Tetralogy of Fallot: aorto-pulmonary collaterals and pulmonary arteries have distinctly different transcriptomes

Pulmonary arteries of Williams syndrome patients exhibit altered serotonin metabolism genes and degenerated medial layer architecture

BACKGROUND

Williams-Beuren syndrome (WS) is characterized by cardiovascular abnormalities associated with a multigene deletion on 7q11.23, in particular elastin (ELN). Peripheral pulmonary artery stenosis (PPAS) frequently affects pediatric patients with WS. Molecular investigation of WS pulmonary arterial (PA) tissue is limited by tissue scarcity.

METHODS

We compared transcriptomes, tissue architecture, and localized changes in protein expression in PA tissue from patients with WS (n = 8) and donors (n = 5).

RESULTS

Over 100 genes were differentially expressed at the ≥4-fold level, including genes related to the serotonin signaling pathway: >60-fold downregulation of serotonin transporter SLC6A4 and >3-fold upregulation of serotonin receptor HTR2A. Histologic examination revealed abnormal elastin distribution and smooth muscle cell morphology in WS PA, with markedly shorter, disorganized elastin fibers, and expanded proteoglycan-rich extracellular matrix between muscle layers.

CONCLUSIONS

There were significant abnormalities in the PA expression of genes regulating serotonin signaling, metabolism, and receptors in WS. Those changes were associated with distinct changes in the arterial structure and may play a role in the stenosis-promoting effects of elevated shear stress at PA bifurcations in WS.

IMPACT

Serotonin pathway signaling is significantly altered in the pulmonary arteries of patients with Williams syndrome and severe peripheral arterial stenosis. The present study compares the histological and biochemical characteristics of pulmonary arteries from patients with Williams syndrome to those of controls, something that has not, to our knowledge, been done previously. It demonstrates marked abnormalities in the pulmonary arteries of patients with Williams syndrome, especially significant pathologic alterations in the signaling of the serotonin pathway. The findings of this study provide direction for the development of potential therapies to treat pulmonary artery stenosis in patients with Williams syndrome.

Deep Hypothermic Circulatory Arrest Activates Neural Precursor Cells in the Neonatal Brain

BACKGROUND

Use of antegrade cerebral perfusion (ACP) as an alternative neuroprotection strategy to deep hypothermic circulatory arrest (DHCA) in the setting of cardiopulmonary bypass in neonates has become a common approach, although the value of ACP over DHCA remains highly debated. This study investigated the disruption to neonatal brain homeostasis by DHCA and ACP.

METHODS

Neonatal pigs (7 days old) undergoing bypass were assigned to 4 groups: DHCA at 18°C and ACP at 18°, 25°, and 32° for 45 minutes (n = 6 per group). ACP was initiated through the innominate artery and maintained at 40 mL/kg/min. After bypass, all animals were maintained sedated and intubated for 24 hours before being euthanized. Brain subventricular zone tissues were analyzed for histologic injury by assessing apoptosis and neural homeostasis (Nestin).

RESULTS

Histologic examination showed no significant ischemic/hypoxic neuronal death at any cooling temperature among the 4 treatment groups. However, we detected a significantly higher apoptotic rate in DHCA compared with ACP at 18°C (P = .003-.017) or 25°C (P = .012-.043), whereas apoptosis at 32°C was not different from DHCA. Of note, we identified increased Nestin expression in the DHCA group compared with all ACP groups (P range = .011-.041).

CONCLUSIONS

Neonatal piglet ACP at 18° or 25°C provides adequate protection from increased brain cellular apoptosis. In contrast to ACP, however, DHCA induces brain Nestin expression, indicating activation of neural progenitor cells and the potential of altering neonatal neurodevelopmental progression. DHCA has potential to more profoundly disrupt neural homeostasis than does ACP.

Intraesophageal aortopulmonary collateral artery occlusion in an infant with Tetralogy of Fallot and flow-dependent major aortopulmonary collateral arteries

Patients with flow-dependent aortopulmonary collateral arteries often exhibit tenuous clinical statuses. Here we present an infant with Tetralogy of Fallot with pulmonary atresia (TOF-PA) and major aortopulmonary collateral arteries (MAPCAs) who experienced clinically significant oxygen desaturations during feedings. These frequent episodes were attributed to gastroesophageal reflux. In preparation for possible surgical correction of her complex congenital heart condition, she was intubated for a cardiac catheterization to better characterize her anatomy, but terminally decompensated shortly after extubation and restarting feeding. On autopsy, very mild evidence of esophageal reflux was present; instead, one of her four aortopulmonary collateral arteries was unexpectedly discovered traversing through the muscular layer of her esophageal wall. This finding was confirmed microscopically with significant intimal hyperplasia compared to uninvolved collateral arteries. The remainder of the autopsy findings, including her myocardium, lungs, and esophagus, were unremarkable. Given the feeding-associated oxygen desaturations present in life and the aberrant collateral artery's comparative stenosis at death, we speculate that the repetitive trauma of esophageal peristalsis was not only significant enough to temporarily impact oxygenation but, over time, led to near-occlusion of the intraesophageal collateral artery, which may have contributed to the terminal decompensation of this already tenuous patient.

A novel approach to the diagnosis and treatment of hemoptysis in infants: A case series

INTRODUCTION

Hemoptysis in children is an uncommon presenting symptom but can be life-threatening if massive. Cardiac catheterization and coil embolization of aorto-pulmonary collateral vessels (APCs) is uncommon in pediatric hemoptysis patients without congenital heart disease.

METHODS

We present a series of seven infants (≤12 months of age) with hemoptysis, all of whom underwent cardiac catheterization to look for and intervene upon APCs, if found. Only those patients who underwent both bronchoscopy as well as cardiac catheterization from January 1995 to January 2015 were included in this retrospective review.

RESULTS

Seven patients met inclusion criteria, and three had a history of recurrent hemoptysis. The mean age was 3 months. Four had evidence of bleeding on bronchoscopy. All seven had respiratory distress which necessitated ICU admission; five required mechanical ventilation. Cardiac catheterization showed significant APCs (>2 mm) in six of the seven studied patients, all of which were coil embolized. One patient had no significant APCs and therefore, no embolization. All patients had complete resolution with no recurrences during the 10-20-year outpatient follow-up period. Chest CT scans were not helpful in delineating the site or etiology of bleeding in any patient.

CONCLUSIONS

APCs should be considered as a differential diagnosis for pulmonary hemorrhage in infants after more common causes have been ruled out.

Modeling Impaired Coaptation Effects on Mitral Leaflet Homeostasis Using a Flow-Culture Bioreactor

BACKGROUND

Mitral valve (MV) regurgitation constitutes an increasing burden of adult and pediatric cardiac disease tending to worsen over time. Whether altered mechanical forces on leaflets cause valve disease is unknown. Here we show that MV leaflet coaptive strain disruption alters expression of genes critical to leaflet homeostasis.

METHODS

We used a flow-culture bioreactor of rat MVs with flow-induced cyclic coaptation (cycling valve group; n = 4) or in a sustained open state (open valve group; n = 4). After 3 days of culture, leaflet RNA expression was profiled.

RESULTS

More than 48 genes exhibited markedly changed expression when coaptive leaflet strain was disrupted for 3 days (change >fourfold; p < 0.05; cycling vs open valves). Genes exhibiting highly altered expression included Angpt2, Vegf, Cd74, RT1-Da (HLA-DRA), and Igfbp3. Pathway analysis indicated the most significant signaling pathways regulating the expression changes were Hif1α and Tnfα when MV closure was disrupted.

CONCLUSIONS

Disruption of normal MV coaptive strain markedly alters the expression of leaflet genes, demonstrating that cyclic strain is critically important to leaflet homeostasis. We demonstrate a pattern of MV gene expression changes in which hypoxia signaling is prominently increased in response to disrupted strain cycles. Coaptive strain regulation of MV leaflet homeostasis implicates altered strain as a mechanism potentially initiating valve disease. Early repair may prevent progression of disease driven by altered coaptation.

Pulmonary hypertension's variegated landscape: a snapshot

The many types of pulmonary hypertension (PH) are so protean in their biological origin, histological expression, and natural history that it is difficult to create a summary picture of the disease, or to easily compare and contrast characteristics of one type of PH with another. For newcomers to the field, however, such a picture would facilitate a broad understanding of PH. In this paper, we suggest that four characteristics are fundamental to describing the nature of various types of PH, and that taken together they define a number of patterns of PH expression. These characteristics are histopathology, developmental origin, associated clinical conditions, and potential for resolution. The “snapshot” is a way to concisely display the ways that these signal characteristics intersect in select specific types of PH, and is an effort to summarize these patterns in a way that facilitates a “big picture” comprehension of this disease.

Critical Role of Coaptive Strain in Aortic Valve Leaflet Homeostasis: Use of a Novel Flow Culture Bioreactor to Explore Heart Valve Mechanobiology

Background

Aortic valve (AV) disease presents critical situations requiring surgery in over 2% of the US population and is increasingly the reason for cardiac surgery. Throughout the AV cycle, mechanical forces of multiple types and varying intensities are exerted on valve leaflets. The mechanisms whereby forces regulate leaflet homeostasis are incompletely understood. We used a novel flow bioreactor culture to investigate alteration of AV opening or closure on leaflet genes.

Methods and Results

Culture of rat AV was conducted in a flow bioreactor for 7 days at 37°C under conditions approximating the normal stroke volume. Three force condition groups were compared: Cycling (n=8); always open (Open; n=3); or always closed (Closed; n=5). From each culture, AV leaflets were pooled by force condition and RNA expression evaluated using microarrays. Hierarchical clustering of 16 transcriptome data sets from the 3 groups revealed only 2 patterns of gene expression: Cycling and Closed groups clustered together, whereas Open AV were different (P<0.05). Sustained AV opening induced marked changes in expression (202 transcripts >2‐fold; P<0.05), whereas Closed AV exhibited similar expression pattern as Cycling (no transcripts >2‐fold; P<0.05). Comparison with human sclerotic and calcific AV transcriptomes demonstrated high concordance of >40 Open group genes with progression toward disease.

Conclusions

Failure of AV to close initiates an extensive response characterized by expression changes common to progression to calcific aortic valve disease. AV coaptation, whether phasic or chronic, preserved phenotypic gene expression. These results demonstrate, for the first time, that coaptation of valve leaflets is a fundamentally important biomechanical cue driving homeostasis.

An Overview of Pulmonary Atresia and Major Aortopulmonary Collateral Arteries

Pulmonary atresia with ventricular septal defect and major aortopulmonary collateral arteries (PA/VSD/MAPCAs) is a rare and complex congenital cardiac lesion that has historically carried a poor prognosis. With advancements in surgical management, we have seen an improvement in the outcomes for children affected by this disease. However, this population continues to present challenges due to the complex anatomy and physiology associated with PA/VSD/MAPCA. This summary of material presented during one of the nursing sessions of the 2014 Meeting of the Pediatric Cardiac Intensive Care Society provides an overview for those in cardiac intensive care units who do not have a large experience with this lesion. We will review the anatomy, physiology, surgical approach, postoperative management strategies, and cardiac catheter intervention options for PA/VSD/MAPCAs. We will also discuss recent innovations that may lead to continued improvement in outcomes for this challenging patient population.