Isolation and Analysis of FAPs and MuSCs

Magnetic activated cell sorting (MACS) was performed according to manufacturer instruction and as previously described^{8 (link)}. Briefly, injured Tibialis anterior muscles were harvested at 3 days post injury and mechanically and enzymatically dissociated with Collagenase II (Gibco 17101-015; 0.15% final) and Dispase II (Sigma D4693-16, 0.04% final) in DMEM. After filtration (70 um filter; Fisher 22363548), we first isolated FAPs using the CD140a (PDGFRα) MicroBead Kit (Miltenyi Biotec 130-101-502). The flow-through was then subjected to MuSC enrichment using the satellite cell isolation kit (Miltenyi Biotec 130-104-268). Once each population was isolated, cells were resuspended in RLT buffer followed by RNA isolation (Qiagen RNeasy Micro Kit 74004) and RT-qPCR analysis as outlined above.