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This study evaluated the morphological changes produced by LLLT on the initial stages of bone healing and also studied the pathways that stimulate the expression of genes related to bone cell proliferation and differentiation. One hundred Wistar rats were divided into control and treated groups. Noncritical size bone defects were surgically created at the upper third of the tibia. Laser irradiation (Ga-Al-As laser 830 nm, 30 mW, 94 s, 2.8 J) was performed for 1, 2, 3, 5, and 7 sessions. Histopathology revealed that treated animals produced increased amount of newly formed bone at the site of the injury. Moreover, microarray analysis evidenced that LLLT produced a significant increase in the expression TGF-β, BMP, FGF, and RUNX-2 that could stimulate osteoblast proliferation and differentiation, which may be related to improving the deposition of newly formed bone at the site of the injury. Thus, it is possible to conclude that LLLT improves bone healing by producing a significant increase in the expression of osteogenic genes.

The aim of this study was to evaluate the influence of postmenopausal bone loss (induced by ovariectomy) in the process of bone healing in a tibial bone defect model in rats by means of histological evaluation of bone defects and the analysis of the expression of genes and proteins involved in bone consolidation. Twenty female Wistar rats (12 weeks old, weighing ±250 g) were randomly divided into two groups: control group (CG) and ovariectomized group (OG). Rats of OG were submitted to ovariectomy and after 8 weeks post-surgery, all animals were submitted to the tibial bone defect model. The main histological finding analysis revealed that ovariectomized animals showed a higher amount of granulation tissue and immature newly formed bone compared to CG. Furthermore, quantitative histological analysis showed that OG presented a significant decrease in the amount of newly formed bone (p = 0.0351). RT-PCR analysis showed no difference in Runx2, ALP, RANK, RANKL and Osterix gene expression 14-day post-surgery. Interestingly, immunohistochemical evaluation showed that Runx2 was down expressed (p = 0.0001) and RANKL was up expressed (p = 0.0022) in the OG. In conclusion, these data highlight that bone loss induced by ovariectomy causes an impairment in the capacity of bone to heal mainly probably because of alterations in the imbalance of osteoblasts and osteoclasts activities.