The Development of Treatment for Bone Defects in Maxilla Using Teflon Membran and the Analysis of Factors Promoting Maxillary Bone Regeneration

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Prostaglandin (PG) is well-known as a group of inflammatory factors and some of them have been reported to have anabolic effects on bone. Many researchers have demonstrated that the administration of PG,especially PGE_2 increases the volume of trabecular and cortical bone in vivo and promotes the differentiation of osteoblast in vitro. It is still not clear whether and how endogenous PG is associated with bone formation in vivo. We have already established a rat model in which osteogenesis can be seen in the tibial medullary cavity by injecting colchicine. Using this model, we examined the expression of the cyclooxygenase (COX) gene that is the synthase of PG from arachidonic acid and has been recently revealed to have two subtypes, a constitutive type (COX-1) and an inducible one (COX-2). During the process of osteogenesis, the gene expression of COX-1 as well as COX-2 was enhanced after colchicine injection in the early stage before bone formation was started. Only the COX-2 gene was elevated again later during the beginning of bone formation. Furthermore, the daily administration of indomethacin, an inhibitor of PG synthase, could reduce the bone mass induced by colchicine in the rat tibiae. These data indicate that endogenous PG is associated with the osteogenesis in this model. Moreover, the present study suggests that COX-2 and COX-1 would be involved in the induction and proliferation of the osteoblast precursor during the early stage of osteogenesis. COX-2 is likely to be more associated with the maturation of osteoblasts in the later stage, while COX-1 will have less contribution to bone maturation.