Single-nucleus analysis reveals renal STAT1/CEBPB signaling as a modifiable relay of proinflammatory FGF23 effects in diabetic kidney disease

Background Circulating fibroblast growth factor 23 (FGF23) rises dramatically in chronic kidney disease, particularly in diabetic kidney disease (DKD). At high concentrations, and with declining Klotho, FGF23 has been linked to renal inflammation. The cell types and transcriptional programs mediating these off-target actions remain undefined. We asked whether the diseased kidney responds to FGF23 differently from the healthy kidney, and whether any disease-specific response could be targeted. Methods Male and female DBA/2J mice received streptozotocin or vehicle to induce DKD. On day 56, mice received a single dose intravenous injection of FGF23 (0.3 g) or vehicle, with tissue collected 1 h later for single-nucleus RNA sequencing, differential expression and regulon (inferred transcription factor activity) analysis. Candidate pathways were tested in precision-cut kidney slices using the CEBPB inhibitor ST-101. Results Streptozotocin-treated male mice developed early DKD with a 6-fold increase in urinary albumin/creatinine ratio and 50% higher blood urea nitrogen with preserved glomerular filtration rate. All major renal cell types were annotated. Canonical FGF23 signaling was intact in disease, with segment-specific target induction conserved in both conditions (e.g. Cyp24a1 in PT-S1 and DCT1). Superimposed on this were disease-restricted responses, including Wsb1 in DCT1 and Pdk4 in PT-S2, PST, DCT1 and DCT2. Regulon analysis revealed DKD-specific induction of CEBPB regulon activity by FGF23 across all analyzed tubular segments, and of STAT1 in several segments. Pre-treatment with a CEBPB inhibitor suppressed CEBPB activity, downstream NF-KB and pro-inflammatory gene sets, and immune-like cell abundance in diseased slices. Conclusion In the diabetic kidney, FGF23 engages a STAT1-CEBPB-NF-{kappa}B axis absent from healthy kidney and extending beyond its canonical Klotho-dependent target segments, identifying CEBPB as a potential treatment target for FGF23's pathological inflammatory actions.