Dynamic structural cell responses in the thymus to acute injury, regeneration, and age

The thymus, the primary site of T cell development, is extremely sensitive to insult but also harbors tremendous capacity for repair. Using single cell sequencing of thymic structural cells, as well as functional and structural analyses, we revealed distinct regenerative programs by endothelial and mesenchymal subsets after injury that stimulated epithelial repair; the compartment primarily supporting T cell development. Thymic function not only declined over lifespan, contributing to immune aging, but the capacity of the thymus to regenerate after damage also declined in old mice. This could be attributed to an inability of the old microenvironment to induce reparative programs; leading to reduced ability to restore tissue structure and function. These findings provide a detailed framework for the response of structural cells to aging and acute damage, which could have considerable implications for our understanding of aging immunity and recovery from treatments such as chemotherapy and bone marrow transplant. ### Competing Interest Statement Dr. Marcel van den Brink has received research support and stock options from Seres Therapeutics and stock options from Notch Therapeutics and Pluto 10 Therapeutics; he has received royalties from Wolters Kluwer; has consulted, received honorarium from or participated in advisory boards for Seres Therapeutics, WindMIL Therapeutics, Rheos Medicines, Merck & Co, Inc., Magenta Therapeutics, Frazier Healthcare Partners, Nektar Therapeutics, Notch Therapeutics, Forty Seven Inc., Priothera, Ceramedix, Lygenesis, Pluto Therapeutics, GlaskoSmithKline, Da Volterra, Vor BioPharma, Novartis 15 (Spouse), Synthekine (Spouse), and Beigene (Spouse); he has IP Licensing with Seres Therapeutics and Juno Therapeutics; and holds a fiduciary role on the Foundation Board of DKMS (a nonprofit organization).