Integrated Multiomics Analyses and Mendelian Randomization Identify the Macrophage-Endothelial Characteristics of Membranous Nephropathy

Background: Membranous nephropathy (MN) is recognized as an autoimmune glomerular disease that may progress to severe end-stage renal disease. In recent years, extensive investigations into molecular characteristics of MN have been conducted at bulk-transcriptome level. However, the single-cell transcriptomic and proteomic features of MN remain to be elucidated. Mendelian randomization (MR) serves as a methodology for establishing causal relationships between exposure factors and outcomes, offering robust evidence to bridge the transition from "associated genes" to "causal genes". Methods: Transcriptome data of MN glomeruli acquired from GEO databases were analyzed and immune infiltration was delineated. Olink proteomics assessed inflammatory proteins in peripheral blood of MN patients in our cohort. Single-cell analyses were conducted to pinpoint subclusters closely linked to the progression of MN. hdWGCNA was utilized to identify co-expression modules correlated with key subclusters. Finally, bidirectional MR was implemented to select module genes exhibiting causal relationship with MN. Results: MN patients exhibited an increase in monocyte and M1 macrophage infiltration within glomeruli. scRNA-seq uncovered an increased abundance of pro-inflammatory macrophages expressing VEGFA and CXCL8, alongside inflammatory endothelial cells (IECs) exhibiting a high level of CCL2 and CXCL2 in MN patients with massive proteinuria. The communication between pro-inflammatory macrophages and endothelial cells appeared to be dominated by VEGFA and CXCL8, while IECs demonstrated an autocrine proclivity for CCL2 and CXCL2. Proteomic analysis showed that inflammatory related proteins, such as MCP1 (CCL2) and IL8 were up-regulated in MN. MR revealed a potential causal relationship between SLC1A5, and the occurrence of MN (OR=1.4, p=0.02). Drivers of ferroptosis were significantly enriched in endothelial cells with elevated SLC1A5, accompanied by higher expression of CCL2 and CXCL2. Conclusion: This study elucidated the circulatory and tissue inflammation of MN from a multi-omics perspective and identified pivotal macrophage-endothelial phenotypes and their interactions. MR identified genes with a causal relationship to MN in the phenotype-associated modules, potentially impacted the onset and progression of MN through modulation of endothelial phenotypes. Funding: Government Support – Non-U.S.