#4970 SINGLE-CELL RNA SEQUENCING REVEALS THE MOLECULAR CHARACTERISTIC OF IGA-MCD
Authors: Wan Junli , Peng Liping , Chen Qilin , Jiang Huimin , Feng Xiaoqian , LI Qiu 
Published: June 2023

Abstract

Background and Aims
IgA nephropathy (IgAN) is the most common primary glomerular disease in children and adolescents worldwide, and is one of the major causes of end-stage renal disease in China. Minimal change disease(MCD) is the most common pathological type of nephrotic syndrome in children. In some rare cases, the renal pathology of these patient has IgA deposits in the mesangial regionns and diffuse fusion of podocyte foot process,which is called IgA-MCD. Previous studies have analyzed the characteristics of IgA-MCD from the aspects of clinical manifestations, pathological features, therapeutic response and prognosis, but the molecular mechanism of its occurrence and development has not been clarified. For the first time, single-cell transcriptome sequencing technology was used to compare IgA-MCD, IgAN and MCD, in order to describe the unique molecular characteristics of IgA-MCD and elucidate the molecular mechanism related to clinical manifestations. It lays the foundation for formulating more appropriate treatment plan and improving prognosis.

Method
Renal fine-needle puncture tissues were collected from 3 children with IgAN, 4 children with MCD, and 1 child with IgA-MCD in Children's Hospital of Chongqing Medical University, and adjacent normal tissues were collected from 1 child with renal tumor as control group. Children in the three disease groups had clinical manifestations of nephrotic syndrome, and nephrotic-level proteinuria at the time of sampling. High-throughput, unbiased single-cell transcriptome sequencing was performed on the above renal tissue samples, and the sequencing results were systematically compared and analyzed.

Results
By analyzing single-cell sequencing data, we systematically described single-cell transcriptome cell maps of renal tissues form children with nephrotic-level albuminuria with different pathologic types (IgAN, MCD, IgA-MCD). Twelve cell types, such as mesenchymal cells and podocytes, were defined by classical marker genes. By comparing the constituent ratio of renal cells and PC analysis of cell subsets in the control group and the three disease groups, it was found that IgA-MCD was closer to MCD. By comparing the differential genes of the three disease groups with those of the control group, we found that the number of differential genes in IgAN’s podocytes was significantly higher than that in the other two groups. Compared with the control group, HMGCS2 was significantly up-regulated in IgA-MCD, and cellular energy metabolism was enhanced. Through pairwise comparison among the three disease groups, it was found that there was no significant difference in genes in podocytes between IgA-MCD and MCD. Compared with IgAN, CXCL12 gene expression in IgA-MCD is significantly up-regulated, and CXCL12 can recruit immune cells and lead to cell damage.

Conclusion
The overall transcription profile of IgA-MCD is more similar to that of MCD. CXCL12 was specifically highly expressed in the podocytes of IgA-MCD, which may be used as a marker molecule for functional changes of IgA-MCD podocyte. IgA-MCD mesenchymal cells were significantly different from those in the other two disease groups. The significant up-regulation of CD81 may be a molecular signal that leads to the activation, proliferation, and secretion of more extracellular matrix of IgAN-MCD glomerular mesenchymal cells.We analyzed the associations and differences among IgAN, MCD and IgA-MCD at the single-cell transcriptome level, which provided a new perspective and insight for the follow-up study of the pathogenesis of the diseases.