白介素-17通路调控骨髓来源的纤维细胞和间充质干细胞参与肾脏间质纤维化的机制研究

Progressive tubulointerstitial fibrosis is the final common pathway for all kidney diseases leading to chronic renal failure. Recently, bone marrow derived cells are reported to be involved in the progression of renal fibrosis by regulating the local pro-inflammatory or pro-fibrosis environment and the injury/repairment of resident glomerular and tubular cells. However, the underlining mechanism is still poorly understood. In previous study, we have demonstrated that the number of bone marrow derived cells in kidney is significantly elevated in patients with chronic kidney disease. In addition, interleukin-17 receptor A on bone marrow derived cells contributes to the accumulation of bone marrow derived cells in kidney and progression of renal fibrosis. Bone marrow derived fibrocytes are candidates for participating in organ fibrosis and microvesicles secreted by mesenchymal stem cells protect against chronic kidney injury. We hypothesized that IL-17A/IL-17RA pathway is involved in renal fibrosis by regulating the differentiation, infiltration and activation of fibrocytes and inhibiting the secretion and function of protective mesenchymal stem cells derived microvesicles. We therefore propose to investigate the role of IL-17A/IL-17RA pathway in murine Il17ra-/- bone marrow transplantation and unilateral ureteral obstruction model and patients with chronic kidney disease. The findings of this project will contribute to the development of renal fibrosis theory and may become novel therapeutic targets in the treatment of pro-inflammatory processes in renal fibrosis.

肾脏间质纤维化是各种慢性肾脏病进展至终末期肾病的最后共同途径。骨髓来源细胞通过调节肾脏炎症微环境和肾脏固有细胞的损伤-修复机制参与肾脏间质纤维化过程，但是其精细调控机制尚未明确。申请者前期研究表明慢性肾脏病患者肾脏组织中大量骨髓来源细胞浸润；细胞表面白介素17受体A介导骨髓来源细胞在肾脏中的积聚参与肾脏间质纤维化。骨髓来源的纤维细胞（fibrocyte）是肾脏中成纤维细胞重要来源，骨髓来源的间充质干细胞通过分泌细胞外微囊泡样结构（microvesicles）参与肾脏损伤修复。本研究拟从临床、细胞和动物三个层面，采用白介素17受体A敲除小鼠和骨髓移植嵌合体模型，探讨白介素17通路调控骨髓来源纤维细胞的分化、募集和激活以及抑制间充质干细胞分泌microvesicles造成肾脏固有细胞损伤-修复机制紊乱，参与肾脏纤维化进程。本课题将丰富和发展肾脏纤维化理论，积极探索延缓或阻断肾脏纤维化新的靶点。

肾脏间质纤维化是各种慢性肾脏病进展至终末期肾病的共同途径。骨髓来源细胞参与肾脏间质纤维化过程，但是其精细调控机制尚未明确。我们发现CKD患者血浆中IL-17A水平增加，与患者血肌酐、尿素、白蛋白等临床指标和肾脏预后相关。单侧输尿管梗阻模型中Fibrocyte数量和相关因子CXCL12、 PDGF、Semaphorin7A增加。IL-17A可以促进肾小管上皮细胞分泌Fibrocyte相关因子和纤维化相关蛋白。他米巴罗汀可以通过抑制Th17细胞分化，下调UUO模型Fibrocyte数量和Fibrocyte相关因子，改善UUO模型肾脏纤维化。我们成功建立小鼠间充质干细胞培养体系，分离鉴定出间充质干细胞分泌的exosome。小鼠间充质干细胞和其分泌的exosome能有效减轻UUO模型肾脏纤维化，但经IL-17A刺激后保护效应无进一步改变。在老龄小鼠缺血再灌注损伤后慢性纤维化模型中，我们发现肾脏三级淋巴结构（Tertiary lymphoid organs, TLO）增加，TLO相关因子CXCL13、CCL19、LTα、LTβ和IL-17A表达增加，IL-17A基因敲除小鼠肾脏TLO面积和相关因子减少，纤维化水平下降。新型趋化因子CXCL16可以介导IL-17A分泌细胞进入病变组织。我们发现CKD患者血清中CXCL16增加，与患者临床指标、肾脏中炎症细胞浸润程度和肾脏预后相关。IFNγ通过NF-κB通路促进人HK2细胞分泌CXCL16。CXCL16促进Jurkat T细胞的迁移，并促进人肾小管上皮细胞分泌促纤维化蛋白Fibronectin。综上所述，本研究结果证实IL-17A通路可以介导骨髓来源纤维细胞的分化、募集和激活，参与肾脏TLO形成过程，在肾脏纤维化过程中在发挥重要作用；CXCL16通路参与慢性肾脏病炎症细胞的趋化和浸润过程，加重肾小管上皮细胞损伤。