#3764 SINGLE-CELL RNA-SEQ REVEALS IMMUNE AND KIDNEY CELL TYPE–SPECIFIC MOLECULAR ASSOCIATIONS TO IGA NEPHROPATHY
Authors: Zeng Honghui , Wang Le , Yang Xiaoqiang , Luo Siweier , Zhou Yiming 
Published: June 2023

Abstract

Background and Aims
IgA nephropathy is the most common primary glomerulonephritis worldwide. There is growing evidence of host immunity is closely related to the pathogenesis of IgAN, but the detailed mechanism in the early stages of IgAN remain largely unknown. In this study, we applied single-cell RNA-seq technology to investigate the transcriptomic changes in PBMCs and kidney tissues of early stage IgAN patients at the single-cell resolution. This study aims to establish a immune and kidney cell landscape of IgAN, and offers new insights for the diagnosis and treatment of IgAN.

Method
In strict accordance to the admission criteria, collect peripheral venous blood and kidney samples of healthy donors and newly diagnosed IgAN patients, prepare single cell solution, verify cell viability by flow cytometry, and perform single-cell RNA-seq using a BD Rhapsody platform. Meanwhile, the clinical data of healthy donors and IgAN patients were collected and analysed. Finally, the correlation and association of differential expressed genes (DEGs) and cell clusters-identified by single-cell RNA-seq with the clinical data of IgAN were investigated.

Results
First, we established immune cells and kidney cells landscape of IgAN. The differentially expressed genes (DEGs) between the control group and IgAN were mainly concentrated in the NK cell-mediated cytotoxicity and cell killing pathways. Interestingly, we found significant decreases in NK cell numbers and cytotoxicity, and NK cell numbers and marker genes were negatively correlated with clinical parameters, including urinary protein creatinine ratio (UPCR) and serum galactose-deficient IgA1 and IgA. In contrast, B cell DEGs were enriched in different viral infection pathways, and one specific B cell subgroup showed inhibition of NFκB signaling, which was positively correlated with clinical parameters. In addition, a subpopulation of monocytes expressing interferon-inducing genes was positively associated with clinical severity of IgAN. In case of the kidney tissue, compared with the control group, mesangial cells of IgAN patients up-regulated extracellular matrix, transcription factors, kidney development and genes related to the regulation of Wnt signaling pathway. The expression of structural protein ITGA8 on mesangial cells was significantly decreased, indicating the mesangial cells were damaged in early IgAN. Pseudo-time analysis indicated that extracellular matrix-related genes were involved in mesangial cell lesion. We also found that the patie'ts' glomerular endothelial cells expressed high level of angiogenesis and VEGF- related genes. Moreover, podocytes of IgAN patients expressed genes of cytoskeletal recombination and FGFR activation.

Conclusion
We successfully established the single-cell landscapes of peripheral blood immune cells and kidney cells in early IgAN patients, which revealed changes in the number and status of immune cells and kidney cells closely related to clinical manifestations and phenotypic transformation. Our study offers new insights for the diagnosis and treatment of IgAN.