Low level laser therapy (830 nm) improves bone repair in osteoporotic rats: Similar outcomes at two different dosages

Abstract Background and objective The goal of this study was to investigate the effects of low level laser therapy (LLLT) in osteoporotic rats by means of subjective histopathological analysis, deposition of collagen at the site of fracture, biomechanical properties and immunohistochemistry for COX-2, Cbfa-1 and VEGF. Material and methods A total of 30 female Wistar rats (12 weeks-old, ± 250 g) were submitted to ovariectomy (OVX). Eight weeks after the OVX, a tibial bone defect was created in all animals and they were randomly divided into 3 groups (n = 10): control bone defect group (CG): bone defects without any treatment; laser 60 J/cm 2 group (L60): animals irradiated with LLLT, at 60 J/cm 2 and laser 120 J/cm 2 group (L120): animals irradiated with LLLT, at 120 J/cm 2 . Results In the laser treated groups, at both fluences, a higher amount of newly formed bone was evidenced as well as granulation tissue compared to control. Picrosirius analysis demonstrated that irradiated animals presented a higher deposition of collagen fibers and a better organization of these fibers when compared to other groups, mainly at 120 J/cm 2 . COX-2, Cbfa-1 or VEGF immunoreactivity was detected in a similar manner either 60 J/cm 2 or 120 J/cm 2 fluences. However, no differences were shown in the biomechanical analysis. Conclusion Taken together, our results support the notion that LLLT improves bone repair in the tibia of osteoporotic rats as a result of stimulation of the newly formed bone, fibrovascularization and angiogenesis.