The role of dentin matrix protein 1 (DMP1) in regulation of osteogenic differentiation of rat dental follicle stem cells (DFSCs)

Abstract

ObjectivesPrimary isolated dental follicle stem cells (DFSCs) possess a strong osteogenesis capability, and such capability is reduced during in vitro culture. Because dentin matrix protein 1 (DMP1) is essential in the maturation of osteoblasts, our objectives were to determine (1) the expression of DMP1 in the DFSCs, (2) the correlation between DMP1 expression and osteogenic capability of DFSCs, and (3) the ability of DMP1 to promote osteogenic differentiation of DFSCs. MethodsDFSCs and their non-stem cell counterpart dental follicle cells (DFC) were established from postnatal rat pups. Expression of DMP1 in the DFSCs and DFC was determined using real-time RT-PCR and western blotting. Different passages of DFSCs were subjected to osteogenic induction. The correlation between osteogenesis and DMP1 expression was analyzed. Then, expression of DMP1 in the DFSCs was knocked-down using siRNA, followed by osteogenic induction to evaluate the effect of DMP1-knockdown. Finally, the late passage DFSCs with reduced DMP1 expression and osteogenic capability were cultured in osteogenic induction medium containing mouse recombinant DMP1 (mrDMP1) to determine if DMP1 can restore osteogenesis of DFSCs. ResultsDFSCs expressed much higher levels of DMP1 than did DFC. DMP1 expression was correlated with the osteogenic capability of DFSCs. Knockdown of DMP1 expression markedly decreased the osteogenesis and osteogenic gene expression in the DFSCs whereas adding mrDMP1 protein to the osteogenic induction medium enhanced osteogenesis. ConclusionsDMP1 is highly expressed in the DFSCs, but minimally expressed in non-stem cell DFC. DMP1 appears to play an important role for osteogenic differentiation of the DFSCs.