This study was aimed to evaluate the effects of low-level laser therapy (LLLT) in the treatment of trabecular bone loss induced by skeletal unloading. Twelve mice have taken denervation operation. At 2 weeks after denervation, LLLT (wavelength, 660 nm; energy density, 3 J/cm2) was applied to the right tibiae of six mice (LASER) for 5 days/week over 2 weeks by using a minimally invasive laser needle system (MILNS) which consists of a 100 μm optical fiber in a fine needle (diameter, 130 μm). Structural parameters and histograms of bone mineralization density distribution (BMDD) were obtained before LLLT and at 2 weeks after LLLT. In addition, osteocyte, osteoblast, and osteoclast populations were counted. Two weeks after LLLT, bone volume fraction, trabeculae number, and trabeculae thickness were significantly increased and trabecular separations, trabecular bone pattern factor, and structure model index were significantly decreased in LASER than SHAM (p < 0.05). BMDD in LASER was maintained while that in SHAM was shifted to lower mineralization. Osteocyte and osteoblast populations were significantly increased but osteoclast population was significantly decreased in LASER when compared with those in SHAM (p < 0.05). The results indicate that LLLT with the MILNS may enhance bone quality and bone homeostasis associated with enhancement of bone formation and suppression of bone resorption.
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