Peptides and growth regulatory factors in bone

All bone is remolded by bone resorbing (osteoclasts) and bone forming (osteoblasts) cells that are under the regulatory control of local factors generated in the bone cell microenvironment. These local factors are comprised of peptides and nonpeptides, including arachidonic acid metabolites such as prostaglandins of the E series and the leukotrines. Most is known of the peptides the stimulate or inhibit osteoclastic bone resorption, but information is also now accumulating on the peptide growth factors that are incorporated into the bone matrix, released in an active form when bone is resorbed, and stimulate those cellular events that result in bone formation. In this article these control mechanisms are reviewed.