ABSTRACT: Adult stem cells maintain tissue integrity by continuous cellular turnover or serving progenitor cells. Human dental pulp stem cells (hDPSCs) are adult stem cells that can readily be isolated from extracted teeth, then expanded or stored for tissue repair and regeneration. However, stem cells undergo an aging process characterized by a decline in functional abilities, leading eventually to reduced organ function and delays in tissue repair. Like other stem cells, hDPSCs age and go through cellular senescence but little information is available on the mechanisms of aging or the details of the aged hDPSC phenotype. In this study, we investigated the aging phenotypes of human dental pulp and hDPSCs and attempted to rejuvenate them. In this study, hDPSCs were isolated from 23 third molars and primary cultured. Then, Flow cytometey, growth curve, dubling time, colony-forming-unit assay, cell viability after cryopreservation and in serum-free media culture, differntiation capacity for odonto-, adipo- and chondrogenesis, and RNA sequencing were analyzed. As results, the aged tooth maintained its weight of dental pulp however, the frequency of CD90+CD73+ mesenchymal stem cells inside pulp significantly decreased with donor aging. Moreover, each aged hDPSCs showed lower proliferative abilities, poorer survival rates, decreased tri-differentiation potential, and decline in metabolic activities than young hDPSCs. We also found those aged phenotypes could be recovered by cultivating aged hDPSCs in high concentration of fetal bovine serum (FBS) ex vivo and furthermore, the declined metabolic activities were restored by the culture. Here, we suggest a novel method of intervention for rejuvenating hDPSCs and these results have applications in both regenerative medicine and stem cell biology.
