Transcriptional profiling reveals ductus arteriosus-specific genes that regulate vascular tone

Discovery and Characterization of VU0542270, the First Selective Inhibitor of Vascular Kir6.1/SUR2B KATP Channels

Vascular smooth muscle KATP channels critically regulate blood flow and blood pressure by modulating vascular tone and therefore represent attractive drug targets for treating several cardiovascular disorders. However, the lack of potent inhibitors that can selectively inhibit Kir6.1/SUR2B (vascular KATP) over Kir6.2/SUR1 (pancreatic KATP) has eluded discovery despite decades of intensive research. We therefore screened 47,872 chemically diverse compounds for novel inhibitors of heterologously expressed Kir6.1/SUR2B channels. The most potent inhibitor identified in the screen was an N-aryl-N'-benzyl urea compound termed VU0542270. VU0542270 inhibits Kir6.1/SUR2B with an IC50 of approximately 100 nM but has no apparent activity toward Kir6.2/SUR1 or several other members of the Kir channel family at doses up to 30 µM (>300-fold selectivity). By expressing different combinations of Kir6.1 or Kir6.2 with SUR1, SUR2A, or SUR2B, the VU0542270 binding site was localized to SUR2. Initial structure-activity relationship exploration around VU0542270 revealed basic texture related to structural elements that are required for Kir6.1/SUR2B inhibition. Analysis of the pharmacokinetic properties of VU0542270 showed that it has a short in vivo half-life due to extensive metabolism. In pressure myography experiments on isolated mouse ductus arteriosus vessels, VU0542270 induced ductus arteriosus constriction in a dose-dependent manner similar to that of the nonspecific KATP channel inhibitor glibenclamide. The discovery of VU0542270 provides conceptual proof that SUR2-specific KATP channel inhibitors can be developed using a molecular target-based approach and offers hope for developing cardiovascular therapeutics targeting Kir6.1/SUR2B. SIGNIFICANCE STATEMENT: Small-molecule inhibitors of vascular smooth muscle KATP channels might represent novel therapeutics for patent ductus arteriosus, migraine headache, and sepsis; however, the lack of selective channel inhibitors has slowed progress in these therapeutic areas. Here, this study describes the discovery and characterization of the first vascular-specific KATP channel inhibitor, VU0542270.

A novel role for PGE2-EP4 in the developmental programming of the mouse ductus arteriosus: consequences for vessel maturation and function

The ductus arteriosus (DA) is a vascular shunt that allows oxygenated blood to bypass the developing lungs in utero. Fetal DA patency requires vasodilatory signaling via the prostaglandin E2 (PGE2) receptor EP4. However, in humans and mice, disrupted PGE2-EP4 signaling in utero causes unexpected patency of the DA (PDA) after birth, suggesting another role for EP4 during development. We used EP4-knockout (KO) mice and acute versus chronic pharmacological approaches to investigate EP4 signaling in DA development and function. Expression analyses identified EP4 as the primary EP receptor in the DA from midgestation to term; inhibitor studies verified EP4 as the primary dilator during this period. Chronic antagonism recapitulated the EP4 KO phenotype and revealed a narrow developmental window when EP4 stimulation is required for postnatal DA closure. Myography studies indicate that despite reduced contractile properties, the EP4 KO DA maintains an intact oxygen response. In newborns, hyperoxia constricted the EP4 KO DA but survival was not improved, and permanent remodeling was disrupted. Vasomotion and increased nitric oxide (NO) sensitivity in the EP4 KO DA suggest incomplete DA development. Analysis of DA maturity markers confirmed a partially immature EP4 KO DA phenotype. Together, our data suggest that EP4 signaling in late gestation plays a key developmental role in establishing a functional term DA. When disrupted in EP4 KO mice, the postnatal DA exhibits signaling and contractile properties characteristic of an immature DA, including impairments in the first, muscular phase of DA closure, in addition to known abnormalities in the second permanent remodeling phase.NEW & NOTEWORTHY EP4 is the primary EP receptor in the ductus arteriosus (DA) and is critical during late gestation for its development and eventual closure. The "paradoxical" patent DA (PDA) phenotype of EP4-knockout mice arises from a combination of impaired contractile potential, altered signaling properties, and a failure to remodel associated with an underdeveloped immature vessel. These findings provide new mechanistic insights into women who receive NSAIDs to treat preterm labor, whose infants have unexplained PDA.

Sexual dimorphic gene expression profile of perirenal adipose tissue in ovine fetuses with growth restriction

Worldwide, fetal growth restriction (FGR) affects 7%-10% of pregnancies, or roughly 20.5 million infants, each year. FGR increases not only neonatal mortality and morbidity but also the risk of obesity in later life. Currently, the molecular mechanisms by which FGR "programs" an obese phenotype are not well understood. Studies demonstrate that FGR females are more prone to obesity compared to males; however, the molecular mechanisms that lead to the sexually dimorphic programming of FGR are not known. Thus, we hypothesized that FGR leads to the sexually dimorphic programming of preadipocytes and reduces their ability to differentiate into mature adipocytes. To test the hypothesis, we utilized a maternal hyperthermia-induced placental insufficiency to restrict fetal growth in sheep. We collected perirenal adipose tissue from near-term (∼140 days gestation) male and female FGR and normal-weight fetal lambs (N = 4 to 5 in each group), examined the preadipocytes' differentiation potential, and identified differential mRNA transcript expression in perirenal adipose tissue. Male FGR fetuses have a lower cellular density (nuclei number/unit area) compared to control male fetuses. However, no difference was observed in female FGR fetuses compared to control female fetuses. In addition, the ability of preadipocytes to differentiate into mature adipocytes with fat accumulation was impaired in male FGR fetuses, but this was not observed in female FGR fetuses. Finally, we examined the genes and pathways involved in the sexually dimorphic programming of obesity by FGR. On enrichment of differentially expressed genes in males compared to females, the Thermogenesis KEGG Pathway was downregulated, and the Metabolic and Steroid Biosynthesis KEGG pathways were upregulated. On enrichment of differentially expressed genes in male FGR compared to male control, the Steroid Biosynthesis KEGG Pathway was downregulated, and the PPAR Signaling KEGG pathway was upregulated. No pathways were altered in females in response to growth restriction in perirenal adipose tissue. Thus, the present study demonstrates a sexually dimorphic program in response to growth restriction in sheep fetal perirenal adipose tissue.

Prdm6 drives ductus arteriosus closure by promoting ductus arteriosus smooth muscle cell identity and contractility

Based upon our demonstration that the smooth muscle cell-selective (SMC-selective) putative methyltransferase, Prdm6, interacts with myocardin-related transcription factor-A, we examined Prdm6's role in SMCs in vivo using cell type-specific knockout mouse models. Although SMC-specific depletion of Prdm6 in adult mice was well tolerated, Prdm6 depletion in Wnt1-expressing cells during development resulted in perinatal lethality and a completely penetrant patent ductus arteriosus (DA) phenotype. Lineage tracing experiments in Wnt1Cre2 Prdm6fl/fl ROSA26LacZ mice revealed normal neural crest-derived SMC investment of the outflow tract. In contrast, myography measurements on DA segments isolated from E18.5 embryos indicated that Prdm6 depletion significantly reduced DA tone and contractility. RNA-Seq analyses on DA and ascending aorta samples at E18.5 identified a DA-enriched gene program that included many SMC-selective contractile associated proteins that was downregulated by Prdm6 depletion. Chromatin immunoprecipitation-sequencing experiments in outflow tract SMCs demonstrated that 50% of the genes Prdm6 depletion altered contained Prdm6 binding sites. Finally, using several genome-wide data sets, we identified an SMC-selective enhancer within the Prdm6 third intron that exhibited allele-specific activity, providing evidence that rs17149944 may be the causal SNP for a cardiovascular disease GWAS locus identified within the human PRDM6 gene.

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.

α-Subunit Tyrosine Phosphorylation Is Required for Activation of the Large Conductance Ca2+-Activated Potassium Channel in the Rabbit Sphincter of Oddi

Large conductance Ca²⁺-activated potassium (BK_Ca) channels are regulated by intracellular free Ca²⁺ concentrations ([Ca²⁺]i) and channel protein phosphorylation. In hypercholesterolemia (HC), motility impairment of the sphincter of Oddi (SO) is associated with abnormal [Ca²⁺]i accumulation in smooth muscle cells of the rabbit SO (RSOSMCs), which is closely related to BK_Ca channel activity. However, the underlying mechanisms regulating channel activity remain unclear. In this study, an HC rabbit model was generated and used to investigate BK_Ca channel activity of RSOSMCs via SO muscle tone measurement in vitro and manometry in vivo, electrophysiological recording, intracellular calcium measurement, and Western blot analyses. BK_Ca channel activity was decreased, which correlated with [Ca²⁺]i overload and reduced tyrosine phosphorylation of the BK_Ca α-subunit in the HC group. The abnormal [Ca²⁺]i accumulation and decreased BK_Ca channel activity were partially restored by Na₃VO₄ pretreatment but worsened by genistein in RSOSMCs in the HC group. This study suggests that α-subunit tyrosine phosphorylation is required for [Ca²⁺]i to activate BK_Ca channels, and there is a negative feedback between the BK_Ca channel and the L-type voltage-dependent Ca²⁺ channel that regulates [Ca²⁺]i. This study provides direct evidence that tyrosine phosphorylation of BK_Ca α-subunits is required for [Ca²⁺]i to activate BK_Ca channels in RSOSMCs, which may be the underlying physiological and pathologic mechanism regulating the activity of BK_Ca channels in SO cells.

Patent Ductus Arteriosus: A Contemporary Perspective for the Pediatric and Adult Cardiac Care Provider

The burden of patent ductus arteriosus (PDA) continues to be significant. In view of marked differences in preterm infants versus more mature, term counterparts (viewed on a continuum with adolescent and adult patients), mechanisms regulating ductal patency, genetic contributions, clinical consequences, and diagnostic and treatment thresholds are discussed separately, when appropriate. Among both preterm infants and older children and adults, a range of hemodynamic profiles highlighting the markedly variable consequences of the PDA are provided. In most contemporary settings, transcatheter closure is preferable over surgical ligation, but data on longer-term outcomes, particularly among preterm infants, are lacking. The present review provides recommendations to identify gaps in PDA diagnosis, management, and treatment on which subsequent research can be developed. Ultimately, the combination of refined diagnostic thresholds and expanded treatment options provides the best opportunities to address the burden of PDA. Although fundamental gaps remain unanswered, the present review provides pediatric and adult cardiac care providers with a contemporary framework in PDA care to support the practice of evidence-based medicine.

Transcriptional Evaluation of the Ductus Arteriosus at the Single-Cell Level Uncovers a Requirement for Vim (Vimentin) for Complete Closure

OBJECTIVE

Failure to close the ductus arteriosus, patent ductus arteriosus, accounts for 10% of all congenital heart defects. Despite significant advances in patent ductus arteriosus management, including pharmacological treatment targeting the prostaglandin pathway, a proportion of patients fail to respond and must undergo surgical intervention. Thus, further refinement of the cellular and molecular mechanisms that govern vascular remodeling of this vessel is required.

METHODS

We performed single-cell RNA-sequencing of the ductus arteriosus in mouse embryos at E18.5 (embryonic day 18.5), and P0.5 (postnatal day 0.5), and P5 to identify transcriptional alterations that might be associated with remodeling. We further confirmed our findings using transgenic mouse models coupled with immunohistochemistry analysis.

RESULTS

The intermediate filament vimentin emerged as a candidate that might contribute to closure of the ductus arteriosus. Indeed, mice with genetic deletion of vimentin fail to complete vascular remodeling of the ductus arteriosus. To seek mechanisms, we turned to the RNA-sequencing data that indicated changes in Jagged1 with similar profile to vimentin and pointed to potential links with Notch. In fact, Notch3 signaling was impaired in vimentin null mice and vimentin null mice phenocopies patent ductus arteriosus in Jagged1 endothelial and smooth muscle deleted mice.

CONCLUSIONS

Through single-cell RNA-sequencing and by tracking closure of the ductus arteriosus in mice, we uncovered the unexpected contribution of vimentin in driving complete closure of the ductus arteriosus through a mechanism that includes deregulation of the Notch signaling pathway.

The molecular mechanisms of oxygen-sensing in human ductus arteriosus smooth muscle cells: A comprehensive transcriptome profile reveals a central role for mitochondria

The ductus arteriosus (DA) connects the fetal pulmonary artery and aorta, diverting placentally oxygenated blood from the developing lungs to the systemic circulation. The DA constricts in response to increases in oxygen (O2) with the first breaths, resulting in functional DA closure, with anatomic closure occurring within the first days of life. Failure of DA closure results in persistent patent ductus arteriosus (PDA), a common complication of extreme preterm birth. The DA's response to O2, though modulated by the endothelium, is intrinsic to the DA smooth muscle cells (DASMC). DA constriction is mediated by mitochondrial-derived reactive oxygen species, which increase in proportion to arterial partial pressure of oxygen (PaO2). The resulting redox changes inhibit voltage-gated potassium channels (Kv) leading to cell depolarization, calcium influx and DASMC constriction. To date, there has not been an unbiased assessment of the human DA O2-sensors using transcriptomics, nor are there known molecular mechanisms which characterize DA closure. DASMCs were isolated from DAs obtained from 10 term infants at the time of congenital heart surgery. Cells were purified by flow cytometry, negatively sorting using CD90 and CD31 to eliminate fibroblasts or endothelial cells, respectively. The purity of the DASMC population was confirmed by positive staining for α-smooth muscle actin, smoothelin B and caldesmon. Cells were grown for 96 h in hypoxia (2.5% O2) or normoxia (19% O2) and confocal imaging with Cal-520 was used to determine oxygen responsiveness. An oxygen-induced increase in intracellular calcium of 18.1% ± 4.4% and SMC constriction (-27% ± 1.5% shortening) occurred in all cell lines within five minutes. RNA sequencing of the cells grown in hypoxia and normoxia revealed significant regulation of 1344 genes (corrected p < 0.05). We examined these genes using Gene Ontology (GO). This unbiased assessment of altered gene expression indicated significant enrichment of the following GOterms: mitochondria, cellular respiration and transcription. The top regulated biologic process was generation of precursor metabolites and energy. The top regulated cellular component was mitochondrial matrix. The top regulated molecular function was transcription coactivator activity. Multiple members of the NADH-ubiquinone oxidoreductase (NDUF) family are upregulated in human DASMC (hDASMC) following normoxia. Several of our differentially regulated transcripts are encoded by genes that have been associated with genetic syndromes that have an increased incidence of PDA (Crebb binding protein and Histone Acetyltransferase P300). This first examination of the effects of O2 on human DA transcriptomics supports a putative role for mitochondria as oxygen sensors.

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.

Plasma Amino Acid Concentrations at Birth and Patent Ductus Arteriosus in Very and Extremely Preterm Infants

Background: Amino acids are increasingly recognized as bioactive molecules in numerous physiological and pathophysiological pathways. The non-essential amino acid glutamate is vasoactive in the rat ductus arteriosus (DA) and a decrease in its levels within the 1st days of life has been associated with the presence of patent DA (PDA) in extremely preterm infants. However, these findings have not been confirmed in other studies. Objective: To investigate the possible association between amino acid concentrations in the 1st day of life and the presence of PDA in a cohort of 121 newborns with gestational age (GA) below 30 weeks and birth weight (BW) below 1,500 g. Methods: Plasma samples were collected 6-12 h after birth and amino acid concentrations were determined by tandem mass spectrometry. Besides PDA, we analyzed the potential association of amino acid concentrations with infant sex, small for GA (SGA, defined as BW < third percentile), antenatal corticosteroids, chorioamnionitis, and preeclampsia. Group differences were analyzed by ANOVA adjusted for GA and BW. A Bonferroni significance threshold of P < 0.0024 was used to correct for multiple testing. Results: PDA was found in 48 of the 121 infants examined. We observed higher mean levels of glutamate in infants with PDA (147.0 μmol/L, SD 84.0) as compared with those without (106.7 μmol/L, SD 49.1, P = 0.0006). None of the other amino acid concentrations in the PDA group reached the level of statistical significance that was pre-set to correct for multiple comparisons. Glutamate levels were not significantly affected by infant sex, being SGA, or by exposure to antenatal corticosteroids, clinical chorioamnionitis, or preeclampsia. Conclusion: Our study not only does not confirm the previous findings of low glutamate levels in preterm infants with PDA, but we have even found elevated glutamate concentrations associated with PDA. Nevertheless, despite the high statistical significance, the difference in glutamate levels may lack clinical significance or may be an epiphenomenon associated with the particular clinical condition of infants with PDA.

Molecular and Mechanical Mechanisms Regulating Ductus Arteriosus Closure in Preterm Infants

Failure of ductus arteriosus closure after preterm birth is associated with significant morbidities. Ductal closure requires and is regulated by a complex interplay of molecular and mechanical mechanisms with underlying genetic factors. In utero patency of the ductus is maintained by low oxygen tension, high levels of prostaglandins, nitric oxide and carbon monoxide. After birth, ductal closure occurs first by functional closure, followed by anatomical remodeling. High oxygen tension and decreased prostaglandin levels mediated by numerous factors including potassium channels, endothelin-1, isoprostanes lead to the contraction of the ductus. Bradykinin and corticosteroids also induce ductal constriction by attenuating the sensitivity of the ductus to PGE2. Smooth muscle cells of the ductus can sense oxygen through a mitochondrial network by the role of Rho-kinase pathway which ends up with increased intracellular calcium levels and contraction of myosin light chains. Anatomical closure of the ductus is also complex with various mechanisms such as migration and proliferation of smooth muscle cells, extracellular matrix production, endothelial cell proliferation which mediate cushion formation with the interaction of blood cells. Regulation of vessel walls is affected by retinoic acid, TGF-β1, notch signaling, hyaluronan, fibronectin, chondroitin sulfate, elastin, and vascular endothelial cell growth factor (VEGF). Formation of the platelet plug facilitates luminal remodeling by the obstruction of the constricted ductal lumen. Vasa vasorum are more pronounced in the term ductus but are less active in the preterm ductus. More than 100 genes are effective in the prostaglandin pathway or in vascular smooth muscle development and structure may affect the patency of ductus. Hemodynamic changes after birth including fluid load and flow characteristics as well as shear forces within the ductus also stimulate closure. Current pharmacological treatment for the closure of a patent ductus is based on the blockage of the prostaglandin pathway mainly through COX or POX inhibition, albeit with some limitations and side effects. Further research for new agents aiming ductal closure should focus on a clear understanding of vascular biology of the ductus.

Role of dopamine and selective dopamine receptor agonists on mouse ductus arteriosus tone and responsiveness

BACKGROUND

Indomethacin treatment for patent ductus arteriosus (PDA) is associated with acute kidney injury (AKI). Fenoldopam, a dopamine (DA) DA₁-like receptor agonist dilates the renal vasculature and may preserve renal function during indomethacin treatment. However, limited information exists on DA receptor-mediated signaling in the ductus and fenoldopam may prevent ductus closure given its vasodilatory nature.

METHODS

DA receptor expression in CD-1 mouse vessels was analyzed by qPCR and immunohistochemistry. Concentration-response curves were established using pressure myography. Pretreatment with SCH23390 (DA₁-like receptor antagonist), phentolamine (α -adrenergic receptor antagonist) or indomethacin addressed mechanisms for DA-induced changes. Fenoldopam's effects on postnatal ductus closure were evaluated in vivo.

RESULTS

DA₁ receptors were expressed equally in ductus and aorta. High-dose DA induced modest vasoconstriction under newborn O₂ conditions. Phentolamine inhibited DA-induced constriction, while SCH23390 augmented constriction, consistent with a vasodilatory role for DA₁ receptors. Despite this, fenoldopam had little effect on ductus tone nor indomethacin- or O₂-induced constriction and did not impair postnatal closure in vivo.

CONCLUSION(S)

DA receptors are present in the ductus but have limited physiologic effects. DA-induced ductus vasoconstriction is mediated via α-adrenergic pathways. The absence of DA₁-mediated impairment of ductus closure supports the study of potential role for fenoldopam during PDA treatment.

Structure-Activity Relationships, Pharmacokinetics, and Pharmacodynamics of the Kir6.2/SUR1-Specific Channel Opener VU0071063

Glucose-stimulated insulin secretion from pancreatic β-cells is controlled by ATP-regulated potassium (K_ATP) channels composed of Kir6.2 and sulfonylurea receptor 1 (SUR1) subunits. The K_ATP channel-opener diazoxide is FDA-approved for treating hyperinsulinism and hypoglycemia but suffers from off-target effects on vascular K_ATP channels and other ion channels. The development of more specific openers would provide critically needed tool compounds for probing the therapeutic potential of Kir6.2/SUR1 activation. Here, we characterize a novel scaffold activator of Kir6.2/SUR1 that our group recently discovered in a high-throughput screen. Optimization efforts with medicinal chemistry identified key structural elements that are essential for VU0071063-dependent opening of Kir6.2/SUR1. VU0071063 has no effects on heterologously expressed Kir6.1/SUR2B channels or ductus arteriole tone, indicating it does not open vascular K_ATP channels. VU0071063 induces hyperpolarization of β-cell membrane potential and inhibits insulin secretion more potently than diazoxide. VU0071063 exhibits metabolic and pharmacokinetic properties that are favorable for an in vivo probe and is brain penetrant. Administration of VU0071063 inhibits glucose-stimulated insulin secretion and glucose-lowering in mice. Taken together, these studies indicate that VU0071063 is a more potent and specific opener of Kir6.2/SUR1 than diazoxide and should be useful as an in vitro and in vivo tool compound for investigating the therapeutic potential of Kir6.2/SUR1 expressed in the pancreas and brain.

Transcriptional profiles in the chicken ductus arteriosus during hatching

The ductus arteriosus, an essential embryonic blood vessel between the pulmonary artery and the descending aorta, constricts after birth or hatching and eventually closes to terminate embryonic circulation. Chicken embryos have two long ductus arteriosi, which anatomically differ from mammal ductus arteriosus. Each long ductus arteriosus is divided into two parts: the pulmonary artery-sided and descending aorta-sided ductus arteriosi. Although the pulmonary artery-sided and descending aorta-sided ductus arteriosi have distinct functional characteristics, such as oxygen responsiveness, the difference in their transcriptional profiles has not been investigated. We performed a DNA microarray analysis (GSE 120116 at NCBI GEO) with pooled tissues from the chicken pulmonary artery-sided ductus arteriosus, descending aorta-sided ductus arteriosus, and aorta at the internal pipping stage. Although several known ductus arteriosus-dominant genes such as tfap2b were highly expressed in the pulmonary artery-sided ductus arteriosus, we newly found genes that were dominantly expressed in the chicken pulmonary artery-sided ductus arteriosus. Interestingly, cluster analysis showed that the expression pattern of the pulmonary artery-sided ductus arteriosus was closer to that of the descending aorta-sided ductus arteriosus than that of the aorta, whereas the morphology of the descending aorta-sided ductus arteriosus was closer to that of the aorta than that of the pulmonary artery-sided ductus arteriosus. Subsequent pathway analysis with DAVID bioinformatics resources revealed that the pulmonary artery-sided ductus arteriosus showed enhanced expression of the genes involved in melanogenesis and tyrosine metabolism compared with the descending aorta-sided ductus arteriosus, suggesting that tyrosinase and the related genes play an important role in the proper differentiation of neural crest-derived cells during vascular remodeling in the ductus arteriosus. In conclusion, the transcription profiles of the chicken ductus arteriosus provide new insights for investigating the mechanism of ductus arteriosus closure.

Molecular and mechanical factors contributing to ductus arteriosus patency and closure

Regulation of the ductus arteriosus, an essential fetal vessel connecting the pulmonary artery and aorta, is complex. Failure of this vessel to close after birth may result in a persistent left-to-right shunt through the patent ductus arteriosus, a condition associated with significant morbidities. Numerous factors contribute to the shift from fetal ductus patency to postnatal closure, requiring precise coordination of molecular cues with biomechanical forces and underlying genetic influences. Despite significant advances, questions remain regarding signaling dynamics and the natural time course of ductus closure, particularly in preterm neonates. This review highlights the contributions of early investigators and more recent clinician scientists to our understanding of the molecular and mechanical factors that mediate ductus patency and closure.

Comparative gene array analyses of severe elastic fiber defects in late embryonic and newborn mouse aorta

Elastic fibers provide reversible elasticity to the large arteries and are assembled during development when hemodynamic forces are increasing. Mutations in elastic fiber genes are associated with cardiovascular disease. Mice lacking expression of the elastic fiber genes elastin ( Eln-/-), fibulin-4 ( Efemp2-/-), or lysyl oxidase ( Lox-/-) die at birth with severe cardiovascular malformations. All three genetic knockout models have elastic fiber defects, aortic wall thickening, and arterial tortuosity. However, Eln-/- mice develop arterial stenoses, while Efemp2-/- and Lox-/- mice develop ascending aortic aneurysms. We performed comparative gene array analyses of these three genetic models for two vascular locations and developmental stages to determine differentially expressed genes and pathways that may explain the common and divergent phenotypes. We first examined arterial morphology and wall structure in newborn mice to confirm that the lack of elastin, fibulin-4, or lysyl oxidase expression provided the expected phenotypes. We then compared gene expression levels for each genetic model by three-way ANOVA for genotype, vascular location, and developmental stage. We found three genes upregulated by genotype in all three models, Col8a1, Igfbp2, and Thbs1, indicative of a common response to severe elastic fiber defects in developing mouse aorta. Genes that are differentially regulated by vascular location or developmental stage in all three models suggest mechanisms for location or stage-specific disease pathology. Comparison of signaling pathways enriched in all three models shows upregulation of integrins and matrix proteins involved in early wound healing, but not of mature matrix molecules such as elastic fiber proteins or fibrillar collagens.

Effects of antenatal betamethasone on preterm human and mouse ductus arteriosus: comparison with baboon data

BACKGROUND

Although studies involving preterm infants ≤34 weeks gestation report a decreased incidence of patent ductus arteriosus after antenatal betamethasone, studies involving younger gestation infants report conflicting results.

METHODS

We used preterm baboons, mice, and humans (≤27^6/7 weeks gestation) to examine betamethasone's effects on ductus gene expression and constriction both in vitro and in vivo.

RESULTS

In mice, betamethasone increased the sensitivity of the premature ductus to the contractile effects of oxygen without altering the effects of other contractile or vasodilatory stimuli. Betamethasone's effects on oxygen sensitivity could be eliminated by inhibiting endogenous prostaglandin/nitric oxide signaling. In mice and baboons, betamethasone increased the expression of several developmentally regulated genes that mediate oxygen-induced constriction (K⁺ channels) and inhibit vasodilator signaling (phosphodiesterases). In human infants, betamethasone increased the rate of ductus constriction at all gestational ages. However, in infants born ≤25^6/7 weeks gestation, betamethasone's contractile effects were only apparent when prostaglandin signaling was inhibited, whereas at 26-27 weeks gestation, betamethasone's contractile effects were apparent even in the absence of prostaglandin inhibitors.

CONCLUSIONS

We speculate that betamethasone's contractile effects may be mediated through genes that are developmentally regulated. This could explain why betamethasone's effects vary according to the infant's developmental age at birth.

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.

Transcriptional profiling of the ductus arteriosus: Comparison of rodent microarrays and human RNA sequencing

DA closure is crucial for the transition from fetal to neonatal life. This closure is supported by changes to the DA's signaling and structural properties that distinguish it from neighboring vessels. Examining transcriptional differences between these vessels is key to identifying genes or pathways responsible for DA closure. Several microarray studies have explored the DA transcriptome in animal models but varied experimental designs have led to conflicting results. Thorough transcriptomic analysis of the human DA has yet to be performed. A clear picture of the DA transcriptome is key to guiding future research endeavors, both to allow more targeted treatments in the clinical setting, and to understand the basic biology of DA function. In this review, we use a cross-species cross-platform analysis to consider all available published rodent microarray data and novel human RNAseq data in order to provide high priority candidate genes for consideration in future DA studies.

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.

Microarray gene expression analysis in ovine ductus arteriosus during fetal development and birth transition

BACKGROUND

Patent ductus arteriosus (PDA) in the newborn is the most common congenital heart anomaly and is significantly more common in preterm infants. Contemporary pharmacological treatment is effective in only 70-80% of the cases. Moreover, indomethacin or ibuprofen, which are used to close a PDA may be accompanied by serious side effects in premature infants. To explore the novel molecular pathways, which may be involved in the maturation and closure of the ductus arteriosus (DA), we used fetal and neonatal sheep to test the hypothesis that maturational development of DA is associated with significant alterations in specific mRNA expression.

METHODS

We conducted oligonucleotide microarray experiments on the isolated mRNA from DA and ascending aorta from three study groups (premature fetus-97 ± 0 d, near-term fetus-136 ± 0.8 d, and newborn lamb-12 ± 0 h). We compared the alterations in mRNA expression in DA and aorta to identify genes specifically involved in DA maturation.

RESULTS

Results demonstrate significant changes in wingless-integrin1, thrombospondin 1, receptor activator of nuclear factor-kappa B, nitric oxide synthase, and retinoic acid receptor activation signaling pathways.

CONCLUSION

We conclude that these pathways may play an important role during both development and postnatal DA closure and warrant further investigation.

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.

Selective serotonin reuptake inhibitor exposure constricts the mouse ductus arteriosus in utero

Use of selective serotonin reuptake inhibitors (SSRIs) is common during pregnancy. Fetal exposure to SSRIs is associated with persistent pulmonary hypertension of the newborn (PPHN); however, a direct link between the two has yet to be established. Conversely, it is well known that PPHN can be caused by premature constriction of the ductus arteriosus (DA), a fetal vessel connecting the pulmonary and systemic circulations. We hypothesized that SSRIs could induce in utero DA constriction. Using isolated vessels and whole-animal models, we sought to determine the effects of two commonly prescribed SSRIs, fluoxetine and sertraline, on the fetal mouse DA. Cannulated vessel myography studies demonstrated that SSRIs caused concentration-dependent DA constriction and made vessels less sensitive to prostaglandin-induced dilation. Moreover, in vivo studies showed that SSRI-exposed mice had inappropriate DA constriction in utero. Taken together, these findings establish that SSRIs promote fetal DA constriction and provide a potential mechanism by which SSRIs could contribute to PPHN.

Heterogeneity in vascular smooth muscle cell embryonic origin in relation to adult structure, physiology, and disease

Regional differences in vascular physiology and disease response exist throughout the vascular tree. While these differences in physiology and disease correspond to regional vascular environmental conditions, there is also compelling evidence that the embryonic origins of the smooth muscle inherent to the vessels may play a role. Here, we review what is known regarding the role of embryonic origin of vascular smooth muscle cells during vascular development. The focus of this review is to highlight the heterogeneity in the origins of vascular smooth muscle cells and the resulting regional physiologies of the vessels. Our goal is to stimulate future investigation into this area and provide a better understanding of vascular organogenesis and disease. .

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.

Aminoglycoside-mediated relaxation of the ductus arteriosus in sepsis-associated PDA

Sepsis is strongly associated with patency of the ductus arteriosus (PDA) in critically ill newborns. Inflammation and the aminoglycoside antibiotics used to treat neonatal sepsis cause smooth muscle relaxation, but their contribution to PDA is unknown. We examined whether: 1) lipopolysaccharide (LPS) or inflammatory cytokines cause relaxation of the ex vivo mouse DA; 2) the aminoglycosides gentamicin, tobramycin, or amikacin causes DA relaxation; and 3) newborn infants treated with aminoglycosides have an increased risk of symptomatic PDA (sPDA). Changes in fetal mouse DA tone were measured by pressure myography in response to LPS, TNF-α, IFN-γ, macrophage-inflammatory protein 2, IL-15, IL-13, CXC chemokine ligand 12, or three aminoglycosides. A clinical database of inborn patients of all gestations was analyzed for association between sPDA and aminoglycoside treatment. Contrary to expectation, neither LPS nor any of the inflammatory mediators caused DA relaxation. However, each of the aminoglycosides caused concentration-dependent vasodilation in term and preterm mouse DAs. Pretreatment with indomethacin and N-(G)-nitro-L-arginine methyl ester did not prevent gentamicin-induced DA relaxation. Gentamicin-exposed DAs developed less oxygen-induced constriction than unexposed DAs. Among 488,349 infants who met the study criteria, 40,472 (8.3%) had sPDA. Confounder-adjusted odds of sPDA were higher in gentamicin-exposed infants, <25 wk and >32 wk. Together, these findings suggest that factors other than inflammation contribute to PDA. Aminoglycoside-induced vasorelaxation and inhibition of oxygen-induced DA constriction support the paradox that antibiotic treatment of sepsis may contribute to DA relaxation. This association was also found in newborn infants, suggesting that antibiotic selection may be an important consideration in efforts to reduce sepsis-associated PDA.