title: Integrin subunit beta3 plays a crucial role in the movement of osteoclasts from the periosteum to the bone surface.
abstract: We have shown that, when mouse parietal bones were incubated in culture medium containing indomethacin, the number of tartrate-resistant acid phosphatase-positive osteoclasts (TRAP + OCs) on the bone surface was drastically reduced (down-regulation), and the number on the periosteal membrane adjacent to the resorbing surface was increased. Subsequent incubation of bones with prostaglandin E2 (PGE2) rapidly reversed these changes (up-regulation). In the work reported here, the osteoclast-associated integrin subunit beta3 was stained by immunohistochemistry. The beta3-positive osteoclast (beta3 + OC) population on freshly isolated bone was comprised of about 67% TRAP + OCs and 33% TRAP OCs. Like TRAP + OCs, beta3 + OCs were reduced in number on the surface of bones incubated with indomethacin, but, in contrast to the TRAP + OCs, beta3 + OCs were not seen on the periosteal membrane. Following up-regulation of TRAP + OCs with PGE2, large numbers of beta3 + OCs appeared on the bone surface and, again, were not seen on the periosteal membrane. Echistatin, a peptide that binds to the alphavbeta3 integrin on osteoclasts, was found to inhibit the up-regulation of TRAP + OCs in a dose-dependent manner but had no effect on the down-regulation of TRAP + OCs. Similarly, echistatin inhibited the upregulation of beta3 + OCs on the bone surface, and, under these conditions, beta3 + OCs were observed on the periosteal membrane. The addition of anti-beta3 antibody also inhibited the up-regulation of TRAP + OCs in response to PGE2. The association of beta3 protein expression with the up-regulated osteoclast and the inhibition of up-regulation by echistatin and by anti-beta3 antibody provide strong evidence that beta3 plays an essential role in the movement of osteoclasts from the membrane to the bone.
authors.affiliation: Charles Salt Research Centre, The Robert Jones and Agnes Hunt Orthopaedic and District Hospital NHS Trust, Oswestry, Shropshire, United Kingdom.
authors.forename: I
authors.initials: I
authors.lastname: Holt
authors.forename: M J
authors.initials: MJ
authors.lastname: Marshall
mesh_terms: D000135:Acid Phosphatase / Q000032:analysis; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D000911:Antibodies, Monoclonal; D015703:Antigens, CD / Q000276:immunology / Q000378:metabolism*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D039661:Integrin beta3; D016023:Integrins / Q000276:immunology / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D008808:Mice, Inbred CBA; D010010:Osteoclasts / Q000737:chemistry / Q000166:cytology* / Q000201:enzymology; D010120:Oxytocics / Q000494:pharmacology; D010294:Parietal Bone / Q000166:cytology*; D010455:Peptides / Q000494:pharmacology; D010521:Periosteum / Q000166:cytology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D010980:Platelet Membrane Glycoproteins / Q000276:immunology / Q000378:metabolism*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D039661:Integrin beta3; D016023:Integrins; D036341:Intercellular Signaling Peptides and Proteins; D010120:Oxytocics; D010455:Peptides; D010975:Platelet Aggregation Inhibitors; D010980:Platelet Membrane Glycoproteins; C057986:echistatin; D000135:Acid Phosphatase; D015232:Dinoprostone; D007213:Indomethacin