NPP1对成纤维细胞生长因子23代谢调控作用的研究

Fibroblast growth factor 23 (FGF-23) is a major phosphaturic hormone. The regulatory mechanism of FGF-23 metabolism remains uncovered. FGF-23 is closely related to the occurrence of several metabolic bone diseases and the prognosis of chronic kidney disease (CKD). The patients of autosomal recessive hypophosphatemic rickets 2 (ARHR2) and CKD share some common clinical features, which are ectopic calcification of soft tissue and obviously elevated serum FGF-23. Based on the previous studies, we hypothesized: 'the nucleotide pyrophosphatase phosphodiesterase 1(NPP1) and pyrophosphate (PPi) may play an important role on regulation of FGF-23 metabolic coupling'. ENPP1-/-, Dmp1-Cre-ENPP1-/- and CKD mice model, as well as osteoblasts liked cells will be involved in our study, to detect the changes of metabolic coupling for FGF-23 production and cleavage with NPP1/PPi intervention. The trigger effects of iron-deficiency on NPP1/PPi-FGF-23 regulatory axis in CKD model will also be investigated. This study will bring to light on the new intervention target for a group of disorders (e.g. CKD, atherosclerosis) which characterized by elevated FGF-23 level and ectopic calcification.

成纤维细胞生长因子23（Fibroblast growth factor 23, FGF-23）是重要的磷调节激素，目前其代谢相关调控机制并未完全阐明。FGF-23与多种代谢性骨病发生和慢性肾脏病（CKD）的预后密切相关。本课题根据常染色体隐性遗传性低血磷性佝偻病（ARHR2）和CKD患者软组织异位矿化和血FGF-23水平显著升高的共同临床特征，提出了“焦磷酸酶磷酸二酯酶1（NPP1）/焦磷酸盐（PPi）调控FGF-23代谢耦联平衡”的研究假设。将通过在体（ENPP1-/-、Dmp1-Cre-ENPP1-/-和CKD模型）和离体(成骨样UMR-106细胞系)研究NPP1/PPi对FGF-23代谢耦联的调控作用，并在CKD模型中观察缺铁对NPP1/PPi调控FGF-23代谢失衡的触发作用。本研究将为以FGF-23代谢失衡和异位钙化为特征的疾病(如动脉粥样硬化等)的防治提供新线索。

磷是人体必需元素，在细胞生理和骨质矿化中发挥重要作用，磷稳态是维持机体生理功能所必需。成纤维细胞生长因子23(Fibroblast growth factor -23，FGF-23) 是一种重要的磷调节因子，与低血磷性佝偻病、慢性肾脏疾病和动脉粥样硬化等多种疾病的发生密切相关。NPP1是一种浆细胞膜糖蛋白，其由核苷酸内焦磷酸酶/磷酸二酯酶 1(ectonucleotide pyrophosphatase/phosphodiesterase 1 , ENPP1)基因编码，主要生理作用为水解三磷酸核苷酸 (Adenosine triphosphate，ATP)产生焦磷酸盐（pyrophosphate, PPi）。ENPP1基因失活突变会引起2型常染色体隐性遗传低血磷佝偻病（ARHR2），该病特征性表型为低磷血症、佝偻病，FGF-23 水平升高，也可伴有异位矿化。 本课题拟通过体内及体外试验，探索NPP1蛋白对FGF23的代谢调控机制，为ARHR2及FGF23升高相关疾病提供治疗靶点。1.本课题在国内首次报道3例ARHR2家系，建立并完善了患者或其家系成员的临床资料库，为该罕见骨病的诊治提供了参考。同时，本研究对患者进行了遗传学检测及基因突变的体外功能验证，丰富了世界低血磷性佝偻病的疾病谱，并首次提出，ARHR2的致病机制与NPP1蛋白催化功能的失活密切相关。2.本课题利用 CRISPR/Cas9技术成功构建ENPP1-Floxp小鼠，并将其与骨组织特异性表达的DMP1-Cre 小鼠交配，在世界上首次构建ENPP1骨特异性敲除的小鼠模型，这对于ENPP1对骨中FGF23水平的调控机制的研究有重要意义。 3.本研究通过体内及体内实验探索NPP1对FGF23的代谢调控机制，发现NPP1有可能通过调控嘌呤能信号转导系统，进而调控其下游的炎症反应及钙离子内流而影响FGF23的表达。本研究揭示了2型常染色体隐性遗传低血磷佝偻病的致病机制，并为ARHR2及FGF23升高相关疾病的治疗提供潜在治疗靶点。4. 本课题通过在体和离体实验发现，非选择性2型嘌呤能受体抑制剂PPADS可以抑制NPP1失活导致的FGF23升高。说明2型嘌呤能受体可能是ARHR2的潜在治疗靶点。