Many adult tissues contain resident stem cells, such as the Pax7+ satellite cells within skeletal muscle, that regenerate parenchymal elements following damage. Tissue-resident mesenchymal progenitors (MPs) also participate in regeneration, although their function and fate in this process are unclear. Here, we identify Hypermethylated in cancer 1 (Hic1) as a marker of MPs in skeletal muscle and further show that Hic1 deletion leads to MP hyperplasia. Single-cell RNA-seq and ATAC-seq analysis of Hic1+ MPs in skeletal muscle shows multiple subpopulations, which we further show have distinct functions and lineage potential. Hic1+ MPs orchestrate multiple aspects of skeletal muscle regeneration by providing stage-specific immunomodulation and trophic and mechanical support. During muscle regeneration, Hic1+ derivatives directly contribute to several mesenchymal compartments including Col22a1-expressing cells within the myotendinous junction. Collectively, these findings demonstrate that HIC1 regulates MP quiescence and identifies MP subpopulations with transient and enduring roles in muscle regeneration.
Keywords: lineage tracing; mesenchymal progenitors; myotendinous junction; pericytes; quiescence; scATAC-seq; scRNA-seq; skeletal muscle; tendon; tissue regeneration.
Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.