Abstract
Chronic kidney disease (CKD) is associated with progressive renal dysfunction, Klotho deficiency, and activation of profibrotic signaling. This study evaluated the functional and molecular effects of kidney-directed adeno-associated virus serotype 9 (AAV9)-mediated human Klotho delivery in experimental CKD. Forty-eight male mice were studied in six groups: sham, untreated 5/6 nephrectomy, empty vector, low- and high-dose AAV9-Klotho, and recombinant Klotho. Vector was administered via the renal vein at week 4. The primary endpoint was week-16 serum creatinine, analyzed using a baseline-adjusted mixed model for repeated measures. High-dose AAV9-Klotho was associated with lower serum creatinine than empty vector (adjusted difference, −20.6 µmol/L; 95% confidence interval, −33.3 to −7.9; p = 0.0018), with concordant changes in blood urea nitrogen, proteinuria, and urinary albumin-to-creatinine ratio. Human Klotho expression increased with vector dose, accompanied by recovery of endogenous mouse Klotho. Fibrosis-associated and inflammatory markers, transforming growth factor-β receptor I abundance, and phosphorylation of mothers against decapentaplegic homologs 2 and 3 (Smad2/3) were lower after treatment, whereas transforming growth factor-β1 (TGF-β1) abundance remained unchanged. These findings associate kidney-directed AAV9-Klotho delivery with improved renal-function measures and modulation of TGF-β1/Smad2/3 signaling in experimental CKD. Histological antifibrotic efficacy and direct receptor-level mechanisms remain unconfirmed.