Glomerular Endothelial Cells Are the Coordinator in the Development of Diabetic Nephropathy

Abstract

The prevalence of diabetes is consistently rising worldwide. Diabetic nephropathy is a leading cause of chronic renal failure. The present study aimed to explore the crosstalk among the different cell types inside diabetic glomeruli, including glomerular endothelial cells, mesangial cells, podocytes, and immune cells, by analyzing an online single-cell RNA profile (GSE131882) of patients with diabetic nephropathy. Differentially expressed genes in the glomeruli were processed by gene enrichment and protein-protein interactions analysis. Glomerular endothelial cells, as well as podocytes, play a critical role in diabetic nephropathy. A subgroup of glomerular endothelial cells possesses characteristic angiogenesis genes, indicating that angiogenesis takes place in the progress of diabetic nephropathy. Immune cells such as macrophages, T lymphocytes, B lymphocytes, and plasma cells also contribute to the disease progression. By using iTALK, the present study reports complicated cellular crosstalk inside glomeruli. Dysfunction of glomerular endothelial cells and immature angiogenesis result from the activation of both paracrine and autocrine signals. The present study reinforces the importance of glomerular endothelial cells in the development of diabetic nephropathy. The exploration of the signaling pathways involved in aberrant angiogenesis reported in the present study shed light on potential therapeutic target(s) for diabetic nephropathy.

Keywords: angiogenesis; cell crosstalk; diabetic nephropathy; glomerular endothelial dysfunction; single cell RNA analysis.

Figure 1

(A) UMAP plot from unsupervised clustering of 23,980 cells from kidney cortex of healthy subjects and patients with diabetic nephropathy. (B) Expression levels of representative genes from each cluster. (C) UMAP plot of the two subclusters of glomerular endothelial cells. (D) Heatmap of top 30 up- and down-regulated DEGs in GEC0. (E) Heatmap of top 30 up- and down-regulated DEGs of GEC1. (F) Pie chart of significantly enriched GO terms group of GEC1. (G) UMAP plot of podocytes in healthy and diabetic conditions. (H) Heatmap of DEGs of podocytes. (I) UMAP plot of the two subclusters of mesangial cells. (J) Heatmap of top 30 up- and down-regulated DEGs in MC0. (K) Heatmap of top 30 up- and down-regulated DEGs in MC1. (L) Pie chart of significantly enriched GO terms group from DEGs of MC1. P-value < 0.05 were considered statistically different.

Figure 2

(A) UMAP plot of the distribution of immune cells in different samples. (B) UMAP plot of four subclusters of immune cells. (C) Heatmap of top 30 up- and down-regulated DEGs in monocytes/macrophages. (D) Heatmap of top 30 up- and down-regulated DEGs in T lymphocytes. (E) Distribution of selected cell markers of monocyte/macrophage: (Upper) Presence of M1-like macrophage markers (ITGAX and CD86) and (Lower) M2-like macrophage markers (CD163 and MRC1). (F) Ligand-receptor interactions prediction network with DEGs from GEC1, MC1, monocytes/macrophages (MONO_MACRO), T lymphocytes, and top 500 expressed genes of podocytes, B lymphocytes, and plasma cells. In the circus, upregulated genes are labeled purple; downregulated genes labeled blue; top expressed genes in podocytes, B lymphocytes and plasma cells labeled black. The lines and arrowheads inside are scaled to indicate the correlations of the ligand and receptor. P-value < 0.05 were considered statistically different.