Gap-junctional regulation of osteoclast function.

Previous research has shown that bone-resorbing osteoclasts contain connexin molecules that organize to hemichannel-forming connexons, which in turn form functional gap junctions in neighboring cells. So far only little is known about the role of gap junctions in osteoclasts. However, blocking of the gap-junctional communication inhibits bone resorption in vitro. Knockout mice deficient of Connexin-43, the major connexin in bone cells, show surprisingly little skeletal manifestations. Gap-junctional communication in osteoblasts and osteocytes is well documented and seems to be essential for the integrity of bone cells, as well as for the transfer of mechanical signals of bone loading. The role of gap junction in osteoclasts is unclear, so far, but some putative roles have been suggested, including their participation in osteoclast precursor fusion to multinucleated mature osteoclasts, communication in the bone multicellular unit in bone remodeling, osteoclast survival, and apoptosis.