UCLA

Normal T cell production from hematopoietic stem and progenitor cells (HSPCs) declines with age, causing the immune system to become less efficient at fighting illnesses ranging from infections to cancer. T cell development begins when HSPCs from the bone marrow circulate in the blood and home to an organ called the thymus. After populating the thymus, HSPCs are first directed to a T cell fate. In later stages, committed thymocytes advance through pivotal checkpoints to mature into different types of T cells with specialized functions that then egress from the thymus. Although the metabolism of peripheral and activated T cells has been extensively studied, metabolic changes during stem cell development into T cells are not well understood, especially in human thymus. In vitro models of T cell differentiation are promising tools to study T cell development, but how well they reflect in vivo metabolism remains unclear. Studying metabolic changes in vitro also faces several challenges due to limitations in current standard culture systems. Previously, our lab developed an in vitro 3D “Artificial Thymic Organoid” (ATO) model that generates functional human T cells from various stem cell sources. Our goal is to improve T cell production and ultimately advance T cell therapies that regenerate the immune system. Here, we adapt the ATO system to recapitulate thymic differentiation of murine HSPCs into mature T cells and overcome several limitations of previous in vitro systems. Next, we integrate transcriptomics and metabolic extracellular flux data from human and murine in vivo and in vitro thymocytes to define the metabolic signatures that distinguish T lineage commitment and T cell maturation stages in the thymus. We reveal that patterns of metabolic activity are remarkably well-conserved in human and murine species, and during in vitro T cell development. Glycolysis and oxidative phosphorylation are drastically reduced at the developmental stage during which thymocytes are completing T cell receptor (TCR) rearrangement. Using an in vitro mouse knockout model of the recombinase activating gene Rag-1, we demonstrate that metabolic activity persistently decreases at the same stage even in the absence of TCR rearrangement. Thus, our results identify critical metabolic transitions that are highly conserved between species as well as in vivo and in vitro T cell development. Future studies in the lab would study the impact of perturbing metabolic pathways on T cell development, particularly in the context of aging.