2415-P: Quiescence Activates p53 and Promotes Reactive Oxygen Species-Induced DNA Damage Repair in Rejuvenation of Aged Mesenchymal Stem Cells

Introduction and Objective: Mesenchymal stem cell (MSC)-based cell therapies for diabetic ulcers have attracted much attention, but have yet to become widespread. One of the reasons is that chronic inflammation in diabetes accelerates aging of MSCs, which significantly impairs their anti-inflammatory functions. We have previously reported that introducing quiescence in adipose tissue-derived stromal cells (ADSCs), a type of MSC that has been utilized for MSC-based cell therapies, rejuvenates ADSCs, restoring their attenuated cellular functions, and their transplantation enhances wound healing in diabetic mice. In this study we investigated the molecular mechanism of quiescence-induced rejuvenation of ADSC. Methods: ADSCs exceeding 15 passages were used for this study. They were subjected to quiescence by being cultured in three-dimensional gels with the stiffness of adipose tissue for 24 hours, and then removed from the gels to bring them back to a non-quiescent state. Results: Aged ADSCs exhibited attenuated ability to proliferate, differentiate into osteoblasts, and secrete Indoleamine 2,3-deoxygenase (IDO) upon stimulation with tumor necrosis factor alpha (TNFα)/interferon gamma (IFNγ). However, these attenuated cellular functions were restored by going through quiescence. The aged ADSCs showed accumulation of reactive oxygen species (ROS) and γH2AX foci in the nucleus, indicating DNA damage, but after aged ADSCs went through quiescence, both ROS accumulation and γH2AX foci disappeared. Furthermore, aged ADSCs showed nuclear localization of p53, which translocated to the cytoplasm after quiescence. When aged ADSCs went through quiescence in the presence of p53 inhibitor, pifislin α, ROS accumulation was eliminated, whereas γH2AX foci in the nucleus and loss of TNFα/IFNγ-dependent enhanced IDO secretion persisted. Conclusion: These results suggest that subjecting aged ADSCs to quiescence eliminates ROS accumulation and promotes DNA damage repair via p53, which contributes to ADSC rejuvenation. Disclosure M. Funaki: Other - Founder, Board member, stock holder; Ended; Mechanogenic, Inc. A. Hata: Research Support; Current; Mechanogenic, Inc. Funding Mechanogenic, Inc.