Genetics of patent ductus arteriosus susceptibility and treatment

Whole-exome sequencing analysis of patent ductus arteriosus in a Japanese macaque (Macaca fuscata)

We performed whole-exome sequencing using a human exome capture kit to analyze the potential genetic factors related to patent ductus arteriosus in Japanese macaques. Compared with the reference sequences of other primates, we identified potential missense variants in five genes: ADAM15, AZGP1, CSPG4, TNFRSF13B, and EPOR.

Vav2 promotes ductus arteriosus anatomic closure via the remodeling of smooth muscle cells by Rac1 activation

The ductus arteriosus (DA), bridging the aorta and pulmonary artery, immediately starts closing after birth. Remodeling of DA leads to anatomic obstruction to prevent repatency. Several histological changes, especially extracellular matrices (ECMs) deposition and smooth muscle cells (SMCs) migration bring to anatomic closure. The genetic etiology and mechanism of DA closure remain elusive. We have previously reported a novel copy number variant containing Vav2 in patent ductus arteriosus (PDA) patients, but its specific role in DA closure remains unknown. The present study revealed that the expression of Vav2 was reduced in human patent DA, and it was less enrichment in the adjacent aorta. Matrigel experiments demonstrated that Vav2 could promote SMC migration from PDA patient explants. Smooth muscle cells with Vav2 overexpression also presented an increased capacity in migration and downregulated contractile-related proteins. Meanwhile, SMCs with Vav2 overexpression exhibited higher expression of collagen III and lessened protein abundance of lysyl oxidase, and both changes are beneficial to DA remodeling. Overexpression of Vav2 resulted in increased activity of Rac1, Cdc42, and RhoA in SMCs. Further investigation noteworthily found that the above alterations caused by Vav2 overexpression were particularly reversed by Rac1 inhibitor. A heterozygous, rare Vav2 variant was identified in PDA patients. Compared with the wild type, this variant attenuated Vav2 protein expression and weakened the activation of downstream Rac1, further impairing its functions in SMCs. In conclusion, Vav2 functions as an activator for Rac1 in SMCs to promote SMCs migration, dedifferentiation, and ECMs production. Deleterious variant potentially induces Vav2 loss of function, further providing possible molecular mechanisms about Vav2 in PDA pathogenesis. These findings enriched the current genetic etiology of PDA, which may provide a novel target for prenatal diagnosis and treatment. KEY MESSAGES: Although we have proposed the potential association between Vav2 and PDA incidence through whole exome sequencing, the molecular mechanisms underlying Vav2 in PDA have never been reported. This work, for the first time, demonstrated that Vav2 was exclusively expressed in closed DAs. Moreover, we found that Vav2 participated in the process of anatomic closure by mediating SMCs migration, dedifferentiation, and ECMs deposition through Rac1 activation. Our findings first identified a deleterious Vav2 c.701C>T variant that affected its function in SMCs by impairing Rac1 activation, which may lead to PDA defect. Vav2 may become an early diagnosis and an effective intervention target for PDA clinical therapy.

Echocardiographic parameters predicting spontaneous closure of ductus arteriosus in preterm infants

Objective

To evaluate the value of echocardiographic parameters in predicting early spontaneous closure of ductus arteriosus in premature infants.

Methods

222 premature infants admitted to the neonatal ward of our hospital were selected, and patent ductus arteriosus was detected by echocardiography 48 h after birth. On the 7th day, whether the ductus arteriosus was closed naturally in this cohort was observed. The infants whose ductus arteriosus were not closed were identified as the PDA group (n = 109), and the other infants were included in the control group (n = 113). The echocardiographic parameters of the two groups of premature infants at 48 h after birth were single-factor statistically and Pearson correlation analyzed, and the parameters with statistically significant differences in single-factor analyzed were selected for multivariate logistic stepwise regression analysis.

Results

The ductus arteriosus shunt velocity and the pressure difference between the descending aorta and the pulmonary artery (ΔPs) in the PDA group were lower than those in the control group (P < 0.05). The pulmonary artery pressure (PASP) in the PDA group was higher than that in the control group (P < 0.05). According to the multivariate logistic stepwise regression analysis, only the maximum shunt velocity of ductus arteriosus was correlated with early spontaneous closure of ductus arteriosus in 48 h first echocardiographic parameters (P = 0.049). The receiver operating characteristic (ROC) curve indicates the optimal critical point of echocardiographic ductus arteriosus shunt velocity in premature infants 48 h after birth was 1.165 m/s.

Conclusion

Echocardiographic parameters are of great value in predicting the early spontaneous closure of ductus arteriosus in premature infants. In particular, the ductus arteriosus shunt velocity is correlated with the early spontaneous closure of ductus arteriosus.

Using omics to breathe new life into our understanding of the ductus arteriosus oxygen response

The ductus arteriosus (DA) connects the aorta to the pulmonary artery (PA), directing placentally oxygenated blood away from the developing lungs. High pulmonary vascular resistance and low systemic vascular resistance facilitate shunting of blood in utero from the pulmonary to the systemic circulation through the widely patent DA, thereby optimizing fetal oxygen (O₂) delivery. With the transition from fetal (hypoxia) to neonatal (normoxia) oxygen conditions, the DA constricts while the PA dilates. This process often fails in prematurity, promoting congenital heart disease. Impaired O₂-responsivness in the DA promotes persistent ductus arteriosus (PDA), the most common form of congenital heart disease. Knowledge of DA oxygen sensing has greatly advanced in the past few decades, however we still lack a complete understanding of the sensing mechanism. The genomic revolution of the past two decades has facilitated unprecedented discovery in every biological system. This review will demonstrate how multiomic integration of data generated from the DA can breathe new life into our understanding of the DA's oxygen response.

Association of patent ductus arteriosus with fetal factors and endotypes of prematurity

During fetal life, the ductus arteriosus (DA) acquires the mechanisms for its postnatal closure following a thorough developmental program. This program can be interrupted by preterm birth and is also susceptible to alteration during fetal life by numerous physiological and pathological stimuli. In this review, we aim to summarize the evidence on how physiological and pathological factors affect DA development, eventually leading to patent DA (PDA). Specifically, we reviewed the associations of sex, race, and pathophysiological pathways leading to very preterm birth (endotypes) with PDA incidence and pharmacological closure. Summary of evidence suggests that there are no male-female differences in the incidence of PDA among very preterm infants. In contrast, risk of developing PDA appears to be higher in infants exposed to chorioamnionitis or who are small for gestational age. Finally, hypertensive disorders of pregnancy may be associated with a better response to pharmacological treatment of PDA. All of this evidence comes from observational studies and therefore associations do not imply causation. The current trend for many neonatologists is to wait for the natural evolution of preterm PDA. Continued research is needed to identify which fetal and perinatal factors modulate the eventual late closure of PDA in very and extremely preterm infants.

Sex Differences in Patent Ductus Arteriosus Incidence and Response to Pharmacological Treatment in Preterm Infants: A Systematic Review, Meta-Analysis and Meta-Regression

A widely accepted concept in perinatal medicine is that boys are more susceptible than girls to complications of prematurity. However, whether this ‘male disadvantage of prematurity’ also involves persistent patent ductus arteriosus (PDA) has been scarcely investigated. Our aim was to conduct a systematic review and meta-analysis on studies addressing sex differences in the risk of developing PDA among preterm infants. We also investigated whether the response to pharmacological treatment of PDA differs between boys and girls. PubMed/Medline and Embase databases were searched. The random-effects male/female risk ratio (RR) and 95% confidence interval (CI) were calculated. We included 146 studies (357,781 infants). Meta-analysis could not demonstrate sex differences in risk of developing any PDA (37 studies, RR 1.03, 95% CI 0.97 to 1.08), hemodynamically significant PDA (81 studies, RR 1.00, 95% CI 0.97 to 1.02), or in the rate of response to pharmacological treatment (45 studies, RR 1.01, 95% CI 0.98 to 1.04). Subgroup analysis and meta-regression showed that the absence of sex differences was maintained over the years and in different geographic settings. In conclusion, both the incidence of PDA in preterm infants and the response rate to pharmacological treatment of PDA are not different between preterm boys and girls.

Mouse models of patent ductus arteriosus (PDA) and their relevance for human PDA

The ductus arteriosus (DA) is a unique fetal vascular shunt, which allows blood to bypass the developing lungs in utero. After birth, changes in complex signaling pathways lead to constriction and permanent closure of the DA. The persistent patency of the DA (PDA) is a common disorder in preterm infants, yet the underlying causes of PDA are not fully defined. Although limits on the availability of human DA tissues prevent comprehensive studies on the mechanisms of DA function, mouse models have been developed that reveal critical pathways in DA regulation. Over 20 different transgenic models of PDA in mice have been described, with implications for human DA biology. Similarly, we enumerate 224 human single-gene syndromes that are associated with PDA, including a small subset that consistently feature PDA as a prominent phenotype. Comparison and functional analyses of these genes provide insight into DA development and identify key regulatory pathways that may serve as potential therapeutic targets for the management of PDA.

Personalized Genetic Diagnosis of Congenital Heart Defects in Newborns

Congenital heart disease is a group of pathologies characterized by structural malformations of the heart or great vessels. These alterations occur during the embryonic period and are the most frequently observed severe congenital malformations, the main cause of neonatal mortality due to malformation, and the second most frequent congenital malformations overall after malformations of the central nervous system. The severity of different types of congenital heart disease varies depending on the combination of associated anatomical defects. The causes of these malformations are usually considered multifactorial, but genetic variants play a key role. Currently, use of high-throughput genetic technologies allows identification of pathogenic aneuploidies, deletions/duplications of large segments, as well as rare single nucleotide variants. The high incidence of congenital heart disease as well as the associated complications makes it necessary to establish a diagnosis as early as possible to adopt the most appropriate measures in a personalized approach. In this review, we provide an exhaustive update of the genetic bases of the most frequent congenital heart diseases as well as other syndromes associated with congenital heart defects, and how genetic data can be translated to clinical practice in a personalized approach.

Transcriptome Analysis Reveals Differential Gene Expression between the Closing Ductus Arteriosus and the Patent Ductus Arteriosus in Humans

The ductus arteriosus (DA) immediately starts closing after birth. This dynamic process involves DA-specific properties, including highly differentiated smooth muscle, sparse elastic fibers, and intimal thickening (IT). Although several studies have demonstrated DA-specific gene expressions using animal tissues and human fetuses, the transcriptional profiles of the closing DA and the patent DA remain largely unknown. We performed transcriptome analysis using four human DA samples. The three closing DA samples exhibited typical DA morphology, but the patent DA exhibited aorta-like elastic lamellae and poorly formed IT. A cluster analysis revealed that samples were clearly divided into two major clusters, the closing DA and patent DA clusters, and showed distinct gene expression profiles in IT and the tunica media of the closing DA samples. Cardiac neural crest-related genes such as JAG1 were highly expressed in the tunica media and IT of the closing DA samples compared to the patent DA sample. Abundant protein expressions of jagged 1 and the differentiated smooth muscle marker calponin were observed in the closing DA samples but not in the patent DA sample. Second heart field-related genes such as ISL1 were enriched in the patent DA sample. These data indicate that the patent DA may have different cell lineages compared to the closing DA.

Next Generation Sequencing Identify Rare Copy Number Variants in Non-syndromic Patent Ductus Arteriosus

Patent ductus arteriosus (PDA) is a common congenital cardiovascular malformation with both inherited and acquired causes. Several genes have been reported to be related to PDA, but the molecular pathogenesis is still unclear. Here, we screened a population matched cohort of 39 patients with PDA and 100 healthy children using whole exome sequencing (WES). And identified 10 copy number variants (CNVs) and 20 candidate genes using Gene ontology (GO) functional enrichment analysis. In gene network analysis, we screened 7 pathogenic CNVs of 10 candidate genes (MAP3K1, MYC, VAV2, WDR5, RXRA, APLNR, TJP1, ERCC2, FOSB, CHRNA4). Further analysis of transcriptome array showed that 7 candidate genes (MAP3K1, MYC, VAV2, APLNR, TJP1, FOSB, CHRNA4) were indeed significantly expressed in human embryonic heart. Moreover, CHRNA4 was observed the most important genes. Our data provided rare CNVs as potential genetic cause of PDA in humans and also advance understanding of the genetic components of PDA.

Do Calcium and Potassium Levels Influence Ductal Patency in Preterm Infants?

OBJECTIVE

We investigated the relationship of serum potassium (K⁺) and ionized calcium (iCa²⁺) levels with the persistence of ductus arteriosus.

STUDY DESIGN

This retrospective cohort study included infants with birth weight < 1,500 g and gestational age < 32 weeks. Serum K⁺ and iCa²⁺ levels at the 1st and 48th hour of life were measured from samples. The difference between the two levels was calculated for both serum K⁺ (ΔK⁺) and iCa²⁺ (ΔCa²⁺). These values were compared between hemodynamically significant patent ductus arteriosus (hsPDA) and non-hsPDA.

RESULTS

Of 1,322 hospitalized preterm nonates, 1,196 were included in the study. Mean serum K⁺ levels at the 1st and 48th hour were higher and iCa²⁺ levels at the 1st and 48th hour were lower in hsPDA and non-hsPDA, respectively (p < 0.001). Ionized ΔCa²⁺ (-0.06 ± 0.13 vs. -0.02 ± 0.12 mmol/L) was higher in hsPDA (p < 0.001).

CONCLUSION

We demonstrated that serum K⁺ and iCa²⁺ level might play a role in ductal constriction.

Proteomics analysis of plasma protein changes in patent ductus arteriosus patients

Objective

Patent ductus arteriosus (PDA) is a congenital heart defect with an unclear etiology that occurs commonly among newborns. Adequately understanding the molecular pathogenesis of PDA can contribute to improved treatment and prevention. Plasma proteins may provide evidence to explore the molecular mechanisms of abnormal cardiac development.

Methods

Isobaric tags for relative and absolute quantitation (iTRAQ) proteomics technology was used to measure different plasma proteins in PDA patients (n = 4) and controls (n = 4). The candidate protein was validated by ELISA and Western blot (WB) assays in a larger sample. Validation of the location and expression of this protein was performed in mouse heart sections.

Results

There were three downregulated proteins and eight upregulated proteins identified in the iTRAQ proteomics data. Among these, protein disulfide-isomerase A6 (PDIA6) was further analyzed for validation. The plasma PDIA6 concentrations (3.2 ± 0.7 ng/ml) in PDA patients were significantly lower than those in normal controls (5.8 ± 1.2 ng/ml). In addition, a WB assay also supported these results. PDIA6 was widely expressed in mouse heart outflow tract on embryonic day 14.5.

Conclusion

Plasma proteomics profiles suggested novel candidate molecular markers for PDA. The findings may allow development of a new strategy to investigate the mechanism and etiology of PDA.

CYP2C9*2 is associated with indomethacin treatment failure for patent ductus arteriosus

Aims: To identify clinical andgenetic factors associated with indomethacin treatment failure in preterm neonates with patent ductus arteriosus (PDA). Patients & Methods: This is a multicenter cohort study of 144 preterm infants (22-32 weeks gestational age) at three centers who received at least one treatment course of indomethacin for PDA. Indomethacin failure was defined as requiring subsequent surgical intervention. Results: In multivariate analysis, gestational age (AOR 0.76, 95% CI 0.60-0.96), surfactant use (AOR 9.77, 95% CI 1.15-83.26), and CYP2C9*2 (AOR 3.74; 95% CI 1.34-10.44) were each associated with indomethacin failure. Conclusion: Age, surfactant use, and CYP2C9*2 influence indomethacin treatment outcome in preterm infants with PDA. This combination of clinical and genetic factors may facilitate targeted indomethacin use for PDA.

Is high platelet distribution width in the first hours of life can predict hemodynamically significant patent ductus arteriosus in preterm newborns?

Aim: To determine whether there is any association between platelet indices within the first hours of life and hemodynamically significant patent ductus arteriosus (hsPDA) in preterm newborns.Patient and methods: A total of 100 preterm infants, gestational age <32 weeks and birth weight <1500 g were analyzed in the study. Complete blood counts obtained within the first 6 hours of life were evaluated for platelet parameters and compared for patent ductus arteriosus (PDA) status.Results: We included 50 infants with hsPDA and 50 controls. Mean gestational week of patients were 28.8 ± 2.4 weeks and mean birth weight of the patients were 1237.5 ± 406 g. Platelet distribution width (PDW) is higher in PDA group compared with the control group (p = .023). The cutoff value of PDW is 11.45 fL for hsPDA with 65% sensitivity and 66% specificity. The other blood parameters including platelet count, platelet mass, and mean platelet volume (MPV) were no statistically different between the two groups. Also, there was no association with the platelet count and the response to the medical therapy.Conclusions: There is no association between hsPDA and the platelet count, platelet mass or MPV in the first day of life. We determined that hsPDA patency was significantly associated with a higher first day PDW level, which is a more specific indicator of platelet activation than other platelet parameters.

Patent ductus arteriosus in preterm infants born before 30 weeks' gestation: high rate of spontaneous closure after hospital discharge

AimThe aim of this study was to determine the spontaneous closure rate of patent ductus arteriosus at a 2-year follow-up, following failed medical therapy and beyond initial hospital discharge, and to evaluate in-hospital spontaneous or pharmacological closure rates.Materials and methodsA retrospective evaluation was conducted in a cohort of preterm infants admitted to the Neonatal ICU of Ancona between January, 2004 and June, 2013. Inclusion criteria were gestational age between 24+0 and 29+6 weeks or birth weight 1.5 mm, a left atrium-to-aorta ratio >1.4, and/or reversal of end-diastolic flow in the aorta >30% of the anterograde. First-line treatment was intravenous ibuprofen. Intravenous indomethacin was used if ibuprofen failed. Surgical ligation was considered in haemodynamically significant patent ductus arteriosus after medical treatment.

RESULTS

A total of 593 infants met the inclusion criteria, and patent ductus arteriosus was diagnosed in 317 (53.4%). Among them, 283 (89.3%) infants had haemodynamically significant patent ductus arteriosus, with pharmacological closure achieved in 228 (80.6%) infants and surgical ligation performed in 20 (7.1%). Follow-up at 24 months was available for 39 (81.3%) of 48 infants with patent ductus arteriosus at the hospital discharge: 36 (92.3%) underwent spontaneous closure, two (5.1%) underwent surgical ligation, and one (2.6%) had a patent ductus arteriosus.DiscussionA significant number of patent ductus arteriosus that fail pharmacological closure undergo spontaneous closure by the age of 2 years. This information should be taken into account when considering surgery or additional attempts of pharmacological closure.

Genetics of the patent ductus arteriosus (PDA) and pharmacogenetics of PDA treatment

Patent ductus arteriosus (PDA) is a frequent, complex, and difficult to treat clinical syndrome among preterm infants in the neonatal intensive care unit. In addition to known clinical risk factors, there are emerging data about genetic predisposition to PDA in both animal and human models. Clinical response and toxicity from drugs used to treat PDA are highly variable. Developmental and genetic aspects of pharmacokinetics and pharmacodynamics influence exposure and response to pharmacologic therapies. Given the variable efficacy and toxicity of known drug therapies, novel therapeutic targets for PDA treatment offer the promise of precision medicine. This review addresses the known genetic contributions to prolonged ductal patency, variability in response to drug therapy for PDA, and potential novel drug targets for future PDA treatment discovery.

Novel drug targets for ductus arteriosus manipulation: Looking beyond prostaglandins

Forty years ago, non-steroidal anti-inflammatory drugs were first reported to decrease systemic prostaglandin levels and promote ductus arteriosus (DA) closure. And yet, prolonged patency of the DA (PDA) remains a significant clinical problem, complicated by imperfect therapies and wide variations in treatment strategy. There are few pharmacology-based tools available for treating PDA (indomethacin, ibuprofen, and acetaminophen), or for maintaining DA patency (PGE₁) as is needed to facilitate corrective surgery for ductus-dependent congenital heart defects. Unfortunately, all of these treatments are inefficient and are associated with concerning adverse effects. This review highlights novel potential DA drug targets that may expand our therapeutic repertoire beyond the prostaglandin pathway.

Polymorphisms in CYP2C9 are associated with response to indomethacin among neonates with patent ductus arteriosus

BackgroundPatent ductus arteriosus (PDA) is a common complication seen in preterm infants. Indomethacin is routinely used to treat PDA. Evidence suggests that the response of indomethacin is highly heritable. This study investigated the association between single-nucleotide polymorphisms (SNPs) in CYP2C9 and the closure of PDA in response to indomethacin.MethodsSix SNPs in CYP2C9 were analyzed for association with indomethacin response. A case-control analysis was performed among neonates who responded to indomethacin (responders) and among those who required surgical ligation (non-responders). Independent transmission disequilibrium tests were performed among parent-child trios of responders and non-responders.ResultsThe G allele of rs2153628 was associated with increased odds of response to indomethacin in the case-control analysis (odds ratios (OR): 1.918, 95% confidence interval (CI): 1.056, 3.483). Among indomethacin responders, the G allele of rs2153628 and the T allele of rs1799853 were overtransmitted from the parents to their child (OR: 2.667, 95% CI: 1.374, 5.177 and OR: 2.375, 95% CI: 1.040, 5.425, respectively), consistent with the case-control analysis.ConclusionWe identified an association between two SNPs in CYP2C9, rs2153628 and rs1799853, and indomethacin response for the treatment of PDA. These findings suggest that response to indomethacin in the closure of PDA may be influenced by polymorphisms associated with altered indomethacin metabolism.

Using benchmarking to identify inter-centre differences in persistent ductus arteriosus treatment: can we improve outcome?

OBJECTIVE

The aim of this study was to identify inter-centre differences in persistent ductus arteriosus treatment and their related outcomes. Materials and methods We carried out a retrospective, multicentre study including infants between 24+0 and 27+6 weeks of gestation in the period between 2010 and 2011. In all centres, echocardiography was used as the standard procedure to diagnose a patent ductus arteriosus and to document ductal closure.

RESULTS

In total, 367 preterm infants were included. All four participating neonatal ICU had a comparable number of preterm infants; however, differences were observed in the incidence of treatment (33-63%), choice and dosing of medication (ibuprofen or indomethacin), number of pharmacological courses (1-4), and the need for surgical ligation after failure of pharmacological treatment (8-52%). Despite the differences in treatment, we found no difference in short-term morbidity between the centres. Adjusted mortality showed independent risk contribution of gestational age, birth weight, ductal ligation, and perinatal centre.

CONCLUSIONS

Using benchmarking as a tool identified inter-centre differences. In these four perinatal centres, the factors that explained the differences in patent ductus arteriosus treatment are quite complex. Timing, choice of medication, and dosing are probably important determinants for successful patent ductus arteriosus closure.

Is there a relationship between platelet parameters and patency of ductus arteriosus in preterm infants?

Postnatal closure of the ductus arteriosus is a complicated two-phase process involving functional and structural changes. So far, the precise mechanisms regulating this process are not fully understood. A growing body of evidence from recent studies suggests that platelets play a key role in inflammatory processes including ductal closure via interaction with endothelial cells. The aim of this study is to assess whether a relationship exists between the occurrence and/or closure of hemodynamically significant ductus arteriosus (HSDA) and platelet parameters (platelet count, circulating platelet mass, mean platelet volume, platelet distribution width) in preterm newborns. This single-center, retrospective study included 824 premature infants between 24 and 34 gestational weeks, evaluated by echocardiography at postnatal 72-96 h. Infants with and without HSDA (n = 208 vs. n = 616) were compared in terms of platelet parameters recorded within the first 3 days of life. Oral or intravenous ibuprofen was commenced for medical treatment, and echocardiography was repeated 24 h thereafter to determine ductal closure. No statistically significant difference could be demonstrated between the groups in terms of baseline platelet parameters. HSDA was independently associated with early-onset neonatal sepsis. Thrombocytopenia, low circulating platelet mass, high platelet distribution width, or high mean platelet volume could not be demonstrated as a risk factor for HSDA. None of the platelet parameters had an influence on ductal closure after medical treatment. Unlike most reports in the literature, presence of HSDA was not associated with any platelet parameter in our study. We could not demonstrate an association between any platelet parameter and either persistence or closure after medical treatment.

Identification of differentially regulated genes in human patent ductus arteriosus

In order to identify differentially expressed genes that are specific to the ductus arteriosus, 18 candidate genes were evaluated in matched ductus arteriosus and aortic samples from infants with coarctation of the aorta. The cell specificity of the gene's promoters was assessed by performing transient transfection studies in primary cells derived from several patients. Segments of ductus arteriosus and aorta were isolated from infants requiring repair for coarctation of the aorta and used for mRNA quantitation and culturing of cells. Differences in expression were determined by quantitative PCR using the ΔΔCt method. Promoter regions of six of these genes were cloned into luciferase reporter plasmids for transient transfection studies in matched human ductus arteriosus and aorta cells. Transcription factor AP-2b and phospholipase A2 were significantly up-regulated in ductus arteriosus compared to aorta in whole tissues and cultured cells, respectively. In transient transfection experiments, Angiotensin II type 1 receptor and Prostaglandin E receptor 4 promoters consistently gave higher expression in matched ductus arteriosus versus aorta cells from multiple patients. Taken together, these results demonstrate that several genes are differentially expressed in ductus arteriosus and that their promoters may be used to drive ductus arteriosus-enriched transgene expression.

Very Low Birth Weight Monochorionic Diamniotic Twins as a Risk Factor for Symptomatic Patent Ductus Arteriosus

BACKGROUND

Some prior studies have shown that symptomatic patent ductus arteriosus (sPDA) is highly familial. Although it is estimated that both genetic and environmental factors may contribute to sPDA, evidence is still lacking.

OBJECTIVE

The aim of this study was to determine the risk factors for sPDA, focusing on the genetic and in utero environment by analyzing very low birth weight (VLBW) singletons and twins.

METHODS

This retrospective case-control study reviewed the medical records of 445 VLBW infants (25 weeks ≤ gestational age <32 weeks, 600 g ≤ birth weight <1,500 g) and compared the incidence of sPDA among monochorionic diamniotic (MD) twins (n = 65), dichorionic diamniotic (DD) twins (n = 66), and singletons (n = 314).

RESULTS

Stepwise multiple regression analysis showed that twin siblings (p = 0.001), gestational week (p < 0.001), antenatal steroid use (p = 0.021), and premature rupture of membranes (p = 0.002) were independent predictors of sPDA. Incidence of sPDA in MD twin siblings was significantly higher than that in singletons (p < 0.01), whereas no significant difference was found between singletons and DD twins or between MD and DD twins.

CONCLUSIONS

The current results show that being a VLBW MD twin is an independent risk factor for sPDA, and that both genetic and in utero environmental factors may contribute to its development.

Effects of Advancing Gestation and Non-Caucasian Race on Ductus Arteriosus Gene Expression

OBJECTIVE

To identify genes affected by advancing gestation and racial/ethnic origin in human ductus arteriosus (DA).

STUDY DESIGN

We collected 3 sets of DA tissue (n = 93, n = 89, n = 91; total = 273 fetuses) from second trimester pregnancies. We examined four genes, with DNA polymorphisms that distribute along racial lines, to identify "Caucasian" and "non-Caucasian" DA. We used real time polymerase chain reaction to measure RNA expression of 48 candidate genes involved in functional closure of the DA, and used multivariable regression analyses to examine the relationships between advancing gestation, "non-Caucasian" race, and gene expression.

RESULTS

Mature gestation and non-Caucasian race are significant predictors for identifying infants who will close their patent DA when treated with indomethacin. Advancing gestation consistently altered gene expression in pathways involved with oxygen-induced constriction (eg, calcium-channels, potassium-channels, and endothelin signaling), contractile protein maturation, tissue remodeling, and prostaglandin and nitric oxide signaling in all 3 tissue sets. None of the pathways involved with oxygen-induced constriction appeared to be altered in "non-Caucasian" DA. Two genes, SLCO2A1 and NOS3, (involved with prostaglandin reuptake/metabolism and nitric oxide production, respectively) were consistently decreased in "non-Caucasian" DA.

CONCLUSIONS

Prostaglandins and nitric oxide are the most important vasodilators opposing DA closure. Indomethacin inhibits prostaglandin production, but not nitric oxide production. Because decreased SLCO2A1 and NOS3 expression can lead to increased prostaglandin and decreased nitric oxide concentrations, we speculate that prostaglandin-mediated vasodilation may play a more dominant role in maintaining the "non-Caucasian" patent DA, making it more likely to close when inhibited by indomethacin.

BMP9 and BMP10 are necessary for proper closure of the ductus arteriosus

The transition to pulmonary respiration after birth requires rapid alterations in the structure of the mammalian cardiovascular system. One dramatic change that occurs is the closure of the ductus arteriosus (DA), an arterial connection in the fetus that directs blood flow away from the pulmonary circulation. Two members of the TGFβ family, bone morphogenetic protein 9 (BMP9) and BMP10, have been recently involved in postnatal angiogenesis, both being necessary for remodeling of newly formed microvascular beds. The aim of the present work was to study whether BMP9 and BMP10 could be involved in closure of the DA. We found that Bmp9 knockout in mice led to an imperfect closure of the DA. Further, addition of a neutralizing anti-BMP10 antibody at postnatal day 1 (P1) and P3 in these pups exacerbated the remodeling defect and led to a reopening of the DA at P4. Transmission electron microscopy images and immunofluorescence stainings suggested that this effect could be due to a defect in intimal cell differentiation from endothelial to mesenchymal cells, associated with a lack of extracellular matrix deposition within the center of the DA. This result was supported by the identification of the regulation by BMP9 and BMP10 of several genes known to be involved in this process. The involvement of these BMPs was further supported by human genomic data because we could define a critical region in chromosome 2 encoding eight genes including BMP10 that correlated with the presence of a patent DA. Together, these data establish roles for BMP9 and BMP10 in DA closure.

MATR3 disruption in human and mouse associated with bicuspid aortic valve, aortic coarctation and patent ductus arteriosus

Cardiac left ventricular outflow tract (LVOT) defects represent a common but heterogeneous subset of congenital heart disease for which gene identification has been difficult. We describe a 46,XY,t(1;5)(p36.11;q31.2)dn translocation carrier with pervasive developmental delay who also exhibited LVOT defects, including bicuspid aortic valve (BAV), coarctation of the aorta (CoA) and patent ductus arteriosus (PDA). The 1p breakpoint disrupts the 5′ UTR of AHDC1, which encodes AT-hook DNA-binding motif containing-1 protein, and AHDC1-truncating mutations have recently been described in a syndrome that includes developmental delay, but not congenital heart disease [Xia, F., Bainbridge, M.N., Tan, T.Y., Wangler, M.F., Scheuerle, A.E., Zackai, E.H., Harr, M.H., Sutton, V.R., Nalam, R.L., Zhu, W. et al. (2014) De Novo truncating mutations in AHDC1 in individuals with syndromic expressive language delay, hypotonia, and sleep apnea. Am. J. Hum. Genet., 94, 784–789]. On the other hand, the 5q translocation breakpoint disrupts the 3′ UTR of MATR3, which encodes the nuclear matrix protein Matrin 3, and mouse Matr3 is strongly expressed in neural crest, developing heart and great vessels, whereas Ahdc1 is not. To further establish MATR3 3′ UTR disruption as the cause of the proband's LVOT defects, we prepared a mouse Matr3^Gt-ex13 gene trap allele that disrupted the 3′ portion of the gene. Matr3^Gt-ex13 homozygotes are early embryo lethal, but Matr3^Gt-ex13 heterozygotes exhibit incompletely penetrant BAV, CoA and PDA phenotypes similar to those in the human proband, as well as ventricular septal defect (VSD) and double-outlet right ventricle (DORV). Both the human MATR3 translocation breakpoint and the mouse Matr3^Gt-ex13 gene trap insertion disturb the polyadenylation of MATR3 transcripts and alter Matrin 3 protein expression, quantitatively or qualitatively. Thus, subtle perturbations in Matrin 3 expression appear to cause similar LVOT defects in human and mouse.

Transcription profiles of the ductus arteriosus in Brown-Norway rats with irregular elastic fiber formation

BACKGROUND

Patent ductus arteriosus (PDA) is one of the most common congenital cardiovascular defects in children. The Brown-Norway (BN) inbred rat presents a higher frequency of PDA. A previous study reported that 2 different quantitative trait loci on chromosomes 8 and 9 were significantly linked to PDA in this strain. Nevertheless, the genetic or molecular mechanisms underlying PDA phenotypes in BN rats have not been fully investigated yet.

METHODS AND RESULTS

It was found that the elastic fibers were abundant in the subendothelial area but scarce in the media even in the closed ductus arteriosus (DA) of full-term BN neonates. DNA microarray analysis identified 52 upregulated genes (fold difference >2.5) and 23 downregulated genes (fold difference <0.4) when compared with those of F344 control neonates. Among these genes, 8 (Tbx20, Scn3b, Stac, Sphkap, Trpm8, Rup2, Slc37a2, and RGD1561216) are located in chromosomes 8 and 9. Interestingly, it was also suggested that the significant decrease in the expression levels of the PGE2-specfic receptor, EP4, plays a critical role in elastogenesis in the DA.

CONCLUSIONS

BN rats exhibited dysregulation of elastogenesis in the DA. DNA microarray analysis identified the candidate genes including EP4 involved in the DNA phenotype. Further investigation of these newly identified genes will hopefully clarify the molecular mechanisms underlying the irregular formation of elastic fibers in PDA.

An unusual cause of congestive heart failure in a young woman

BACKGROUND

Congestive heart failure (CHF) is a common Emergency Department (ED) disorder that accounts for >5 million ED visits annually. Although quite rare, patent ductus arteriosus (PDA) is a serious cause of CHF that if left untreated can lead to life-threatening sequelae, such as hypertensive pulmonary vascular disease, endarteritis, and aneurysms of the ductus.

OBJECTIVE

To discuss a case of PDA leading to CHF that illustrates one of the common complications of untreated PDA.

CASE REPORT

A 35-year-old woman presented to the ED with a 2-month history of shortness of breath, dyspnea on exertion, decreased exercise tolerance, and orthopnea. The physical examination revealed a 4/6 continuous machine-like murmur. In the presence of new CHF and an atypical murmur, a transthoracic echocardiogram was performed that confirmed the diagnosis of PDA. She underwent an uncomplicated percutaneous closure of the ductus with significant improvement in her symptoms.

CONCLUSIONS

Persistent PDA in adulthood is a rare but important cause of CHF with significant morbidity and mortality if not appropriately diagnosed and treated.

Clinical pharmacology of indomethacin in preterm infants: implications in patent ductus arteriosus closure

Indomethacin is a non-steroidal anti-inflammatory drug that is a potent inhibitor of prostaglandin E(2) synthesis. After birth, the ductus arteriosus closes spontaneously within 2-4 days in term infants. The major factor closing the ductus arteriosus is the tension of oxygen, which increases significantly after birth. Prostaglandin E(2) has the opposite effect to that of oxygen; it relaxes smooth muscle and tends to inhibit the closure of the ductus arteriosus. In preterm infants with respiratory distress syndrome, the ductus arteriosus fails to close (patent ductus arteriosus [PDA]) because the concentration of prostaglandin E2 is relatively high. PDA occurs in more than 70 % of neonates weighing less than 1,500 g at birth. The aim of this article was to review the published data on the clinical pharmacology of indomethacin in preterm infants in order to provide a critical analysis of the literature and a useful tool for physicians. The bibliographic search was performed electronically using the PubMed and EMBASE databases as search engines and February 2012 was the cutoff point. A remarkable interindividual variability was observed for the half-life (t(½)), clearance (CL), and volume of distribution (V(d)) of indomethacin. Prophylactic indomethacin consists of a continuous infusion of low levels of indomethacin and may be useful in preterm infants. Extremely preterm infants are less likely to respond to indomethacin. Infants with a postnatal age of 2 months do not respond to treatment with indomethacin. Indomethacin has several adverse effects, the most common of which is renal failure. An increase in serum creatinine of ≥0.5 % mg/dL after indomethacin was observed in about 10-15 % of the patients and creatinine returns to a normal level about 1 week after cessation of therapy. Indomethacin should be administered intravenously by syringe pump for at least 30 min to minimize adverse effects on cerebral, gastrointestinal, and renal blood flow velocities. A prolonged course of indomethacin appears to reduce the risk of severe intracranial hemorrhage and renal impairment in patients with PDA. In conclusion, indomethacin is a useful drug to treat PDA.