Extracellular Vesicles as Communicators of Senescence in Musculoskeletal Aging

Extracellular vesicles (EVs), including exosomes and microvesicles, are released by numerous cell types. EVs are now acknowledged as playing a critical role in cell-cell communication in healthy aging as well as in age-related diseases. Recently it was shown that senescence, a key hallmark of aging, increases the secretion of EVs. Moreover, EVs can transport proteins and microRNAs (miRNAs) that are key components of the senescence-associated secretory phenotype (SASP). Here we review evidence that SASP-related miRNAs are involved in musculoskeletal degeneration with aging. Specifically, senescence-related miRNAs are elevated in EVs released by skeletal muscle myocytes and fibro-adipogenic progenitor cells with aging and disuse atrophy, respectively. Many of these same senescence-related miRNAs are detected in EVs from the synovial fluid of patients with osteoarthritis, and these miRNAs can contribute to cartilage degeneration. Finally, senescence-associated miRNAs are secreted from bone marrow-derived stem (stromal) cells impacting neighboring hematopoietic stem cells and circulating in the blood. The senescence-associated miRNA mir-34a, which is known to target Wnt and Notch pathways as well as the cell survival factors Sirt1 and Bcl2, is detected in EVs from human and animal subjects with muscle atrophy, bone loss, and osteoarthritis. These findings suggest that suppressing the secretion of EV-derived, senescence-related miRNAs, such as miR-34a, or increasing levels of competing endogenous long noncoding RNAs, such as MALAT1 that inhibit miR-34a, may help to improve musculoskeletal function with aging. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.