Analyses of Mesenchymal Progenitors in Skeletal Muscle by Fluorescence-Activated Cell Sorting and Tissue Clearing.

Mesenchymal progenitors, which are resident progenitor populations residing in skeletal muscle interstitial space, contribute to pathogeneses such as fat infiltration, fibrosis, and heterotopic ossification. In addition to their pathological roles, mesenchymal progenitors have also been shown to play important roles for successful muscle regeneration and homeostatic muscle maintenance. Therefore, detailed and accurate analyses of these progenitors are essential for the research on muscle diseases and health. Here, we describe a method for purification of mesenchymal progenitors based on the expression of PDGFRα, which is a specific and well-established marker for mesenchymal progenitors, using fluorescence-activated cell sorting (FACS). Purified cells can be used in several downstream experiments including cell culture, cell transplantation, and gene expression analysis. We also describe the method for whole-mount 3-dimensional imaging of mesenchymal progenitors by utilizing tissue clearing. The methods described herein provide a powerful platform for studying mesenchymal progenitors in skeletal muscle.