Denervation-related alterations and biological activity of miRNAs contained in exosomes released by skeletal muscle fibers

Abstract

Exosomes are vesicles released by many eukaryotic cells; their cargo includes proteins, mRNA and microRNA (miR) that can be transferred to recipient cells and regulate cellular processes in an autocrine or paracrine manner. While cells of the myoblast lineage secrete exosomes, it is not known whether skeletal muscle fibers (myofibers) release exosomes. In this study, we found that cultured myofibers release nanovesicles that have bilamellar membranes and an average size of 60–130 nm, contain typical exosomal proteins and miRNAs and are taken up by C2C12 cells. miR-133a was found to be the most abundant myomiR in these vesicles while miR-720 was most enriched in exosomes compared to parent myofibers. Treatment of NIH 3T3 cells with myofiber-derived exosomes downregulated the miR-133a targets proteins Smarcd1 and Runx2, confirming that these exosomes have biologically relevant effects on recipient cells. Denervation resulted in a marked increase in miR-206 and reduced expression of miRs 1, 133a, and 133b in myofiber-derived exosomes. These findings demonstrate that skeletal muscle fibers release exosomes which can exert biologically significant effects on recipient cells, and that pathological muscle conditions such as denervation induce alterations in exosomal miR profile which could influence responses to disease states through autocrine or paracrine mechanisms.

Recovery from 6‐month spaceflight at the International Space Station: muscle‐related stress into a proinflammatory setting

“…In particular, miR‐206 and miR‐21 have been found to increase in muscle tissue in catabolic/atrophy condition in a mouse model (38). The contribution of muscle atrophy/wasting to the pool of c‐miRs was recently confirmed in exosomes released by myofibers, supporting the conclusion that myofiber‐derived exosomes modulate protein levels of key factors in myogenic or osteogenic differentiation of mesenchymal progenitor cells (39). In particular, miR‐21‐5p was shown to promote the osteogenic differentiation of mouse bone marrow cells by targeting Sprouty homolog 1 (Spryl), negatively regulating the osteogenic differentiation of mesenchymal stem cells (40).…”

Skeletal muscle tissue secretes more extracellular vesicles than white adipose tissue and myofibers are a major source ex vivo but not in vivo

“…Cell monocultures are a relatively simple system for studying SkM myocyte-derived EVs, but they lack the organization and extracellular matrix characteristic of tissues. Ex vivo incubation of SkM tissue explants has been shown to be an alternative approach to study EVs (1,4,18,25). This method yields EVs with a comparable size, morphology and composition to EVs from cultured cells or blood (1).…”

“…SkM tissue-derived EVs from obese mice increase expression of genes involved in regulating beta-cell mass in lean recipient mice (18). SkM tissue-derived EVs from hind limb denervated mice alter adipocyte gene expression in a co-culture system (4). In addition to SkM explants, WAT explants have also been studied.…”

Secreted miRNAs in the tripartite neuromuscular junction

“…In 2017, Gasperi et al reported that skeletal muscle fibers release exosomes. Furthermore, Denervation resulted in a marked increase in miR-206 and reduced expression of miR-1, miR-133 in myofiber-derived exosomes [19]. These findings demonstrate that muscle cells release exosomes which can transfer biologically active miRNAs to recipient cells.…”