Klotho Hormone Reverses Aging Across Heart, Kidney and Gut in Mice

Aging tissues lose their capacity to self-renew, partly because circulating levels of α-Klotho — a hormone produced primarily by the kidney and known for its anti-aging properties — fall dramatically with age. This study provides systematic, multi-organ evidence that Klotho deficiency accelerates aging phenotypes and that supplementation can partially reverse them, acting through a defined molecular pathway.

The research team used three mouse groups: young wild-type (5–6 months), old wild-type (17–23 months), and old heterozygous Klotho-deficient mice (OKL+/−). All old groups received either saline or daily intraperitoneal soluble α-Klotho (0.01 mg/kg/day) for 10 weeks. BrdU was administered before sacrifice to label actively dividing cells. Serum Klotho fell more than 12-fold from young to old wild-type mice; OKL+/− mice had even lower levels. sKL supplementation measurably restored circulating Klotho, especially when started before 20 months.

In the small intestine — a high-turnover tissue — aging reduced BrdU-positive crypt cells and expanded reactive Paneth and Goblet cell populations. OKL+/− mice showed further expansion of these secretory cells. sKL significantly reduced Paneth and Goblet cell counts in OKL+/− mice and partially restored crypt proliferation. In the kidney, BrdU labeling of tubular epithelial cells dropped ~50% from young to old and dropped further in OKL+/− mice. Glomerulosclerosis scores in OKL+/− mice approached 50% moderate-to-severe involvement; sKL cut this to ~12% (p<0.001). Interstitial fibrosis, which nearly doubled in OKL+/− mice, was significantly reduced by sKL in both old groups.

In the heart — one of the least regenerative tissues in mammals — aging suppressed BrdU, Ki67, and phospho-histone H3 (pH3) cardiomyocyte markers, with OKL+/− showing even greater suppression. sKL treatment produced striking recoveries: ~5-fold increase in BrdU+ cardiomyocytes and ~4-fold in Ki67+ cardiomyocytes in OKL+/− mice. Echocardiography confirmed functional benefits: sKL significantly reduced left ventricular mass and improved diastolic function (E'/A') in OKL+/− mice, without meaningfully altering ejection fraction. Mechanistic analysis showed that sKL upregulates Sirt1, which in turn suppresses CHK2 — a checkpoint kinase that halts cell cycle progression in response to DNA damage — thereby permitting greater cellular proliferation. DNA damage markers (γ-H2Ax, ATM) were elevated in aged and Klotho-deficient tissues and reduced by sKL treatment.

The study is notable for demonstrating that a single circulating hormone influences stem cell and progenitor proliferation across organs with radically different regenerative rates, through a conserved Sirt1-CHK2 signaling axis. Implications for human aging and age-related organ dysfunction are significant, though translation from mouse models requires careful consideration.