by various types of cells, most notably osteoblasts (which secrete new bone) and osteoclasts (which break down bone); osteocytes are also present in bone.

Precursors to osteoclasts, called pre-osteoclasts, express surface receptors called RANK (receptor activator of nuclear factor-kappa B). RANK is a member of the tumor necrosis factor receptor (TNFR) superfamily. RANK is activated