Chaperone-mediated autophagy sustains muscle stem cell regenerative functions but declines with age

Proteostasis supports stemness and its loss correlates with the functional decline of diverse stem cell types. Here we identify that chaperone-mediated autophagy (CMA), a selective autophagy pathway, is necessary for the regenerative capacity of muscle stem cells (MuSCs) throughout life. We show that CMA is active in MuSCs, while genetic loss of CMA in MuSCs or failure of CMA in normally aged cells causes a proliferative impairment, resulting in defective skeletal muscle regeneration. Reactivation of CMA in old MuSCs boosts their proliferative capacity and improves their regenerative ability. Using comparative proteomics to identify CMA substrates, we uncovered actin cytoskeleton and glycolytic metabolism as key processes altered in aged mice and human MuSCs. Our findings reveal CMA to be a decisive stem-cell-fate regulator, with implications for fostering muscle regeneration in old age.