Potential of human dental pulp stem cell-derived conditioned medium for amelo-/odontoblastic differentiation of HERS/ERM cells.

HERS/ERM cells constitute the only dental epithelial population that can be isolated from adult human teeth. Although HERS/ERM cells are the most studied dental epithelial cell source, information on their differentiation is lacking: these cells have a long induction period and low mineralization without coculture with dental mesenchymal stem cells. To characterize and develop an effective method for differentiating dental epithelial cells, we observed the epithelial‒mesenchymal interaction effects of deciduous dental pulp stem cell (dDPSC)-derived conditioned media (CM) during HERS/ERM cell differentiation. The collected CM was freeze-dried (DCM) and applied at high concentrations to determine the optimal concentration. The DCM-20 %, DCM-40 %, DCM-60 %, and DCM-80 % (v/v) groups presented an increased growth pattern. On day 2, increased expression of AMELX was detected in the DCM-60 % and DCM-80 % groups. ENAM expression was increased in the DCM-80 % group on day 2 and in the DCM-treated groups on day 4. In the DCM-80 % group, DSPP expression was significantly increased. In the DCM-60 % and DCM-80 % groups, high DSPP expression was detected. The ENAM expression in the DCM-80 % group was higher than that in the other groups. Mineralized nodules were detected on day 8 in the DCM-40 %, DCM-60 %, and DCM-80 % groups. The amount of calcium deposits increased with increasing DCM concentration. Our data indicated that dDPSC-CM has significant potential to induce ameloblastic and odontoblastic differentiation in HERS/ERM cells. The paracrine factors of dDPSC-CM could induce ameloblast differentiation without direct cell-to-cell interactions. These findings emphasize the potential of dDPSC-CM in the differentiation of HERS/ERM cells in vitro.