Osteocyte calcium signaling - A potential translator of mechanical load to mechanobiology

Osteocytes are embedded dendritic bone cells; by virtue of their position in bone tissue, ability to coordinate bone building osteoblasts and resorbing osteoclasts, and sensitivity to tissue level mechanical loading, they serve as the resident bone mechanosensor. The mechanisms osteocytes use to change mechanical loading into biological signals that drive tissue level changes has been well studied over the last 30 years, however the ways loading parameters are encoded at the cellular level are still not fully understood. Calcium signaling is a first messenger signal exhibited by osteocytes in response to mechanical forces. A body of work interrogating the mechanisms of osteocyte calcium signaling exists and is presently expanding, presenting the opportunity to better understand the relationship between calcium signaling characteristics and tuned osteocyte responses to tissue level strain features (e.g. magnitude, duration, frequency). This review covers the history of osteocyte load induced calcium signaling and highlights potential cellular mechanisms used by osteocytes to turn details about loading parameters into biological events.