Conduction system abnormalities in rat embryos induced by maternal hyperthermia

The role of teratogens in neural crest development

The neural crest (NC), discovered by Wilhelm His 150 years ago, gives rise to a multipotent migratory embryonic cell population that generates a remarkably diverse and important array of cell types during the development of the vertebrate embryo. These cells originate in the neural plate border (NPB), which is the ectoderm between the neural plate and the epidermis. They give rise to the neurons and glia of the peripheral nervous system, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies are a class of congenital diseases resulting from the abnormal induction, specification, migration, differentiation or death of NC cells (NCCs) during embryonic development and have an important medical and societal impact. In general, congenital defects affect an appreciable percentage of newborns worldwide. Some of these defects are caused by teratogens, which are agents that negatively impact the formation of tissues and organs during development. In this review, we will discuss the teratogens linked to the development of many birth defects, with a strong focus on those that specifically affect the development of the NC, thereby producing neurocristopathies. Although increasing attention is being paid to the effect of teratogens on embryonic development in general, there is a strong need to critically evaluate the specific role of these agents in NC development. Therefore, increased understanding of the role of these factors in NC development will contribute to the planning of strategies aimed at the prevention and treatment of human neurocristopathies, whose etiology was previously not considered.

Cortisol stimulates proliferation and apoptosis in the late gestation fetal heart: differential effects of mineralocorticoid and glucocorticoid receptors

We have previously found that modest chronic increases in maternal cortisol result in an enlarged fetal heart. To explore the mechanisms of this effect, we used intrapericardial infusions of a mineralocorticoid receptor (MR) antagonist (canrenoate) or of a glucocorticoid receptor (GR) antagonist (mifepristone) in the fetus during maternal infusion of cortisol (1 mg·kg⁻¹·day⁻¹). We have shown that the MR antagonist blocked the increase in fetal heart weight and in wall thickness resulting from maternal cortisol infusion. In the current study we extended those studies and found that cortisol increased Ki67 staining in both ventricles, indicating cell proliferation, but also increased active caspase-3 staining in cells of the conduction pathway in the septum and subendocardial layers of the left ventricle, suggesting increased apoptosis in Purkinje fibers. The MR antagonist blocked the increase in cell proliferation, whereas the GR antagonist blocked the increased apoptosis in Purkinje fibers. We also found evidence of activation of caspase-3 in c-kit-positive cells, suggesting apoptosis in stem cell populations in the ventricle. These studies suggest a potentially important role of corticosteroids in the terminal remodeling of the late gestation fetal heart and suggest a mechanism for the cardiac enlargement with excess corticosteroid exposure.

Maternal fever during early pregnancy and the risk of oral clefts

An increased risk of birth defects after hyperthermic exposures has been confirmed in animal studies, but population studies have yielded inconsistent results. Oral clefts are a common birth defect and have been associated with these exposures in some of these studies. In this study, data from the National Birth Defects Prevention Study was used to evaluate the association of maternal report of febrile illness in early pregnancy and the risk of oral clefts. All oral cleft cases born between 1997 and 2004 were compared with nonmalformed controls born in the same geographical region during the same time period. Mothers reporting febrile illness during pregnancy were stratified by fever grade and antipyretic use. Logistic regression models were used to generate crude and adjusted odds ratios for exposure to fever and association with each oral cleft phenotype. The dataset included 5821 controls, 1567 cases of cleft lip with or without cleft palate (CL+/-P) and 835 cases of cleft palate only. A modestly increased risk was observed for isolated CL+/-P (odds ratio, 1.28; 95% confidence interval, 1.01-1.63). Stratification by fever grade (body temperature <101.5 degrees or > or =101.5 degrees F) did not yield significant differences in risk. Risk estimates were higher among women who reported a fever, but did not take antipyretics to control their fever, particularly for nonisolated compared with isolated oral clefts. This finding suggests that adequate control of fever may diminish the deleterious effects of fever in cases of oral cleft.

Prenatal zinc deficiency: influence on heart morphology and distribution of key heart proteins in a rat model

The etiology of congenital heart disease is multifactorial, with genetics and nutritional deficiencies recognized as causative agents. Maternal zinc (Zn) deficiency is associated with an increased risk for fetal heart malformations; however, the contributing mechanisms have yet to be identified. In this study, we fed pregnant rats a Zn-adequate diet (ZnA), a Zn-deficient (ZnD), or a restricted amount of Zn adequate diet (RF) beginning on gestation day (GD) 4.5, to examine whether increased cell death and changes in cardiac neural crest cells (NCC) play a role in Zn deficiency-induced heart defects. Fetuses were collected on GD 13.5, 15.5, and 18.5 and processed for GATA-4, FOG-2, connexin-43 (Cx43), HNK-1, smooth muscle alpha-actin (SMA) and cleaved caspase-3 protein expression. Fetuses from ZnA-fed dams showed normal heart development, whereas fetuses from dams fed with the ZnD diet exhibited a variety of heart anomalies, particularly in the region of the outflow tract. HNK-1 expression was lower than normal in the hearts of GD13.5 and 15.5 ZnD fetuses, particularly in the right atrium and in the distal tip of the interventricular septum. Conversely, Cx43 immunoreactivity was increased throughout the heart in fetuses from ZnD dams compared to fetuses from control dams. The distribution and intensity of expression of SMA, GATA-4, FOG-2, and markers of apoptosis were similar among the three groups. We propose that Zn deficiency induced alterations in the distribution of Cx43 and HNK-1 in fetal hearts contribute to the occurrence of the developmental heart anomalies.