Endothelial to mesenchymal transition in the cardiovascular system

Beyond VICs: Shedding light on the overlooked VECs in calcific aortic valve disease

Calcific aortic valve disease (CAVD) is prevalent in developed nations and has emerged as a pressing global public health concern due to population aging. The precise etiology of this disease remains uncertain, and recent research has primarily focused on examining the role of valvular interstitial cells (VICs) in the development of CAVD. The predominant treatment options currently available involve open surgery and minimally invasive interventional surgery, with no efficacious pharmacological treatment. This article seeks to provide a comprehensive understanding of valvular endothelial cells (VECs) from the aspects of valvular endothelium-derived nitric oxide (NO), valvular endothelial mechanotransduction, valvular endothelial injury, valvular endothelial-mesenchymal transition (EndMT), and valvular neovascularization, which have received less attention, and aims to establish their role and interaction with VICs in CAVD. The ultimate goal is to provide new perspectives for the investigation of non-invasive treatment options for this disease.

Anti-IL-17 Inhibits PINK1/Parkin Autophagy and M1 Macrophage Polarization in Rheumatic Heart Disease

Rheumatic heart disease (RHD) is an important and preventable cause of cardiovascular death and disability, but the lack of clarity about its exact mechanisms makes it more difficult to find alternative methods or prevention and treatment. We previously demonstrated that increased IL-17 expression plays a crucial role in the development of RHD-related valvular inflammatory injury. Macrophage autophagy/polarization may be a pro-survival strategy in the initiation and resolution of the inflammatory process. This study investigated the mechanism by which IL-17 regulates autophagy/polarization activation in macrophages. A RHD rat model was generated, and the effects of anti-IL-17 and 3-methyladenine (3-MA) were analyzed. The molecular mechanisms underlying IL-17-induced macrophage autophagy/polarization were investigated via in vitro experiments. In our established RHD rat model, the activation of the macrophage PINK1/Parkin autophagic pathway in valve tissue was accompanied by M1 macrophage infiltration, and anti-IL-17 treatment inhibited autophagy and reversed macrophage inflammatory infiltration, thereby attenuating endothelial-mesenchymal transition (EndMT) in the valve tissue. The efficacy of 3-MA treatment was similar to that of anti-IL-17 treatment. Furthermore, in THP-1 cells, the pharmacological promotion of autophagy by IL-17 induced M1-type polarization, whereas the inhibition of autophagy by 3-MA reversed this process. Mechanistically, silencing PINK1 in THP-1 blocked autophagic flux. Moreover, IL-17-induced M1-polarized macrophages promoted EndMT in HUVECs. This study revealed that IL-17 plays an important role in EndMT in RHD via the PINK1/Parkin autophagic pathway and macrophage polarization, providing a potential therapeutic target.

The isoproterenol-induced myocardial fibrosis: A biochemical and histological investigation

The isoproterenol (ISO)-induced myocardial fibrosis is considered a reliable and repeatable experimental model characterized by a relatively low mortality rate. Although is well-known that ISO stimulates the β1 adrenergic receptors at the myocardial level, a high degree of heterogeneity emerges around the doses and duration of the treatment generating unclear results. Therefore, we propose to gain insights into the progression of ISO-induced myocardial fibrosis, in order to critically analyze and optimize the experimental model. Male Wistar rats (12-14-week-old) were submitted to subcutaneous injection of ISO, in particular, two doses were selected: the commonly used dose of 5 mg/kg and a lower dose of 1 mg/kg, administered for 3 and 6 days. Biochemical and histological examinations were conducted either immediately after the last administration or after a recovering period of 7 or 14 days from the initial administration. Noteworthy, from our investigation emerged that even the lower dose of ISO was able to induce the maximal biochemical and histological alterations, suggesting that lower doses should be considered to control the progression of the damage more precisely and to identify a prodromic phase in which intervention with pharmacological or nutraceutical tools can be effectively attempted.

Analysis of immunoinfiltration and EndoMT based on TGF-β signaling pathway-related genes in acute myocardial infarction

Acute myocardial infarction (AMI), a critical manifestation of coronary heart disease, presents a complex and not entirely understood etiology. This study investigates the potential role of immune infiltration and endothelial-mesenchymal transition (EndoMT) in AMI pathogenesis. We conducted an analysis of the GSE24519 and MSigDB datasets to identify differentially expressed genes associated with the TGF-β signaling pathway (DE-TSRGs) and carried out a functional enrichment analysis. Additionally, we evaluated immune infiltration in AMI and its possible link to myocardial fibrosis. Key genes were identified using machine learning and LASSO logistic regression. The expression of MEOX1 in the ventricular muscles and endothelial cells of Sprague-Dawley rats was assessed through RT-qPCR, immunohistochemical and immunofluorescence assays, and the effect of MEOX1 overexpression on EndoMT was investigated. Our study identified five DE-TSRGs, among which MEOX1, SMURF1, and SPTBN1 exhibited the most significant associations with AMI. Notably, we detected substantial immune infiltration in AMI specimens, with a marked increase in neutrophils and macrophages. MEOX1 demonstrated consistent expression patterns in rat ventricular muscle tissue and endothelial cells, and its overexpression induced EndoMT. Our findings suggest that the TGF-β signaling pathway may contribute to AMI progression by activating the immune response. MEOX1, linked to the TGF-β signaling pathway, appears to facilitate myocardial fibrosis via EndoMT following AMI. These novel insights into the mechanisms of AMI pathogenesis could offer promising therapeutic targets for intervention.

RNA-Binding Proteins Regulate Post-Transcriptional Responses to TGF-β to Coordinate Function and Mesenchymal Activation of Murine Endothelial Cells

BACKGROUND

Endothelial cells (ECs) are primed to respond to various signaling cues. For example, TGF (transforming growth factor)-β has major effects on EC function and phenotype by driving ECs towards a more mesenchymal state (ie, triggering endothelial to mesenchymal activation), a dynamic process associated with cardiovascular diseases. Although transcriptional regulation triggered by TGF-β in ECs is well characterized, post-transcriptional regulatory mechanisms induced by TGF-β remain largely unknown.

METHODS

Using RNA interactome capture, we identified global TGF-β driven changes in RNA-binding proteins in ECs. We investigated specific changes in the RNA-binding patterns of hnRNP H1 (heterogeneous nuclear ribonucleoprotein H1) and Csde1 (cold shock domain containing E1) using RNA immunoprecipitation and overlapped this with RNA-sequencing data after knockdown of either protein for functional insight. Using a modified proximity ligation assay, we visualized the specific interactions between hnRNP H1 and Csde1 and target RNAs in situ both in vitro and in mouse heart sections.

RESULTS

Characterization of TGF-β-regulated RBPs (RNA-binding proteins) revealed hnRNP H1 and Csde1 as key regulators of the cellular response to TGF-β at the post-transcriptional level, with loss of either protein-promoting mesenchymal activation in ECs. We found that TGF-β drives an increase in binding of hnRNP H1 to its target RNAs, offsetting mesenchymal activation, but a decrease in Csde1 RNA-binding, facilitating this process. Both, hnRNP H1 and Csde1, dynamically bind and regulate specific subsets of mRNAs related to mesenchymal activation and endothelial function.

CONCLUSIONS

Together, we show that RBPs play a key role in the endothelial response to TGF-β stimulation at the post-transcriptional level and that the RBPs hnRNP H1 and Csde1 serve to maintain EC function and counteract mesenchymal activation. We propose that TGF-β profoundly modifies RNA-protein interaction entailing feedback and feed-forward control at the post-transcriptional level, to fine-tune mesenchymal activation in ECs.

A gene-based association test of interactions for maternal-fetal genotypes identifies genes associated with nonsyndromic congenital heart defects

The risk of congenital heart defects (CHDs) may be influenced by maternal genes, fetal genes, and their interactions. Existing methods commonly test the effects of maternal and fetal variants one-at-a-time and may have reduced statistical power to detect genetic variants with low minor allele frequencies. In this article, we propose a gene-based association test of interactions for maternal-fetal genotypes (GATI-MFG) using a case-mother and control-mother design. GATI-MFG can integrate the effects of multiple variants within a gene or genomic region and evaluate the joint effect of maternal and fetal genotypes while allowing for their interactions. In simulation studies, GATI-MFG had improved statistical power over alternative methods, such as the single-variant test and functional data analysis (FDA) under various disease scenarios. We further applied GATI-MFG to a two-phase genome-wide association study of CHDs for the testing of both common variants and rare variants using 947 CHD case mother-infant pairs and 1306 control mother-infant pairs from the National Birth Defects Prevention Study (NBDPS). After Bonferroni adjustment for 23,035 genes, two genes on chromosome 17, TMEM107 (p = 1.64e-06) and CTC1 (p = 2.0e-06), were identified for significant association with CHD in common variants analysis. Gene TMEM107 regulates ciliogenesis and ciliary protein composition and was found to be associated with heterotaxy. Gene CTC1 plays an essential role in protecting telomeres from degradation, which was suggested to be associated with cardiogenesis. Overall, GATI-MFG outperformed the single-variant test and FDA in the simulations, and the results of application to NBDPS samples are consistent with existing literature supporting the association of TMEM107 and CTC1 with CHDs.

Endothelial-to-mesenchymal transition: New insights into vascular calcification

With the continuous progress of atherosclerosis research, the significant pathological change of it--vascular calcification (VC), gains increasing attention. In recent years, numerous studies have demonstrated that it is an independent predictor of death risk of cardiovascular disease, and it has a strong correlation with poor clinical prognosis. As the world's population continues to age, the occurrence of VC is expected to reach its highest point in the near future. Therefore, it is essential to investigate ways to prevent or even reverse this process for clinical purposes. Endothelial-to-mesenchymal transition (EndMT) describes the progressive differentiation of endothelial cells into mesenchymal stem cells (MSCs) under various stimuli and acquisition of pluripotent cell characteristics. More and more studies show that EndMT plays a vital role in various cardiovascular diseases, including atherosclerosis, vascular calcification and heart valvular disease. EndMT is also involved in the formation and progression of VC. This review vividly describes the history, characteristics of EndMT and how it affects the endothelial cell process, then focuses on the relationship between vascular endothelium, EndMT, amino acid metabolism, and vascular calcification. Finally, it overviews the signal pathway of EndMT and drugs targeting EndMT, hoping to provide new ideas and a theoretical basis for studying potential therapeutic targets of VC.

Hydrogen Sulfide Modulates Endothelial-Mesenchymal Transition in Heart Failure

BACKGROUND

Hydrogen sulfide is a critical endogenous signaling molecule that exerts protective effects in the setting of heart failure. Cystathionine γ-lyase (CSE), 1 of 3 hydrogen-sulfide-producing enzyme, is predominantly localized in the vascular endothelium. The interaction between the endothelial CSE-hydrogen sulfide axis and endothelial-mesenchymal transition, an important pathological process contributing to the formation of fibrosis, has yet to be investigated.

METHODS

Endothelial-cell-specific CSE knockout and Endothelial cell-CSE overexpressing mice were subjected to transverse aortic constriction to induce heart failure with reduced ejection fraction. Cardiac function, vascular reactivity, and treadmill exercise capacity were measured to determine the severity of heart failure. Histological and gene expression analyses were performed to investigate changes in cardiac fibrosis and the activation of endothelial-mesenchymal transition.

RESULTS

Endothelial-cell-specific CSE knockout mice exhibited increased endothelial-mesenchymal transition and reduced nitric oxide bioavailability in the myocardium, which was associated with increased cardiac fibrosis, impaired cardiac and vascular function, and worsened exercise performance. In contrast, genetic overexpression of CSE in endothelial cells led to increased myocardial nitric oxide, decreased endothelial-mesenchymal transition and cardiac fibrosis, preserved cardiac and endothelial function, and improved exercise capacity.

CONCLUSIONS

Our data demonstrate that endothelial CSE modulates endothelial-mesenchymal transition and ameliorate the severity of pressure-overload-induced heart failure, in part, through nitric oxide-related mechanisms. These data further suggest that endothelium-derived hydrogen sulfide is a potential therapeutic for the treatment of heart failure with reduced ejection fraction.

Endothelial-cell-mediated mechanism of coronary microvascular dysfunction leading to heart failure with preserved ejection fraction

Although the prevalence of heart failure with preserved ejection fraction (HFpEF) is growing worldwide, its complex pathophysiology has yet to be fully elucidated, and multiple hypotheses have all failed to produce a viable target for therapeutic action or provide effective treatment. Cardiac remodeling has long been considered an important mechanism of HFpEF. Strong evidence has been reported over the past years that coronary microvascular dysfunction (CMD), manifesting as structural and functional abnormalities of coronary microvasculature, also contributes to the evolution of HFpEF. However, the mechanisms of CMD are still not well understood and need to be studied further. Coronary microvascular endothelial cells (CMECs) are one of the most abundant cell types in the heart by number and active players in cardiac physiology and pathology. CMECs are not only important cellular mediators of cardiac vascularization but also play an important role in disease pathophysiology by participating in the inception and progression of cardiac remodeling. CMECs are also actively involved in the pathogenesis of CMD. Numerous studies have confirmed that CMD is closely related to cardiac remodeling. ECs may serve a critical function in mediating the connection between CMD and HFpEF. It follows that CMECs participate in the mechanism of CMD leading to HFpEF. In this review article, we focus on the role of CMD in the pathogenesis of HFpEF resulting from cardiac remodeling and highlight the subsequent complexity of the EC-mediated correlation between CMD and HFpEF.

Effects of Physiological and Pathological Urea Concentrations on Human Microvascular Endothelial Cells

Urea is the uremic toxin accumulating with the highest concentration in the plasma of chronic kidney disease (CKD) patients, not being completely cleared by dialysis. Urea accumulation is reported to exert direct and indirect side effects on the gastrointestinal tract, kidneys, adipocytes, and cardiovascular system (CVS), although its pathogenicity is still questioned since studies evaluating its side effects lack homogeneity. Here, we investigated the effects of physiological and pathological urea concentrations on a human endothelial cell line from the microcirculation (Human Microvascular Endothelial Cells-1, HMEC-1). Urea (5 g/L) caused a reduction in the proliferation rate after 72 h of exposure and appeared to be a potential endothelial-to-mesenchymal transition (EndMT) stimulus. Moreover, urea induced actin filament rearrangement, a significant increase in matrix metalloproteinases 2 (MMP-2) expression in the medium, and a significant up- or down-regulation of other EndMT biomarkers (keratin, fibrillin-2, and collagen IV), as highlighted by differential proteomic analysis. Among proteins whose expression was found to be significantly dysregulated following exposure of HMEC-1 to urea, dimethylarginine dimethylaminohydrolase (DDAH) and vasorin turned out to be down-regulated. Both proteins have been directly linked to cardiovascular diseases (CVD) by in vitro and in vivo studies. Future experiments will be needed to deepen their role and investigate the signaling pathways in which they are involved to clarify the possible link between CKD and CVD.

The Endothelial Transcription Factor ERG Mediates a Differential Role in the Aneurysmatic Ascending Aorta with Bicuspid or Tricuspid Aorta Valve: A Preliminary Study

The pathobiology of ascending aorta aneurysms (AAA) onset and progression is not well understood and only partially characterized. AAA are also complicated in case of bicuspid aorta valve (BAV) anatomy. There is emerging evidence about the crucial role of endothelium-related pathways, which show in AAA an altered expression and function. Here, we examined the involvement of ERG-related pathways in the differential progression of disease in aortic tissues from patients having a BAV or tricuspid aorta valve (TAV) with or without AAA. Our findings identified ERG as a novel endothelial-specific regulator of TGF-β-SMAD, Notch, and NO pathways, by modulating a differential fibrotic or calcified AAA progression in BAV and TAV aortas. We provided evidence that calcification is correlated to different ERG expression (as gene and protein), which appears to be under control of Notch signaling. The latter, when increased, associated with an early calcification in aortas with BAV valve and aneurysmatic, was demonstrated to favor the progression versus severe complications, i.e., dissection or rupture. In TAV aneurysmatic aortas, ERG appeared to modulate fibrosis. Therefore, we proposed that ERG may represent a sensitive tissue biomarker to monitor AAA progression and a target to develop therapeutic strategies and influence surgical procedures.

A Systematic Review of Ebstein’s Anomaly with Left Ventricular Noncompaction

Traditional definitions of Ebstein’s anomaly (EA) and left ventricular noncompaction (LVNC), two rare congenital heart defects (CHDs), confine disease to either the right or left heart, respectively. Around 15–29% of patients with EA, which has a prevalence of 1 in 20,000 live births, commonly manifest with LVNC. While individual EA or LVNC literature is extensive, relatively little discussion is devoted to the joint appearance of EA and LVNC (EA/LVNC), which poses a higher risk of poor clinical outcomes. We queried PubMed, Medline, and Web of Science for all peer-reviewed publications from inception to February 2022 that discuss EA/LVNC and found 58 unique articles written in English. Here, we summarize and extrapolate commonalities in clinical and genetic understanding of EA/LVNC to date. We additionally postulate involvement of shared developmental pathways that may lead to this combined disease. Anatomical variation in EA/LVNC encompasses characteristics of both CHDs, including tricuspid valve displacement, right heart dilatation, and left ventricular trabeculation, and dictates clinical presentation in both age and severity. Disease treatment is non-specific, ranging from symptomatic management to invasive surgery. Apart from a few variant associations, mainly in sarcomeric genes MYH7 and TPM1, the genetic etiology and pathogenesis of EA/LVNC remain largely unknown.

Inhibition of β-catenin signaling attenuates arteriovenous fistula thickening in mice by suppressing myofibroblasts

Background

Arteriovenous fistula (AVF) is the most important vascular access for hemodialysis; however, preventive treatment to maintain the patency of AVFs has not been developed. In endothelium, β-catenin functions in both the intercellular adherens complex and signaling pathways that induce the transition of endothelial cells to myofibroblasts in response to mechanical stimuli. We hypothesize that mechanical disturbances in the AVF activate β-catenin signaling leading to the transition of endothelial cells to myofibroblasts, which cause AVF thickening. The present study aimed to test this hypothesis.

Methods

Chronic kidney disease in mice was induced by a 0.2% adenine diet. AVFs were created by aortocaval puncture. Human umbilical vein endothelial cells (HUVECs) were used in the cell experiments. A pressure-culture system was used to simulate mechanical disturbances of the AVF.

Results

Co-expression of CD31 and smooth muscle alpha-actin (αSMA), loss of cell–cell adhesions, and the expression of the myofibroblast marker, integrin subunit β6 (ITGB6), indicated transition to myofibroblasts in mouse AVF. Nuclear translocation of β-catenin, decreased axin2, and increased c-myc expression were also observed in the AVF, indicating activated β-catenin signaling. To confirm that β-catenin signaling contributes to AVF lesions, β-catenin signaling was inhibited with pyrvinium pamoate; β-catenin inhibition significantly attenuated AVF thickening and decreased myofibroblasts. In HUVECs, barometric pressure-induced nuclear localization of β-catenin and increased expression of the myofibroblast markers, αSMA and ITGB6. These changes were attenuated via pretreatment with β-catenin inhibition.

Conclusions

The results of this study indicate that mechanical disturbance in AVF activates β-catenin signaling to induce the transition of endothelial cells to myofibroblasts. This signaling cascade can be targeted to maintain AVF patency.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00436-1.

IL-1β in atherosclerotic vascular calcification: From bench to bedside

Atherosclerotic vascular calcification contributes to increased risk of death in patients with cardiovascular diseases. Assessing the type and severity of inflammation is crucial in the treatment of numerous cardiovascular conditions. IL-1β, a potent proinflammatory cytokine, plays diverse roles in the pathogenesis of atherosclerotic vascular calcification. Several large-scale, population cohort trials have shown that the incidence of cardiovascular events is clinically reduced by the administration of anti-IL-1β therapy. Anti-IL-1β therapy might reduce the incidence of cardiovascular events by affecting atherosclerotic vascular calcification, but the mechanism underlying this effect remains unclear. In this review, we summarize current knowledge on the role of IL-1β in atherosclerotic vascular calcification, and describe the latest results reported in clinical trials evaluating anti-IL-1β therapies for the treatment of cardiovascular diseases. This review will aid in improving current understanding of the pathophysiological roles of IL-1β and mechanisms underlying its activity.

A dual role of YAP in driving TGFβ-mediated endothelial-to-mesenchymal transition

Endothelial-to-mesenchymal transition (EndMT) is the biological process through which endothelial cells transdifferentiate into mesenchymal cells. During embryo development, EndMT regulates endocardial cushion formation via TGFβ/BMP signaling. In adults, EndMT is mainly activated during pathological conditions. Hence, it is necessary to characterize molecular regulators cooperating with TGFβ signaling in driving EndMT, to identify potential novel therapeutic targets to treat these pathologies. Here, we studied YAP, a transcriptional co-regulator involved in several biological processes, including epithelial-to-mesenchymal transition (EMT). As EndMT is the endothelial-specific form of EMT, and YAP (herein referring to YAP1) and TGFβ signaling cross-talk in other contexts, we hypothesized that YAP contributes to EndMT by modulating TGFβ signaling. We demonstrate that YAP is required to trigger TGFβ-induced EndMT response, specifically contributing to SMAD3-driven EndMT early gene transcription. We provide novel evidence that YAP acts as SMAD3 transcriptional co-factor and prevents GSK3β-mediated SMAD3 phosphorylation, thus protecting SMAD3 from degradation. YAP is therefore emerging as a possible candidate target to inhibit pathological TGFβ-induced EndMT at early stages.

Summary: A new crucial role for YAP as a co-activator of early pathological TGFβ-mediated endothelial-to-mesenchymal transition program and characterization of the underlying molecular mechanism.

Role of PI3K/Akt signaling pathway in cardiac fibrosis

Heart failure (HF) is considered as a severe health problem worldwide, while cardiac fibrosis is one of the main driving factors for the progress of HF. Cardiac fibrosis was characterized by changes in cardiomyocytes, cardiac fibroblasts, ratio of collagen (COL) I/III, and the excessive production and deposition of extracellular matrix (ECM), thus forming a scar tissue, which leads to pathological process of cardiac structural changes and systolic as well as diastolic dysfunction. Cardiac fibrosis is a common pathological change of many advanced cardiovascular diseases including ischemic heart disease, hypertension, and HF. Accumulated studies have proven that phosphoinositol-3 kinase (PI3K)/Akt signaling pathway is involved in regulating the occurrence, progression and pathological formation of cardiac fibrosis via regulating cell survival, apoptosis, growth, cardiac contractility and even the transcription of related genes through a series of molecules including mammalian target of rapamycin (mTOR), glycogen synthase kinase 3 (GSK-3), forkhead box proteins O1/3 (FoxO1/3), and nitric oxide synthase (NOS). Thus, the review focuses on the role of PI3K/Akt signaling pathway in the cardiac fibrosis. The information reviewed here should be significant in understanding the role of PI3K/Akt in cardiac fibrosis and contribute to the design of further studies related to PI3K/Akt and the cardiac fibrotic response, as well as sought to shed light on a potential treatment for cardiac fibrosis.

Endothelial to Mesenchymal Transition in the Cardiogenesis and Cardiovascular Diseases

Today, cardiovascular diseases remain a leading cause of morbidity and mortality worldwide. Endothelial to mesenchymal transition (EndMT) does not only play a major role in the course of development but also contributes to several cardiovascular diseases in adulthood. EndMT is characterized by down-regulation of the endothelial proteins and highly up-regulated fibrotic specific genes and extracellular matrix-forming proteins. EndMT is also a transforming growth factor-β-driven (TGF-β) process in which endothelial cells lose their endothelial characteristics and acquire a mesenchymal phenotype with expression of α-smooth muscle actin (α-SMA), fibroblast-specific protein 1, etc. EndMT is a vital process during cardiac development, thus disrupted EndMT gives rise to the congenital heart diseases, namely septal defects and valve abnormalities. In this review, we have discussed the main signaling pathways and mechanisms participating in the process of EndMT such as TGF-β and Bone morphogenetic protein (BMP), Wnt^#, and Notch signaling pathway and also studied the role of EndMT in physiological cardiovascular development and pathological conditions including myocardial infarction, pulmonary arterial hypertension, congenital heart defects, cardiac fibrosis, and atherosclerosis. As a perspective view, having a clear understanding of involving cellular and molecular mechanisms in EndMT and conducting Randomized controlled trials (RCTs) with a large number of samples for involving pharmacological agents may guide us into novel therapeutic approaches of congenital disorders and heart diseases.

Dasatinib induces endothelial-to-mesenchymal transition in human vascular-endothelial cells: counteracted by cotreatment with bosutinib

Adverse vascular events have become a serious clinical problem in chronic myeloid leukemia (CML) patients who receive certain BCR/ABL1 tyrosine kinase inhibitors (TKIs). Studies have shown that endothelial-to-mesenchymal transition (EndMT) can contribute to various vascular diseases. We investigated the effects of TKIs on the development of EndMT in human vascular-endothelial cells (VECs). Exposure of VECs to dasatinib, but not to other TKIs, produced a significant increase in the formation of spindle-shaped cells. This effect was accompanied by a significant increase in expression of the EndMT inducer transforming growth factor-β (TGF-β) and mesenchymal markers vimentin, smooth muscle alpha-actin, and fibronectin, as well as a significant decrease in expression of vascular-endothelial markers CD31 and VE-cadherin attributable at least in part to activation of ERK signaling. Inhibitors of TGF-β and ERK partially attenuated dasatinib-induced EndMT. Interestingly, bosutinib efficiently counteracted dasatinib-induced EndMT and attenuated dasatinib-induced phosphorylation of ERK. Taken together, these results show that dasatinib induces EndMT, which might contribute to the development of vascular toxicity, such as the pulmonary hypertension observed in CML patients receiving dasatinib. Bosutinib could play a distinct role in protecting VECs from EndMT.

Mechanisms of the Osteogenic Switch of Smooth Muscle Cells in Vascular Calcification: WNT Signaling, BMPs, Mechanotransduction, and EndMT

Characterized by the hardening of arteries, vascular calcification is the deposition of hydroxyapatite crystals in the arterial tissue. Calcification is now understood to be a cell-regulated process involving the phenotypic transition of vascular smooth muscle cells into osteoblast-like cells. There are various pathways of initiation and mechanisms behind vascular calcification, but this literature review highlights the wingless-related integration site (WNT) pathway, along with bone morphogenic proteins (BMPs) and mechanical strain. The process mirrors that of bone formation and remodeling, as an increase in mechanical stress causes osteogenesis. Observing the similarities between the two may aid in the development of a deeper understanding of calcification. Both are thought to be regulated by the WNT signaling cascade and bone morphogenetic protein signaling and can also be activated in response to stress. In a pro-calcific environment, integrins and cadherins of vascular smooth muscle cells respond to a mechanical stimulus, activating cellular signaling pathways, ultimately resulting in gene regulation that promotes calcification of the vascular extracellular matrix (ECM). The endothelium is also thought to contribute to vascular calcification via endothelial to mesenchymal transition, creating greater cell plasticity. Each of these factors contributes to calcification, leading to increased cardiovascular mortality in patients, especially those suffering from other conditions, such as diabetes and kidney failure. Developing a better understanding of the mechanisms behind calcification may lead to the development of a potential treatment in the future.

Vascular dysfunction in aged mice contributes to persistent lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease thought to result from impaired lung repair following injury and is strongly associated with aging. While vascular alterations have been associated with IPF previously, the contribution of lung vasculature during injury resolution and fibrosis is not well understood. To compare the role of endothelial cells (ECs) in resolving and non-resolving models of lung fibrosis, we applied bleomycin intratracheally to young and aged mice. We found that injury in aged mice elicited capillary rarefaction, while injury in young mice resulted in increased capillary density. ECs from the lungs of injured aged mice relative to young mice demonstrated elevated pro-fibrotic and reduced vascular homeostasis gene expression. Among the latter, Nos3 (encoding the enzyme endothelial nitric oxide synthase, eNOS) was transiently upregulated in lung ECs from young but not aged mice following injury. Young mice deficient in eNOS recapitulated the non-resolving lung fibrosis observed in aged animals following injury, suggesting that eNOS directly participates in lung fibrosis resolution. Activation of the NO receptor soluble guanylate cyclase in human lung fibroblasts reduced TGFβ-induced pro-fibrotic gene and protein expression. Additionally, loss of eNOS in human lung ECs reduced the suppression of TGFβ-induced lung fibroblast activation in 2D and 3D co-cultures. Altogether, our results demonstrate that persistent lung fibrosis in aged mice is accompanied by capillary rarefaction, loss of EC identity, and impaired eNOS expression. Targeting vascular function may thus be critical to promote lung repair and fibrosis resolution in aging and IPF.

The polarity protein Scrib limits atherosclerosis development in mice

AIMS

The protein Scrib (Scribble 1) is known to control apico-basal polarity in epithelial cells. The role of polarity proteins in the vascular system remains poorly characterized; however, we previously reported that Scrib maintains the endothelial phenotype and directed migration. On this basis, we hypothesized that Scrib has anti-atherosclerotic functions.

METHODS AND RESULTS

Tamoxifen-induced Scrib-knockout mice were crossed with ApoE-/- knockout mice and spontaneous atherosclerosis under high-fat diet (HFD), as well as accelerated atherosclerosis in response to partial carotid artery ligation and HFD, was induced. Deletion of Scrib resulted in increased atherosclerosis development in both models. Mechanistically, flow- as well as acetylcholine-induced endothelium-dependent relaxation and AKT phosphorylation was reduced by deletion of Scrib, whereas vascular permeability and leucocyte extravasation were increased after Scrib knockout. Scrib immune pull down in primary carotid endothelial cells and mass spectrometry identified Arhgef7 (Rho Guanine Nucleotide Exchange Factor 7, βPix) as interaction partner. Scrib or Arhgef7 down-regulation by siRNA reduced the endothelial barrier function in human umbilical vein endothelial cells. Gene expression analysis from murine samples and from human biobank material of carotid endarterectomies indicated that loss of Scrib resulted in endothelial dedifferentiation with a decreased expression of endothelial signature genes.

CONCLUSIONS

By maintaining a quiescent endothelial phenotype, the polarity protein Scrib elicits anti-atherosclerotic functions.

Nur77 deficiency exacerbates cardiac fibrosis after myocardial infarction by promoting endothelial-to-mesenchymal transition

Cardiac fibrosis is a reparative process after myocardial infarction (MI), which leads to cardiac remodeling and finally heart failure. Endothelial-to-mesenchymal transition (EndMT) is induced after MI and contributes to cardiac fibrosis after MI. Orphan nuclear receptor Nur77 is a key regulator of inflammation, angiogenesis, proliferation, and apoptosis in vascular endothelial cells. Here, we investigated the role of orphan nuclear receptor Nur77 in EndMT and cardiac fibrosis after MI. Cardiac fibrosis was induced through MI by ligation of the left anterior descending coronary artery. We demonstrated that Nur77 knockout aggravated cardiac dysfunction and cardiac fibrosis 30 days after MI. Moreover, Nur77 deficiency resulted in enhanced EndMT as shown by increased expression of FSP-1, SM22α, Snail, and decreased expression of PECAM-1 and eNOS compared with wild-type mice after MI. Then, we found overexpression Nur77 in human coronary artery endothelial cells significantly inhibited interleukin 1β and transforming growth factor β2-induced EndMT, as shown by a reduced transition to a fibroblast-like phenotype and preserved angiogenesis potential. Mechanistically, we demonstrated that Nur77 downregulated EndMT by inhibiting the nuclear factor-κB-dependent pathway. In conclusion, Nur77 is involved in cardiac fibrosis by inhibiting EndMT and may be a promising target for therapy of cardiac fibrosis after MI.

Evidence for endothelial-to-mesenchymal transition in human brain arteriovenous malformations

BACKGROUND

Brain arteriovenous malformations (AVMs) are rare, potentially devastating cerebrovascular lesions that can occur in both children and adults. AVMs are largely sporadic and the basic disease biology remains unclear, limiting advances in both detection and treatment. This study aimed to investigate human brain AVMs for endothelial-to-mesenchymal transition (EndMT), a process recently implicated in cerebral cavernous malformations (CCMs).

METHODS

We used 29 paraffin-embedded and 13 fresh/frozen human brain AVM samples to profile expression of panels of EndMT-associated proteins and RNAs. CCMs, a cerebrovascular disease also characterized by abnormal vasculature, were used as a primary comparison, given that EndMT specifically contributes to CCM disease biology. AVM-derived cell lines were isolated from three fresh, surgical AVM samples and characterized by protein expression.

RESULTS

We observed high collagen deposition, high PAI-1 expression, and expression of EndMT-associated transcription factors such as KLF4, SNAI1, and SNAI2 and mesenchymal-associated markers such as VIM, ACTA2, and S100A4. SMAD-dependent TGF-β signaling was not strongly activated in AVMs and this pathway may be only partially involved in mediating EndMT. Using serum-free culture conditions, we isolated myofibroblast-like cell populations from AVMs that expressed a unique range of proteins associated with mature cell types and with EndMT. Conditioned medium from these cells led to increased proliferation of HUVECs and SMCs.

CONCLUSIONS

Collectively, our results suggest a role for EndMT in AVM disease. This may lead to new avenues for disease models to further our understanding of disease mechanisms, and to the development of improved diagnostics and therapeutics.

Amphiregulin promotes cardiac fibrosis post myocardial infarction by inducing the endothelial-mesenchymal transition via the EGFR pathway in endothelial cells

The endothelial-mesenchymal transition (EndMT) plays a key role in the development of cardiac fibrosis (CF) after acute myocardial infarction (AMI). The results of our previous study showed that amphiregulin (AR) expression was enhanced after MI. However, the role of AR on EndMT post MI remains unknown. This study aimed to elucidate the impact of AR on EndMT post MI and the associated molecular mechanisms. AR expression was markedly enhanced in infarct border area post MI, and endothelial cells were one of the primary cell sources of AR secretion. Stimulation with AR promoted endothelial cell proliferation, invasion, migration, collagen synthesis and EndMT. In addition, EGFR and downstream gene expression was significantly enhanced. In vivo, EndMT was significantly inhibited after lentivirus-AR-shRNA was delivered to the myocardium post MI. In addition, silencing AR ameliorated cardiac function by decreasing the extent of CF. Furthermore, the levels of EGFR pathway components in endothelial cells extracted from infarct border myocardium were all significantly decreased in lentivirus-AR-shRNA-treated MI mice. Our results demonstrate that AR induces CF post MI by enhancing EndMT in endothelial cells. Thus, targeting the regulation of AR may provide a potentially novel therapeutic option for CF after MI.

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.

A Computational Model of the Endothelial to Mesenchymal Transition

Endothelial cells (ECs) form the lining of lymph and blood vessels. Changes in tissue requirements or wounds may cause ECs to behave as tip or stalk cells. Alternatively, they may differentiate into mesenchymal cells (MCs). These processes are known as EC activation and endothelial-to-mesenchymal transition (EndMT), respectively. EndMT, Tip, and Stalk EC behaviors all require SNAI1, SNAI2, and Matrix metallopeptidase (MMP) function. However, only EndMT inhibits the expression of VE-cadherin, PECAM1, and VEGFR2, and also leads to EC detachment. Physiologically, EndMT is involved in heart valve development, while a defective EndMT regulation is involved in the physiopathology of cardiovascular malformations, congenital heart disease, systemic and organ fibrosis, pulmonary arterial hypertension, and atherosclerosis. Therefore, the control of EndMT has many promising potential applications in regenerative medicine. Despite the fact that many molecular components involved in EC activation and EndMT have been characterized, the system-level molecular mechanisms involved in this process have not been elucidated. Toward this end, hereby we present Boolean network model of the molecular involved in the regulation of EC activation and EndMT. The simulated dynamic behavior of our model reaches fixed and cyclic patterns of activation that correspond to the expected EC and MC cell types and behaviors, recovering most of the specific effects of simple gain and loss-of-function mutations as well as the conditions associated with the progression of several diseases. Therefore, our model constitutes a theoretical framework that can be used to generate hypotheses and guide experimental inquiry to comprehend the regulatory mechanisms behind EndMT. Our main findings include that both the extracellular microevironment and the pattern of molecular activity within the cell regulate EndMT. EndMT requires a lack of VEGFA and sufficient oxygen in the extracellular microenvironment as well as no FLI1 and GATA2 activity within the cell. Additionally Tip cells cannot undergo EndMT directly. Furthermore, the specific conditions that are sufficient to trigger EndMT depend on the specific pattern of molecular activation within the cell.

Endothelial autophagy deficiency induces IL6 - dependent endothelial mesenchymal transition and organ fibrosis

Macroautophagy/autophagy plays a vital role in the homeostasis of diverse cell types. Vascular endothelial cells contribute to vascular health and play a unique role in vascular biology. Here, we demonstrated that autophagy defects in endothelial cells induced IL6 (interleukin 6)-dependent endothelial-to-mesenchymal transition (EndMT) and organ fibrosis with metabolic defects in mice. Inhibition of autophagy, either by a specific inhibitor or small interfering RNA (siRNA) for ATG5 (autophagy related 5), in human microvascular endothelial cells (HMVECs) induced EndMT. The IL6 level was significantly higher in ATG5 siRNA-transfected HMVECs culture medium compared with the control HMVECs culture medium, and neutralization of IL6 by a specific antibody completely inhibited EndMT in ATG5 siRNA-transfected HMVECs. Similar to the in vitro data, endothelial-specific atg5 knockout mice (Atg5 Endo; Cdh5-Cre Atg5 flox/flox mice) displayed both EndMT-associated kidney and heart fibrosis when compared to littermate controls. The plasma level of IL6 was higher in Atg5 Endo compared to that of control mice, and fibrosis was accelerated in Atg5 Endo treated with a HFD; neutralization of IL6 by a specific antibody inhibited EndMT and fibrosis in HFD-fed Atg5 Endo associated with the amelioration of metabolic defects. These results revealed the essential role of autophagy in endothelial cell integrity and revealed that the disruption of endothelial autophagy could lead to significant pathological IL6-dependent EndMT and organ fibrosis. Abbreviations: 3-MA: 3-methyladenine; ATG5: autophagy related 5; EndMT: endothelial-to-mesenchymal transition; HES: hematoxylin and eosin stain; HFD: high-fat diet; HMVECs: human microvascular endothelial cells; IFNG: interferon gamma; IL6: interleukin 6; MTS: Masson's trichrome staining; NFD: normal-fat diet; siRNA: small interfering RNA; SMAD3: SMAD family member 3; TGFB: transforming growth factor β; TNF: tumor necrosis factor; VEGFA: vascular endothelial growth factor A.

Gene Expression Profiles Induced by a Novel Selective Peroxisome Proliferator-Activated Receptor α Modulator (SPPARMα) Pemafibrate

Pemafibrate is the first clinically-available selective peroxisome proliferator-activated receptor α modulator (SPPARMα) that has been shown to effectively improve hypertriglyceridemia and low high-density lipoprotein cholesterol (HDL-C) levels. Global gene expression analysis reveals that the activation of PPARα by pemafibrate induces fatty acid (FA) uptake, binding, and mitochondrial or peroxisomal oxidation as well as ketogenesis in mouse liver. Pemafibrate most profoundly induces HMGCS2 and PDK4, which regulate the rate-limiting step of ketogenesis and glucose oxidation, respectively, compared to other fatty acid metabolic genes in human hepatocytes. This suggests that PPARα plays a crucial role in nutrient flux in the human liver. Additionally, pemafibrate induces clinically favorable genes, such as ABCA1, FGF21, and VLDLR. Furthermore, pemafibrate shows anti-inflammatory effects in vascular endothelial cells. Pemafibrate is predicted to exhibit beneficial effects in patients with atherogenic dyslipidemia and diabetic microvascular complications.

Optical coherence tomography for in vivo imaging of endocardial to mesenchymal transition during avian heart development

The endocardial to mesenchymal transition (EndMT) that occurs in endocardial cushions during heart development is critical for proper heart septation and formation of the heart's valves. In EndMT, cells delaminate from the endocardium and migrate into the previously acellular endocardial cushions. Optical coherence tomography (OCT) imaging uses the optical properties of tissues for contrast, and during early development OCT can differentiate cellular versus acellular tissues. Here we show that OCT can be used to non-invasively track EndMT progression in vivo in the outflow tract cushions of chicken embryos. This enables in vivo studies to elucidate factors leading to cardiac malformations.

Learn from Your Elders: Developmental Biology Lessons to Guide Maturation of Stem Cell-Derived Cardiomyocytes

Human pluripotent stem cells (hPSCs) offer a multifaceted platform to study cardiac developmental biology, understand disease mechanisms, and develop novel therapies. Remarkable progress over the last two decades has led to methods to obtain highly pure hPSC-derived cardiomyocytes (hPSC-CMs) with reasonable ease and scalability. Nevertheless, a major bottleneck for the translational application of hPSC-CMs is their immature phenotype, resembling that of early fetal cardiomyocytes. Overall, bona fide maturation of hPSC-CMs represents one of the most significant goals facing the field today. Developmental biology studies have been pivotal in understanding the mechanisms to differentiate hPSC-CMs. Similarly, evaluation of developmental cues such as electrical and mechanical activities or neurohormonal and metabolic stimulations revealed the importance of these pathways in cardiomyocyte physiological maturation. Those signals cooperate and dictate the size and the performance of the developing heart. Likewise, this orchestra of stimuli is important in promoting hPSC-CM maturation, as demonstrated by current in vitro maturation approaches. Different shades of adult-like phenotype are achieved by prolonging the time in culture, electromechanical stimulation, patterned substrates, microRNA manipulation, neurohormonal or metabolic stimulation, and generation of human-engineered heart tissue (hEHT). However, mirroring this extremely dynamic environment is challenging, and reproducibility and scalability of these approaches represent the major obstacles for an efficient production of mature hPSC-CMs. For this reason, understanding the pattern behind the mechanisms elicited during the late gestational and early postnatal stages not only will provide new insights into postnatal development but also potentially offer new scalable and efficient approaches to mature hPSC-CMs.

Endothelial to Mesenchymal Transition: Role in Physiology and in the Pathogenesis of Human Diseases

Numerous studies have demonstrated that endothelial cells are capable of undergoing endothelial to mesenchymal transition (EndMT), a newly recognized type of cellular transdifferentiation. EndMT is a complex biological process in which endothelial cells adopt a mesenchymal phenotype displaying typical mesenchymal cell morphology and functions, including the acquisition of cellular motility and contractile properties. Endothelial cells undergoing EndMT lose the expression of endothelial cell-specific proteins such as CD31/platelet-endothelial cell adhesion molecule, von Willebrand factor, and vascular-endothelial cadherin and initiate the expression of mesenchymal cell-specific genes and the production of their encoded proteins including α-smooth muscle actin, extra domain A fibronectin, N-cadherin, vimentin, fibroblast specific protein-1, also known as S100A4 protein, and fibrillar type I and type III collagens. Transforming growth factor-β1 is considered the main EndMT inducer. However, EndMT involves numerous molecular and signaling pathways that are triggered and modulated by multiple and often redundant mechanisms depending on the specific cellular context and on the physiological or pathological status of the cells. EndMT participates in highly important embryonic development processes, as well as in the pathogenesis of numerous genetically determined and acquired human diseases including malignant, vascular, inflammatory, and fibrotic disorders. Despite intensive investigation, many aspects of EndMT remain to be elucidated. The identification of molecules and regulatory pathways involved in EndMT and the discovery of specific EndMT inhibitors should provide novel therapeutic approaches for various human disorders mediated by EndMT.

Cross-Talk between Neurohormonal Pathways and the Immune System in Heart Failure: A Review of the Literature

Heart failure is a complex clinical syndrome involving a multitude of neurohormonal pathways including the renin-angiotensin-aldosterone system, sympathetic nervous system, and natriuretic peptides system. It is now emerging that neurohumoral mechanisms activated during heart failure, with both preserved and reduced ejection fraction, modulate cells of the immune system. Indeed, these cells express angiotensin I receptors, adrenoceptors, and natriuretic peptides receptors. Ang II modulates macrophage polarization, promoting M2 macrophages phenotype, and this stimulation can influence lymphocytes Th1/Th2 balance. β-AR activation in monocytes is responsible for inhibition of free oxygen radicals production, and together with α2-AR can modulate TNF-α receptor expression and TNF-α release. In dendritic cells, activation of β2-AR inhibits IL-12 production, resulting in the inhibition of Th1 and promotion of Th2 differentiation. ANP induces the activation of secretion of superoxide anion in polymorphonucleated cells; reduces TNF-α and nitric oxide secretion in macrophages; and attenuates the exacerbated TH1 responses. BNP in macrophages can stimulate ROS production, up-regulates IL-10, and inhibits IL-12 and TNF-α release by dendritic cells, suggesting an anti-inflammatory cytokines profile induction. Therefore, different neurohormonal-immune cross-talks can determine the phenotype of cardiac remodeling, promoting either favorable or maladaptive responses. This review aims to summarize the available knowledge on neurohormonal modulation of immune responses, providing supportive rational background for further research.

Endothelial Cells Tissue-Specific Origins Affects Their Responsiveness to TGF-β2 during Endothelial-to-Mesenchymal Transition

The endothelial-to-mesenchymal transition (EndMT) is a biological process where endothelial cells (ECs) acquire a fibroblastic phenotype after concomitant loss of the apical-basal polarity and intercellular junction proteins. This process is critical to embryonic development and is involved in diseases such as fibrosis and tumor progression. The signaling pathway of the transforming growth factor β (TGF-β) is an important molecular route responsible for EndMT activation. However, it is unclear whether the anatomic location of endothelial cells influences the activation of molecular pathways responsible for EndMT induction. Our study investigated the molecular mechanisms and signaling pathways involved in EndMT induced by TGF-β2 in macrovascular ECs obtained from different sources. For this purpose, we used four types of endothelial cells (coronary artery endothelial cells, CAECs; primary aortic endothelial cells PAECs; human umbilical vein endothelia cells, HUVECs; and human pulmonary artery endothelial cells, HPAECs) and stimulated with 10 ng/mL of TGF-β2. We observed that among the ECs analyzed in this study, PAECs showed the best response to the TGF-β2 treatment, displaying phenotypic changes such as loss of endothelial marker and acquisition of mesenchymal markers, which are consistent with the EndMT activation. Moreover, the PAECs phenotypic transition was probably triggered by the extracellular signal–regulated kinases 1/2 (ERK1/2) signaling pathway activation. Therefore, the anatomical origin of ECs influences their ability to undergo EndMT and the selective inhibition of the ERK pathway may suppress or reverse the progression of diseases caused or aggravated by the involvement EndMT activation.

The Role of Angiogenesis and Pro-Angiogenic Exosomes in Regenerative Dentistry

Dental surgeries can result in traumatic wounds that provoke major discomfort and have a high risk of infection. In recent years, density research has taken a keen interest in finding answers to this problem by looking at the latest results made in regenerative medicine and adapting them to the specificities of oral tissue. One of the undertaken directions is the study of angiogenesis as an integrative part of oral tissue regeneration. The stimulation of this process is intended to enhance the local availability of stem cells, oxygen levels, nutrient supply, and evacuation of toxic waste. For a successful stimulation of local angiogenesis, two major cellular components must be considered: the stem cells and the vascular endothelial cells. The exosomes are extracellular vesicles, which mediate the communication between two cell types. In regenerative dentistry, the analysis of exosome miRNA content taps into the extended communication between these cell types with the purpose of improving the regenerative potential of oral tissue. This review analyzes the stem cells available for the dentistry, the molecular cargo of their exosomes, and the possible implications these may have for a future therapeutic induction of angiogenesis in the oral wounds.

Phosphocreatine Attenuates Isoproterenol-Induced Cardiac Fibrosis and Cardiomyocyte Apoptosis

The present study was designed to further explore the role and the underlying molecular mechanism of phosphocreatine (PCr) for cardiac fibrosis in vivo. Isoproterenol (ISO) was used to induce cardiac fibrosis in rats. PCr administration ameliorated fibrosis by reducing collagen accumulation and fibrosis-related signals, including transforming growth factor beta 1 (TGF-β1), alpha smooth muscle actin (α-SMA), collagen type I, and collagen type III. Mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B (NF-κB) signaling pathways, including p38, extracellular signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p65, were highly activated by ISO and blocked by PCr. Moreover, PCr decreased ISO-induced matrix metalloproteinase-9 (MMP-9) and increased the tissue inhibitor of metalloproteinase-1 (TIMP-1) expression. Furthermore, PCr suppressed cardiomyocyte apoptosis induced by ISO, as shown by downregulated expression of the proapoptotic caspase-3, Bax, and upregulated expression of the antiapoptotic Bcl-2. Taken together, PCr can be an effective agent for preventing cardiac fibrosis and cardiomyocyte apoptosis.

Hemodynamics in Cardiac Development

The beating heart is subject to intrinsic mechanical factors, exerted by contraction of the myocardium (stretch and strain) and fluid forces of the enclosed blood (wall shear stress). The earliest contractions of the heart occur already in the 10-somite stage in the tubular as yet unsegmented heart. With development, the looping heart becomes asymmetric providing varying diameters and curvatures resulting in unequal flow profiles. These flow profiles exert various wall shear stresses and as a consequence different expression patterns of shear responsive genes. In this paper we investigate the morphological alterations of the heart after changing the blood flow by ligation of the right vitelline vein in a model chicken embryo and analyze the extended expression in the endocardial cushions of the shear responsive gene Tgfbeta receptor III. A major phenomenon is the diminished endocardial-mesenchymal transition resulting in hypoplastic (even absence of) atrioventricular and outflow tract endocardial cushions, which might be lethal in early phases. The surviving embryos exhibit several cardiac malformations including ventricular septal defects and malformed semilunar valves related to abnormal development of the aortopulmonary septal complex and the enclosed neural crest cells. We discuss the results in the light of the interactions between several shear stress responsive signaling pathways including an extended review of the involved Vegf, Notch, Pdgf, Klf2, eNos, Endothelin and Tgfβ/Bmp/Smad networks.

Influence of blood flow on cardiac development

The role of hemodynamics in cardiovascular development is not well understood. Indeed, it would be remarkable if it were, given the dauntingly complex array of intricately synchronized genetic, molecular, mechanical, and environmental factors at play. However, with congenital heart defects affecting around 1 in 100 human births, and numerous studies pointing to hemodynamics as a factor in cardiovascular morphogenesis, this is not an area in which we can afford to remain in the dark. This review seeks to present the case for the importance of research into the biomechanics of the developing cardiovascular system. This is accomplished by i) illustrating the basics of some of the highly complex processes involved in heart development, and discussing the known influence of hemodynamics on those processes; ii) demonstrating how altered hemodynamic environments have the potential to bring about morphological anomalies, citing studies in multiple animal models with a variety of perturbation methods; iii) providing examples of widely used technological innovations which allow for accurate measurement of hemodynamic parameters in embryos; iv) detailing the results of studies in avian embryos which point to exciting correlations between various hemodynamic manipulations in early development and phenotypic defect incidence in mature hearts; and finally, v) stressing the relevance of uncovering specific biomechanical pathways involved in cardiovascular formation and remodeling under adverse conditions, to the potential treatment of human patients. The time is ripe to unravel the contributions of hemodynamics to cardiac development, and to recognize their frequently neglected role in the occurrence of heart malformation phenotypes.

Endothelial to Mesenchymal Transition Represents a Key Link in the Interaction between Inflammation and Endothelial Dysfunction

Endothelial cells that line the inner walls of blood vessels are in direct contact with blood and display remarkable heterogeneity in their response to exogenous stimuli. These ECs have unique location-dependent properties determined by the corresponding vascular beds and play an important role in regulating the homeostasis of the vascular system. Evidence suggests that vascular endothelial cells exposed to various environments undergo dynamic phenotypic switching, a key biological program in the context of endothelial heterogeneity, but that might result in EC dysfunction and, in turn, cause a variety of human diseases. Emerging studies show the importance of endothelial to mesenchymal transition (EndMT) in endothelial dysfunction during inflammation. EndMT is a complex biological process in which ECs lose their endothelial characteristics, acquire mesenchymal phenotypes, and express mesenchymal cell markers, such as alpha smooth muscle actin and fibroblast-specific protein 1. EndMT is induced by inflammatory responses, leading to pathological states, including tissue fibrosis, pulmonary arterial hypertension, and atherosclerosis, via dysfunction of the vascular system. Although the mechanisms associated with inflammation-induced EndMT have been identified, unraveling the specific role of this phenotypic switching in vascular dysfunction remains a challenge. Here, we review the current understanding on the interactions between inflammatory processes, EndMT, and endothelial dysfunction, with a focus on the mechanisms that regulate essential signaling pathways. Identification of such mechanisms will guide future research and could provide novel therapeutic targets for the treatment of vascular diseases.