MicroRNA Regulation in Osteocytes

Abstract

The role of microRNA (miR) regulation during the processes of bone homeostasis and remodeling has been a key research topic in recent years. Extensive work has gone into understanding the role of miR regulation in osteoblasts and osteoclasts; however, the role of miRs in osteocytes remains unclear. The aim of the present review is to describe the current knowledge regarding miR regulation in osteocytes. MiRs are key regulators of bone development and homeostasis, and the involvement of miRs in the regulation of osteocyte differentiation, viability, and function has recently been demonstrated. Findings from numerous studies have begun to identify various mechanisms of miR regulation in osteocytes. miRs have been shown to play a role in regulating osteocyte differentiation. For example, numerous miRs (including miR21, miR30, and miR23a) found to be upregulated during osteocyte differentiation target osteoblast-regulating mRNAs, whereas several downregulated miRs target key osteocyte-regulating genes. Further, miRs have been shown to regulate key signaling pathways controlling osteocyte viability and function. In particular, miR21 is involved in the survival signaling pathway downstream of connexin 43. Further, miR218, miR676, and miR324 regulate the expression of SOST/sclerostin, an osteocytic gene involved in the control of bone formation. Additionally, recent studies have demonstrated that miRs play a role in mediating cross-talk between osteocytes and other bone cells, as well as, with other musculoskeletal tissues including skeletal muscle and adipose tissue. miRs have been shown to be involved in regulating osteocyte differentiation, viability, and function. Further, recent studies have begun to highlight the potential involvement of miRs in mediating extracellular communication/regulation between osteocytes and other cells within the musculoskeletal system. However, more research on this topic is needed to determine the extent to which miRs regulate osteocytes and whether they are also involved in mediating cross-talk between musculoskeletal cells.