Irradiation by blue light-emitting diode enhances osteogenic differentiation in gingival mesenchymal stem cells in vitro

The aim of this study was to investigate the effects of blue light irradiation on the process of osteogenic differentiation in stem cells. The cells used in this study were derived from human gingival mesenchymal stem cells (hGMSCs), and were treated with 0 (control group), 1, 2, 4 or 6 J/cm(2) blue light using blue light-emitting diodes. Cell growth was assessed by the 3-(4,5-Dimethyl-2-thiazolyl)-2,5-Diphenyl-2H-tetrazolium bromide (MTT) cell proliferation assay and osteogenic differentiation was evaluated by monitoring alkaline phosphatase (ALP) activity, alizarin red staining and real-time PCR (RT-PCR). The results of the MTT assay indicated that blue light inhibited hGMSC proliferation, and the ALP and alizarin red results showed that blue light promoted osteogenesis. The expression levels of the osteogenic genes runt-related transcription factor2 (Runx2), collagen type I (Col1) and osteocalcin (OCN) increased significantly (P < 0.05) when cells were irradiated with 2 or 4 J/cm(2) of blue light. In conclusion, irradiation with blue light inhibits the proliferation of hGMSC and promotes osteogenic differentiation.