Soluble Alpha Klotho for Reversal of Renal Interstitial Fibrosis and Renal Regeneration: A Hypothesis Based on Developmental Biology and Preclinical Evidence

Background: Renal interstitial fibrosis represents the final common pathway of chronic kidney disease (CKD) irrespective of its cause. α-Klotho exists in three subfamilies (α, β, γ), with α-Klotho present in membrane-bound and soluble forms. The membrane-bound form plays a key role in phosphate and vitamin D metabolism via FGF23 signaling. The soluble form (sαKL) acts as a hormone with anti-inflammatory, antioxidant, tumor-suppressive, and proteolytic activities. In-utero, sαKL levels are high and promote renal hypertrophy and hyperplasia. These levels decline after birth and further with aging and CKD1. Methods: Reviewed preclinical studies evaluating the therapeutic effects of exogenous Klotho supplementation and gene therapy in animal models of CKD. This includes administration of recombinant human Klotho protein (rh-Klotho), intravenous Klotho-derived peptide (KP1), gene delivery using Klotho-carrying plasmids, and mesenchymal stem cells aimed at restoring fetal levels of sαKL. Outcomes included renal function parameters, histological assessments, and molecular markers of fibrosis and regeneration. Results: Administration of rh-Klotho (20 µg/kg/day for 8 weeks) improved glomerular filtration rate (GFR), reversed renal fibrosis, and upregulated BMP-7 expression2. KP1 localized selectively to injured kidneys and reduced fibrotic lesions3. Exogenous sαKL decreased albuminuria, serum creatinine, mesangial expansion, glomerular hypertrophy, and tubular interstitial fibrosis2,3. sαKL also increased BMP-7, which antagonized TGFβ1-induced epithelial-to-mesenchymal transition (EMT), a key process in fibrosis. Gene therapy using Klotho plasmids provided renal protection and reduced structural damage4. Developmental insights support that high fetal sαKL levels stimulate renal growth. [1] Takenaka T et al. Kidney Blood Press Res. 2023;48(1):326–337. [2] Yuan Q et al. Nat Commun. 2022;13:438. [3] Hajare AD et al. Mol Biomed. 2025;6:19. [4] Acta Pharmacol Sin. https://doi.org/10.1111/apha.14220 Conclusion: Supplementation of soluble α-Klotho in higher animal models at an equivalent dose for 8 weeks is necessary for the reversal of renal interstitial fibrosis. Mimicking fetal sαKL levels through such supplementation may stimulate renal regeneration in CKD and represents a promising therapeutic strategy.