Elucidation of the mechanism of alveolar bone regeneration by controlled release of recombinant human FGF-2

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We analyzed biological mechanism of the bone regeneration induced by controlled release of FGF2 using gelatin hydrogel in mouse. The alveolar bone regeneration model have established in 2005 supported by Grant-in-Aids for Scientific Research from JSPS. Through 7-14 days after implantation of the gelatin hydrogel, PCNA index in the periosteum of the FGF-2 released group (experimental group) was significantly higher than the control group. And hyperplastic periosteum with positive responses of alkaline phosphatase activity was observed with callus formation in the experimental group. In situ hybridization was performed using DIG-labeled cRNA probes for alkaline phosphatase, osteocalcin, osteopontin, Fgfr-1, Fgfr-2 and Runx2 to detect osteoblast maturation and distribution of the Fgfr-1, Fgfr-2 and Runx2 expression in the FGF2 induced hyperplastic periosteum. Mature osteoblast expressing osteocalcin, osteopontin and alkaline phosphatase was observed on a surface of the callus and original … More bone. Beside, immature osteoblast expressing only alkaline phosphatase showed widespread distribution in the periosteum. Whereas, Fgfr-1 and Fgfr-2 signal were greater in mature osteoblast than immature osteoblast, and some spindle shaped Cells out of the periosteum also expressed Fgfr-1, Fgfr-2. Runx2 was colocalyzed in periosteum with the signals of Fgfr-1 and Fgfr-2. Furthermore, expression level of these genes in laser micro-dissected periosteum were analyzed by real time RT-PCR. In experimental group, Runx2, osteocalcin, osteopontin and alkaline phosphatase expression were significantly higher than control group. Fgfr-1 and Fgfr-2 expression level were also higher in the experimental group than those of the control group. It can be concluded that controlled release of FGF2 in periosteum promotes additive bone regeneration through callus formation as a result of anabolic effects of FGF2 not merely promoting osteogenic cell proliferation but also enhancement of bone matrix production. Moreover, in this study we showed that FGF2 up-regulates Runx2 expression revel in the tissue as with osteocalcin, osteopontin and alkaline phosphatase expression contrary to results of previous in vitro experiment reports. Less