Dysregulated Klotho and FGF23 signalling aggravates vascular remodelling in age-related pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a chronic condition of elevated pulmonary arterial pressure caused by vascular remodelling due to increased proliferation of pulmonary arterial smooth muscle cells (PASMC). Initially described as a disease primarily affecting young women, it now increasingly affects the elderly. Age-related pathomechanisms of PAH remain, however, unclear. In a translational approach combining preclinical disease models and analyses of human cohorts, we probed for a role of the anti-ageing protein Klotho, which acts as a co-receptor for fibroblast growth factor 23 (FGF23) in the pathogenesis of PAH.

Mice aged 114-117 weeks showed moderate spontaneous PAH with right ventricular (RV) hypertrophy and dysfunction relative to young mice aged < 40 weeks. This effect was further pronounced upon hypoxic exposure (10% O2) for 14 days. Histological sections showed pulmonary vascular wall thickening of small pulmonary arterioles. Similar findings were obtained in mice with a partial Klotho deficiency (kl/+) that developed RV systolic pressures (RVSP) of 72.58 ± 3.3 mmHg within two weeks of hypoxia. Aged mice and kl/+ mice had elevated plasma levels of FGF23, further amplified by hypoxic exposure. ELISA-based measurements in serum of patients from a cross-sectional study with PAH aged 60 years or older confirmed an increase in circulatory FGF23. Immunohistochemistry staining of lung tissue showed increased proliferative activity of PASMC in kl/+ mice, and recombinant FGF23 elevated proliferative activity of PASMC in vitro. The hyperproliferative response to FGF23 was prevented by siRNA-mediated knockdown of fibroblast growth factor receptor 1 in PASMC. In kl/+ mice, FGF23 neutralisation using an anti-FGF23 antibody reduced RVSP, improved RV dysfunction and RV hypertrophy and prevented pulmonary vascular remodelling.

Our findings identify the accumulation of FGF23 as novel mechanism of pulmonary vascular remodeling in PAH. Targeting dysregulated Klotho/FGF23 signalling may present a promising therapeutic strategy in elderly patients.