Research Work On Mechanism Of HA/TCP Biphasic Bioceramics' Osteoinductivity

Abstract Calcium Phosphate(CP) biomaterial's framework and component could be similar to natural bone by controlling the condition of produce. Previous study about CP showed that this kind of biomaterial had good biocompatibility. In recent year, not only CP 's osteocondutivity was founded, but also osteoindutivity. Some researcher founded that CP could induce new bone tissue formation in non-osseous site or environment. In order to achieve pefect results, a satisfying biomaterials were hoped to take advantage of body's natural ability to heal, especially to endow biomaterials with the biologically function to induce a tissue or organ regeneration. For advanced investgated the mechanism of CP's osteoinductivity, the HA/TCP biphase biocerimaic a kind of CP biomaterials were employed as test materials in this study, and different methods were used to study the heterotopic bone formation in porous HA/TCP ceramics implanted in pigs and rabbits respectively.Material and Methods HA/TCP was a kind of typical CP biomaterials,which was consistent of HA and TCP. According to ISO9003's standard, HA/TCP biphase bioceramic were fabricated into cylinder with Φ8mmX10mm.According to the osteoinductive concept, we chose intramuscular implantation (dorsal muscle) as the study model for osteoinduction, in which pigs and New Zealand rabbits were used. In the mean while, in vitro experiments were alsocarried out.Results In vitro system, bone marrow haversted from rabbits and pigs were collected and cultivated under culture medium comprised with stimuli(Dex lOnmol/L, P -GP lOmmol/L, AsAp 0.05mmol/L)which could induce mesenchymal stem cells (MSC) differentiate into osteoblast. Osteoblast were co-cultured with HA/TCP slice, enzyme histology showed that HA/TCP had reversible lesion effect on cell membrane system, but the period was very short. The enzyme activity of osteoblast recover normal at the end period of study. This showed that HA/TCP had good cell-compatibility.In vivo experiments, the new bone were noticed at 3 months post-implantatin in pig group and at 6 months post-implantation in rabbit group. The new bone were located at inner pores of HA/TCP implanters. At the edge of new bone, osteoblast were observed. In pig group, the MSC were founded by immunohistochemistry method. In the mean time, Cbfal positive cell were noticed, which is a special gene showing the mesenchymal stem cell covert to osteoblast. BMP-2 were expressed by osteoblast, osteocyte and pro-osteoblast. In study period, a kind of multi-nuclear grant cell were observed, which was located at the interface between the wall of HA/TCP material's pore and the mesenchymal. This kind of cell were characterized as osteocalst by immunohistochemistry and enzymehistochemistry method.Conclusion 1, HA/TCP biphase bioceramcis have good biocompatibility; 2. HA/TCP biphase bioceramics have osteoinductivity; 3. The model of new bone formation is intramember osteogenesis; 4, HA/TCP materials could provided fitting inon environment by degeneration, which could help MSC'sdifferentiation and new bone formation.