How effectively can clinical examination pick up congenital heart disease at birth?

Differential requirement for DICER1 activity during the development of mitral and tricuspid valves

Mitral and tricuspid valves are essential for unidirectional blood flow in the heart. They are derived from similar cell sources, and yet congenital dysplasia affecting both valves is clinically rare, suggesting the presence of differential regulatory mechanisms underlying their development. Here, we specifically inactivated Dicer1 in the endocardium during cardiogenesis and found that Dicer1 deletion caused congenital mitral valve stenosis and regurgitation, whereas it had no impact on other valves. We showed that hyperplastic mitral valves were caused by abnormal condensation and extracellular matrix (ECM) remodeling. Our single-cell RNA sequencing analysis revealed impaired maturation of mesenchymal cells and abnormal expression of ECM genes in mutant mitral valves. Furthermore, expression of a set of miRNAs that target ECM genes was significantly lower in tricuspid valves compared to mitral valves, consistent with the idea that the miRNAs are differentially required for mitral and tricuspid valve development. We thus reveal miRNA-mediated gene regulation as a novel molecular mechanism that differentially regulates mitral and tricuspid valve development, thereby enhancing our understanding of the non-association of inborn mitral and tricuspid dysplasia observed clinically.

SEMA6D regulates perinatal cardiomyocyte proliferation and maturation in mice

Cardiomyocytes undergo dramatic changes during the fetal to neonatal transition stage to adapt to the new environment. The molecular and genetic mechanisms regulating these changes remain elusive. In this study, we showed Sema6D as a novel signaling molecule regulating perinatal cardiomyocyte proliferation and maturation. SEMA6D is a member of the Semaphorin family of signaling molecules. To reveal its function during cardiogenesis, we specifically inactivated Sema6D in embryonic cardiomyocytes using a conditional gene deletion approach. All mutant animals showed hypoplastic myocardial walls in neonatal hearts due to reduced cell proliferation. We further revealed that expression of MYCN and its downstream cell cycle regulators is impaired in late fetal hearts in which Sema6D is deleted, suggesting that SEMA6D acts through MYCN to regulate cardiomyocyte proliferation. In early postnatal mutant hearts, expression of adult forms of sarcomeric proteins is increased, while expression of embryonic forms is decreased. These data collectively suggest that SEMA6D is required to maintain late fetal/early neonatal cardiomyocytes at a proliferative and less mature status. Deletion of Sema6D in cardiomyocytes led to reduced proliferation and accelerated maturation. We further examined the consequence of these defects through echocardiographic analysis. Embryonic heart deletion of Sema6D significantly impaired the cardiac contraction of male adult hearts, while having a minor effect on female mutant hearts, suggesting that the effect of Sema6D-deletion in adult hearts is sex dependent.

Malformations Surveillance: Comparison between Findings at Birth and Age 1 Year

BACKGROUND

Malformations surveillance programs among newborn infants are used to determine the prevalence of congenital anomalies. A comparison in the same group of infants between the malformations detected at birth and those detected at 1 year of age will identify errors in the surveillance process and, also, the abnormalities more likely not to be detected at birth, but later in the first year of life.

METHODS

The malformations identified at birth by Brigham and Women's Hospital (BWH) in the years 2000 and 2005 have been compared with the abnormalities detected in the same infants up to age 1 year by the Massachusetts Birth Defects Monitoring Program.

RESULTS

The Massachusetts Birth Defects Monitoring Program identified 557 malformed infants in 2000 and 415 in 2005. Of these, 34 (3.5%) of the malformed infants were missed at birth by BWH Surveillance Program. An additional 22 (2.3%) malformed infants had delayed detection, as they were identified later in the first year. The reasons were the fact that: (1) the Surveillance staff reviewed the physicians' recorded findings only on the first day of life; (2) failure of the examining pediatrician to record the presence of a malformation in her/his notes. The most common abnormalities with delayed detection were mild heart defects, such as atrial septal defects.

CONCLUSION

These findings emphasize the importance in a newborn malformations surveillance program of continued follow up in the first days of life, especially in small, premature infants. Birth Defects Research 110:142-147, 2018. © 2017 Wiley Periodicals, Inc.

Risk Factors for Necrotizing Enterocolitis in Neonates: A Retrospective Case-Control Study

BACKGROUND

Necrotizing enterocolitis (NEC) in neonates is devastating, and risk-factor identification is crucial. This study aimed to evaluate risk factors for NEC in different gestational age (GA) groups.

METHODS

Risk factors associated with NEC were investigated using a retrospective case-control design. Patients with Bell's Stage NEC≥II were divided into three groups based on GA: I, <34 weeks; II, ≥34 weeks but <37 weeks; III, ≥37 weeks. Each case was paired with two GA- and weight-matched controls. Data were collected from medical records, and univariate and conditional logistic regression analyses employed.

RESULTS

A total of 238 cases and 476 controls were enrolled. Variation in the months when NEC was diagnosed was noted, with a peak in January and a trough in August. Intrahepatic cholestasis of pregnancy and transfusion with packed red blood cells were significantly associated with NEC in preterm infants. Meconium aspiration syndrome was an independent risk factor for a greater chance of NEC development in full-term infants. Postnatal asphyxia and sepsis were associated with an increased risk of NEC in all groups. Probiotic use was associated with a reduced risk of NEC. Patients aged >34 weeks with congenital heart disease were more likely than controls to have NEC.

CONCLUSION

Intrahepatic cholestasis of pregnancy and meconium aspiration syndrome may be new risk factors for NEC.

Functions of miRNAs during Mammalian Heart Development

MicroRNAs (miRNAs) play essential roles during mammalian heart development and have emerged as attractive therapeutic targets for cardiovascular diseases. The mammalian embryonic heart is mainly derived from four major cell types during development. These include cardiomyocytes, endocardial cells, epicardial cells, and neural crest cells. Recent data have identified various miRNAs as critical regulators of the proper differentiation, proliferation, and survival of these cell types. In this review, we briefly introduce the contemporary understanding of mammalian cardiac development. We also focus on recent developments in the field of cardiac miRNAs and their functions during the development of different cell types.

Yap1 is required for endothelial to mesenchymal transition of the atrioventricular cushion

Cardiac malformations due to aberrant development of the atrioventricular (AV) valves are among the most common forms of congenital heart diseases. Normally, heart valve mesenchyme is formed from an endothelial to mesenchymal transition (EMT) of endothelial cells of the endocardial cushions. Yes-associated protein 1 (YAP1) has been reported to regulate EMT in vitro, in addition to its known role as a major regulator of organ size and cell proliferation in vertebrates, leading us to hypothesize that YAP1 is required for heart valve development. We tested this hypothesis by conditional inactivation of YAP1 in endothelial cells and their derivatives. This resulted in markedly hypocellular endocardial cushions due to impaired formation of heart valve mesenchyme by EMT and to reduced endocardial cell proliferation. In endothelial cells, TGFβ induces nuclear localization of Smad2/3/4 complex, which activates expression of Snail, Twist1, and Slug, key transcription factors required for EMT. YAP1 interacts with this complex, and loss of YAP1 disrupts TGFβ-induced up-regulation of Snail, Twist1, and Slug. Together, our results identify a role of YAP1 in regulating EMT through modulation of TGFβ-Smad signaling and through proliferative activity during cardiac cushion development.

Cell autonomous requirement of endocardial Smad4 during atrioventricular cushion development in mouse embryos

Atrioventricular (AV) cushions are the precursors of AV septum and valves. In this study, we examined roles of Smad4 during AV cushion development using a conditional gene inactivation approach. We found that endothelial/endocardial inactivation of Smad4 led to the hypocellular AV cushion defect and that both reduced cell proliferation and increased apoptosis contributed to the defect. Expression of multiple genes critical for cushion development was down-regulated in mutant embryos. In collagen gel assays, the number of mesenchymal cells formed is significantly reduced in mutant AV explants compared to that in control explants, suggesting that the reduction of cushion mesenchyme formation in mutants is unlikely secondary to their gross vasculature abnormalities. Using a previously developed immortal endocardial cell line, we showed that Smad4 is required for BMP signaling- stimulated upregulation of Tbx20 and Gata4. Therefore, our data collectively support the cell-autonomous requirement of endocardial Smad4 in regulating AV cushion development.

Cardiac assessment in the neonatal population

Congenital heart defects are not uncommon among neonatal patients. Although most are benign, the prompt identification of a life-threatening anomaly is essential for rapid intervention and a positive treatment outcome. Cardiac defects may be identified in the newborn nursery with thorough and systematic physical assessment, including inspection, palpation, auscultation, and measurement of blood pressure and oxygen saturations. The ability of the nurse to identify irregular findings during physical assessment aids rapid identification and treatment.

Congenital cardiac disease in the newborn infant: past, present, and future

Congenital heart defects are the most common of all congenital malformations, with a review of the literature reporting the incidence at 6 to 8 per 1000 live births. The Centers for Disease Control reports cyanotic heart defects occurred in 56.9 per 100,000 live births in the United States in 2005, with higher rates noted when maternal age exceeded 40 years. The incidence of congenital heart disease in premature infants is 12.5 per 1000 live births, excluding isolated patent ductus arteriosus and atrial septal defect. Despite advances in detection and treatment, congenital heart disease accounts for 3% of all infant deaths and 46% of death from congenital malformations. This article discusses the embryology, pathogenesis, clinical presentation, incidence, classifications, and management of congenital heart diseases.