Action of Anabolic Factors on Bone Formation in Mice

描述(申请人提供)：体内注射甲状旁腺激素(PTH)可刺激实验动物和人类的新骨形成。虽然IGF-1介导了甲状旁腺激素在骨中的部分作用，但其他生长因子的作用尚未阐明。甲状旁腺素是钙代谢的重要调节剂，对骨骼也有分解代谢作用。与甲状旁腺激素类似，碱性成纤维细胞生长因子-2在啮齿动物体内应用时是一种有效的骨合成物质，也可以刺激破骨细胞的形成和骨吸收。我们发现甲状旁腺素增加了成骨细胞和骨器官培养细胞中成纤维细胞生长因子-2及其受体(FGFR)的表达。我们发现，短期应用成纤维细胞生长因子-2促进小鼠骨髓基质细胞PTH受体1、IGF-1和RUNX-2的表达，并促进矿化骨结节的形成。此外，我们的初步研究表明，PTH在小鼠骨髓培养中刺激破骨细胞形成、增加血清钙和促进体内骨形成的能力在FGF2基因缺失的小鼠中都显著降低，这表明内源性成纤维细胞生长因子-2在PTH在骨中的某些反应中起着重要的生理作用。目前尚不清楚FGF2-/-小鼠对甲状旁腺素的合成代谢反应降低是由于成骨细胞还是破骨细胞水平上的骨重建。初步研究表明，在分化条件下生长的骨髓基质细胞(来自两种基因型)对甲状旁腺素的cAMP反应相似。PTH通过激活RANKL刺激破骨细胞的形成。有趣的是，RANKL刺激破骨细胞形成和激活在破骨细胞形成中至关重要的p38MAP激酶的能力在FGF2-/-小鼠的骨髓培养中也受到了损害。这项资助的重点是确定内源性成纤维细胞生长因子-2在甲状旁腺素诱导的小鼠骨重建中的作用。总体假设是，内源性成纤维细胞生长因子-2是甲状旁腺素在骨中发挥最大合成代谢和反应作用所必需的辅助因子。甲状旁腺激素对内源性成纤维细胞生长因子-2的调节可能具有治疗意义。具体目的1：确定成纤维细胞生长因子-2缺乏是否调节甲状旁腺素的合成代谢反应。具体目标2a。探讨成纤维细胞生长因子-2缺乏对甲状旁腺素诱导的成骨细胞增殖、分化、凋亡和骨结节形成的影响。目的2b：研究FGF2缺乏对甲状旁腺素诱导的小鼠破骨细胞生成的影响。具体目标3：确定FGF2缺乏是否改变了关键的信号分子，这些信号分子介导了甲状旁腺素在骨中的诱导反应。这些研究结果有助于加深我们对甲状旁腺激素作用于骨的分子机制(S)的理解。 如果FGF2对甲状旁腺激素的合成代谢作用至关重要，那么对这种相互作用的分析可能会导致合成代谢治疗的新方法。

DESCRIPTION (provided by applicant): In vivo administration of parathyroid hormone (PTH) stimulates new bone formation in experimental animals and humans. Although IGF-1 mediates some of the effects of PTH in bone, the role of other growth factors has not been elucidated. PTH is an essential regulator of calcium metabolism and also has catabolic effects on bone. Similar to PTH, basic fibroblast growth factor (FGF-2) is a potent bone anabolic agent when administered to rodents in vivo and also stimulates osteoclast formation and bone resorption. We have shown that PTH increased FGF-2 and FGF receptor (FGFR) expression in cell cultures of osteoblastic cells as well as in bone organ cultures. We have shown that short term FGF-2 treatment of mouse bone marrow stromal cells increased PTH Receptor 1, IGF-1 and Runx-2 expression and mineralized bone nodule formation. Furthermore, our preliminary studies show that the ability of PTH to stimulate osteoclast formation in murine bone marrow cultures, to increase serum calcium and to increase bone formation in vivo are all significantly reduced in mice with disruption of the Fgf2 gene suggesting an important physiologic role for endogenous FGF-2 in some of the responses to PTH in bone. It is not clear whether the reduced anabolic response to PTH in the Fgf2-/- mice is due to effects on bone remodeling at the level of the osteoblast or the osteoclast. Preliminary studies show that the cAMP response to PTH is similar in marrow stromal cells (from both genotypes) grown under differentiation conditions. PTH stimulates osteoclast formation via activation of RANKL. Interestingly, the ability of RANKL to stimulate osteoclast formation and to activate p38MAP kinase that is important in osteoclast formation is also impaired in marrow cultures from the Fgf2 -/- mice. The focus of this grant is to determine the role of endogenous FGF-2 in PTH induced bone remodeling in mice. The overall hypothesis is that endogenous FGF-2 is a necessary co-factor for maximal anabolic and resportive effects of PTH in bone. Modulation of endogenous FGF-2 by PTH could have therapeutic implications. Specific Aim 1: To determine whether FGF-2 deficiency modulates the anabolic response to PTH. Specific Aim 2a. To assess whether FGF-2 deficiency affects PTH induced osteoblast proliferation, differentiation, apoptosis and bone nodule formation. Specific Aim 2b: To examine the effect Fgf2 deficiency on osteoclastogenesis in response to PTH in Fgf2-/- mice. Specific Aim 3: To determine whether Fgf2 deficiency alters key signaling molecules that mediate PTH induced responses in bone. The results of the proposed studies could increase our understanding of the molecular mechanism(s) of the effect of PTH on bone. If FGF2 is critical for the PTH anabolic effect, then analysis of this interaction could lead to a new approach to anabolic therapy