Vascular stiffening in aging females with a hypertension-induced HIF2A gain-of-function mutation.

Pulmonary arterial hypertension (PAH) is more prevalent in females than males; the causes of this sex difference have not been adequately explored. Gain-of-function (GOF) mutations in hypoxia-inducible factor 2α (HIF2A) lead to PAH and thrombotic consequences in patients and mice. Additionally, multiple emerging studies suggest that elevated systemic arterial stiffening (SAS) occurs in PAH; this could have critical prognostic value. Here, we utilized a HIF2A GOF mouse model to determine how SAS can be used as a prognosticator in sex-divergent PAH. We analyzed survival, vascular mechanics, and vascular phenotypes in young adult (8-16 weeks) and middle age (9-12 months) Hif2a GOF mice. We find that Hif2a heterozygous (HT) female mice, but not Hif2a HT male mice, exhibit poor survival, SAS upon aging, and decreased ability to withstand repeated physiological strain. Hif2a HT female mice also display thickening of the adventitial intima and increased collagen I and collagen III in all layers of the thoracic aorta. Our findings demonstrate differing PAH progression in female and male Hif2a GOF mice. Specifically, alterations in extracellular matrix (ECM) content led to vascular stiffening in aged females, resulting in poor survival. Moreover, we show that SAS emerges early in mice with PAH by coupling studies of vascular mechanics and analyzing vascular structure and composition. Importantly, we present a model for assessing sex differences in hereditary PAH progression and sex-specific prognosis, proposing that aortic stiffening can be used to prognosticate future poor outcomes in PAH.