Abstract
Osteocyte is the most abundant cell type in bone, and the only cell type located inside the mineralized matrix. The striking structural design of bone predicts an important role for osteocytes in determining bone structure and function. Osteocytes are connected with each other via gap junctions and form a three dimensional cellular network in mineralized bone matrix. Recently, it has been shown that osteocytes are not only passive bystanders, but also have an active regulatory role in whole body phosphate and calcium metabolism. Osteocytes are cells which sense mechanical loading in bone. They respond to mechanical stimuli by producing and secreting several bioactive substances including nitric oxide and prostaglandins and thus transmit messages of loading to effector cells, like osteoblasts and osteoclasts. Present data suggest that osteocytes actively inhibit osteoclastic bone resorption. Whenever osteocytes die, this inhibitory effect is turned off and osteoclasts are activated. This mechanism of action could explain targeted remodeling in the region of stress induced microcracks happened. Osteocytes can also modulate osteoblasts function. In conclusion, osteocytes sense mechanical stimuli, transmit signals through cellular network and regulate osteoblast and osteoclast function during bone remodeling.
