Apr 10, 2020
The skeleton adapts to mechanical usage and mechanical loading promotes bone formation and remodeling. Although most bone cells are involved in mechanosensing, it is well accepted that osteocytes are the principal mechanosensory cells. Osteocytes are embedded inside the bone mineral matrix and have stellate morphology with small cell body and long dendritic processes. The long dendritic processes of osteocytes form a network not only connecting the neighboring osteocytes, but also the cells on the bone surface, such as osteoblasts and osteoclasts. Recently, morphological studies also show the connection of osteocytes with bone marrow and blood vessels. The osteocyte has been perceived as the center of bone remodeling by coordinating both osteoblast and osteoclast function, and also as the initiator of bone remodeling by sensing the bone matrix. Osteocyte cell body and processes are surrounded by fluid-filled space, forming an extensive lacuno-canalicular network. Various studies suggest that flow of interstitial fluid driven by extravascular pressure is a likely stress-related factor that transmits mechanical stimulation to bone cells. Dendritic processes of osteocytes are postulated as the mechanical sensory region on osteocytes. The mechanisms by which osteocytes sense and respond to mechanical loading and unloading in osteocytes are active research focuses in many laboratories.