mTORC1 regulates exosomes release from odontoblasts to regulate DPSCs odontoblastic differentiation

Abstract Dental pulp stem cells (DPSCs) are the crucial part of dentin-pulp complex regeneration. A further understanding of the mechanism of how DPSCs stay in a quiescent state can contribute to improvements in dentin-pulp complex and dentinogenesis. Here, our study discovered that mTORC1 activation in odontoblasts resulted in thicker dentin and higher dentin volume/tissue volume of molars and led to increased exosomes marker expression levels of CD63 and Alix. In vitro, we confirmed that mTORC1 inactivation in odontoblasts reverses the inhibition of DPSC odontoblastic differentiation when cocultured with odontoblasts. Besides, our study indicated that exosomes derived from mTORC1-activated or mTORC1-inactivated MDPC23 both inhibited the odontoblastic differentiation of DPSCs and at same concentration. The miRNA sequence of exosomes derived from shTSC1-tansfected MDPC23 or rapamycin-treated MDPC23 or non-treated MDPC23 indicated that the majority of the miRNA was similar. Furthermore, we discovered that the exosomes derived from odontoblasts inhibited the odontoblastic differentiation of DPSCs, and the inhibitory effect was positively correlated with exosomes concentration. Taken together, mTORC1 regulates the exosomes release by odontoblasts to inhibit the odontoblastic differentiation of DPSCs but not the exosomes contents. These findings might provide a new understanding for dental-pulp complex regeneration.