Comparative effects of low-level laser therapy pre- and post-injury on mRNA expression of MyoD,myogenin, and IL-6 during the skeletal muscle repair

This study analyzed the effect of pre-injury and post-injury irradiation with low-level laser therapy (LLLT) on the mRNA expression of myogenic regulatory factors and interleukin 6 (IL-6) during the skeletal muscle repair. Male rats were divided into six groups: control group, sham group, LLLT group, injury group; pre-injury LLLT group, and post-injury LLLT group. LLLT was performed with a diode laser (wavelength 780 nm; output power 40 mW’ and total energy 3.2 J). Cryoinjury was induced by two applications of a metal probe cooled in liquid nitrogen directly onto the belly of the tibialis anterior (TA) muscle. After euthanasia, the TA muscle was removed for the isolation of total RNA and analysis of MyoD, myogenin, and IL-6 using real-time quantitative PCR. Significant increases were found in the expression of MyoD mRNA at 3 and 7 days as well as the expression of myogenin mRNA at 14 days in the post-injury LLLT group in comparison to injury group. A significant reduction was found in the expression of IL-6 mRNA at 3 and 7 days in the pre-injury LLLT and post-injury LLLT groups. A significant increase in IL-6 mRNA was found at 14 days in the post-injury LLLT group in comparison to the injury group. LLLT administered following muscle injury modulates the mRNA expression of MyoD and myogenin. Moreover, the both forms of LLLT administration were able to modulate the mRNA expression of IL-6 during the muscle repair process.     

Effect of laser therapy on skeletal muscle repair process in diabetic rats

Skeletal muscle myopathy is a common source of disability in diabetic patients. This study evaluated whether low-level laser therapy (LLLT) influences the healing morphology of injured skeletal muscle. Sixty-five male Wistar rats were divided as follows: (1) sham; (2) control; (3) diabetic; (4) diabetic sham; (5) nondiabetic cryoinjured submitted to LLLT (LLLT); (6) diabetic cryoinjured submitted to LLLT (D-LLLT); and (7) diabetic cryoinjured non-treated (D). Diabetes was induced with streptozotocin. Anterior tibialis muscle was cryoinjured and received LLLT daily (780 nm, 5 J/cm², 10 s per point; 0.2 J; total treatment, 1.6 J). Euthanasia occurred on day 1 in groups 1, 2, 3, and 4 and on days 1, 7, and 14 in groups 5, 6, and 7. Muscle samples were processed for H&E and Picrosirius Red and photographed. Leukocytes, myonecrosis, fibrosis, and immature fibers were manually quantified using the ImageJ software. On day 1, all cryoinjured groups were in the inflammatory phase. The D group exhibited more myonecrosis than LLLT group (p?<?0.05). On day 14, the LLLT group was in the remodeling phase; the D group was still in the proliferative phase, with fibrosis, chronic inflammation, and granulation tissue; and the D-LLLT group was in an intermediary state in relation to the two previous groups. Under polarized light, on day 14, the LLLT and D-LLLT groups had organized collagen bundles in the perimysium, whereas the diabetic groups exhibited fibrosis. LLLT can have a positive effect on the morphology of skeletal muscle during the tissue repair process by enhancing the reorganization of myofibers and the perimysium, reducing fibrosis.     

Effect of low-level laser therapy on the fracture healing process

Low-level laser therapy (LLLT) is a biophysical form of intervention in the fracture-repair process, which, through several mechanisms, accelerates the healing of fractures and enhances callus formation. The effect of laser on fracture healing is controversial. Some authors affirm that LLLT can accelerate bone formation by increasing osteoblastic activity. The objective of our study was to evaluate the effect of laser therapy on fracture healing. Thirty rabbits were subjected to tibial bone open osteotomies that were stabilized with external fixators. The animals were divided into two study groups: laser group and control group. Callus development and bone mineral density were quantitatively evaluated by CT; the animals were then killed and the fractures were assessed for biomechanical properties. The results demonstrated that the increasing rate of bone mineral density was higher in the laser (L) group than in the control (C) group. CT at 5 weeks revealed a mean callus density of 297 Hounsfield units (HU) for the control group and 691 HU for the L group, which was statistically significant (P?=?0.001). In the L group, the mean recorded fracture tension was 190.5 N and 359.3 N for healed and intact bones, respectively, which was statistically significant (P?<?0.001). The result of the study showed that the use of laser could enhance callus development in the early stage of the healing process, with doubtful improvement in biomechanical properties of the healing bone; therefore, laser therapy may be recommended as an additional treatment in non-union fractures in humans.     

Phototherapy with low-level laser affects the remodeling of types I and III collagen in skeletal muscle repair

The purpose of this article was to analyze the photobiomodulator role of low-level laser therapy (LLLT) on the skeletal muscle remodeling following cryoinjury in rats, focusing the types I and III collagen proteins. Laser phototherapy has been employed to stimulate repair in different tissues. However, its role in skeletal muscle remodeling is not yet well clarified, especially its effect on the collagen component of the extracellular matrix. Fifty adult Wistar rats were divided into four groups: control, sham, cryoinjury, and laser-treated cryoinjury. Laser irradiation was performed three times a week on the injured region using the InGaAlP (indium-gallium-aluminum-phosphorous) laser (660 nm; beam spot of 0.04 cm², output power of 20 mW, power density of 0.5 mW/cm², energy density of 5 J/cm², 10-s exposure time, with a total energy dose of 0.2 J). Five animals were killed after short-term (days 1 and 7) and long-term (14 and 21) durations following injury. The muscles were processed and submitted to hematoxylin and eosin (H&E) and immunohistochemical staining. The histological slices were analyzed qualitatively, semi-quantitatively, and quantitatively. The data were submitted to statistical analysis using the Kruskal-Wallis test. The qualitative analysis of morphological aspects revealed that the muscle repair were very similar in cryoinjury and laser groups on days 1, 14 and 21. However, at 7 days, differences could be observed because there was a reduction in myonecrosis associated to formation of new vessels (angiogenesis) in the laser-treated group. The analysis of the distribution of types I and III collagen, on day 7, revealed a significant increase in the depositing of these proteins in the laser-treated group when compared to the cryoinjury group. InGaAlP diode laser within the power parameters and conditions tested had a biostimulatory effect at the regenerative and fibrotic phases of the skeletal muscle repairs, by promoting angiogenesis, reducing myonecrosis, and inducing types I and III collagen synthesis, following cryoinjury in rat.     

Infrared low-level diode laser on inflammatory process modulation in mice: pro- and anti-inflammatory cytokines

To evaluate the modulation of proinflammatory (interleukin-6, IL-6; tumor necrosis factor-α, TNF-α; and interferon-γ, IFN-γ) and anti-inflammatory cytokines (transforming growth factor-β1, TGF-β1) in the inflammation processes in vivo with low-level laser action, 50 isogenic mice were randomly distributed into three groups: control (no surgical procedure, n?=?10), sham (surgical procedure with three standard cutaneous incisions, followed by an abdominal muscle incision and suture, n?=?20), and laser (same procedure followed by laser exposure, n?=?20). The sham group was divided into three subgroups: sham I (euthanasia and evaluation, 36 h after surgical procedure), sham II (euthanasia and evaluation, 60 h after surgical procedure), and sham III (euthanasia and evaluation, 84 h after surgical procedure). The laser group was also divided in three subgroups: laser I (a single laser session, 12 h after surgery), laser II (two laser sessions, 12 and 36 h after surgery), and laser III (three laser sessions, 12, 36, and 60 h after surgery). All animals in the laser groups received three points per session of continuous infrared laser (wavelength of 780 nm, power of 20 mW, fluency of 10 J/cm², exposure time of 20 s per point, and energy of 0.4 J). After euthanasia, spleen mononuclear cells were isolated and cultured for 48 h. Concentrations of IL-6, TNF-α, IFN-γ, and TGF-β1 were obtained by enzyme-linked immunosorbent assay method. There was a significant difference between the IL-6 and TNF-α concentrations in the 60-and 84-h evaluations when the laser and sham groups were compared to the control group (p?<?0.05), except for laser II in the TNF-α analysis (p?>?0.05). The IFN-γ concentration analysis showed a significant difference only in sham II when compared to the control group (p?<?0.05). Thus, there was a modulatory effect of TNF-α and IFN-γ in the laser group, particularly in the 60-h postoperative evaluation. There was no significant difference between the laser, sham, and control groups for TGF-β1 analysis (p?>?0.05). The low-level laser application decreased the TNF-α and IFN-γ release in vivo of spleen mononuclear cells in mice, especially after two exposure sessions. However, there was no modulation of the IL-6 and TGF-β1 release.     

Effect of low-level laser therapy on repair of the bone compromised by radiotherapy

Radiotherapy (RDT) is commonly used for cancer treatment, but high doses of ionizing radiation can directly affect healthy tissues. Positive biological effects of low-level laser therapy (LLLT) on bone repair have been demonstrated; however, this effect on surgical defects of bone previously compromised by radiotherapy has not been evaluated. The aim of this study was to investigate the influence of LLLT (λ?=?830 nm) in femur repair after ionizing radiation. Twenty Wistar rats were divided into four groups: control group (GC, n?=?5) creation of bone defects (BDs) only; laser group (GL), with BD and LLLT (n?=?5); radiotherapy group (GR), submitted to RDT and BD (n?=?5); and radiotherapy and laser group (GRL), submitted to RDT, BD, and LLLT (n?=?5). GL and GRL received punctual laser application (DE?=?210 J/cm², P?=?50 mW, t?=?120 s, and beam diameter of 0.04 cm²) immediately after surgery, with 48-h interval during 7 days. Animals were euthanized at 7 days after surgery, and bone sections were evaluated morphometrically with conventional microscopy. Bone repair was only observed in nonirradiated bone, with significant improvement in GL in comparison to GC. GR and GRL did not present any bone neoformation. The result demonstrated a positive local biostimulative effect of LLLT in normal bone. However, LLLT was not able to revert the bone metabolic damage due to ionizing radiation.     

Effect of low-level laser therapy on bone repair: histological study in rats

BACKGROUND AND OBJECTIVES: Bone remodeling is characterized as a cyclic and lengthy process. It is currently accepted that not only this dynamics is triggered by a biological process, but also biochemical, electrical, and mechanical stimuli are key factors for the maintenance of bone tissue. The hypothesis that low-level laser therapy (LLLT) may favor bone repair has been suggested. The purpose of this study was to evaluate the bone repair in defects created in rat lower jaws after stimulation with infrared LLLT directly on the injured tissue. STUDY DESIGN/MATERIALS AND METHODS: Bone defects were prepared on the mandibles of 30 Holtzman rats allocated in two groups (n = 15), which were divided in three evaluation period (15, 45, and 60 days), with five animals each. control group-no treatment of the defect; laser group-single laser irradiation with a GaAlAs semiconductor diode laser device (lambda = 780 nm; P = 35 mW; t = 40 s; Theta = 1.0 mm; D = 178 J/cm(2); E = 1.4 J) directly on the defect area. The rats were sacrificed at the pre-established periods and the mandibles were removed and processed for staining with hematoxylin and eosin, Masson's Trichrome and picrosirius techniques. RESULTS: The histological results showed bone formation in both groups. However, the laser group exhibited an advanced tissue response compared to the control group, abbreviating the initial inflammatory reaction and promoting rapid new bone matrix formation at 15 and 45 days (P<0.05). On the other hand, there were no significant differences between the groups at 60 days. CONCLUSION: The use of infrared LLLT directly to the injured tissue showed a biostimulating effect on bone remodeling by stimulating the modulation of the initial inflammatory response and anticipating the resolution to normal conditions at the earlier periods. However, there were no differences between the groups at 60 days.     

The effects of 780-nm low-level laser therapy on muscle healing process after cryolesion

The objective of this study was to assess the effects of 780-nm low-level laser therapy at different periods of 7, 14 and 21 days after cryolesion, including the dose (10 or 50 J/cm²), to promote a better muscle repair evidenced by histopathological and immunohistochemical analyses. Fifty-four male rats were divided into three groups: injured control group (CG)—injured animals without any treatment; injured 780-nm laser-treated group, at 10 J/cm² (G10); and injured 780-nm laser-treated group, at 50 J/cm² (G50). Each group was divided into three subgroups (n?=?6): 7, 14 and 21 days post-injury. Histopathological findings revealed better organised muscle fibres in the G10 and G50 during the periods of 7 and 14 days compared to the CG. The G10 and G50 during the 7 days showed a significant reduction (p?<?0.05) of lesion area compared to the CG, without differences between groups treated for 14 and 21 days. The G10 showed an increase of the amount of vessels after 14 days compared to the G50, but not in relation to controls. With regard to the immunohistochemical analyses of the MyoD factor, the G10 and G50 during the 7 days showed higher concentrations of immunomarkers than controls. Myogenin immunomarkers were similarly observed at days 7 and 14 in all the three groups analysed, whereas immunomarkers were found in none of the groups after 21 days of laser therapy. The results showed that laser, regardless the applied dose, has positive effects on muscle repair.     

Effect of low-level laser therapy on angiogenesis and matrix metalloproteinase-2 immunoexpression in wound repair

Low-level laser therapy (LLLT) induces anti-inflammatory and angiogenic activities in wound healing. However, the mechanism of action and optimal parameters require further clarification. In this study, we investigated the effects of LLLT on wound healing matrix metalloproteinase (MMP)-2 immunoexpression and angiogenic processes. Twenty female Wistar rats were randomly divided into four groups (n?=?5) according to the treatments as follows. CG7 and CG14 were control groups at days 7 and 14, respectively, which received physiological saline (0.9 % NaCl daily). LG7 and LG14 were laser therapy groups at days 7 and 14, respectively, which received two (LG7) or four (LG14) LLLT applications (40 mW; 660 nm; 4 J/cm²). A dorsal skin sample in the wound area (measuring 2 cm²) was removed after the experimental period, and then the animals were euthanized. The specimens were processed for qualitative and quantitative histological analyses and measurement of MMP-2 expression in the dermis and epidermis. A persistent crust and moderate number of inflammatory cells were found in CG7 and CG14 groups. In the LG14 group, wounds demonstrated complete re-epithelization at the remodeling phase. Angiogenesis and MMP-2 expression were higher in LLLT-treated groups, particularly the LG14 group, which correlated according to the Spearman correlation test. LLLT improves wound healing by enhancing neocollagenesis, increasing the amount of new vessels formed in the tissue (neoangiogenesis), and modulating MMP-2 expression. Epidermal overexpression of MMP-2 was correlated to angiogenic processes.     

Effect of low-intensity laser irradiation on the process of bone repair

The effect of low-intensity laser (GaAsAl) irradiation on bone repair in the femurs of mice was investigated. An experimental model of hole injury with surgery drills was used in 20 mouse femurs followed by a study of the effect of low-energy laser irradiation on bone repair. The experimental model was divided into two groups. The first (10 left femurs) received laser irradiation immediately after injury and was followed for different time intervals (24, 48, and 72 h). The right femurs (control group) underwent hole injury but no laser irradiation. The rats were sacrificed after 14 days and the results were analyzed using a quantitative histometrical method. The Mann-Whitney test was used to perform the statistical analysis. Histometrical analysis revealed a more rapid accumulation of reparative new bone in the hole injury of the laser-irradiated legs. We conclude that GaAsAl laser irradiation after injury was effective on bone repair when compared to results in the control group.     

Evaluation of scars in children after treatment with low-level laser

Burn scars are known for their tendency to worsen with hypertrophy and contracture, causing esthetic and functional problems. The objective is to analyze the effectiveness of low-level laser therapy on post-burn hypertrophic scar tissue in children. A randomized controlled study included 15 children, ranging from 2 to 10 years of age, presented with post-burn hypertrophic scars. They received He-Ne laser and topical treatment. Each scar was divided into two halves. One half was treated with laser therapy and topical treatment (study area), and the other half was treated with topical treatment only (control area). The children were evaluated before, and after 3 months of the study by Vancouver Scar Scale (VSS), ultrasonography, and laser Doppler perfusion imaging. Significant improvement was reported in the studied area, compared to the control area for patients with P values (P =?0.003) and (P =?0.005), for VSS and U/S scores, respectively. No differences were detected for blood perfusion of the scar between both areas (P?=?0.73). In addition, no adverse effects were reported. Photobiomodulation (PBM) is an efficient and safe therapeutic modality for post-burn hypertrophic scars in children, with no side effects, and should be considered a part of combination therapy for better results.     

Effects of the combination of low-level laser therapy and anionic polymer membranes on bone repair

Lasers in Medical Science - In view of the limitations of bone reconstruction surgeries using autologous grafts as a gold standard, tissue engineering is emerging as an alternative, which permits...     

Effect of the transdermal low-level laser therapy on endothelial function

The effect of low-level laser therapy (LLLT) on the cardiovascular system is not fully established. Since the endothelium is an important endocrine element, establishing the mechanisms of LLLT action is an important issue.The aim of the study was to evaluate the effect of transdermal LLLT on endothelial function.In this study, healthy volunteers (n?=?40, age?=?20–40 years) were enrolled. N?=?30 (14 female, 16 male, mean age 30?±?5 years) constituted the laser-irradiated group (LG). The remaining 10 subjects (6 women, 4 men, mean age 28?±?5 years) constituted the control group (CG). Participants were subjected to LLLT once a day for three consecutive days. Blood for biochemical assessments was drawn before the first irradiation and 24 h after the last session. In the LG, transdermal illumination of radial artery was conducted (a semiconductor laser λ?=?808 nm, irradiation 50 mW, energy density 1.6 W/cm² and a dose 20 J/day, a total dose of 60 J). Biochemical parameters (reflecting angiogenesis: vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), angiostatin; antioxidative status: glutathione (GSH) and the nitric oxide metabolic pathway: symmetric dimethylarginine (SDMA), asymmetric dimethylarginine (ADMA) and l-arginine) were assessed. In the LG, a significant increase in GSH levels and considerable decrease in angiostatin concentration following the LLLT were observed. No significant differences in levels of the VEGF, FGF, SDMA, ADMA were observed.LLLT modifies vascular endothelial function by increasing its antioxidant and angiogenic potential. We found no significant differences in levels of the nitric oxide pathway metabolites within 24 h following the LLLT irradiation.     

Effect of low-level laser therapy on allergic asthma in rats

Asthma is a complex chronic inflammatory disease of the airways that involves the activation of many inflammatory and other types of cells. We investigated the effect of low-level laser therapy (LLLT) on allergic asthma in rats and compared its effect with that of the glucocorticoid budesonide. Asthma was induced by challenge and repeated exposure to ovalbumin. Asthmatic rats were then treated with LLLT or budesonide suspension. LLLT at 8 J/cm² once daily for 21 days could relieve pathological damage and airway inflammation in asthmatic rats. LLLT could decrease the total numbers of cells and eosinophils in bronchoalveolar lavage fluid. LLLT could reduce levels of IL-4 and increase IFN-γ levels in bronchoalveolar lavage fluid and serum, meanwhile reduce serum IgE levels. Flow cytometry assay showed that LLLT can regulate the Th1/Th2 imbalance of asthmatic rats. LLLT had a similar effect to that of budesonide. These findings suggest that the mechanism of LLLT treatment of asthma is by adjustment of Th1/Th2 imbalance. Thus, LLLT could take over some of the effects of budesonide for the treatment of asthma, thereby reducing some of the side effects of budesonide.