Action of Anbolic Factors on Bone Formation in Mice

描述（由申请人提供）：在实验动物和人体内给予甲状旁腺激素（PTH）刺激新骨形成。虽然IGF-1介导骨中甲状旁腺激素的一些作用，但其他生长因子的作用尚未阐明。甲状旁腺激素是钙代谢的重要调节因子，对骨骼也有分解代谢作用。与PTH类似，碱性成纤维细胞生长因子（FGF-2）是一种有效的骨合成代谢剂，在啮齿类动物体内使用时，也能刺激破骨细胞的形成和骨吸收。我们已经证明，在成骨细胞培养和骨器官培养中，甲状旁腺激素增加了FGF-2和FGF受体（FGFR）的表达。我们已经证明，短期FGF-2处理小鼠骨髓基质细胞增加PTH受体1、IGF-1和Runx-2的表达和矿化骨结节的形成。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、增加血清钙和增加体内骨形成的能力在Fgf2基因破坏的小鼠中都显着降低，这表明内源性FGF-2在骨骼中对PTH的一些反应中具有重要的生理作用。目前尚不清楚Fgf2-/-小鼠对PTH合成代谢反应的降低是由于成骨细胞或破骨细胞水平对骨重塑的影响。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）中cAMP对PTH的反应是相似的。PTH通过激活RANKL刺激破骨细胞形成。有趣的是，在Fgf2 -/-小鼠的骨髓培养中，RANKL刺激破骨细胞形成和激活p38MAP激酶（在破骨细胞形成中很重要）的能力也受到损害。本资助的重点是确定内源性FGF-2在甲状旁腺激素诱导的小鼠骨重塑中的作用。总的假设是，内源性FGF-2是骨中甲状旁腺激素最大合成代谢和反应作用的必要辅助因子。PTH调节内源性FGF-2可能具有治疗意义。特异性目的1：确定FGF-2缺乏是否调节PTH的合成代谢反应。具体目标2a。评估FGF-2缺乏是否影响甲状旁腺激素诱导的成骨细胞增殖、分化、凋亡和骨结节形成。特异性目的2b：在Fgf2-/-小鼠中，研究Fgf2缺乏对破骨细胞生成的影响。特异性目的3：确定Fgf2缺乏是否会改变骨中介导甲状旁腺激素诱导反应的关键信号分子。所提出的研究结果可以增加我们对甲状旁腺激素对骨骼影响的分子机制的理解。

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