Cell Rep. 2019 May 14;27(7):2029-2035.e5. doi: 10.1016/j.celrep.2019.04.074.

Mesenchymal Stromal Cells Are Required for Regeneration and Homeostatic Maintenance of Skeletal Muscle.

Wosczyna MN¹, Konishi CT², Perez Carbajal EE², Wang TT², Walsh RA², Gan Q², Wagner MW², Rando TA³.

Abstract

The necessity of mesenchymal stromal cells, called fibroadipogenic progenitors (FAPs), in skeletal muscle regeneration and maintenance remains unestablished. We report the generation of a PDGFRα^CreER knockin mouse model that provides a specific means of labeling and targeting FAPs. Depletion of FAPs using Cre-dependent diphtheria toxin expression results in loss of expansion of muscle stem cells (MuSCs) and CD45+ hematopoietic cells after injury and impaired skeletal muscle regeneration. Furthermore, FAP-depleted mice under homeostatic conditions exhibit muscle atrophy and loss of MuSCs, revealing that FAPs are required for the maintenance of both skeletal muscle and the MuSC pool. We also report that local tamoxifen metabolite delivery to target CreER activity in a single muscle, removing potentially confounding systemic effects of ablating PDGFRα+ cells distantly, also causes muscle atrophy. These data establish a critical role of FAPs in skeletal muscle regeneration and maintenance.