Emerging imaging and circulating biomarkers in relation to underlying mechanisms in Bicuspid Aortic Valve aortopathy

Bicuspid Aortic Valve (BAV) is the most prevalent congenital heart defect with an autosomal dominant inheritance. With up to 2% of the general population affected by the condition, mortality remains high likely due to the development of aortopathy which pre-disposes to the development of aortic dissection. Current guidelines focus on surgical management, once a threshold of aorta diameter is surpassed, via routine image surveillance. However, it is recognised that some will develop aortic dissection without meeting these requirements for surgical intervention. Recent literature has begun to address the need for potential biomarkers specific to aortopathy in the BAV population to aid in risk stratification. Four-dimensional cardiovascular magnetic resonance flow imaging has paved the way to the development of imaging measurements such as wall shear stress and reverse flow which aid in the assessment of aberrant blood flow contributing to aortopathy in the BAV group. Differing levels of plasma biomarkers such as matrix metalloproteinases and microRNA have also been associated with aortopathy development furthering insight into the cellular mechanisms involved in aortic vascular matrix remodelling. This article will provide an overview of the recent research into prospective 4-D imaging and circulating biomarkers that have been studied and potential areas of future work.

A systematic review of miRNAs as biomarkers for chemotherapy-induced cardiotoxicity in breast cancer patients reveals potentially clinically informative panels as well as key challenges in miRNA research

Breast cancer patients are at a particularly high risk of cardiotoxicity from chemotherapy having a detrimental effect on quality-of-life parameters and increasing the risk of mortality. Prognostic biomarkers would allow the management of therapies to mitigate the risks of cardiotoxicity in vulnerable patients and a key potential candidate for such biomarkers are microRNAs (miRNA). miRNAs are post-transcriptional regulators of gene expression which can also be released into the circulatory system and have been associated with the progression of many chronic diseases including many types of cancer. In this review, the evidence for the potential application of miRNAs as biomarkers for chemotherapy-induced cardiotoxicity (CIC) in breast cancer patientsis evaluated and a simple meta-analysis is performed to confirm the replication status of each reported miRNA. Further selection of miRNAs is performed by reviewing the reported associations of each miRNA with other cardiovascular conditions. Based on this research, the most representative panels targeting specific chemotherapy agents and treatment regimens are suggested, that contain several informative miRNAs, including both general markers of cardiac damage as well as those for the specific cancer treatments.

The genetic, molecular, and hemodynamic basis of bicuspid aortic valve aortopathy: A contemporary narrative review

Bicuspid aortic valve (BAV) is the most common congenital heart defect. Along with the expeditious advancements in genetics, molecular science, and imaging, the body of literature surrounding BAV has grown immensely in recent years. The purpose of this review is to categorize and summarize articles published regarding bicuspid aortic valve aortopathy in the last five years. The increased availability of genomic testing has allowed the study of inherited factors contributing to BAV, with associations between variations in several genes and the development of aortopathy. It has also been found that epigenetics and microRNAs play a critical role. Molecularly, the arrangement of the extracellular matrix and its various components are related to the strength of the aortic wall. Compromises in the extracellular matrix have been shown to limit the ability of the smooth muscle cells and fibroblasts to maintain the integrity of the aortic wall. Advancements in cardiac imaging, notably magnetic resonance imaging, have allowed for intense study of the hemodynamics of various cardiac lesions. Recent articles have proposed that early aortic valve insufficiency rather than stenosis leads to aortic dilation. After reviewing recent publications regarding BAV and the development of aortopathy, the authors acknowledge that there is much still unknown. Further research in the fields addressed in this review will allow for improvements in diagnostics and treatments for affected individuals.

MicroRNAs as Biomarkers for Birth Defects

It is estimated that 2-4% of live births will have a birth defect (BD). The availability of biomarkers for the prenatal detection of BDs will facilitate early risk assessment, prompt medical intervention and ameliorating disease severity. miRNA expression levels are often found to be altered in many diseases. There is, thus, a growing interest in determining whether miRNAs, particularly extracellular miRNAs, can predict, diagnose, or monitor BDs. These miRNAs, typically encapsulated in exosomes, are released by cells (including those of the fetus and placenta) into the extracellular milieu, such as blood, urine, saliva and cerebrospinal fluid, thereby enabling interaction with target cells. Exosomal miRNAs are stable, protected from degradation, and retain functionality. The observation that placental and fetal miRNAs can be detected in maternal serum, provides a strong rationale for adopting miRNAs as noninvasive prenatal biomarkers for BDs. In this mini-review, we examine the current state of research involving the use of miRNAs as prognostic and diagnostic biomarkers for BD.

MicroRNAs involve in bicuspid aortic aneurysm: pathogenesis and biomarkers

The incidence of bicuspid aortic valves (BAV) is high in the whole population, BAV-related thoracic aortic aneurysm (TAA) is accompanied by many adverse vascular events. So far, there are two key points in dealing with BAV-related TAA. First is fully understanding on its pathogenesis. Second is optimizing surgical intervention time. This review aims to illustrate the potential role of miRNAs in both aspects, that is, how miRNAs are involved in the occurrence and progression of BAV-related TAA, and the feasibilities of miRNAs as biomarkers.

An Exploratory Look at Bicuspid Aortic Valve (Bav) Aortopathy: Focus on Molecular and Cellular Mechanisms

Bicuspid aortic valve (BAV) is the most common congenital heart malformation. BAV patients are at increased risk for aortic valve disease (stenosis/regurgitation), infective endocarditis, thrombi formation and, in particular, aortic dilatation, aneurysm and dissection. This review aims at exploring the possible interplay among genetics, extracellular matrix remodeling, abnormal signaling pathways, oxidative stress and inflammation in contributing to BAV-associated aortopathy (BAV-A-A). Novel circulating biomarkers have been proposed as diagnostic tools able to improve risk stratification in BAV-A-A. However, to date, the precise molecular and cellular mechanisms that lead to BAV-A-A remain unknown. Genetic, hemodynamic and cardiovascular risk factors have been implicated in the development and progression of BAV-A-A. Oxidative stress may also play a role, similarly to what observed in atherosclerosis and vulnerable plaque formation. The identification of common pathways between these 2 conditions may provide a platform for future therapeutic solutions.

The science of BAV aortopathy

The aortopathy associated with bicuspid aortic valve (BAV) is an epidemiologically relevant source of chronic and acute aortic disease (aneurysm and dissection). However, its pathogenesis is still the object of scientific uncertainties and debates. Indeed, the mechanisms determining the diseases of the ascending aorta in BAV patients are most likely complex and multifactorial, i.e. resulting from variable modes of interplay between genetic and hemodynamic factors. Although few scientific studies have so far taken into adequate account this complexity, leaving the precise sequence of pathogenetic events still undiscovered, the accumulated evidence from previous research approaches have at least brought about important insights. While genetic studies have so far identified variants relevant to either valve malformation or aortic complications (including those in the genes NOTCH1, TGFBR2, ACTA2, GATA5, NKX2.5, SMAD6, ROBO4), however each explaining not more than 5% of the study population, other investigations have thoroughly described both the flow features, with consequent forces acting on the arterial wall (including skewed flow jet direction, rotational flow, wall shear stress), and the main changes in the molecular and cellular wall structure (including extracellular matrix degradation, smooth muscle cell changes, oxidative stress, unbalance of TGF-β signaling, aberrant endothelial-to-mesenchymal transition). All of this evidence, together with the recognition of the diverse phenotypes that the aortopathy can assume in BAV patients, holding possible prognostic significance, is reviewed in this chapter. The complex and multifaceted body of knowledge resulting from clinical and basic science studies on BAV aortopathy has the potential to importantly influence modes of clinical management of this disease in the near future.

Circulating microRNAs vs. aortic diameter in bicuspid aortic valve aortopathy

There is growing clinical need and interest to implement novel risk prediction tools in bicuspid aortic valve-associated proximal aortic disease, so-called bicuspid aortic valve aortopathy. Inherent limitations of the diameter-based risk stratification for adverse aortic events in bicuspid aortic valve aortopathy patients have recently been recognized. Therefore, alternative diagnostic tools and subsequent adjustments in the treatment guidelines are urgently needed. Herein, we summarize the current evidence on recent diagnostic developments to improve risk stratification in bicuspid aortic valve aortopathy, including circulating microRNAs as biomarkers to predict the progression of aortic disease.

Applications of a Specialty Bicuspid Aortic Valve Program: Clinical Continuity and Translational Collaboration

Bicuspid aortic valve (BAV) is a common congenital heart diagnosis and is associated with aortopathy. Current guidelines for aortic resection have been validated but are based on aortic diameter, which is insufficient to predict acute aortic events. Clinical and translational collaboration is necessary to identify biomarkers that can individualize the timing of prophylactic surgery for BAV aortopathy. We describe our multidisciplinary BAV program, including research protocols aimed at biomarker discovery and results from our longitudinal clinical registry. From 2012–2018, 887 patients enrolled in our clinical BAV registry with the option to undergo four dimensional flow cardiovascular magnetic resonance imaging (4D flow CMR) and donate serum plasma or tissue samples. Of 887 patients, 388 (44%) had an elective BAV-related procedure after initial presentation, while 499 (56%) continued with medical management. Of medical patients, 44 (9%) had elective surgery after 2.3 ± 1.4 years. Surgery patients’ biobank donations include 198 (46%) aorta, 374 (86%) aortic valve, and 314 (73%) plasma samples. The 4D flow CMR was completed for 215 (50%) surgery patients and 243 (49%) medical patients. Patients with BAV aortopathy can be safely followed by a multidisciplinary team to detect indications for surgery. Paired tissue and hemodynamic analysis holds opportunity for biomarker development in BAV aortopathy.

Shear Stress and Aortic Strain Associations With Biomarkers of Ascending Thoracic Aortic Aneurysm

BACKGROUND

This study aims to investigate the association of wall shear stress (WSS) and aortic strain with circulating biomarkers including matrix metalloproteinases (MMP), tissue inhibitors of metalloproteinase (TIMP), and exosomal level of microRNA (miRNA) in ascending aortic aneurysms of patients with bicuspid or tricuspid aortic valve.

METHODS

A total of 76 variables from 125 patients with ascending aortic aneurysms were collected from (1) blood plasma to measure plasma levels of miRNAs and protein activity; (2) computational flow analysis to estimate peak systolic WSS and time-average WSS (TAWSS); and (3) imaging analysis of computed tomography angiography to determine aortic wall strain. Principal component analysis followed by logistic regression allowed the development of a predictive model of aortic surgery by combining biomechanical descriptors and biomarkers.

RESULTS

The protein activity of MMP-1, TIMP-1, and MMP-2 was positively correlated to the systolic WSS and TAWSS observed in the proximal ascending aorta (eg, R = 0.52, P < .001, for MMP-1 with TAWSS) where local maxima of WSS were found. For bicuspid patients, aortic wall strain was associated with miR-26a (R = 0.55, P = .041) and miR-320a (R = 0.69, P < .001), which shows a significant difference between bicuspid and tricuspid patients. Receiver-operating characteristics curves revealed that the combination of WSS, MMP-1, TIMP-1, and MMP-12 is predictive of aortic surgery (area under the curve 0.898).

CONCLUSIONS

Increased flow-based and structural descriptors of ascending aortic aneurysms are associated with high levels of circulating biomarkers, implicating adverse vascular remodeling in the dilated aorta by mechanotransduction. A combination of shear stress and circulating biomarkers has the potential to improve the decision-making process for ascending aortic aneurysms to a highly individualized level.

Expression Patterns of Circulating MicroRNAs in the Risk Stratification of Bicuspid Aortopathy

Objective: Aortic size-based criteria are of limited value in the prediction of aortic events, while most aortic events occur in patients with proximal aortic diameters < 50 mm. Serological biomarkers and especially circulating microRNAs (miRNAs) have been proposed as an elegant tool to improve risk stratification in patients with different aortopathies. Therefore, we aimed to evaluate the levels of circulating miRNAs in a surgical cohort of patients presenting with bicuspid aortic valve disease and distinct valvulo-aortic phenotypes. Methods: We prospectively examined a consecutive cohort of 145 patients referred for aortic valve surgery: (1) Sixty three patients (mean age 47 ± 11 years, 92% male) with bicuspid aortic valve regurgitation and root dilatation (BAV-AR), (2) thirty two patients (mean age 59 ± 11 years, 73% male) with bicuspid aortic valve stenosis (BAV-AS), and (3) fifty patients (mean age 56 ± 14 years, 55% male) with tricuspid aortic valve stenosis and normal aortic root diameters (TAV-AS) who underwent aortic valve+/-proximal aortic surgery at a single institution. MicroRNAs analysis included 11 miRNAs, all published previously in association with aortopathies. Endpoints of our study were (1) correlation between circulating miRNAs and aortic diameter and (2) comparison of circulating miRNAs in distinct valvulo-aortic phenotypes. Results: We found a significant inverse linear correlation between circulating miRNAs levels and proximal aortic diameter in the whole study cohort. The strongest correlation was found for miR-17 (r = −0.42, p < 0.001), miR-20a (r = −0.37, p < 0.001), and miR-106a (r = −0.32, p < 0.001). All miRNAs were significantly downregulated in BAV vs. TAV with normal aortic root dimensions Conclusions: Our data demonstrate a significant inverse correlation between circulating miRNAs levels and the maximal aortic diameter in BAV aortopathy. When comparing miRNAs expression patterns in BAV vs. TAV patients with normal aortic root dimensions, BAV patients showed significant downregulation of analyzed miRNAs as compared to their TAV counterparts. Further multicenter studies in larger cohorts are needed to further validate these results.

Unravelling the Pathogenetic Mechanisms in Congenital Aortopathies: Need for an Integrative Translational Approach

Congenital heart disease (CHD)-associated aortopathy is a very heterogeneous entity with a wide spectrum of clinical presentations. The pathogenesis of aortopathy is still incompletely understood, and, therefore, the best prevention and management strategy is currently unknown. The most common entity of CHD-associated aortopathies is bicuspid aortic valve (BAV)-associated aortic disease (so called bicuspid aortopathy) that is found in 50%–60% of BAV individuals. BAV aortopathy has been reported in association with an increased risk of aortic events, especially aortic dissection and sudden cardiac death. Risk stratification of adverse aortic events is still very rudimentary and considers only the maximal aortic diameter, which makes it unsuitable for an individual risk prediction. This introductory Editorial highlights the unmet clinical need for more integrative and translational research to unravel pathogenetic pathways in the development of CHD-associated aortopathies, integrating recently identified genetic lesions and knowledge on circulating biomarkers and microstructural changes in the diseased aorta.

Aortic valve-related aortopathy: assessing optimal timing of surgical intervention

Introduction: Dilatation of the proximal aorta is often associated with an aortic valve disease (e.g. bicuspid aortic valve, aortic stenosis), so-called 'valve-related aortopathy.' The definition of optimal timing for surgical intervention in valve-related aortopathy remains incompletely clarified. The limited value of traditional diameter-based intervention criteria has been recognized and more sophisticated diagnostic tools are necessary.Areas covered: This article aims to give an overview on the most recent literature addressing the different forms of valve-related aortopathies and the optimal timing of surgical intervention. It highlights the valve morphotype-dependent (BAV vs TAV) and the valve lesion-dependent aortopathies (stenosis vs regurgitation) and outlines the current treatment options of those pathologies. Further, this review discusses novel serological and rheological markers, potentially helping in the decision-making process in valve-related aortopathy. Systematic literature searches were performed using PubMed and Embase up to July 2019.Expert opinion: The combination of serological biomarkers and quantitative rheological markers for transvalvular flow eccentricity might be an additional useful tool. A possible solution for the future could be a risk score which considers body-surface-adjusted aortic diameters, activity of certain circulating biomarkers, transvalvular flow patterns, possible connective tissue disorders, and the valve morphology to define an individualized treatment strategy.

Risk Stratification in Bicuspid Aortic Valve Aortopathy: Emerging Evidence and Future Perspectives

The current management of aortic dilatation associated with congenital bicuspid aortic valve (bicuspid aortic valve aortopathy) is based on dimensional parameters (diameter of the aneurysm, growth of the diameter over time) and few other criteria. The disease is however heterogeneous in terms of natural and clinical history and risk of acute complications, ie aortic dissection. Dimensional criteria are now admitted to have limited value as predictors of such complications. Thus, novel principles for risk stratification have been recently investigated, including phenotypic criteria, flow-related metrics, and circulating biomarkers. A systematization of the typical anatomoclinical forms that the aortopathy can assume has led to the identification of the more severe root phenotype, associated with higher risk of progression of the aneurysm and possible higher aortic dissection risk. Four-dimensional-flow magnetic resonance imaging studies are searching for potentially clinically significant metrics of flow derangement, based on the recognized association of local abnormal shear stress with wall pathology. Other research initiatives are addressing the question whether circulating molecules could predict the presence or, more importantly, the future development of aortopathy. The present review summarizes the latest progresses in the knowledge on risk stratification of bicuspid aortic valve aortopathy, focusing on critical aspects and debated points.

microRNAs in bicuspid aortic valve associated aortopathy: Recent advances and future perspectives

The risk of acute aortic events in patients with bicuspid aortic valve (BAV) constitutes a medical concern in terms of timing and surgical decision. During the past years, there has been a growing interest in the potential of microRNAs (miRNAs) as crucial epigenetic factors in multiple cellular processes associated with BAV aortopathy. Nevertheless, there are still challenges that need to be overcome before miRNAs could enter clinical practice, and further validation studies in larger and well-defined BAV cohorts are now required. This review aims at providing a comprehensive overview of the available data on the expression profiles and function of specific miRNAs in BAV aortopathy, evaluating miRNA signatures as potential molecular markers of disease. We also discuss the role of other novel classes of non-coding RNAs, including long non-coding RNAs and circular RNAs, in BAV-associated aortopathy, mainly regarding their possible implementation as diagnostic and prognostic markers.

Epigenetic influences on genetically triggered thoracic aortic aneurysm

Genetically triggered thoracic aortic aneurysms (TAAs) account for 30% of all TAAs and can result in early morbidity and mortality in affected individuals. Epigenetic factors are now recognised to influence the phenotype of many genetically triggered conditions and have become an area of interest because of the potential for therapeutic manipulation. Major epigenetic modulators include DNA methylation, histone modification and non-coding RNA. This review examines epigenetic modulators that have been significantly associated with genetically triggered TAAs and their potential utility for translation to clinical practice.

Novel Approaches for BAV Aortopathy Prediction-Is There a Need for Cohort Studies and Biomarkers?

Bicuspid aortic valve (BAV) disease is the most common congenital malformation of the human heart with a prevalence of 1–2% in the general population. More than half of patients with a BAV present with a dilated proximal aorta (so-called bicuspid aortopathy) which is associated with an enhanced risk of life-threatening aortic complications. Up to now, the pathogenesis of bicuspid aortopathy as well as the risk stratification of aortic complications has not yet been sufficiently clarified. Recent findings have shown that bicuspid aortopathy features phenotypic heterogeneity. Two distinct valvulo-aortic phenotypes, the so-called root phenotype, as well as a dilation of the tubular ascending aorta, coincide with a significantly different risk for aortal complications. However, the phenotype-based classification that is only based on these two clinical forms is not sufficient to estimate the risk of aortal complications in a prognostically relevant way. Therefore, there is growing clinical interest to assess novel approaches in BAV research and to introduce circulating biomarkers as an elegant diagnostic tool to improve risk stratification in BAV aortopathy. A large scale epidemiological cohort study, ranking from apparently healthy individuals to disease patients, and comprehensive biobanks provide the opportunity to study BAV disease and its complications and to identify novel biomarkers for BAV aortopathy surveillance and prognosis. Firstly, the data indicate that several protein-based biomarkers and non-coding RNA molecules, in particular circulating microRNAs, can serve as relevant molecular biomarkers to predict the course of BAV-associated aortopathy. Here, we review the current literature and knowledge about BAV from a clinical point of view, and report about novel approaches in BAV biomarker research.