Physioxia enhances T cell development ex vivo from human hematopoietic stem and progenitor cells.

Understanding physiologic T cell development from hematopoietic stem (HSCs) and progenitor cells (HPCs) is essential for development of improved hematopoietic cell transplantation (HCT) and emerging T-cell therapies. Factors in the thymic niche, including Notch 1 receptor ligand, guide HSCs and HPCs through T cell development in vitro. We report that physiologically relevant oxygen concentration (5% O2 , Physioxia), an important environmental thymic factor promotes differentiation of cord blood CD34+ cells into progenitor T (proT) cells in serum-free and feeder-free culture system. This effect is enhanced by a potent reducing and antioxidant agent, ascorbic acid. Human CD34+ cell-derived proT cells in suspension cultures maturate into CD3+ T cells in an artificial thymic organoid (ATO) culture system more efficiently when maintained under physioxia, compared to ambient air. Low oxygen tension acts as a positive regulator of HSC commitment and HPC differentiation toward proT cells in the feeder-free culture system and for further maturation into T cells in the ATO. Culturing HSC/HPCs in physioxia is an enhanced method of effective progenitor T and mature T cell production ex vivo and may be of future use for HCT and T-cell immunotherapies. © AlphaMed Press 2020 SIGNIFICANCE STATEMENT: Our report is the first to investigate the role of physiologically relevant oxygen concentration (5% O2, Physioxia) on the ex vivo sequence of T cell differentiation and maturation from human hematopoietic stem and progenitor cells. Physioxia promotes hematopoietic stem cell commitment and hematopoietic progenitor cell differentiation into progenitor/precursor T cells in suspension culture, effects enhanced with a potent antioxidant ascorbic acid, and which further facilitates T cell maturation in artificial thymic organoids. This provides new insight into human T cell development and may be useful for future clinical translation for patients treated with CB HCT and for immunocompromised patients.