A Novel, Scalable Rat Model of Glomerular Hyperfiltration CKD via Inducible Nephron Progenitor Cell Ablation

Background: Nephron overload is the final common pathway in chronic kidney disease (CKD) progression. Efficient, uniform models of glomerular hyperfiltration are scarce, impeding drug discovery. Conventional 5/6 nephrectomy models suffer from invasiveness, variability, and poor scalability. We developed a novel, non-invasive, scalable rat model of hyperfiltration CKD. Methods: We generated a novel CKD model using Six2-iCaspase9 transgenic rats expressing inducible Caspase9 via the nephron progenitor cell (NPC)-specific Six2 promoter. A single IP injection of a chemical inducer of dimerization (CID) was administered to pregnant dams at E13.5-E19.5 to induce targeted NPC apoptosis for graded nephron reduction. CID-treated rats (Tg+; CKD model) were compared with vehicle/non-transgenic controls (Tg-). Optimized in vitro fertilization (IVF) ensured scalable embryo production. CKD was assessed by serum creatinine (sCr), blood urea nitrogen (BUN), urine albumin-to-creatinine ratio (UACR), glomerular diameter, glomerulosclerosis, and interstitial fibrosis. eGFR was calculated (sCr, BUN, body weight). Results: Rats subjected to CID treatment at E17.5 developed characteristic features of CKD by 8 weeks of age. Tg+ had significantly higher BUN (p<0.01) and sCr (p<0.05) than Tg-. eGFR in Tg+ (1830±149μL/min, n=29) was 40% lower than Tg- (3062±190μL/min, n=8; p<0.0001). Tg+ also showed marked albuminuria, indicating glomerular damage. Glomerular diameter in Tg+ (163±7μm, n=16) was 1.9-fold greater than Tg- (84±3μm, n=25; p<0.0001), consistent with hypertrophy. Histology confirmed glomerulosclerosis and interstitial fibrosis. Furthermore, CID timing (E13.5-E19.5) allowed for graded control of CKD severity, ranging from neonatal lethality to milder phenotypes. IVF enabled reproducible, large-scale, uniform CKD model rat generation. Conclusion: The inducible NPC ablation model utilizing Six2-iCaspase9 transgenic rats provides a non-invasive, scalable, and severity-controllable platform that effectively recapitulates key aspects of glomerular hyperfiltration-associated CKD. This novel model, with its unprecedented control and scalability, promises to accelerate CKD research and drug discovery. Efficacy studies of SGLT2 inhibitors and GLP-1 receptor agonists in this model are underway. Funding: Government Support – Non-U.S.