Evaluation of the osteogenic effect of low-level laser therapy (808 nm and 660 nm) on bone defects induced in the femurs of female rats submitted to ovariectomy

Comparative Investigation of Photobiomodulation in Diabetes-Impaired Alveolar Bone Healing: A Histomorphometrical and Molecular Study

Objective: Diabetes mellitus is increasing worldwide. Photobiomodulation (PBM) is proposed as a therapeutic method in various medical concerns. This study aimed to compare the effects of PBM at the wavelengths of 660, 808, or 660 + 808 nm on alveolar bone healing in diabetic rats. Methods: Bilateral maxillary first molars were extracted from diabetic Wistar rats (n = 36). Right-sided sockets were treated by an In-Ga-Al-P laser at 660 nm (7.2 J/cm2, 24 s; DM660), Ga-Al-As laser at 808 nm (7 J/cm2, 14 s; DM808), or a combination of these two sets (DM-dual) (n = 12). Left sides served as controls. On days 7 or 14, specimens were assigned for histomorphometric or real-time PCR analysis of runt-related transcription factor 2, osteocalcin, collagen I, and vascular endothelial growth factor expression. Results: Irradiated sockets of groups DM-808 and DM-dual showed a significant increase in bone tissue and blood vessel establishment as compared to DM-660. Further, group DM-dual exhibited the least amount of fibrotic tissue as compared to the other groups. Conclusions: Within our study limits, the present experiment suggested PBM at 808 nm, alone or combined with 660 nm irradiation, could promote alveolar bone healing, along with minimal fibrosis induction, in diabetic rats.

The role of photobiomodulation in accelerating bone repair

Bone repair is faced with obstacles such as slow repair rates and limited bone regeneration capacity. Delayed healing even nonunion could occur in bone defects, influencing the life quality of patients severely. Photobiomodulation (PBM) utilizes different light sources to derive beneficial therapeutic effects with the advantage of being non-invasive and painless, providing a promising strategy for accelerating bone repair. In this review, we summarize the parameters, mechanisms, and effects of PBM regulating bone repair, and further conclude the current clinical application of PBM devices in bone repair. The wavelength of 635-980 nm, the output power of 40-100 mW, and the energy density of less than 100 J/cm2 are the most commonly used parameters. New technologies, including needle systems and biocompatible and implantable optical fibers, offer references to realize an efficient and safe strategy for bone repair. Further research is required to establish the reliability of outcomes from in vivo and in vitro studies and to standardize clinical trial protocols.

Effect of photobiomodulation therapy with different wavelengths on bone mineral density in osteoporotic rats

Osteoporosis is associated with severe pain, bone deformity, fracture, and bone loss. It is important to find strategies to prevent bone resorption and treat osteoporosis. This study sought to assess the effect of photobiomodulation therapy (PBMT) with different wavelengths on bone mineral density (BMD) in osteoporotic rats. This animal study evaluated 63 adult female rats. The rats underwent ovariectomy to induce osteoporosis. Ovariectomized rats were randomly divided into 9 groups of control (OC), treatment with zoledronic acid alone (0.02 mg/kg), and treatment with 660 nm, 810 nm, and 940 nm PBMT alone (3 times a week for 6 weeks, energy density of 4 J/cm2), and combined with zoledronic acid. The healthy control group (HC) only underwent sham surgery. The rats underwent cone-beam computed tomography (CBCT) 52 days after the first treatment session to measure their BMD according to the gray value (GV) of images. To assess the biomechanical properties of bone, the resected bones were subjected to 3-point bending test (3-PBT). The experimental groups had significant differences with the OC group regarding radiographic and biomechanical properties of bone (P < 0.05), indicating a healing course. No significant difference was noted between the experimental groups treated with different laser wavelengths and those treated with zoledronic acid (P > 0.05). In the condition of this study, it was found that PBMT at a constant energy density of 4 J/cm2 with 660-, 810-, and 940-nm wavelengths is effective for enhancement of bone mineral density and biomechanical properties. No significant difference was noted between different wavelengths of diode laser regarding radiographic and biomechanical properties of bone.

Photobiomodulation effects in metalloproteinases expression in zymosan-induced arthritis

Matrix metalloproteinases (MMPs) play a crucial role in the degenerative course of rheumatic disorders. They are responsible for cartilage and other joint-associated tissues breakdown. Amid arthritis treatments, photobiostimulation (PBM), a non-thermal and non-invasive low-power laser application, appears to be an outstanding therapy alternative once it has succeeded in MMPs modulation. Thus, this study aimed to evaluate the PBM effects of low infrared laser (830 nm), testing two different energy densities (3 and 30 Jcm^-2) in MMP-2, MMP-9, MMP-13, and MMP-14 as well as the inhibitor TIMP-2 expressions using zymosan-induced arthritis model. C57BL/6 mice were distributed into four groups (n = 8): zymosan-induced arthritis without treatment; zymosan-induced arthritis and dexamethasone-treated; zymosan-induced arthritis and PBM at energy density of 3 Jcm^-2 treated; and zymosan-induced arthritis and PBM at energy density of 30 Jcm^-2 treated. MMPs and TIMP-2 mRNA relative levels by qRT-PCR and proteins expression by immunohistochemical and Western blotting techniques were performed after PBM treatment in the inflamed joint. Our results demonstrated PBM could modulate both mRNA relative levels and proteins expression of the MMP-2, -9, -13, -14, and TIMP-2 in joint tissues, decreasing MMP-9 protein expression and increasing TIMP-2 protein expression. PBM promotes a better arthritis prognostic, modulating metalloproteinase and its inhibitor, especially MMP-9 and TIMP-2 protein expression that is important inflammatory markers. These findings may also corroborate that PBM may regulate MMPs expression using different pathways.

The Effects of Photobiomodulation on MC3T3-E1 Cells via 630 nm and 810 nm Light-Emitting Diode

BACKGROUND Photobiomodulation (PBM) has been explored as a promising therapeutic strategy to regulate bone cell growth; however, the effects of PBM on osteoblast cell lines remains poorly understood. In addition, as a light source of PBM, the light uniformity of light-emitting diode (LED) devices has not been given enough attention. MATERIAL AND METHODS Here, we sought to investigate the effects of PBM on MC3T3-E1 cells via 630 nm and 810 nm light from a newly designed LED with high uniformity of light. Cell proliferation, flow cytometric analysis, alkaline phosphatase (ALP) staining, ALP activity, Alizarin Red S staining, and quantitative real-time polymerase chain reaction (qRT-PCR) were carried out to assess treatment response. MC3T3-E1 cells were irradiated with LED devices (630±5 nm and 810±10 nm, continuous wave) for 200 seconds at a power density of 5 mW/cm² once daily. RESULTS Increases in cell proliferation and decreases in cell apoptosis were evident following irradiation. ALP staining intensity and activity were also significantly increased following irradiation. Level of mineralization was obviously enhanced in irradiated groups compared with non-irradiated controls. qRT-PCR also showed significant increases in mRNA expression of osteocalcin (OCN) and osteoprotegerin (OPG) in the irradiated groups. CONCLUSIONS Our results showed that LED PBM could promote the proliferation, ALP staining intensity and activity, level of mineralization, gene expression of OCN and OPG of MC3T3-E1 cells, with no significant difference between the 630 nm- and 810 nm-irradiated groups.

Enhancing osteoblast functions on biofilm-contaminated titanium alloy by concentration-dependent use of methylene blue-mediated antimicrobial photodynamic therapy

The concentration of methylene blue (MB) photosensitizer could affect the eradication efficacy of antimicrobial photodynamic therapy (aPDT) in the treatment of contaminated implants, which is linked to the osseointegration of the implant. We evaluated osteoblast functions on the contaminated SLA (sandblasting, large-grit and acid-etching) Ti alloy surfaces after the concentration-dependent use of MB-aPDT. Totally 1164 SLA discs were randomly distributed for the analyses of antibacterial efficacy and osteoblast functions. Gram-negative (Aggregatibacter actinomycetemcomitans; A. actinomycetemcomitans) or Gram-positive (Streptococcus mutans; S. mutans) adhered on disc samples was subjected to aPDT with different MB concentrations (200, 250, 300, 350, and 400 μg/mL) using 660 nm diode laser with maximum output 80 mW for 1 min irradiation (4.8 J/cm²). Bactericidal effect was examined by viability, morphology, and lipopolysaccharide (LPS) assays. The disinfected disc surfaces by MB-aPDT to support osteoblast-like MG63 attachment, proliferation, differentiation, and mineralization were assessed for the predetermined culture time intervals. The statistical differences between the means were performed using a one-way analysis of variance (ANOVA) with a post hoc Scheffe test. The results of the morphology observation and bacterial survival examination consistently indicated a remarkably lower quantity of bacterial colonies on biofilm-contaminated surfaces after the aPDT treatment with higher MB concentration. Similarly, the higher MB concentration in aPDT resulted in the lower LPS amounts remaining on the A. actinomycetemcomitans-contaminated surfaces. Intriguingly, the expression of osteoblast cultured on disinfected surfaces using aPDT with higher MB concentration was comparable to the control without contamination. Within the limits of this in vitro model, this formulation of 400 μg/mL MB used in aPDT may be not only the lethal concentration against the 2 bacteria-contaminated implants, but it could also enhance the osteoblast functions on the contaminated implants. Nevertheless, the efficacy in the clinical practice for peri-implantitis therapy remains to be studied.

Low-level laser therapy enhances the number of osteocytes in calvaria bone defects of ovariectomized rats

BACKGROUND

Osteoporosis can make bone repair difficult. Low-level laser therapy (LLLT) has been shown to be a promising tool for bone neoformation. This study aimed to analyze the effect of LLLT on calvaria bone defects of ovariectomized rats using stereology.

METHODS

Fifty-four Wistar rats were subjected to bilateral ovariectomy, and bone defects were created in calvaria after 150 days. The animals were divided into nine groups (n =  6 per group), and 24 hours after the bone defects were created they received 3, 6 or 12 sessions of LLLT at 0, 20 or 30 J/cm2, using a 780-nm low-intensity GaAlAs laser. One-way ANOVA followed by Tukey's post hoc test was used for data processing. A difference of P < 0.05 was considered statistically significant. The parameters evaluated were osteocyte density (Nv ost), total osteocyte number (Nto ost), trabecular surface density (Sv t), and trabecular surface area (Sa t).

RESULTS

Data obtained showed that Nto ost, Sv t, and Sa t in group G2 rats were significantly different from G1 (0 J/cm2) (P < 0.05). Compared to group G4, G5 presented higher values for the parameters Sv t and Sa t, and G6 presented significantly higher values for almost all the analyzed parameters (Nv ost, Nto ost, Sv t, and Sa t) (P < 0.05). Compared to group G7, G8 showed a higher value only for the parameter Sa t, and G9 showed significantly higher values for parameters Nv ost, Nto ost, Sv t, and Sa t.

CONCLUSION

We conclude that LLLT stimulated bone neoformation and contributed to an increase in the total number of osteocytes, especially with a laser energy density of 30 J/cm2 given for 6 and 12 sessions.

Red (635 nm), Near-Infrared (808 nm) and Violet-Blue (405 nm) Photobiomodulation Potentiality on Human Osteoblasts and Mesenchymal Stromal Cells: A Morphological and Molecular In Vitro Study

Photobiomodulation (PBM) has been used for bone regenerative purposes in different fields of medicine and dentistry, but contradictory results demand a skeptical look for its potential benefits. This in vitro study compared PBM potentiality by red (635 ± 5 nm) or near-infrared (NIR, 808 ± 10 nm) diode lasers and violet-blue (405 ± 5 nm) light-emitting diode operating in a continuous wave with a 0.4 J/cm² energy density, on human osteoblast and mesenchymal stromal cell (hMSC) viability, proliferation, adhesion and osteogenic differentiation. PBM treatments did not alter viability (PI/Syto16 and MTS assays). Confocal immunofluorescence and RT-PCR analyses indicated that red PBM (i) on both cell types increased vinculin-rich clusters, osteogenic markers expression (Runx-2, alkaline phosphatase, osteopontin) and mineralized bone-like nodule structure deposition and (ii) on hMSCs induced stress fiber formation and upregulated the expression of proliferation marker Ki67. Interestingly, osteoblast responses to red light were mediated by Akt signaling activation, which seems to positively modulate reactive oxygen species levels. Violet-blue light-irradiated cells behaved essentially as untreated ones and NIR irradiated ones displayed modifications of cytoskeleton assembly, Runx-2 expression and mineralization pattern. Although within the limitations of an in vitro experimentation, this study may suggest PBM with 635 nm laser as potential effective option for promoting/improving bone regeneration.

Investigation of photobiomodulation potentiality by 635 and 809 nm lasers on human osteoblasts

Photobiomodulation (PBM) describes light-induced photochemical reactions achieved by the application of red or near infrared lasers/LED light with low energy densities. This noninvasive and painless method has been used in some clinical areas but controversial outcomes demand a skeptical look for its promising and potential effects. In this detailed in vitro study, the osteoblast cells were irradiated with 635 and 809 nm diode lasers at energy densities of 0.5, 1, and 2 J/cm². Cell viability, proliferation, bone formation, and osteoblast differentiation were evaluated by methylthiazole tetrazolium (MTT) assay, Alamar Blue assay, acridine orange/propidium iodide staining, alkaline phosphatase (ALP) activity, Alizarin red staining, and reverse-transcription polymerase chain reaction (RT-PCR) to test the expression of collagen type I, ALPL, and osteocalcin. The results indicate that studied energy doses have a transient effect (48 h after laser irradiation) on the osteoblast viability and proliferation. Similarly, laser irradiation did not appear to have any effect on ALP activity. These results were confirmed by RT-PCR analysis of osteoblast markers. This study suggests that several irradiation parameters and variations in the methods should be clearly established in the laboratory before laser treatment becomes a postulated application for bone tissue regeneration in clinical level.

Evaluation of the effects of pulsed wave LLLT on tibial diaphysis in two rat models of experimental osteoporosis, as examined by stereological and real-time PCR gene expression analyses

Osteoporosis (OP) and osteoporotic fracture are major public health issues for society; the burden for the affected individual is also high. Previous studies have shown that pulsed wave low-level laser therapy (PW LLLT) has osteogenic effects. This study intended to evaluate the impacts of PW LLLT on the cortical bone of osteoporotic rats' tibias in two experimental models, ovariectomized and dexamethasone-treated. We divided the rats into four ovariectomized induced OP (OVX-d) and four dexamethasone-treated (glucocorticoid-induced OP, GIOP) groups. A healthy (H) group of rats was considered for baseline evaluations. At 14 weeks following ovariectomy, we subdivided the OVX-d rats into the following groups: (i) control which had OP, (ii) OVX-d rats treated with alendronate (1 mg/kg), (iii) OVX-d rats treated with LLLT, and (iv) OVX-d rats treated with alendronate and PW LLLT. The remaining rats received dexamethasone over a 5-week period and were also subdivided into four groups: (i) control rats treated with intramuscular (i.m.) injections of distilled water (vehicle), (ii) rats treated with subcutaneous alendronate injections (1 mg/kg), (iii) laser-treated rats, and (iv) rats simultaneously treated with laser and alendronate. The rats received alendronate for 30 days and underwent PW LLLT (890 nm, 80 Hz, 0.972 J/cm(2)) three times per week during 8 weeks. Then, the right tibias were extracted and underwent a stereological analysis of histological parameters and real-time polymerase chain reaction (RT-PCR). A significant increase in cortical bone volume (mm(3)) existed in all study groups compared to the healthy rats. There were significant decreases in trabecular bone volume (mm(3)) in all study groups compared to the group of healthy rats. The control rats with OP and rats from the vehicle group showed significantly increased osteoclast numbers compared to most other groups. Alendronate significantly decreased osteoclast numbers in osteoporotic rats. Concurrent treatments (compounded by PW LLLT and alendronate) produce the same effect on osteoporotic bone.

Titanium scaffold osteogenesis in healthy and osteoporotic rats is improved by the use of low-level laser therapy (GaAlAs)

The present study aimed to assess the effects of low-level laser therapy (GaAlAs) on the bone repair process within titanium scaffolds in the femurs of healthy and osteoporotic rats. Fifty-six rats were divided into four groups: group Sh: SHAM animals that received scaffolds; group LSh: SHAM animals that received scaffolds and were subjected to laser therapy; group OV: ovarietomized (OVX) animals that received scaffolds; and group LOV: OVX animals that received scaffolds and were subjected to laser therapy. Thirty days following ovariectomy or sham surgery, scaffolds were implanted in the left femurs of all animals in the study. Immediately after opening the surgical site, the inner part of the surgical cavity was stimulated with low-level laser (GaAlAs). In addition to this procedure, the laser group was also subjected to sessions of low-level laser therapy (LLLT) at 48-h intervals, with the first session performed immediately after surgery. The rats were sacrificed at 2 and 6 weeks, time in which femur fragments were submitted for histological and histomorphometric examination, and skin tissue above the scaffold was submitted to histological analysis. At the end of the study, greater bone formation was observed in the animals submitted to LLLT. At 2 and 6 weeks, statistically significant differences were observed between LSh and Sh groups (p = 0.009 and 0.0001) and LOV and OV (p = 0.0001 and 0.0001), respectively. No statistical difference was observed when assessing the estrogen variable. On the basis of our methodology and results, we conclude that LLLT improves and accelerates bone repair within titanium scaffolds in both ovariectomized and healthy rats, when compared to animals not subjected to radiation.

Effect of Pulsed Wave Low-Level Laser Therapy on Tibial Complete Osteotomy Model of Fracture Healing With an Intramedullary Fixation

BACKGROUND

Fractures pose a major worldwide challenge to public health, causing tremendous disability for the society and families. According to recent studies, many in vivo and in vitro experiments have shown the positive effects of PW LLLT on osseous tissue.

OBJECTIVES

The aim of this study was to evaluate the outcome of infrared pulsed wave low-level laser therapy (PW LLLT) on the fracture healing process in a complete tibial osteotomy in a rat model, which was stabilized by an intramedullary pin.

MATERIALS AND METHODS

This experimental study was conducted at Shahid Beheshti University of Medical Sciences in Tehran, Iran. We performed complete tibial osteotomies in the right tibias for the population of 15 female rats. The rats were divided randomly into three different groups: I) Control rats with untreated bone defects; II) Rats irradiated by a 0.972 J/cm(2) PW LLLT; and III) Rats irradiated by a 1.5 J/cm(2) PW LLLT. The right tibias were collected six weeks following the surgery and a three-point bending test was performed to gather results. Immediately after biomechanical examination, the fractured bones were prepared for histological examinations. Slides were examined using stereological method.

RESULTS

PW LLLT significantly caused an increase in maximum force (N) of biomechanical repair properties for osteotomized tibias in the first and second laser groups (30.0 ± 15.9 and 32.4 ± 13.8 respectively) compared to the control group (8.6 ± 4.5) LSD test, P = 0.019, P = 0.011 respectively). There was a significant increase in the osteoblast count of the first and second laser groups (0.53 ± 0.06, 0.41 ± 0.06 respectively) compared to control group (0.31 ± 0.04) (LSD test, P = 0001, P = 0.007 respectively).

CONCLUSIONS

This study confirmed the efficacy of PW LLLT on biomechanical strength, trabecular bone volume, callus volume, and osteoblast number of repairing callus in a complete tibial osteotomy animal model at a relatively late stage of the bone healing process.

Effects of low-intensity non-coherent light therapy on the inflammatory process in the calcaneal tendon of ovariectomized rats

The aim of this experimental study was to investigate the effects of low-intensity light-emitting diode (LED) phototherapy on the inflammatory process in the calcaneal tendon of ovariectomized rats (OVX) through the involvement of the inflammatory mediators interleukin (IL)-6, IL-10, and tumor necrosis factor-alpha (TNF-α). Thirty-five female Wistar rats were divided into 4 groups: 3 groups of OVX rats totaling 30 rats (untreated OVX rats [OVX injury group], treated OVX rats [OVX LED group], and control OVX rats; subgroups existed based on the sampling times, which were 3, 7, and 14 days) and 1 group of non-OVX rats (not OVX; n = 5). Tendon injury was induced by trauma using a 208-g mass placed at 20 cm from the right tendon of each animal with energy of 0.70 J. The animals were treated 12 h after tendonitis with LED therapy and every 48 h thereafter until euthanasia (at 3, 7, or 14 days). The tendons were dissected and stored in liquid nitrogen at -196 °C, thawed only at the time of immunoenzymatic testing (ELISA). Groups treated with LED showed a decrease in the number of pro-inflammatory cells, IL-6, and TNF-α (p <0.05), and an increase in IL-10 (p < 0.05) when compared to the not OVX group (p < 0.05). It was concluded that low-intensity LED treatment using the parameters and wavelength of 945 nm in the time periods studied reduced the release of IL-6 and TNF-α and increased the release of IL-10, thereby improving the inflammatory response in OVX rats.

Low-level laser therapy improves bone formation: stereology findings for osteoporosis in rat model

Low-level laser therapy (LLLT) benefits bone metabolism, but its use needs to be standardized. We evaluated the effects of LLLT on bone defects in calvaria of ovariectomized rats. Stereology was used to calculate tissue repair volume (V tr ), density of trabecular bone volume (Vv t ), total volume of newly formed trabecular bone (Vtot), and the area occupied by collagen fibers (A C ). Fifty-four Wistar rats were submitted to bilateral ovariectomy, and bone defects were created in calvaria after 150 days. The animals were divided into nine groups (n = 6), and 24 h after defects, the treatment started with a 780-nm low-intensity GaAlAs laser: G1, G2, and G3 received 3 sessions of 0, 20, and 30 J/cm(2) respectively; G4, G5, and G6 received 6 sessions of 0, 20, and 30 J/cm(2), respectively; and G7, G8, and G9 received 12 sessions of 0, 20, and 30 J/cm(2), respectively. A normal distribution was found for all of the data. The test used to verify the normality was the Kolmogorov-Smirnov (KS, p > 0.05). The one-way ANOVA followed by Tukey's post hoc test was used for data processing. A difference of p < 0.05 was considered statistically significant. Groups G2 and G1 showed significance for V tr , Vv t , Vtot, and (A C ). Results were significant for (Vv t ) and (Vtot) between G3 and G1. There were no significant results between G5 and G4 as well as between G8 and G7. Groups G6 and G4 results showed statistical difference for V tr , Vv t , Vtot, and (A C ). Groups G9 and G7 showed significance for V tr , Vv t , Vtot, and (A C ). In conclusion, there was new bone formation in the groups that received 20 and 30 J/cm(2) when compared to control groups, but over time, the dose of 30 J/cm(2) showed better stereological parameters when compared to 20 J/cm(2).

Effect of low-level laser therapy in an experimental model of osteoarthritis in rats evaluated through Raman spectroscopy

OBJECTIVE

This work aimed to investigate the biochemical changes associated with low-level laser therapy (LLLT) using 660 and 780 nm, on a well-established experimental model of osteoarthritis (OA) in the knees of rats with induced collagenase, using histomorphometry and Raman spectroscopy.

MATERIALS AND METHODS

Thirty-six Wistar rats were divided into four groups: control (GCON, n=9), collagenase without treatment (GCOL, n=9), collagenase with LLLT 660 nm treatment (G660, n=8), and collagenase with LLLT 780 nm treatment (G780, n=10). LLLT protocol was: 30 mW power output, 10 sec irradiation time, 0.04 cm(2) spot size, 0.3 J energy, 0.75 W/cm(2) irradiance, and 7.5 J/cm(2) fluence per session per day, during 14 days. Then, knees were withdrawn and submitted to histomorphometry and Raman spectroscopy analysis. Principal components analysis (PCA) and Mahalanobis distance were employed to characterize the spectral findings.

RESULTS

Histomorphometry revealed a significant increase in the amount of collagen III for the group irradiated with 660 nm. The Raman bands at 1247, 1273, and 1453 cm(-1) (from principal component score PC2), attributed to collagen type II, and 1460 cm(-1) (from PC3), attributed to collagen type III, suggested that the LLLT causes acceleration in cellular activity, especially on the cells that repair cartilage, accelerating the breakdown of cartilage destroyed by collagenase and stimulating the fibroblast to synthesize repairing collagen III.

CONCLUSIONS

LLLT accelerated the initial breakdown of cartilage destroyed by collagenase and stimulated the fibroblast to synthesize the repairing collagen III, suggesting a beneficial effect of LLLT on OA.

Low power laser stimulation of the bone consolidation in tibial fractures of rats: a radiologic and histopathological analysis

The objective of this study is to analyze the effectiveness of low power laser irradiation in the bone consolidation of tibial fractures in rats. An experimental, comparative, prospective study with control group was designed. Twenty Wistar rats were grouped into control (n = 10) and experimental groups (n = 10). A tibial fracture, with a mechanical drill, was inflicted in all rats. The experimental group received ten days of low power arsenide-gallium laser irradiation of 850 nm (KLD, Sao Paulo, Brasil)-100 mW, 8 J/cm(2), 64 s. Before and after the laser treatment, a radiologic analysis was carried out in both groups, in which the rats were graded from 0 to IV according the Montoya scale of bone consolidation. Also, we histopathologically analyzed the bone to estimate the proliferation of fibroblasts, bone matrix, and angiogénesis with a microscopy, which were graded as I (thin layer of fibroblasts and osteoid matrix), II (thick layer of fibroblasts and osteoid matrix), or III (thick layer of fibroblasts and osteoid matrix and new blood vessels). Radiologic data showed that the experimental group had a higher bone consolidation of Montoya scale after ten days of laser irradiation compared to control group (P < 0.004). Histopathologic data showed more fibroblasts and angiogenesis presence in the group receiving laser irradiation, compared to control group (P < .002). The low power laser radiation therapy may expedite the bone repair after tibial fractures in rats, according to radiologic and histopathologic analysis.

Effect of low-level laser therapy on metalloproteinase MMP-2 and MMP-9 production and percentage of collagen types I and III in a papain cartilage injury model

Osteoarthritis (OA) resulting from injury or disease is associated with increased levels of several matrix metalloproteinases (MMPs), which degrade all components of the complex extracellular matrix in the cartilage. The objective of this study is to investigate the effect of low-level laser therapy (LLLT) on papain-induced joint damage in rats by histopathology and analysis of metalloproteinase 2 and 9 production. Sixty male Wistar rats were randomly distributed into four groups of 15 animals: (1) non-injury negative control, (2) injury positive control, (3) treated with LLLT at 50 mW, and (4) treated with LLLT at 100 mW. OA was induced in animals using papain (4 % solution) followed by treatment with LLLT. After 7, 14, and 21 days, the animals were euthanized. The articular lavage was collected and centrifuged; then, the supernatant was stored prior to protein analysis by western blot. The material was stained with hematoxylin and eosin for histopathological analysis, and Picrosirius Red was used to estimate the percentage of collagen fibers. To determine normal distribution, ANOVA and Tukey's post hoc test were used for comparison between and within each group at each time period. All data are expressed as mean and standard deviation values, with the null hypothesis considered as p < 0.05. Both laser groups (50 and 100 mW) were effective in tissue repair, decreasing collagen type III expression and increasing type I expression in all experimental periods; however, LLLT at 50 mW reduced metalloproteinase 9 more than at 100 mW in 21 days. LLLT at 50 mW was more efficient in the modulation of matrix MMPs and tissue repair.

Low-level laser therapy in different stages of rheumatoid arthritis: a histological study

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease of unknown etiology. Treatment of RA is very complex, and in the past years, some studies have investigated the use of low-level laser therapy (LLLT) in treatment of RA. However, it remains unknown if LLLT can modulate early and late stages of RA. With this perspective in mind, we evaluated histological aspects of LLLT effects in different RA progression stages in the knee. It was performed a collagen-induced RA model, and 20 male Wistar rats were divided into 4 experimental groups: a non-injured and non-treated control group, a RA non-treated group, a group treated with LLLT (780 nm, 22 mW, 0.10 W/cm(2), spot area of 0.214 cm(2), 7.7 J/cm(2), 75 s, 1.65 J per point, continuous mode) from 12th hour after collagen-induced RA, and a group treated with LLLT from 7th day after RA induction with same LLLT parameters. LLLT treatments were performed once per day. All animals were sacrificed at the 14th day from RA induction and articular tissue was collected in order to perform histological analyses related to inflammatory process. We observed that LLLT both at early and late RA progression stages significantly improved mononuclear inflammatory cells, exudate protein, medullary hemorrhage, hyperemia, necrosis, distribution of fibrocartilage, and chondroblasts and osteoblasts compared to RA group (p < 0.05). We can conclude that LLLT is able to modulate inflammatory response both in early as well as in late progression stages of RA.