肾纤维化中VEGF-C/VEGFR3信号通过自噬调控巨噬细胞活化促进淋巴管新生的作用及机制研究

Renal fibrosis is the final outcome of the chronic kidney disease, a clear mechanism of its occurrence and development of prevention and treatment of chronic kidney disease is of great significance. Our previous study confirmed the presence of lymphangiogenesis in various pathological types of chronic kidney disease and was positively correlated with the degree of fibrosis. We further found that there was a positive correlation between lymphatic vessel numbers and macrophage infiltration in mouse renal fibrosis model , in vitro experiments also found that polarized macrophages expressed different degrees of lymphatic markers, suggesting that macrophages might directly transdifferentiated into lymphatic endothelial cells to promote lymphangiogenesis; On the other hand, autophagy is essential for proper macrophage activation, and lymphatic growth signal VEGF-C/VEGFR3 could regulate macrophage autophagy. It was speculated that VEGF-C/VEGFR3 in renal fibrosis can regulate the activation and transdifferentiation of macrophages through autophagy, and ultimately promote lymphangiogenesis. Therefore, this project is to be validated clinically, in vivo and in vitro from many aspects: 1) Macrophages in renal fibrosis can be transdifferentiated into lymphatic vessels, of which M1 macrophage activation is highly likely; 2) lymphangiogenesis signal VEGF-C/ VEGFR3 regulates macrophage activation and transdifferentiation; 3) The VEGF-C/VEGFR3 signal regulates macrophage activation and transdifferentiation via autophagy and identifies a specific source of lymphangiogenesis in renal fibrosis. This project provides new ideas and targets for the prevention and treatment of renal fibrosis.

肾纤维化是慢性肾脏病发展最终结局，明确发生发展机制对防治慢性肾脏病有重要意义。我们前期研究证实各种类型慢性肾脏病中存在淋巴管新生，与纤维化程度正相关，进而我们发现小鼠肾纤维化中淋巴管生成与巨噬细胞正相关，且有共定位，体外实验发现M1可表达淋巴管内皮细胞标记物，提示M1可能直接转分化为淋巴管内皮细胞；巨噬细胞活化与自噬有关，VEGF-C/VEGFR3信号又可调节巨噬细胞自噬。据此推测，VEGF-C/VEGFR3信号可通过下调自噬促进巨噬细胞向M1活化，进而转分化为淋巴管内皮细胞；为此，本项目拟从临床、体内、体外多角度验证：1）肾纤维化中M1较M0、M2更能转分化为淋巴管；2）VEGF-C/VEGFR3信号可调控巨噬细胞向M1活化，进而向淋巴管内皮细胞转分化；3）VEGF-C/VEGFR3信号通过下调自噬发挥以上作用。研究成果为肾纤维化防治提供新思路。

我国CKD患病率约为10.8%，且逐年增加，给社会和个人都带来巨大的负担；CKD最终发展为慢性肾脏病（ESRD），而肾纤维化是CKD向ESRD进展的共同通路。因此明确肾脏纤维化的机制有助于寻找阻断CKD向ESRD进展的有效策略。炎症在肾纤维化的发生发展中起着至关重要的作用，而淋巴管生成是炎症领域的一个新的研究热点。最近的研究揭示了淋巴管新生与肾纤维化之间的关系，但淋巴管内皮细胞(LECs)的来源尚不清楚。有报道巨噬细胞在其他组织中通过直接或间接的机制参与淋巴管生成，而我们认为巨噬细胞和淋巴内皮祖细胞在肾纤维化中有密切的关系。在本研究中，我们证实肾纤维化模型中存在淋巴管新生，并与纤维化程度和巨噬细胞浸润呈正相关，进一步发现巨噬细胞可转分化为淋巴管内皮细胞。与静息(M0)巨噬细胞和替代活化(M2)巨噬细胞相比，经典活化(M1)巨噬细胞在体内和体外更可能转分化为LECs。VEGF-C通过激活VEGFR3进一步增加巨噬细胞M1极化和向LECs转分化，机制是VEGF-C/VEGFR3通路的激活可下调巨噬细胞自噬，进而调控巨噬细胞表型。雷帕霉素诱导巨噬细胞自噬降低M1巨噬细胞极化和向LECs的分化。这些结果表明，在肾纤维化微环境中， VEGF-C/VEGFR3信号通过抑制巨噬细胞自噬促进巨噬细胞M1极化，进而增加M1巨噬细胞向LECs的转分化。这为肾纤维化提供了新的理论基础，有望成为新的干预靶点。