Background: Protein-losing enteropathy (PLE) is a severe complication of the univentricular Fontan circulation and associated with disturbances in salt and water homeostasis. Fontan patients with PLE ...have a poor prognosis, with increased morbidity and mortality. Due to limited therapeutic strategies, patients are often treated only symptomatically. Methods: We report our first experience of Tolvaptan (TLV) treatment in a Fontan patient with PLE, severe volume retention and hyponatraemia, refractory to conventional diuretic therapy. In addition to clinical parameters, we monitored drug effects including tissue sodium and volume status via serial 23 Na-magnetic resonance imaging ( 23 Na-MRI) and bioimpedance spectroscopy compared with age-matched controls. Results: 23 Na-MRI identified elevated tissue sodium, which decreased under TLV treatment, as well as volume status, while serum sodium increased and the patient’s symptoms improved. During long-term treatment, we were able to differentiate between sodium and volume status in our patient, suggesting that TLV uncoupled body sodium from water. Conclusion: TLV in addition to loop diuretics improved clinical symptoms of PLE and lowered tissue sodium overload. Long-term effects should be further evaluated in Fontan patients.
OBJECTIVES
This retrospective study evaluated the feasibility and related outcome of intraluminal pulmonary artery banding (I-PAB).
METHODS
Thirty-two children underwent I-PAB between July 2006 and ...April 2014. The median age and weight were 60 days (range: 5 days to 4.2 years) and 3.7 kg (range: 2.6–13.0 kg), respectively. Cardiac diagnoses included single ventricle morphology (n = 11), complex ventricular septal defects (n = 11), balanced atrioventricular septal defects (n = 3), congenitally corrected transposition of the great arteries (n = 2) and aortic arch hypoplasia with ventricular septal defects (n = 5). On cardiopulmonary bypass (CPB), 2 I-PAB modifications with either 1 (n = 24) or 2 (‘hour-glass-technique’, n = 8) fenestrated pericardial patches were performed.
RESULTS
The median fenestration size was 5 mm (range: 4–6.5 mm). In 18 patients I-PAB was a solitary procedure; in 3 of them the decision was made intraoperatively. There was no hospital mortality. The median interval to debanding was 189 days (range: 112 days to 2.6 years). During this period, we observed a significant increase in the pressure gradient over I-PAB (P < 0.01), whereas arterial saturations remained stable. Four patients received balloon dilatation of I-PAB to prolong the palliation period. No patient experienced band occlusion, pulmonary hypertension related to I-PAB, coronary or pulmonary valve impairment. Debanding was performed in 27 patients and one of them required pulmonary patch arterioplasty due to I-PAB-associated pulmonary trunk distortion. Three patients are still awaiting further surgery. There were 2 late deaths prior to, and 3 after debanding, all not related to I-PAB.
CONCLUSIONS
I-PAB with an exactly defined internal orifice is feasible and effective. Although arterial saturations seem to remain stable, balloon dilatation of I-PAB can be performed safely and efficiently in order to prolong the palliation period. The rate of I-PAB-related complications is low, which might improve the long-term patient outcome. Therefore, despite requiring CPB, I-PAB is our institutional preference for children who require pulmonary artery banding.
Autosomal-dominant hypertension and brachydactyly (Online Mendelian Inheritance in Man 112410) is a prototype-translational research project. We used interphase fluorescent in situ hybridization and ...discovered complex rearrangements on chromosome 12p in 5 families but elucidated a common inverted region in the linkage interval. The inversion contains no known gene. However, we found 5 expressed sequence tags in databases. We used 5′- and 3′-Rapid Amplification of cDNA Ends PCR for elongation of the transcripts in phenotype-relevant tissue (fetal aorta, fetal brain, and fetal cartilage). We detected tissue-specific multiple splicing with different exon usage of 32 exons in the gene-related structure. These different transcripts lack both open reading frames and Kozak sequences. In vitro transcription/translation experiments did not identify any peptide-related molecules. We then performed quantitative RT-PCR to test for differential expression of the various spliced transcripts in the total fibroblast RNA of affected and nonaffected Turkish family members. Skin fibroblasts of affected individuals have a significantly increased proliferation rate compared with nonaffected individuals. Ten of 12 spliced exon combinations representing all of the spliced variants do not show a significantly different RNA expression rate. However, 2 RT-PCR products are exclusively expressed in nonaffected individuals. Both reverse transcription amplicons share 1 exon. This result is surprising because of the autosomal-dominant mode of inheritance of the trait. RNA secondary prediction of this single exon results in a stable stem-loop structure known to be essential for microRNA processing. We are pursuing the possibility of microRNA expression in affected patients that leads to complete down regulation of a spliced transcript.
Congenital heart defects (CHDs) have a neonatal incidence of 0.8-1% (refs. 1,2). Despite abundant examples of monogenic CHD in humans and mice, CHD has a low absolute sibling recurrence risk (∼2.7%), ...suggesting a considerable role for de novo mutations (DNMs) and/or incomplete penetrance. De novo protein-truncating variants (PTVs) have been shown to be enriched among the 10% of 'syndromic' patients with extra-cardiac manifestations. We exome sequenced 1,891 probands, including both syndromic CHD (S-CHD, n = 610) and nonsyndromic CHD (NS-CHD, n = 1,281). In S-CHD, we confirmed a significant enrichment of de novo PTVs but not inherited PTVs in known CHD-associated genes, consistent with recent findings. Conversely, in NS-CHD we observed significant enrichment of PTVs inherited from unaffected parents in CHD-associated genes. We identified three genome-wide significant S-CHD disorders caused by DNMs in CHD4, CDK13 and PRKD1. Our study finds evidence for distinct genetic architectures underlying the low sibling recurrence risk in S-CHD and NS-CHD.
Cardiovascular disease is the most common cause of death worldwide, and hypertension is the major risk factor. Mendelian hypertension elucidates mechanisms of blood pressure regulation. Here we ...report six missense mutations in PDE3A (encoding phosphodiesterase 3A) in six unrelated families with mendelian hypertension and brachydactyly type E (HTNB). The syndrome features brachydactyly type E (BDE), severe salt-independent but age-dependent hypertension, an increased fibroblast growth rate, neurovascular contact at the rostral-ventrolateral medulla, altered baroreflex blood pressure regulation and death from stroke before age 50 years when untreated. In vitro analyses of mesenchymal stem cell-derived vascular smooth muscle cells (VSMCs) and chondrocytes provided insights into molecular pathogenesis. The mutations increased protein kinase A-mediated PDE3A phosphorylation and resulted in gain of function, with increased cAMP-hydrolytic activity and enhanced cell proliferation. Levels of phosphorylated VASP were diminished, and PTHrP levels were dysregulated. We suggest that the identified PDE3A mutations cause the syndrome. VSMC-expressed PDE3A deserves scrutiny as a therapeutic target for the treatment of hypertension.
Mutations in sarcomere protein genes can cause hypertrophic cardiomyopathy (HCM), a disorder characterized by myocyte enlargement, fibrosis, and impaired ventricular relaxation. Here, we demonstrate ...that sarcomere protein gene mutations activate proliferative and profibrotic signals in non-myocyte cells to produce pathologic remodeling in HCM. Gene expression analyses of non-myocyte cells isolated from HCM mouse hearts showed increased levels of RNAs encoding cell-cycle proteins, Tgf-β, periostin, and other profibrotic proteins. Markedly increased BrdU labeling, Ki67 antigen expression, and periostin immunohistochemistry in the fibrotic regions of HCM hearts confirmed the transcriptional profiling data. Genetic ablation of periostin in HCM mice reduced but did not extinguish non-myocyte proliferation and fibrosis. In contrast, administration of Tgf-β-neutralizing antibodies abrogated non-myocyte proliferation and fibrosis. Chronic administration of the angiotensin II type 1 receptor antagonist losartan to mutation-positive, hypertrophy-negative (prehypertrophic) mice prevented the emergence of hypertrophy, non-myocyte proliferation, and fibrosis. Losartan treatment did not reverse pathologic remodeling of established HCM but did reduce non-myocyte proliferation. These data define non-myocyte activation of Tgf-β signaling as a pivotal mechanism for increased fibrosis in HCM and a potentially important factor contributing to diastolic dysfunction and heart failure. Preemptive pharmacologic inhibition of Tgf-β signals warrants study in human patients with sarcomere gene mutations.
Finding genes that cause human hypertension is not straightforward, since the determinants of blood pressure in primary hypertension are multifactorial. One approach to identifying relevant genes is ...to elucidate rare forms of monogenic hypertension. A relevant mutation may provide a rational starting point from which to analyse the pathophysiology of a condition affecting 20% of the world's population. In 1973 a family with autosomal dominantly inherited brachydactyly and severe hypertension, where the two traits cosegregated completely, was described. We have now re-examined this kindred, and localized the hypertension and brachydactyly locus to chromosome 12p in a region defined by markers D12S364 and D12S87. As the renin-angiotensin-system and sympathetic nervous system respond normally in this form of hypertension, the condition resembles essential hypertension. This feature distinguishes this form of hypertension from glucocorticoid remediable aldosteronism and Liddle's syndrome, which are salt-sensitive forms of monogenic hypertension with very low plasma renin activity. We suggest that identification of the gene involved in hypertension and brachydactyly and its mutation will be of great relevance in elucidating new mechanisms leading to blood pressure elevation.
Congenital heart defects (CHDs) are the most common birth defect worldwide and are a leading cause of neonatal mortality. Nonsyndromic atrioventricular septal defects (AVSDs) are an important subtype ...of CHDs for which the genetic architecture is poorly understood. We performed exome sequencing in 13 parent-offspring trios and 112 unrelated individuals with nonsyndromic AVSDs and identified five rare missense variants (two of which arose de novo) in the highly conserved gene NR2F2, a very significant enrichment (p = 7.7 × 10−7) compared to 5,194 control subjects. We identified three additional CHD-affected families with other variants in NR2F2 including a de novo balanced chromosomal translocation, a de novo substitution disrupting a splice donor site, and a 3 bp duplication that cosegregated in a multiplex family. NR2F2 encodes a pleiotropic developmental transcription factor, and decreased dosage of NR2F2 in mice has been shown to result in abnormal development of atrioventricular septa. Via luciferase assays, we showed that all six coding sequence variants observed in individuals significantly alter the activity of NR2F2 on target promoters.
Abstract
Background
Protein-losing enteropathy (PLE) is a severe complication of the Fontan circulation. There is increasing discussion about whether lymphatic dysregulation is involved as ...pathomechanism of PLE. This investigation focuses on the interplay between alteration of lymphatic cells and immunologic pathway alterations.
Methods
Micro-ribonucleic acid (miRNA) expression profiling was performed in 49 patients (
n
= 10 Fontan patients with PLE,
n
= 30 Fontan patients without PLE, and
n
= 9 patients with dextro-transposition of the great arteries (dTGA). miRNA pathway analysis was performed to identify significantly enriched pathways. To determine lymphocyte populations and subtypes multiparameter flow cytometry was used.
Results
miRNAs pathway analysis of Fontan patients with PLE revealed 20 significantly changed networks of which four of the ten largest were associated with immunologic processes. This finding is supported by significant T cell deficiency with decreased CD4+ count (
p
= 0.0002), altered CD4 +/CD8+ ratio, and significantly modified CD4+ (
p
< 0.0001) and CD8+ (
p
= 0.0002) T cell differentiation toward effector and terminal differentiated T cells in Fontan patients with PLE. Analyses of CD4+ T cell subsets demonstrated significantly increased frequencies of CD4+ CD25+ CD127– regulatory T cells (Treg) in Fontan patients with PLE (
p
= 0.0011).
Conclusion
PLE in Fontan patients is associated with severe lymphopenia, T cell deficiency, significant alterations of T cell differentiation, and increased Treg frequency reflecting an immune status of chronic inflammation and shortened protection against pathogens and autoimmunity. These cellular alterations seemed to be dysregulated by several miRNA controlled immunological pathways.
Autosomal-dominant hypertension with brachydactyly is a salt-independent Mendelian syndrome caused by activating mutations in the gene encoding phosphodiesterase 3A. These mutations increase the ...protein kinase A–mediated phosphorylation of phosphodiesterase 3A resulting in enhanced cAMP-hydrolytic affinity and accelerated cell proliferation. The phosphorylated vasodilator-stimulated phosphoprotein is diminished, and parathyroid hormone-related peptide is dysregulated, potentially accounting for all phenotypic features. Untreated patients die prematurely of stroke; however, hypertension-induced target-organ damage is otherwise hardly apparent. We conducted clinical studies of vascular function, cardiac functional imaging, platelet function in affected and nonaffected persons, and cell-based assays. Large-vessel and cardiac functions indeed seem to be preserved. The platelet studies showed normal platelet function. Cell-based studies demonstrated that available phosphodiesterase 3A inhibitors suppress the mutant isoforms. However, increasing cGMP to indirectly inhibit the enzyme seemed to have particular use. Our results shed more light on phosphodiesterase 3A activation and could be relevant to the treatment of severe hypertension in the general population.
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