Effects of basic fibroblast growth factor on the remodeling of alveolar bone

为了维持健康的牙周组织，需要足够的牙槽骨支持量。牙周组织中成骨细胞和破骨细胞之间的细胞功能调控着连续的骨重塑。另一方面，我们已经证明局部应用成纤维细胞生长因子-2 （FGF-2）诱导显著的牙周组织再生。在这项研究中，我们研究了FGF-2对牙周组织破骨细胞生成的影响。免疫组织化学分析显示，在自然发生的牙周炎的比格犬牙周组织中，FGF-2分布在牙周韧带细胞、牙龈成纤维细胞和破骨细胞上。在体外实验中，我们用可溶性RANKL （NF-κB配体受体激活剂）刺激小鼠骨髓单核细胞（RAW264） 3天，成功诱导出多核破骨细胞。此外，我们证明在可溶性RANKL刺激下，FGF-2对RAW264细胞的破骨细胞形成没有直接影响。然而，有趣的是，fgf -2刺激的小鼠克隆牙周韧带细胞（MPDL-22）和牙龈成纤维细胞（MG/B6）的条件培养基对破骨细胞的形成有抑制作用，但不影响破骨细胞的成熟。用抗opg (osteoprotegerin) mAb预处理条件培养基后，这种抑制作用得以恢复。此外，FGF-2上调MPDL-22和MG/B6中OPG和RANKL mRNA的表达。这些结果表明，由牙周组织细胞产生的fgf -2诱导的OPG可以抑制牙周组织中破骨细胞的形成，从而支持牙槽骨的形成。

In order to maintain the healthy periodontal tissue, adequate supportive alveolar bone volume is required. Continuous bone remodeling is regulated by orchestrated cellular functions between osteoblasts and osteoclasts in periodontal tissue. On the other hand, we have already demonstrated that topical application of fibroblast growth factor-2 (FGF-2) induced significant periodontal tissue regeneration.In this study, we examined the effects of FGF-2 on osteoclastogenesis in periodontal tissues. Immunohistochemical analysis revealed that FGF-2 is distributed on the periodontal ligament cells, gingival fibroblasts and osteoclasts in the periodontal tissue of beagle dogs with naturally occurring periodontitis. In in vitro studies, we successfully induced multinucleated osteoclasts from murine myelomonocytic cells (RAW264) by stimulating the cells with soluble RANKL (receptor activator of NF-κB ligand) for 3 days. Furthermore, we demonstrated that FGF-2 had no direct effects on the osteoclast formation from RAW264 cells under the stimulation with soluble RANKL. Interestingly, however, the conditioned medium of FGF-2-stimulated murine clonal periodontal ligament cells (MPDL-22) and gingival fibroblasts (MG/B6) showed the inhibitory effects on the osteoclast formation, but did not influence the maturation of the osteoclasts. This inhibitory effect was restored by the pretreatment of conditioned medium with anti-OPG (osteoprotegerin) mAb. In addition, FGF-2 upregulated the OPG and RANKL mRNA expressions in MPDL-22 and MG/B6. These results suggest that FGF-2-induced OPG produced from periodontal tissue cells can inhibit osteoclast formation in the periodontal tissue and may in turn support the alveolar bone formation.