Podocyte-Specific Deletion of STAT3 in KLF4-Related Experimental Podocytopathy

Background: Podocyte loss and parietal epithelial cell activation are features of subtypes of glomerulonephritis and focal segmental glomerulosclerosis (FSGS). We recently reported that the podocyte-specific loss of Krüppel-like factor 4 (Klf4 ΔPod ) triggers dysregulated glomerular STAT3 activation, podocyte loss with parietal epithelial cell activation and proliferation, leading to FSGS. While pharmacological systemic STAT3 inhibition attenuated this phenotype, it remains unclear whether the detrimental effects of Klf4 loss is primarily a result of dysregulated STAT3 activation intrinsically in podocytes. Methods: Mice with the concurrent and conditional knockdown of Stat3 and Klf4 ( Klf4 ΔPod Stat3 ΔPod ) were generated and characterized. Expression arrays from kidney biopsies with various types of glomerular diseases, deposited in Nephroseq, were interrogated for glomerular expression of genes downstream of STAT3 signaling. Cell-specific modulation of STAT3 genes were determined using scRNA-seq-based proportional cell type deconvolution of bulk RNA-seq obtained from the Nephrotic Syndrome Study Network (NEPTUNE) FSGS and healthy controls. Results: Klf4 ΔPod Stat3 ΔPod mice demonstrated no significant podocyte loss, parietal epithelial cell activation and proliferation, FSGS lesions, albuminuria, kidney dysfunction, and tubulointerstitial fibrosis and inflammation compared to the Klf4 ΔPod mice. Klf4 ΔPod Stat3 ΔPod mice also exhibited less glomerular myofibroblasts (+α-SMA) as compared to Klf4 ΔPod mice. Overall survival was restored in Klf4 ΔPod Stat3 ΔPod mice as compared to Klf4 ΔPod mice. Interrogation of expression arrays from human kidney biopsies with renal vasculitis demonstrated a glomerular enrichment of genes involved in canonical STAT3 signaling as compared to healthy controls, which negatively correlated with eGFR. Deconvolution of the bulk RNA-seq data from NEPTUNE showed an enrichment of these STAT3 genes in podocytes as compared to other glomerular cell clusters. Conclusions: Collectively, these data demonstrate that inhibiting podocyte-specific STAT3 signaling was sufficient to counter the detrimental effects of Klf4 loss in podocytes, thereby preventing albuminuria, accelerated podocyte loss, activation and proliferation of parietal epithelial cells, FSGS lesions, and kidney failure.