Exosomes and Extracellular RNA in Muscle and Bone Aging and Crosstalk

(a). PURPOSE: Extracellular vesicles (EV), which include exosomes and microvesicles, are membrane-bound particles shed by most cell types and are important mediators of cell-cell communication by delivering their cargo of proteins, miRNA and mRNA to target cells and altering their function. Here, we provide an overview of what is currently known about EV composition and function in bone and muscle cells and discuss their role in mediating crosstalk between these two tissues as well as their role in musculoskeletal aging. (b). RECENT FINDINGS: Recent studies have shown that muscle and bone cells produce EV, whose protein, mRNA and miRNA cargo reflects the differentiated state of the parental cells. These EV have functional effects within their respective tissues but evidence is accumulating that they are also shed into the circulation and can have effects on distant tissues. Bone and muscle-derived EV can alter the differentiation and function of bone and muscle cells. Many of these effects are mediated via small microRNAs that regulate target genes in recipient cells. (c). SUMMARY: EV-mediated signaling in muscle and bone is an exciting and emerging field. While considerable progress has been made, much is still to be discovered about the mechanisms regulating EV composition, release, uptake and function in muscle and bone. A key challenge is to understand more precisely how exosomes function in truly physiological settings.