Mechanical strain triggers differentiation of dental mesenchymal stem cells by activating osteogenesis-specific biomarkers expression

Dental stem cell biotechnology has been used as a potential method to treat the dental diseases. This study aimed to investigate effects of mechanical stimulation on osteogenic properties of rat dental mesenchymal stem cells (DMSCs). DMSCs were isolated from rat teeth root tissues and identified by detecting vimentin and keratin expression. Flexcell FX4K tension system that mediating cyclic strain was used to treat DMSCs. MTT assay was used to observe DMSCs viability. Alkaline phosphatase (ALP) staining and alizarin red staining were conducted. Osteogenesis-specific biomarkers, such as receptor activator for nuclear factor-kB ligand (RANKL), osteoprotegerin (OPG), dentin sialoprotein (DSP) and bone sialoprotein (BSP), were evaluated using RT-PCR, western blot and immunohistochemistry assay, respectively. Positive ALP staining and alizarin red staining confirmed DMSCs phenotype. There were no significant morphology differences between mechanical stimuli treated cells and normal control cells. MTT results showed no significant differences between normal control cells and mechanically stimulated DMSCs. RT-PCR, western blot and immunohistochemistry assay indicated that 10% cyclic strain could trigger an obvious change of mRNA and protein expression of RANKL, OPG, DSP and BSP, respectively. Mechanical stimulation could trigger relative higher levels of calcium deposition in DMSCs. Mechanical strain triggered bone formation mainly through activating RANKL gene expression. In conclusion, 10% cycle mechanical strain could stimulate higher amounts of ALP and calcium deposition by activating RNAKL, and could trigger dramatically changes of mRNA and protein expression of osteogenesis-specific biomarkers, such as OPG, BSP and DSP