title: Effects of geometry of hydroxyapatite as a cell substratum in BMP-induced ectopic bone formation.
abstract: Three different types of porous hydroxyapatite with pore sizes of 100-200 micrometer in diameter-porous particles of hydroxyapatite (PPHAP), porous blocks of hydroxyapatite (PBHAP), and honeycomb-shaped hydroxyapatite (HCHAP)-were compared in terms of their abilities to induce osteogenesis when implanted subcutaneously with recombinant human BMP-2 into rats and extracted at 1, 2, 3, and 4 weeks. Histologically, direct bone formation occurred in PPHAP and PBHAP while only endochondral ossification took place in HCHAP. Interestingly, cartilage in the central zones and bone in the orifice zones of the tunnels of the HCHAP were observed at 2 weeks. After 3 weeks, the cartilage disappeared and bone formation occurred throughout the inner surface of the tunnels of the HCHAP, always leaving space for capillaries within the tunnels. Alkaline phosphatase activity and osteocalcin content were the highest in HCHAP among the three hydroxyapatite implants. These results clearly indicate that BMP-induced bone formation is highly dependent on the geometry of the carrier, which provides feasible structural factors for vascularization.
authors.affiliation: Department of Biochemistry, School of Dentistry, Hokkaido University, N-13, W-7, Kita-Ku, Sapporo, 060-8586, Japan.
authors.forename: Q M
authors.initials: QM
authors.lastname: Jin
authors.forename: H
authors.initials: H
authors.lastname: Takita
authors.forename: T
authors.initials: T
authors.lastname: Kohgo
authors.forename: K
authors.initials: K
authors.lastname: Atsumi
authors.forename: H
authors.initials: H
authors.lastname: Itoh
authors.forename: Y
authors.initials: Y
authors.lastname: Kuboki
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001672:Biocompatible Materials / Q000737:chemistry*; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000008:administration & dosage*; D017931:DNA Primers / Q000235:genetics; D004343:Drug Implants; D017886:Durapatite / Q000737:chemistry*; D006801:Humans; D008297:Male; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D015675:Osteocalcin / Q000235:genetics / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects*; D010316:Particle Size; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000008:administration & dosage; D016212:Transforming Growth Factor beta
chemical_list: C525718:BMP2 protein, human; D001672:Biocompatible Materials; C525720:Bmp2 protein, rat; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D017931:DNA Primers; D004343:Drug Implants; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D015675:Osteocalcin; D017886:Durapatite; D000469:Alkaline Phosphatase