Sonication-Assisted Method for Decellularization of Human Umbilical Artery for Small-Caliber Vascular Tissue Engineering

Decellularized vascular grafts are useful for the construction of biological small-diameter tissue-engineered vascular grafts (≤6 mm). Traditional chemical decellularization requires a long treatment time, which may damage the structure and alter the mechanical properties. Decellularization using sonication is expected to solve this problem. The aim of this study was to develop an effective decellularization method using ultrasound followed by washing. Different power values of sonication at 40 kHz were tested for 2, 4, and 8 h followed by a washing procedure. The efficacy of sonication of decellularized human umbilical artery (sDHUA) was evaluated via DNA content, histological staining, mechanical properties, and biocompatibility. The sDHUAs were further implanted into rats for up to 90 days and magnetic resonance angiography (MRA) was performed for the implanted grafts. The results demonstrated that treatment of human umbilical artery (HUA) by sonication at ultrasonic power of 204 W for 4 h followed by washing for 24 h in 2% SDS buffer could eliminate more than 90% of cells and retain similar mechanical properties of the HUA. Recellularization was assessed by scanning electron microscopy (SEM), which indicated that sDHUA provided niches for human umbilical vein endothelial cells (HUVECs) to reside, indicating in vitro cytocompatibility. Further implantation tests also indicated the fitness of the sonication-treated HUA as a scaffold for small-caliber tissue engineering vascular grafts.

VASODILATOR EFFECT OF OCTYLMETHOXYCINNAMATE ON HUMAN UMBILICAL ARTERIES

Octylmethoxycinnamate (OMC) is a filter for ultraviolet B radiation used in sunscreens to protect skin. There is some evidence about the OMC activity as endocrine disruptor concerning a possible estrogenic activity, but its vascular effects were not still analyzed. The objective was to evaluate the non-genomic effects of the OMC on human umbilical artery (HUA) without endothelium. By mean of an organ bath system, HUA rings without endothelium were contracted by 5-hydroxytryptamine (5HT; 1µM) or by depolarization with KCl (60mM), and the effect of different concentrations of OMC was analyzed. The OMC elicits vasodilator effect on HUA without endothelium contracted by 5-HT (1μM) and by KCl (60mM). The effect was similar for the two contractile agents used. Here, we established that the OMC causes vasodilation of human arteries. This effect is analogous to the non-genomic effect caused by estradiol (E2), which occurs also by and endothelial-independent mechanism.

Caffeic Acid Phenethyl Ester (CAPE), Active Phenolic Compound of Propolis Attenuates Endothelin, Prostaglandin F2α and U46619 Elicited Contractions of Isolated Human Umbilical Artery

Background: Propolis is a product of honeybees that contains a variety of different compounds, including caffeic acid phenethyl ester (CAPE). Propolis and its bioactive compounds are widely used in folk medicine and as a dietary supplement. Previously it has been shown that CAPE has antioxidant, anti-inflammatory, antimicrobial, antiviral, immunomodulatory, and anticancer activity. Objective: This in vitro study was designed to investigate the vasoactive effects of CAPE on quiescent and precontracted human umbilical arteries. Methods: Umbilical artery strips were suspended in aerated organ baths containing a buffer solution. The strips were randomly allocated to study groups (n=8). Via a transducer and computer, changes in isometric tension were recorded. The effects of cumulative CAPE (10-8-10-4M) on basal tone of the artery, and in different groups of strips, the vasodilatory effect of cumulative CAPE on the constriction elicited by endothelin (ET-1), prostaglandin F2α (PGF2α) and U46619, and the effect of incubation with NO synthase inhibitor L-NAME, were recorded. Conclusion: CAPE elicits concentration-dependent relaxation on precontracted human umbilical artery strips depending on the constrictor agent. NO plays significant role in CAPE’s vasorelaxant effect.

DNMT3A inhibits E2F1-induced arterial marker expression and impairs angiogenesis in human umbilical artery endothelial cells

Arterial marker genes EphrinB2 and HEY2 are essential for cardiovascular development and postnatal neovascularization. Our previous study confirmed that E2F1 could activate the transcription of EphrinB2 and HEY2 in human mesenchymal stem cells; however, the detailed mechanism has not been resolved yet. In this study, we focused on the interaction between E2F1 and DNMT3A, a de novo DNA methyltransferase, on regulating the expression of EphrinB2 and HEY2, and explored the potential mechanisms. Gain- and loss-of-function experiments implicated the positive effect of E2F1 on the expression of EphrinB2 and HEY2 and tube formation in human umbilical artery endothelial cells. Accumulation of DNMT3A decreased the levels of EphrinB2 and HEY2, and impaired tube formation induced by E2F1, while inhibiting DNMT3A by RNA interference augmented their expression and angiogenesis in E2F1-trasfected cells. We then asked whether the low expressions of EphrinB2 and HEY2 induced by DNMT3A are related to the methylation status of their promoters. Surprisingly, the methylation status of the CpG islands in the promoter region was not significantly affected by overexpression of exogenous DNMT3A. Furthermore, the interaction between E2F1 and DNMT3A was confirmed by co-immunoprecipitation. DNMT3A could inhibit the transcription of EphrinB2 and HEY2 promoters by affecting the binding of E2F1 to its recognition sequences as revealed by luciferase reporter assay and chromatin immunoprecipitation. These results identified a novel mechanism underlying the cooperation of DNMT3A with E2F1 on regulating target gene expression, and revealed their roles in the angiogenic process.

Clinical Importance of the Human Umbilical Artery Potassium Channels

Potassium (K+) channels are usually predominant in the membranes of vascular smooth muscle cells (SMCs). These channels play an important role in regulating the membrane potential and vessel contractility—a role that depends on the vascular bed. Thus, the activity of K+ channels represents one of the main mechanisms regulating the vascular tone in physiological and pathophysiological conditions. Briefly, the activation of K+ channels in SMC leads to hyperpolarization and vasorelaxation, while its inhibition induces depolarization and consequent vascular contraction. Currently, there are four different types of K+ channels described in SMCs: voltage-dependent K+ (KV) channels, calcium-activated K+ (KCa) channels, inward rectifier K+ (Kir) channels, and 2-pore domain K+ (K2P) channels. Due to the fundamental role of K+ channels in excitable cells, these channels are promising therapeutic targets in clinical practice. Therefore, this review discusses the basic properties of the various types of K+ channels, including structure, cellular mechanisms that regulate their activity, and new advances in the development of activators and blockers of these channels. The vascular functions of these channels will be discussed with a focus on vascular SMCs of the human umbilical artery. Then, the clinical importance of K+ channels in the treatment and prevention of cardiovascular diseases during pregnancy, such as gestational hypertension and preeclampsia, will be explored.