Lifelong Hypoxia Produces Multigenerational Developmental Lung Disease and Pulmonary Hypertension in Mice

Chronic hypoxia during development can impair lung and pulmonary vascular growth, but most mouse models of hypoxia-induced pulmonary hypertension expose adult animals for limited periods and do not capture lifelong or multigenerational hypoxic exposure. We developed a multigenerational model of lifelong moderate hypoxia by maintaining wild-type C57BL/6J mice at 13% inspired oxygen fraction (FiO₂), beginning before fertilization and continuing through gestation, postnatal development, and adulthood. This exposure permitted breeding over two generations. Pregnancy and delivery rates were largely preserved, but second-generation litters had fewer pups alive at birth and reduced overall survival to weaning, primarily due to fetal or perinatal loss. Among surviving adults, both first- and second-generation hypoxia-exposed mice developed pulmonary hypertension, right ventricular systolic dysfunction, right ventricular hypertrophy, and reduced exercise capacity compared with age-matched room-air controls. These functional abnormalities were accompanied by alveolar simplification, increased lung compliance, increased muscularization of small pulmonary arterioles, and reduced peripheral pulmonary vascular density. Several measures, including right ventricular systolic pressure and right ventricular remodeling, were modestly worse in second-generation mice. Hemoglobin concentration was increased in both hypoxia-exposed generations, whereas exploratory analysis of gastrocnemius muscle showed no detectable reduction in skeletal muscle capillary density in first-generation mice. Thus, lifelong exposure to 13% FiO₂ establishes a survivable but pathologic model of developmental hypoxia that permits multigenerational studies while producing persistent lung developmental abnormalities, pulmonary vascular disease, right ventricular dysfunction, erythrocytosis, and exercise limitation.