Emerging roles of osteocytes in regulation of bone and skeletal muscle mass

Contrary to the popular perception that the bone is merely a structural organ, decades of research have established its functional importance in whole-body metabolism. Osteocytes, which comprise >80% of all bone cells, were also initially thought to be terminally differentiated dormant cells lacking metabolic functions. However, new research is increasingly providing evidence that osteocytes not only play a role in the structural integrity of the bone, but also have secretory functions which regulate other bone cells as well as other organs including skeletal muscle - the structural-mechanical neighbor of the bone - via paracrine, and endocrine pathways. However, the publicly available preclinical and clinical data pertaining to the factors secreted by osteocytes and their functions in the musculoskeletal system largely fail to reach a consensus. This review is thus aimed to objectively collate all information available in the public domain for efficient access by researchers in the field. We strongly believe that this review will help researchers in an unbiased design of therapeutic strategies for musculoskeletal disorders.