Photobiomodulation effects of Low-level light irradiation (LLLI) on regeneration have been reported in skin, nerve, and skeletal muscle tissues and bone. Bone Mesenchymal stem cells (BMSCs) are derived from bone marrow, which exhibited a ?broblast-like appearance, and could differentiate in vitro into different lineages. However, there is a reciprocal relationship between growth and osteogenic differentiation in MSCs. Therefore, it’s important to investigate the effect of LLLI on BMSCs. The aim of our study was to investigate the proliferation effect of 635 nm red laser light on bone marrow MSCs with or without osteogenic supplements. Bone marrow was collected from the 4-week-old Sprague–Dawley rats femur and tibiae. MSCs with and without osteogenic supplements both were divided into three groups. A continuous 635 nm wavelength red light diode laser (a power output of 960 mW) was used in the study. The size of light spot was 35mm in diameter. Irradiation was performed every other day since the half of medium was changed to osteogenic differentiation media (ODM). The first irradiation day was set as 0 day. The duration of each irradiation for red light was calculated at 10 seconds for 1 J/cm2, 20 seconds for 2 J/cm2. Two of these groups were used as controls: MSCs incubated in DMEM without irradiation (control 1), MSCs incubated in ODM without irradiation (control 2). Cellular proliferation was evaluated by using WST-8. Cell viability was assessed with WST-8 kit at 2, 4, 6 and 8 days, respectively. At 4, 6 and 8 days, groups cultured with DMEM showed significantly higher viabilities than that in groups with ODM. In groups with DMEM, red light at all doses significantly stimulated cell viability as compared with the control 1. Groups irradiated at 1 and 2 J/cm2 had more effective proliferation on 4 (P < 0.01) and 6 days (P < 0.05), when compared with the control 1. In groups with ODM, control 2 and the irradiated groups showed similar proliferation speeds. In conclusion, we can find that red light can promote proliferation of MSCs cultured in normal media, and suppress proliferation of MSCs cultured in ODM.
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