Connexin43-containing gap junctions potentiate extracellular Ca2+-induced odontoblastic differentiation of human dental pulp stem cells via Erk1/2

Abstract

Extracellular Ca2+ can promote dentin sialophosphoprotein (DSPP) expression and odontoblastic differentiation of dental pulp stem cells (DPSCs). Gap junctions mediated by connexin43 (Cx43) allow diffusion of small molecules (such as Ca2+) among cells to regulate cell-to-cell communications. However, it is unclear whether Cx43 is required for the Ca2+-induced cell differentiation. Here, we found that the influx of extracellular Ca2+ through L-type Ca2+ channels increases intracellular free Ca2+ levels to promote DSPP expression. Cx43 overexpression potentiated the extracellular Ca2+-induced DSPP expression via Erk1/2. Flow cytometry analyses showed that Cx43 increased the percentage of p-Erk1/2 positive cells in response to Ca2+, indicating that Cx43 in DPSCs possibly acts as a traditional gap junction channel, which permits the sharing of signals among coupled cells to make more DPSCs respond to Ca2+. Furthermore, inhibition of Cx43 function and gap junction communication decreased Ca2+-induced the expression of DSPP, suggesting that cell-to-cell contacts are required for Cx43 to promote the Ca2+-induced cell differentiation. Similarly, the study performed on DPSCs cultured at low-density and high-density revealed that intercellular contacts are required to potentiate Erk1/2 activity and DSPP expression. In total, this study indicates that Cx43 increases Ca2+-induced DSPP expression and odontoblastic differentiation of DPSCs via Erk1/2 through gap junction-mediated cell-to-cell contacts.