Cellular and molecular heterogeneity of human skeletal muscle stem cells

Description

Abstract Satellite cells (SC) are Pax7+ tissue resident muscle stem cells, essential for muscle regeneration. SC are therefore considered as a potential stem cell source to treat skeletal muscle diseases. Nevertheless, as other primary muscle stem cells, SC are difficult to expand in vitro without dramatically reducing their regenerative potential. We have recently demonstrated that human myogenic reserve cells (RC) are quiescent myogenic stem cells with properties required for their use in cell therapy i.e. they survive, they form new myofibers and they generate new Pax7+ cells in vivo. Moreover, as compare to other muscle stem cells, RC hold the advantage to be generated in vitro in number compatible with possible therapeutic applications. We also showed that RC is an heterogenous population with a Pax7Hi and a Pax7Lo population. To study their cellular and molecular heterogeneity, we combined intracellular flow cytometry to isolate a pure population of Pax7Hi and Pax7Lo fixed-permeabilized human RC with high sensitivity RNAseq to analyze their transcriptional profile. Additionally, we study their metabolic and bioenergetic profile as metabolism is considered to be an active player in the regulation of cell state. Significant transcriptional changes were observed between Pax7Hi and Pax7Lo RC subpopulations with 399 modified genes. Pax7, Spry1 and Hes1 were upregulated in Pax7Hi subpopulation as genes involved in apoptosis, cell cycle regulation and oxidative stress. Our findings suggest that the Pax7Hi RC subpopulation adopt a more stem-like state and may constitute an appropriate stem cell source for potential therapeutic applications.