Emily J. Camm

Developmental Programming of Cardiovascular Dysfunction by Prenatal Hypoxia and Oxidative Stress

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.

Glial responses to neonatal hypoxic-ischemic injury in the rat cerebral cortex

Neurogenesis is nearly completed after birth, whereas gliogenic activities remain intense during the postnatal period in the developing rat cortex. These include involution of radial glia, proliferation of astrocytes and oligodendrocytes and myelin formation. Little is known about the effects of hypoxic–ischemic (HI) injury on these critical postnatal processes. Here we explored the glial reactions to mild HI injury of the neonatal rat cerebral cortex at P3. We show that the HI lesion results in disruption of the normal radial glia architecture, which was paralleled by an increase in GFAP immunopositive reactive astrocytes. The morphology of these latter cells and the fact that they were immunolabelled for both nestin and GFAP suggest an accelerated transformation of radial glia into astrocytes. In addition, BrdU/GFAP immunostaining revealed a significant increase of double‐labelled cells indicating an acute proliferation of astrocytes after HI. This enhanced proliferative activity of astrocytes persisted for several weeks. We found an elevated number and increased mitotic activity of both NG2‐positive oligodendrocyte progenitors and RIP‐positive oligodendrocytes after injury. These findings imply that glial responses are central to cortical tissue remodelling following neonatal ischemia and represent a potential target for therapeutic approaches.

Partial contributions of developmental hypoxia and undernutrition to prenatal alterations in somatic growth and cardiovascular structure and function

OBJECTIVE The objective of the study was to compare and contrast the effects of developmental hypoxia vs undernutrition on fetal growth, cardiovascular morphology, and function. STUDY DESIGN On day 15 of gestation, Wistar dams were divided into control, hypoxic (10% O(2)), or undernourished (35% reduction in food intake) pregnancy. On day 20, fetal thoraces were fixed, and the fetal heart and aorta underwent quantitative histological analysis. In a separate group, fetal aortic vascular reactivity was determined via wire myography. RESULTS Both hypoxic and undernourished pregnancy was associated with asymmetric fetal growth restriction. Pregnancy complicated by hypoxia promoted fetal aortic thickening without changes in cardiac volumes when expressed as a percentage of total heart volume. In contrast, maternal undernutrition affected fetal cardiac morphology without changes in aortic structure. Fetal aortic vascular reactivity was also differentially affected by hypoxia or undernutrition. CONCLUSION Developmental hypoxia or undernutrition in late gestation has differential effects on fetal cardiovascular morphology and function.

Cerebral outcomes in a preterm baboon model of early versus delayed nasal continuous positive airway pressure

BACKGROUND. The survival of prematurely born infants has greatly increased in recent decades because of advances in neonatal intensive care, which have included the advent of ventilatory therapies. However, there is limited knowledge as to the impact of these therapies on the developing brain. The purpose of this work was to evaluate the influence of randomized respiratory therapy with either early continuous positive airway pressure or delayed continuous positive airway pressure preceded by positive pressure ventilation on the extent of brain injury and altered development in a prematurely delivered primate model. METHODS. Fetal baboons were delivered at 125 days of gestation (term: ∼185 days of gestation) by cesarean section. Animals were maintained for 28 days postdelivery with either: early continuous positive airway pressure (commencing at 24 hours; n = 6) or delayed continuous positive airway pressure (positive pressure ventilation for 5 days followed by nCPAP; n = 5). Gestational controls (n = 4) were delivered at 153 days of gestation. At the completion of the study, animals were killed, the brains were assessed histologically for growth and development, and evidence of cerebral injury and indices for both parameters were formulated. RESULTS. Brain and body weights were reduced in all of the nasal continuous positive airway pressure animals compared with controls; however, the brain/body weight ratio was increased in early continuous positive airway pressure animals. Within both nasal continuous positive airway pressure groups compared with controls, there was increased gliosis in the subcortical and deep white matter and cortex and a persistence of radial glia. Early continuous positive airway pressure was associated with less cerebral injury than delayed continuous positive airway pressure therapy. Neuropathologies were not observed in controls. CONCLUSIONS. Premature delivery, in the absence of potentiating factors, such as hypoxia or infection, is associated with a decrease in brain growth and the presence of subtle brain injury, which seems to be modified by respiratory therapies with early continuous positive airway pressure being associated with less overall cerebral injury.

Prenatal hypoxia independent of undernutrition promotes molecular markers of insulin resistance in adult offspring.

Molecular mechanisms predisposing people to insulin resistance are starting to emerge. Altered insulin signaling for hepatic gluconeogenesis and muscle glucose uptake is thought to play a central role. Development under suboptimal conditions is also known to increase the risk of insulin resistance in adulthood. However, the partial contributions of reduced oxygen vs. nutrient delivery to the fetus, two common adverse conditions in utero, to developmental programming of insulin resistance remain unknown. The aim of this study was to determine the effects of developmental hypoxia or undernutrition on the expression of insulin‐signaling proteins in liver and skeletal muscle in adult rat offspring. We show that the expression of hepatic phospho‐Akt and muscle Akt2 were significantly reduced in offspring of hypoxic, relative to offspring from normoxic or undernourished, pregnancies. Hepatic Akt‐1, Akt‐2, and PKCζ protein expression was reduced in offspring from both hypoxic and undernourished pregnancies. Muscle GLUT4 expression was decreased in undernourished, and further decreased in hypoxic, offspring. These findings link prenatal hypoxia to down‐regulation of components of hepatic and muscle Akt expression in adult offspring. Akt may represent a pharmaceutical target for clinical intervention against the developmental programming of metabolic disease resulting from prenatal hypoxia.—Camm, E. J., Martin‐Gronert, M. S., Wright, N. L., Hansell, J. A., Ozanne, S. E., Giussani, D. A. Prenatal hypoxia independent of undernutrition promotes molecular markers of insulin resistance in adult offspring. FASEB J. 25, 420–427 (2011). www.fasebj.org

Ascorbate prevents placental oxidative stress and enhances birth weight in hypoxic pregnancy in rats.

•  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.

The Programming Power of the Placenta

Size at birth is a critical determinant of life expectancy, and is dependent primarily on the placental supply of nutrients. However, the placenta is not just a passive organ for the materno-fetal transfer of nutrients and oxygen. Studies show that the placenta can adapt morphologically and functionally to optimize substrate supply, and thus fetal growth, under adverse intrauterine conditions. These adaptations help meet the fetal drive for growth, and their effectiveness will determine the amount and relative proportions of specific metabolic substrates supplied to the fetus at different stages of development. This flow of nutrients will ultimately program physiological systems at the gene, cell, tissue, organ, and system levels, and inadequacies can cause permanent structural and functional changes that lead to overt disease, particularly with increasing age. This review examines the environmental regulation of the placental phenotype with particular emphasis on the impact of maternal nutritional challenges and oxygen scarcity in mice, rats and guinea pigs. It also focuses on the effects of such conditions on fetal growth and the developmental programming of disease postnatally. A challenge for future research is to link placental structure and function with clinical phenotypes in the offspring.

Developmental and metabolic brain alterations in rats exposed to bisphenol A during gestation and lactation

In recent years, considerable research has focused on the biological effect of endocrine‐disrupting chemicals. Bisphenol A (BPA) has been implicated as an endocrine‐disrupting chemical (EDC) due to its ability to mimic the action of endogenous estrogenic hormones.

Heart Disease Link to Fetal Hypoxia and Oxidative Stress

The quality of the intrauterine environment interacts with our genetic makeup to shape the risk of developing disease in later life. Fetal chronic hypoxia is a common complication of pregnancy. This chapter reviews how fetal chronic hypoxia programmes cardiac and endothelial dysfunction in the offspring in adult life and discusses the mechanisms via which this may occur. Using an integrative approach in large and small animal models at the in vivo, isolated organ, cellular and molecular levels, our programmes of work have raised the hypothesis that oxidative stress in the fetal heart and vasculature underlies the mechanism via which prenatal hypoxia programmes cardiovascular dysfunction in later life. Developmental hypoxia independent of changes in maternal nutrition promotes fetal growth restriction and induces changes in the cardiovascular, metabolic and endocrine systems of the adult offspring, which are normally associated with disease states during ageing. Treatment with antioxidants of animal pregnancies complicated with reduced oxygen delivery to the fetus prevents the alterations in fetal growth, and the cardiovascular, metabolic and endocrine dysfunction in the fetal and adult offspring. The work reviewed offers both insight into mechanisms and possible therapeutic targets for clinical intervention against the early origin of cardiometabolic disease in pregnancy complicated by fetal chronic hypoxia.

Postnatal outcomes in term and preterm lambs following fetal growth restriction

1. Epidemiological evidence indicates that low birthweight increases the risk of a number of adult‐onset diseases. It is now apparent that many babies with a low birthweight may have been subjected to a combination of reduced growth rates in utero as well as preterm birth. However, the long‐term effects of preterm birth following intra‐uterine growth restriction (IUGR) are unknown. Thus, our objectives were: (i) to identify prenatal factors associated with preterm birth in IUGR fetuses; and (ii) to characterize postnatal effects of preterm birth following IUGR.