3D Imaging Reveals Complex Microvascular Remodeling in the Right Ventricle in Pulmonary Hypertension.

BACKGROUND: Pathogenic concepts of right ventricular (RV) failure in pulmonary arterial hypertension focus on a critical loss of microvasculature. However, the methods underpinning prior studies did not take into account the 3-dimensional (3D) aspects of cardiac tissue, making accurate quantification difficult. We applied deep-tissue imaging to the pressure-overloaded RV to uncover the 3D properties of the microvascular network and determine whether deficient microvascular adaptation contributes to RV failure. METHODS: Heart sections measuring 250-µm-thick were obtained from mice after pulmonary artery banding (PAB) or debanding PAB surgery and properties of the RV microvascular network were assessed using 3D imaging and quantification. Human heart tissues harvested at the time of transplantation from pulmonary arterial hypertension cases were compared with tissues from control cases with normal RV function. RESULTS: Longitudinal 3D assessment of PAB mouse hearts uncovered complex microvascular remodeling characterized by tortuous, shorter, thicker, highly branched vessels, and overall preserved microvascular density. This remodeling process was reversible in debanding PAB mice in which the RV function recovers over time. The remodeled microvasculature tightly wrapped around the hypertrophied cardiomyocytes to maintain a stable contact surface to cardiomyocytes as an adaptation to RV pressure overload, even in end-stage RV failure. However, microvasculature-cardiomyocyte contact was impaired in areas with interstitial fibrosis where cardiomyocytes displayed signs of hypoxia. Similar to PAB animals, microvascular density in the RV was preserved in patients with end-stage pulmonary arterial hypertension, and microvascular architectural changes appeared to vary by etiology, with patients with pulmonary veno-occlusive disease displaying a lack of microvascular complexity with uniformly short segments. CONCLUSIONS: 3D deep tissue imaging of the failing RV in PAB mice, pulmonary hypertension rats, and patients with pulmonary arterial hypertension reveals complex microvascular changes to preserve the microvascular density and maintain a stable microvascular-cardiomyocyte contact. Our studies provide a novel framework to understand microvascular adaptation in the pressure-overloaded RV that focuses on cell-cell interaction and goes beyond the concept of capillary rarefaction.

MicroRNA-34a-Dependent Attenuation of Angiogenesis in Right Ventricular Failure.

BACKGROUND: The right ventricle (RV) is at risk in patients with complex congenital heart disease involving right-sided obstructive lesions. We have shown that capillary rarefaction occurs early in the pressure-loaded RV. Here we test the hypothesis that microRNA (miR)-34a, which is induced in RV hypertrophy and RV failure (RVF), blocks the hypoxia-inducible factor-1α-vascular endothelial growth factor (VEGF) axis, leading to the attenuated angiogenic response and increased susceptibility to RV failure. METHODS AND RESULTS: Mice underwent pulmonary artery banding to induce RV hypertrophy and RVF. Capillary rarefaction occurred immediately. Although hypoxia-inducible factor-1α expression increased (0.12±0.01 versus 0.22±0.03, P=0.05), VEGF expression decreased (0.61±0.03 versus 0.22±0.05, P=0.01). miR-34a expression was most upregulated in fibroblasts (4-fold), but also in cardiomyocytes and endothelial cells (2-fold). Overexpression of miR-34a in endothelial cells increased cell senescence (10±3% versus 22±2%, P<0.05) by suppressing sirtulin 1 expression, and decreased tube formation by 50% via suppression of hypoxia-inducible factor-1α, VEGF A, VEGF B, and VEGF receptor 2. miR-34a was induced by stretch, transforming growth factor-ß1, adrenergic stimulation, and hypoxia in cardiac fibroblasts and cardiomyocytes. In mice with RVF, locked nucleic acid-antimiR-34a improved RV shortening fraction and survival half-time and restored capillarity and VEGF expression. In children with congenital heart disease-related RVF, RV capillarity was decreased and miR-34a increased 5-fold. CONCLUSIONS: In summary, miR-34a from fibroblasts, cardiomyocytes, and endothelial cells mediates capillary rarefaction by suppressing the hypoxia-inducible factor-1α-VEGF axis in RV hypertrophy/RVF, raising the potential for anti-miR-34a therapeutics in patients with at-risk RVs.

A Noninvasive Circulating Signature of Combined Right Ventricular Pressure and Volume Overload in Tetralogy of Fallot/Pulmonary Atresia/Major Aortopulmonary Collateral Arteries.

Background: Despite surgical advances, children with tetralogy of Fallot/pulmonary atresia/major aortopulmonary collaterals (TOF/PA/MAPCAs) are subject to chronic right ventricular (RV) pressure and volume overload. Current diagnostic tools do not identify adverse myocardial remodeling and cannot predict progression to RV failure. We sought to identify a noninvasive, circulating signature of the systemic response to right heart stress to follow disease progression. Methods: Longitudinal data were collected from patients with TOF/PA/MAPCAs (N = 5) at the time of (1) early RV pressure overload and (2) late RV pressure and volume overload. Plasma protein and microRNA expression were evaluated using high-throughput data-independent mass spectroscopy and Agilent miR Microarray, respectively. Results: At the time of early RV pressure overload, median patient age was 0.34 years (0.02-9.37), with systemic RV pressures, moderate-severe hypertrophy, and preserved systolic function. Late RV pressure and volume overload occurred at a median age of 4.08 years (1.51-10.83), with moderate RV hypertrophy and dilation, and low normal RV function; 277 proteins were significantly dysregulated (log2FC ≥0.6/≤-0.6, FDR≤0.05), predicting downregulation in lipid transport (apolipoproteins), fibrinolytic system, and extracellular matrix structural proteins (talin 1, profilin 1); and upregulation in the respiratory burst. Increasing RV size and decreasing RV function correlated with decreasing structural protein expression. Similarly, miR expression predicted downregulation of extracellular matrix-receptor interactions and upregulation in collagen synthesis. Conclusion: To our knowledge, we show for the first time a noninvasive protein and miR signature reflecting the systemic response to adverse RV myocardial remodeling in TOF/PA/MAPCAs which could be used to follow disease progression.

Biomarkers, Socioeconomic Factors, and Right Ventricular Function After Surgical Repair for Tetralogy of Fallot.

Right ventricular (RV) dysfunction early after tetralogy of Fallot (TOF) increases post-operative morbidity. We investigated associations of circulating biomarkers and socioeconomic factors with early post-operative RV systolic function. Single-center prospective cohort study of infants undergoing TOF repair. Six serologic biomarkers of myocardial fibrosis and wall stress collected at the time of surgery were measured with immunoassay. Geocoding was performed for socioeconomic factors. Multivariate adaptive regression splines (MARS) models identified factors associated with RV function parameters: fractional area change (FAC), global longitudinal strain and strain rate, and free wall strain and strain rate. Seventy-one patients aged 3.5 months (IQR 2.4, 5.2) were included. Galectin-3 was the highest ranked predictor for FAC, global longitudinal strain, and free wall strain, and procollagen type-I carboxy-terminal propeptide (PICP) was the highest ranked predictor for global longitudinal strain rate and free wall strain rate. Several neighborhood characteristics were also highly ranked. Models adjusted R2 ranged from 0.71 to 0.85 (FAC, global longitudinal strain/strain rate), and 0.55-0.57 (RV free wall strain/strain rate). A combination of serologic biomarkers, socioeconomic, and clinical variables explain a significant proportion of the variability in RV function after TOF repair. These factors may inform pre-operative risk-stratification for these patients.

A process for academic societies to develop scientific statements and white papers: experience of the Pediatric Cardiac Intensive Care Society.

There are substantial knowledge gaps, practice variation, and paucity of controlled trials owing to the relatively small number of patients with critical heart disease. The Pediatric Cardiac Intensive Care Society has recognised this knowledge gap as an area needing a more comprehensive and evidence-based approach to the management of the critically ill child with heart disease. To address this, the Pediatric Cardiac Intensive Care Society created a scientific statements and white papers committee. Scientific statements and white papers will present the current state-of-the-art in areas where controversy exists, providing clinicians with guidance in diagnostic and therapeutic strategies, particularly where evidence-based data are lacking. This paper provides a template for other societies and organisations faced with the task of developing scientific statements and white papers. We describe the methods used to perform a systematic literature search and evidence rating that will be used by all scientific statements and white papers emerging from the Pediatric Cardiac Intensive Care Society. The Pediatric Cardiac Intensive Care Society aims to revolutionise the care of children with heart disease by shifting our efforts from individual institution-based practices to national standardised protocols and to lay the ground work for multicentre high-impact research directions.

miR-21 is associated with fibrosis and right ventricular failure.

Combined pulmonary insufficiency (PI) and stenosis (PS) is a common long-term sequela after repair of many forms of congenital heart disease, causing progressive right ventricular (RV) dilation and failure. Little is known of the mechanisms underlying this combination of preload and afterload stressors. We developed a murine model of PI and PS (PI+PS) to identify clinically relevant pathways and biomarkers of disease progression. Diastolic dysfunction was induced (restrictive RV filling, elevated RV end-diastolic pressures) at 1 month after generation of PI+PS and progressed to systolic dysfunction (decreased RV shortening) by 3 months. RV fibrosis progressed from 1 month (4.4% ± 0.4%) to 3 months (9.2% ± 1%), along with TGF-ß signaling and tissue expression of profibrotic miR-21. Although plasma miR-21 was upregulated with diastolic dysfunction, it was downregulated with the onset of systolic dysfunction), correlating with RV fibrosis. Plasma miR-21 in children with PI+PS followed a similar pattern. A model of combined RV volume and pressure overload recapitulates the evolution of RV failure unique to patients with prior RV outflow tract surgery. This progression was characterized by enhanced TGF-ß and miR-21 signaling. miR-21 may serve as a plasma biomarker of RV failure, with decreased expression heralding the need for valve replacement.

Institution of Veno-arterial Extracorporeal Membrane Oxygenation Does Not Lead to Increased Wall Stress in Patients with Impaired Myocardial Function.

The effect of veno-arterial extracorporeal membrane oxygenation (VA ECMO) on wall stress in patients with cardiomyopathy, myocarditis, or other cardiac conditions is unknown. We set out to determine the circumferential and meridional wall stress (WS) in patients with systemic left ventricles before and during VA ECMO. We established a cohort of patients with impaired myocardial function who underwent VA ECMO therapy from January 2000 to November 2013. Demographic and clinical data were collected and inotropic score calculated. Measurements were taken on echocardiograms prior to the initiation of VA ECMO and while on full-flow VA ECMO, in order to derive wall stress (circumferential and meridional), VCFc, ejection fraction, and fractional shortening. A post hoc sub-analysis was conducted, separating those with pulmonary hypertension (PH) and those with impaired systemic output. Thirty-three patients met inclusion criteria. The patients' median age was 0.06 years (range 0-18.7). Eleven (33%) patients constituted the organ failure group (Gr2), while the remaining 22 (66%) patients survived to discharge (Gr1). WS and all other echocardiographic measures were not different when comparing patients before and during VA ECMO. Ejection and shortening fraction, WS, and VCFc were not statistically different comparing the survival and organ failure groups. The patients' position on the VCFc-WS curve did not change after the initiation of VA ECMO. Those with PH had decreased WS as well as increased EF after ECMO initiation, while those with impaired systemic output showed no difference in those parameters with initiation of ECMO. The external workload on the myocardium as indicated by WS is unchanged by the institution of VA ECMO support. Furthermore, echocardiographic measures of cardiac function do not reflect the changes in ventricular performance inherent to VA ECMO support. These findings are informative for the interpretation of echocardiograms in the setting of VA ECMO. ECMO may improve ventricular mechanics in those with PH as the primary diagnosis.

Compassionate deactivation of ventricular assist devices in pediatric patients.

Despite greatly improved survival in pediatric patients with end-stage heart failure through the use of ventricular assist devices (VADs), heart failure ultimately remains a life-threatening disease with a significant symptom burden. With increased demand for donor organs, liberalizing the boundaries of case complexity, and the introduction of destination therapy in children, more children can be expected to die while on mechanical support. Despite this trend, guidelines on the ethical and pragmatic issues of compassionate deactivation of VAD support in children are strikingly absent. As VAD support for pediatric patients increases in frequency, the pediatric heart failure and palliative care communities must work toward establishing guidelines to clarify the complex issues surrounding compassionate deactivation. Patient, family and clinician attitudes must be ascertained and education regarding the psychological, legal and ethical issues should be provided. Furthermore, pediatric-specific planning documents for use before VAD implantation as well as deactivation checklists should be developed to assist with decision-making at critical points during the illness trajectory. Herein we review the relevant literature regarding compassionate deactivation with a specific focus on issues related to children.

Time-dependent evolution of functional vs. remodeling signaling in induced pluripotent stem cell-derived cardiomyocytes and induced maturation with biomechanical stimulation.

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are a powerful platform for uncovering disease mechanisms and assessing drugs for efficacy/toxicity. However, the accuracy with which hiPSC-CMs recapitulate the contractile and remodeling signaling of adult cardiomyocytes is not fully known. We used ß-adrenergic receptor (ß-AR) signaling as a prototype to determine the evolution of signaling component expression and function during hiPSC-CM maturation. In "early" hiPSC-CMs (less than or equal to d 30), ß2-ARs are a primary source of cAMP/PKA signaling. With longer culture, ß1-AR signaling increases: from 0% of cAMP generation at d 30 to 56.8 ± 6.6% by d 60. PKA signaling shows a similar increase: 15.7 ± 5.2% (d 30), 49.8 ± 0.5% (d 60), and 71.0 ± 6.1% (d 90). cAMP generation increases 9-fold from d 30 to 60, with enhanced coupling to remodeling pathways (e.g., Akt and Ca(2+)/calmodulin-dependent protein kinase type II) and development of caveolin-mediated signaling compartmentalization. By contrast, cardiotoxicity induced by chronic ß-AR stimulation, a major component of heart failure, develops much later: 5% cell death at d 30vs 55% at d 90. Moreover, ß-AR maturation can be accelerated by biomechanical stimulation. The differential maturation of ß-AR functionalvs remodeling signaling in hiPSC-CMs has important implications for their use in disease modeling and drug testing. We propose that assessment of signaling be added to the indices of phenotypic maturation of hiPSC-CMs.-Jung, G., Fajardo, G., Ribeiro, A. J. S., Kooiker, K. B., Coronado, M., Zhao, M., Hu, D.-Q., Reddy, S., Kodo, K., Sriram, K., Insel, P. A., Wu, J. C., Pruitt, B. L., Bernstein, D. Time-dependent evolution of functionalvs remodeling signaling in induced pluripotent stem cell-derived cardiomyocytes and induced maturation with biomechanical stimulation.

Deletion of the ß2-adrenergic receptor prevents the development of cardiomyopathy in mice.

Beta adrenergic receptor (ß-AR) subtypes act through diverse signaling cascades to modulate cardiac function and remodeling. Previous in vitro studies suggest that ß1-AR signaling is cardiotoxic whereas ß2-AR signaling is cardioprotective, and may be the case during ischemia/reperfusion in vivo. The objective of this study was to assess whether ß2-ARs also play a cardioprotective role in the pathogenesis of non-ischemic forms of cardiomyopathy. To dissect the role of ß1 vs ß2-ARs in modulating MLP (Muscle LIM Protein) cardiomyopathy, we crossbred MLP-/- with ß1-/- or ß2-/- mice. Deletion of the ß2-AR improved survival, cardiac function, exercise capacity and myocyte shortening; by contrast haploinsufficency of the ß1-AR reduced survival. Pathologic changes in Ca(2+) handling were reversed in the absence of ß2-ARs: peak Ca(2+) and SR Ca(2+) were decreased in MLP-/- and ß1+/-/MLP-/- but restored in ß2-/-MLP-/-. These changes were associated with reversal of alterations in troponin I and phospholamban phosphorylation. Gi inhibition increased peak and baseline Ca(2+), recapitulating changes observed in the ß2-/-/MLP-/-. The L-type Ca(2+) blocker verapamil significantly decreased cardiac function in ß2-/-MLP-/- vs WT. We next tested if the protective effects of ß2-AR ablation were unique to the MLP model using TAC-induced heart failure. Similar to MLP, ß2-/- mice demonstrated delayed progression of heart failure with restoration of myocyte shortening and peak Ca(2+) and Ca(2+) release. Deletion of ß2-ARs prevents the development of MLP-/- cardiomyopathy via positive modulation of Ca(2+) due to removal of inhibitory Gi signaling and increased phosphorylation of troponin I and phospholamban. Similar effects were seen after TAC. Unlike previous models where ß2-ARs were found to be cardioprotective, in these two models, ß2-AR signaling appears to be deleterious, potentially through negative regulation of Ca(2+) dynamics.

FK506 activates BMPR2, rescues endothelial dysfunction, and reverses pulmonary hypertension.

Dysfunctional bone morphogenetic protein receptor-2 (BMPR2) signaling is implicated in the pathogenesis of pulmonary arterial hypertension (PAH). We used a transcriptional high-throughput luciferase reporter assay to screen 3,756 FDA-approved drugs and bioactive compounds for induction of BMPR2 signaling. The best response was achieved with FK506 (tacrolimus), via a dual mechanism of action as a calcineurin inhibitor that also binds FK-binding protein-12 (FKBP12), a repressor of BMP signaling. FK506 released FKBP12 from type I receptors activin receptor-like kinase 1 (ALK1), ALK2, and ALK3 and activated downstream SMAD1/5 and MAPK signaling and ID1 gene regulation in a manner superior to the calcineurin inhibitor cyclosporine and the FKBP12 ligand rapamycin. In pulmonary artery endothelial cells (ECs) from patients with idiopathic PAH, low-dose FK506 reversed dysfunctional BMPR2 signaling. In mice with conditional Bmpr2 deletion in ECs, low-dose FK506 prevented exaggerated chronic hypoxic PAH associated with induction of EC targets of BMP signaling, such as apelin. Low-dose FK506 also reversed severe PAH in rats with medial hypertrophy following monocrotaline and in rats with neointima formation following VEGF receptor blockade and chronic hypoxia. Our studies indicate that low-dose FK506 could be useful in the treatment of PAH.

Physiologic and molecular characterization of a murine model of right ventricular volume overload.

Pulmonary insufficiency (PI) is a common long-term sequel after repair of tetralogy of Fallot, causing progressive right ventricular (RV) dilation and failure. We describe the physiologic and molecular characteristics of the first murine model of RV volume overload. PI was created by entrapping the pulmonary valve leaflets with sutures. Imaging, catheterization, and exercise testing were performed at 1, 3, and 6 mo and compared with sham controls. RNA from the RV free wall was hybridized to Agilent whole genome oligonucleotide microarrays. Volume overload resulted in RV enlargement, decreased RV outflow tract shortening fraction at 1 mo followed by normalization at 3 and 6 mo (39 ± 2, 44 ± 2, and 41 ± 2 vs. 46 ± 3% in sham), early reversal of early and late diastolic filling velocities (E/A ratio) followed by pseudonormalization (0.87 ± 0.08, 0.82 ± 0.08, and 0.96 ± 0.08 vs. 1.04 ± 0.03; P < 0.05), elevated end-diastolic pressure (7.6 ± 0.7, 6.9 ± 0.8, and 7 ± 0.5 vs. 2.7 ± 0.2 mmHg; P < 0.05), and decreased exercise duration (26 ± 0.4, 26 ± 1, and 22 ± 1.3 vs. 30 ± 1.1 min; P < 0.05). Subendocardial RV fibrosis was evident by 1 mo. At 1 mo, 372 genes were significantly downregulated. Mitochondrial pathways and G protein-coupled receptor signaling were the most represented categories. At 3 mo, 434 genes were upregulated and 307 downregulated. While many of the same pathways continued to be downregulated, TNF-α, transforming growth factor-ß(1) (TGF-ß(1)), p53-signaling, and extracellular matrix (ECM) remodeling transitioned from down- to upregulated. We describe a novel murine model of chronic RV volume overload recapitulating aspects of the clinical disease with gene expression changes suggesting early mitochondrial bioenergetic dysfunction, enhanced TGF-ß signaling, ECM remodeling, and apoptosis.

Loss of Hfe leads to progression of tumor phenotype in primary retinal pigment epithelial cells.

PURPOSE: Hemochromatosis is a disorder of iron overload arising mostly from mutations in HFE. HFE is expressed in retinal pigment epithelium (RPE), and Hfe(-/-) mice develop age-related iron accumulation and retinal degeneration associated with RPE hyperproliferation. Here, the mechanism underlying the hyperproliferative phenotype in RPE was investigated. METHODS: Cellular senescence was monitored by ß-galactosidase activity. Gene expression was monitored by real-time PCR. Survivin was analyzed by Western blot and immunofluorescence. Migration and invasion were monitored using appropriate kits. Glucose transporters (GLUTs) were monitored by 3-O-methyl-D-glucose uptake. Histone deacetylases (HDACs) were studied by monitoring catalytic activity and acetylation status of histones H3/H4. RESULTS: Hfe(-/-) RPE cells exhibited slower senescence rate and higher survivin expression than wild type cells. Hfe(-/-) cells migrated faster and showed greater glucose uptake and increased expression of GLUTs. The expression of HDACs and DNA methyltransferase (DNMTs) also was increased. Similarly, RPE cells from hemojuvelin (Hjv)-knockout mice, another model of hemochromatosis, also had increased expression of GLUTs, HDACs, and DNMTs. The expression of Slc5a8 was decreased in Hfe(-/-) RPE cells, but treatment with a DNA methylation inhibitor restored the transporter expression, indicating involvement of DNA methylation in the silencing of Slc5a8 in Hfe(-/-) cells. CONCLUSIONS: RPE cells from iron-overloaded mice exhibit several features of tumor cells: decreased senescence, enhanced migration, increased glucose uptake, and elevated levels of HDACs and DNMTs. These features are seen in Hfe(-/-) RPE cells as well as in Hjv(-/-) RPE cells, providing a molecular basis for the hyperproliferative phenotype of Hfe(-/-) and Hjv(-/-) RPE cells.

Dynamic microRNA expression during the transition from right ventricular hypertrophy to failure.

MicroRNAs (miRs) are small, noncoding RNAs that are emerging as crucial regulators of cardiac remodeling in left ventricular hypertrophy (LVH) and failure (LVF). However, there are no data on their role in right ventricular hypertrophy (RVH) and failure (RVF). This is a critical question given that the RV is uniquely at risk in patients with congenital right-sided obstructive lesions and in those with systemic RVs. We have developed a murine model of RVH and RVF using pulmonary artery constriction (PAC). miR microarray analysis of RV from PAC vs. control demonstrates altered miR expression with gene targets associated with cardiomyocyte survival and growth during hypertrophy (miR 199a-3p) and reactivation of the fetal gene program during heart failure (miR-208b). The transition from hypertrophy to heart failure is characterized by apoptosis and fibrosis (miRs-34, 21, 1). Most are similar to LVH/LVF. However, there are several key differences between RV and LV: four miRs (34a, 28, 148a, and 93) were upregulated in RVH/RVF that are downregulated or unchanged in LVH/LVF. Furthermore, there is a corresponding downregulation of their putative target genes involving cell survival, proliferation, metabolism, extracellular matrix turnover, and impaired proteosomal function. The current study demonstrates, for the first time, alterations in miRs during the process of RV remodeling and the gene regulatory pathways leading to RVH and RVF. Many of these alterations are similar to those in the afterload-stressed LV. miRs differentially regulated between the RV and LV may contribute to the RVs increased susceptibility to heart failure.

Polarized distribution of heme transporters in retinal pigment epithelium and their regulation in the iron-overload disease hemochromatosis.

PURPOSE: FLVCR, BCRP, and PCFT/HCP-1 represent the three heme transporters identified thus far in mammalian cells, but there is very little known about their expression and regulation in the retina. In this study, the expression of these transporters in mouse retina and retinal pigment epithelium (RPE) and their regulation in the iron-overload disease hemochromatosis were examined. METHODS: The expression of FLVCR, BCRP, and PCFT in mouse retina and primary mouse RPE cells was studied by RT-PCR and immunofluorescence. Polarized localization of the transporters in RPE was studied by co-localization using a specific marker of the RPE apical membrane. Uptake of heme in primary RPE cells was determined using zinc-mesoporphyrin, a fluorescent heme analogue. The regulation of heme transporters by iron overload was studied in two genetic models of hemochromatosis (HFE-null mouse and HJV-null mouse) and in two nongenetic models of iron overload (cytomegalovirus infection and treatment with ferric ammonium citrate). RESULTS: All three heme transporters were expressed in the retina and RPE. In the RPE, the expression of FLVCR was restricted to the apical membrane, and the expression of BCRP and PCFT was restricted to the basolateral membrane. In all cases of iron overload, the expression of FLVCR and PCFT was upregulated and that of BCRP was downregulated. CONCLUSIONS: Hemochromatosis is associated not only with excessive accumulation of free iron in the retina and RPE but also with excessive accumulation of heme. Since heme is toxic at high levels, as is free iron, heme-induced oxidative damage may also play a role in hemochromatosis-associated retinal pathology.

Recipient genotype is a predictor of allograft cytokine expression and outcomes after pediatric cardiac transplantation.

OBJECTIVES: This study sought to investigate the influence of recipient renin-angiotensin-aldosterone system (RAAS) genotype on cardiac function, rejection, and outcomes after heart transplantation. BACKGROUND: The RAAS influences cardiac function and up-regulates inflammatory/immune pathways. Little is known about the effect of recipient RAAS polymorphisms in pediatric cardiac transplantation. METHODS: Patients <25 years of age, after cardiac transplantation, were enrolled (2003 to 2008) and genotyped for polymorphisms in genes associated with RAAS upregulation: AGT-G, ACE-D, AGTR1-C, CYP11B2-G, and CMA-A. Presence of at least 1 high-risk allele was defined as a high-risk genotype. Univariable and multivariable associations between genotypes and outcomes were assessed in time-dependent models using survival, logistic, or linear regression models. Biopsy samples were immunostained for interleukin (IL)-6, transforming growth factor (TGF)-beta, and tumor necrosis factor (TNF)-alpha during rejection and quiescence. RESULTS: A total of 145 patients were studied, 103 primary cohort and 42 replication cohort; 81% had rejection, 51% had graft dysfunction, and 13% had vasculopathy, 7% died and 8% underwent re-transplantation. A higher number of homozygous high-risk RAAS genotypes was associated with a higher risk of graft dysfunction (hazard ratio [HR]: 1.5, p = 0.02) and a higher probability of death (HR: 2.5, p = 0.04). The number of heterozygous high-risk RAAS genotypes was associated with frequency of rejection (+0.096 events/year, p < 0.001) and rejection-associated graft dysfunction (+0.37 events/year, p = 0.002). IL-6 and TGF-beta were markedly upregulated during rejection in patients with >/=2 high-risk RAAS genotypes. CONCLUSIONS: Recipient RAAS polymorphisms are associated with a higher risk of rejection, graft cytokine expression, graft dysfunction, and a higher mortality after cardiac transplantation. This may have implications for use of RAAS inhibitors in high-risk patients after transplantation.

Genomic profiling of left and right ventricular hypertrophy in congenital heart disease.

BACKGROUND: The right ventricle (RV) has a lower ability than the left ventricle (LV) to adapt to systemic load. The molecular basis of these differences is not known. We compared hypertrophy-signaling pathways between the RV and the LV in patients with congenital heart disease (CHD). METHODS: Gene expression was measured using DNA microarrays in myocardium from children with CHD with LV or RV obstructive lesions undergoing surgery. The expression of 175 hypertrophy-signaling genes was compared between the LV (n=7) and the RV (n=11). Hierarchic clustering was performed. RESULTS: Seventeen genes (10%) were differentially expressed between the LV and the RV. Expression of genes for angiotensin, adrenergic, G-proteins, cytoskeletal, and contractile components was lower (P < .05) and expression of maladaptive factors (fibroblast growth factors, transforming growth factor-beta, caspases, ubiquitin) was higher in the RV compared with the LV (P < .05). Five of 7 LV samples clustered together. Only 4 of 11 RV samples clustered with the LV. Genes critical to adaptive remodeling correlated with the degree of LV hypertrophy but not RV hypertrophy. CONCLUSION: The transcription of pathways of adaptive remodeling was lower in the RV compared with the LV. This may explain the lower ability of the RV to adapt to hemodynamic load in CHD.

Phylogenomic evidence for multiple losses of flight in ratite birds.

Ratites (ostriches, emus, rheas, cassowaries, and kiwis) are large, flightless birds that have long fascinated biologists. Their current distribution on isolated southern land masses is believed to reflect the breakup of the paleocontinent of Gondwana. The prevailing view is that ratites are monophyletic, with the flighted tinamous as their sister group, suggesting a single loss of flight in the common ancestry of ratites. However, phylogenetic analyses of 20 unlinked nuclear genes reveal a genome-wide signal that unequivocally places tinamous within ratites, making ratites polyphyletic and suggesting multiple losses of flight. Phenomena that can mislead phylogenetic analyses, including long branch attraction, base compositional bias, discordance between gene trees and species trees, and sequence alignment errors, have been eliminated as explanations for this result. The most plausible hypothesis requires at least three losses of flight and explains the many morphological and behavioral similarities among ratites by parallel or convergent evolution. Finally, this phylogeny demands fundamental reconsideration of proposals that relate ratite evolution to continental drift.

Failure of right ventricular adaptation in children with tetralogy of Fallot.

BACKGROUND: The left ventricle (LV) adapts to chronic hypoxia by expressing protective angiogenic, metabolic, and antioxidant genes to improve O2 delivery and energy production, and to minimize reoxygenation injury. The ability of the right ventricle (RV) to adapt to hypoxia in children with tetralogy of Fallot (TOF) is unknown. METHODS AND RESULTS: Gene expression using real-time polymerase chain reaction was measured in RV myocardium obtained during surgical repair of TOF from 23 patients: 13 cyanotic and 10 acyanotic. Results were compared between the 2 groups and correlated with age at surgery, severity of cyanosis, and early postoperative course. The cyanotic patients were younger at surgery compared with acyanotic (5+/-3 versus 9+/-4 months; P=0.01), had higher hematocrit (43+/-4 versus 38+/-3 grams/dL; P=0.004), and lower O2 saturations (84+/-4% versus 98+/-2%; (P<0.001). Cyanotic patients had a significantly lower expression of vascular endothelial growth factor (VEGF), glycolytic enzymes, and glutathione peroxidase (GPX) (P<0.05), and a higher expression of collagen (P<0.01) compared with acyanotic patients. Gene expression correlated inversely with severity of cyanosis ie, preoperative hematocrit (P<0.01) and positively with preoperative saturation (P<0.05). The relationship between gene expression and cyanosis was independent of age at surgery. Ca2+ handling genes did not correlate with the severity of hypoxia. Lower angiogenic, glycolytic, and antioxidant gene expression correlated with increasing postoperative lactate (P<0.05). CONCLUSIONS: The RV fails to up regulate adaptive pathways in response to increasing hypoxia in children with TOF. The implications of an early maladaptive response of the RV on long-term RV function require further investigation.

Inlet patch: heterotopic gastric mucosa--another contributor to supraesophageal symptoms?

OBJECTIVE: To determine prospectively the incidence of an inlet patch (IP) in children requiring esophagogastroduodenoscopy (EGD) and assess the prevalence of presenting symptoms between children with and without an IP. STUDY DESIGN: All patients undergoing EGD in a 2-year period were assessed for the presence of an IP with biopsy confirmation. IP, distal esophagus, and stomach biopsy specimens were blindly reviewed by a pathologist for the presence and degree of inflammation and intestinal metaplasia. Symptoms from children with and without an IP were compared. RESULTS: From 407 EGDs done by a single endoscopist, 24 patients had confirmed IP (incidence of 5.9%). The presence and degree of inflammation were always relatively greater in the columnar mucosa of the IP than in the antral/body gastric mucosa in the same patient (P = .0027) Inflammation was similar in the squamous epithelium around the IP and in the distal esophagus (P=.46). Two patients had intestinal metaplasia of the IP. The patients with IPs had a higher prevalence of respiratory symptoms than the control group (P = .03). CONCLUSIONS: Children with IPs may have a higher frequency of respiratory symptoms. Periodic surveillance should be performed in children with intestinal metaplasia of an IP.