The expression of bone matrix protein matrix around #beta#-TCP particles implanted into bone

摘要

Tissue response around #beta#-tricalcium phosphate (#beta#-TCP) particles (150-300 #mu#m in diameter) implanted into rat tibiae was analyzed by in situ hybridization with digoxigenin-labeled procollagen #alpha#1(I) (COL), osteonectin, osteocalcin, and osteopontin (OPN) RNA probes. Specimens were collected at 3, 5, 7, and 10 days after the operation. Holes without implantation were used as control. In both the #beta#-TCP implanted and control groups, new bone was formed centripetally and all four kinds of mRNA were expressed in activated osteoblasts. A COL signal was expressed most strongly and widely, and was detected at the peripheral region of the hole at day 3. The other three mRNAs were also expressed in bone forming osteoblasts by day 7. However, in the earlier cell reaction stage, OPN expression in the #beta#-TCP implanted group was different than that in the control group: OPN mRNA was seen exclusively in the cells on the particles, and an OPN signal was detected n6t only in COL-positive cells, but also in COL-negative cells. The former cells may be osteoblasts and reflect the early process of bone formation on biomaterials. The latter cells may be macrophages and reflect foreign body reactions. Expression of these OPN mRNAs induced by implantation of #beta#-TCP may play a role in bone formation on the materials and in determining their biocompatibility.