Intercellular communication from myotubes to fibroblasts is differentially impacted by mineralocorticoid receptor signaling and muscular dystrophy.

backgroundReplacement of striated muscle with fibrosis leads to the symptoms and fatality in Duchenne muscular dystrophy (DMD). Transient local production of the mineralocorticoid aldosterone in the skeletal muscle microenvironment enhances wound healing. However, persistent aldosterone signaling through the mineralocorticoid receptor (MR) in multiple cell types within skeletal muscles exacerbates damage and fibrosis in DMD. Mineralocorticoid receptor antagonists demonstrate therapeutic benefits by preventing aldosterone binding to MR and downstream transcriptional activation. Therefore, defining aldosterone-mediated intercellular crosstalk in health and disease is highly relevant.

methodsTo delineate MR-regulated signaling mechanisms from myotubes to fibroblasts in health and disease, we treated cultured wild-type and dystrophin-deficient mdx (DMD model) myotubes with aldosterone or vehicle and used myotube conditioned media to treat neonatal fibroblasts isolated from the corresponding skeletal muscles. We performed: RNA sequencing of myotubes and conditioned media-treated fibroblasts, ligand-receptor predictions, unbiased cytokine profiling and fibroblast functional assays including proliferation, migration and matrix production to gain a systems-level understanding of intercellular communication from myotubes to fibroblasts.

resultsConditioned media from aldosterone-treated wild-type myotubes induced numerous transcriptional changes in wild-type fibroblasts, supporting MR-regulated cell communication from myotubes to fibroblasts. Mdx myotubes and conditioned media-treated fibroblasts showed an altered transcriptional profile compared to wild-type, supporting differences in both cell types due to intrinsic dystrophin deficiency even prior to the onset of pathology. Local aldosterone synthase prior to disease onset led to reduced differential expression in mdx fibroblasts from aldosterone-treated myotube signaling. Distinct ligand/receptor combinations influenced by MR-signaling and dystrophin deficiency in myotube to fibroblast signaling were identified. While signaling from aldosterone-treated wild-type myotubes enhanced fibroblast functional properties including proliferation and matrix production, signaling from dystrophic myotubes resulted in reduced migration and matrix production in dystrophic fibroblasts.

conclusionsThis study provides new mechanistic insight along the cell communication axis demonstrating that myotubes regulate fibroblast properties and this intercellular signaling is modified differentially by aldosterone and disease. These findings have implications for understanding skeletal muscle health and disease and improving wound healing and chronic fibrosis.