Extracellular vesicles released by senescent myoblasts affect recipient cells via miRNA-target interactions

Cellular senescence is a state of irreversible cell cycle arrest accompanied by a robust Senescence-Associated Secretory Phenotype (SASP) that disrupts the local and systemic microenvironment. In skeletal muscle, aging is accompanied by the dysfunction of resident muscle stem cells, also known as satellite cells, as well as chronic, low-grade systemic inflammation, which is partially driven by the SASP. Extracellular vesicles (EVs) are emerging as potential mediators of SASP intercellular communication; however, little is known within the context of skeletal muscle senescence. Here, we observed that senescent myoblasts release SASP factors in vitro that reduce myotube diameter by approximately 30% (p < 0.05). EVs released by these cells contained miRNAs directly implicated in cellular senescence and anti-apoptotic signalling. We identified 22 differentially expressed miRNAs (FDR < 0.05; |FC| > 1.5) within senescent myoblast-derived EVs (SEVs), including miR-34a/b/c and miR-22. Furthermore, miR-301a-3p was revealed as a novel mediator of several genes related to senescence. SEV transfer onto myoblasts significantly upregulated the anti-apoptotic gene Mdm2 (p < 0.05; 60% increase), a member of the senescence-associated super-enhancer family. Lastly, we integrated the miRNA gene target data with the transcriptomic profiles of adult (8mo) and geriatric (28mo) mouse gastrocnemius muscles and observed a significant overlap in gene regulation by SEV miRNAs during aging. Taken together, these results indicate that EVs and their miRNA cargo may be potential contributors to the SASP and senescence-associated signalling in skeletal muscle during advanced aging.