Valve Development Research Articles

Angiopoietin-like 2 is essential to aortic valve development in mice

Aortic valve (AoV) abnormalities during embryogenesis are a major risk for the development of aortic valve stenosis (AVS) and cardiac events later in life. Here, we identify an unexpected role for Angiopoietin-like 2 (ANGPTL2), a pro-inflammatory protein secreted by senescent cells, in valvulogenesis. At late embryonic stage, mice knocked-down for Angptl2 (Angptl2-KD) exhibit a premature thickening of AoV leaflets associated with a dysregulation of the fine balance between cell apoptosis, senescence and proliferation during AoV remodeling and a decrease in the crucial Notch signalling. These structural and molecular abnormalities lead toward spontaneous AVS with elevated trans-aortic gradient in adult mice of both sexes. Consistently, ANGPTL2 expression is detected in human fetal semilunar valves and associated with pathways involved in cell cycle and senescence. Altogether, these findings suggest that Angptl2 is essential for valvulogenesis, and identify Angptl2-KD mice as an animal model to study spontaneous AVS, a disease with unmet medical need.

Perspectives on pediatric congenital aortic valve stenosis: Extracellular matrix proteins, post translational modifications, and proteomic strategies.

In heart valve biology, organization of the extracellular matrix structure is directly correlated to valve function. This is especially true in cases of pediatric congenital aortic valve stenosis (pCAVS), in which extracellular matrix (ECM) dysregulation is a hallmark of the disease, eventually leading to left ventricular hypertrophy and heart failure. Therapeutic strategies are limited, especially in pediatric cases in which mechanical and tissue engineered valve replacements may not be a suitable option. By identifying mechanisms of translational and post-translational dysregulation of ECM in CAVS, potential drug targets can be identified, and better bioengineered solutions can be developed. In this review, we summarize current knowledge regarding ECM proteins and their post translational modifications (PTMs) during aortic valve development and disease and contributing factors to ECM dysregulation in CAVS. Additionally, we aim to draw parallels between other fibrotic disease and contributions to ECM post-translational modifications. Finally, we explore the current treatment options in pediatrics and identify how the field of proteomics has advanced in recent years, highlighting novel characterization methods of ECM and PTMs that may be used to identify potential therapeutic strategies relevant to pCAVS.

Abstract 14459: Case Report: Unusual Presentation of Cardiobacterium Hominis Bioprosthetic Valve Endocarditis

Introduction: Cardiobacterium hominis , part of the oropharyngeal flora, is a gram-negative bacteria reported to cause infection in less than 5% of patients with infective endocarditis (IE). In children, congenital heart disease (CHD) is a predominant risk factor for developing IE. Herein we describe an unusual presentation of C. hominis bioprosthetic valve endocarditis. Case Presentation: A 23-year-old woman with bicuspid aortic valve and aortic valve stenosis underwent aortic bioprosthetic valve placement in 2017. In March 2022, she presented to an emergency room with left lower abdominal pain. A CT scan demonstrated occlusion of the left iliac artery. Medications at that time included oral contraceptive pills and baby aspirin. No echocardiogram was obtained at that visit. She presented for a routine cardiology follow-up in May 2022 at which time she was asymptomatic. Transthoracic echocardiogram demonstrated moderate to severe aortic insufficiency, though the mechanism could not be delineated. There was concomitant development of mild mitral valve and tricuspid valve insufficiency. She denied dyspnea, chest pain, or fevers. Laboratory investigation showed mild elevation of CRP and a normal ESR. A transesophageal echocardiogram demonstrated that the severe aortic regurgitation was through a paravalvar leak (figure 1). There was no evidence of vegetations. Three separate blood cultures grew C. hominis . The patient was admitted for IV antibiotic therapy prior to bioprosthetic replacement. Conclusions: C. hominis is an infrequent cause of endocarditis and most cases present with fever and elevated ESR. This patient had an unusual presentation with left iliac thrombus, which in retrospect was likely due to embolism of a vegetation. She also developed aortic bioprosthetic paravalvar leak. This case highlights the need for a high degree of suspicion for endocarditis in patients with CHD and bioprosthetic valves.

Abstract 9555: Human Valve Atlas in Health and Disease

Background: Semilunar and atrioventricular valves have distinct structures and are often affected differently in congenital valve diseases (CVD). Here we aim to define and compare the cellular composition and transcriptomic signatures of four different human fetal valves, which provide a reference map to engineer valves in vitro , and to study valve-specific impairment in CVD. Methods: Aortic, pulmonary, mitral, and tricuspid valves were barcoded respectively from a healthy human fetal heart at gestational day 105. Single-cell (sc)RNA-seq was performed. Spatial localization of new subpopulations was determined by immunostaining and in situ hybridization. Cell-cell interaction was revealed by cell-chat. Results: scRNA-seq analysis revealed major cell types including endothelial (VECs), interstitial (VICs), and immune cells. In addition to reported collagen & glycosaminoglycan (GAG) VIC in mice, VIC sub-clustering identified two human-specific APOE+ and CLDN11+ subpopulations. APOE+ VICs specifically located underneath VECs facing unidirectional flow, indicating cell-cell interaction of APOE+ VICs & VECs. VEC sub-clustering identified lymphatic VECs under turbulent flow, while CD55+ & PTGDS+ VECs under unidirectional flow. Cell-chat uncovered NOTCH3-JAG1 pairs in facilitating the co-development of spatially adjacent APOE+ VICs & PTGDS+ VECs. To further uncover valve-specific signatures, we compared gene expression profiles of four valves. In lymphatic VECs, genes regulating BMP pathway were enriched in semilunar valves. In GAG VICs, MAPK pathway was specifically enriched in pulmonary valve, indicating development of different valves may need activation of different pathways. Interestingly, when comparing valve with pulmonary atresia versus healthy pulmonary valve using scRNA-seq, both MAPK related genes and GAG VICs were significantly reduced, suggesting impaired MAPK may contribute to pulmonary-specific loss of GAG VICs leading to its abnormal development. Conclusion: Our high-resolution atlas of human fetal valves revealed subtypes of VIC & VEC with unique spatial locations. Comparison of four valves identified pulmonary valve-specific MAPK pathway that may explain loss of GAG VICs in patients with pulmonary atresia.

A lightweight flexible semi-cylindrical valve for seamless integration in soft robots based on the giant electrorheological fluid

Complete compliance of soft robots is a trending research topic. One significant aspect is the control element. In the current work, a flexible electro-rheological (ER) valve development is chosen due to the advantage of its dynamic power density, convenient electronic control mode, and no mechanical moving parts. These properties enable the ER valve to be miniaturized and easily integrated into a fluid-driven soft robot. However, the integration effect of the existing flexible ER valve configuration in soft robots is not ideal. In this study, a novel concentric semi-cylindrical flexible giant ER (GER) valve with a dual flowing direction is proposed for a soft robot to enable a larger deformation bending motion with multiple motion modes. The resulting valve has an overall volume of 50 mm3, a mass of 0.88 g, and a maximum controlling pressure of 84 kPa with a pressure change rate of 13.9, which is suitable for most soft robot applications. The pressure difference calculation method for the concentric semi-cylindrical GER valve is discussed. The effects of size, voltages, and flow rates on the valve’s static and dynamic performances, as well as the characteristics of the two pressure regulation modes, are investigated through simulations and experiments. The seamless integration and flexibility of the proposed valve are demonstrated by controlling a typical network actuator with six motion modes. Finally, a soft robot composed of two actuators is fabricated and realized the grasping of multiple everyday objects using different motion modes.

Transcatheter Pulmonary Valve Replacement: A Review of Current Valve Technologies.

Transcatheter pulmonary valve replacement was first performed by Dr Philip Bonhoeffer, who implanted a Medtronic Melody valve in a human in 2000. Over the past 2 decades, there have been many advances in transcatheter pulmonary valve technology. This includes the use of the SAPIEN transcatheter heart valve in the pulmonary position, modifications and refinements to valve implantation procedures, and development of self-expanding valves and prestents to treat large diameter native or patched right ventricular outflow tracts. This article reviews the current transcatheter pulmonary valve technologies with a focus on valve design, screening process, implant procedure, and clinical outcomes.

Synthesis of High-Molecular-Weight and Strength Polyisobutylene-Based Polyurethane and Its Use for the Development of a Synthetic Heart Valve.

Under optimized synthesis conditions, for the first time, polyisobutylene-based polyurethane (PIB-PU) is prepared with 70% PIB soft segment (i.e., a bioinert and calcification-resistant PU) with Mn > 100000 Da, 32 MPa ultimate strength, and 630% elongation. The key parameters for this achievement are a) the precise stoichiometry of the polyurethane forming reaction, specifically the use of highly purified di-isocyanate (4,4'-methylene-bis (phenyl isocyanate), MDI), and b) the increased solid content of the synthesis solution to the limit beyond which increased viscosity prevents stirring. The shape of the stress-strain trace of PIB-PU indicates a two-step failure starting with a reversible elastic (Hookean) region up to ≈50% yield, followed by a slower linearly increasing high-modulus-deformation region suggesting the strengthening of PIB soft segments by entanglement/catenation, and the hard segments by progressively ordering urethane domains. This PIB-PU is a candidate for a fully synthetic bioprosthetic heart valve since preliminary studies show that PIB-PU has impressive fatigue life.

Loss of ceramide synthase 5 reduces the development of aortic valve stenosis in mice with high fat diet

Abstract Background Ceramide synthase 5 (CerS5) is essential to maintain C:16 ceramide levels in mice. Ceramides contribute to inflammation and calcification, two hallmarks of aortic valve stenosis development. It is known, that loss of CerS5 function reduces diet-induced obesity. Purpose The aim of this study was to investigate the effect of ceramide synthase 5 and high-fat diet on the development of aortic valve stenosis with a mouse model. Methods Our experiment consists of four groups of mice: Wild type (WT) and CerS5 (−/−) mice, with normal and high fat diet. We induced the aortic valve stenosis development through a wire-injury. For this model, a coronary angiography wire is introduced into the left ventricle over the right carotid artery, followed by rotation on the aortic valve level to generate a defined injury. Development of aortic valve stenosis was determined by measuring the peak velocity 14, 28 and 42 days after the wire-injury. With histological analysis of the aortic valve, we measured macrophage infiltration with CD68 immunostaining and calcification using von Kossa staining. For statistical analysis ANOVA and Turkeys multiple comparisons were performed. Results Histological analysis of the aortic valve revealed, that in CerS5 (−/−) mice with high fat diet (HFD) immune cell infiltration is reduced, while there is no difference between CerS5 (−/−) mice and wild type, when fed with normal diet (A). Also calcification showed a trend towards a reduction in CerS5 mice with high fat diet, but was not statistically significant (B). Echocardiography could detect a reduced peak velocity of CerS5 mice with high fat diet, in comparison to the other groups, four and six weeks after wire injury (C). Conclusion Our experiments indicate that loss of CerS5 function reduces the development of aortic valve stenosis in mice with high fat diet, by decreasing immune cell infiltration and calcification. Interestingly, in the groups with normal chow, loss of CerS5 function had no effect. In addition, high-fat diet alone had no negative effect in our mouse model. Based on our results it can be assumed that upon high fat diet CerS5 mediates for pro-inflammatory effects in the aortic valve, which are absent on normal diet. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): Ernst & Berta Grimmke Foundation (13/19)

MITRAL VALVE CHORDAE TENDINEAE DEVELOP INDEPENDENTLY FROM LEAFLET TISSUE DURING FETAL DEVELOPMENT

During fetal development of the mitral valve, chordae tendineae are thought to derive from the leaflet after it’s delamination from the ventricular wall. However, preliminary work on the fetal bovine heart has shown the presence of branched chordae tendineae well before leaflet delamination (Fig. 1A). We hypothesized that the fetal chordae and leaflet tissue are developing along distinct timelines in the bovine heart. To test this hypothesis, we examined the anatomical development and extracellular matrix composition of the bovine mitral valve chordae and leaflet during fetal development and in adult.

SYMMETRIC LEAFLET EXPANSION WITH MILD PROGRESSIVE LEAFLET TETHERING IS A NORMAL DEVELOPMENTAL FEATURE OF TRICUSPID VALVE MATURATION DURING YOUTH: A QUANTITATIVE THREE-DIMENSIONAL ECHOCARDIOGRAPHY (3DE) STUDY

SYMMETRIC LEAFLET EXPANSION WITH MILD PROGRESSIVE LEAFLET TETHERING IS A NORMAL DEVELOPMENTAL FEATURE OF TRICUSPID VALVE MATURATION DURING YOUTH: A QUANTITATIVE THREE-DIMENSIONAL ECHOCARDIOGRAPHY (3DE) STUDY

Structural abnormalities in the non-dilated ascending aortic wall of bicuspid aortic valve patients

BackgroundA bicuspid aortic valve (BAV) is the most common congenital cardiac malformation. The development of the aortic valve is closely related to the development of the ascending aorta, associated with structural differences in the bicuspid aorta. Here we describe the non-dilated ascending aortic wall in bicuspid aortic valve patients. MethodsBAV (n=41) and tricuspid aortic valve (TAV) (n=18) non-dilated ascending aortic wall samples were studied. We investigated the following features of the aortic wall: vessel wall thickness, endothelial cell morphology, atherosclerosis, and elastic lamellae organization. Medial pathologic features encompassing elastic fiber thinning, fragmentation and degeneration, overall medial degeneration, mucoid extracellular matrix accumulation, and smooth muscle cell nuclei loss were studied. Furthermore, we included apoptosis, periaortic inflammation, and the level of expression of differentiated vascular smooth muscle cells. ResultsThe non-dilated BAV ascending aortic wall is characterized by a significantly thinner intimal layer, without features of atherosclerosis (P<.001). The medial layer is significantly thicker (P<.001) with more mucoid extracellular matrix accumulation (P<.001). All other medial pathologic features were more prominent in the TAV (P<.001). The media has significantly less differentiated vascular smooth muscle cells (P<.001) between the neatly regulated elastic lamellae which are thinner in the BAV as compared to the TAV (P<.0001). ConclusionsThe BAV ascending aorta without dilatation is characterized by a differentiation defect of vascular smooth muscle cells in the media and a significantly thinner intimal layer without overt pathologic features.

Role of endothelial CXCR4 in the development of aortic valve stenosis

BackgroundCXCL12/CXCR4 signaling is essential in cardiac development and repair, however, its contribution to aortic valve stenosis (AVS) remains unclear. In this study, we tested the role of endothelial CXCR4 on the development of AVS.Materials and methodsWe generated CXCR4 endothelial cell-specific knockout mice (EC CXCR4 KO) by crossing CXCR4fl/fl mice with Tie2-Cre mice to study the role of endothelial cell CXCR4 in AVS. CXCR4fl/fl mice were used as controls. Echocardiography was used to assess the aortic valve and cardiac function. Heart samples containing the aortic valve were stained using Alizarin Red for detection of calcification. Masson’s trichrome staining was used for the detection of fibrosis. The apex of the heart samples was stained with wheat germ agglutinin (WGA) to visualize ventricular hypertrophy.ResultsCompared with the control group, the deletion of CXCR4 in endothelial cells led to significantly increased aortic valve peak velocity and aortic valve peak pressure gradient, with decreased aortic valve area and ejection fraction. EC CXCR4 KO mice also developed cardiac hypertrophy as evidenced by increased diastolic and systolic left ventricle posterior wall thickness (LVPW), cardiac myocyte size, and heart weight (HW) to body weight (BW) ratio. Our data also confirmed increased microcalcifications, interstitial fibrosis, and thickened valvular leaflets of the EC CXCR4 KO mice.ConclusionThe data collected throughout this study suggest the deletion of CXCR4 in endothelial cells is linked to the development of aortic valve stenosis and left ventricular hypertrophy. The statistically significant parameters measured indicate that endothelial cell CXCR4 plays an important role in aortic valve development and function. We have compiled compelling evidence that EC CXCR4 KO mice can be used as a novel model for AVS.

Differential requirement for DICER1 activity during the development of mitral and tricuspid valves.

Mitral and tricuspid valves are essential for unidirectional blood flow in the heart. They are derived from similar cell sources, and yet congenital dysplasia affecting both valves is clinically rare, suggesting the presence of differential regulatory mechanisms underlying their development. Here, we specifically inactivated Dicer1 in the endocardium during cardiogenesis and found that Dicer1 deletion caused congenital mitral valve stenosis and regurgitation, whereas it had no impact on other valves. We showed that hyperplastic mitral valves were caused by abnormal condensation and extracellular matrix (ECM) remodeling. Our single-cell RNA sequencing analysis revealed impaired maturation of mesenchymal cells and abnormal expression of ECM genes in mutant mitral valves. Furthermore, expression of a set of miRNAs that target ECM genes was significantly lower in tricuspid valves compared to mitral valves, consistent with the idea that the miRNAs are differentially required for mitral and tricuspid valve development. We thus reveal miRNA-mediated gene regulation as a novel molecular mechanism that differentially regulates mitral and tricuspid valve development, thereby enhancing our understanding of the non-association of inborn mitral and tricuspid dysplasia observed clinically.

Activation of AcvR1-Mediated Signaling Results in Semilunar Valve Defects.

Calcific aortic valve disease (CAVD) is a common cardiac defect, particularly in the aging population. While several risk factors, such as bi-leaflet valve structure and old age, have been identified in CAVD pathogenesis, molecular mechanisms resulting in this condition are still under active investigation. Bone morphogenetic protein signaling via the activin type I receptor (AcvRI) plays an important role during physiological and pathological processes involving calcification, e.g., bone formation and heterotopic ossification. In addition, AcvRI is required for normal cardiac valve development, yet its role in aortic valve disease, if any, is currently unknown. Here, we induced the expression of constitutively active AcvRI in developing mouse embryos in the endocardium and in cells at the valve leaflet–wall junction that are not of endocardium origin using the Nfac1Cre transgene. The mutant mice were born alive, but showed thickened aortic and pulmonary valve leaflets during the early postnatal period. Adult mutant mice developed aortic stenosis with high frequency, sclerotic aortic valves, and displayed Alcian Blue-positive hypertrophic chondrocyte-like cells at the leaflet–wall junction. Calcification was only seen with low penetrance. In addition, we observed that the expression levels of gene sets associated with inflammation-related cytokine signaling, smooth muscle cell contraction, and cGMP signaling were altered in the mutants when compared with those of the controls. This work shows that, in a mouse model, such continuous AcvRI activity in the Nfatc1Cre recombination domain results in pathological changes in the aortic valve structure and function.

Normal and abnormal development of the aortic valve and ascending aortic wall: an overview of the embryology and pathology of the bicuspid aortic valve.

Normal and abnormal development of the aortic valve and ascending aortic wall: an overview of the embryology and pathology of the bicuspid aortic valve.

En Face Endocardial Cushion Preparation for Planar Morphogenesis Analysis in Mouse Embryos.

The study of the cellular and molecular mechanisms underlying the development of the mammalian heart is essential to address human congenital heart disease. The development of the primitive cardiac valves involves the epithelial-to-mesenchymal transition (EMT) of endocardial cells from the atrioventricular canal (AVC) and outflow tract (OFT) regions of the heart in response to local inductive myocardial and endocardial signals. Once the cells delaminate and invade the extracellular matrix (cardiac jelly) located between the endocardium and the myocardium, the primitive endocardial cushions (EC) are formed. This process implies that the endocardium has to fill the gaps left by the delaminated cells and has to reorganize itself to converge (narrow) or extend (lengthen) along an axis. Current research has implicated the planar cell polarity (PCP) pathway in regulating the subcellular localization of the factors involved in this process. Classically, the initial phases of cardiac valve development have been studied in cross-sections of embryonic hearts or in ex vivo AVC or OFT explants cultured on collagen gels. These approaches allow the analysis of apico-basal polarity but do not allow the analysis of cell behavior within the plane of the epithelium or of the morphological changes of migrating cells. Here, we show an experimental approach that allows the visualization of the endocardium at valvulogenic regions as a planar field of cells. This experimental approach provides the opportunity to study PCP, planar topology, and intercellular communication within the endocardium of the OFT and AVC during valve development. Deciphering new cellular mechanisms involved in cardiac valve morphogenesis may contribute to understanding congenital heart disease associated with endocardial cushion defects.

Normal and abnormal development of the aortic valve and ascending aortic wall: a comprehensive overview of the embryology and pathology of the bicuspid aortic valve.

A bicuspid aortic valve (BAV) is the most prevalent congenital cardiac anomaly, in which the valve has only two leaflets, instead of the normal three. Patients with a BAV have an increased risk of aneurysm formation and the development of an aortic dissection. Vascular smooth muscle cells in both the non- and dilated aortic wall are characterized by a maturation defect in all BAV patients, as compared to patients with a tricuspid aortic valve, which can contribute to inherent developmental susceptibility. Besides structural abnormalities of the vascular wall, a turbulent blood flow, caused by bicuspid valve geometry, could expedite the pathological process in the aortic wall, leading to aortopathy. Although the risk for aortopathy is significant, not all BAV patients experience (acute) aortic complications in their lifespan, highlighting the complexity of the pathogenetic process. Recent studies have focused on the embryonic development of semilunar valves and the ascending aortic wall. Their findings highlight that a defect in the embryogenesis could not only explain the development of a malformed aortic valve but also the increased risk for ascending aorta and arch pathology. This review presents an overview of the normal and abnormal development of the aortic valve and the aortic wall: a common defect in early embryogenesis causes the development of a BAV and associated aortopathy.

Comparative study on Sichuan yak pericardium and Australian cattle pericardium

Currently, as the key raw material of artificial biological heart valve, bovine pericardium is mainly depend on import and has become a "bottleneck" challenge, greatly limiting the development of domestic biological heart valve. Therefore, the localization of bovine pericardium is extremely urgent. In this study, the pericardium of Sichuan yak was compared with that of Australian cattle in terms of fundamental properties and anti-calcification performance. The results demonstrated that the appearance and thickness of yak pericardium were more advantageous than the Australian one. Sichuan yak pericardium and Australian cattle pericardium had comparable performance in shrinkage temperature, mechanical test and anti-calcification test. This study preliminarily verifies the feasibility of substitution of Australian cattle pericardium by Sichuan yak pericardium and promotes the progression of bovine pericardium localization with data support.

Valve in valve and valve in ring transcatheter aortic valveimplantation

In recent years the trend towards surgical bioprosthetic valve implantation, especially among young patients, has increased in order to avoid anticoagulant therapy. The patient&amp;rsquo;s age remains one of the leading risk factors for valve dysfunction. Gold standard for treating such diseases was surgical reintervention until the development of transcatheter heart valves. By 2050 the annual number of patients undergoing surgical bioprosthetic valve implantation is expected to triple from an average of 290,000 in 2003 to over 850,000. This study presents the literature review of Valve in Valve and Valve in Ring procedures, as well as our experience in ViV and ViR transcatheter valve implantation.

Valvuloplasty of fetal pulmonary atresia with intact ventricular septum and hypoplastic right heart: Mid-term follow-up results

ObjectiveThis study aimed to analyze and evaluate the results of mid-term follow-up after fetal pulmonary valvuloplasty (FPV) in fetuses with pulmonary atresia with intact ventricular septum (PA/IVS). MethodsFrom August 31, 2018, to May 31, 2019, seven fetuses with PA/IVS and hypoplastic right heart were included in this study. All underwent echocardiography by the same specialist and were operated on by the same team. Intervention and echocardiography data were collected, and changes in the associated indices noted during follow-up were analyzed. ResultsAll seven fetuses successfully underwent FPV. The median gestational age at FPV was 27.54 weeks. The average FPV procedural time was 6 ​min. Persistent bradycardia requiring treatment occurred in 4/7 procedures. Finally, five pregnancies were successfully delivered, and the other two were aborted. Compared to data before fetal cardiac interventions (FCI), tricuspid valve annulus diameter/mitral valve annulus diameter (TV/MV) and right ventricle diameter/left ventricle diameter (RV/LV) of all fetuses had progressively improved. The maximum tricuspid regurgitation velocity decreased from 4.60 ​m/s to 3.64 ​m/s. The average follow-up time was 30.40 ​± ​2.05 months. During the follow-up period, the diameter of the tricuspid valve ring in five children continued to improve, and the development rate of the tricuspid valve was relatively obvious from 6 months to 1 year after birth. However, the development of the right ventricle after birth was relatively slow. It was discovered that there were individual variations in the development of the right ventricle during follow-up. ConclusionThe findings support the potential for the development of the right ventricle and tricuspid valve in fetuses with PA/IVS who underwent FCI. Development of the right ventricle and tricuspid valve does not occur synchronously during pregnancy. The right ventricle develops rapidly in utero, but the development of tricuspid valve is more apparent after birth than in utero.