Identification of Apically Localized Endogenous Dental Pulp Stem Cells

Dental pulp is crucial for maintaining tooth vitality and function. Vital pulp provides defense mechanisms, sensory function, and tooth structural integrity. The presence of dental pulp stem cells (DPSCs) plays a role in the regeneration of damaged pulp and dentin. In immature teeth, the apical papilla at the apex harbors stem cells that are involved in root formation and maturation. Although stem cells isolated from the pulp and apical papilla have shown regenerative capacities, the in situ process of their involvement in pulp and dentin regeneration in response to injury is still unclear. Here, using single-cell transcriptomics and lineage tracing techniques, we identified the presence of endogenous Axin2+ DPSCs localized at the apex of mouse molars. The single-cell profiling identified 6 subpopulations of molar pulp tissue, including odontoblasts, pulp cells, and DPSCs. Lineage tracing analysis revealed that Axin2+ DPSCs gradually expand at the root apex and differentiate into pulp cells within the canal, contributing to pulp tissue formation in the pulp chamber and eventually maturing into odontoblasts over a period of at least 9 months. Upon pulp exposure or injury, the DPSCs rapidly proliferate and facilitate pulp healing and reparative dentin formation. Furthermore, the regenerative potential of the isolated DPSCs was demonstrated through their transplantation into the kidney capsule, leading to the successful formation of ectopic pulp tissue and reparative dentin. Identifying novel DPSCs at the apex provides new insights into pulp biology and establishes a foundation for regenerative endodontic therapies, leading to the deciphering of underlying mechanisms and development of new therapeutic strategies.