Abstract

High-Resolution Lineage Mapping of Myogenesis in vivo

Ermelinda Porpiglia, Life Science Research Associate, Stanford University School of Medicine

Muscle regeneration is a dynamic process during which the state and identity of the cells involved changes over time. Adult muscle stem cells are the driving force in skeletal muscle repair and regeneration. Mostly quiescent in healthy individuals, they become activated in response to muscle injury. While the phenotypic identity of muscle stem cells has been previously established, muscle progenitor cells, which are at a stage in between the stem cell and the mature functional myogenic cell, have not yet been identified in vivo. Progenitor cells hold enormous potential as a platform to study the cellular behavior and molecular control of stem cell fate, to identify novel therapeutic targets for muscle diseases, and to develop cell therapy applications for regenerative medicine. However, a major roadblock in their identification has been a lack of tools to resolve cellular heterogeneity in skeletal muscle, underscoring the importance of single-cell studies. We have capitalized on single-cell mass cytometry (CyTOF), a transformative technology that allows the discovery of novel subsets within a complex cell population, to capture stem cell fate decisions in vivo. We discovered novel cell surface markers that define a myogenic progression in vivo, by combining a high-throughput flow cytometry screen with CyTOF analysis of skeletal muscle. Importantly, using new marker sets we identified stem cells and previously unrecognized progenitor cell populations. We showed by lineage tracing experiments that these progenitor populations originate from muscle stem cells and exhibit distinct regenerative potential in vivo. Moreover, high dimensional CyTOF analysis in response to acute injury revealed the cellular and molecular dynamics of muscle regeneration at a level of resolution not previously possible.