title: Hydroxyapatite particles are capable of inducing osteoclast formation.
abstract: Hydroxyapatite (HA) coatings have been used to improve implant fixation by promoting bone formation around the prosthesis. A macrophage response to HA particulates has been noted around loosened HA-coated prostheses. As biomaterial wear particle-associated macrophages are known to be capable of differentiating into osteoclasts that are capable of bone resorption, we examined whether particulate HA could similarly induce macrophage-osteoclast differentiation. HA-associated macrophages were isolated from granulomas, formed by subcutaneous implantation of HA, and co-cultured with UMR 106 osteoblast-like cells in the presence of 1,25-dihydroxyvitamin D(3) for up to 14 days on glass coverslips and bone slices. HA-associated macrophage-osteoclast differentiation was evidenced by the formation of numerous multinucleated tartrate resistant acid phosphatase (TRAP)-positive cells which formed lacunar resorption pits on bone slices. Polymethylmethacrylate (PMMA) particle-associated macrophages, isolated from subcutaneous PMMA-containing granulomas, caused significantly more osteoclast formation and bone resorption than HA-associated macrophages. These results indicate that macrophages responding to HA particles are capable of osteoclast differentiation. They also suggest that particles derived from uncemented (HA-coated) implants are likely to induce less osteoclast formation and osteolysis than cemented implants.
authors.affiliation: Department of Pathology, University of Oxford, Nuffield Orthopaedic Center, Headington, Oxford OX3 7LD, UK.
authors.forename: A
authors.initials: A
authors.lastname: Sabokbar
authors.forename: R
authors.initials: R
authors.lastname: Pandey
authors.forename: J
authors.initials: J
authors.lastname: Díaz
authors.forename: J M
authors.initials: JM
authors.lastname: Quinn
authors.forename: D W
authors.initials: DW
authors.lastname: Murray
authors.forename: N A
authors.initials: NA
authors.lastname: Athanasou