The ECM is the key structural component determining dilatation and aneurysm formation in the aortic wall. 8 Abdominal aortic aneurysms (AAAs) are characterized by loss of elastin and increased collagen turnover. Apart from miR-29, the miR-15 family has been implicated in collagen remodeling and the characteristic postnatal silencing of elastin.9 The miR-15 family consists of 6 highly conserved microRNAs (miR-15a, miR15b, miR-16-1, miR-16-2, miR-195, and miR-497), which are clustered on 3 separate chromosomes. They have a common seed region (AGCAGCA) and varying degrees of sequence homology in the 3′ region of the mature microRNA.

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Supplemental Digital Content is available in the text.

AimsExtracellular matrix remodelling has been implicated in a number of vascular conditions, including venous hypertension and varicose veins. However, to date, no systematic analysis of matrix remodelling in human veins has been performed.Methods and resultsTo understand the consequences of venous hypertension, normal and varicose veins were evaluated using proteomics approaches targeting the extracellular matrix. Varicose saphenous veins removed during phlebectomy and normal saphenous veins obtained during coronary artery bypass surgery were collected for proteomics analysis. Extracellular matrix proteins were enriched from venous tissues. The proteomics analysis revealed the presence of >150 extracellular matrix proteins, of which 48 had not been previously detected in venous tissue. Extracellular matrix remodelling in varicose veins was characterized by a loss of aggrecan and several small leucine-rich proteoglycans and a compensatory increase in collagen I and laminins. Gene expression analysis of the same tissues suggested that the remodelling process associated with venous hypertension predominantly occurs at the protein rather than the transcript level. The loss of aggrecan in varicose veins was paralleled by a reduced expression of aggrecanases. Chymase and tryptase β1 were among the up-regulated proteases. The effect of these serine proteases on the venous extracellular matrix was further explored by incubating normal saphenous veins with recombinant enzymes. Proteomics analysis revealed extensive extracellular matrix degradation after digestion with tryptase β1. In comparison, chymase was less potent and degraded predominantly basement membrane-associated proteins.ConclusionThe present proteomics study provides unprecedented insights into the expression and degradation of structural and regulatory components of the vascular extracellular matrix in varicosis.

Original research article BACKGROUND: Myocardial fibrosis is a feature of many cardiac diseases. We used proteomics to profile glycoproteins in the human cardiac extracellular matrix (ECM). METHODS:Atrial specimens were analyzed by mass spectrometry after extraction of ECM proteins and enrichment for glycoproteins or glycopeptides.RESULTS: ECM-related glycoproteins were identified in left and right atrial appendages from the same patients. Several known glycosylation sites were confirmed. In addition, putative and novel glycosylation sites were detected. On enrichment for glycoproteins, peptides of the small leucine-rich proteoglycan decorin were identified consistently in the flowthrough. Of all ECM proteins identified, decorin was found to be the most fragmented. Within its protein core, 18 different cleavage sites were identified. In contrast, less cleavage was observed for biglycan, the most closely related proteoglycan. Decorin processing differed between human ventricles and atria and was altered in disease. The C-terminus of decorin, important for the interaction with connective tissue growth factor, was detected predominantly in ventricles in comparison with atria. In contrast, atrial appendages from patients in persistent atrial fibrillation had greater levels of full-length decorin but also harbored a cleavage site that was not found in atrial appendages from patients in sinus rhythm. This cleavage site preceded the N-terminal domain of decorin that controls muscle growth by altering the binding capacity for myostatin. Myostatin expression was decreased in atrial appendages of patients with persistent atrial fibrillation and hearts of decorin null mice. A synthetic peptide corresponding to this decorin region dose-dependently inhibited the response to myostatin in cardiomyocytes and in perfused mouse hearts. CONCLUSIONS:This proteomics study is the first to analyze the human cardiac ECM. Novel processed forms of decorin protein core, uncovered in human atrial appendages, can regulate the local bioavailability of antihypertrophic and profibrotic growth factors.glycoproteomics reveals Decorin Peptides With anti-Myostatin activity in human atrial Fibrillation

Background: Remodelling of the extracellular matrix (ECM) is a hallmark of heart failure (HF). Our previous analysis of the secretome of murine cardiac fibroblasts returned ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5) as one of the most abundant proteases. ADAMTS5 cleaves chondroitin sulphate proteoglycans (CSPGs) such as versican. The contribution of ADAMTS5 and its substrate versican to HF is unknown. Methods: Versican remodelling was assessed in mice lacking the catalytic domain of ADAMTS5 (Adamts5 △Cat ). Proteomics was applied to study ECM remodelling in left ventricular samples from HF patients, with a particular focus on the effects of common medications used for the treatment of HF. Results: Versican and versikine, an ADAMTS-specific versican cleavage product, accumulated in ischemic HF patients. Versikine was also elevated in a porcine model of cardiac ischemia/reperfusion injury and in murine hearts after angiotensin II (Ang II) infusion. In Adamts5 △Cat mice, Ang II infusion resulted in an aggravated versican build-up and hyaluronic acid disarrangement, accompanied by reduced levels of integrin beta 1, filamin A and connexin 43. Echocardiographic assessment of Adamts5 △Cat mice revealed a reduced ejection fraction and an impaired global longitudinal strain upon Ang II infusion. Cardiac hypertrophy and collagen deposition, however, were similar to littermate controls. In a proteomics analysis of a larger cohort of cardiac explants from ischemic HF patients (n=65), the use of β-blockers was associated with a reduction in ECM deposition, with versican being among the most pronounced changes. Subsequent experiments in cardiac fibroblasts confirmed that β1-adrenergic receptor stimulation increased versican expression. Despite similar clinical characteristics, HF patients treated with β-blockers had a distinct cardiac ECM profile. Conclusions: Our results in animal models and patients suggest that ADAMTS proteases are critical for versican degradation in the heart, and that versican accumulation is associated with impaired cardiac function. A comprehensive characterisation of the cardiac ECM in ischemic HF patients revealed that β−blockers may have a previously unrecognized beneficial effect on the cardiac CSPG content.

Aims A mutation in the phospholamban (PLN) gene, leading to deletion of Arg14 (R14del), has been associated with malignant arrhythmias and ventricular dilation. Identifying pre-symptomatic carriers with vulnerable myocardium is crucial because arrhythmia can result in sudden cardiac death, especially in young adults with PLN-R14del mutation. This study aimed at assessing the efficiency and efficacy of in vivo genome editing, using CRISPR/Cas9 and a cardiotropic adeno-associated virus (AAV9), in improving cardiac function in young adult mice expressing the human PLN-R14del. Methods and Results Humanized mice were generated expressing human wild-type (hPLN-WT) or mutant (hPLN-R14del) PLN in the heterozygous state, mimicking human carriers. Cardiac magnetic resonance imaging at 12 weeks of age showed bi-ventricular dilation and increased stroke volume in mutant vs. WT mice, with no deficit in ejection fraction or cardiac output. Challenge of ex vivo hearts with isoproterenol and rapid pacing unmasked higher propensity for sustained ventricular tachycardia (VT) in hPLN-R14del relative to hPLN-WT. Specifically, the VT threshold was significantly reduced (20.3±1.2 Hz in hPLN-R14del vs. 25.7±1.3 Hz in WT, p < 0.01) reflecting higher arrhythmia burden. To inactivate the R14del allele, mice were tail-vein-injected with AAV9.CRISPR/Cas9/gRNA or AAV9 empty capsid (controls). CRISPR-Cas9 efficiency was evaluated by droplet digital PCR and NGS-based amplicon sequencing. In vivo gene editing significantly reduced end diastolic and stroke volumes in hPLN-R14del CRISPR-treated mice compared to controls. Susceptibility to VT was also reduced, as the VT threshold was significantly increased relative to controls (30.9±2.3 Hz vs. 21.3±1.5 Hz; p < 0.01). Conclusions This study is the first to show that disruption of hPLN-R14del allele by AAV9- CRISPR/Cas9 improves cardiac function and reduces VT susceptibility in humanized PLN-R14del mice, offering preclinical evidence for translatable approaches to therapeutically suppress the arrhythmogenic phenotype in human patients with PLN-R14del disease. Translational Perspective The phospholamban R14del mutation causes dilated and arrhythmogenic cardiomyopathies, with increased risk of malignant ventricular arrhythmias in young adult carriers. With few available therapeutic options, heart transplantation is often the ultimate treatment. This study presents the first humanized mouse model of PLN-R14del disease, reveals the ability to detect abnormal cardiac function and increased arrhythmogenic vulnerability in pre-symptomatic hPLN-R14del mice, and demonstrates that allele-specific disruption of R14del using in vivo AAV9/CRISPR-Cas9 reverses the disease phenotype. This preclinical study offers promising translatable approaches to detect and therapeutically suppress the arrhythmogenic phenotype in patients with PLN-R14del disease and potentially other inherited cardiomyopathies.

Fibrosis is a hallmark of many cardiovascular diseases and is associated with the exacerbated secretion and deposition of the extracellular matrix (ECM). Using proteomics, we have previously identified more than 150 ECM and ECM-associated proteins in cardiovascular tissues. Notably, many ECM proteins are glycosylated. This post-translational modification affects protein folding, solubility, binding, and degradation. We have developed a sequential extraction and enrichment method for ECM proteins that is compatible with the subsequent liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of intact glycopeptides. The strategy is based on sequential incubations with NaCl, SDS for tissue decellularization, and guanidine hydrochloride for the solubilization of ECM proteins. Recent advances in LC-MS/MS include fragmentation methods, such as combinations of higher-energy collision dissociation (HCD) and electron transfer dissociation (ETD), which allow for the direct compositional analysis of glycopeptides of ECM proteins. In the present paper, we describe a method to prepare the ECM from tissue samples. The method not only allows for protein profiling but also the assessment and characterization of glycosylation by MS analysis.