Role of Extracellular Matrix in Pathophysiology of Patent Ductus Arteriosus: Emphasis on Vascular Remodeling

Lung ultrasound score in the decision of patent ductus arteriosus closure in neonates

PURPOSE

We aimed to investigate the role of lung ultrasound (LUS) score in the closure of hemodynamically insignificant patent ductus arteriosus (PDA) and the clinical findings of the patients before and after closure.

METHODS

The study groups (107 preterm neonates under 34 gestational weeks) were classified as hemodynamically significant PDA (group 1), hemodynamically insignificant PDA with closure therapy (group 2), hemodynamically insignificant PDA without closure therapy (group 3), and no PDA group (group 4) based on the echocardiography. 6- and 10-region LUS scores were compared for each group.

RESULTS

There was a significant difference between groups 1 and 3 on first, third, and seventh days. In contrast, groups 1 and 2 had similar LUS scores on the first, third, and seventh days. There was a negative correlation between LUS scores on the first and third days and gestational age, birth weight, the first- and fifth-minute APGAR scores, and there was a positive correlation between aortic root to left atrium ratio, and PDA diameter/weight ratio.

CONCLUSION

We observed that LUS scores in patients with hemodynamically insignificant PDA treated with closure therapy were similar to in patients with hemodynamically significant PDA. Thus, LUS score can have role in PDA closure in preterm neonates. However, more comprehensive studies are needed.

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.

Clinical and morphological features of arterial duct in premature newborns

The open arterial duct has a pathological significance in premature newborns. Closure of the ductus arteriosus is a complex process that includes functional and anatomical closure.

Purpose. To identify the features of arterial duct remodeling in premature newborns.

Material and methods. We conducted a retrospective clinical and morphological analysis of 35 deceased premature newborns. During their lifetime, all children were examined using clinical and laboratory-instrumental methods. In all cases, autopsies of deceased children were performed with a complex of morphological studies of the arterial duct.

Results. It has been established that the open arterial duct in premature newborns plays an important role in increasing respiratory failure. It also necessitates the appointment and conduct of invasive respiratory therapy. The functioning of the arterial duct is facilitated by low partial pressure and blood oxygen saturation levels. Morphofunctional features of arterial duct remodeling were revealed. A positive correlation was established between the indicators of the gas composition of the child’s blood and the thickness of the duct wall.

Conclusion. Risk factors for an open arterial duct in premature newborns are the age of the mother over 35 years, threatened miscarriage, prenatal discharge of amniotic fluid, gestational diabetes mellitus, fetoplacental insufficiency, and severe asphyxia at birth. Morphological changes in the form of thickening of the endothelial layer and the formation of intimal pillows, fragmentation and focal necrosis of the internal elastic membrane with the accumulation of mucoid matter, proliferation and migration of smooth muscle cells into the subendothelial space reflect the processes of remodeling of the arterial duct. 

Piezo1 in vascular remodeling of atherosclerosis and pulmonary arterial hypertension: A potential therapeutic target

Vascular remodeling (VR) is a structural and functional change of blood vessels to adapt to the changes of internal and external environment. It is one of the common pathological features of many vascular proliferative diseases. The process of VR is mainly manifested in the changes of vascular wall structure and function, including intimal hyperplasia, thickening or thinning of media, fibrosis of adventitia, etc. These changes are also the pathological basis of aging and various cardiovascular diseases. Mechanical force is the basis of cardiovascular biomechanics, and the newly discovered mechanical sensitive ion channel Piezo1 is widely distributed in the whole cardiovascular system. Studies have confirmed that Piezo1, a mechanically sensitive ion channel, plays an important role in cardiovascular remodeling diseases. This article reviews the molecular mechanism of Piezo1 in atherosclerosis, hypertension and pulmonary hypertension, in order to provide a theoretical basis for the further study of vascular remodeling.

Cinaciguat Prevents Postnatal Closure of Ductus Arteriosus by Vasodilation and Anti-remodeling in Neonatal Rats

Closure of the ductus arteriosus (DA) involves vasoconstriction and vascular remodeling. Cinaciguat, a soluble guanylyl cyclase (sGC) activator, was reported with vasodilatory and anti-remodeling effects on pulmonary hypertensive vessels. However, its effects on DA are not understood. Therefore, we investigated whether cinaciguat regulated DA patency and examined its underlying mechanisms. In vivo, we found that cinaciguat (10 mg/kg, i.p. at birth) prevented DA closure at 2 h after birth with luminal patency and attenuated intimal thickening. These anti-remodeling effects were associated with enhanced expression of cyclic guanosine monophosphate (cGMP) in DA. Ex vivo, cinaciguat dilated oxygen-induced DA constriction dose-dependently. Such vasodilatory effect was blunted by KT-5823, a PKG inhibitor. In DA smooth muscle cells (DASMCs), we further showed that cinaciguat inhibited angiotensin II (Ang II)-induced proliferation and migration of DASMCs. In addition, cinaciguat inhibited Ang II-induced mitochondrial reactive oxygen species (ROS) production. Finally, Ang II-activated MAPKs and Akt were also inhibited by cinaciguat. In conclusion, cinaciguat prevents postnatal DA closure by vasodilation and anti-remodeling through the cGMP/PKG pathway. The mechanisms underlying anti-remodeling effects include anti-proliferation and anti-migration, with attenuation of mitochondrial ROS production, MAPKs, and Akt signaling. Thus, this study implicates that sGC activation may be a promising novel strategy to regulate DA patency.

Molecular Mechanisms Underlying Remodeling of Ductus Arteriosus: Looking beyond the Prostaglandin Pathway

The ductus arteriosus (DA) is a physiologic vessel crucial for fetal circulation. As a major regulating factor, the prostaglandin pathway has long been the target for DA patency maintenance or closure. However, the adverse effect of prostaglandins and their inhibitors has been a major unsolved clinical problem. Furthermore, a significant portion of patients with patent DA fail to respond to cyclooxygenase inhibitors that target the prostaglandin pathway. These unresponsive medical patients ultimately require surgical intervention and highlight the importance of exploring pathways independent from this well-recognized prostaglandin pathway. The clinical limitations of prostaglandin-targeting therapeutics prompted us to investigate molecules beyond the prostaglandin pathway. Thus, this article introduces molecules independent from the prostaglandin pathway based on their correlating mechanisms contributing to vascular remodeling. These molecules may serve as potential targets for future DA patency clinical management.