Lgr5 Marks Adult Progenitor Cells Contributing to Skeletal Muscle Regeneration and Sarcoma Formation

Regeneration of adult skeletal muscle is driven largely by resident satellite cells, a stem cell population increasingly considered to display a high degree of molecular heterogeneity. In this study, we find that Lgr5, a receptor for Rspo and a potent mediator of Wnt/β-catenin signaling, marks a subset of activated satellite cells that contribute to muscle regeneration. Lgr5 is found to be rapidly upregulated in purified myogenic progenitors following acute cardiotoxin-induced injury. In vivo lineage tracing using our Lgr5-2ACre^ERT2R26tdTomato^LSL reporter mouse model shows that Lgr5⁺ cells can reconstitute damaged muscle fibers following muscle injury, as well as replenish the quiescent satellite cell pool. Moreover, conditional mutation in Lgr52ACre^ERT2;Kras^G12D;Trp53^flox/flox mice drives undifferentiated pleomorphic sarcoma formation in adult mice, thereby substantiating Lgr5⁺ cells as a cell of origin of sarcomas. Our findings provide the groundwork for developing Rspo/Wnt-signaling-based therapeutics to potentially enhance regenerative outcomes of skeletal muscles in degenerative muscle diseases.