Figure 1. Infusion of BM ECs from young mice rejuvenates HSCs in aged, irradiated mice.

In aged mice, there is a decline in the number of BM ECs, increased leakiness of the BM vasculature, and elevated intracellular ROS levels. The aged hematopoietic system is characterized by reduced HSC regenerative capacity, loss of T and B lymphocytes, and myeloid skewing. In this issue, Poulos and colleagues show that infusion of young ECs into aged, irradiated mice improves age-associated defects in BM ECs, restores HSC self-renewal capacity, and increases B and T cell numbers.