Department of Orthopedic Surgery, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA; Department of Joint Surgery, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guangdong, China.
Department of Orthopedic Surgery, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA.
J Steroid Biochem Mol Biol. 2020 May;199:105587. doi: 10.1016/j.jsbmb.2020.105587. Epub 2020 Jan 28.
Chronic kidney disease (CKD) is associated with elevated circulating fibroblast growth factor 23 (FGF23), impaired renal biosynthesis of 1α,25-dihydroxyvitamin D (1α,25(OH)D), low bone mass, and increased fracture risk. Our previous data with human mesenchymal stem cells (hMSCs) indicated that vitamin D metabolism in hMSCs is regulated as it is in the kidney and promotes osteoblastogenesis in an autocrine/paracrine manner. In this study, we tested the hypothesis that FGF23 inhibits vitamin D metabolism and action in hMSCs. hMSCs were isolated from discarded marrow during hip arthroplasty, including two subjects receiving hemodialysis and a series of 20 subjects (aged 49-83 years) with estimated glomerular filtration rate (eGFR) data. The direct in vitro effects of rhFGF23 on hMSCs were analyzed by RT-PCR, Western immunoblot, and biochemical assays. Ex vivo analyses showed positive correlations for both secreted and membrane-bound αKlotho gene expression in hMSCs with eGFR of the subjects from whom hMSCs were isolated. There was downregulated constitutive expression of αKlotho, but not FGFR1 in hMSCs obtained from two hemodialysis subjects. In vitro, rhFGF23 countered vitamin D-stimulated osteoblast differentiation of hMSCs by reducing the vitamin D receptor, CYP27B1/1α-hydroxylase, biosynthesis of 1α,25(OH)D, and signaling through BMP-7. These data demonstrate that dysregulated vitamin D metabolism in hMSCs may contribute to impaired osteoblastogenesis and altered bone and mineral metabolism in CKD subjects due to elevated FGF23. This supports the importance of intracellular vitamin D metabolism in autocrine/paracrine regulation of osteoblast differentiation in hMSCs.
慢性肾脏病（CKD）与循环成纤维细胞生长因子 23（FGF23）升高、肾脏 1α,25-二羟维生素 D（1α,25(OH)D）生物合成受损、骨量减少和骨折风险增加有关。我们之前用人骨髓间充质干细胞（hMSCs）的数据表明，hMSCs 中的维生素 D 代谢受其调控，并以自分泌/旁分泌的方式促进成骨细胞分化。在这项研究中，我们检验了 FGF23 抑制 hMSCs 中维生素 D 代谢和作用的假说。hMSCs 从髋关节置换术时废弃的骨髓中分离得到，包括两名接受血液透析的患者和一系列 20 名（年龄 49-83 岁）具有估算肾小球滤过率（eGFR）数据的患者。通过 RT-PCR、Western 免疫印迹和生化分析，分析 rhFGF23 对 hMSCs 的直接体外作用。体外分析显示，hMSCs 中分泌型和膜结合型αKlotho 基因的表达与分离 hMSCs 的患者的 eGFR 呈正相关。从两名血液透析患者中获得的 hMSCs 中，αKlotho 的组成型表达下调，但 FGFR1 没有下调。体外，rhFGF23 通过降低维生素 D 受体、CYP27B1/1α-羟化酶、1α,25(OH)D 的生物合成以及通过 BMP-7 信号传导，拮抗维生素 D 刺激的 hMSCs 成骨细胞分化。这些数据表明，hMSCs 中维生素 D 代谢失调可能导致 CKD 患者成骨细胞生成受损和骨矿物质代谢改变，原因是 FGF23 升高。这支持了细胞内维生素 D 代谢在 hMSCs 中成骨细胞分化的自分泌/旁分泌调节中的重要性。
