Abstract

Skeletal muscle strength and regenerative capacity progressively decline with aging, partly due to functional impairment of muscle stem cells, the driving force in skeletal muscle repair and regeneration. However, the mechanisms responsible for age-associated muscle stem cell dysfunction remain elusive. A major barrier in addressing this challenge, has been the increased functional heterogeneity of the muscle stem cell population, which renders standard bulk analysis ineffective, and the lack of tools to resolve it, underscoring the need for single-cell studies.  

Here we capitalize on single-cell mass cytometry (also known as Cytometry by Time of Flight (CyTOF)), a transformative technology that allows the discovery of rare subsets within complex cell populations, to resolve functionally and molecularly distinct muscle stem cells subsets that arise with aging, and capture stem cell fate decisions in vivo. Using antibodies conjugated to stable metal isotopes, rather than fluorophores, CyTOF enables the simultaneous measurement of over 50 parameters per single-cell, facilitating the identification of novel cell subsets based on combinations of surface and intracellular markers.  

Through this cutting-edge approach we discovered novel cell surface markers that define a myogenic progression in vivo and identified previously unrecognized muscle stem cell subsets that underlie age-associated muscle stem cell dysfunction. These findings uncover a key signaling pathway that is dysregulated in aged muscle stem cells and can be effectively targeted in vivo to improve muscle regenerative capacity and muscle strength. The newly identified progenitor cells provide a critical missing link with which to study the control of stem cell fate, and shed light on the regulatory networks that govern cell state transitions in muscle diseases and aging.