FGF2 Isoforms in Bone and Phosphate Homeostasis

项目总结： 该项目的长期目标是确定成纤维细胞的高分子量异构体 生长因子2(HMWFGF2)参与骨关节病的发生。骨关节炎(OA)是最常见的一种 关节炎，对人类健康和医疗保健系统的成本有重大的负面影响。退化性 骨关节病是一种骨关节病，流行于患有X连锁低磷血症(XLH)和 在所有年龄较大的XLH患者中都很常见，是这些受试者发病的主要原因。HMWTG小鼠 表型复制发生严重骨性关节炎的XLHHyp小鼠同源基因。我们之前也发表过， HMWFGF2亚型在Hyp小鼠成骨细胞和骨细胞中高表达。我们最近发现的相关信息 研究表明，与Hyp小鼠相似，HMWTg小鼠随着年龄的增长逐渐发展为严重的骨性关节炎。与之相反的是小鼠 在成骨细胞系细胞中过表达低分子FGF2亚型(LMWTg)不会发生骨性关节炎。 我们的初步数据还显示，选择性消融FGF2HMW亚型的小鼠不会 与年龄较大的WT窝产仔相比，发生骨性关节炎。我们的初步研究表明机械论上的相关性 在HMWTg膝关节中FGF23/FGFR1/MAPK和BMP/Smad1/5/8表达上调，而在LMWTg关节中不表达。我们 因此，我们希望探索FGF23在HMWTG诱导的OA中的潜在作用，因为我们发表了HMW但是 而不是LMW FGF2转录调控FGF23。此外，骨性关节炎中的FGF23是一个研究不足的领域 FGF2异构体在骨性关节炎中调节FGF23的研究也可能影响这一领域。我们提供了新颖的初步方案 体内注射FGF23中和抗体可改善HMWTg小鼠的OA表型。 这些发现支持我们的总体假设，即HMWFGF2亚型通过 FGF23/FGFR1/MAPK信号通路。我们还希望研究LMWTG关节内稳态的机制。 和HMWKO小鼠，因为LMWFGF2似乎保护关节免受骨性关节炎的发展。我们的目标是：目标 1A：明确FGF23/FGFReceptor信号在HMWFGF2诱导骨关节病中的作用。目标1b： 确定低分子FGF2过度表达或选择性消融的功能效应 HMWFGF2亚型可抵抗小鼠的骨关节病进展。目标2：定义 HMWFGF2诱导骨关节病的机制(S)我们的初步体外研究表明 FGF23/成纤维细胞生长因子受体及其下游信号通路的不同激活对血管紧张素转换酶分解代谢的影响 HMWFGF2与LMWFGF2在关节动态平衡中的合成代谢作用。小鼠成软骨细胞株ATDC5 FGF2HMW和FGF2LMWcDNAs转导小鼠关节软骨细胞 载体、HMWTg和LMWTg小鼠将被用来询问独特的细胞内信号通路 对于HMW或LMW在发展或预防OA的发展中的作用。由于FGF2在骨关节炎中的作用是 有争议的研究同时支持FGF2的分解代谢和合成代谢作用，以及由于 FGF2在骨性关节炎中的亚型尚未被研究，我们的研究可能会对该领域产生重大影响。

Project Summary: The long-term objective of this project is to determine how the high molecular weight isoforms of Fibroblast growth factor 2 (HMWFGF2) contribute to osteoarthropathy. Osteoarthritis (OA) is the most common form of arthritis and has a major negative impact on human health and cost to the health care system. Degenerative osteoarthropathy, a form of OA is prevalent in young individuals with X-linked hypophosphatemia (XLH) and common to all older XLH individuals and is a major cause of morbidity in these subjects. HMWTg mice phenocopy the Hyp mouse homolog of XLH that develops severe OA. We also previously published that HMWFGF2 isoforms are overexpressed in osteoblasts and osteocytes of Hyp mice. Of relevance we recently published that similar to Hyp mice, HMWTg mice develop progressively severe OA with age. In contrast mice overexpressing low molecular weight FGF2 isoform (LMWTg) in osteoblast lineage cells do not develop OA. Our preliminary data also show that mice in which the FGF2HMW isoforms are selectively ablated do not develop OA compared with aged WT littermates. Of mechanistic relevance our preliminary studies show upregulation of FGF23/FGFR1/MAPK and BMP/Smad1/5/8 in HMWTg knee joints but not LMWTg joints. We therefore wish to explore the potential role of FGF23 in HMWTg induced OA since we published that HMW but not LMW FGF2 transcriptionally regulates FGF23. Furthermore, FGF23 in OA is an understudied area thus studies of FGF2 isoforms modulating FGF23 in OA could also impact the field. We provide novel preliminary data that in vivo administration of FGF23 neutralizing antibody ameliorates the OA phenotype in HMWTg mice. These findings support our overall hypothesis that HMWFGF2 isoforms contribute to OA via FGF23/FGFR1/MAPK signaling. We also wish to investigate the mechanism of joint homeostasis in LMWTg and HMWKO mice since LMWFGF2 appears to protect the joint from OA development. Our aims are: Aim 1a:Define the role of FGF23/FGFReceptor signaling in HMWFGF2 induces osteoarthropathy. Aim 1b: Determine the functional effects of overexpressing of low molecular weight FGF2 or selective ablation of HMWFGF2 isoforms to confer resistance against osteoarthropathy progression in mice. Aim 2: Define the mechanism(s) by which HMWFGF2 induces osteoarthropathy. Our preliminary in vitro studies suggest differential activation of FGF23/FGF receptors and downstream signaling pathways for the catabolic effects of HMWFGF2 versus anabolic effect of LMWFGF2 in joint homeostasis. Murine chondrogenic cell line ATDC5 transduced with FGF2HMW and FGF2LMW cDNAs and primary murine articular chondrocytes obtained from Vector, HMWTg and LMWTg mice will be used to interrogate intracellular signaling pathways that are unique for HMW or LMW in developing or preventing development of OA. Since the role of FGF2 in OA is controversial with studies supporting both catabolic and anabolic effects of FGF2 and since the potential role of FGF2 isoforms in OA has not been investigated, our studies could significantly impact the field.