Protective role of early Tnfsf15 upregulation in limiting glomerular injury and proteinuria in experimental Alport Syndrome.

Alport syndrome is a progressive kidney disease caused by pathogenic variants in genes encoding type IV collagen, a major structural component of the glomerular basement membrane (GBM). Abnormal GBM architecture impairs filtration and triggers inflammation, fibrosis, and eventual kidney failure. Because disease progression is irreversible, identifying early molecular changes is essential for understanding disease onset. We performed glomerular single-cell RNA sequencing (scRNA-seq) in a Col4a5 G5X Alport mouse model at 5 weeks of age, prior to detectable proteinuria or GBM/podocyte abnormalities (pre-onset), and at 8 weeks, when mild proteinuria and structural defects emerged. Despite the early stage, scRNA-seq revealed widespread transcriptional alterations, most prominently in podocytes. Among genes upregulated at both time points, we identified Tumor Necrosis Factor Superfamily Member 15 (Tnfsf15), previously associated with kidney disease susceptibility but with unclear function. To determine its role in Alport syndrome, we generated Tnfsf15-deficient Alport mice. Tnfsf15 homozygous knockout mice exhibited increased proteinuria and exacerbated glomerular injury compared with Tnfsf15(+/+) Alport mice during early disease. These findings support a protective role for Tnfsf15 in the early stages of Alport syndrome, mitigating proteinuria and limiting glomerular injury.