Kubota K, Iseki S, Kuroda S, Oida S, Iimura T, Duarte W R, Ohya K, Ishikawa I, Kasugai S
Department of Periodontology, Hard Tissue Engineering, Tokyo Dental and Medical University, Japan.
Bone. 2002 Oct;31(4):465-71. doi: 10.1016/s8756-3282(02)00852-9.
Bone morphogenetic protein family members (BMPs) are essential signaling molecules during limb development and, in this process, fibroblast growth factor family members (FGFs) cooperate with BMPs. FGFs also exert anabolic effects in bone when systemically or locally applied. Thus, it is likely that the cooperation with FGFs also occurs in BMP-induced ectopic bone formation and that the exogenous FGF application would promote this bone formation. In the present study, after subcutaneously implanting recombinant human BMP-2 (rhBMP-2) in rats, we examined the expression of FGF-4 and FGF receptors (FGFRs) mRNAs and the effect of exogenous recombinant human FGF-4 (rhFGF-4) on bone formation. Three days after implantation, the pellets containing rhBMP-2 were surrounded by fibroblastic mesenchymal cells; on day 7, cartilage tissue appeared; on day 10, hypertrophic chondrocytes and a small amount of mineralized tissue were observed; and, on day 14, the amount of mineralized tissue increased. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that FGF-4 expression appeared at early stages (days 3 and 7) and its expression decreased at later stages (days 10, 14, and 21), whereas FGFRs were expressed continuously. In situ hybridization revealed that, on days 3 and 7, FGF-4, and FGFR subtypes 1 and 2 (FGFR-1 and FGFR-2) were expressed in mesenchymal cells and chondrocytes, and in the area of alkaline phosphatase (ALP) expression. On day 10, FGF-4 was not detected, whereas the expression of FGFR-1 and FGFR-2 was detectable in the area of alkaline phosphatase (ALP) expression. Injection of rhFGF-4 on days 2, 3, and 4 enhanced the mineralized tissue formation induced by rhBMP-2; however, neither rhFGF-4 treatment on days 6, 7, and 8 nor rhFGF-4 treatment on days 9, 10, and 11 influenced the amount of rhBMP-2-induced mineralization. Our results indicate that FGF-4 and FGFR signals play important roles during rhBMP-2-induced bone formation. We further suggest that the combination of rhBMP-2 and rhFGF-4 would be useful for bone augmentation.
骨形态发生蛋白家族成员（BMPs）是肢体发育过程中必不可少的信号分子，在此过程中，成纤维细胞生长因子家族成员（FGFs）与BMPs协同作用。当全身或局部应用时，FGFs在骨骼中也发挥合成代谢作用。因此，在BMP诱导的异位骨形成中，可能也存在与FGFs的协同作用，并且外源性应用FGFs会促进这种骨形成。在本研究中，将重组人BMP-2（rhBMP-2）皮下植入大鼠后，我们检测了FGF-4和FGF受体（FGFRs）mRNA的表达，以及外源性重组人FGF-4（rhFGF-4）对骨形成的影响。植入后3天，含有rhBMP-2的小球被成纤维细胞间充质细胞包围；第7天，出现软骨组织；第10天，观察到肥大软骨细胞和少量矿化组织；第14天，矿化组织量增加。逆转录-聚合酶链反应（RT-PCR）分析显示，FGF-4表达在早期阶段（第3天和第7天）出现，后期阶段（第10天、第14天和第21天）表达下降，而FGFRs持续表达。原位杂交显示，在第3天和第7天，FGF-4以及FGFR亚型1和2（FGFR-1和FGFR-2）在间充质细胞、软骨细胞以及碱性磷酸酶（ALP）表达区域表达。第10天，未检测到FGF-4，而在碱性磷酸酶（ALP）表达区域可检测到FGFR-1和FGFR-2的表达。在第2天、第3天和第4天注射rhFGF-4可增强rhBMP-2诱导的矿化组织形成；然而，在第6天、第7天和第8天进行rhFGF-4处理，以及在第9天、第10天和第11天进行rhFGF-4处理，均未影响rhBMP-2诱导的矿化量。我们的结果表明，FGF-4和FGFR信号在rhBMP-2诱导的骨形成过程中发挥重要作用。我们进一步认为，rhBMP-2和rhFGF-4联合应用对骨增量将是有用的。
