Pathophysiology of Aortic Stenosis and Mitral Regurgitation

Aortic stenosis: a review on acquired pathogenesis and ominous combination with diabetes mellitus

BACKGROUND

Aortic stenosis (AS) is a progressive disease, with no pharmacological treatment. The prevalence of diabetes mellitus (DM) among AS patients is higher than in the general population. DM significantly increases the risk of AS development and progression from mild to severe. The interplay between AS and DM's mechanism is not entirely known yet.

MAIN BODY

The increased accumulation of advanced glycation end products (AGEs) was linked to increased valvular oxidative stress, inflammation, expression of coagulation factors, and signs of calcification, according to an analysis of aortic stenotic valves. It is interesting to note that in diabetic AS patients, valvular inflammation did not correlate with serum glucose levels but rather only with long-term glycemic management markers like glycated haemoglobin and fructosamine. Transcatheter aortic valve replacement, which has been shown to be safer than surgical aortic valve replacement, is advantageous for AS patients who also have concurrent diabetes. Additionally, novel anti-diabetic medications have been proposed to lower the risk of AS development in DM patients, including sodium-glucose cotransporter-2 inhibitors and glucagon-like peptide-1 receptor agonist that target reduction of AGEs-mediated oxidative stress.

CONCLUSIONS

There are little data on the effects of hyperglycemia on valvular calcification, but understanding the interactions between them is essential to develop a successful treatment strategy to stop or at least slow the progression of AS in DM patients. There is a link among AS and DM and that DM negatively impacts the quality of life and longevity of AS patients. The sole successful treatment, despite ongoing efforts to find new therapeutic modalities, involves aortic valve replacement. More research is required to find methods that can slow the advancement of these conditions, enhancing the prognosis and course of people with AS and DM.

Additive effects of mitral regurgitation on left ventricular strain in essential hypertensive patients as evaluated by cardiac magnetic resonance feature tracking

Objectives

Hypertension is one of the leading risk factors for cardiovascular disease. Mitral regurgitation (MR) is a heart valve disease commonly seen in hypertensive cases. This study aims to assess the effect of MR on left ventricle (LV) strain impairment among essential hypertensive cases and determine factors that independently impact the global peak strain of the LV.

Materials and methods

We enrolled 184 essential hypertensive patients, of which 53 were patients with MR [HTN (MR +) group] and 131 were without MR [HTN (MR−) group]. Another group of 61 age-and gender-matched controls was also included in the study. All participants had received cardiac magnetic resonance examination. The HTN (MR +) group was classified into three subsets based on regurgitation fraction, comprising mild MR (n = 22), moderate MR (n = 19), and severe MR (n = 12). We compared the LV function and strain parameters across different groups. Moreover, we performed multivariate linear regression to determine the independent factors affecting LV global radial peak strain (GRS), circumferential peak strain (GCS), and global longitudinal peak strain (GLS).

Results

HTN (MR−) cases exhibited markedly impaired GLS and peak diastolic strain rate (PDSR) but preserved LV ejection fraction (LVEF) compared to the controls. However, HTN (MR +) patients showed a decrease in LVEF and further deteriorated GRS, GCS, GLS, PDSR, and the peak systolic strain rate (PSSR) compared to the HTN (MR−) group and controls. With increasing degrees of regurgitation, the LV strain parameters were gradually reduced in HTN (MR +) patients. Even the mild MR group showed impaired GCS, GLS, PDSR, and PSSR compared to the HTN (MR−) group. Multiple regression analyses indicated that the degree of regurgitation was independently associated with GRS (β = -0.348), GCS (β = -0.339), and GLS (β = -0.344) in HTN (MR +) patients.

Conclusion

GLS was significantly impaired in HTN (MR−) patients. MR may further exacerbate the deterioration of LV strain among essential hypertensive cases. Besides, the degree of regurgitation was independently correlated with GRS, GCS, and GLS in HTN (MR +) patients.

Enduring Reactive Oxygen Species Emission Causes Aberrant Protein S-Glutathionylation Transitioning Human Aortic Valve Cells from a Sclerotic to a Stenotic Phenotype

Aims: During calcific aortic valve stenosis (CAVS) progression, oxidative stress and endothelial dysfunction mark the initial pathogenic steps with a parallel dysregulation of the antioxidant systems. Here, we tested whether oxidation-induced protein S-glutathionylation (P-SSG) accounts for a phenotypic switch in human aortic valvular tissue, eventually leading to calcium deposition. Next, we tested whether countering this reactive oxygen species (ROS) surge would prevent these perturbations. Results: We employed state-of-the-art technologies, such as electron paramagnetic resonance (EPR), liquid chromatography-tandem mass spectrometry, imaging flow-cytometry, and live-cell imaging on human excised aortic valves and primary valve endothelial cells (VECs). We observed that a net rise in EPR-detected ROS emission marked the transition from fibrotic to calcific in human CAVS specimens, coupled to a progressive increment in P-SSG deposition. In human VECs (hVECs), treatment with 2-acetylamino-3-[4-(2-acetylamino-2-carboxyethylsulfanylthiocarbonylamino)phenylthiocarbamoylsulfanyl]propionic acid triggered highly oxidizing conditions prompting P-SSG accumulation, damaging mitochondria, and inducing endothelial nitric oxide synthase uncoupling. All the events conjured up in morphing these cells from their native endothelial phenotype into a damaged calcification-inducing one. As proof of principle, the use of the antioxidant N-acetyl-L-cysteine prevented these alterations. Innovation: Borne as a compensatory system to face excessive oxidative burden, with time, P-SSG contributes to the morphing of hVECs from their innate phenotype into a damaged one, paving the way to calcium deposition. Conclusion: Our data suggest that, in the human aortic valve, unremitted ROS emission along with a P-SSG build-up occurs and accounts, at least in part, for the morphological/functional changes leading to CAVS. Antioxid. Redox Signal. 37, 1051-1071.

First quantitative dosages: Strong correlations between non-5-HT2Rs serotonin receptors on normal human heart valves

Objectives

Although critical in animal and human development and pathology, a measurement of the quantitative expression of 5-HTR serotonin receptors on animal or human valvular tissues has never been performed.

Methods

Quantification of the most frequent 5-HTRs reported as being present in human peripheral tissue was performed using radiolabeled agonists/antagonists. A membrane protein extract from normal human valves (aortic/mitral/tricuspid and some pulmonary) and associated diseased left myocardium, all unusable in clinics, were obtained from the Homograft bank.

Results

We analyzed 5-HT1AR/5-HT1B/DR/5-HT2AR/5-HT2BR/5-HT 2CR/5-HT4R/5-HT7R from 28 hearts. We confirmed the presence of tissue and measured the quantitative content for respective proteins in femtomol/mg of protein extracts: for 5-HT2AR (35.9+/−0.7), 5-HT2BR (28.8+/−1.3) but also a newly observed and robust expression for 5-HT4R (38+/−4.2). We identified one, 5-HT1ARs (4.9+/−0.3), and the possible expression, but at a very low level, of previously reported 5-HT1B/DRs (1.3+/−0.5) as well as the new 5-HT7Rs (3.5+/0.1) and 5-HT2CRs (1.2+/−0.1). Interestingly, by using univariate analysis, we were able to observe many correlations between the different 5-HTR levels of expression especially between 5-HT1AR/5-HT1B/DR and also between 5-HT4R/5-HT7R, but none were observed between 5-HT2AR and 5-HT2BR. Using multivariate analyses for a specific 5-HTR level of expression, after adjustment for implantation sites and other 5-HTRs, we found that 5-HT1AR was correlated with 5-HT1B/DR;5-HT4R with 5-HT7R and 5-HT1AR;5-HT2BR with 5-HT2AR only. For 5-HT2C, no correlation was observed.

Conclusion

5-HT2AR/5-HT2BR and 5-HT4R were all observed to have a high and equal level of expression on human valves, but that of 5-HT1AR was more limited. Since these non-5-HT2Rs are coupled with different G-proteins, with specific signaling, theoretically they may control the main 5-HT2R signaling (i.e., PLC/DAG-PKC-ERK/Ras/Src signaling) involved in valvular fibrosis and degeneration.

Macrophages in the heart: Active players or simple bystanders?

Today, more and more studies focus on the processes in which macrophages are involved. These discoveries provide new perspectives on the cellular mechanisms that regulate the physiological functions of the healthy heart. Moreover, they offer a deeper knowledge of the pathologic processes underlying the onset and the evolution of specific cardiac impairment. The heterogeneous population of macrophages within the heart can be divided by origin, expression profile, and function. The pool of cardiac macrophages includes at least two distinct subsets with different ontogeny. The first one has an embryonic origin, deriving from the yolk sac and the fetal liver, while the other macrophage subset results from the postnatal recruitment of monocytes produced in the bone marrow. This review will focus on new phenotypes and functions of cardiac macrophages that have been identified in the last years and that need to be deeply studied to unveil new potential therapies aimed at treating cardiac diseases.

Sex-Specific Cell Types and Molecular Pathways Indicate Fibro-Calcific Aortic Valve Stenosis

Background

Aortic stenosis (AS) is the most common valve disorder characterized by fibro-calcific remodeling of leaflets. Recent evidence indicated that there is a sex-related difference in AS development and progression. Fibrotic remodeling is peculiar in women’s aortic valves, while men’s leaflets are more calcified. Our study aimed to assess aortic valve fibrosis (AVF) in a severe AS cohort using non-invasive diagnostic tools and determine whether sex-specific pathological pathways and cell types are associated with severe AS.

Materials and Methods

We have included 28 men and 28 women matched for age with severe AS who underwent echocardiography and cardiac contrast-enhanced computed tomography (CT) before intervention. The calcium and fibrosis volumes were assessed and quantified using the ImageJ thresholding method, indexed calcium and fibrosis volume were calculated by dividing the volume by the aortic annular area. For a deeper understanding of molecular mechanisms characterizing AS disorder, differentially expressed genes and functional inferences between women and men’s aortic valves were carried out on a publicly available microarray-based gene expression dataset (GSE102249). Cell types enrichment analysis in stenotic aortic valve tissues was used to reconstruct the sex-specific cellular composition of stenotic aortic valves.

Results

In agreement with the literature, our CT quantifications showed that women had significantly lower aortic valve calcium content compared to men, while fibrotic tissue composition was significantly higher in women than men. The expression profiles of human stenotic aortic valves confirm sex-dependent processes. Pro-fibrotic processes were prevalent in women, while pro-inflammatory ones, linked to the immune response system, were enhanced in men. Cell-type enrichment analysis showed that mesenchymal cells were over-represented in AS valves of women, whereas signatures for monocytes, macrophages, T and B cells were enriched men ones.

Conclusions

Our data provide the basis that the fibro-calcific process of the aortic valve is sex-specific, both at gene expression and cell type level. The quantification of aortic valve fibrosis by CT could make it possible to perform population-based studies and non-invasive assessment of novel therapies to reduce or halt sex-related calcific aortic valve stenosis (CAVS) progression, acting in an optimal window of opportunity early in the course of the disease.

Prioritization of Candidate Biomarkers for Degenerative Aortic Stenosis through a Systems Biology-Based In-Silico Approach

Degenerative aortic stenosis is the most common valve disease in the elderly and is usually confirmed at an advanced stage when the only treatment is surgery. This work is focused on the study of previously defined biomarkers through systems biology and artificial neuronal networks to understand their potential role within aortic stenosis. The goal was generating a molecular panel of biomarkers to ensure an accurate diagnosis, risk stratification, and follow-up of aortic stenosis patients. We used in silico studies to combine and re-analyze the results of our previous studies and, with information from multiple databases, established a mathematical model. After this, we prioritized two proteins related to endoplasmic reticulum stress, thrombospondin-1 and endoplasmin, which have not been previously validated as markers for aortic stenosis, and analyzed them in a cell model and in plasma from human subjects. Large-scale bioinformatics tools allow us to extract the most significant results after using high throughput analytical techniques. Our results could help to prevent the development of aortic stenosis and open the possibility of a future strategy based on more specific therapies.

Purinergic Receptor P2Y2 Stimulation Averts Aortic Valve Interstitial Cell Calcification and Myofibroblastic Activation

Rationale—Calcific aortic valve stenosis (CAVS) is a pathological condition of the aortic valve with a prevalence of 3% in the general population. It is characterized by massive rearrangement of the extracellular matrix, mostly due to the accumulation of fibro-calcific deposits driven by valve interstitial cells (VIC), and no pharmacological treatment is currently available. The aim of this study was to evaluate the effects of P2Y2 receptor (P2RY2) activation on fibro-calcific remodeling of CAVS. Methods—We employed human primary VICs isolated from CAVS leaflets treated with 2-thiouridine-5′-triphosphate (2ThioUTP, 10 µM), an agonist of P2RY2. The calcification was induced by inorganic phosphate (2 mM) and ascorbic acid (50 µg/mL) for 7 or 14 days, while the 2ThioUTP was administered starting from the seventh day. 2ThioUTP was chronically administered for 5 days to evaluate myofibroblastic activation. Results—P2RY2 activation, under continuous or interrupted pro-calcific stimuli, led to a significant inhibition of VIC calcification potential (p < 0.01). Moreover, 2ThioUTP treatment was able to significantly reduce pro-fibrotic gene expression (p < 0.05), as well as that of protein α-smooth muscle actin (p = 0.004). Conclusions—Our data suggest that P2RY2 activation should be further investigated as a pharmacological target for the prevention of CAVS progression, acting on both calcification and myofibroblastic activation.

Aggravation of functional mitral regurgitation on left ventricle stiffness in type 2 diabetes mellitus patients evaluated by CMR tissue tracking

BACKGROUND

Functional mitral regurgitation (FMR) is one of the most common heart valve diseases in diabetes and may increase left ventricular (LV) preload and aggravate myocardial stiffness. This study aimed to investigate the aggravation of FMR on the deterioration of LV strain in type 2 diabetes mellitus (T2DM) patients and explore the independent indicators of LV peak strain (PS).

MATERIALS AND METHODS

In total, 157 T2DM patients (59 patients with and 98 without FMR) and 52 age- and sex-matched healthy control volunteers were included and underwent cardiac magnetic resonance examination. T2DM with FMR patients were divided into T2DM patients with mild (n = 21), moderate (n = 19) and severe (n = 19) regurgitation. LV function and global strain parameters were compared among groups. Multivariate analysis was used to identify the independent indicators of LV PS.

RESULTS

The T2DM with FMR had lower LV strain parameters in radial, circumferential and longitudinal direction than both the normal and the T2DM without FMR (all P < 0.05). The mild had mainly decreased peak diastolic strain rate (PDSR) compared to the normal. The moderate had decreased peak systolic strain rate (PSSR) compared to the normal and PDSR compared to the mild and the normal. The severe FMR group had decreased PDSR and PSSR compared to the mild and the normal (all P < 0.05). Multiple linear regression showed that the regurgitation degree was independent associated with radial (β = - 0.272), circumferential (β = - 0.412) and longitudinal (β = - 0.347) PS; the months with diabetes was independently associated with radial (β = - 0.299) and longitudinal (β = - 0.347) PS in T2DM with FMR.

CONCLUSION

FMR may aggravate the deterioration of LV stiffness in T2DM patients, resulting in decline of LV strain and function. The regurgitation degree and months with diabetes were independently correlated with LV global PS in T2DM with FMR.

Combined Mitral and Aortic Valve Surgery: 17 Years' Experience in a Single Center

Background and objective:

It is not uncommon that patients requiring valve surgery have several simultaneous valvular dysfunctions. Combined aortic and mitral valve surgery is the most common form of double-valve surgery. The aim of this study was to analyze and present the outcomes of simultaneous aortic and mitral valve surgery in a single center in a real-life setting.

Methods:

The study population consisted of 150 patients operated in the Kuopio University Hospital from 2004 to 2020. All patients undergoing concomitant mitral and aortic valve surgery were included. Four groups were formed based on either the etiology or pathophysiology of the valvular dysfunction. The most common combination was mitral regurgitation with aortic regurgitation (n = 72, 48%), followed by mitral regurgitation with aortic stenosis (n = 37, 25%), endocarditis (n = 29, 19%), and mitral stenosis with aortic regurgitation or stenosis (n = 12, 8%). Concomitant coronary artery revascularization was performed in 37 (25%) patients and tricuspid valve repair in 26 (17%) patients.

Results:

Operative mortality was 2% and 30-day mortality was 7%. Overall survival was 86%, 78%, and 61% in 3, 5, and 10 years, respectively. Patients with endocarditis were significantly more morbid, and more often than other patients had to undergo an emergency operation. There were no significant differences between the groups in terms of early and late survival. In the overall cohort, the EuroSCORE II value, increased pulmonary artery pressure, decreased glomerular filtration, and length of the operation displayed a negative correlation with survival.

Conclusions:

Despite the challenging nature of multivalvular heart disease, surgery is a safe method of treatment with good short- and long-term outcomes.

Current Evidence and Future Perspectives on Pharmacological Treatment of Calcific Aortic Valve Stenosis

Calcific aortic valve stenosis (CAVS), the most common heart valve disease, is characterized by the slow progressive fibro-calcific remodeling of the valve leaflets, leading to progressive obstruction to the blood flow. CAVS is an increasing health care burden and the development of an effective medical treatment is a major medical need. To date, no effective pharmacological therapies have proven to halt or delay its progression to the severe symptomatic stage and aortic valve replacement represents the only available option to improve clinical outcomes and to increase survival. In the present report, the current knowledge and latest advances in the medical management of patients with CAVS are summarized, placing emphasis on lipid-lowering agents, vasoactive drugs, and anti-calcific treatments. In addition, novel potential therapeutic targets recently identified and currently under investigation are reported.

Sex-specific differences in age-related aortic valve calcium load: A systematic review and meta-analysis

Aging of the aortic valve, characterized by leaflet thickening and loss of extensibility, leads to progressive changes in valve function. These age-related mechanisms have not been evaluated yet in sex-specific calcific aortic valve stenosis (CAVS) onset and progression. Recent studies reported the association between high aortic valve calcification (AVC) load and male gender in patients with CAVS while women present faster progression than men. To evaluate these age- and sex-specific differences, we performed a systematic review and meta-analysis with meta-regression. A systematic search related to AVC measured by computed tomography and gender-specific differences was conducted according to PRISMA guidelines. Seven studies, enrolling 1859 men and 1055 women, were included in the quantitative synthesis. We found a significant difference between men and women both in AVC load and density. AVC load mean difference (MD), between men and women, was 1131 ± 243 AU (p < 0.0001; I²: 96.5 %, p < 0.001), while AVC density MD was 159 ± 20 AU/cm² (p < 0.0001) without heterogeneity among the studies (I²: 23.5, p = 0.3). Meta-regression analyses showed that AVC load MD positively correlated with age and other cardiovascular risk factors such as diabetes, hypertension, and coronary artery disease presence. Our meta-analysis shows a significant association of incremental AVC load with male gender, regardless of the individual anatomical characteristics and the cardiovascular risk factors. Further studies are needed: i) to clarify if there are different sex-related pathophysiological processes driving the development and the progression of age-related CAVS, and ii) to determine if a sex-specific therapeutic strategy should be applied for CAVS treatment and/or prevention.

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.

Endothelial-to-Mesenchymal Transition in Calcific Aortic Valve Disease

Calcific aortic valve disease (CAVD) represents a significant threat to cardiovascular health worldwide, and the incidence of this sclerocalcific valve disease has rapidly increased along with a rise in life expectancy. Compelling evidence has suggested that CAVD is an actively and finely regulated pathophysiological process even though it has been referred to as "degenerative" for decades. A striking similarity has been noted in the etiopathogenesis between CAVD and atherosclerosis, a classical proliferative sclerotic vascular disease.1 Nevertheless, pharmaceutical trials that attempted to target inflammation and dyslipidemia have produced disappointing results in CAVD. While senescence is a well-documented risk factor, the sophisticated regulatory networks have not been adequately explored underlying the aberrant calcification and osteogenesis in CAVD. Valvular endothelial cells (VECs), a type of resident effector cells in aortic leaflets, are crucial in maintaining valvular integrity and homeostasis, and dysfunctional VECs are a major contributor to disease initiation and progression. Accumulating evidence suggests that VECs undergo a phenotypic and functional transition to mesenchymal or fibroblast-like cells in CAVD, a process known as the endothelial-to-mesenchymal transition (EndMT) process. The relevance of this transition in CAVD has recently drawn great interest due to its importance in both valve genesis at an embryonic stage and CAVD development at an adult stage. Hence EndMT might be a valuable diagnostic and therapeutic target for disease prevention and treatment. This mini-review summarized the relevant literature that delineates the EndMT process and the underlying regulatory networks involved in CAVD.

Management of valvulopathies with acute severe heart failure and cardiogenic shock

Cardiogenic shock is a critical clinical situation, requiring rapid diagnosis, aetiological assessment and immediate initiation of therapy. In industrialized countries, aortic stenosis is the most frequent left-sided valvulopathy, followed by mitral regurgitation, aortic regurgitation and mitral stenosis. Severe valvulopathies leading to cardiogenic shock are not rare conditions, but few data are available on their optimal management. Therapeutic options for such critical conditions include inotropic agents, mechanical support (when feasible) and rapid valvular intervention. Although surgery remains the gold-standard treatment for severe valvular disease, mortality is frequently prohibitive in the setting of cardiogenic shock, necessitating consideration of alternative therapies. Percutaneous management of valvulopathies has emerged as an alternative treatment for patients deemed at high surgical risk in a stable condition. Although few published data are available, catheter-based interventions may be feasible in the cardiogenic shock setting. This review offers an overview of different valvulopathies in the cardiogenic shock setting, and summarizes the different therapeutic options currently available in such critical situations.

Mechanical strain induces a pro-fibrotic phenotype in human mitral valvular interstitial cells through RhoC/ROCK/MRTF-A and Erk1/2 signaling pathways

The mitral valve is a complex multilayered structure populated by fibroblast-like cells, valvular interstitial cells (VIC) which are embedded in an extracellular matrix (ECM) scaffold and are submitted to the mechanical deformations affecting valve at each heartbeat, for an average of 40 million times per year. Myxomatous mitral valve (MMV) is the most frequent heart valve disease characterized by disruption of several valvular structures due to alterations of their ECM preventing the complete closure of the valve resulting in symptoms of prolapse and regurgitation. VIC and their ECM exhibit reciprocal dynamic processes between the mechanical signals issued from the ECM and the modulation of VIC phenotype responsible for ECM homeostasis of the valve. Abnormal perception and responsiveness of VIC to mechanical stress may induce an inappropriate adaptative remodeling of the valve progressively leading to MMV. To investigate the response of human VIC to mechanical strain and identify the molecular mechanisms of mechano-transduction in these cells, a cyclic equibiaxial elongation of 14% at the cardiac frequency of 1.16 Hz was applied to VIC by using a Flexercell-4000 T™ apparatus for increasing time (from 1 h to 8 h). We showed that cyclic stretch induces an early (1 h) and transient over-expression of TGFβ2 and αSMA. CTGF, a profibrotic growth factor promoting the synthesis of ECM components, was strongly induced after 1 and 2 h of stretching and still upregulated at 8 h. The mechanical stress-induced CTGF up-regulation was dependent on RhoC, but not RhoA, as demonstrated by siRNA-mediated silencing approaches, and further supported by evidencing RhoC activation upon cell stretching and suppression of cell response by pharmacological inhibition of the effector ROCK1/2. It was also dependent on the MEK/Erk1/2 pathway which was activated by mechanical stress independently of RhoC and ROCK. Finally, mechanical stretching induced the nuclear translocation of myocardin related transcription factor-A (MRTF-A) which forms a transcriptional complex with SRF to promote the expression of target genes, notably CTGF. Treatment of stretched cultures with inhibitors of the identified pathways (ROCK1/2, MEK/Erk1/2, MRTF-A translocation) blocked CTGF overexpression and abrogated the increased MRTF-A nuclear translocation. CTGF is up-regulated in many pathological processes involving mechanically challenged organs, promotes ECM accumulation and is considered as a hallmark of fibrotic diseases. Pharmacological targeting of MRTF-A by newly developed inhibitors may represent a relevant therapy for MMV.

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.

Unchain My Heart: Integrins at the Basis of iPSC Cardiomyocyte Differentiation

The cellular response to the extracellular matrix (ECM) microenvironment mediated by integrin adhesion is of fundamental importance, in both developmental and pathological processes. In particular, mechanotransduction is of growing importance in groundbreaking cellular models such as induced pluripotent stem cells (iPSC), since this process may strongly influence cell fate and, thus, augment the precision of differentiation into specific cell types, e.g., cardiomyocytes. The decryption of the cellular machinery starting from ECM sensing to iPSC differentiation calls for new in vitro methods. Conveniently, engineered biomaterials activating controlled integrin-mediated responses through chemical, physical, and geometrical designs are key to resolving this issue and could foster clinical translation of optimized iPSC-based technology. This review introduces the main integrin-dependent mechanisms and signalling pathways involved in mechanotransduction. Special consideration is given to the integrin-iPSC linkage signalling chain in the cardiovascular field, focusing on biomaterial-based in vitro models to evaluate the relevance of this process in iPSC differentiation into cardiomyocytes.