FGF2 Isoforms in Bone and Phosphate Homeostasis

项目摘要： 本项目的长期目标是确定成纤维细胞的高分子量亚型如何 生长因子2（HMWFGF 2）有助于骨关节病。骨关节炎（OA）是最常见的形式， 关节炎，并对人类健康和卫生保健系统的成本具有重大的负面影响。退行性 骨关节病是OA的一种形式，在患有X连锁低磷酸盐血症（XLH）的年轻个体中普遍存在， 常见于所有老年XLH个体，是这些受试者发病的主要原因。HMWTg小鼠 表型复制发展严重OA的XLH的Hyp小鼠同源物。我们之前也发表过， HMWFGF 2亚型在Hyp小鼠的成骨细胞和骨细胞中过表达。我们最近 HMWTg小鼠与Hyp小鼠相似，随着年龄的增长逐渐发展为严重的OA。相反， 在成骨细胞系细胞中过表达低分子量FGF 2同种型（LMWTg）不会发展成OA。 我们的初步数据还表明，选择性消融FGF 2 HMW同种型的小鼠， 与老龄WT同窝仔相比，我们的初步研究显示 FGF 23/FGFR 1/MAPK和BMP/Smad 1/5/8在HMWTg膝关节而非LMWTg关节中上调。我们 因此，希望探索FGF 23在HMWTg诱导的OA中的潜在作用，因为我们发表了HMW， 而不是LMW FGF 2转录调节FGF 23。此外，骨关节炎中的FGF 23是一个研究不足的领域， 在OA中调节FGF 23的FGF 2同种型的研究也可能影响该领域。我们提供新颖的初步 体内施用FGF 23中和抗体改善HMWTg小鼠中的OA表型。 这些发现支持了我们的总体假设，即HMWFGF 2亚型通过以下途径促进OA的发生： FGF 23/FGFR 1/MAPK信号传导。我们还希望探讨LMWTg关节内稳态的机制 和HMWKO小鼠，因为LMWFGF 2似乎保护关节免受OA发展。我们的目标是：目标 图1a：定义FGF 23/FGF受体信号传导在HMWFGF 2诱导骨关节病中的作用。目标1b： 确定过表达低分子量FGF 2或选择性切除 HMWFGF 2亚型赋予小鼠骨关节病进展抗性。目标2：定义 HMWFGF 2诱导骨关节病的机制。我们初步的体外研究表明 FGF 23/FGF受体和下游信号传导通路的差异活化， HMWFGF 2与LMWFGF 2在关节稳态中的合成代谢作用。小鼠软骨细胞系ATDC 5 用FGF 2 HMW和FGF 2 LMW cDNA转导的小鼠关节软骨细胞和从 载体、HMWTg和LMWTg小鼠将用于询问独特的细胞内信号传导途径 HMW或LMW在发展或预防OA发展中的作用。由于FGF 2在OA中的作用是 与支持FGF 2的分解代谢和合成代谢作用的研究存在争议， OA中的FGF 2亚型尚未研究，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.