Aortic remodeling after transverse aortic constriction in mice is attenuated with AT1 receptor blockade

LncRNA MFRL regulates the phenotypic switch of vascular smooth muscle cells to attenuate arterial remodeling by encoding a novel micropeptide MFRLP

BACKGROUND

Arterial remodeling is a common pathophysiological change in the pathogenesis of cardiovascular diseases in which the phenotypic switch of vascular smooth muscle cells (VSMC) plays an important role. Recently, an increasing number of long non-coding RNAs(lncRNAs) have been shown to encode micropeptides that play biological roles and have great clinical transformation potential. However, the role of micropeptides encoded by lncRNAs in arterial remodeling has not been well studied and requires further exploration.

METHODS AND RESULTS

Through bioinformatic analysis and experimental verification, we found that a new lncRNA, the mitochondrial function-related lncRNA (MFRL), encodes a 64-amino acid micropeptide, MFRLP. MFRL and MFRLP play important roles in the phenotypic switch of VSMC. Further experiments showed that MFRLP interacts with mitochondrial cytochrome b to reduce accumulation of reactive oxygen species, suppress mitophagy and inhibit the VSMC switch from contractile to synthetic phenotype.

CONCLUSIONS

LncRNA MFRL encodes the micropeptide MFRLP, which interacts with mitochondrial cytochrome b to inhibit the VSMC switch from contractile to synthetic phenotype and improve arterial remodeling.

The role of oxidative stress in aortic dissection: a potential therapeutic target

The incidence of aortic dissection (AD) is steadily increasing, driven by the rising prevalence of chronic conditions such as hypertension and the global aging of the population. Oxidative stress emerges as a pivotal pathophysiological mechanism contributing to the progression of AD. Oxidative stress triggers apoptosis in vascular smooth muscle cells, reshapes the extracellular matrix (ECM), and governs ECM degradation and remodeling, subsequently impacting aortic compliance. Furthermore, oxidative stress not only facilitates the infiltration of macrophages and mononuclear lymphocytes but also disrupts the integral structure and functionality of endothelial cells, thereby inducing endothelial cell dysfunction and furthering the degeneration of the middle layer of the aortic wall. Investigating antioxidants holds promise as a therapeutic avenue for addressing AD.

The perspective of cAMP/cGMP signaling and cyclic nucleotide phosphodiesterases in aortic aneurysm and dissection

Aortic aneurysm (AA) and dissection (AD) are aortic diseases caused primarily by medial layer degeneration and perivascular inflammation. They are lethal when the rupture happens. Vascular smooth muscle cells (SMCs) play critical roles in the pathogenesis of medial degeneration, characterized by SMC loss and elastin fiber degradation. Many molecular pathways, including cyclic nucleotide signaling, have been reported in regulating vascular SMC functions, matrix remodeling, and vascular structure integrity. Intracellular cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) are second messengers that mediate intracellular signaling transduction through activating effectors, such as protein kinase A (PKA) and PKG, respectively. cAMP and cGMP are synthesized by adenylyl cyclase (AC) and guanylyl cyclase (GC), respectively, and degraded by cyclic nucleotide phosphodiesterases (PDEs). In this review, we will discuss the roles and mechanisms of cAMP/cGMP signaling and PDEs in AA/AD formation and progression and the potential of PDE inhibitors in AA/AD, whether they are beneficial or detrimental. We also performed database analysis and summarized the results showing PDEs with significant expression changes under AA/AD, which should provide rationales for future research on PDEs in AA/AD.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Animal Models, Pathogenesis, and Potential Treatment of Thoracic Aortic Aneurysm

Thoracic aortic aneurysm (TAA) has a prevalence of 0.16-0.34% and an incidence of 7.6 per 100,000 person-years, accounting for 1-2% of all deaths in Western countries. Currently, no effective pharmacological therapies have been identified to slow TAA development and prevent TAA rupture. Large TAAs are treated with open surgical repair and less invasive thoracic endovascular aortic repair, both of which have high perioperative mortality risk. Therefore, there is an urgent medical need to identify the cellular and molecular mechanisms underlying TAA development and rupture to develop new therapies. In this review, we summarize animal TAA models including recent developments in porcine and zebrafish models: porcine models can assess new therapeutic devices or intervention strategies in a large mammal and zebrafish models can employ large-scale small-molecule suppressor screening in microwells. The second part of the review covers current views of TAA pathogenesis, derived from recent studies using these animal models, with a focus on the roles of the transforming growth factor-beta (TGFβ) pathway and the vascular smooth muscle cell (VSMC)-elastin-contractile unit. The last part discusses TAA treatment options as they emerge from recent preclinical studies.

Alamandine attenuates oxidative stress in the right carotid following transverse aortic constriction in mice

OBJECTIVE

Pressure overload can result in significant changes to the structure of blood vessels, a process known as vascular remodeling. High levels of tension can cause vascular inflammation, fibrosis, and structural alterations to the vascular wall. Prior research from our team has demonstrated that the oral administration of alamandine can promote vasculoprotective effects in mice aorta that have undergone transverse aortic constriction (TAC). Furthermore, changes in local hemodynamics can affect the right and left carotid arteries differently after TAC. Thus, in this study, we aimed to assess the effects of alamandine treatment on right carotid remodeling and the expression of oxidative stress-related substances induced by TAC.

METHODS AND RESULTS

Male C57BL/6 mice were categorized into three groups: Sham, TAC, and TAC treated with alamandine (TAC+ALA). Alamandine treatment was administered orally by gavage (30 µg/kg/day), starting three days before the surgery, and continuing for a period of fourteen days. Morphometric analysis of hematoxylin and eosin-stained sections revealed that TAC induced hypertrophic and positive remodeling in the right carotid artery. Picrosirius Red staining also demonstrated an increase in total collagen deposition in the right carotid artery due to TAC-induced vascular changes. Alamandine treatment effectively prevented the increase in reactive oxygen species production and depletion of nitric oxide levels, which were induced by TAC. Finally, alamandine treatment was also shown to prevent the increased expression of nuclear factor erythroid 2-related factor 2 and 3-nitrotyrosine that were induced by TAC.

CONCLUSION

Our results suggest that alamandine can effectively attenuate pathophysiological stress in the right carotid artery of animals subjected to TAC.

Cardiac radiation improves ventricular function in mice and humans with cardiomyopathy

BACKGROUND

Rapidly dividing cells are more sensitive to radiation therapy (RT) than quiescent cells. In the failing myocardium, macrophages and fibroblasts mediate collateral tissue injury, leading to progressive myocardial remodeling, fibrosis, and pump failure. Because these cells divide more rapidly than cardiomyocytes, we hypothesized that macrophages and fibroblasts would be more susceptible to lower doses of radiation and that cardiac radiation could therefore attenuate myocardial remodeling.

METHODS

In three independent murine heart failure models, including models of metabolic stress, ischemia, and pressure overload, mice underwent 5 Gy cardiac radiation or sham treatment followed by echocardiography. Immunofluorescence, flow cytometry, and non-invasive PET imaging were employed to evaluate cardiac macrophages and fibroblasts. Serial cardiac magnetic resonance imaging (cMRI) from patients with cardiomyopathy treated with 25 Gy cardiac RT for ventricular tachycardia (VT) was evaluated to determine changes in cardiac function.

FINDINGS

In murine heart failure models, cardiac radiation significantly increased LV ejection fraction and reduced end-diastolic volume vs. sham. Radiation resulted in reduced mRNA abundance of B-type natriuretic peptide and fibrotic genes, and histological assessment of the LV showed reduced fibrosis. PET and flow cytometry demonstrated reductions in pro-inflammatory macrophages, and immunofluorescence demonstrated reduced proliferation of macrophages and fibroblasts with RT. In patients who were treated with RT for VT, cMRI demonstrated decreases in LV end-diastolic volume and improvements in LV ejection fraction early after treatment.

CONCLUSIONS

These results suggest that 5 Gy cardiac radiation attenuates cardiac remodeling in mice and humans with heart failure.

FUNDING

NIH, ASTRO, AHA, Longer Life Foundation.

The risk factors of postoperative hypoxemia in patients with Stanford type A acute aortic dissection

Hypoxemia is one of the most common complications in patients after Stanford type A acute aortic dissection surgery. The aim of this study was to investigate the association of circulating ANG II level with postoperative hypoxemia and to identify the risk factors for postoperative hypoxemia in Stanford type A acute aortic dissection patients. In this study, 88 patients who underwent Stanford type A acute aortic dissection surgery were enrolled. Postoperative hypoxemia is defined by the oxygenation index (OI). Perioperative clinical data were collected and the serum ANG II and sACE2 levels were measured. The differences in the basic characteristics, intraoperative details, biochemical parameters, laboratory test data and clinical outcomes were compared between the hypoxemia group and the non-hypoxemia group by univariate analysis. Multivariate logistic regression analysis was performed on the variables with P < .1 in univariate analysis or that were considered clinically important to identify risk factors for postoperative hypoxemia. Twenty-five patients (28.4%) were considered to have postoperative hypoxemia (OI ≤ 200 mm Hg). The ANG II concentration remained a risk factor associated with postoperative hypoxemia [OR = 1.018, 95% CI (1.003-1.034), P = .022]. The other risk factors remaining in the logistic regression model were BMI [OR = 1.417, 95% CI (1.159-1.733), P = .001] and cTnI [OR = 1.003, 95% CI (1.000-1.005), P = .032]. Elevated levels of ANG II, BMI and cTnI are risk factors for postoperative hypoxemia in patients with Stanford type A acute aortic dissection.

AGGF1 therapy inhibits thoracic aortic aneurysms by enhancing integrin α7-mediated inhibition of TGF-β1 maturation and ERK1/2 signaling

Thoracic aortic aneurysm (TAA) is a localized or diffuse dilatation of the thoracic aortas, and causes many sudden deaths each year worldwide. However, there is no effective pharmacologic therapy. Here, we show that AGGF1 effectively blocks TAA-associated arterial inflammation and remodeling in three different mouse models (mice with transverse aortic constriction, Fbn1^C1041G/+ mice, and β-aminopropionitrile-treated mice). AGGF1 expression is reduced in the ascending aortas from the three models and human TAA patients. Aggf1^+/- mice and vascular smooth muscle cell (VSMC)-specific Aggf1^smcKO knockout mice show aggravated TAA phenotypes. Mechanistically, AGGF1 enhances the interaction between its receptor integrin α7 and latency-associated peptide (LAP)-TGF-β1, blocks the cleavage of LAP-TGF-β1 to form mature TGF-β1, and inhibits Smad2/3 and ERK1/2 phosphorylation in VSMCs. Pirfenidone, a treatment agent for idiopathic pulmonary fibrosis, inhibits TAA-associated vascular inflammation and remodeling in wild type mice, but not in Aggf1^+/- mice. In conclusion, we identify an innovative AGGF1 protein therapeutic strategy to block TAA-associated vascular inflammation and remodeling, and show that efficacy of TGF-β inhibition therapies require AGGF1.

A classification approach to improve out of sample predictability of structure-based constitutive models for ascending thoracic aortic tissue

In this research, a pipeline was developed to assess the out-of-sample predictive capability of structure-based constitutive models of ascending aortic aneurysmal tissue. The hypothesis being tested is that a biomarker can help establish similarities among tissues sharing the same level of a quantifiable property, thus enabling the development of biomarker-specific constitutive models. Biomarker-specific averaged material models were constructed from biaxial mechanical tests of specimens that shared similar biomarker properties such as level of blood-wall shear stress or microfiber (elastin or collagen) degradation in the extracellular matrix. Using a cross-validation strategy commonly used in classification algorithms, biomarker-specific averaged material models were assessed in contrast to individual tissue mechanics of out of sample specimens that fell under the same category but did not contribute to the averaged model's generation. The normalized root means square errors (NRMSE) calculated on out-of-sample data were compared with average models when no categorization was performed versus biomarker-specific models and among different level of a biomarker. Different biomarker levels exhibited statistically different NRMSE when compared among each other, indicating more common features shared by the specimens belonging to the lower error groups. However, no specific biomarkers reached a significant difference when compared to the average model created when No Categorization was performed, possibly on account of unbalanced number of specimens. The method developed could allow for the screening of different biomarkers or combinations/interactions in a systematic manner leading the way to larger datasets and to more individualized constitutive approaches.

Aortic Cellular Diversity and Quantitative Genome-Wide Association Study Trait Prioritization Through Single-Nuclear RNA Sequencing of the Aneurysmal Human Aorta

BACKGROUND

Mural cells in ascending aortic aneurysms undergo phenotypic changes that promote extracellular matrix destruction and structural weakening. To explore this biology, we analyzed the transcriptional features of thoracic aortic tissue.

METHODS

Single-nuclear RNA sequencing was performed on 13 samples from human donors, 6 with thoracic aortic aneurysm, and 7 without aneurysm. Individual transcriptomes were then clustered based on transcriptional profiles. Clusters were used for between-disease differential gene expression analyses, subcluster analysis, and analyzed for intersection with genetic aortic trait data.

RESULTS

We sequenced 71 689 nuclei from human thoracic aortas and identified 14 clusters, aligning with 11 cell types, predominantly vascular smooth muscle cells (VSMCs) consistent with aortic histology. With unbiased methodology, we found 7 vascular smooth muscle cell and 6 fibroblast subclusters. Differentially expressed genes analysis revealed a vascular smooth muscle cell group accounting for the majority of differential gene expression. Fibroblast populations in aneurysm exhibit distinct behavior with almost complete disappearance of quiescent fibroblasts. Differentially expressed genes were used to prioritize genes at aortic diameter and distensibility genome-wide association study loci highlighting the genes JUN, LTBP4 (latent transforming growth factor beta-binding protein 1), and IL34 (interleukin 34) in fibroblasts, ENTPD1, PDLIM5 (PDZ and LIM domain 5), ACTN4 (alpha-actinin-4), and GLRX in vascular smooth muscle cells, as well as LRP1 in macrophage populations.

CONCLUSIONS

Using nuclear RNA sequencing, we describe the cellular diversity of healthy and aneurysmal human ascending aorta. Sporadic aortic aneurysm is characterized by differential gene expression within known cellular classes rather than by the appearance of novel cellular forms. Single-nuclear RNA sequencing of aortic tissue can be used to prioritize genes at aortic trait loci.

Inhibition of the Renin-Angiotensin System Fails to Suppress β-Aminopropionitrile-Induced Thoracic Aortopathy in Mice-Brief Report

BACKGROUND

Cross-linking of lysine residues in elastic and collagen fibers is a vital process in aortic development. Inhibition of lysyl oxidase by BAPN (β-aminopropionitrile) leads to thoracic aortopathies in mice. Although the renin-angiotensin system contributes to several types of thoracic aortopathies, it remains unclear whether inhibition of the renin-angiotensin system protects against aortopathy caused by the impairment of elastic fiber/collagen crosslinking.

METHODS

BAPN (0.5% wt/vol) was started in drinking water to induce aortopathies in male C57BL/6J mice at 4 weeks of age for 4 weeks. Five approaches were used to investigate the impact of the renin-angiotensin system. Bulk RNA sequencing was performed to explore potential molecular mechanisms of BAPN-induced thoracic aortopathies.

RESULTS

Losartan increased plasma renin concentrations significantly, compared with vehicle-infused mice, indicating effective angiotensin II type 1 receptor inhibition. However, losartan did not suppress BAPN-induced aortic rupture and dilatation. Since losartan is a surmountable inhibitor of the renin-angiotensin system, irbesartan, an insurmountable inhibitor, was also tested. Although increased plasma renin concentrations indicated effective inhibition, irbesartan did not ameliorate aortic rupture and dilatation in BAPN-administered mice. Thus, BAPN-induced thoracic aortopathies were refractory to angiotensin II type 1 receptor blockade. Next, we inhibited angiotensin II production by pharmacological or genetic depletion of AGT (angiotensinogen), the unique precursor of angiotensin II. However, neither suppressed BAPN-induced thoracic aortic rupture and dilatation. Aortic RNA sequencing revealed molecular changes during BAPN administration that were distinct from other types of aortopathies in which angiotensin II type 1 receptor inhibition protects against aneurysm formation.

CONCLUSIONS

Inhibition of either angiotensin II action or production of the renin-angiotensin system does not attenuate BAPN-induced thoracic aortopathies in mice.

Intracellular signaling control of mechanical homeostasis in the aorta

Mature arteries exhibit a preferred biomechanical state in health evidenced by a narrow range of intramural and wall shear stresses. When stresses are perturbed by changes in blood pressure or flow, homeostatic mechanisms tend to restore target values via altered contractility and/or cell and matrix turnover. In contrast, vascular disease associates with compromised homeostasis, hence we must understand mechanisms underlying mechanical homeostasis and its robustness. Here, we use a multiscale computational model wherein mechanosensitive intracellular signaling pathways drive arterial growth and remodeling. First, we identify an ensemble of cell-level parameterizations where tissue-level responses are well-regulated and adaptive to hemodynamic perturbations. The responsible mechanism is persistent multiscale negative feedback whereby mechanosensitive signaling drives mass turnover until homeostatic target stresses are reached. This demonstrates how robustness emerges despite inevitable cell and individual heterogeneity. Second, we investigate tissue-level effects of signaling node knockdowns (ATIR, ROCK, TGF[Formula: see text]RII, PDGFR, ERK1/2) and find general agreement with experimental reports of fault tolerance. Robustness against structural changes manifests via low engagement of the node under baseline stresses or compensatory multiscale feedback via upregulation of additional pathways. Third, we show how knockdowns affect collagen and smooth muscle turnover at baseline and with perturbed stresses. In several cases, basal production is not remarkably affected, but sensitivities to stress deviations, which influence feedback strength, are reduced. Such reductions can impair adaptive responses, consistent with previously reported aortic vulnerability despite grossly normal appearances. Reduced stress sensitivities thus form a candidate mechanism for how robustness is lost, enabling transitions from health towards disease.

Embryonic Heterogeneity of Smooth Muscle Cells in the Complex Mechanisms of Thoracic Aortic Aneurysms

Smooth muscle cells (SMCs) are the major cell type of the aortic wall and play a pivotal role in the pathophysiology of thoracic aortic aneurysms (TAAs). TAAs occur in a region-specific manner with the proximal region being a common location. In this region, SMCs are derived embryonically from either the cardiac neural crest or the second heart field. These cells of distinct origins reside in specific locations and exhibit different biological behaviors in the complex mechanism of TAAs. The purpose of this review is to enhance understanding of the embryonic heterogeneity of SMCs in the proximal thoracic aorta and their functions in TAAs.

Single-Cell Analysis of Aneurysmal Aortic Tissue in Patients with Marfan Syndrome Reveals Dysfunctional TGF-β Signaling

The molecular and cellular processes leading to aortic aneurysm development in Marfan syndrome (MFS) remain poorly understood. In this study, we examined the changes of aortic cell populations and gene expression in MFS by performing single-cell RNA sequencing (scRNA seq) on ascending aortic aneurysm tissues from patients with MFS (n = 3) and age-matched non-aneurysmal control tissues from cardiac donors and recipients (n = 4). The expression of key molecules was confirmed by immunostaining. We detected diverse populations of smooth muscle cells (SMCs), fibroblasts, and endothelial cells (ECs) in the aortic wall. Aortic tissues from MFS showed alterations of cell populations with increased de-differentiated proliferative SMCs compared to controls. Furthermore, there was a downregulation of MYOCD and MYH11 in SMCs, and an upregulation of COL1A1/2 in fibroblasts in MFS samples compared to controls. We also examined TGF-β signaling, an important pathway in aortic homeostasis. We found that TGFB1 was significantly upregulated in two fibroblast clusters in MFS tissues. However, TGF-β receptor genes (predominantly TGFBR2) and SMAD genes were downregulated in SMCs, fibroblasts, and ECs in MFS, indicating impairment in TGF-β signaling. In conclusion, despite upregulation of TGFB1, the rest of the canonical TGF-β pathway and mature SMCs were consistently downregulated in MFS, indicating a potential compromise of TGF-β signaling and lack of stimulus for SMC differentiation.

Feasibility of Bilinear Mechanical Characterization of the Abdominal Aorta in a Hypertensive Mouse Model

A change in elastin and collagen content is indicative of damage caused by hypertension, which changes the non-linear behavior of the vessel wall. This study was aimed at investigating the feasibility of monitoring the non-linear material behavior in an angiotensin II hypertensive mice model. Aortas from 13 hypertensive mice were imaged with pulse wave imaging (PWI) over 4 wk using a 40-MHz linear array. The pulse wave velocity was estimated using two wave features: (i) the maximum axial acceleration of the foot (PWV_dia) and (ii) the maximum axial acceleration of the dicrotic notch (PWV_end-sys). The Bramwell-Hill equation was used to derive the compliance at diastolic and end-systolic pressure. This study determined the potential of PWI in a hypertensive mouse model to image and quantify the non-linear material behavior in vivo. End-systolic compliance could differentiate between the sham and angiotensin II groups, whereas diastolic compliance could not, indicating that PWI can detect early collagen-dominated remodeling.

Reduced Smooth Muscle Contractile Capacity Facilitates Maladaptive Arterial Remodeling

Albeit seldom considered explicitly, the vasoactive state of a central artery can contribute significantly to the in vivo values of flow-induced wall shear stress and pressure-induced wall stress, which in turn are strong determinants of wall growth and remodeling. In this technical brief, we test the hypothesis that diminished vasoactive capacity compromises effective mechano-adaptations of central arteries. Toward this end, we use consistent methods to re-interpret previously published data on carotid artery remodeling in a common mouse model of induced hypertension and a separate model of connective tissue disease that results in Marfan syndrome. Animals have identical backgrounds and in both cases, the data are consistent with the hypothesis considered. In particular, individual carotid arteries with strong (normal) vasoactive capacity tend to maintain wall thickness and in vivo axial stress closer to homeostatic, thus resulting in passive circumferential wall stress and energy storage closer to normal values. We conclude, therefore, that effective vasoactivity helps to control the biomechanical state in which cells and matrix turnover, thus helping to delineate mechano-adaptive from maladaptive remodeling. Future analyses of experimental data and computational models of growth and remodeling should account for this strong coupling between smooth muscle contractile capacity and central arterial remodeling.

A neutralizing IL-11 antibody reduces vessel hyperplasia in a mouse carotid artery wire injury model

Vascular restenosis remains a major problem in patients with coronary artery disease (CAD) and peripheral artery disease (PAD). Neointimal hyperplasia, defined by post-procedure proliferation and migration of vascular smooth muscle cells (VSMCs) is a key underlying pathology. Here we investigated the role of Interleukin 11 (IL-11) in a mouse model of injury-related plaque development. Apoe^-/- mice were fed a hyperlipidaemic diet and subjected to carotid wire injury of the right carotid. Mice were injected with an anti-IL11 antibody (X203), IgG control antibody or buffer. We performed ultrasound analysis to assess vessel wall thickness and blood velocity. Using histology and immunofluorescence approaches, we determined the effects of IL-11 inhibition on VSMC and macrophages phenotypes and fibrosis. Treatment of mice with carotid wire injury using X203 significantly reduced post-endothelial injury vessel wall thickness, and injury-related plaque, when compared to control. Immunofluorescence staining of the injury-related plaque showed that X203 treatment did not reduce macrophage numbers, but reduced the number of VSMCs and lowered matrix metalloproteinase 2 (MMP2) levels and collagen content in comparison to control. X203 treatment was associated with a significant increase in smooth muscle protein 22α (SM22α) positive cells in injury-related plaque compared to control, suggesting preservation of the contractile VSMC phenotype. Interestingly, X203 also reduced the collagen content of uninjured carotid arteries as compared to IgG, showing an additional effect on hyperlipidemia-induced arterial remodeling in the absence of mechanical injury. Therapeutic inhibition of IL-11 reduced vessel wall thickness, attenuated neointimal hyperplasia, and has favorable effects on vascular remodeling following wire-induced endothelial injury. This suggests IL-11 inhibition as a potential novel therapeutic approach to reduce arterial stenosis following revascularization in CAD and PAD patients.

Deletion of AT1a (Angiotensin II Type 1a) Receptor or Inhibition of Angiotensinogen Synthesis Attenuates Thoracic Aortopathies in Fibrillin1C1041G/+ Mice

Objective: A cardinal feature of Marfan syndrome is thoracic aortic aneurysm. The contribution of the renin-angiotensin system via AT1aR (Ang II [angiotensin II] receptor type 1a) to thoracic aortic aneurysm progression remains controversial because the beneficial effects of angiotensin receptor blockers have been ascribed to off-target effects. This study used genetic and pharmacological modes of attenuating angiotensin receptor and ligand, respectively, to determine their roles on thoracic aortic aneurysm in mice with fibrillin-1 haploinsufficiency (Fbn1C1041G/+). Approach and Results: Thoracic aortic aneurysm in Fbn1C1041G/+ mice was found to be strikingly sexual dimorphic. Males displayed aortic dilation over 12 months while aortic dilation in Fbn1C1041G/+ females did not differ significantly from wild-type mice. To determine the role of AT1aR, Fbn1C1041G/+ mice that were either +/+ or -/- for AT1aR were generated. AT1aR deletion reduced expansion of ascending aorta and aortic root diameter from 1 to 12 months of age in males. Medial thickening and elastin fragmentation were attenuated. An antisense oligonucleotide against angiotensinogen was administered to male Fbn1C1041G/+ mice to determine the effects of Ang II depletion. Antisense oligonucleotide against angiotensinogen administration attenuated dilation of the ascending aorta and aortic root and reduced extracellular remodeling. Aortic transcriptome analyses identified potential targets by which inhibition of the renin-angiotensin system reduced aortic dilation in Fbn1C1041G/+ mice. Conclusions: Deletion of AT1aR or inhibition of Ang II production exerted similar effects in attenuating pathologies in the proximal thoracic aorta of male Fbn1C1041G/+ mice. Inhibition of the renin-angiotensin system attenuated dysregulation of genes within the aorta related to pathology of Fbn1C1041G/+ mice.

Excessive adventitial stress drives inflammation-mediated fibrosis in hypertensive aortic remodelling in mice

Hypertension induces significant aortic remodelling, often adaptive but sometimes not. To identify immuno-mechanical mechanisms responsible for differential remodelling, we studied thoracic aortas from 129S6/SvEvTac and C57BL/6 J mice before and after continuous 14-day angiotensin II infusion, which elevated blood pressure similarly in both strains. Histological and biomechanical assessments of excised vessels were similar at baseline, suggesting a common homeostatic set-point for mean wall stress. Histology further revealed near mechano-adaptive remodelling of the hypertensive 129S6/SvEvTac aortas, but a grossly maladaptive remodelling of C57BL/6 J aortas. Bulk RNA sequencing suggested that increased smooth muscle contractile processes promoted mechano-adaptation of 129S6/SvEvTac aortas while immune processes prevented adaptation of C57BL/6 J aortas. Functional studies confirmed an increased vasoconstrictive capacity of the former while immunohistochemistry demonstrated marked increases in inflammatory cells in the latter. We then used multiple computational biomechanical models to test the hypothesis that excessive adventitial wall stress correlates with inflammatory cell infiltration. These models consistently predicted that increased vasoconstriction against an increased pressure coupled with modest deposition of new matrix thickens the wall appropriately, restoring wall stress towards homeostatic consistent with adaptive remodelling. By contrast, insufficient vasoconstriction permits high wall stresses and exuberant inflammation-driven matrix deposition, especially in the adventitia, reflecting compromised homeostasis and gross maladaptation.

Contribution of PDGFRα-positive cells in maintenance and injury responses in mouse large vessels

The maladaptive remodeling of vessel walls with neointima formation is a common feature of proliferative vascular diseases. It has been proposed that neointima formation is caused by the dedifferentiation of mature smooth muscle cells (SMCs). Recent evidence suggests that adventitial cells also participate in neointima formation; however, their cellular dynamics are not fully understood. In this study, we utilized a lineage tracing model of platelet-derived growth factor receptor alpha (PDGFRa) cells and examined cellular behavior during homeostasis and injury response. PDGFRa marked adventitial cells that were largely positive for Sca1 and a portion of medial SMCs, and both cell types were maintained for 2 years. Upon carotid artery ligation, PDGFRa-positive (+) cells were slowly recruited to the neointima and exhibited an immature SMC phenotype. In contrast, in a more severe wire denudation injury, PDGFRa+ cells were recruited to the neointima within 14 days and fully differentiated into SMCs. Under pressure overload induced by transverse aortic constriction, PDGFRa+ cells developed marked adventitial fibrosis. Taken together, our observations suggest that PDGFRa+ cells serve as a reservoir of adventitial cells and a subset of medial SMCs and underscore their context-dependent response to vascular injuries.

Antibody-mediated neutralization of IL11 signalling reduces ERK activation and cardiac fibrosis in a mouse model of severe pressure overload

Interleukin-11 (IL11) is important for fibroblast-to-myofibroblast transformations. Here, we examined the signalling and phenotypic effects of inhibiting IL11 signalling using neutralizing antibodies against IL11 or its cognate receptor (IL11RA) in a mouse model of acute and severe pressure overload. C57BL/6J mice underwent ascending aortic constriction (AAC) surgery and were randomized to anti-IL11, anti-IL11RA, or isotype control antibodies (20 mg/kg, bi-weekly for 2 weeks). AAC surgery induced the expression of IL11, IL11RA and extracellular matrix (ECM) genes that was associated with cardiac hypertrophy and aortic remodelling. Inhibition of IL11 signalling reduced AAC-induced cardiac fibrosis and ECM gene expression as well as ERK1/2 phosphorylation but had no effect on cardiac hypertrophy. STAT3 was phosphorylated in the hearts of AAC-treated mice but this was unrelated to IL11 activity, which we confirmed in mouse cardiac fibroblasts in vitro. These data highlight that blocking IL11 signalling reduces cardiac fibrosis due to severe pressure overload and suggests ERK, but not STAT3, activity as the relevant underlying signalling pathway.

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.

Alamandine improves cardiac remodeling induced by transverse aortic constriction in mice

Alamandine is the newest identified peptide of the renin-angiotensin system (RAS) and has protective effects in the cardiovascular system. Although the involvement of classical RAS components in the genesis and progression of cardiac remodeling is well known, less is known about the effects of alamandine. Therefore, in the present study we investigated the effects of alamandine on cardiac remodeling induced by transverse aortic constriction (TAC) in mice. Male mice (C57BL/6), 10-12 wk of age, were divided into three groups: sham operated, TAC, and TAC + ALA (30 µg/kg/day alamandine for 14 days). The TAC surgery was performed under ketamine and xylazine anesthesia. At the end of treatment, the animals were submitted to echocardiographic examination and subsequently euthanized for tissue collection. TAC induced myocyte hypertrophy, collagen deposition, and the expression of matrix metalloproteinase (MMP)-2 and transforming growth factor (TGF)-β in the left ventricle. These markers of cardiac remodeling were reduced by oral treatment with alamandine. Western blotting analysis showed that alamandine prevents the increase in ERK1/2 phosphorylation and reverts the decrease in 5'-adenosine monophosphate-activated protein kinase (AMPK)α phosphorylation induced by TAC. Although both TAC and TAC + ALA increased SERCA2 expression, the phosphorylation of phospholamban in the Thr17 residue was increased solely in the alamandine-treated group. The echocardiographic data showed that there are no functional or morphological alterations after 2 wk of TAC. Alamandine treatment prevents myocyte hypertrophy and cardiac fibrosis induced by TAC. Our results reinforce the cardioprotective role of alamandine and highlight its therapeutic potential for treating heart diseases related to pressure overload conditions.NEW & NOTEWORTHY Alamandine is the newest identified component of the renin-angiotensin system protective arm. Considering the beneficial effects already described so far, alamandine is a promising target for cardiovascular disease treatment. We demonstrated for the first time that alamandine improves many aspects of cardiac remodeling induced by pressure overload, including cell hypertrophy, fibrosis, and oxidative stress markers.

Mechanisms of Vascular Remodeling in Hypertension

Hypertension is both a cause and a consequence of central artery stiffening, which in turn is an initiator and indicator of myriad disease conditions and thus all-cause mortality. Such stiffening results from a remodeling of the arterial wall that is driven by mechanical stimuli and mediated by inflammatory signals, which together lead to differential gene expression and concomitant changes in extracellular matrix composition and organization. This review focuses on biomechanical mechanisms by which central arteries remodel in hypertension within the context of homeostasis-what promotes it, what prevents it. It is suggested that the vasoactive capacity of the wall and inflammatory burden strongly influence the ability of homeostatic mechanisms to adapt the arterial wall to high blood pressure or not. Maladaptation, often reflected by inflammation-driven adventitial fibrosis, not just excessive intimal-medial thickening, significantly diminishes central artery function and disturbs hemodynamics, ultimately compromising end organ perfusion and thus driving the associated morbidity and mortality. It is thus suggested that there is a need for increased attention to controlling both smooth muscle phenotype and inflammation in hypertensive remodeling of central arteries, with future studies of the often adaptive response of medium-sized muscular arteries promising to provide additional guidance.

Identification of Transcriptional Variation in Aortic Remodeling Using a Murine Transverse Aortic Constriction (TAC) Model

Arterial remodeling is a major pathological consequence of hypertension, which is recognized as the most common chronic non-communicable disease. However, the detailed mechanism of how arterial remodeling is induced by hypertension has not yet been fully elucidated. Evaluating the transcriptional changes in arterial tissue in response to elevated blood pressure at an early stage may provide new insights and identify novel therapeutic candidates in preventing arterial remodeling. Here, we used the ascending aorta of the transverse aortic constriction (TAC) model to induce arterial remodeling in C57BL/6 male mice. Age-matched mice were subjected to sham surgery as controls. The TAC model was only considered successful if the mice conformed to the criteria (RC/LC blood flow velocity with 5–10-fold change) 1 week after the surgery. Two weeks after surgery, the ascending aorta developed severe remodeling in TAC mice as compared to the sham group. High throughput sequencing was then applied to identify differentially expressed (DE) transcripts. In silicon analysis were then performed to systematically network transcriptional changes. A total of 1,019 mRNAs were significantly changed between TAC and the sham group at the transcriptional level. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis revealed that stress/stimulus/immune-related biological processes played a crucial role during arterial remodeling. Our data provide a comprehensive understanding of global gene expression changes in the TAC model, which suggests that targeting inflammation and vascular smooth cell transformation are potential therapeutic strategies to interfere with the aortic remodeling at an early stage in the development of hypertension.

Interleukin-11 is important for vascular smooth muscle phenotypic switching and aortic inflammation, fibrosis and remodeling in mouse models

Transforming growth factor beta-1 (TGFβ1) is a major driver of vascular smooth muscle cell (VSMC) phenotypic switching, an important pathobiology in arterial disease. We performed RNA-sequencing of TGFβ1-stimulated human aortic or arterial VSMCs which revealed large and consistent upregulation of Interleukin 11 (IL11). IL11 has an unknown function in VSMCs, which highly express the IL11 receptor alpha, suggestive of an autocrine loop. In vitro, IL11 activated ERK signaling, but inhibited STAT3 activity, and caused VSMC phenotypic switching to a similar extent as TGFβ1 or angiotensin II (ANGII) stimulation. Genetic or therapeutic inhibition of IL11 signaling reduced TGFβ1- or ANGII-induced VSMC phenotypic switching, placing IL11 activity downstream of these factors. Aortas of mice with Myh11-driven IL11 expression were remodeled and had reduced contractile but increased matrix and inflammatory genes expression. In two models of arterial pressure loading, IL11 was upregulated in the aorta and neutralizing IL11 antibodies reduced remodeling along with matrix and pro-inflammatory gene expression. These data show that IL11 plays an important role in VSMC phenotype switching, vascular inflammation and aortic pathobiology.

Histone Deacetylase Inhibition Attenuates Aortic Remodeling in Rats under Pressure Overload

The use of histone deacetylase (HDAC) inhibitor is a novel therapeutic strategy for cardiovascular disease. Studies have shown that many HDAC inhibitors have the ability to reduce the aortic remodeling in various animal models. We hypothesized that the HDAC inhibitor, MGCD0103 (MGCD), attenuates aortic remodeling in rats under pressure overload-induced by transverse aortic constriction (TAC). The aortic ring tension analysis was conducted using the thoracic aorta. Sections of the aorta were visualized after hematoxylin and eosin, trichrome, and Verhoeff-van Gieson staining, and immunohistochemistry. The expression of genes related to aortic remodeling (αSMA, Mmp2, and Mmp9) and angiotensin receptors (Agtr1 and Agtr2) was determined by quantitative real-time polymerase chain reaction. There was a significant decrease in relaxation of the aorta when treated with MGCD. Fibrosis of the aortic wall and expression of angiotensin receptors increased in TAC rats, which was attenuated by MGCD. These results indicate that MGCD, an HDAC inhibitor, attenuates aortic remodeling in rats with TAC-induced pressure overload rats and may serve as a potential therapeutic target of antiaortic remodeling in pressure overload-induced hypertension-related diseases.

Aortic remodeling is modest and sex-independent in mice when hypertension is superimposed on aging

OBJECTIVES

Increased central artery stiffness associates with cardiovascular disease. Among other factors, hypertension and aging are strong contributors to central artery stiffening, yet it has been difficult to separate their effects. Herein, we study isolated and combined effects of hypertension and aging on central artery remodeling in multiple mouse models as a function of sex.

METHODS

We biomechanically phenotyped the aorta as a function of two different methods of inducing hypertension [infusion of angiotensin II (AngII) or combining a high salt diet with inhibition of endothelial-derived nitric oxide synthase using L-NAME] in male and female wild-type and fibulin-5 null mice, the latter of which models aspects of aortic aging.

RESULTS

Despite increasing blood pressure similarly, salt + L-NAME led to adaptive and maladaptive remodeling in the abdominal and thoracic aorta, respectively, whereas AngII caused luminal dilatation but little remodeling of the wall. Importantly, effects of aging were more dramatic than those resulting from induced hypertension and, consequently, superimposing hypertension on aging led to modest additional changes in luminal radius and wall thickness, though wall stress and stiffness increased mainly because of the elevated pressure.

CONCLUSION

Our results suggest that effects of hypertension on aortic remodeling are modest when superimposed on aging in mice, largely independent of sex. These findings are consistent with general observations in humans and in spontaneously hypertensive rats, though separated here for the first time in a rodent model characterized by a severe loss of elastic fiber integrity similar to that found in the aged human aorta.

Endogenous hydrogen sulfide improves vascular remodeling through PPARδ/SOCS3 signaling

Introduction

Mounting evidences demonstrated the deficiency of hydrogen sulfide (H₂S) facilitated the progression of cardiovascular diseases. However, the exact effects of H₂S on vascular remodeling are not consistent.

Objectives

This study aimed to investigate the beneficial role of endogenous H₂S on vascular remodeling.

Methods

CSE inhibitor, DL-propargylglycine (PPG) was used to treat mice and vascular smooth muscle cells (VSMCs). Sodium hydrosulfide (NaHS) was given to provide hydrogen sulfide. Vascular tension, H&E staining, masson trichrome staining, western blot and CCK8 were used to determine the vascular remodeling, expressions of inflammatory molecules and proliferation of VSMCs.

Results

The deficiency of endogenous H₂S generated vascular remodeling with aggravated active and passive contraction, thicken aortic walls, collagen deposition, increased phosphorylation of STAT3, decreased production of PPARδ and SOCS3 in aortas, which were reversed by NaHS. PPG inhibited expression of PPARδ and SOCS3, stimulated the phosphorylation of STAT3, increased inflammatory molecules production and proliferation rate of VSMCs which could all be corrected by NaHS supply. PPARδ agonist GW501516 offered protections similar to NaHS in PPG treated VSMCs. Aggravated active and passive contraction in PPG mice aortas, upregulated p-STAT3 and inflammatory molecules, downregulated SOCS3 and phenotype transformation in PPG treated VSMCs could be corrected by PPARδ agonist GW501516 treatment. On the contrary, PPARδ antagonist GSK0660 exhibited opposite effects on vascular contraction in aortas, expressions of p-STAT3 and SOCS3 in VSMCs compared with GW501516.

Conclusion

In a word, endogenous H₂S protected against vascular remodeling through preserving PPARδ/SOCS3 anti-inflammatory signaling pathway. Deficiency of endogenous H₂S should be considered as a risk factor for VSMCs dysfunction.

Involvement of Angiotensin II Type 1 Receptor and Calcium Channel in Vascular Remodeling and Endothelial Dysfunction in Rats with Pressure Overload

Vascular remodeling is an adaptive response to various stimuli, including mechanical forces, inflammatory cytokines and hormones. In the present study, we investigated the role of angiotensin II type 1 receptor (AT1R) and calcium channel in carotid artery remodeling in response to increased biomechanical forces by using the transverse aortic constriction (TAC) rat model. TAC was induced on ten-week-old male Sprague-Dawley rats and these models were treated with AT1R blocker olmesartan (1 mg/kg/day) or/and calcium channel blocker (CCB) amlodipine (0.5 mg/kg/day) for 14 days. After the treatment, the right common carotid artery proximal to the band (RCCA-B) was collected for further assay. Results showed that olmesartan, but not amlodipine, significantly prevented TAC-induced adventitial hyperplasia. Similarly, olmesartan, but not amlodipine, signifcantly prevented vascular infammation, as indicated by increased tumor necrosis factor α (TNF-α) and increased p65 phosphorylation, an indicator of nuclear factor κ-light-chain-enhancer of activated B cells (NFκB) activation in RCCA-B. In contrast, both olmesartan and amlodipine reversed the decreased expression of endothelial nitric oxidase synthase (eNOS) and improved endothelium-dependent vasodilation, whereas combination of olmesartan and amlodipine showed no further synergistic protective effects. These results suggest that AT1R was involved in vascular remodeling and inflammation in response to pressure overload, whereas AT1R and subsequent calcium channel were involved in endothelial dysfunction.

Aortic Aneurysms and Dissections Series: Part II: Dynamic Signaling Responses in Aortic Aneurysms and Dissections

Aortic structure and function are controlled by the coordinated actions of different aortic cells and the extracellular matrix. Several pathways have been identified that control the aortic wall in a cell-type-specific manner and play diverse roles in various phases of aortic injury, repair, and remodeling. This complexity of signaling in the aortic wall poses challenges to the development of therapeutic strategies for treating aortic aneurysms and dissections. Here, in part II of this Recent Highlights series on aortic aneurysms and dissections, we will summarize recent studies published in Arteriosclerosis, Thrombosis, and Vascular Biology that have contributed to our knowledge of the signaling pathway-related mechanisms of aortic aneurysms and dissections.

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.

Therapies for Thoracic Aortic Aneurysms and Acute Aortic Dissections

Thoracic aortic aneurysms that progress to acute aortic dissections are often fatal. Thoracic aneurysms have been managed with treatment with β-adrenergic blocking agents (β-blockers) and routine surveillance imaging, followed by surgical repair of the aneurysm when the risk of dissection exceeds the risk for repair. Thus, there is a window to initiate therapies to slow aortic enlargement and delay or ideally negate the need for surgical repair of the aneurysm to prevent a dissection. Mouse models of Marfan syndrome-a monogenic disorder predisposing to thoracic aortic disease-have been used extensively to identify such therapies. The initial finding that TGFβ (transformation growth factor-β) signaling was increased in the aortic media of a Marfan syndrome mouse model and that its inhibition via TGFβ neutralization or At1r (Ang II [angiotensin II] type I receptor) antagonism prevented aneurysm development was generally viewed as a groundbreaking discovery that could be translated into the first cure of thoracic aortic disease. However, several large randomized trials of pediatric and adult patients with Marfan syndrome have subsequently yielded no evidence that At1r antagonism by losartan slows aortic enlargement more effectively than conventional treatment with β-blockers. Subsequent studies in mouse models have begun to resolve the complex molecular pathophysiology underlying onset and progression of aortic disease and have emphasized the need to preserve TGFβ signaling to prevent aneurysm formation. This review describes critical experiments that have influenced the evolution of our understanding of thoracic aortic disease, in addition to discussing old controversies and identifying new therapeutic opportunities.

Computational Modeling Predicts Immuno-Mechanical Mechanisms of Maladaptive Aortic Remodeling in Hypertension

Uncontrolled hypertension is a major risk factor for myriad cardiovascular diseases. Among its many effects, hypertension increases central artery stiffness which in turn is both an initiator and indicator of disease. Despite extensive clinical, animal, and basic science studies, the biochemomechanical mechanisms by which hypertension drives aortic stiffening remain unclear. In this paper, we show that a new computational model of aortic growth and remodeling can capture differential effects of induced hypertension on the thoracic and abdominal aorta in a common mouse model of disease. Because the simulations treat the aortic wall as a constrained mixture of different constituents having different material properties and rates of turnover, one can gain increased insight into underlying constituent-level mechanisms of aortic remodeling. Model results suggest that the aorta can mechano-adapt locally to blood pressure elevation in the absence of marked inflammation, but large increases in inflammation drive a persistent maladaptive phenotype characterized primarily by adventitial fibrosis. Moreover, this fibrosis appears to occur via a marked increase in the rate of deposition of collagen having different material properties in the absence of a compensatory increase in the rate of matrix degradation. Controlling inflammation thus appears to be key to reducing fibrosis, but therapeutic strategies should not compromise the proteolytic activity of the wall that is essential to mechanical homeostasis.

Dynamic and diverse changes in the functional properties of vascular smooth muscle cells in pulmonary hypertension

Pulmonary hypertension (PH) is the end result of interaction between pulmonary vascular tone and a complex series of cellular and molecular events termed 'vascular remodelling'. The remodelling process, which can involve the entirety of pulmonary arterial vasculature, almost universally involves medial thickening, driven by increased numbers and hypertrophy of its principal cellular constituent, smooth muscle cells (SMCs). It is noted, however that SMCs comprise heterogeneous populations of cells, which can exhibit markedly different proliferative, inflammatory, and extracellular matrix production changes during remodelling. We further consider that these functional changes in SMCs of different phenotype and their role in PH are dynamic and may undergo significant changes over time (which we will refer to as cellular plasticity); no single property can account for the complexity of the contribution of SMC to pulmonary vascular remodelling. Thus, the approaches used to pharmacologically manipulate PH by targeting the SMC phenotype(s) must take into account processes that underlie dominant phenotypes that drive the disease. We present evidence for time- and location-specific changes in SMC proliferation in various animal models of PH; we highlight the transient nature (rather than continuous) of SMC proliferation, emphasizing that the heterogenic SMC populations that reside in different locations along the pulmonary vascular tree exhibit distinct responses to the stresses associated with the development of PH. We also consider that cells that have often been termed 'SMCs' may arise from many origins, including endothelial cells, fibroblasts and resident or circulating progenitors, and thus may contribute via distinct signalling pathways to the remodelling process. Ultimately, PH is characterized by long-lived, apoptosis-resistant SMC. In line with this key pathogenic characteristic, we address the acquisition of a pro-inflammatory phenotype by SMC that is essential to the development of PH. We present evidence that metabolic alterations akin to those observed in cancer cells (cytoplasmic and mitochondrial) directly contribute to the phenotype of the SM and SM-like cells involved in PH. Finally, we raise the possibility that SMCs transition from a proliferative to a senescent, pro-inflammatory and metabolically active phenotype over time.

Reversal of Aortic Enlargement Induced by Increased Biomechanical Forces Requires AT1R Inhibition in Conjunction With AT2R Activation

Objective- Pharmacological inhibition of the AT1R (angiotensin II type 1 receptor) with losartan can attenuate ascending aortic remodeling induced by transverse aortic constriction (TAC). In this study, we investigated the role of the AT2R (angiotensin II type 2 receptor) and MasR (Mas receptor) in TAC-induced ascending aortic dilation and remodeling. Approach and Results- Wild-type C57BL/6J mice were subjected to sham or TAC surgeries in the presence and absence of various drugs. Aortic diameters were assessed by echocardiography, central blood pressure was measured in the ascending aorta 2 weeks post-operation, and histology and gene expression analyses completed. An angiotensin-converting enzyme inhibitor, captopril, decreased systolic blood pressure to the same level as losartan but did not attenuate aortic dilation, adventitial inflammation, medial collagen deposition, elastin breakage, or Mmp9 (matrix metalloproteinase-9) expression when compared with TAC mice. In contrast, co-administration of captopril with an AT2R agonist, compound 21, attenuated aortic dilation, medial collagen content, elastin breaks, and Mmp9 expression, whereas co-administration of captopril with a MasR agonist (AVE0991) did not reverse aortic dilation and led to aberrant aortic remodeling. An AT2R antagonist, PD123319, reversed the protective effects of losartan in TAC mice. Treatment with compound 21 alone showed no effect on TAC-induced aortic enlargement, blood pressure, elastin breakage, or Mmp9 expression. Conclusions- Our data indicate that when AT1R signaling is blocked, AT2R activation is a key modulator to prevent aortic dilation that occurs with TAC. These data suggest that angiotensin-converting enzyme inhibitor may not be as effective as losartan for slowing aneurysm growth because losartan requires intact AT2R signaling to prevent aortic enlargement.

Alamandine attenuates arterial remodelling induced by transverse aortic constriction in mice

Aims: The renin-angiotensin system (RAS) plays an important role in the pathophysiology of vascular diseases, especially as a mediator of inflammation and tissue remodelling. Alamandine (Ala¹-angiotensin-(1-7)) is a new biologically active peptide from the RAS, interacting with Mas-related G-protein-coupled receptor member D. Although a growing number of studies reveal the cardioprotective effects of alamandine, there is a paucity of data on its participation in vascular remodelling associated events. In the present study, we investigated the effects of alamandine on ascending aorta remodelling after transverse aortic constriction (TAC) in mice. Methods and results: C57BL/6J male mice were divided into the following groups: Sham (sham-operated), TAC (operated) and TAC+ALA (operated and treated with alamandine-HPβCD (2-Hydroxypropyl-β-cyclodextrin), 30 μg/kg/day, by gavage). Oral administration of alamandine for 14 days attenuated arterial remodelling by decreasing ascending aorta media layer thickness and the cells density in the adventitia induced by TAC. Alamandine administration attenuated ascending aorta fibrosis induced by TAC, through a reduction in the following parameters; total collagen deposition, expression collagen III and transforming growth factor-β (TGF-β) transcripts, matrix metalloproteinases (MMPs) activity and vascular expression of MMP-2. Importantly, alamandine decreased vascular expression of proinflammatory genes as CCL2, tumour necrosis factor α (TNF-α) and interleukin-1β (IL-1β), and was able to increase expression of MRC1 and FIZZ1, pro-resolution markers, after TAC surgery. Conclusion: Alamandine treatment attenuates vascular remodelling after TAC, at least in part, through anti-fibrotic and anti-inflammatory effects. Hence, this work opens new avenues for the use of this heptapeptide also as a therapeutic target for vascular disease.

Compromised mechanical homeostasis in arterial aging and associated cardiovascular consequences

Aging leads to central artery stiffening and associated hemodynamic sequelae. Because healthy arteries exhibit differential geometry, composition, and mechanical behaviors along the central vasculature, we sought to determine whether wall structure and mechanical function differ across five vascular regions-the ascending and descending thoracic aorta, suprarenal and infrarenal abdominal aorta, and common carotid artery-in 20 versus 100-week-old male wild-type mice. Notwithstanding generally consistent changes across these regions, including a marked thickening of the arterial wall, diminished in vivo axial stretch, and loss of elastic energy storage capacity, the degree of changes tended to be slightly greater in abdominal than in thoracic or carotid vessels. Likely due to the long half-life of vascular elastin, most mechanical changes in the arterial wall resulted largely from a distributed increase in collagen, including thicker fibers in the media, and localized increases in glycosaminoglycans. Changes within the central arteries associated with significant increases in central pulse pressure and adverse changes in the left ventricle, including increased cardiac mass and decreased diastolic function. Given the similar half-life of vascular elastin in mice and humans but very different life-spans, there are important differences in the aging of central vessels across these species. Nevertheless, the common finding of aberrant matrix remodeling contributing to a compromised mechanical homeostasis suggests that studies of central artery aging in the mouse can provide insight into mechanisms and treatment strategies for the many adverse effects of vascular aging in humans.

α-Solanine reverses pulmonary vascular remodeling and vascular angiogenesis in experimental pulmonary artery hypertension

OBJECTIVE

Similar to cancer, pulmonary arterial hypertension (PAH) is characterized by vascular remodeling, which leads to obliteration of the small pulmonary arteriole, with marked proliferation of pulmonary artery smooth muscle cells (PASMC) and/or endothelial cells dysfunction. Aberrant expression of tumor suppressor genes is closely associated with susceptibility to PAH. We hypothesized that α-solanine, a glycoalkaloid found in members of the nightshade family known to have antitumor activity in different cancers, reverses experimental PAH by activating the tumor suppressor-axis inhibition protein 2 (AXIN2).

METHODS AND RESULTS

We investigated the effects of α-solanine on PASMC proliferation and apoptosis by using 5-ethynyl-2'-deoxyuridine proliferation assay, proliferating cell nuclear antigen and Ki67 staining, TUNEL and Anexine V assays. Scratch wound healing and tube formation assays were also used to study migration of endothelial cells. In vitro, we demonstrated, using cultured human PASMC from PAH patients, that α-solanine reversed dysfunctional AXIN2, β-catenin and bone morphogenetic protein receptor type-2 signaling, whereas restored [Ca]i, IL-6 and IL-8, contributing to the decrease of PAH-PASMC proliferation and resistance to apoptosis. Meanwhile, α-solanine inhibits proliferation, migration and tube formation of PAH-pulmonary artery endothelial cells by inhibiting Akt/GSK-3α activation. In vivo, α-solanine administration decreases distal pulmonary arteries remodeling, mean pulmonary arteries pressure and right ventricular hypertrophy in both monocrotaline-induced and Sugen/hypoxia-induced PAH in mice.

CONCLUSION

This study demonstrates that AXIN2/β-catenin axis and Akt pathway can be therapeutically targeted by α-solanine in PAH. α-Solanine could be used as a new therapeutic strategy for the treatment of PAH.

Consideration of Sex Differences in Design and Reporting of Experimental Arterial Pathology Studies-Statement From ATVB Council

There are many differences in arterial diseases between men and women, including prevalence, clinical manifestations, treatments, and prognosis. The new policy of the National Institutes of Health, which requires the inclusion of sex as a biological variable for preclinical studies, aims to foster new mechanistic insights and to enhance our understanding of sex differences in human diseases. The purpose of this statement is to suggest guidelines for designing and reporting sex as a biological variable in animal models of atherosclerosis, thoracic and abdominal aortic aneurysms, and peripheral arterial disease. We briefly review sex differences of these human diseases and their animal models, followed by suggestions on experimental design and reporting of animal studies for these vascular pathologies.

Beneficial Effects of Galectin-3 Blockade in Vascular and Aortic Valve Alterations in an Experimental Pressure Overload Model

Galectin-3 (Gal-3) is involved in cardiovascular fibrosis and aortic valve (AV) calcification. We hypothesized that Gal-3 pharmacological inhibition with modified citrus pectin (MCP) could reduce aortic and AV remodeling in normotensive rats with pressure overload (PO). Six weeks after aortic constriction, vascular Gal-3 expression was up-regulated in male Wistar rats. Gal-3 overexpression was accompanied by an increase in the aortic media layer thickness, enhanced total collagen, and augmented expression of fibrotic mediators. Further, vascular inflammatory markers as well as inflammatory cells content were greater in aorta from PO rats. MCP treatment (100 mg/kg/day) prevented the increase in Gal-3, media thickness, fibrosis, and inflammation in the aorta of PO rats. Gal-3 levels were higher in AVs from PO rats. This paralleled enhanced AV fibrosis, inflammation, as well as greater expression of calcification markers. MCP treatment prevented the increase in Gal-3 as well as fibrosis, inflammation, and calcification in AVs. Overall, Gal-3 is overexpressed in aorta and AVs from PO rats. Gal-3 pharmacological inhibition blocks aortic and AV remodeling in experimental PO. Gal-3 could be a new therapeutic approach to delay the progression and the development of aortic remodeling and AV calcification in PO.

mTOR (Mechanistic Target of Rapamycin) Inhibition Decreases Mechanosignaling, Collagen Accumulation, and Stiffening of the Thoracic Aorta in Elastin-Deficient Mice

OBJECTIVE

Elastin deficiency because of heterozygous loss of an ELN allele in Williams syndrome causes obstructive aortopathy characterized by medial thickening and fibrosis and consequent aortic stiffening. Previous work in Eln-null mice with a severe arterial phenotype showed that inhibition of mTOR (mechanistic target of rapamycin), a key regulator of cell growth, lessened the aortic obstruction but did not prevent early postnatal death. We investigated the effects of mTOR inhibition in Eln-null mice partially rescued by human ELN that manifest a less severe arterial phenotype and survive long term.

APPROACH AND RESULTS

Thoracic aortas of neonatal and juvenile mice with graded elastin deficiency exhibited increased signaling through both mTOR complex 1 and 2. Despite lower predicted wall stress, there was increased phosphorylation of focal adhesion kinase, suggestive of greater integrin activation, and increased transforming growth factor-β-signaling mediators, associated with increased collagen expression. Pharmacological blockade of mTOR by rapalogs did not improve luminal stenosis but reduced mechanosignaling (in delayed fashion after mTOR complex 1 inhibition), medial collagen accumulation, and stiffening of the aorta. Rapalog administration also retarded somatic growth, however, and precipitated neonatal deaths. Complementary, less-toxic strategies to inhibit mTOR via altered growth factor and nutrient responses were not effective.

CONCLUSIONS

In addition to previously demonstrated therapeutic benefits of rapalogs decreasing smooth muscle cell proliferation in the absence of elastin, we find that rapalogs also prevent aortic fibrosis and stiffening attributable to partial elastin deficiency. Our findings suggest that mTOR-sensitive perturbation of smooth muscle cell mechanosensing contributes to elastin aortopathy.

T cell costimulation blockade blunts pressure overload-induced heart failure

Heart failure (HF) is a leading cause of mortality. Inflammation is implicated in HF, yet clinical trials targeting pro-inflammatory cytokines in HF were unsuccessful, possibly due to redundant functions of individual cytokines. Searching for better cardiac inflammation targets, here we link T cells with HF development in a mouse model of pathological cardiac hypertrophy and in human HF patients. T cell costimulation blockade, through FDA-approved rheumatoid arthritis drug abatacept, leads to highly significant delay in progression and decreased severity of cardiac dysfunction in the mouse HF model. The therapeutic effect occurs via inhibition of activation and cardiac infiltration of T cells and macrophages, leading to reduced cardiomyocyte death. Abatacept treatment also induces production of anti-inflammatory cytokine interleukin-10 (IL-10). IL-10-deficient mice are refractive to treatment, while protection could be rescued by transfer of IL-10-sufficient B cells. These results suggest that T cell costimulation blockade might be therapeutically exploited to treat HF.

Abatacept is an FDA-approved drug used for treatment of rheumatoid arthritis. Here the authors show that abatacept reduces cardiomyocyte death in a mouse model of heart failure by inhibiting activation and heart infiltration of T cells and macrophages, an effect mediated by IL-10, suggesting a potential therapy for heart failure.

Ascending aortic adventitial remodeling and fibrosis are ameliorated with Apelin-13 in rats after TAC via suppression of the miRNA-122 and LGR4-β-catenin signaling

Apelin has been proved to be a critical mediator of vascular function and homeostasis. Here, we investigated roles of Apelin in aortic remodeling and fibrosis in rats with transverse aortic constriction (TAC). Male Sprague-Dawley rats were subjected to TAC and then randomized to daily deliver Apelin-13 (50μg/kg) or angiotensin type 1 receptor (AT1) blocker Irbesartan (50mg/kg) for 4 weeks. Pressure overload resulted in myocardial hypertrophy, systolic dysfunction, aortic remodeling and adventitial fibrosis with reduced levels of Apelin in ascending aortas of rat after TAC compared with sham-operated group. These changes were associated with marked increases in levels of miRNA-122, TGFβ1, CTGF, NFAT5, LGR4, and β-catenin. More importantly, Apelin and Irbesartan treatment strikingly prevented TAC-mediated aortic remodeling and adventitial fibrosis in pressure overloaded rats by blocking AT1 receptor and miRNA-122 levels and repressing activation of the CTGF-NFAT5 and LGR4-β-catenin signaling. In cultured primary rat adventitial fibroblasts, exposure to angiotensin II (100nmolL^-1) led to significant increases in cellular migration and levels of TGFβ1, CTGF, NFAT5, LGR4 and β-catenin, which were effectively reversed by pre-treatment with Apelin (100nmolL^-1) and miRNA-122 inhibitor (50nmolL^-1). In conclusion, Apelin counterregulated against TAC-mediated ascending aortic remodeling and angiotensin II-induced promotion of cellular migration by blocking AT1 receptor and miRNA-122 levels and preventing activation of the TGFβ1-CTGF-NFAT5 and LGR4-β-catenin signaling, ultimately contributing to attenuation of aortic adventitial fibrosis. Our data point to Apelin as an important regulator of aortic remodeling and adventitial fibrosis and a promising target for vasoprotective therapies.