The effects of photobiomodulation therapy on mouse pre-osteoblast cell line MC3T3-E1 proliferation and apoptosis via miR-503/Wnt3a pathway

Photobiomodulation therapy (PBMT) has been demonstrated as regulating osteoblast proliferation. MicroRNAs (miRNAs) are involved in various pathophysiologic processes in osteoblast, but the role of miRNAs in the PBMT-based promotion of osteoblast proliferation remains unclear. This study aimed to investigate the effects of PBMT treatment (3.75J/cm(2)) on mouse pre-osteoblast cell line MC3T3-E1 proliferation and apoptosis via the miR-503/Wnt3a pathway; meanwhile, detect the expressions of miR-503 and Wnt3a after PBMT treatment and the role of miR-503 in regulating Wnt signaling molecules Wnt3a, -catenin, Runx2, apoptotic proteins caspase-3, and Bcl-2 in vitro. The PBMT parameters were as follows: 808nm continuous wavelength, 0.401W output power, 0.042W/cm(2) power density, 9.6cm(2) spot size, 36J energy, 3.75J/cm(2) energy density, 90s irradiation for three times per 12h, 14.5cm distance of the laser source and the angle of divergence of the laser beam was 7 degrees. In our present study, the target relationship was predicted and verified by bioinformatics analysis and luciferase reporter assays. Gene mRNA and protein expressions were examined by qPCR and western blot analysis. The MTT method was used to evaluate the effect of miR-503 on MC3T3-E1 cells proliferation. And cell apoptosis was examined by flow cytometry. The results showed that PBMT treatment reduced the expression of miR-503 and increased the level of Wnt3a (p<0.01). Bioinformatics analysis and luciferase reporter assays revealed that Wnt3a was a target of miR-503, and Wnt3a was regulated by miR-503. Furthermore, miR-503 was found to functionally inhibit proliferation and promote apoptosis (p<0.01). And during this process, Wnt3a, -catenin, Runx2, and Bcl-2 expressions were significantly inhibited (p<0.01); however, caspase-3 level was upregulated (p<0.01). These results suggest that miR-503 plays a role in osteoblast proliferation and apoptosis in response to PBMT, which is potentially amenable to therapeutic manipulation for clinical application.