Dosage-Dependent Nephroprotective Effects of an ALK5 Inhibitor in the Unilateral Ureteral Obstruction (UUO) Mouse Model

Background: Renal fibrosis is a hallmark of chronic kidney disease (CKD) and an essential factor for progressive loss of kidney function and development of end-stage renal disease. The unilateral ureteral obstruction (UUO) mouse is a widely used surgery-induced model of CKD with rapid induction of renal inflammation and fibrosis. Here, we characterized the effect of the TGF-β type 1 receptor kinase/ALK5 inhibitor (ALK5i) on renal outcomes in the UUO mouse. Methods: Male C57BL/6J mice (9 weeks old) were randomised and stratified into study groups based on body weight and were either sham-operated or underwent UUO surgery. UUO mice received (PO, BID) vehicle or ALK5i (3, 10 or 30 mg/kg) for 8 days. Vehicle-dosed sham-operated mice served as controls. At termination, both kidneys were weighed, and the obstructed left kidney was processed for quantification of hydroxyproline (HP) histological markers of fibrosis (Col1a1, Col3a1), tubular injury (KIM-1) and macrophage infiltration (F4/80). Plasma was sampled for measurement of KIM-1 levels. Results: The UUO mouse demonstratedpronounced renal tubular injury, accompanied by extensive fibrotic remodelling, tubular injury, myofibroblast activation, and macrophage infiltration. ALK5i therapy dose-dependently attenuated fibrosis, inflammation, and tubular damage in the model. Kidney hydroxyproline (HP) content demonstrated strong correlation with the expression levels of Col1a1 and Col3a1, highlighting its utility as a biomarker of renal fibrosis. Conclusion: ALK5i exerted dose-dependent nephroprotective effects in the UUO mouse model. Given the rapid induction of fibrosis and inflammation, the UUO mouse is optimal for screening of compounds with potential anti-fibrotic and anti-inflammatory effects.