Multi-omics in thoracic aortic aneurysm: the complex road to the simplification

BACKGROUND

Thoracic aortic aneurysm (TAA) is a serious condition that affects the aorta, characterized by the dilation of its first segment. The causes of TAA (e.g., age, hypertension, genetic syndromes) are heterogeneous and contribute to the weakening of the aortic wall. This complexity makes treating this life-threatening aortopathy challenging, as there are currently no etiological therapy available, and pharmacological strategies, aimed at avoiding surgical aortic replacement, are merely palliative. Recent studies on novel therapies for TAA have focused on identifying biological targets and etiological mechanisms of the disease by using advanced -omics techniques, including epigenomics, transcriptomics, proteomics, and metabolomics approaches.

METHODS

This review presents the latest findings from -omics approaches and underscores the importance of integrating multi-omics data to gain more comprehensive understanding of TAA.

RESULTS

Literature suggests that the alterations in TAA mediators frequently involve members of pro-fibrotic process (i.e., TGF-β signaling pathways) or proteins associated with cell/extracellular structures (e.g., aggrecans). Further analyses often reported the importance in TAA of processes as inflammation (PCR, CD3, leukotriene compounds), oxidative stress (chromatin OXPHOS, fatty acids), mitochondrial respiration and glycolysis/gluconeogenesis (e.g., PPARs and HIF1a). Of note, more recent metabolomics studies added novel molecular markers to the list of TAA-specific detrimental mediators (proteoglycans).

CONCLUSION

It is increasingly clear that integrating data from different -omics branches, along with clinical data, is essential as well as complicated both to reveal hidden relevant information and to address complex diseases such as TAA. Importantly, recent progresses in metabolomics highlighted novel potential and unprecedented marks in TAA diagnosis and therapy.

Marfan Syndrome: Enhanced Diagnostic Tools and Follow-up Management Strategies

Marfan syndrome (MFS) is a rare inherited autosomic disorder, which encompasses a variety of systemic manifestations caused by mutations in the Fibrillin-1 encoding gene (FBN1). Cardinal clinical phenotypes of MFS are highly variable in terms of severity, and commonly involve cardiovascular, ocular, and musculoskeletal systems with a wide range of manifestations, such as ascending aorta aneurysms and dissection, mitral valve prolapse, ectopia lentis and long bone overgrowth, respectively. Of note, an accurate and prompt diagnosis is pivotal in order to provide the best treatment to the patients as early as possible. To date, the diagnosis of the syndrome has relied upon a systemic score calculation as well as DNA mutation identification. The aim of this review is to summarize the latest MFS evidence regarding the definition, differences and similarities with other connective tissue pathologies with severe systemic phenotypes (e.g., Autosomal dominant Weill-Marchesani syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome) and clinical assessment. In this regard, the management of MFS requires a multidisciplinary team in order to accurately control the evolution of the most severe and potentially life-threatening complications. Based on recent findings in the literature and our clinical experience, we propose a multidisciplinary approach involving specialists in different clinical fields (i.e., cardiologists, surgeons, ophthalmologists, orthopedics, pneumologists, neurologists, endocrinologists, geneticists, and psychologists) to comprehensively characterize, treat, and manage MFS patients with a personalized medicine approach.

Basigin genetic depletion reduces thoracic aortic aneurysm formation in marfan syndrome mice

Background

Marfan Syndrome (MFS) is a rare genetic disease due to mutations in fibrillin 1 gene [1]. It is characterized by thoracic aortic aneurysm (TAA), whose dissection is the major cause of morbidity and mortality in MFS patients [2]. While pathological mechanisms underlying MFS extracellular matrix remodelling have started to be elucidated, an etiological treatment is not available yet [3,4]. Recently, EMMPRIN has been proposed as new actor in pro-fibrotic processes associated with TAA development in MFS patients [4,5].

Purpose

To confirm the role of EMMPRIN (i.e. Basigin in mice, Bsg) in TAA formation and progression in a preclinical setting, we assessed whether Bsg genetic depletion in a mouse model of MFS (Fbn1C1039G/+) [6] had an impact on aortic phenotype.

Methods

We generated a double transgenic mouse model, Fbn1C1039G/+-Bsg+/−, by crossing commercially available Fbn1C1039G/+ with Bsg+/− mice (provided by Dr. Kadomatsu) [7] and we prospectively measured aortic root size in 12 Fbn1C1039G/+-Bsg+/−, 9 Fbn1C1039G/+, and 15 WT mice every 4 weeks from 12 to 20 weeks of age by 2D-echocardiography. Both qRT-PCR and Western Blot were used to evaluate EMMPRIN downstream pro-fibrotic pathway activation in thoracic aortic tissue obtained from mice sacrificed at 12 weeks. Plasma soluble EMMPRIN (sEMMPRIN) levels were assessed by ELISA.

Results

Echocardiographic assessment at 12 and 20 weeks of age confirmed significantly dilated aortic root in Fbn1C1039G/+ vs WT (mean±SD at 12 weeks: 1.772±0.081 vs 1.394±0.068 mm, respectively, p<0.0001; 20 weeks: 1.899±0.103 vs 1.520±0.083 mm, respectively, p<0.0001), and revealed that Fbn1C1039G/+-Bsg+/− mice had lower aortic root diameter extent compared to Fbn1C1039G/+ (12 weeks: 1.667±0.109 vs 1.772±0.081 mm, respectively, p=0.026; 20 weeks: 1.752±0.129 vs 1.899±0.103 mm, respectively, p=0.011). Pro-fibrotic gene profiling in a subset of 12 weeks old mice showed that Col1A1, Col3A1 and FN1 genes were more expressed in Fbn1C1039G/+ than in WT mice and that the up-regulation of these genes was mitigated in Fbn1C1039G/+ by Bsg depletion (ANOVA p=0.048, p=0.055, and p=0.0003, respectively). Moreover, we found a significant activation of the EMMPRIN downstream pro-fibrotic ERK1/2 pathway in Fbn1C1039G/+ compared to WT mice which was attenuated in the Fbn1C1039G/+-Bsg+/− model (p=0.030). Plasma sEMMPRIN levels were lower in Fbn1C1039G/+ than in WT mice, consistent with what we previously observed in MFS patients [5], and decreased over time in both Fbn1C1039G/+ and WT mice (2-way ANOVA disease p=0.013, time p=0.012, interaction p=ns).

Conclusions

Basigin genetic depletion reduces dilatation of the aortic root and pro-fibrotic pathway activation in a preclinical MFS model, confirming previous proof-of-concept findings and paving the way for the development of innovative therapies for MFS patients. Plasma sEMMPRIN levels stand as promising tool to predict the aortic enlargement progression in MFS models and patients.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Italian Ministery of Health

Relationship Between Plasma Osteopontin and Arginine Pathway Metabolites in Patients With Overt Coronary Artery Disease

Introduction

Osteopontin (OPN) is involved in ectopic calcification. Its circulating form is upregulated in coronary artery disease (CAD) patients. Circulating OPN levels positively correlate with oxidative stress, one of the major triggers of endothelial dysfunction. Endothelial dysfunction is, in turn, associated with reduced nitric oxide (NO) bioavailability due to the impaired arginine pathway. The aim of this study was to better understand the correlations between OPN, oxidative stress markers, and the arginine pathway metabolites.

Methods and Results

ELISA and mass spectrometry techniques have been used to evaluate circulating OPN and arginine pathway/oxidative stress metabolites, respectively, in twenty-five control subjects and thirty-three patients with overt atherosclerosis. OPN positively correlates with 2,3-dinor-8isoPGF2a levels (p = 0.02), ornithine (p = 0.01), ADMA (p = 0.001), SDMA (p = 0.03), and citrulline (p = 0.008) levels only in CAD patients. In addition, citrulline positively correlated with ADMA (p = 0.02) levels, possibly as result of other sources of citrulline biosynthetic pathways.

Conclusion

The association between OPN and impaired arginine/NO pathway could play a role in the inhibition of endothelial NO synthase (eNOS) and/or in the arginase activation in the context of CAD patients. However, further studies are needed to verify the cause-effect relationship between OPN, oxidative stress, and arginine/NO pathway dysregulation.

Cyclophilin A inhibition as potential treatment of human aortic valve calcification

Aortic valve stenosis (AS) is a pathological condition that affects about 3% of the population, representing the most common valve disease. The main clinical feature of AS is represented by the impaired leaflet motility, due to calcification, which leads to the left ventricular outflow tract obstruction during systole. The formation and accumulation of calcium nodules are driven by valve interstitial cells (VICs). Unfortunately, to date, the in vitro and in vivo studies were not sufficient to fully recapitulate all the pathological pathways involved in AS development, as well as to define a specific and effective pharmacological treatment for AS patients. Cyclophilin A (CyPA), the most important immunophilin and endogenous ligand of cyclosporine A (CsA), is strongly involved in several detrimental cardiovascular processes, such as calcification. To date, there are no data on the CyPA role in VIC-mediated calcification process of AS. Here, we aimed to identify the role of CyPA in AS by studying VIC calcification, in vitro. In this study, we found that (i) CyPA is up-regulated in stenotic valves of AS patients, (ii) pro-calcifying medium promotes CyPA secretion by VICs, (iii) in vitro treatment of VICs with exogenous CyPA strongly stimulates calcium deposition, and (iv) exogenous CyPA inhibition mediated by CsA analogue MM284 abolished in vitro calcium potential. Thus, CyPA represents a biological target that may act as a novel candidate in the detrimental AS development and its inhibition may provide a novel pharmacological approach for AS treatment.

Impact of Oxidative Stress and Protein S-Glutathionylation in Aortic Valve Sclerosis Patients with Overt Atherosclerosis

Aortic valve sclerosis (AVSc) is characterized by non-uniform thickening of the leaflets without hemodynamic changes. Endothelial dysfunction, also caused by dysregulation of glutathione homeostasis expressed as ratio between its reduced (GSH) and its oxidised form (GSSG), could represent one of the pathogenic triggers of AVSc. We prospectively enrolled 58 patients with overt atherosclerosis and requiring coronary artery bypass grafting (CABG). The incidence of AVSc in the studied population was 50%. The two groups (No-AVSc and AVSc) had similar clinical characteristics. Pre-operatively, AVSc group showed significantly lower GSH/GSSG ratio than No-AVSc group (p = 0.02). Asymmetric dimethylarginine (ADMA) concentration was significantly higher in AVSc patients compared to No-AVSc patients (p < 0.0001). Explanted sclerotic aortic valves presented a significantly increased protein glutathionylation (Pr-SSG) than No-AVSc ones (p = 0.01). In vitro, inhibition of glutathione reductase caused β-actin glutathionylation, activation of histone 2AX, upregulation of α2 smooth muscle actin (ACTA2), downregulation of platelet and endothelial cell adhesion molecule 1 (PECAM1) and cadherin 5 (CDH5). In this study, we showed for the first time that the dysregulation of glutathione homeostasis is associated with AVSc. We found that Pr-SSG is increased in AVSc leaflets and it could lead to EndMT via DNA damage. Further studies are warranted to elucidate the causal role of Pr-SSG in aortic valve degeneration.

MiRNA profiling revealed enhanced susceptibility to oxidative stress of endothelial cells from bicuspid aortic valve

AIMS

Calcific aortic valve stenosis (CAVS) is the most frequent manifestation of aortic valve disease and the third leading cause of cardiovascular disease in the Western countries associated with significant morbidity and mortality. An active biological progression involving inflammation and oxidation leading to valve endothelial damage is considered a hallmark of the early stages of valve degeneration. However, tricuspid (TAV) and bicuspid (BAV) aortic valve deterioration are considered to differ only by shear stress. We hypothesized that endothelial cells (EC) derived from BAV and TAV patients have different miRNA expression patterns and thus distinct pathways could lead to endothelial damage in BAV than TAV patients.

METHODS AND RESULTS

We isolated ECs from patients with bicuspid or tricuspid aortic valve, which underwent surgery due to CAVS. MiRNA expression profile by PCR revealed eight upregulated miRNAs between BAV and TAV ECs. Functional analysis identified that BAV ECs presented altered cellular response to oxidative stress and DNA damage stimulus via p53 and alteration in the intrinsic apoptotic signaling pathway. GPX3 and SRXN1 mRNA were express at lower levels in BAV compared to TAV ECs, leading to an increment of DNA double-strand breaks. BAV ECs had a sustained apoptosis activation when compared to TAV ECs. This difference was exacerbated by oxidative stress stimulus leading to a reduced survival rate but completely reverted by miR-328-3p inhibition.

CONCLUSION

The present data showed molecular differences in oxidative stress susceptibility, DNA damage magnitude, and apoptosis induction between ECs derived from BAV and TAV patients.

Soluble EMMPRIN levels discriminate aortic ectasia in Marfan syndrome patients

Marfan syndrome (MFS) is a rare genetic disease characterized by a matrix metalloproteases (MMPs) dysregulation that leads to extracellular matrix degradation. Consequently, MFS patients are prone to develop progressive thoracic aortic enlargement and detrimental aneurysm. Since MMPs are activated by the extracellular MMP inducer (EMMPRIN) protein, we determined whether its plasmatic soluble form (sEMMPRIN) may be considered a marker of thoracic aortic ectasia (AE). Methods: We compared plasma sEMMPRIN levels of 42 adult Caucasian MFS patients not previously subjected to aortic surgery with those of matched healthy controls (HC) by ELISA. In the MFS cohort we prospectively evaluated the relationship between plasma sEMMPRIN levels and the main MFS-related manifestations. Results: MFS patients had lower plasma sEMMPRIN levels (mean±SD: 2071±637 pg/ml) than HC (2441±642 pg/ml, p=0.009). Amongst all considered MFS-related clinical features, we found that only aortic root dilatation associated with circulating sEMMPRIN levels. Specifically, plasma sEMMPRIN levels negatively correlated with aortic Z-score (r=-0.431, p=0.004), and were significantly lower in patients with AE (Z-score≥2, 1788±510 pg/ml) compared to those without AE (Z-score<2, 2355±634 pg/ml; p=0.003). ROC curve analysis revealed that plasma sEMMPRIN levels discriminated patients with AE (AUC [95%CI]: 0.763 [0.610-0.916], p=0.003) with 85.7% sensitivity, 76.2% specificity, and 81% accuracy. We defined plasma sEMMPRIN levels ≤2246 pg/ml as the best threshold discriminating the presence of AE in MFS patients with an odds ratio [95%CI] of 19.2 [3.947-93.389] (p<0.001). Conclusions: MFS patients are characterized by lower sEMMPRIN levels than HC. Notably, plasma sEMMPRIN levels are strongly associated with thoracic AE.

Cell models of arrhythmogenic cardiomyopathy: advances and opportunities

Arrhythmogenic cardiomyopathy is a rare genetic disease that is mostly inherited as an autosomal dominant trait. It is associated predominantly with mutations in desmosomal genes and is characterized by the replacement of the ventricular myocardium with fibrous fatty deposits, arrhythmias and a high risk of sudden death. In vitro studies have contributed to our understanding of the pathogenic mechanisms underlying this disease, including its genetic determinants, as well as its cellular, signaling and molecular defects. Here, we review what is currently known about the pathogenesis of arrhythmogenic cardiomyopathy and focus on the in vitro models that have advanced our understanding of the disease. Finally, we assess the potential of established and innovative cell platforms for elucidating unknown aspects of this disease, and for screening new potential therapeutic agents. This appraisal of in vitro models of arrhythmogenic cardiomyopathy highlights the discoveries made about this disease and the uses of these models for future basic and therapeutic research.

Summary:In vitro models of ACM provide insights into the molecular mechanisms of this disease. This reappraisal offers a comprehensive vision of past discoveries and constitutes a tool for future research.

Pathophysiology of Aortic Stenosis and Mitral Regurgitation

The global impact of the spectrum of valve diseases is a crucial, fast-growing, and underrecognized health problem. The most prevalent valve diseases, requiring surgical intervention, are represented by calcific and degenerative processes occurring in heart valves, in particular, aortic and mitral valve. Due to the increasing elderly population, these pathologies will gain weight in the global health burden. The two most common valve diseases are aortic valve stenosis (AVS) and mitral valve regurgitation (MR). AVS is the most commonly encountered valve disease nowadays and affects almost 5% of elderly population. In particular, AVS poses a great challenge due to the multiple comorbidities and frailty of this patient subset. MR is also a common valve pathology and has an estimated prevalence of 3% in the general population, affecting more than 176 million people worldwide. This review will focus on pathophysiological changes in both these valve diseases, starting from the description of the anatomical aspects of normal valve, highlighting all the main cellular and molecular features involved in the pathological progression and cardiac consequences. This review also evaluates the main approaches in clinical management of these valve diseases, taking into account of the main published clinical guidelines. © 2017 American Physiological Society. Compr Physiol 7:799-818, 2017.

Abstract P107: Hypertension Enhances the Differentiation of Cardiac Fibroblasts Into Myofibroblasts After TGF-beta1 Treatment

Objectives: In cardiac fibrosis associated with hypertension, TGF-beta1 plays a key role by acting on differentiation of cardiac fibroblasts (CF) into alpha-smooth muscle actin (alpha-SMA)-positive myofibroblasts. In this study, we tested the effect of TGF-beta1 during the myofibroblast differentiation process of CF from normotensive and hypertensive rats.

Methods: CF were obtained by enzymatic digestion of hearts isolated from Spontaneously Hypertensive (hCF) and normotensive Wistar Kyoto (nCF) rats (n=5 rat/group). Gene and protein expression in CF was evaluated by Western blot and qRT-PCR analyses, respectively. Immunohistochemistry analysis for integrin alpha-v beta-5 was performed on rat cardiac tissue (n=5 rat/group).

Results: Cultured hCF showed an enhanced SMAD2/3 activation and alpha-SMA protein expression after treatment with TGF-beta1 (5 ng/ml) in comparison with nCF. Alpha-SMA up-regulation was further confirmed by qRT-PCR analysis that showed a significant increase in alpha-SMA gene expression in hCF after TGF-beta1 treatment (2.78±0.25 vs 2.01±0.21 fold increase, p <0.05). Moreover, immunostaining on cardiac tissues revealed a higher expression of integrin alpha-v beta-5 in hypertensive vs normotensive rat hearts (345.3±170.0 vs 48.2±22.3 mm 2 of integrin-positive area, p <0.05). This result was also confirmed in vitro ; indeed, integrin alpha-v beta-5 gene expression in hCF increased 2.8-fold in basal condition and 5.12-fold after TGF-beta1 treatment when compared to untreated nCF.

Conclusions: Taken together, these results suggest that hCF are more prone to upregulate integrin alpha-v beta-5 and consequently differentiate into myofibroblasts in vitro under TGF-beta1 treatment. Thus, targeting alpha-v beta-5 might open a novel prospective for the treatment of fibrosis in hypertensive hearts likely reducing integrin-mediated TGF-beta1 activation.

Vascular smooth muscle cells in Marfan syndrome aneurysm: the broken bricks in the aortic wall

Marfan syndrome (MFS) is a connective tissue disorder with multiple organ manifestations. The genetic cause of this syndrome is the mutation of the FBN1 gene, encoding the extracellular matrix (ECM) protein fibrillin-1. This genetic alteration leads to the degeneration of microfibril structures and ECM integrity in the tunica media of the aorta. Indeed, thoracic aortic aneurysm and dissection represent the leading cause of death in MFS patients. To date, the most effective treatment option for this pathology is the surgical substitution of the damaged aorta. To highlight novel therapeutic targets, we review the molecular mechanisms related to MFS etiology in vascular smooth muscle cells, the foremost cellular type involved in MFS pathogenesis.

Assessing cytokines' talking patterns following experimental myocardial damage by applying Shannon's information theory

BACKGROUND

The simultaneous measurement of multiple cytokines in parallel by using multiplex proteome arrays (MPA) is of great interest to understanding the inflammatory response following myocardial infarction; however, since cytokines are pleiotropic and redundant, increase of information throughput (IT) attained by measuring multiple cytokines remain to be determined. We aimed this study to assess the IT of an MPA system designed to assess 8 cytokines - commercially available at the time of the study - serum levels, before (control state) and after experimental myocardial cryoinjury (activated state) in rats.

METHODS

By assuming that redundant information do not generally increase the IT, we derived Entropy (H) and Redundancy (R) of information by using formulas of Shannon modified accordingly, where a high IT (high H and low R) corresponds to a low level of correlation between cytokines and vice versa for a low IT. The maximum theoretical level of IT and the contribution of each cytokine were also estimated.

RESULTS

In control state, no significant correlations were found between cytokines showing high IT; on the contrary, in activated state, several significant correlations were found supporting a complex cross-talk pattern between cytokines with low IT. Using as reference the maximum theoretical level of IT, in activated state, H was reduced of 67.0% and R was increased of 77.4% supporting a reduction of IT. Furthermore, the contribution of individual cytokines to H value of MPA was variable: in control state, IL-2 gave the most contribution to H value, conversely during activated state IL-10 gave most contribution. Finally during activated state, IL-1β was the only cytokine strongly correlated with values of all other cytokines, suggesting a crucial role in the inflammatory cascade.

CONCLUSIONS

Paradoxically, by analyzing an MPA system designed for redundant analytes such as cytokines, translating the Shannon's information theory from the field of communication to biology, the IT system in our model deteriorates during the activation state by increasing its redundancy, showing maximum value of entropy in the control conditions. Finally, the study of the mutual interdependence between cytokines by the contribution to the IT may allow formulating alternative models to describe the inflammatory cascade after myocardial infarction.

Immunohistochemical expression of oncological proliferation markers in the hearts of rats during normal pregnancy

Aim: Pregnancy is characterized by left ventricular hypertrophy that is potentially accounted for by cardiomyocyte proliferation, although no such evidence is currently available. This study investigates if the left ventricular mass (LVM) increase during pregnancy implies cell hyperplasia. Materials & methods: In nonpregnant and late-pregnant rats, cardiac function and LVM were evaluated by MRI, and cardiomyocyte dimensions and proliferations were assessed quantitatively by morphometric analysis and immunohistochemistry using oncological markers (Ki67 and MCM2). Results: In late-pregnant rats, LVM and cardiomyocyte area were greater. No mitotic figures were found nor was there any significant difference between groups in Ki67 expression. MCM2 expression was related to LVM. Conclusion: During pregnancy, rat cardiomyocytes undergo hypertrophy but not hyperplasia; the expression of MCM2, related to LVM, suggests it could be a marker of protein synthesis. The application of oncological markers to physiological contexts may provide insight into their role within the cell cycle.

Limited hypotensive effect of sildenafil in a high-risk population: a preliminary report

Erectile dysfunction (ED) is often associated with cardiovascular disease (CVD) and the risk of sildenafil-induced orthostatic hypotension (OH) in subjects with CVD is a matter of concern. We describe our experience in using the tilt test (TT) with continuous plethysmography to evaluate the occurrence of OH in patients with CVD and ED after a test dose of sildenafil. When sildenafil was added on top of their usual pharmacological treatment two patients out of 32 (6.2%) developed asymptomatic OH, with a maximum blood pressure fall of 40/20 mm Hg. The low prevalence and modest clinical relevance of OH in our high-risk population coupled with the known high sensitivity and reproducibility of the TT seem to suggest that sildenafil is haemodynamically safer than is generally believed even when added on top of vasoactive treatment. These findings should be put into perspective against the growing wealth of evidence that PDE5 inhibitors may have therapeutic potential for a number of CV conditions.