Activation of proliferation and differentiation of dental follicle stem cells (DFSCs) by heat stress

Objectives Adult stem cells (ASCs) remain in a slowly cycling/quiescent state under normal physiological conditions, but they can be awakened from this by certain factors, such as injury signals. Previously, our group has shown that dental follicle stem cells (DFSCs) appear to proliferate more rapidly than their non-stem cell counterparts at elevated temperatures. The study described here has aimed to (i) elucidate optimal temperature in which to culture DFSCs, (ii) determine whether elevated temperatures could enhance differentiation capability of DFSCs and (iii) characterize stem cell and osteogenic marker expression of DFSCs at elevated temperatures. Materials and methods DFSCs obtained from rat first molars were cultured at 37 (control), 38, 39, 40 and 41 degrees C. Cell proliferation was evaluated by Alamar blue reduction assay and mean numbers of viable dissociated cells. Osteogenic differentiation was evaluated after 7 or 14 days osteogenic induction. Expression of selected marker genes was also assessed during proliferation and differentiation of the cells. Results Increased cell proliferation was seen at heat-stress temperatures of 38 degrees, 39 degrees and 40 degrees C. DFSCs revealed maximal osteogenesis when cultured at 39 and 40 degrees C. Moreover, some stem cell and osteogensis-associated markers had elevated expression in heat-stress conditions. Conclusions Under determined heat-stress conditions, DFSCs increased their proliferation, osteogenic differentiation and expression of some marker genes. Thus, it is likely that elevated temperature could serve as a factor to activate adult stem cells.