Title Identification and characterization of endogenous dental pulp stem cells Abstract The goal of this proposal is to identify and characterize endogenous dental pulp stem cells (DPSCs) in adult mice molars. Although continuously growing mouse incisors have been used as a model system to characterize dental stem cells, endogenous DPSCs within the molars remain understudied. Unlike incisors, mouse molars are not continuously growing and resemble human teeth. Therefore, it is crucial for the field of stem cell biology as well as dental pulp regeneration therapy to identify and characterize endogenous DPSCs isolated from the molars. To conduct this research we have developed a mouse model in which Axin2+ dental pulp cells in molars are genetically labeled. Our preliminary assessment shows that Axin2+ DPSCs are capable of self-renewing and differentiating into mature odontoblasts for a year in vivo. In addition, the transplanted dental pulp cells are capable regenerate pulp-like tissue. This initial discovery shows a difference in the type of tissues regenerated from other adult stem cells and DPSCs, suggesting their unique cellular plasticity present in endogenous DPSCs. In this application, we will test if Axin2-expressing DPSCs can meet the criteria of adult stem cells. We will also examine the stem cells properties at a single cell level. The regenerative ability and cellular plasticity of the transplanted endogenous DPSCs will be carefully assessed. Potential heterogeneity of Axin2+ DPSCs will be identified through single-cell RNA-sequence analysis and bioinformatics analysis. The completion of this proposal has outstanding potential to advance our knowledge base of endogenous DPSCs in molars, leading to novel strategies for tissue regeneration therapies.