Transcriptional Evidence for Transient Regulation of Muscle Regeneration by Brown Adipose Transplant in the Rotator Cuff

Chronic rotator cuff injuries can lead to a degenerative microenvironment that favors chronic inflammation, fibrosis, and fatty infiltration. Recovery of muscle structure and function will ultimately require a complex network of muscle resident cells, including satellite cells, fibro-adipogenic progenitors (FAPs), and immune cells. Recent work suggests that signaling from adipose tissue and progenitors could modulate regeneration and recovery of function, particularly pro-myogenic signaling from brown or beige adipose (BAT). In this study, we sought to identify cellular targets of BAT signaling during muscle regeneration using a rotator cuff BAT transplantation mouse model. Cardiotoxin injured supraspinatus muscle had improved mass at 7 day post-surgery (dps) when transplanted with exogeneous BAT. Transcriptional analysis revealed transplanted BAT modulates FAP signaling early in regeneration likely via crosstalk with immune cells. To investigate the effect of BAT on muscle regeneration, we collected primary cells isolated from the supraspinatus of 12-week-old male C57BL/6J mouse. Paired samples were collected from the same mouse. The BAT samples were isolated from muscles injected with cardiotoxin and then transplanted with interscapular BAT from 3wks-old mouse. The CTL samples were from muscles injured with cardiotoxin only. SCs (CD45-/CD31-/Sca1+/a7integrin+) and FAPs (CD45-/CD31-/Sca1+/a7integrin-) were sorted for RNA isolation with a FACSAria II. We performed differeitial expression gene analysis on the RNASeq results from isolated SCs and FAPs at 2 timepoints.