Transplanting rejuvenated blood stem cells extends lifespan of aged immunocompromised mice [scRNA-seq of LSK cells]

One goal of regenerative medicine is to rejuvenate tissues and extend lifespan by restoring the function of endogenous aged stem cells. However, evidence that somatic stem cells can be targeted in vivo to extend lifespan is still lacking. Here, we demonstrate that after a short systemic treatment with a specific inhibitor of the small RhoGTPase Cdc42 (CASIN), transplanting aged hematopoietic stem cells (HSCs) from treated mice is sufficient to extend the healthspan and lifespan of aged immunocompromised mice without additional treatment. In detail, we show that systemic CASIN treatment improves strength and endurance of aged mice by increasing the myogenic regenerative potential of aged skeletal muscle stem cells. Further, we show that CASIN modifies niche localization and H4K16ac polarity of HSCs in vivo. Single cell profiling reveals changes in HSC transcriptome, which underlie enhanced lymphoid and regenerative capacity in serial transplantation assays. Overall, we provide proof-of-concept evidence that a short systemic treatment to decrease Cdc42 activity improves the regenerative capacity of different endogenous aged stem cells in vivo, and that rejuvenated HSCs exert a broad systemic effect sufficient to extend murine health- and lifespan. Overall design: Aged mice (C57Bl6, >80 weeks old) were treated with CASIN for 4 consecutive days (1 i.p injection every 24h). At day 5, samples were taken from the bone marrow from treated aged mice, as well as young control (C57Bl6, 10-12 weeks old) and aged control mice (controls treated only with cyclodextrin). Lin- cKit+ Sca1+ (LSK) bone marrow cells were sorted to perform scRNA-seq. There are a total of 3 replicates per mice condition.