Fetal hypoxia is a common complication of pregnancy. It has been shown to programme cardiac and endothelial dysfunction in the offspring in adult life. However, the mechanisms via which this occurs remain elusive, precluding the identification of potential therapy. Using an integrative approach at the isolated organ, cellular and molecular levels, we tested the hypothesis that oxidative stress in the fetal heart and vasculature underlies the molecular basis via which prenatal hypoxia programmes cardiovascular dysfunction in later life. In a longitudinal study, the effects of maternal treatment of hypoxic (13% O2) pregnancy with an antioxidant on the cardiovascular system of the offspring at the end of gestation and at adulthood were studied. On day 6 of pregnancy, rats (n = 20 per group) were exposed to normoxia or hypoxia ± vitamin C. At gestational day 20, tissues were collected from 1 male fetus per litter per group (n = 10). The remaining 10 litters per group were allowed to deliver. At 4 months, tissues from 1 male adult offspring per litter per group were either perfusion fixed, frozen, or dissected for isolated organ preparations. In the fetus, hypoxic pregnancy promoted aortic thickening with enhanced nitrotyrosine staining and an increase in cardiac HSP70 expression. By adulthood, offspring of hypoxic pregnancy had markedly impaired NO-dependent relaxation in femoral resistance arteries, and increased myocardial contractility with sympathetic dominance. Maternal vitamin C prevented these effects in fetal and adult offspring of hypoxic pregnancy. The data offer insight to mechanism and thereby possible targets for intervention against developmental origins of cardiac and peripheral vascular dysfunction in offspring of risky pregnancy.

Human and animal studies suggest that suboptimal early nutrition during critical developmental periods impacts long-term health. For example, maternal overnutrition during pregnancy and lactation in mice programs insulin resistance, obesity, and endothelial dysfunction in the offspring. Here we investigated the effects of diet-induced maternal obesity on the offspring cardiac phenotype and explored potential underlying molecular mechanisms. Dams fed the obesogenic diet were heavier (P < 0.01) and fatter (P < 0.0001) than controls throughout pregnancy and lactation. There was no effect of maternal obesity on offspring body weight or body composition up to 8 wk of age. However, maternal obesity resulted in increased offspring cardiac mass (P < 0.05), increased heart-body weight (P < 0.01), heart weight-tibia length (P < 0.05), increased left ventricular free wall thickness and area (P < 0.01 and P < 0.05, respectively), and increased myocyte width (P < 0.001). Consistent with these structural changes, the expression of molecular markers of cardiac hypertrophy were also increased [Nppb(BNP), Myh7-Myh6(βMHC-αMHC) (both P < 0.05) and mir-133a (P < 0.01)]. Offspring were hyperinsulinemic and displayed increased insulin action through AKT (P < 0.01), ERK (P < 0.05), and mammalian target of rapamycin (P < 0.05). p38MAPK phosphorylation was also increased (P < 0.05), suggesting pathological remodeling. Increased Ncf2(p67phox) expression (P < 0.05) and impaired manganese superoxide dismutase levels (P < 0.01) suggested oxidative stress, which was consistent with an increase in levels of 4-hydroxy-2-trans-nonenal (a measure of lipid peroxidation). We propose that maternal diet-induced obesity leads to offspring cardiac hypertrophy, which is independent of offspring obesity but is associated with hyperinsulinemia-induced activation of AKT, mammalian target of rapamycin, ERK, and oxidative stress.

Key points• High-altitude pregnancy is associated with reduced oxygenation and placental complications, which can affect maternal and fetal outcome. However, most high-altitude populations are also impoverished and because maternal undernutrition itself is known to promote placental problems, the extent to which complications during high-altitude pregnancy could be due to maternal oxygen and/or nutrient restriction remains unclear.• The aim of the study was to investigate whether reduced placental oxygenation, independent of maternal undernutrition, increases maternal and placental oxidative stress and whether maternal treatment with vitamin C is protective.• The study shows that hypoxic pregnancy increased maternal circulating and placental molecular indices of oxidative stress.• Maternal vitamin C treatment was protective and increased birth weight.• The study offers insight to mechanism and intervention against the effects of high altitude on pregnancy.Abstract This study isolated the effects of maternal hypoxia independent of changes in maternal nutrition on maternal circulatory and placental molecular indices of oxidative stress and determined whether maternal antioxidant treatment conferred protection. Pregnant rats were subjected to normoxic pregnancy or 13% O 2 chronic hypoxia for most of gestation with and without maternal treatment with vitamin C in the drinking water. Maternal hypoxia with and without vitamin C did not affect maternal food or water intake and led to a significant increase in maternal and fetal haematocrit. At gestational day 20, maternal plasma urate and L-cysteine concentrations, and placental levels of 4-hydroxynonenal and heat shock protein 70 were increased while placental heat shock protein 90 levels were decreased in hypoxic pregnancy. The induction of maternal circulatory and placental molecular indices of oxidative stress in hypoxic pregnancies was prevented by maternal treatment with vitamin C. Maternal hypoxia during pregnancy with or without vitamin C increased placental weight, but not total or compartmental volumes. Maternal treatment with vitamin C increased birth weight in both hypoxic and normoxic pregnancies. The data show that maternal hypoxia independent of maternal undernutrition promotes maternal and placental indices of oxidative stress, effects that can be prevented by maternal treatment with vitamin C in hypoxic pregnancy. While vitamin C may not be the ideal candidate of choice for therapy in pregnant women, and taking into consideration differences in ascorbic acid metabolism between rats and humans, the data do underlie that antioxidant treatment may provide a useful intervention to improve placental function and protect fetal growth in pregnancy complicated by fetal hypoxia.

Progress in the study of pregnancy complicated by chronic hypoxia in large mammals has been held back by the inability to measure long‐term significant reductions in fetal oxygenation at values similar to those measured in human pregnancy complicated by fetal growth restriction. Here, we introduce a technique for physiological research able to maintain chronically instrumented maternal and fetal sheep for prolonged periods of gestation under significant and controlled isolated chronic hypoxia beyond levels that can be achieved by habitable high altitude. This model of chronic hypoxia permits measurement of materno‐fetal blood gases as the challenge is actually occurring. Chronic hypoxia of this magnitude and duration using this model recapitulates the significant asymmetric growth restriction, the pronounced cardiomyopathy, and the loss of endothelial function measured in offspring of high‐risk pregnancy in humans, opening a new window of therapeutic research.

Evidence derived from human clinical studies and experimental animal models shows a causal relationship between adverse pregnancy and increased cardiovascular disease in the adult offspring. However, translational studies isolating mechanisms to design intervention are lacking. Sheep and humans share similar precocial developmental milestones in cardiovascular anatomy and physiology. We tested the hypothesis in sheep that maternal treatment with antioxidants protects against fetal growth restriction and programmed hypertension in adulthood in gestation complicated by chronic fetal hypoxia, the most common adverse consequence in human pregnancy. Using bespoke isobaric chambers, chronically catheterized sheep carrying singletons underwent normoxia or hypoxia (10% oxygen [O2]) ± vitamin C treatment (maternal 200 mg.kg−1 IV daily) for the last third of gestation. In one cohort, the maternal arterial blood gas status, the value at which 50% of the maternal hemoglobin is saturated with oxygen (P50), nitric oxide (NO) bioavailability, oxidative stress, and antioxidant capacity were determined. In another, naturally delivered offspring were raised under normoxia until early adulthood (9 months). Lambs were chronically instrumented and cardiovascular function tested in vivo. Following euthanasia, femoral arterial segments were isolated and endothelial function determined by wire myography. Hypoxic pregnancy induced fetal growth restriction and fetal oxidative stress. At adulthood, it programmed hypertension by enhancing vasoconstrictor reactivity and impairing NO-independent endothelial function. Maternal vitamin C in hypoxic pregnancy improved transplacental oxygenation and enhanced fetal antioxidant capacity while increasing NO bioavailability, offsetting constrictor hyper-reactivity and replenishing endothelial function in the adult offspring. These discoveries provide novel insight into mechanisms and interventions against fetal growth restriction and adult-onset programmed hypertension in an animal model of complicated pregnancy in a species of similar temporal developmental milestones to humans.