Significance
Rotator cuff tears affect millions of people in the U.S.; however, current interventions are hindered by persistent muscle degeneration. This study identifies the therapeutic potential for muscle recovery in the epimuscular fat in the rotator cuff, previously considered a negative feature of the pathology, and finds that this fat is beige, rather than white. This is important for two reasons. First, the stem cells that were isolated from this beige fat are more myogenic than those from white fat, which have been the focus of stem cell-based therapies to date, suggesting epimuscular fat could be a better stem cell source to augment rotator cuff repair. Second, these beige stem cells promote myogenesis in neighboring cells in culture, suggesting the potential for this fat to be manipulated therapeutically to promote muscle recovery through secreted signals.