Lymphangiogenesis in renal fibrosis arises from macrophages via VEGF-C/VEGFR3-dependent autophagy and polarization

Ying Zhang,Gang Xu,Kun Wang,Conghui Zhang,Shuai Huang,Xinjun Liang,Peng Cheng,Yanyan Liu,Xiaoyan Chang,Yueqiang Li,Lixi Li,Qing Li

doi:10.1038/s41419-020-03385-x

Abstract

Inflammation plays a crucial role in the occurrence and development of renal fibrosis, which ultimately results in end-stage renal disease (ESRD). There is new focus on lymphangiogenesis in the field of inflammation. Recent studies have revealed the association between lymphangiogenesis and renal fibrosis, but the source of lymphatic endothelial cells (LECs) is not clear. It has also been reported that macrophages are involved in lymphangiogenesis through direct and indirect mechanisms in other tissues. We hypothesized that there was a close relationship between macrophages and lymphatic endothelial progenitor cells in renal fibrosis. In this study, we demonstrated that lymphangiogenesis occurred in a renal fibrosis model and was positively correlated with the degree of fibrosis and macrophage infiltration. Compared to resting (M0) macrophages and alternatively activated (M2) macrophages, classically activated (M1) macrophages predominantly transdifferentiated into LECs in vivo and in vitro. VEGF-C further increased M1 macrophage polarization and transdifferentiation into LECs by activating VEGFR3. It was suggested that VEGF-C/VEGFR3 pathway activation downregulated macrophage autophagy and subsequently regulated macrophage phenotype. The induction of autophagy in macrophages by rapamycin decreased M1 macrophage polarization and differentiation into LECs. These results suggested that M1 macrophages promoted lymphangiogenesis and contributed to newly formed lymphatic vessels in the renal fibrosis microenvironment, and VEGF-C/VEGFR3 signaling promoted macrophage M1 polarization by suppressing macrophage autophagy and then increased the transdifferentiation of M1 macrophages into LECs.

Highlights

Chronic kidney disease (CKD) has become a global public health concern
There was a similar effect in the adriamycin nephropathy model (ADR) (Fig. S1). These results demonstrated that lymphangiogenesis paralleled renal fibrosis, macrophage infiltration, and vascular endothelial growth factor-C (VEGF-C) expression
Lymphatic vessel markers are coexpressed with macrophages in vivo and in vitro To determine whether macrophages can be directly differentiated into lymphatic endothelial cells (LECs) in renal fibrosis, immunofluorescence double-labeling of macrophages (F4/80) and lymphangiogenesis markers (LYVE-1) was conducted to analyze colocalization in ureteral obstruction (UUO) (Fig. 3A) and ADR (Fig. 3B) mice, and the results showed that some LYVE-1+ lymphatic vessels were positive for F4/80

Summary

Introduction

The glomerular filtration rate decreases and patient life quality progressively declines, eventually resulting in Many factors, such as inflammation, endothelial/epithelial cell transdifferentiation into mesenchymal cells, oxidative stress, and myofibroblast recruitment, have been found to play important roles in the development of renal fibrosis. An increasing number of studies have shown that lymphatic vessels are passive drainage channels and actively participate in a variety of biological effects These vessels are essential for immune regulation, immune surveillance, and inflammatory responses and are new targets for immune-related disease intervention[3].

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Results

Conclusion