Role of myofibroblasts in vascular remodelling: focus on restenosis and aneurysm

Single-Cell Analyses Offer Insights into the Different Remodeling Programs of Arteries and Veins

Arteries and veins develop different types of occlusive diseases and respond differently to injury. The biological reasons for this discrepancy are not well understood, which is a limiting factor for the development of vein-targeted therapies. This study contrasts human peripheral arteries and veins at the single-cell level, with a focus on cell populations with remodeling potential. Upper arm arteries (brachial) and veins (basilic/cephalic) from 30 organ donors were compared using a combination of bulk and single-cell RNA sequencing, proteomics, flow cytometry, and histology. The cellular atlases of six arteries and veins demonstrated a 7.8× higher proportion of contractile smooth muscle cells (SMCs) in arteries and a trend toward more modulated SMCs. In contrast, veins showed a higher abundance of endothelial cells, pericytes, and macrophages, as well as an increasing trend in fibroblasts. Activated fibroblasts had similar proportions in both types of vessels but with significant differences in gene expression. Modulated SMCs and activated fibroblasts were characterized by the upregulation of MYH10, FN1, COL8A1, and ITGA10. Activated fibroblasts also expressed F2R, POSTN, and COMP and were confirmed by F2R/CD90 flow cytometry. Activated fibroblasts from veins were the top producers of collagens among all fibroblast populations from both types of vessels. Venous fibroblasts were also highly angiogenic, proinflammatory, and hyper-responders to reactive oxygen species. Differences in wall structure further explain the significant contribution of fibroblast populations to remodeling in veins. Fibroblasts are almost exclusively located outside the external elastic lamina in arteries, while widely distributed throughout the venous wall. In line with the above, ECM-targeted proteomics confirmed a higher abundance of fibrillar collagens in veins vs. more basement ECM components in arteries. The distinct cellular compositions and transcriptional programs of reparative populations in arteries and veins may explain differences in acute and chronic wall remodeling between vessels. This information may be relevant for the development of antistenotic therapies.

Post-angioplasty remodeling of coronary arteries investigated via a chemo-mechano-biological in silico model

This work presents the application of a chemo-mechano-biological constitutive model of soft tissues for describing tissue inflammatory response to damage in collagen constituents. The material model is implemented into a nonlinear finite element formulation to follow up a coronary standard balloon angioplasty for one year. Numerical results, compared with available in vivo clinical data, show that the model reproduces the temporal dynamics of vessel remodeling associated with subintimal damage. Such dynamics are bimodular, being characterized by an early tissue resorption and lumen enlargement, followed by late tissue growth and vessel constriction. Applicability of the modeling framework in retrospective studies is demonstrated, and future extension towards prospective applications is discussed.

Effect of sequential release of sirolimus and rosuvastatin using silk fibroin microneedle to prevent intimal hyperplasia

Intimal hyperplasia (IH) is a major cause of vascular restenosis after bypass surgery, which progresses as a series of processes from the acute to chronic stage in response to endothelial damage during bypass grafting. A strategic localized drug delivery system that reflects the pathophysiology of IH and minimizes systemic side effects is necessary. In this study, the sequential release of sirolimus, a mechanistic target of rapamycin (mTOR) inhibitor, and statin, an HMG-COA inhibitor, was realized as a silk fibroin-based microneedle device in vivo. The released sirolimus in the acute stage reduced neointima (NI) and vascular fibrosis through mTOR inhibition. Furthermore, rosuvastatin, which was continuously released from the acute to chronic stage, reduced vascular stiffness and apoptosis through the inactivation of Yes-associated protein (YAP). The sequential release of sirolimus and rosuvastatin confirmed the synergistic treatment effects on vascular inflammation, VSMC proliferation, and ECM degradation remodeling through the inhibition of transforming growth factor (TGF)-beta/NF-κB pathway. These results demonstrate the therapeutic effect on preventing restenosis with sufficient vascular elasticity and significantly reduced IH in response to endothelial damage. Therefore, this study suggests a promising strategy for treating coronary artery disease through localized drug delivery of customized drug combinations.

Smad2/3 signaling involved in urotensin II-induced phenotypic differentiation, collagen synthesis and migration of rat aortic adventitial fibroblasts

Objective. To investigate whether Smad2/3 signaling is involved in urotensin II (UII) induced activation of aortic adventitial fibroblasts. Materials and Methods. Growth-arrested adventitial fibroblasts were stimulated with UII in the presence or absence of urotensin II receptor (UT) antagonist SB710411 or transfected with Smad2/3 small inhibitory RNA (siRNA). UII stimulated Smad2/3 phosphorylation, α-smooth muscle actin (α-SMA), and collagen I expression and migration of adventitial fibroblasts were evaluated by western blot analysis, real-time reverse transcription polymerase chain reaction, immunofluorescence, ELISA, and transwell migration assay, respectively. Results. In cultured adventitial fibroblasts, UII time- and dose-dependently stimulated Smad2/3 protein phosphorylation, with maximal effect at 10-8 mol/l (increased by 147.2%, P<0.001). UII stimulated Smad2/3 upregulation and nuclear translocation. SB710411 significantly inhibited these effects. In addition, UII potently induced α-SMA and procollagen 1 protein or mRNA expression (P<0.01), which were completely blocked by Smad2 (decreased by 75.1%, 54.2% in protein, and by 73.3% and 38.2% in mRNA, respectively, P<0.01) or Smad3 siRNA (decreased by 80.3% and 47.0% in protein, and by 72.3% and 47.7% in mRNA, respectively, P<0.01). Meanwhile, Smad2 or smad3 siRNA significantly inhibited the UII-induced collagen 1 secretion and cell migration. Conclusions. UII may stimulate adventitial-fibroblast phenotype conversion, migration, and collagen I synthesis via phosphorylated-Smad2/3 signal transduction pathways.

Roles and mechanism of IL-11 in vascular diseases

Vascular diseases are the leading cause of morbidity and mortality worldwide. Therefore, effective treatment strategies that can reduce the risk of vascular diseases are urgently needed. The relationship between Interleukin-11 (IL-11) and development of vascular diseases has gained increasing attention. IL-11, a target for therapeutic research, was initially thought to participate in stimulating platelet production. Additional research concluded that IL-11 is effective in treating several vascular diseases. However, the function and mechanism of IL-11 in these diseases remain unknown. This review summarizes IL-11 expression, function, and signal transduction mechanism. This study also focuses on the role of IL-11 in coronary artery disease, hypertension, pulmonary hypertension, cerebrovascular disease, aortic disease, and other vascular diseases and its potential as a therapeutic target. Consequently, this study provides new insight into the clinical diagnosis and treatment of vascular diseases.

Arterial tissues and their inflammatory response to collagen damage: A continuum in silico model coupling nonlinear mechanics, molecular pathways, and cell behavior

Damage in soft biological tissues causes an inflammatory reaction that initiates a chain of events to repair the tissue. This work presents a continuum model and its in silico implementation that describe the cascade of mechanisms leading to tissue healing, coupling mechanical as well as chemo-biological processes. The mechanics is described by means of a Lagrangian nonlinear continuum mechanics framework and follows the homogenized constrained mixtures theory. Plastic-like damage, growth and remodeling as well as homeostasis are taken into account. The chemo-biological pathways account for two molecular and four cellular species, and are activated by damage of collagen molecules in fibers. To consider proliferation, differentiation, diffusion and chemotaxis of species, diffusion-advection-reaction equations are employed. To the best of authors' knowledge, the proposed model combines for the first time such high number of chemo-mechano-biological mechanisms in a consistent continuum biomechanical framework. The resulting set of coupled differential equations describe balance of linear momentum, evolution of kinematic variables as well as mass balance equations. They are discretized in time according to a backward Euler finite difference scheme, and in space through a finite element Galerkin discretization. The features of the model are firstly demonstrated presenting the species dynamics and highlighting the influence of damage intensities on the growth outcome. In terms of a biaxial test, the chemo-mechano-biological coupling and the model's applicability to reproduce normal as well as pathological healing are shown. A last numerical example underlines the model's applicability to complex loading scenarios and inhomogeneous damage distributions. Concluding, the present work contributes towards comprehensive in silico models in biomechanics and mechanobiology.

A novel histological occlusion classification for coiled aneurysms based on multiphoton microscopy

OBJECTIVE

Intracranial aneurysm (IA) coiling remains the most commonly used endovascular approach for ruptured and unruptured IA, and recanalization is a common drawback that impairs treatment success. Angiographic occlusion and aneurysm healing are not synonymous, and histological evaluation of embolized aneurysms remains a challenge. We propose here an experimental study of coil embolization in animal models by multiphoton microscopy (MPM) in comparison with conventional histological staining. The purpose of his work is to analyze coil healing process using histological sections of aneurysms.

METHODS

Based on a rabbit elastase model, 27 aneurysms were fixed, embedded in resin, and cut in thin histological sections 1 month after coils implantation and after angiographic control. Hematoxylin and eosin (H&S) staining were realized. Non-stained adjacent slices were imaged for multiphoton excited autofluorescence (AF) and second-harmonic generation (SHG) to construct three-dimensional (3D) projections of sequentially and axially acquired images.

RESULTS

The contrast provided by the combination of these two imaging modalities can be used to distinguish five levels of aneurysm healing, based on a combination of thrombus evolution and increased extracellular matrix (ECM) deposit.

CONCLUSION

RDPC:\Users\SHAHUL\RDP6|We have established a novel histological scale from a rabbit elastase aneurysm model after coiling with a classification of five different stages thanks to nonlinear microscopy. This classification is an actualized tool in order to obtain a more precise evaluation of occlusion device efficacy in the scope of new innovative microscopy for research.

Role of Endothelial Progenitor Cells in Frailty

Frailty is a clinical condition closely related to aging which is characterized by a multidimensional decline in biological reserves, a failure of physiological mechanisms and vulnerability to minor stressors. Chronic inflammation, the impairment of endothelial function, age-related endocrine system modifications and immunosenescence are important mechanisms in the pathophysiology of frailty. Endothelial progenitor cells (EPCs) are considered important contributors of the endothelium homeostasis and turn-over. In the elderly, EPCs are impaired in terms of function, number and survival. In addition, the modification of EPCs' level and function has been widely demonstrated in atherosclerosis, hypertension and diabetes mellitus, which are the most common age-related diseases. The purpose of this review is to illustrate the role of EPCs in frailty. Initially, we describe the endothelial dysfunction in frailty, the response of EPCs to the endothelial dysfunction associated with frailty and, finally, interventions which may restore the EPCs expression and function in frail people.

LOX-1 deficiency increases ruptured abdominal aortic aneurysm via thinning of adventitial collagen

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a key mediator of inflammation and plays an important role in the pathogenesis of atherosclerosis. Conversely, LOX-1 deficiency has been shown to decrease inflammation and atherosclerosis, both of which have been proposed to contribute to abdominal aortic aneurysm (AAA) pathogenesis. However, the role of LOX-1 in AAA pathogenesis remains unknown. Here, we investigated the effects of Olr1 (which encodes LOX-1) deletion on angiotensin II (Ang II)-induced AAA in apolipoprotein E knockout (ApoE KO) mice to determine whether LOX-1 deficiency mitigates AAA development. To accomplish this, we used serial, non-invasive ultrasound assessment, which revealed that the incidence and expansion rate of AAA were similar regardless of Olr1 deletion. However, Olr1 deletion significantly increased severe AAAs, including ruptured AAAs resulting in death. Oil Red O staining of the harvested aortas showed that the extent of atheroma burden localized in aneurysmal lesions did not differ between LOX-1-deficient and control mice, suggesting that Olr1 deletion did not decrease atheroma burden in the aneurysmal wall. Further histopathological analysis revealed that aneurysmal lesions in LOX-1-deficient mice had fewer fibroblasts and myofibroblasts, as well as thinner adventitial collagen, although the degree of elastin fragmentation or disruption was similar between LOX-1-deficient and control mice. An in vitro study confirmed that the proliferation of adventitial fibroblasts collected from LOX-1-deficient mice was significantly attenuated despite Ang II stimulation. In conclusion, Olr1 deletion may not mitigate aneurysm development but rather increases the vulnerability of rupture by suppressing adventitial fibroblast proliferation and collagen synthesis.

Trypanosoma cruzi Infection Promotes Vascular Remodeling and Coexpression of α-Smooth Muscle Actin and Macrophage Markers in Cells of the Aorta

Chagas disease is an emerging global health problem; however, it remains neglected. Increased aortic stiffness (IAS), a predictor of cardiovascular events, has recently been reported in asymptomatic chronic Chagas patients. After vascular injury, smooth muscle cells (SMCs) can undergo alterations associated with phenotypic switch and transdifferentiation, promoting vascular remodeling and IAS. By studying different mouse aortic segments, we tested the hypothesis that Trypanosoma cruzi infection promotes vascular remodeling. Interestingly, the thoracic aorta was the most affected by the infection. Decreased expression of SMC markers and increased expression of proliferative markers were observed in the arteries of acutely infected mice. In acutely and chronically infected mice, we observed cells coexpressing SMC and macrophage (Mo) markers in the media and adventitia layers of the aorta, indicating that T. cruzi might induce cellular processes associated with SMC transdifferentiation into Mo-like cells or vice versa. In the adventitia, the Mo cell functional polarization was associated with an M2-like CD206+arginase-1+ phenotype despite the T. cruzi presence in the tissue. Only Mo-like cells in inflammatory foci were CD206+iNOS+. In addition to the disorganization of elastic fibers, we found thickening of the aortic layers during the acute and chronic phases of the disease. Our findings indicate that T. cruzi infection induces a vascular remodeling with SMC dedifferentiation and increased cell populations coexpressing α-SMA and Mo markers that could be associated with IAS promotion. These data highlight the importance of studying large vessel homeostasis in Chagas disease.

Adventitial Fibroblasts in Aortic Aneurysm: Unraveling Pathogenic Contributions to Vascular Disease

Aortic aneurysm (AA) is a degenerative vascular disease that involves aortic dilatation, and, if untreated, it can lead to rupture. Despite its significant impact on the healthcare system, its multifactorial nature and elusive pathophysiology contribute to limited therapeutic interventions that prevent the progression of AA. Thus, further research into the mechanisms underlying AA is paramount. Adventitial fibroblasts are one of the key constituents of the aortic wall, and they play an essential role in maintaining vessel structure and function. However, adventitial fibroblasts remain understudied when compared with endothelial cells and smooth muscle cells. Adventitial fibroblasts facilitate the production of extracellular matrix (ECM), providing structural integrity. However, during biomechanical stress and/or injury, adventitial fibroblasts can be activated into myofibroblasts, which move to the site of injury and secrete collagen and cytokines, thereby enhancing the inflammatory response. The overactivation or persistence of myofibroblasts has been shown to initiate pathological vascular remodeling. Therefore, understanding the underlying mechanisms involved in the activation of fibroblasts and in regulating myofibroblast activation may provide a potential therapeutic target to prevent or delay the progression of AA. This review discusses mechanistic insights into myofibroblast activation and associated vascular remodeling, thus illustrating the contribution of fibroblasts to the pathogenesis of AA.

Endocan, a Soluble Marker of Endothelial Cell Activation Is a Molecular Marker of Disease Severity in Women with Preeclampsia

Endocan is a proteoglycan secreted by activated endothelium that regulates angiogenesis via interaction with hepatocyte growth factor (HGF). We hypothesized that women diagnosed with preeclampsia (PE) and/or fetal growth restriction (FGR) have elevated circulating endocan concentrations in direct relationship with severity of clinical manifestations. Serum concentration of endocan and HGF were analyzed in 224 women grouped as healthy pregnant controls (P-CRL, n = 77), PE with severe features (sPE, n = 83), chronic hypertension (crHTN: n = 36), idiopathic FGR (n = 18), and healthy non-pregnant controls (NP-CRL, n = 7). Endocan and HGF measured by immunoassay were analyzed along with markers of inflammation, angiogenesis, and protein misfolding (urine congophilia). Endocan expression in the placenta and/or myometrium was studied by immunohistochemistry and real-time PCR. Compared to gestational age-matched P-CRL, women with early-onset sPE had higher circulating endocan concentrations. Among women with PE and/or FGR, endocan concentration correlated with soluble endoglin and urine congophilia but not with HGF or markers of inflammation or angiogenesis. In the placenta, endocan was expressed in villous and extravillous trophoblasts and endothelium. Intense endocan immunostaining was observed in plaque-like aggregations of sPE placentas complicated with FGR. In addition, thickened blood vessels in the myometrium of sPE patients stained positive for endocan. Women with early-onset sPE have elevated serum endocan likely reflecting chronic endothelial activation. Enhanced expression and/or deposition of endocan at the sites of placental injury and in remodeled maternal blood vessels supports a role for endocan in either vascular rescue or as a contributor to FGR and perhaps long-term cardiovascular morbidity.

Age and sex dependency of thoracic aortopathy in a mouse model of Marfan syndrome

Thoracic aortic aneurysm is one of the manifestations of Marfan syndrome (MFS) that is known to affect men more severely than women. However, the incidence of MFS is similar between men and women. The aim of this study is to show that during pathological aortic dilation, sex-dependent severity of thoracic aortopathy in a mouse model of MFS translates into sex-dependent alterations in cells and matrix of the ascending aorta, consequently affecting aortic biomechanics. Fibrillin-1 C1041G/+ (Het) mice were used as a mouse model of MFS. Ultrasound measurements from 3 to 12 mo showed increased aortic diameter in Het aorta, with larger percentage increase in diameter for males compared with females. Immunohistochemistry showed decreased contractile smooth muscle cells in Het aortic wall compared with healthy aorta, which was accompanied by decreased contractility measured by wire myography. Elastin autofluorescence, second-harmonic generation microscopy of collagen fibers, and passive biomechanical assessments using myography showed more severe damage to elastin fibers, increased medial fibrosis, and increased stiffness of the aortic wall in MFS males but not females. Male and female Het mice showed increased expression of Sca-1-positive adventitial progenitor cells versus controls at young ages. In agreement with clinical data, Het mice demonstrate sex-dependent severity of thoracic aortopathy. It was also shown that aging exacerbates the disease state especially for males. Our findings suggest that female mice are protected from progression of aortic dilation at early ages, leading to a lag in aneurysm growth.NEW & NOTEWORTHY Male Fbn1^C1041G/+ mice show more severe thoracic aortic changes compared with females, especially at 12 mo of age. Up to 6 mo of age, Sca-1⁺ smooth muscle progenitor cells are more abundant in the adventitia of both male and female Fbn1 Het mice compared with wild types (WTs). Male and female Het mice show similar patterns of expression of Sca-1⁺ cells at early ages.

miR-133a Replacement Attenuates Thoracic Aortic Aneurysm in Mice

Background Thoracic aortic aneurysms (TAAs) occur because of abnormal remodeling of aortic extracellular matrix and are accompanied by the emergence of proteolytically active myofibroblasts. The microRNA miR-133a regulates cellular phenotypes and is reduced in clinical TAA specimens. This study tested the hypothesis that miR-133a modulates aortic fibroblast phenotype, and overexpression by lentivirus attenuates the development of TAA in a murine model. Methods and Results TAA was induced in mice. Copy number of miR-133a was reduced in TAA tissue and linear regression analysis confirmed an inverse correlation between aortic diameter and miR-133a. Analyses of phenotypic markers revealed an mRNA expression profile consistent with myofibroblasts in TAA tissue. Fibroblasts were isolated from the thoracic aortae of mice with/without TAA. When compared with controls, miR-133a was reduced, migration was increased, adhesion was reduced, and the ability to contract a collagen disk was increased. Overexpression/knockdown of miR-133a controlled these phenotypes. After TAA induction in mice, a single tail-vein injection of either miR-133a overexpression or scrambled sequence (control) lentivirus was performed. Overexpression of miR-133a attenuated TAA development. The pro-protein convertase furin was confirmed to be a target of miR-133a by luciferase reporter assay. Furin was elevated in this murine model of TAA and repressed by miR-133a replacement in vivo resulting in reduced proteolytic activation. Conclusions miR-133a regulates aortic fibroblast phenotype and over-expression prevented the development of TAA in a murine model. These findings suggest that stable alterations in aortic fibroblasts are associated with development of TAA and regulation by miR-133a may lead to a novel therapeutic strategy.

Myofibroblasts: Function, Formation, and Scope of Molecular Therapies for Skin Fibrosis

Myofibroblasts are contractile, α-smooth muscle actin-positive cells with multiple roles in pathophysiological processes. Myofibroblasts mediate wound contractions, but their persistent presence in tissues is central to driving fibrosis, making them attractive cell targets for the development of therapeutic treatments. However, due to shared cellular markers with several other phenotypes, the specific targeting of myofibroblasts has long presented a scientific and clinical challenge. In recent years, myofibroblasts have drawn much attention among scientific research communities from multiple disciplines and specialisations. As further research uncovers the characterisations of myofibroblast formation, function, and regulation, the realisation of novel interventional routes for myofibroblasts within pathologies has emerged. The research community is approaching the means to finally target these cells, to prevent fibrosis, accelerate scarless wound healing, and attenuate associated disease-processes in clinical settings. This comprehensive review article describes the myofibroblast cell phenotype, their origins, and their diverse physiological and pathological functionality. Special attention has been given to mechanisms and molecular pathways governing myofibroblast differentiation, and updates in molecular interventions.

Non-syndromic thoracic aortic aneurysm: cellular and molecular insights

Thoracic aortic aneurysm (TAA) develops silently and asymptomatically and is a major cause of mortality. TAA prevalence is greatly underestimated, it is usually diagnosed incidentally, and its treatment consists mainly of prophylactic surgery based on the aortic diameter. The lack of effective drugs and biological markers to identify and stratify TAAs by risk before visible symptoms results from scant knowledge of its pathophysiological mechanisms. Here we integrate the structural impairment affecting non-syndromic non-familial TAA with the main cellular and molecular changes described so far and consider how these changes are interconnected through specific pathways. The ultimate goal is to define much-needed novel markers of TAA, and so the potential of previously identified molecules to aid in early diagnosis/prognosis is also discussed. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Insights on the Pathogenesis of Aneurysm through the Study of Hereditary Aortopathies

Thoracic aortic aneurysms (TAA) are permanent and localized dilations of the aorta that predispose patients to a life-threatening risk of aortic dissection or rupture. The identification of pathogenic variants that cause hereditary forms of TAA has delineated fundamental molecular processes required to maintain aortic homeostasis. Vascular smooth muscle cells (VSMCs) elaborate and remodel the extracellular matrix (ECM) in response to mechanical and biochemical cues from their environment. Causal variants for hereditary forms of aneurysm compromise the function of gene products involved in the transmission or interpretation of these signals, initiating processes that eventually lead to degeneration and mechanical failure of the vessel. These include mutations that interfere with transduction of stimuli from the matrix to the actin-myosin cytoskeleton through integrins, and those that impair signaling pathways activated by transforming growth factor-β (TGF-β). In this review, we summarize the features of the healthy aortic wall, the major pathways involved in the modulation of VSMC phenotypes, and the basic molecular functions impaired by TAA-associated mutations. We also discuss how the heterogeneity and balance of adaptive and maladaptive responses to the initial genetic insult might contribute to disease.

An ultrastructural pathologist's views on fibroblasts, modified smooth muscle cells, wound healing, stenosing arteriopathies, Kawasaki disease, Dupuytren's contracture, and the stroma of carcinomas

It wasn't until 1960 that the dense bodies of the peripheral actin arrays of fibroblasts were finally visualized, i.e., stress fibers (SFs). Mistakenly assumed that its SFs turned the fibroblast into a unique cell situated somewhere in a continuum between it and a smooth muscle cell (SMC), it was descriptively named a "myofibroblast" (MF). Automatically, spindle cells with SFs and/or smooth muscle actin by SMA IHC-staining, became MFs, although endothelial cells, pericytes, modified SMCs (mSMC), and myoepithelial cells all contain SFs. An invisible "intermediate" cell was hypothesized to exist somewhere between SMA-negative and positive fibroblasts, and named a "proto-myofibroblast". The sub-epithelial spindle cells of normal and malignant tumors of the GI, GU, and respiratory tracts are all fibroblasts with SFs. The second erroneous myofibroblast came from a 1971 rat wound healing study and its 1974 human counterpart. Updated analysis of the papers' TEMs proved that the cells are mSMCs and not fibroblasts (AKA: MFs). The pathognomonic cells of Dupuytren's contracture are mSMCs and fibroblasts and that of the stenosing arteriopathy of Kawasaki Disease and other similar arteriopathies are mSMCs. TEM remains a powerful tool.

Aortic Aneurysms and Dissections Series

The aortic wall is composed of highly dynamic cell populations and extracellular matrix. In response to changes in the biomechanical environment, aortic cells and extracellular matrix modulate their structure and functions to increase aortic wall strength and meet the hemodynamic demand. Compromise in the structural and functional integrity of aortic components leads to aortic degeneration, biomechanical failure, and the development of aortic aneurysms and dissections (AAD). A better understanding of the molecular pathogenesis of AAD will facilitate the development of effective medications to treat these conditions. Here, we summarize recent findings on AAD published in ATVB. In this issue, we focus on the dynamics of aortic cells and extracellular matrix in AAD; in the next issue, we will focus on the role of signaling pathways in AAD.

Lactic acid-mediated endothelial to mesenchymal transition through TGF-β1 contributes to in-stent stenosis in poly-L-lactic acid stent

Currently, bioresorbable stents made with biodegradable materials are attracting more and more attentions in cardiovascular tissue engineering. Especially, poly-L-lactic acid (PLLA) stent has been regarded as the most promising one due to excellent biodegradability until serious in-stent restenosis at late stage was reported. This imply that the PLLA stent has side effect in cell function, and it is rarely reported the effect of degradation product of PLLA on endothelial function. Here we reported that lactic acid (LA) not acidic pH induced endothelial-to-mesenchymal transition (EndMT) leading to vascular fibrosis which may contribute to in-stent stenosis after PLLA stent implantation. Furthermore, we found TGF-β1 signaling was involved in boosting EndMT by LA. These results demonstrate a mechanism of in-stent stenosis induced by PLLA and indicate its utility for the future design of polymeric vascular scaffolds.

Remodeling of a Cell-Free Vascular Graft with Nanolamellar Intima into a Neovessel

Advances in cardiovascular materials have brought us improved artificial vessels with larger diameters for reducing adverse responses that drive acute thrombosis and the associated complications. Nonetheless, the challenge is still considerable when applying these materials in small-diameter blood vessels. Here we report the biomimetic design of an acellular small-diameter vascular graft with specifically lamellar nanotopography on the luminal surface via a modified freeze-cast technique. The experimental findings verify that the well-designed nanolamellar structure is able to inhibit the adherence and activation of platelets, induce oriented growth of endothelial cells, and eventually remodel a neovessel to maintain long-term patency in vivo. Furthermore, the results of numerical simulations in physically mimetic conditions reveal that the regularly lamellar nanopattern can manipulate blood flow to reduce the flow disturbance compared with random topography. Our current work not only creates a freeze-cast small-diameter vascular graft that employs topographic architecture to direct the vascular cell fates for revasculature but also rekindles confidence in biophysical cues for modulating in situ tissue regeneration.

Fibroblasts and Their Pathological Functions in the Fibrosis of Aortic Valve Sclerosis and Atherosclerosis

Cardiovascular diseases, such as atherosclerosis and aortic valve sclerosis (AVS) are driven by inflammation induced by a variety of stimuli, including low-density lipoproteins (LDL), reactive oxygen species (ROS), infections, mechanical stress, and chemical insults. Fibrosis is the process of compensating for tissue injury caused by chronic inflammation. Fibrosis is initially beneficial and maintains extracellular homeostasis. However, in the case of AVS and atherosclerosis, persistently active resident fibroblasts, myofibroblasts, and smooth muscle cells (SMCs) perpetually remodel the extracellular matrix under the control of autocrine and paracrine signaling from the immune cells. Myofibroblasts also produce pro-fibrotic factors, such as transforming growth factor-β1 (TGF-β1), angiotensin II (Ang II), and interleukin-1 (IL-1), which allow them to assist in the activation and migration of resident immune cells. Post wound repair, these cells undergo apoptosis or become senescent; however, in the presence of unresolved inflammation and persistence signaling for myofibroblast activation, the tissue homeostasis is disturbed, leading to excessive extracellular matrix (ECM) secretion, disorganized ECM, and thickening of the affected tissue. Accumulating evidence suggests that diverse mechanisms drive fibrosis in cardiovascular pathologies, and it is crucial to understand the impact and contribution of the various mechanisms for the control of fibrosis before the onset of a severe pathological consequence.

RhoGTPase in Vascular Disease

Ras-homologous (Rho)A/Rho-kinase pathway plays an essential role in many cellular functions, including contraction, motility, proliferation, and apoptosis, inflammation, and its excessive activity induces oxidative stress and promotes the development of cardiovascular diseases. Given its role in many physiological and pathological functions, targeting can result in adverse effects and limit its use for therapy. In this review, we have summarized the role of RhoGTPases with an emphasis on RhoA in vascular disease and its impact on endothelial, smooth muscle, and heart and lung fibroblasts. It is clear from the various studies that understanding the regulation of RhoGTPases and their regulators in physiology and pathological conditions is required for effective targeting of Rho.

Relationships Between Phenotype and Function of Blood CD4+ T-Cells and Ascending Thoracic Aortic Aneurysm: an Experimental Study

Introduction

Non-familial ascending thoracic aorta dilation and aneurysms (TAAs) are silent diseases in elderly patients. Histopathology revealed that functionally polarized infiltrating CD4⁺ T-cells play a key role in aortic wall weakening.

Objective

To evaluate the possible associations between phenotype and cytokine production of circulating CD4⁺ T-lymphocytes and the presence of TAA in patients with aortic valve disease (AVD).

Methods

We studied blood samples from 10 patients with TAA and 10 patients with AVD. Flow cytometry was used to quantify: a) CD4⁺ T-lymphocytes surface expression of CD25, CD28, and chemokine receptors (CCR5, CXCR3, CX3CR1); b) fractions of in vitro stimulated CD4⁺ T-cells producing cytokines (interferon gamma [IFN-γ], interleukin [IL]-17A, IL-21, IL-10); c) CD4⁺CD25^highFoxP3⁺ regulatory T-cells (Treg) fraction. Enzyme-linked immunosorbent assays (ELISA) were performed for cytokines (IFN-γ, IL-6, IL-10, IL-17A, IL-23, transforming growth factor beta [TGF-β]) and chemokines (RANTES, CX3CL1).

Results

The total CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells fraction was higher (P=0.0323) in AVD (20.452±4.673) than in TAA patients (8.633±2.030). The frequency ratio of CD4⁺ T-lymphocytes producing IFN-γ vs. IL-17A+IL-21 cytokine-producing CD4+ T-cells was higher (P=0.0239) in AVD (2.102±0.272) than in TAA (1.365±0.123) patients. The sum of CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells correlated positively with values of the previous cytokine ratio (P=0.0002, R=0.732). The ratio of CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells vs. Treg was higher (P=0.0008) in AVD (20.859±3.393) than in TAA (6.367±1.277) patients.

Conclusion

Our results show that the presence of TAA in subjects with AVD is associated with imbalance between phenotypic and cytokine-producing subsets of circulating CD4+ T-lymphocytes, prevalently oriented towards a pro-fibrotic and IFN-γ counteracting effect to functional polarization.

Endothelial progenitor cells in age-related vascular remodeling

Accumulating evidence has demonstrated that endothelial progenitor cells (EPCs) could facilitate the reendothelialization of injured arteries by replacing the dysfunctional endothelial cells, thereby suppressing the formation of neointima. Meanwhile, other findings suggest that EPCs may be involved in the pathogenesis of age-related vascular remodeling. This review is presented to summarize the characteristics of EPCs and age-related vascular remodeling. In addition, the role of EPCs in age-related vascular remodeling and possible solutions for improving the therapeutic effects of EPCs in the treatment of age-related diseases are discussed.

Endovascular stent-induced alterations in host artery mechanical environments and their roles in stent restenosis and late thrombosis

Cardiovascular stent restenosis remains a major challenge in interventional treatment of cardiovascular occlusive disease. Although the changes in arterial mechanical environment due to stent implantation are the main causes of the initiation of restenosis and thrombosis, the mechanisms that cause this initiation are still not fully understood. In this article, we reviewed the studies on the issue of stent-induced alterations in arterial mechanical environment and discussed their roles in stent restenosis and late thrombosis from three aspects: (i) the interaction of the stent with host blood vessel, involve the response of vascular wall, the mechanism of mechanical signal transmission, the process of re-endothelialization and late thrombosis; (ii) the changes of hemodynamics in the lumen of the vascular segment and (iii) the changes of mechanical microenvironment within the vascular segment wall due to stent implantation. This review has summarized and analyzed current work in order to better solve the two main problems after stent implantation, namely in stent restenosis and late thrombosis, meanwhile propose the deficiencies of current work for future reference.

Pathogenic Mechanisms of Bicuspid Aortic Valve Aortopathy

Bicuspid aortic valve (BAV) is the most common congenital valvular defect and is associated with ascending aortic dilation (AAD) in a quarter of patients. AAD has been ascribed both to the hemodynamic consequences of normally functioning and abnormal BAV morphology, and to the effect of rare and common genetic variation upon function of the ascending aortic media. AAD manifests in two overall and sometimes overlapping phenotypes: that of aortic root aneurysm, similar to the AAD of Marfan syndrome; and that of tubular AAD, similar to the AAD seen with tricuspid aortic valves (TAVs). These aortic phenotypes appear to be independent of BAV phenotype, have different embryologic origins and have unique etiologic factors, notably, regarding the role of hemodynamic changes inherent to the BAV phenotype. Further, in contrast to Marfan syndrome, the AAD seen with BAV is infrequently present as a strongly inherited syndromic phenotype; rather, it appears to be a less-penetrant, milder phenotype. Both reduced levels of normally functioning transcriptional proteins and structurally abnormal proteins have been observed in aneurysmal aortic media. We provide evidence that aortic root AAD has a stronger genetic etiology, sometimes related to identified common non-coding fibrillin-1 (FBN1) variants and other aortic wall protein variants in patients with BAV. In patients with BAV having tubular AAD, we propose a stronger hemodynamic influence, but with pathology still based on a functional deficit of the aortic media, of genetic or epigenetic etiology. Although it is an attractive hypothesis to ascribe common mechanisms to BAV and AAD, thus far the genetic etiologies of AAD have not been associated to the genetic etiologies of BAV, notably, not including BAV variants in NOTCH1 and GATA4.

Epigenetic regulation of TGF-β1 signalling in dilative aortopathy of the thoracic ascending aorta

The term 'epigenetics' refers to heritable, reversible DNA or histone modifications that affect gene expression without modifying the DNA sequence. Epigenetic modulation of gene expression also includes the RNA interference mechanism. Epigenetic regulation of gene expression is fundamental during development and throughout life, also playing a central role in disease progression. The transforming growth factor β1 (TGF-β1) and its downstream effectors are key players in tissue repair and fibrosis, extracellular matrix remodelling, inflammation, cell proliferation and migration. TGF-β1 can also induce cell switch in epithelial-to-mesenchymal transition, leading to myofibroblast transdifferentiation. Cellular pathways triggered by TGF-β1 in thoracic ascending aorta dilatation have relevant roles to play in remodelling of the vascular wall by virtue of their association with monogenic syndromes that implicate an aortic aneurysm, including Loeys-Dietz and Marfan's syndromes. Several studies and reviews have focused on the progression of aneurysms in the abdominal aorta, but research efforts are now increasingly being focused on pathogenic mechanisms of thoracic ascending aorta dilatation. The present review summarizes the most recent findings concerning the epigenetic regulation of effectors of TGF-β1 pathways, triggered by sporadic dilative aortopathy of the thoracic ascending aorta in the presence of a tricuspid or bicuspid aortic valve, a congenital malformation occurring in 0.5-2% of the general population. A more in-depth comprehension of the epigenetic alterations associated with TGF-β1 canonical and non-canonical pathways in dilatation of the ascending aorta could be helpful to clarify its pathogenesis, identify early potential biomarkers of disease, and, possibly, develop preventive and therapeutic strategies.

A Possible Early Biomarker for Bicuspid Aortopathy: Circulating Transforming Growth Factor β-1 to Soluble Endoglin Ratio

RATIONALE

The pathogenesis of bicuspid aortic valve (BAV)-associated aortopathy is poorly understood, and no prognostic biomarker is currently available.

OBJECTIVE

We aimed to identify putative circulating biomarkers pathogenetically and prognostically linked to bicuspid aortopathy.

METHODS AND RESULTS

By reverse transcription polymerase chain reaction, we evaluated gene expression variations (versus normal aorta) of transforming growth factor-β1 (TGF-β1), connective tissue growth factor, matrix metalloproteinase-2 (MMP-2), MMP-14, endoglin (ENG), and superoxide dismutase 3 in ascending aorta samples from 50 tricuspid and 70 patients with BAV undergoing surgery for aortic stenosis (aorta diameter ≤45 mm: BAV_non-dil or >45 mm: BAV_dil). Expression changes of the TGF-β1 active dimer and ENG were analyzed also by Western blot in ascending aorta samples from other 10 tricuspid aortic valve, 10 BAV_non-dil, and 10 BAV_dil patients. The serum concentration of study targets was assessed through ELISA and the ratio of serum TGF-β1/ENG (T/E) was evaluated. All BAV_non-dil patients underwent follow-up echocardiography to assess aortic growth rate. In BAV_non-dil patients, TGF-β1 and MMP-2 gene expression increased significantly, whereas MMP-14 and ENG expression decreased versus controls. Expression changes were confirmed at protein level for TGF-β1 and ENG. TGF-β1 serum concentration significantly decreased in tricuspid aortic valve and BAV_non-dil patients versus healthy subjects. ENG serum concentration decreased in all patients, more markedly in BAV_dil. A significant increase of the T/E ratio versus healthy subjects was unique of patients with BAV. In BAV_non-dil patients, a T/E ≥9 was independently associated in multivariable analysis with higher MMP-2 and lower superoxide dismutase 3 gene expression, independent of age and aortic diameter. A significant correlation was observed between baseline T/E ratio and aortic diameter growth rate in BAV_non-dil patients (r=0.66, P<0.001).

CONCLUSIONS

The novel evidence of a possible value of the T/E ratio as a biomarker of BAV aortopathy was presented: further validation studies are warranted.

Enhanced neointimal fibroblast, myofibroblast content and altered extracellular matrix composition: Implications in the progression of human peripheral artery restenosis

BACKGROUND AND AIMS

Neointimal cellular proliferation of fibroblasts and myofibroblasts is documented in coronary artery restenosis, however, their role in peripheral arterial disease (PAD) restenosis remains unclear. Our aim was to investigate the role of fibroblasts, myofibroblasts, and collagens in restenotic PAD.

METHODS

Nineteen PAD restenotic plaques were compared with 13 de novo plaques. Stellate cells (H&E), fibroblasts (FSP-1), myofibroblasts (α-actin/vimentin/FSP-1), cellular proliferation (Ki-67), and apoptosis (caspase-3 with poly ADP-ribose polymerase) were evaluated by immunofluorescence. Collagens were evaluated by picro-sirius red stain with polarization microscopy. Smooth muscle myosin heavy chain (SMMHC), IL-6 and TGF-β cytokines were analyzed by immunohistochemistry.

RESULTS

Restenotic plaques demonstrated increased stellate cells (2.7 ± 0.15 vs.1.3 ± 0.15) fibroblasts (2282.2 ± 85.9 vs. 906.4 ± 134.5) and myofibroblasts (18.5 ± 1.2 vs.10.6 ± 1.0) p = 0.0001 for all comparisons. In addition, fibroblast proliferation (18.4% ± 1.2 vs.10.4% ± 1.1; p = 0.04) and apoptosis (14.6% ± 1.3 vs.11.2% ± 0.6; p = 0.03) were increased in restenotic plaques. Finally, SMMHC (2.6 ± 0.12 vs.1.4 ± 0.15; p = 0.0001), type III collagen density (0.33 ± 0.06 vs. 0.17 ± 0.07; p = 0.0001), IL-6 (2.08 ± 1.7 vs.1.03 ± 2.0; p = 0.01), and TGF-β (1.80 ± 0.27 vs. 1.11 ± 0.18; p = 0.05) were increased in restenotic plaques.

CONCLUSIONS

Our study suggests proliferation and apoptosis of fibroblast and myofibroblast with associated increase in type III collagen may play a role in restenotic plaque progression. Understanding pathways involved in proliferation and apoptosis in neointimal cells, may contribute to future therapeutic interventions for the prevention of restenosis in PAD.

A novel chemo-mechano-biological model of arterial tissue growth and remodelling

Arterial growth and remodelling (G&R) is mediated by vascular cells in response to their chemical and mechanical environment. To date, mechanical and biochemical stimuli tend to be modelled separately, however this ignores their complex interplay. Here, we present a novel mathematical model of arterial chemo-mechano-biology. We illustrate its application to the development of an inflammatory aneurysm in the descending human aorta. The arterial wall is modelled as a bilayer cylindrical non-linear elastic membrane, which is internally pressurised and axially stretched. The medial degradation that accompanies aneurysm development is driven by an inflammatory response. Collagen remodelling is simulated by adaption of the natural reference configuration of constituents; growth is simulated by changes in normalised mass-densities. We account for the distribution of attachment stretches that collagen fibres are configured to the matrix and, innovatively, allow this distribution to remodel. This enables the changing functional role of the adventitia to be simulated. Fibroblast-mediated collagen growth is represented using a biochemical pathway model: a system of coupled non-linear ODEs governs the evolution of fibroblast properties and levels of key biomolecules under the regulation of Transforming Growth Factor (TGF)-β, a key promoter of matrix deposition. Given physiologically realistic targets, different modes of aneurysm development can be captured, while the predicted evolution of biochemical variables is qualitatively consistent with trends observed experimentally. Interestingly, we observe that increasing the levels of collagen-promoting TGF-β results in arrest of aneurysm growth, which seems to be consistent with experimental evidence. We conclude that this novel Chemo-Mechano-Biological (CMB) mathematical model has the potential to provide new mechanobiological insight into vascular disease progression and therapy.

RhoA determines lineage fate of mesenchymal stem cells by modulating CTGF-VEGF complex in extracellular matrix

Mesenchymal stem cells (MSCs) participate in the repair/remodelling of many tissues, where MSCs commit to different lineages dependent on the cues in the local microenvironment. Here we show that TGFβ-activated RhoA/ROCK signalling functions as a molecular switch regarding the fate of MSCs in arterial repair/remodelling after injury. MSCs differentiate into myofibroblasts when RhoA/ROCK is turned on, endothelial cells when turned off. The former is pathophysiologic resulting in intimal hyperplasia, whereas the latter is physiological leading to endothelial repair. Further analysis revealed that MSC RhoA activation promotes formation of an extracellular matrix (ECM) complex consisting of connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF). Inactivation of RhoA/ROCK in MSCs induces matrix metalloproteinase-3-mediated CTGF cleavage, resulting in VEGF release and MSC endothelial differentiation. Our findings uncover a novel mechanism by which cell–ECM interactions determine stem cell lineage specificity and offer additional molecular targets to manipulate MSC-involved tissue repair/regeneration.

It is unclear what regulates the fate of mesenchymal stem cells (MSCs) in arterial repair following injury. Here, the authors show that MSC differentiation following injury is triggered by RhoA which in turn stimulates the release of connective tissue growth factor and vascular endothelial growth factor.

Osteoprotegerin Prevents Development of Abdominal Aortic Aneurysms

Abdominal aortic aneurysms (AAAs), which commonly occur among elderly individuals, are accompanied by a risk of rupture and subsequent high mortality. Establishment of medical therapies for the prevention of AAAs requires further understanding of the molecular pathogenesis of this condition. This report details the possible involvement of Osteoprotegerin (OPG) in the prevention of AAAs through inhibition of Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In CaCl₂-induced AAA models, both internal and external diameters were significantly increased with destruction of elastic fibers in the media in Opg knockout (KO) mice, as compared to wild-type mice. Moreover, up-regulation of TRAIL expression was observed in the media by immunohistochemical analyses. Using a culture system, both the TRAIL-induced expression of matrix metalloproteinase-9 in smooth muscle cells (SMCs) and the chemoattractive effect of TRAIL on SMCs were inhibited by OPG. These data suggest that Opg may play a preventive role in the development of AAA through its antagonistic effect on Trail.

Effect of Polyelectrolyte Film Stiffness on Endothelial Cells During Endothelial-to-Mesenchymal Transition

Endothelial-to-mesenchymal transition (EndMT), during which endothelial cells (ECs) transdifferentiate into mesenchymal phenotype, plays a key role in the development of vascular implant complications such as endothelium dysfunction and in-stent restenosis. Substrate stiffness has been confirmed as a key factor to influence EC behaviors; however, so far, the relationship between substrate stiffness and EndMT has been rarely studied. Here, ECs were cultured on the (poly(L-lysine)/hyaluronate acid) (PLL/HA) multilayer films with controlled stiffness for 2 weeks, and their EndMT behaviors were studied. We demonstrated that ECs lost their markers (vWf and CD31) in a stiffness-dependent manner even without supplement of growth factors, and the softer film favored the maintaining of EC phenotype. Further, induced by transforming growth factor β1 (TGF-β1), ECs underwent EndMT, as characterized by losing their typical cobblestone morphology and markers and gaining smooth muscle cell markers (α-smooth muscle actin and calponin). Interestingly, stronger EndMT was observed when ECs were cultured on the stiffer film. Collectively, our findings suggest that substrate stiffness has significant effects on EndMT, and a softer substrate is beneficial to ECs by keeping their phenotype and inhibiting EndMT, which presents a new strategy for surface design of vascular implant materials.

Leukotriene B4 Activates Pulmonary Artery Adventitial Fibroblasts in Pulmonary Hypertension

A recent study demonstrated a significant role for leukotriene B4 (LTB4) causing pulmonary vascular remodeling in pulmonary arterial hypertension. LTB4 was found to directly injure luminal endothelial cells and promote growth of the smooth muscle cell layer of pulmonary arterioles. The purpose of this study was to determine the effects of LTB4 on the pulmonary adventitial layer, largely composed of fibroblasts. Here, we demonstrate that LTB4 enhanced human pulmonary artery adventitial fibroblast proliferation, migration, and differentiation in a dose-dependent manner through its cognate G-protein-coupled receptor, BLT1. LTB4 activated human pulmonary artery adventitial fibroblast by upregulating p38 mitogen-activated protein kinase as well as Nox4-signaling pathways. In an autoimmune model of pulmonary hypertension, inhibition of these pathways blocked perivascular inflammation, decreased Nox4 expression, reduced reactive oxygen species production, reversed arteriolar adventitial fibroblast activation, and attenuated pulmonary hypertension development. This study uncovers a novel mechanism by which LTB4 further promotes pulmonary arterial hypertension pathogenesis, beyond its established effects on endothelial and smooth muscle cells, by activating adventitial fibroblasts.

Fibrosis Related Inflammatory Mediators: Role of the IL-10 Cytokine Family

Importance of chronic fibroproliferative diseases (FDs) including pulmonary fibrosis, chronic kidney diseases, inflammatory bowel disease, and cardiovascular or liver fibrosis is rapidly increasing and they have become a major public health problem. According to some estimates about 45% of all deaths are attributed to FDs in the developed world. Independently of their etiology the common hallmark of FDs is chronic inflammation. Infiltrating immune cells, endothelial, epithelial, and other resident cells of the injured organ release an orchestra of inflammatory mediators, which stimulate the proliferation and excessive extracellular matrix (ECM) production of myofibroblasts, the effector cells of organ fibrosis. Abnormal amount of ECM disturbs the original organ architecture leading to the decline of function. Although our knowledge is rapidly expanding, we still have neither a diagnostic tool to detect nor a drug to specifically target fibrosis. Therefore, there is an urgent need for the more comprehensive understanding of the pathomechanism of fibrosis and development of novel diagnostic and therapeutic strategies. In the present review we provide an overview of the common key mediators of organ fibrosis highlighting the role of interleukin-10 (IL-10) cytokine family members (IL-10, IL-19, IL-20, IL-22, IL-24, and IL-26), which recently came into focus as tissue remodeling-related inflammatory cytokines.

Tenascin-C in development and disease of blood vessels

Tenascin-C (TNC) is an extracellular glycoprotein categorized as a matricellular protein. It is highly expressed during embryonic development, wound healing, inflammation, and cancer invasion, and has a wide range of effects on cell response in tissue morphogenesis and remodeling including the cardiovascular system. In the heart, TNC is sparsely detected in normal adults but transiently expressed at restricted sites during embryonic development and in response to injury, playing an important role in myocardial remodeling. Although TNC in the vascular system appears more complex than in the heart, the expression of TNC in normal adult blood vessels is generally low. During embryonic development, vascular smooth muscle cells highly express TNC on maturation of the vascular wall, which is controlled in a way that depends on the embryonic site of cell origin. Strong expression of TNC is also linked with several pathological conditions such as cerebral vasospasm, intimal hyperplasia, pulmonary artery hypertension, and aortic aneurysm/ dissection. TNC synthesized by smooth muscle cells in response to developmental and environmental cues regulates cell responses such as proliferation, migration, differentiation, and survival in an autocrine/paracrine fashion and in a context-dependent manner. Thus, TNC can be a key molecule in controlling cellular activity in adaptation during normal vascular development as well as tissue remodeling in pathological conditions.

Dipeptidyl peptidase-4 inhibitor decreases abdominal aortic aneurysm formation through GLP-1-dependent monocytic activity in mice

Abdominal aortic aneurysm (AAA) is a life-threatening situation affecting almost 10% of elders. There has been no effective medication for AAA other than surgical intervention. Dipeptidyl peptidase-4 (DPP-4) inhibitors have been shown to have a protective effect on cardiovascular disease. Whether DPP-4 inhibitors may be beneficial in the treatment of AAA is unclear. We investigated the effects of DPP-4 inhibitor sitagliptin on the angiotensin II (Ang II)-infused AAA formation in apoE-deficient (apoE^-/-) mice. Mice with induced AAA were treated with placebo or 2.5, 5 or 10 mg/kg/day sitagliptin. Ang II-infused apoE^-/- mice exhibited a 55.6% incidence of AAA formation, but treatment with sitagliptin decreased AAA formation. Specifically, administered sitagliptin in Ang II-infused mice exhibited decreased expansion of the suprarenal aorta, reduced elastin lamina degradation of the aorta, and diminished vascular inflammation by macrophage infiltration. Treatment with sitagliptin decreased gelatinolytic activity and apoptotic cells in aorta tissues. Sitaglipitn, additionally, was associated with increased levels of plasma active glucagon-like peptide-1 (GLP-1). In vitro studies, GLP-1 decreased reactive oxygen species (ROS) production, cell migration, and MMP-2 as well as MMP-9 activity in Ang II-stimulated monocytic cells. The results conclude that oral administration of sitagliptin can prevent abdominal aortic aneurysm formation in Ang II-infused apoE^-/-mice, at least in part, by increasing of GLP-1 activity, decreasing MMP-2 and MMP-9 production from macrophage infiltration. The results indicate that sitagliptin may have therapeutic potential in preventing the development of AAA.

Role of mechanotransduction in vascular biology: focus on thoracic aortic aneurysms and dissections

Thoracic aortic diseases that involve progressive enlargement, acute dissection, or rupture are influenced by the hemodynamic loads and mechanical properties of the wall. We have only limited understanding, however, of the mechanobiological processes that lead to these potentially lethal conditions. Homeostasis requires that intramural cells sense their local chemomechanical environment and establish, maintain, remodel, or repair the extracellular matrix to provide suitable compliance and yet sufficient strength. Proper sensing, in turn, necessitates both receptors that connect the extracellular matrix to intracellular actomyosin filaments and signaling molecules that transmit the related information to the nucleus. Thoracic aortic aneurysms and dissections are associated with poorly controlled hypertension and mutations in genes for extracellular matrix constituents, membrane receptors, contractile proteins, and associated signaling molecules. This grouping of factors suggests that these thoracic diseases result, in part, from dysfunctional mechanosensing and mechanoregulation of the extracellular matrix by the intramural cells, which leads to a compromised structural integrity of the wall. Thus, improved understanding of the mechanobiology of aortic cells could lead to new therapeutic strategies for thoracic aortic aneurysms and dissections.

Molecular mechanisms of inherited thoracic aortic disease - from gene variant to surgical aneurysm

Aortic dissection is a catastrophic event that has a high mortality rate. Thoracic aortic aneurysms are the clinically silent precursor that confers an increased risk of acute aortic dissection. There are several gene mutations that have been identified in key structural and regulatory proteins within the aortic wall that predispose to thoracic aneurysm formation. The most common and well characterised of these is the FBN1 gene mutation that is known to cause Marfan syndrome. Others less well-known mutations include TGF-β1 and TGF-β2 receptor mutations that cause Loeys-Dietz syndrome, Col3A1 mutations causing Ehlers-Danlos Type 4 syndrome and Smad3 and-4, ACTA2 and MYHII mutations that cause familial thoracic aortic aneurysm and dissection. Despite the variation in the proteins affected by these genetic mutations, there is a unifying pathological end point of medial degeneration within the wall of the aorta characterised by vascular smooth muscle cell loss, fragmentation and loss of elastic fibers, and accumulation of proteoglycans and glycosaminoglycans within vascular smooth muscle cell-depleted areas of the aortic media. Our understanding of these mutations and their post-translational effects has led to a greater understanding of the pathophysiology that underlies thoracic aortic aneurysm formation. Despite this, there are still many unanswered questions regarding the molecular mechanisms. Further elucidation of the signalling pathways will help us identify targets that may be suitable modifiers to enhance treatment of this often fatal condition.

Novel potential targets for prevention of arterial restenosis: insights from the pre-clinical research

Restenosis is the pathophysiological process occurring in 10-15% of patients submitted to revascularization procedures of coronary, carotid and peripheral arteries. It can be considered as an excessive healing reaction of the vascular wall subjected to arterial/venous bypass graft interposition, endarterectomy or angioplasty. The advent of bare metal stents, drug-eluting stents and of the more recent drug-eluting balloons, have significantly reduced, but not eliminated, the incidence of restenosis, which remains a clinically relevant problem. Biomedical research in pre-clinical animal models of (re)stenosis, despite its limitations, has contributed enormously to the identification of processes involved in restenosis progression, going well beyond the initial dogma of a primarily proliferative disease. Although the main molecular and cellular mechanisms underlying restenosis have been well described, new signalling molecules and cell types controlling the progress of restenosis are continuously being discovered. In particular, microRNAs and vascular progenitor cells have recently been shown to play a key role in this pathophysiological process. In addition, the advanced highly sensitive high-throughput analyses of molecular alterations at the transcriptome, proteome and metabolome levels occurring in injured vessels in animal models of disease and in human specimens serve as a basis to identify novel potential therapeutic targets for restenosis. Molecular analyses are also contributing to the identification of reliable circulating biomarkers predictive of post-interventional restenosis in patients, which could be potentially helpful in the establishment of an early diagnosis and therapy. The present review summarizes the most recent and promising therapeutic strategies identified in experimental models of (re)stenosis and potentially translatable to patients subjected to revascularization procedures.

Analysis of extracellular superoxide dismutase and Akt in ascending aortic aneurysm with tricuspid or bicuspid aortic valve

Ascending aortic aneurysm (AsAA) is a consequence of medial degeneration (MD), deriving from apoptotic loss of smooth muscle cells (SMC) and fragmentation of elastin and collagen fibers. Alterations of extracellular matrix structure and protein composition, typical of medial degeneration, can modulate intracellular pathways. In this study we examined the relevance of extracellular superoxide dismutase (SOD3) and Akt in AsAA pathogenesis, evaluating their tissue distribution and protein levels in ascending aortic tissues from controls (n=6), patients affected by AsAA associated to tricuspid aortic valve (TAV, n=9) or bicuspid aortic valve (BAV, n=9). The results showed a significant reduction of SOD3, phospho-Akt and Akt protein levels in AsAA tissues from patients with BAV, compared to controls, whereas the differences observed between controls and patients with TAV were not significant. The decreased levels of SOD3 and Akt in BAV aortic tissues are associated with decreased Erk1/Erk2 phosphorylation and MMP-9 levels increase. The authors suggest a role of decreased SOD3 protein levels in the progression of AsAA with BAV and a link between ECM modifications of aortic media layer and impaired Erk1/Erk2 and Akt signaling in the late stages of the aortopathy associated with BAV.

High-density lipoprotein: a novel target for antirestenosis therapy

Restenosis is an integral pathological process central to the recurrent vessel narrowing after interventional procedures. Although the mechanisms for restenosis are diverse in different pathological conditions, endothelial dysfunction, inflammation, vascular smooth muscle cell (SMC) proliferation, and myofibroblasts transition have been thought to play crucial role in the development of restenosis. Indeed, there is an inverse relationship between high-density lipoprotein (HDL) levels and risk for coronary heart disease (CHD). However, relatively studies on the direct assessment of HDL effect on restenosis are limited. In addition to involvement in the cholesterol reverse transport, many vascular protective effects of HDL, including protection of endothelium, antiinflammation, antithrombus actions, inhibition of SMC proliferation, and regulation by adventitial effects may contribute to the inhibition of restenosis, though the exact relationships between HDL and restenosis remain to be elucidated. This review summarizes the vascular protective effects of HDL, emphasizing the potential role of HDL in intimal hyperplasia and vascular remodeling, which may provide novel prophylactic and therapeutic strategies for antirestenosis.

The role of cystatin C in vascular remodeling of balloon-injured abdominal aorta of rabbits

This study aimed to evaluate the role of cystatin C (CysC) in the vascular remodeling of balloon-injured abdominal aorta of rabbits. Forty-eight New Zealand white rabbits were randomly divided into three groups: the balloon-injured injury group (n = 16), the CysC monoclonal antibody group (n = 16), and the sham-operative group (n = 16). Serum CysC levels were detected by enzyme linked immunosorbent assay. Changes in adventitial area, adventitial thickness, lumen area (LA), neointimal area (IA), internal elastic lamina area (IELA), external elastic lamina area (EELA), vascular remodeling index (VRI) and residual stenosis (RS) were measured by the Leica image analysis system. Immunohistochemical analysis of α-smooth muscle actin (α-SMA) and proliferating cell nuclear antigen (PCNA) were performed. Serum CysC levels of rabbits in the balloon-injured injury group were significantly higher than those in the CysC monoclonal antibody group and the sham-operative group (both P < 0.05). At 6 weeks after balloon injury, the adventitial area and thickness, LA, IA, IELA and EELA in the balloon-injured injury group were also higher than those in the CysC monoclonal antibody and sham-operative groups (all P < 0.05). In addition, the balloon-injured injury group showed higher VRI and RS than those of the CysC monoclonal antibody group (both P < 0.05). The positive expression of α-SMA in the vascular adventitia and media in the balloon-injured group were higher than that of the CysC monoclonal antibody and sham-operative groups. The balloon-injured group also showed a stronger expression of α-SMA in the neointima than that of the CysC monoclonal antibody group. There was a strong positive expression of PCNA in the vascular adventitia and neointima in the balloon-injured and CysC monoclonal antibody groups. However, the number of PCNA-positive cells in the balloon-injured group was higher than that of the CysC monoclonal antibody group (25.45 ± 4.21 vs. 6.75 ± 1.11, P = 0.003). Our findings provide empirical evidence that serum CysC levels may play an important role in the vascular remodeling of balloon-injured abdominal aorta of rabbits.