Identification of PHACTR4 as A New Biomarker for Diabetic Nephropathy and Its Correlation with Glomerular Endothelial Dysfunction and Immune Infiltration

The pathophysiology of diabetic nephropathy (DN) is fundamentally dependent on glomerular endothelial cells (GECs), which are a crucial portion of the glomerular filtration barrier. This study aimed to identify biomarker candidates associated with GECs dysfunction in DN by combining microarray and single-cell sequencing dataset analysis.

Microarray dataset GSE30528 was downloaded from the Gene expression omnibus (GEO) database. Key gene sets for diabetic kidney disease (DKD) were selected by using weighted gene co-expression network analysis (WGCNA). Biomarker candidates were then identified using least absolute shrinkage and selection operator (LASSO) logistic regression. The single-cell sequencing data (GSE131882) was used to explore the biological functional differences in glomerular endothelium between the control and DKD groups. The diagnostic efficiency of the selected biomarker was tested in the Receiver operating characteristic (ROC) curve. Moreover, we used the single-sample gene set enrichment analysis (ssGSEA) to compare immune cell infiltration between DKD and control groups. RT-PCR was used to validate the selected gene expression in cultured glomerular endothelial cells under high glucose stimulation.

Results:

 Phosphatase and actin regulator 4 (PHACTR4) was ultimately selected as the key GEC-related biomarker in DKD. Significantly downregulated PHACTR4 mRNA expression was further validated in human glomerular endothelial cells (HGECs) under high glucose stimulation by using RT-PCR. The decreased PHACTR4 was found to be associated with abnormal endothelial proliferation and neo-angiogenesis. Additionally, immune infiltration analysis revealed that PHACTR4 was negatively associated with inflammatory infiltration, especially pro-inflammatory cells including activated CD4 and CD8 T cells, B cells, and Mast cells, indicating PHACTR4 downregulation may exacerbate inflammatory reaction.

PHACTR4 is a potential diagnostic marker for DKD and plays an essential role in aberrant glomerular endothelial proliferation and inflammation in DKD.