeletal muscle as a response to an overload. The aim was to compare the effects of the transcutaneous vascular photobiomodulation (VPBM) and the LPBM on muscle fiber size, gait functionality, and on mechanical sensitivity during the CH model in rats. VPBM was administered over the rat's main tail vein and LPBM was applied over the plantar muscle region. VPBM induced an increase in muscle fiber diameter and cross-sectional area (CSA) after 7 days. At 14 days, an increase in the fiber diameter was found in both irradiated groups. The VPBM and LPBM promoted the reestablishment of normal gait evaluated by the sciatic functional index after 14 days. No changes were found in the mechanical (nociceptive) sensitivity in VPBM and LPBM groups in comparison to the CH group but there was an increase in the nociceptive sensitivity in the CH groups in comparison to the control after 7 and 14 days. In conclusion, both PBM, vascular and local, were able to improve the muscle size and gait during the CH process with more pronounced effects when irradiation was performed systemically (VPBM).

Deconstructing the Ergogenic Effects of Photobiomodulation: A Systematic Review and Meta-analysis of its Efficacy in Improving Mode-Specific Exercise Performance in Humans

BACKGROUND

Photobiomodulation therapy (PBMT) is defined as non-thermal electromagnetic irradiation through laser or light-emitting diode sources. In recent decades, PBMT has attracted attention as a potential preconditioning method. The current meta-analysis was conducted to assess the effectiveness of PBMT in improving mode-specific exercise performance in healthy young adults.

METHODS

A computerized literature search was conducted, ending on 15 May 2022. The databases searched were PubMed, Cochrane Central Register of Controlled Trials, Embase, SPORTDiscus, and the Physiotherapy Evidence Database. Inclusion/exclusion criteria limited articles to crossover, double-blind, placebo-controlled studies investigating the PBMT effects as a preconditioning method. The included trials were synthesized according to exercise mode (single-joint, cycling, running, and swimming). All results were combined using the standardized mean differences (SMDs) method and the 95% confidence intervals (CIs) were described.

RESULTS

A total of 37 individual studies, employing 78 exercise performance measurements in 586 participants, were included in the analyses. In single-joint exercises, PBMT improved muscle endurance performance (SMD 0.27, 95% CI 0.12-0.41; p < 0.01) but not muscle strength performance (p = 0.92). In cycling, PBMT improved time to exhaustion performance (SMD 0.35, 95% CI 0.10-0.59; p < 0.01) but had no effect on all-out sprint performance (p = 0.96). Similarly, PBMT had no effect on time to exhaustion (p = 0.10), time-trial (p = 0.61), or repeated-sprint (p = 0.37) performance in running and no effect on time-trial performance in swimming (p = 0.81).

CONCLUSION

PBMT improves muscle endurance performance in single-joint exercises and time to exhaustion performance in cycling but is not effective for muscle strength performance in single-joint exercises, running, or swimming performance metrics.

Effect of Photobiomodulation on Denervation-Induced Skeletal Muscle Atrophy and Autophagy: A Study in Mice

OBJECTIVE

The purpose of this study was to investigate whether photobiomodulation (PBM) can protect against and attenuate muscle atrophy owing to complete peripheral nerve lesion in mice by acting on autophagy.

METHODS

C57BL/10 mice underwent right sciatic nerve transection to induce tibialis anterior muscle atrophy. After 6 hours of denervation, the mice received PBM (wavelength, 830 nm) daily, transcutaneously over the tibialis anterior muscle region for 5 or 14 days. Some mice with sciatic nerve lesion did not receive PBM. Mice that did not have sciatic nerve lesion and PBM were used as controls. After 5 and 14 days, the right tibialis anterior muscle was examined using histomorphometric (cross-sectional area of muscle fibers), Western blot (levels of the autophagy marker LC3), and immunofluorescence analyses (number of LC3 puncta in the muscle fibers).

RESULTS

The cross-sectional area of the tibialis anterior muscle fibers decreased after 5 and 14 days of denervation. PBM protected against muscle fiber atrophy after 5 days of denervation and attenuated muscle fiber atrophy after 14 days of denervation. After 5 days of muscle denervation, autophagy did not change, as demonstrated by the comparable levels of LC3-I/II ratio and LC3 puncta between the controls and the mice with atrophic muscle; PBM did not change this profile. After 14 days of denervation, an increased LC3-I/II ratio suggested an ongoing autophagy, which was not affected by PBM.

CONCLUSION

PBM attenuated the tibialis anterior muscle atrophy induced by sciatic nerve transection in the mice after at least 5 and 14 days of muscle denervation, without affecting autophagy. The transient protective effect of PBM was observed as early as 5 days after the of complete nerve lesion.

Combined application of chondroitinase ABC and photobiomodulation with low-intensity laser on the anal sphincter repair in rabbit

Background

Photobiomodulation with low-intensity laser (LIL) and chondroitinase ABC (ChABC) can repair damaged muscle tissue, so the aim of this study was to investigate the effect of co-administration of these two factors on anal sphincter repair in rabbits.

Methods

Male rabbits were studied in 5 groups (n = 7): Control (intact), sphincterotomy, laser, ChABC and laser + ChABC. 90 days after intervention were evaluated resting and maximum squeeze pressures, number of motor units, collagen amount, markers of muscle regeneration and angiogenesis.

Results

Resting pressure in the Laser + ChABC group was higher than the sphincterotomy, laser and ChABC groups (p < 0.0001). Maximum squeeze pressure in the all study groups was higher than sphincterotomy group (p < 0.0001). In the laser + ChABC and ChABC groups, motor unit numbers were more than the sphincterotomy group (p < 0.0001). Collagen content was significantly decreased in the laser (p < 0.0001) and laser + ChABC groups. ACTA1 (p = 0.001) and MHC (p < 0.0001) gene expression in the Laser + ChABC group were more than the laser or ChABC alone. VEGFA (p = 0.009) and Ki67 mRNA expression (p = 0.01) in the Laser + ChABC group were more than the laser group, But vimentin mRNA expression (p < 0.0001) was less than the laser group.

Conclusion

Co-administration of ChABCs and photobiomodulation with LIL appears to improve the tissue structure and function of the anal sphincter in rabbits more than when used alone.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-021-02047-2.

Low-level laser prevents doxorubicin-induced skeletal muscle atrophy by modulating AMPK/SIRT1/PCG-1α-mediated mitochondrial function, apoptosis and up-regulation of pro-inflammatory responses

Background

Doxorubicin (Dox) is a widely used anthracycline drug to treat cancer, yet numerous adverse effects influencing different organs may offset the treatment outcome, which in turn affects the patient’s quality of life. Low-level lasers (LLLs) have resulted in several novel indications in addition to traditional orthopedic conditions, such as increased fatigue resistance and muscle strength. However, the mechanisms by which LLL irradiation exerts beneficial effects on muscle atrophy are still largely unknown.

Results

The present study aimed to test our hypothesis that LLL irradiation protects skeletal muscles against Dox-induced muscle wasting by using both animal and C2C12 myoblast cell models. We established SD rats treated with 4 consecutive Dox injections (12 mg/kg cumulative dose) and C2C12 myoblast cells incubated with 2 μM Dox to explore the protective effects of LLL irradiation. We found that LLL irradiation markedly alleviated Dox-induced muscle wasting in rats. Additionally, LLL irradiation inhibited Dox-induced mitochondrial dysfunction, apoptosis, and oxidative stress via the activation of AMPK and upregulation of SIRT1 with its downstream signaling PGC-1α. These aforementioned beneficial effects of LLL irradiation were reversed by knockdown AMPK, SIRT1, and PGC-1α in C2C12 cells transfected with siRNA and were negated by cotreatment with mitochondrial antioxidant and P38MAPK inhibitor. Therefore, AMPK/SIRT1/PGC-1α pathway activation may represent a new mechanism by which LLL irradiation exerts protection against Dox myotoxicity through preservation of mitochondrial homeostasis and alleviation of oxidative stress and apoptosis.

Conclusion

Our findings may provide a novel adjuvant intervention that can potentially benefit cancer patients from Dox-induced muscle wasting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00719-w.

Effects of Photobiomodulation/Laser Therapy Combined With Resistance Training on Quadriceps Hypertrophy and Strength, and Postural Balance in Older Women: A Randomized, Triple-Blinded, Placebo-Controlled Study

BACKGROUND AND PURPOSE

Physical and therapeutic strategies to maintain and rehabilitate skeletal muscle mass, strength, and postural balance are clinically relevant to improve the health, well-being, and quality of life of older adults. The purpose of this study was to investigate the effects of photobiomodulation (PBM)/laser therapy combined with a resistance training (RT) program on quadriceps hypertrophy and strength, and postural balance in older women.

METHODS

In a randomized, triple-blinded, placebo-controlled design, twenty-two older women (age 66.6 ± 5.2 years) were engaged in a supervised 10-wk RT program (2 times per week) involving unilateral leg extension exercise, in which each leg of the same participant was randomly assigned to receive active (λ = 808 nm, optical output = 100 mW, total energy = 42 J) or placebo laser PBM immediately before the RT sessions. Maximal dynamic strength by unilateral knee extension 1-repetition maximum (1RM), muscle hypertrophy by vastus lateralis muscle thickness, and postural balance by one-legged stance test on a force platform were assessed before and after the training program.

RESULTS

Significance statistical analysis revealed a similar improvement (time P = .003) from pre- to posttraining for muscle hypertrophy and strength, and postural balance between active and placebo laser conditions. However, clinical interpretation for muscle hypertrophy showed a moderate effect (effect size [ES] = 0.58) for the active laser and a small effect (ES = 0.38) for the placebo laser. Clinical difference was not noticed between conditions for other analyzed variables.

CONCLUSIONS

These findings indicate that RT alone can be clinically important for counteracting the deleterious effects of aging on muscle size, strength, and balance, and that applying laser PBM therapy before the RT sessions may further improve gains in muscle hypertrophy.

Bidirectional myofiber transition through altering the photobiomodulation condition

Despite remarkable advancements in modern medicine, muscular atrophy remains as an unsolved problem. It is well known that pathological characteristics of different atrophy types could vary according to the pathophysiological causes. In fact, the lesion of atrophy is not always homogenously distributed but often predominantly evident in either fast or slow myofibers. As the focalization of the atrophic lesions, the existence and the functional impairment of each fast and slow progenitor/satellite cell (SC) are suspected though there are still controversies about this hypothesis. In this study, we isolated Pax7 positive (Pax7^+ve) SCs from the tibia anterior (fast) and soleus (slow) muscles respectively and successfully demonstrated, for the first time, the difference between optimal exposure durations of photobiomodulation (PBM) which was known as low level laser irradiation (LLLI) in promoting proliferation of Pax7^+ve SC which were acquired from fast and slow muscles respectively. Moreover, a hypertrophy-accompanied bidirectional change in myofiber composition with neuromuscular junction alteration, either from slow to fast or fast to slow, were achieved by applying different PBM durations. Simultaneously, PBM exhibited a synergistic effect with muscle exercise on the increase in myofiber size. Our data suggested the existence of at least two different populations of Pax7^+ve SC which possess distinct sensitivities towards PBM. As our data revealed the capability of PBM in bidirectional changes of skeletal muscle composition and neuromuscular junction constitution thereby strengthen its contractility through altering the irradiation condition, we believe PBM showed the potential to be as a promising clinical treatment for muscular atrophy.

Effects of reloading after chronic neuromuscular inactivity on the three-dimensional capillary architecture in rat soleus muscle

The purpose of the study was to investigate the effects of ambulatory reloading following hindlimb unloading on the three-dimensional (3D) capillary architecture of rat soleus muscle. In this study, 15 male Sprague-Dawley rats were used. The rats were randomly assigned to the following 3 groups: a normal weight bearing control group (CON), 14 days of hindlimb unloading group (HU), and 14 days of hindlimb unloading followed by 7 days of ambulatory reloading group (HU-RL). The capillary diameter and volume were measured using confocal laser microscopy, and capillary number was determined by two-dimensional (2D) capillary staining in the soleus muscle of each group. The capillary diameter and volume as well as the capillary number were significantly lower in the HU group than in the CON group and significantly higher in the HU-RL group than in the HU group. These results provided novel information about the effectiveness of reloading following unloading on not only the 2D increase in capillary number but also the 3D capillary remodeling in the diameter and volume within the unloaded soleus muscle.

Combination of laser and human adipose-derived stem cells in repair of rabbit anal sphincter injury: a new therapeutic approach

Background

Anal sphincter injury leads to fecal incontinence. Based on the regenerative capability of laser and human adipose-derived stem cells (hADSCs), this study was designed to assess the effects of co-application of these therapies on anal sphincter recovery after injury.

Design

Male rabbits were assigned to equal groups (n = 7) including control, sphincterotomy, sphincterotomy treated with laser (660 nm, 90 s, immediately after sphincterotomy, daily, 14 days), hADSCs (2 × 10⁶ hADSCs injected into injured area of the sphincter immediately after sphincterotomy), and laser + hADSCs. Ninety days after sphincterotomy, manometry and electromyography were performed, sphincter collagen content was evaluated, and Ki67, myosin heavy chain (MHC), skeletal muscle alpha-actin (ACTA1), vascular endothelial growth factor A (VEGFA), and vimentin mRNA gene expression were assessed.

Results

The laser + hADSCs group had a higher resting pressure compared with the sphincterotomy (p < 0.0001), laser (p < 0.0001), and hADSCs (p = 0.04) groups. Maximum squeeze pressure was improved in all treated animals compared with the sphincterotomized animals (p < 0.0001), without a significant difference between treatments (p > 0.05). In the laser + hADSCs group, motor unit numbers were higher than those in the laser group (p < 0.0001) but did not differ from the hADSCs group (p = 0.075). Sphincterotomy increased collagen content, but the muscle content (p = 0.36) and collagen content (p = 0.37) were not significantly different between the laser + hADSCs and control groups. Laser + hADSCs increased ACTA1 (p = 0.001) and MHC (p < 0.0001) gene expression compared with laser or hADSCs alone and was associated with increased VEGFA (p = 0.009) and Ki67 mRNA expression (p = 0.01) and decreased vimentin mRNA expression (p < 0.0001) compared with laser.

Conclusion

The combination of laser and hADSCs appears more effective than either treatment alone for promoting myogenesis, angiogenesis, and functional recovery after anal sphincterotomy.

Effects of photobiomodulation therapy combined to static magnetic field in strength training and detraining in humans: protocol for a randomised placebo-controlled trial

INTRODUCTION

In recent years, it has been demonstrated that photobiomodulation therapy (PBMT) using low-level laser therapy and/or light-emitting diode therapy combined to static magnetic field (sMF) has ergogenic effects, improving muscular performance and accelerating postexercise recovery. However, many aspects related to these effects and its clinical applicability remain unknown. Therefore, the aim of this project is to evaluate the ergogenic effects of PBMT/sMF in detraining after a strength-training protocol.

METHODS AND ANALYSIS

The study will be a randomised, triple-blind, placebo-controlled clinical trial. Healthy male volunteers will be randomly distributed into four experimental groups: PBMT/sMF before training sessions + PBMT/sMF during detraining, PBMT/sMF before training sessions + placebo during detraining, placebo before training sessions + PBMT/sMF during detraining and placebo before training sessions + placebo during detraining. Strength-training sessions will be carried out over 12 weeks, and the detraining period will occur during the 4 weeks after. The muscular strength and the structural properties of quadriceps will be analysed.

ETHICS AND DISSEMINATION

This study was approved by the Research Ethics Committee of Nove de Julho University. The results from this study will be disseminated through scientific publications in international peer-reviewed journals and presented at national and international scientific meetings.

TRIAL REGISTRATION NUMBER

NCT03858179.

A transient protective effect of low-level laser irradiation against disuse-induced atrophy of rats

Satellite cells, a population of skeletal muscular stem cells, are generally recognized as the main and, possibly, the sole source of postnatal muscle regeneration. Previous studies have revealed the potential of low-level laser (LLL) irradiation in promoting satellite cell proliferation, which, thereby, boosts the recovery of skeletal muscle from atrophy. The purpose of this study is to investigate the beneficial effect of LLL on disuse-induced atrophy. The optimal irradiation condition of LLL (808 nm) enhancing the proliferation of Pax7^+ve cells, isolated from tibialis anterior (TA) muscle, was examined and applied on TA muscle of disuse-induced atrophy model of the rats accordingly. Healthy rats were used as the control. On one hand, transiently, LLL was able to postpone the progression of atrophy for 1 week through a reduction of apoptosis in Pax7^-veMyoD^+ve (myocyte) population. Simultaneously, a significant enhancement was observed in Pax7^+veMyoD^+ve population; however, most of the increased cells underwent apoptosis since the second week, which suggested an impaired maturation of the population. On the other hand, in normal control rats with LLL irradiation, a significant increase in Pax7^+veMyoD^+ve cells and a significant decrease of apoptosis were observed. As a result, a strengthened muscle contraction was observed. Our data showed the capability of LLL in postponing the progression of disuse-induced atrophy for the first time. Furthermore, the result of normal rats with LLL irradiation showed the effectiveness of LLL to strengthen muscle contraction in healthy control.

Photobiomodulation Therapy in Veterinary Medicine: A Review

Laser therapy, or photobiomodulation, has rapidly grown in popularity in human and veterinary medicine. With a number of proposed indications and broad, sometimes anecdotal, use in practice, research interest has expanded aimed at providing scientific support. Recent studies have shown that laser therapy alters the inflammatory and immune response as well as promotes healing for a variety of tissue types. This review will cover the history of the modality, basic principles, proposed mechanisms of action, evidence-based clinical indications, and will guide the practitioner through its application in practice.

Infrared Laser Improves Collagen Organization in Muscle and Tendon Tissue During the Process of Compensatory Overload

BACKGROUND

The photobiomodulation using the low-level laser therapy (LLLT) exerts a positive modulating effect on the synthesis of collagen in skeletal muscles and tendons. However, few studies have addressed this effect during the compensatory overload.

OBJECTIVE

Evaluate the effect of infrared laser on the deposition and organization of collagen fibers in muscle and tendon tissue during compensatory overload of the plantar muscle in rats.

MATERIALS AND METHODS

Wistar rats were submitted to bilateral ablation of the synergist muscles of the hind paws and divided in groups: Control, Hypertrophy, and Hypertrophy (H)+LLLT (780 nm, 40 mW, 9.6 J/cm² and 10 s/point, 8 points, total energy 3.2 J, daily), evaluated at 7 and 14 days. Muscle cuts were stained with Picrosirius-Red and hematoxylin-eosin and tendon cuts were submitted to birefringence for determination of collagen distribution and organization.

RESULTS

After 7 days an increase was observed in the area between beam muscles in H+LLLT (25.45% ± 2.56) in comparison to H (20.3% ± 3.31), in mature fibers and fibrilis in H+LLLT (29346.88 μm² ± 2182.56; 47602.8 μm² ± 2201.86 respectively) in comparison to H (26656.5 μm² ± 1880.46; 45630.34 μm² ± 2805.82 respectively) and in the collagen area in H+LLLT (2.25% ± 0.19) in comparison to H (2.0% ± 0.15). However, after 14 days a reduction was observed in the area between beam muscles in H+LLLT (13.88% ± 2.54) in comparison to H (19.1% ± 2.61), in fibrils and mature fibers in H+LLLT (17174.1 μm² ± 2563.82; 32634.04 μm² ± 1689.38 respectively) in comparison to H (55249.86 μm² ± 1992.65; 44318.36 μm² ± 1759.57) and in the collagen area in H+LLLT (1.76% ± 0.16) in comparison to H (2.09 ± 0.27). A greater organization of collagen fibers in the tendon was observed after 7 and 14 days in H+LLLT groups.

CONCLUSIONS

Infrared laser irradiation induces an improvement in collagen organization in tendons and a reduction in the total area of collagen in muscles during compensatory atrophy following the ablation of synergist muscles.

Inducible satellite cell depletion attenuates skeletal muscle regrowth following a scald-burn injury

KEY POINTS

Severe burns result in significant skeletal muscle cachexia that impedes recovery. Activity of satellite cells, skeletal muscle stem cells, is altered following a burn injury and likely hinders regrowth of muscle. Severe burn injury induces satellite cell proliferation and fusion into myofibres with greater activity in muscles proximal to the injury site. Conditional depletion of satellite cells attenuates recovery of myofibre area and volume following a scald burn injury in mice. Skeletal muscle regrowth following a burn injury requires satellite cell activity, underscoring the therapeutic potential of satellite cells in the prevention of prolonged frailty in burn survivors.

ABSTRACT

Severe burns result in profound skeletal muscle atrophy; persistent muscle atrophy and weakness are major complications that hamper recovery from burn injury. Many factors contribute to the erosion of muscle mass following burn trauma, and we have previously shown concurrent activation and apoptosis of muscle satellite cells following a burn injury in paediatric patients. To determine the necessity of satellite cells during muscle recovery following a burn injury, we utilized a genetically modified mouse model (Pax7CreER -DTA) that allows for the conditional depletion of satellite cells in skeletal muscle. Additionally, mice were provided 5-ethynyl-2'-deoxyuridine to determine satellite cell proliferation, activation and fusion. Juvenile satellite cell-wild-type (SC-WT) and satellite cell-depleted (SC-Dep) mice (8 weeks of age) were randomized to sham or burn injury consisting of a dorsal scald burn injury covering 30% of total body surface area. Both hindlimb and dorsal muscles were studied at 7, 14 and 21 days post-burn. SC-Dep mice had >93% depletion of satellite cells compared to SC-WT (P < 0.05). Burn injury induced robust atrophy in muscles located both proximal and distal to the injury site (∼30% decrease in fibre cross-sectional area, P < 0.05). Additionally, burn injury induced skeletal muscle regeneration, satellite cell proliferation and fusion. Depletion of satellite cells impaired post-burn recovery of both muscle fibre cross-sectional area and volume (P < 0.05). These findings support an integral role for satellite cells in the aetiology of lean tissue recovery following a severe burn injury.

Effects of photobiomodulation therapy on Bothrops moojeni snake-envenomed gastrocnemius of mice using enzymatic biomarkers

Bothropic venom contains a range of biologically active substances capable of causing severe local and systemic envenoming symptomatology within its victims. The snake anti-venom is effective against systemic effects but has no neutralizing effect against the fast developing local effects. Herein, mice gastrocnemius injected with Bothrops moojeni venom (40 μg/kg) or saline solution were irradiated with HeNe (632.8 nm) and GaAs (904 nm) lasers (daily energy density of 4 J/cm²; 0.03/0.21 power density; 0.07/0.16 spot size; 1.2/0.04 total energy, 1 cm off contact, for HeNe and GaAs lasers, respectively) and euthanized in periods ranging from 3 h to 21 days. Blood biochemistry for creatine kinase (CK), alkaline phosphatase (ALP), acid phosphatase (AP), lactate dehydrogenase (LDH), aspartate transaminase (AST), and myoglobin and histopathological analysis, for assessing the degree of myonecrosis and regeneration of gastrocnemius, were done at every time interval. GaAs laser promoted faster photobiomodulation therapy (PBMT) effects, and the GaAs group exhibited a better clinical outcome than the HeNe group. Within the GaAs group, the serum levels of CK, LDH, AP, AST, and myoglobin, which were increased by the physiological effects of the venom, were reduced to initial baseline before snake envenomation in less time than those irradiated by the HeNe laser. However, the group receiving irradiation from the HeNe laser returned the levels of ALP activity to baseline faster than those of the GaAs group. Histopathological analysis revealed enhanced muscle regeneration in mice groups treated with both lasers. PBM promoted by GaAs and HeNe showed well-developed centrally nucleate regenerating cells and an increased number of newly formed blood vessels when compared to unirradiated muscle. We therefore suggest that GaAs had the best outcomes likely derived from a deeper penetrating longer wavelength. We conclude that PMBT is a promising, non-invasive approach to be further tested in pre-clinical studies with a goal to further its clinical use in skeletal muscle recovery in snakebite victims.

Comparison of Ozone and Photo-Biomodulation Therapies on Mental Nerve Injury in Rats

PURPOSE

This study compared photo-biomodulation (PBM) and ozone therapy (OT) for mental nerve injury by counting Schwann cells (SCs) and fasciculated nerve branches and measuring fascicular nerve areas.

MATERIALS AND METHODS

The effects of OT and PBM on mental nerve injury were evaluated. Mental nerves of 27 rats were partly sutured and allocated into 3 groups. Group 1 received no treatment, group 2 received OT, and group 3 received PBM. The number of fascicules beyond nerve branches and the number of SCs before and after nerve injury were evaluated histologically.

RESULTS

A better healing pattern was observed in the treatment groups. The number of SCs was markedly larger in the OT and PBM groups than in the control group.

CONCLUSIONS

Oral and maxillofacial surgeons should be familiar with the differential diagnosis, prevention, and management of neurosensory disturbances. This study provides insights into the management of neurosensory disturbances related to mental nerve injury using OT and PBM. This study clearly suggests that OT and PBM are promising novel methods for the treatment of mental nerve injury.

Histomorphologic and ultrastructural recovery of myopathy in rats treated with low-level laser therapy

The purpose of the present work was to study the effect of low-level laser therapy (LLLT): helium-neon (He-Ne) and gallium arsenide (Ga-As) laser on the histomorphology of muscle and mitochondria in experimental myopathy in rats. Thirty Suquía strain female rats were distributed in groups: (A) control (intact), (B) injured, (C) injured and treated with He-Ne laser, (D) injured and treated with Ga-As laser, (E) irradiated with He-Ne laser on the non-injured muscle, and (F) irradiated with Ga-As laser on the non-injured muscle. Myopathy was induced by injecting 0.05 mg/rat/day of adrenaline in the left gastrocnemius muscle at the same point on five consecutive days, in groups B, C, and D. LLLT was applied with 9.5 J cm^-2 daily for seven consecutive days in groups C, D, E, and F. The muscles were examined with optic and electronic microscopy. The inflammation was classified as absent, mild, and intense and the degree of mitochondrial alteration was graded I, II, III, and IV. Categorical data were statistically analyzed by Chi-square and the Fisher-Irwin Bilateral test, setting significant difference at p < 0.05. The damage found in muscle and mitochondria histomorphology in animals with induced myopathy (B) was intense or severe inflammation with grade III or IV of mitochondrial alteration. They underwent significant regression (p < 0.001) compared with the groups treated with He-Ne (C) and Ga-As (D) laser, in which mild or moderate inflammation was seen and mitochondrial alteration grades I and II, recovering normal myofibrillar architecture. No differences were found between the effects caused by the two lasers, or between groups A, E, and F. Group A was found to be different from B, C, and D (p < 0.001). LLLT in experimental myopathy caused significant muscular and mitochondrial morphologic recovery.

Photobiomodulation Protects and Promotes Differentiation of C2C12 Myoblast Cells Exposed to Snake Venom

BACKGROUND

Snakebites is a neglected disease and in Brazil is considered a serious health problem, with the majority of the snakebites caused by the genus Bothrops. Antivenom therapy and other first-aid treatments do not reverse local myonecrose which is the main sequel caused by the envenomation. Several studies have shown the effectiveness of low level laser (LLL) therapy in reducing local myonecrosis induced by Bothropic venoms, however the mechanism involved in this effect is unknown. In this in vitro study, we aimed to analyze the effect of LLL irradiation against cytotoxicity induced by Bothrops jararacussu venom on myoblast C2C12 cells.

METHODOLOGY

C2C12 were utilized as a model target and were incubated with B. jararacussu venom (12.5 μg/mL) and immediately irradiated with LLL at wavelength of red 685 nm or infrared 830 nm with energy density of 2.0, 4.6 and 7.0 J/cm2. Effects of LLL on cellular responses of venom-induced cytotoxicity were examined, including cell viability, measurement of cell damage and intra and extracellular ATP levels, expression of myogenic regulatory factors, as well as cellular differentiation.

RESULTS

In non-irradiated cells, the venom caused a decrease in cell viability and a massive release of LDH and CK levels indicating myonecrosis. Infrared and red laser at all energy densities were able to considerably decrease venom-induced cytotoxicity. Laser irradiation induced myoblasts to differentiate into myotubes and this effect was accompanied by up regulation of MyoD and specially myogenin. Moreover, LLL was able to reduce the extracellular while increased the intracellular ATP content after venom exposure. In addition, no difference in the intensity of cytotoxicity was shown by non-irradiated and irradiated venom.

CONCLUSION

LLL irradiation caused a protective effect on C2C12 cells against the cytotoxicity caused by B. jararacussu venom and promotes differentiation of these cells by up regulation of myogenic factors. A modulatory effect of ATP synthesis may be suggested as a possible mechanism mediating cytoprotection observed under laser irradiation.

Investigation of the Comparative Effects of Red and Infrared Laser Therapy on Skeletal Muscle Repair in Diabetic Rats

OBJECTIVE

The aim of this study was to evaluate the in vivo response of 2 different laser wavelengths (red and infrared) on skeletal muscle repair process in diabetic rats.

DESIGN

Forty Wistar rats were randomly divided into 4 experimental groups: basal control-nondiabetic and muscle-injured animals without treatment (BC); diabetic muscle-injured without treatment (DC); diabetic muscle-injured, treated with red laser (DCR) and infrared laser (DCIR). The injured region was irradiated daily for 7 consecutive days, starting immediately after the injury using a red (660 nm) and an infrared (808 nm) laser.

RESULTS

The histological results demonstrated in both treated groups (red and infrared wavelengths) a modulation of the inflammatory process and a better tissue organization located in the site of the injury. However, only infrared light significantly reduced the injured area and increased MyoD and myogenin protein expression. Moreover, both red and infrared light increased the expression of the proangiogenic vascular endothelial growth factor and reduced the cyclooxygenase 2 protein expression.

CONCLUSION

These results suggest that low-level laser therapy was efficient in promoting skeletal muscle repair in diabetic rats. However, the effect of infrared wavelength was more pronounced by reducing the area of the injury and modulating the expression proteins related to the repair.

Differentiation Potential of Adipose-Derived Stem Cells When Cocultured with Smooth Muscle Cells, and the Role of Low-Intensity Laser Irradiation

OBJECTIVE

The aim of the study was to investigate the differentiation potential of adipose-derived stem cells (ADSCs) when cocultured with smooth muscle cells (SMCs), and to determine the role of low-intensity laser irradiation (LILI).

BACKGROUND DATA

ADSCs isolated from adipose tissue are isolated with ease and in large amounts. SMCs constitute most parts of the intestinal, urinary, reproductive, and cardiovascular systems. LILI has been found to have positive effects on different cell types, including ADSCs.

METHODS

The study used ADSCs (Stempro Adipose Derived Stem Cells-R7788-115) and SMCs (SKU-T-1 American Type Culture Collection HTB-114) cell lines. These cell lines were cocultured in a 1:1 ratio with and without growth factors and then exposed to LILI using 636 nm at 5 J/cm².

RESULTS

Cell viability and proliferation increased significantly in the cocultured groups that were exposed to LILI alone, as well as in combination with growth factors. Further, there was a significant decrease in the expression of stem cell markers with a concomitant increase in SMC markers.

CONCLUSIONS

These results suggest that ADSCs have the ability to differentiate into SMCs when cocultured with SMCs, whereas LILI potentially augments the differentiation potential and need. This further highlights the significant role that LILI has to offer ADSC therapy in regenerative medicine.

Effect of low-level laser therapy (808 nm) on skeletal muscle after endurance exercise training in rats

BACKGROUND:

Low-level laser therapy (LLLT) has been demonstrated to be effective in optimizing skeletal muscle performance in animal experiments and in clinical trials. However, little is known about the effects of LLLT on muscle recovery after endurance training.

OBJECTIVE:

This study evaluates the effects of low-level laser therapy (LLLT) applied after an endurance training protocol on biochemical markers and morphology of skeletal muscle in rats.

METHOD:

Wistar rats were divided into control group (CG), trained group (TG), and trained and laser irradiated group (TLG). The endurance training was performed on a treadmill, 1 h/day, 5 days/wk, for 8 wk at 60% of the maximal speed reached during the maximal effort test (Tmax) and laser irradiation was applied after training.

RESULTS:

Both trained groups showed significant increase in speed compared to the CG. The TLG demonstrated a significantly reduced lactate level, increased tibialis anterior (TA) fiber cross-section area, and decreased TA fiber density. Myogenin expression was higher in soleus and TA muscles in both trained groups. In addition, LLLT produced myogenin downregulation in the TA muscle of trained animals.

CONCLUSION:

These results suggest that LLLT could be an effective therapeutic approach for stimulating recovery during an endurance exercise protocol.

Light-emitting diode therapy in exercise-trained mice increases muscle performance, cytochrome c oxidase activity, ATP and cell proliferation

Light-emitting diode therapy (LEDT) applied over the leg, gluteus and lower-back muscles of mice using a LED cluster (630 nm and 850 nm, 80 mW/cm(2) , 7.2 J/cm(2) ) increased muscle performance (repetitive climbing of a ladder carrying a water-filled tube attached to the tail), ATP and mitochondrial metabolism; oxidative stress and proliferative myocyte markers in mice subjected to acute and progressive strength training. Six bi-daily training sessions LEDT-After and LEDT-Before-After regimens more than doubled muscle performance and increased ATP more than tenfold. The effectiveness of LEDT on improving muscle performance and recovery suggest applicability for high performance sports and in training programs. Positioning of the mice and light-emitting diode therapy (LEDT) applied on mouse legs, gluteus and lower-back muscles without contact.

Low-Level Laser Therapy (LLLT) in Dystrophin-Deficient Muscle Cells: Effects on Regeneration Capacity, Inflammation Response and Oxidative Stress

The present study evaluated low-level laser therapy (LLLT) effects on some physiological pathways that may lead to muscle damage or regeneration capacity in dystrophin-deficient muscle cells of mdx mice, the experimental model of Duchenne muscular dystrophy (DMD). Primary cultures of mdx skeletal muscle cells were irradiated only one time with laser and analyzed after 24 and 48 hours. The LLLT parameter used was 830 nm wavelengths at 5 J/cm² fluence. The following groups were set up: Ctrl (untreated C57BL/10 primary muscle cells), mdx (untreated mdx primary muscle cells), mdx LA 24 (mdx primary muscle cells - LLLT irradiated and analyzed after 24 h), and mdx LA 48 (mdx primary muscle cells - LLLT irradiated and analyzed after 48 h). The mdx LA 24 and mdx LA 48 groups showed significant increase in cell proliferation, higher diameter in muscle cells and decreased MyoD levels compared to the mdx group. The mdx LA 48 group showed significant increase in Myosin Heavy Chain levels compared to the untreated mdx and mdx LA 24 groups. The mdx LA 24 and mdx LA 48 groups showed significant increase in [Ca2+]i. The mdx group showed significant increase in H2O2 production and 4-HNE levels compared to the Ctrl group and LLLT treatment reduced this increase. GSH levels and GPx, GR and SOD activities increased in the mdx group. Laser treatment reduced the GSH levels and GR and SOD activities in dystrophic muscle cells. The mdx group showed significant increase in the TNF-α and NF-κB levels, which in turn was reduced by the LLLT treatment. Together, these results suggest that the laser treatment improved regenerative capacity and decreased inflammatory response and oxidative stress in dystrophic muscle cells, indicating that LLLT could be a helpful alternative therapy to be associated with other treatment for dystrophinopathies.

Pre-exercise low-level laser therapy improves performance and levels of oxidative stress markers in mdx mice subjected to muscle fatigue by high-intensity exercise

This study was designed to determine if the levels of oxidative stress markers are influenced by low-level laser therapy (LLLT) in mdx mice subjected to high-intensity exercise training on an electric treadmill. We used 21 C57BL/10ScSn-Dmdmdx/J mice and 7 C57BL/10ScSn mice, all aged 4 weeks. The mice were divided into four groups: a positive control group of normal, wild-type mice (WT); a negative control group of untreated mdx mice; a group of mdx mice that underwent forced high-intensity exercise on a treadmill (mdx fatigue); and another group of mdx mice with the same characteristics that were treated with LLLT at a single point on the gastrocnemius muscle of the hind paw and underwent forced high-intensity exercise on a treadmill. The mdx mice treated with LLLT showed significantly lower levels of creatine kinase (CK) and oxidative stress than mdx mice that underwent forced high-intensity exercise on a treadmill. The activities of the antioxidant enzyme superoxide dismutase (SOD) were higher in control mdx mice than in WT mice. LLLT also significantly reduced the level of this marker. LLLT had a beneficial effect also on the skeletal muscle performance of mdx mice. However, the single application of LLLT and the dose parameters used in this study were not able to change the morphology of a dystrophic muscle.

Low-level laser therapy on skeletal muscle inflammation: evaluation of irradiation parameters

We evaluated the effect of different irradiation parameters in low-level laser therapy (LLLT) for treating inflammation induced in the gastrocnemius muscle of rats through cytokines concentration in systemic blood and analysis of muscle tissue. We used continuous (830 and 980 nm) and pulsed illuminations (830 nm). Animals were divided into five groups per wavelength (10, 20, 30, 40, and 50 mW), and a control group. LLLT was applied during 5 days with a constant irradiation time and area. TNF-α, IL-1β, IL-2, and IL-6 cytokines were quantified by ELISA. Inflammatory cells were counted using microscopy. Identical methodology was used with pulsed illumination. Average power (40 mW) and duty cycle were kept constant (80%) at five frequencies (5, 25, 50, 100, and 200 Hz). For continuous irradiation, treatment effects occurred for all doses, with a reduction of TNF-α, IL-1β, and IL-6 cytokines and inflammatory cells. Continuous irradiation at 830 nm was more effective, a result explained by the action spectrum of cytochrome c oxidase (CCO). Best results were obtained for 40 mW, with data suggesting a biphasic dose response. Pulsed wave irradiation was only effective for higher frequencies, a result that might be related to the rate constants of the CCO internal electron transfer process.

Hyperglycemia Inhibits Recovery From Disuse-Induced Skeletal Muscle Atrophy in Rats

The purpose of this study was to evaluate the effects of hyperglycemia on skeletal muscle recovery following disuse-induced muscle atrophy in rats. Wistar rats were grouped as streptozotocin-induced diabetic rats and non-diabetic rats. Both ankle joints of each rat were immobilized to induce atrophy of the gastrocnemius muscles. After two weeks of immobilization and an additional two weeks of recovery, tail blood and gastrocnemius muscles were isolated. Serial cross sections of muscles were stained for myosin ATPase (pH 4.5) and alkaline phosphatase activity. Serum insulin and muscle insulin-like growth factor-1 (IGF-1) levels were also measured. Serum insulin levels were significantly reduced in the diabetic rats compared to the non-diabetic controls. The diameters of type I, IIa, and IIb myofibers and capillary-to-myofiber ratio in the isolated muscle tissue were decreased after immobilization in both treatments. During the recovery period, these parameters were restored in the non-diabetic rats, but not in the diabetic rats. In addition, muscle IGF-1 levels after recovery increased significantly in the non-diabetic rats, but not in the diabetic rats. We conclude that decreased levels of insulin and IGF-1 and impairment of angiogenesis associated with diabetes might be partly responsible for the inhibition of regrowth in diabetic muscle.

The non-thermal effects of pulsed ultrasound irradiation on the development of disuse muscle atrophy in rat gastrocnemius muscle

This study examined the effects of therapeutic pulsed ultrasound (US) on the development of disuse muscle atrophy in rat gastrocnemius muscle. Male Wistar rats were randomly distributed into control, immobilization (Im), sham US, and US groups. In the Im, sham US and US groups, the bilateral ankle joints of each rat were immobilized in full plantar flexion with a plaster cast for a 4-wk period. The pulsed US (frequency, 1 MHz; intensity, 1.0 W/cm(2); pulsed mode 1:4; 15 min) was irradiated to the gastrocnemius muscle in the US group over a 4-wk immobilization period. The pulsed US irradiation delivered only non-thermal effects to the muscle. In conjunction with US irradiation, 5-bromo-2'-deoxyuridine (BrdU) was injected subcutaneously to label the nuclei of proliferating satellite cells 1 h before each pulsed US irradiation. Immobilization resulted in significant decreases in the mean diameters of type I, IIA and IIB muscle fibers of the gastrocnemius muscle in the Im, sham US and US groups compared with the control group. However, the degrees of muscle fiber atrophy for all types were significantly lower in the US group compared with the Im and sham US groups. Although the number of capillaries and the concentrations of insulin-like growth factor and basic fibroblast growth factor did not change in the muscle, the number of BrdU-positive nuclei in the muscle was significantly increased by pulsed US irradiation in the US group. The results of this study suggest that pulsed US irradiation inhibits the development of disuse muscle atrophy partly via activation of satellite cells.

Effect of IR laser on myoblasts: a proteomic study

Laser therapy is used in physical medicine and rehabilitation to accelerate muscle recovery and in sports medicine to prevent damages produced by metabolic disturbances and inflammatory reactions after heavy exercise. The aim of this research was to get insight into possible benefits deriving from the application of an advanced IR laser system to counteract deficits of muscle energy metabolism and stimulate the recovery of hypotrophic tissue. We studied the effect of IR laser treatment on proliferation, differentiation, cytoskeleton organization and global protein expression in C2C12 myoblasts. We found that laser treatment induced a decrease in the cell proliferation rate without affecting cell viability, while leading to cytoskeletal rearrangement and expression of the early differentiation marker MyoD. The differential proteome analysis revealed the up-regulation and/or modulation of many proteins known to be involved in cell cycle regulation, cytoskeleton organization and differentiation.

Low level laser therapy on experimental myopathy

PURPOSE

The aim of the present work was to study the effect of Helium-Neon (HeNe) and Gallium Arsenide (GaAs) laser upon nitric oxide (NO) plasma levels, an inflammatory biomarker associated with oxidative stress, in rats with experimental myopathy. These were evaluated through histological assessment.

MATERIALS AND METHODS

The groups studied were: (A) control (intact rats that received LLLT sham exposures), (B) rats with myopathy and sacrificed at 24 h later, (C) rats with myopathy and sacrificed 8 days later, (D) rats with myopathy and treated with HeNe laser, (E) rats with myopathy and treated with GaAs laser, (F) intact rats treated with HeNe laser and (G) intact rats treated with GaAs laser. Myopathy was induced by injecting 50μl of 1% carrageenan λ (type IV) in the left gastrocnemius muscle. Low Level Laser Therapy (LLLT) was applied with 9.5 J.cm(-2) daily for 10 consecutive days with each laser. The determination of the NO was made by spectrophotometry. The muscles were stained with Hematoxylin-Eosin and examined by optic microscopy. Quantitative variables were statistically analyzed by the Fisher test, and categorical by applying Pearson's Chi Squared test at p <0.05 for all cases.

RESULTS

In groups B and C, NO was significantly increased compared to groups A, D, E, F and G (p<0.05). In group C, the percentage of area with inflammatory infiltration was significantly increased compared to the other groups (p<0.001).

CONCLUSIONS

LLLT decreased plasma levels of NO in rats with experimental myopathies and significant muscle recovery.

ST36 laser acupuncture reduces pain-related behavior in rats: involvement of the opioidergic and serotonergic systems

Laser acupuncture is a modality of low-level light therapy used as an alternative to needling for the past three decades. Although it has proved effective for the treatment of various conditions, the mechanisms underlying its effects are not fully understood. To contribute to this understanding, this study was designed to (1) evaluate the antinociceptive effect of ST36 laser acupuncture (830 nm, 3 J/cm(2)) in rat models of acute nociception and (2) to investigate the opioidergic and serotonergic systems involvement in this effect. Our results demonstrate that ST36 laser acupuncture inhibited (36 ± 2 %) acetic acid-induced abdominal constrictions and both neurogenic (48 ± 7 %) and inflammatory (phase IIA 42 ± 8 % and phase IIB 83 ± 6 %) phases of formalin-induced nociceptive behavior. Moreover, the antinociceptive activity of laser irradiation in the acetic acid test was significantly reversed by preadministration of naloxone (1 mg/kg, nonselective opioid receptor antagonist), pindolol (1 mg/kg, subcutaneous; nonselective 5-HT 1A/B receptor antagonist), and ketanserin (1 mg/kg; selective 5-HT2A receptor antagonist) but not by ondansetron (1 mg/kg, selective 5-HT3 receptor antagonist). Taken together, our data demonstrate, for the first time, that (1) ST36 laser acupuncture elicited significant antinociceptive effect against acetic acid- and formalin-induced behavior in rats and that (2) this effect is mediated by activation of the opioidergic and serotonergic (5-HT1 and 5-HT2A receptors) systems.

Low-level laser therapy (808 nm) reduces inflammatory response and oxidative stress in rat tibialis anterior muscle after cryolesion

BACKGROUND AND OBJECTIVE

Muscle regeneration is a complex phenomenon, involving coordinated activation of several cellular responses. During this process, oxidative stress and consequent tissue damage occur with a severity that may depend on the intensity and duration of the inflammatory response. Among the therapeutic approaches to attenuate inflammation and increase tissue repair, low-level laser therapy (LLLT) may be a safe and effective clinical procedure. The aim of this study was to evaluate the effects of LLLT on oxidative/nitrative stress and inflammatory mediators produced during a cryolesion of the tibialis anterior (TA) muscle in rats.

MATERIAL AND METHODS

Sixty Wistar rats were randomly divided into three groups (n = 20): control (BC), injured TA muscle without LLLT (IC), injured TA muscle submitted to LLLT (IRI). The injured region was irradiated daily for 4 consecutive days, starting immediately after the lesion using a AlGaAs laser (continuous wave, 808 nm, tip area of 0.00785 cm(2) , power 30 mW, application time 47 seconds, fluence 180 J/cm(2) ; 3.8 mW/cm(2) ; and total energy 1.4 J). The animals were sacrificed on the fourth day after injury.

RESULTS

LLLT reduced oxidative and nitrative stress in injured muscle, decreased lipid peroxidation, nitrotyrosine formation and NO production, probably due to reduction in iNOS protein expression. Moreover, LLLT increased SOD gene expression, and decreased the inflammatory response as measured by gene expression of NF-kβ and COX-2 and by TNF-α and IL-1β concentration.

CONCLUSION

These results suggest that LLLT could be an effective therapeutic approach to modulate oxidative and nitrative stress and to reduce inflammation in injured muscle.

Shining light on nanotechnology to help repair and regeneration

Phototherapy can be used in two completely different but complementary therapeutic applications. While low level laser (or light) therapy (LLLT) uses red or near-infrared light alone to reduce inflammation, pain and stimulate tissue repair and regeneration, photodynamic therapy (PDT) uses the combination of light plus non-toxic dyes (called photosensitizers) to produce reactive oxygen species that can kill infectious microorganisms and cancer cells or destroy unwanted tissue (neo-vascularization in the choroid, atherosclerotic plaques in the arteries). The recent development of nanotechnology applied to medicine (nanomedicine) has opened a new front of advancement in the field of phototherapy and has provided hope for the development of nanoscale drug delivery platforms for effective killing of pathological cells and to promote repair and regeneration. Despite the well-known beneficial effects of phototherapy and nanomaterials in producing the killing of unwanted cells and promoting repair and regeneration, there are few reports that combine all three elements i.e. phototherapy, nanotechnology and, tissue repair and regeneration. However, these areas in all possible binary combinations have been addressed by many workers. The present review aims at highlighting the combined multi-model applications of phototherapy, nanotechnology and, reparative and regeneration medicine and outlines current strategies, future applications and limitations of nanoscale-assisted phototherapy for the management of cancers, microbial infections and other diseases, and to promote tissue repair and regeneration.

Low-level laser therapy (808 nm) contributes to muscle regeneration and prevents fibrosis in rat tibialis anterior muscle after cryolesion

Muscle regeneration is a complex phenomenon, involving replacement of damaged fibers by new muscle fibers. During this process, there is a tendency to form scar tissue or fibrosis by deposition of collagen that could be detrimental to muscle function. New therapies that could regulate fibrosis and favor muscle regeneration would be important for physical therapy. Low-level laser therapy (LLLT) has been studied for clinical treatment of skeletal muscle injuries and disorders, even though the molecular and cellular mechanisms have not yet been clarified. The aim of this study was to evaluate the effects of LLLT on molecular markers involved in muscle fibrosis and regeneration after cryolesion of the tibialis anterior (TA) muscle in rats. Sixty Wistar rats were randomly divided into three groups: control, injured TA muscle without LLLT, injured TA muscle treated with LLLT. The injured region was irradiated daily for four consecutive days, starting immediately after the lesion using an AlGaAs laser (808 nm, 30 mW, 180 J/cm(2); 3.8 W/cm(2), 1.4 J). The animals were sacrificed on the fourth day after injury. LLLT significantly reduced the lesion percentage area in the injured muscle (p<0.05), increased mRNA levels of the transcription factors MyoD and myogenin (p<0.01) and the pro-angiogenic vascular endothelial growth factor (p<0.01). Moreover, LLLT decreased the expression of the profibrotic transforming growth factor TGF-β mRNA (p<0.01) and reduced type I collagen deposition (p<0.01). These results suggest that LLLT could be an effective therapeutic approach for promoting skeletal muscle regeneration while preventing tissue fibrosis after muscle injury.

Satellite cell depletion does not inhibit adult skeletal muscle regrowth following unloading-induced atrophy

Resident muscle stem cells, known as satellite cells, are thought to be the main mediators of skeletal muscle plasticity. Satellite cells are activated, replicate, and fuse into existing muscle fibers in response to both muscle injury and mechanical load. It is generally well-accepted that satellite cells participate in postnatal growth, hypertrophy, and muscle regeneration following injury; however, their role in muscle regrowth following an atrophic stimulus remains equivocal. The current study employed a genetic mouse model (Pax7-DTA) that allowed for the effective depletion of >90% of satellite cells in adult muscle upon the administration of tamoxifen. Vehicle and tamoxifen-treated young adult female mice were either hindlimb suspended for 14 days to induce muscle atrophy or hindlimb suspended for 14 days followed by 14 days of reloading to allow regrowth, or they remained ambulatory for the duration of the experimental protocol. Additionally, 5-bromo-2'-deoxyuridine (BrdU) was added to the drinking water to track cell proliferation. Soleus muscle atrophy, as measured by whole muscle wet weight, fiber cross-sectional area, and single-fiber width, occurred in response to suspension and did not differ between satellite cell-depleted and control muscles. Furthermore, the depletion of satellite cells did not attenuate muscle mass or force recovery during the 14-day reloading period, suggesting that satellite cells are not required for muscle regrowth. Myonuclear number was not altered during either the suspension or the reloading period in soleus muscle fibers from vehicle-treated or satellite cell-depleted animals. Thus, myonuclear domain size was reduced following suspension due to decreased cytoplasmic volume and was completely restored following reloading, independent of the presence of satellite cells. These results provide convincing evidence that satellite cells are not required for muscle regrowth following atrophy and that, instead, the myonuclear domain size changes as myofibers adapt.

Low-level laser (light) therapy (LLLT) on muscle tissue: performance, fatigue and repair benefited by the power of light

The use of low level laser (light) therapy (LLLT) has recently expanded to cover areas of medicine that were not previously thought of as the usual applications such as wound healing and inflammatory orthopedic conditions. One of these novel application areas is LLLT for muscle fatigue and muscle injury. Since it is becoming agreed that mitochondria are the principal photoacceptors present inside cells, and it is known that muscle cells are exceptionally rich in mitochondria, this suggests that LLLT should be highly beneficial in muscle injuries. The ability of LLLT to stimulate stem cells and progenitor cells means that muscle satellite cells may respond well to LLLT and help muscle repair. Furthermore the ability of LLLT to reduce inflammation and lessen oxidative stress is also beneficial in cases of muscle fatigue and injury. This review covers the literature relating to LLLT and muscles in both preclinical animal experiments and human clinical studies. Athletes, people with injured muscles, and patients with Duchenne muscular dystrophy may all benefit.

Low intensity laser therapy accelerates muscle regeneration in aged rats

BACKGROUND

Elderly people suffer from skeletal muscle disorders that undermine their daily activity and quality of life; some of these problems can be listed as but not limited to: sarcopenia, changes in central and peripheral nervous system, blood hypoperfusion, regenerative changes contributing to atrophy, and muscle weakness. Determination, proliferation and differentiation of satellite cells in the regenerative process are regulated by specific transcription factors, known as myogenic regulatory factors (MRFs). In the elderly, the activation of MRFs is inefficient which hampers the regenerative process. Recent studies found that low intensity laser therapy (LILT) has a stimulatory effect in the muscle regeneration process. However, the effects of this therapy when associated with aging are still unknown.

OBJECTIVE

This study aimed to evaluate the effects of LILT (λ=830 nm) on the tibialis anterior (TA) muscle of aged rats.

SUBJECTS AND METHODS

The total of 56 male Wistar rats formed two population sets: old and young, with 28 animals in each set. Each of these sets were randomly divided into four groups of young rats (3 months of age) with n=7 per group and four groups of aged rats (10 months of age) with n=7 per group. These groups were submitted to cryoinjury + laser irradiation, cryoinjury only, laser irradiation only and the control group (no cryoinjury/no laser irradiation). The laser treatment was performed for 5 consecutive days. The first laser application was done 24 h after the injury (on day 2) and on the seventh day, the TA muscle was dissected and removed under anesthesia. After this the animals were euthanized. Histological analyses with toluidine blue as well as hematoxylin-eosin staining (for counting the blood capillaries) were performed for the lesion areas. In addition, MyoD and VEGF mRNA was assessed by quantitative polymerase chain reaction.

RESULTS

The results showed significant elevation (p<0.05) in MyoD and VEGF genes expression levels. Moreover, capillary blood count was more prominent in elderly rats in laser irradiated groups when compared to young animals.

CONCLUSION

In conclusion, LILT increased the maturation of satellite cells into myoblasts and myotubes, enhancing the regenerative process of aged rats irradiated with laser.