Inflammatory and immune responses in the arterial media

Potential protective role of let-7d-5p in atherosclerosis progression reducing the inflammatory pathway regulated by NF-κB and vascular smooth muscle cells proliferation

The prevalence of cardiovascular diseases (CVDs) is increasing in the last decades, even is the main cause of death in first world countries being atherosclerosis one of the principal triggers. Therefore, there is an urgent need to decipher the underlying mechanisms involved in atherosclerosis progression. In this respect, microRNAs dysregulation is frequently involved in the progression of multiple diseases including CVDs. Our aim was to demonstrate that let-7d-5p unbalance could contribute to the pathophysiology of atherosclerosis and serve as a potential diagnostic biomarker. We evaluated let-7d-5p levels in vascular biopsies and exosome-enriched extracellular vesicles (EVs) from patients with carotid atherosclerosis and healthy donors. Moreover, we overexpressed let-7d-5p in vitro in vascular smooth muscle cells (VSMCs) to decipher the targets and the underlying mechanisms regulated by let-7d-5p in atherosclerosis. Our results demonstrate that let-7d-5p was significantly upregulated in carotid plaques from overweight patients with carotid atherosclerosis. Moreover, in EVs isolated from plasma, we found that let-7d-5p levels were increased in carotid atherosclerosis patients compared to control subjects specially in overweight patients. Receiver Operating Characteristic (ROC) analyses confirmed its utility as a diagnostic biomarker for atherosclerosis. In VSMCs, we demonstrated that increased let-7d-5p levels impairs cell proliferation and could serve as a protective mechanism against inflammation by impairing NF-κB pathway without affecting insulin resistance. In summary, our results highlight the role of let-7d-5p as a potential therapeutic target for atherosclerosis since its overexpression induce a decrease in inflammation and VSMCs proliferation, and also, as a novel non-invasive diagnostic biomarker for atherosclerosis in overweight patients.

Role of macrophages in aortic dissection pathogenesis: insights from preclinical studies to translational prospective

Aortic dissection is a critical vascular disease that is characterized by a high mortality rate and inflammation significantly influences its onset and progression. Recent studies highlight the integral role of macrophages, key players in the immune system, in the pathological landscape of aortic dissection. These cells are involved in crucial processes, such as the remodeling of the extracellular matrix, immunocyte infiltration, and phenotypic switching of smooth muscle cells, which are essential for the structural integrity and functional dynamics of the aortic wall. Despite these insights, the specific contributions of macrophages to the development and progression of aortic dissection remains unclear. This review explores the pathogenesis of aortic dissection with a focus on macrophages and describes their origins, phenotypic variations, and potential roles based on the most recent research findings. Furthermore, we discuss key molecules related to macrophages during aortic dissection, their interactions with other cellular components within the aorta, and the implications of these interactions for future therapeutic strategies. This comprehensive analysis aimed to improve our understanding of macrophages in aortic dissection and promote the development of targeted interventions.

Mapping the unicellular transcriptome of the ascending thoracic aorta to changes in mechanosensing and mechanoadaptation during aging

Aortic stiffening is an inevitable manifestation of chronological aging, yet the mechano-molecular programs that orchestrate region- and layer-specific adaptations along the length and through the wall of the aorta are incompletely defined. Here, we show that the decline in passive cyclic distensibility is more pronounced in the ascending thoracic aorta (ATA) compared to distal segments of the aorta and that collagen content increases in both the medial and adventitial compartments of the ATA during aging. The single-cell RNA sequencing of aged ATA tissues reveals altered cellular senescence, remodeling, and inflammatory responses accompanied by enrichment of T-lymphocytes and rarefaction of vascular smooth muscle cells, compared to young samples. T lymphocyte clusters accumulate in the adventitia, while the activation of mechanosensitive Piezo-1 enhances vasoconstriction and contributes to the overall functional decline of ATA tissues. These results portray the immuno-mechanical aging of the ATA as a process that culminates in a stiffer conduit permissive to the accrual of multi-gerogenic signals priming to disease development.

Regulation of vascular remodeling by immune microenvironment after the establishment of autologous arteriovenous fistula in ESRD patients

Autogenous arteriovenous fistula (AVF) is the preferred dialysis access for receiving hemodialysis treatment in end-stage renal disease patients. After AVF is established, vascular remodeling occurs in order to adapt to hemodynamic changes. Uremia toxins, surgical injury, blood flow changes and other factors can induce inflammatory response, immune microenvironment changes, and play an important role in the maintenance of AVF vascular remodeling. This process involves the infiltration of pro-inflammatory and anti-inflammatory immune cells and the secretion of cytokines. Pro-inflammatory and anti-inflammatory immune cells include neutrophil (NEUT), dendritic cell (DC), T lymphocyte, macrophage (Mφ), etc. This article reviews the latest research progress and focuses on the role of immune microenvironment changes in vascular remodeling of AVF, in order to provide a new theoretical basis for the prevention and treatment of AVF failure.

Extracellular Matrix Remodeling in Vascular Disease: Defining Its Regulators and Pathological Influence

Because of structural and cellular differences (ie, degrees of matrix abundance and cross-linking, mural cell density, and adventitia), large and medium-sized vessels, in comparison to capillaries, react in a unique manner to stimuli that induce vascular disease. A stereotypical vascular injury response is ECM (extracellular matrix) remodeling that occurs particularly in larger vessels in response to injurious stimuli, such as elevated angiotensin II, hyperlipidemia, hyperglycemia, genetic deficiencies, inflammatory cell infiltration, or exposure to proinflammatory mediators. Even with substantial and prolonged vascular damage, large- and medium-sized arteries, persist, but become modified by (1) changes in vascular wall cellularity; (2) modifications in the differentiation status of endothelial cells, vascular smooth muscle cells, or adventitial stem cells (each can become activated); (3) infiltration of the vascular wall by various leukocyte types; (4) increased exposure to critical growth factors and proinflammatory mediators; and (5) marked changes in the vascular ECM, that remodels from a homeostatic, prodifferentiation ECM environment to matrices that instead promote tissue reparative responses. This latter ECM presents previously hidden matricryptic sites that bind integrins to signal vascular cells and infiltrating leukocytes (in coordination with other mediators) to proliferate, invade, secrete ECM-degrading proteinases, and deposit injury-induced matrices (predisposing to vessel wall fibrosis). In contrast, in response to similar stimuli, capillaries can undergo regression responses (rarefaction). In summary, we have described the molecular events controlling ECM remodeling in major vascular diseases as well as the differential responses of arteries versus capillaries to key mediators inducing vascular injury.

The innate immune sensor STING accelerates neointima formation via NF-κB signaling pathway

Vascular smooth muscle cells (VSMCs) proliferation, migration, and phenotypic switching are considered crucial events in the progression of neointima formation. Stimulator of interferon genes (STING), an innate immune sensor of cyclic dinucleotides against pathogens, in neointima formation remains obscure. Here, we observed a significant increase in STING expression on the neointima of injured vessels and mouse aortic VSMCs induced by PDGF-BB. In vivo, global knockout of STING (Sting-/-) attenuated neointima formation after vascular injury. In vitro data showed that STING deficiency significantly alleviated PDGF-BB-induced proliferation and migration in VSMCs. Furthermore, these contractile marker genes were upregulated in Sting-/- VSMCs. Overexpression of STING promoted proliferation, migration, and phenotypic switching in VSMCs. Mechanistically, STING-NF-κB signaling was involved in this process. The pharmacological inhibition of STING induced by C-176 partially prevented neointima formation due to suppression of VSMCs proliferation. Taken together, STING-NF-κB axis significantly promoted proliferation, migration, and phenotypic switching of VSMCs, which may be a novel therapeutic approach to combat vascular proliferative diseases.

Signaling pathways in vascular function and hypertension: molecular mechanisms and therapeutic interventions

Hypertension is a global public health issue and the leading cause of premature death in humans. Despite more than a century of research, hypertension remains difficult to cure due to its complex mechanisms involving multiple interactive factors and our limited understanding of it. Hypertension is a condition that is named after its clinical features. Vascular function is a factor that affects blood pressure directly, and it is a main strategy for clinically controlling BP to regulate constriction/relaxation function of blood vessels. Vascular elasticity, caliber, and reactivity are all characteristic indicators reflecting vascular function. Blood vessels are composed of three distinct layers, out of which the endothelial cells in intima and the smooth muscle cells in media are the main performers of vascular function. The alterations in signaling pathways in these cells are the key molecular mechanisms underlying vascular dysfunction and hypertension development. In this manuscript, we will comprehensively review the signaling pathways involved in vascular function regulation and hypertension progression, including calcium pathway, NO-NOsGC-cGMP pathway, various vascular remodeling pathways and some important upstream pathways such as renin-angiotensin-aldosterone system, oxidative stress-related signaling pathway, immunity/inflammation pathway, etc. Meanwhile, we will also summarize the treatment methods of hypertension that targets vascular function regulation and discuss the possibility of these signaling pathways being applied to clinical work.

Single-Cell RNA-Seq Analysis Reveals Macrophages Are Involved in the Pathogenesis of Human Sporadic Acute Type A Aortic Dissection

Macrophages play an important role in the progression of sporadic acute type A aortic dissection (ATAAD). The aim of this study was to characterize the cellular heterogeneity of macrophages in ATAAD tissues by scRNA-seq. Ascending aortic wall tissue from six ATAAD patients and three heart transplant donors was assessed by scRNA-seq and then analyzed and validated by various bioinformatic algorithms and histopathology experiments. The results revealed that the proportion of macrophages in ATAAD tissues (24.51%) was significantly higher than that in normal tissues (13.69%). Among the six macrophage subclusters, pro-inflammatory macrophages accounted for 14.96% of macrophages in the AD group and 0.18% in the normal group. Chemokine- and inflammation-related genes (CCL2, CCL20, S100A8, and S100A9) were expressed more intensively in macrophages in ATAAD tissue than in those in normal tissue. Additionally, intercellular communication analysis and transcription factor analysis indicated the activation of inflammation and degradation of the extracellular matrix in ATAAD tissue. Finally, immunohistochemistry, immunofluorescence, and Western blot experiments confirmed the overexpression of macrophage marker genes (CD68 and CD163) and matrix metalloproteinases (MMP9 and MMP2) in ATAAD tissue. Collectively, our study provides a preliminary evaluation of the role of macrophages in ATAAD, and the results could aid in the development of therapeutic options in the future.

Melatonin and Aging

The health problems associated with the aging process are becoming increasingly widespread due to the increase in mean life expectancy taking place globally. While decline of many organ functions is an unavoidable concomitant of senescence, these can be delayed or moderated by a range of factors. Among these are dietary changes and weight control, taking sufficient exercise, and the utilization of various micronutrients. The utility of incurring appropriate changes in lifestyle is generally not confined to a single organ system but has a broadly positive systemic effect.Among one of the most potent means of slowing down age-related changes is the use of melatonin, a widely distributed biological indole. While melatonin is well known as a treatment for insomnia, it has a wide range of beneficial qualities many of which are relevant. This overview describes how several of the properties of melatonin are especially relevant to many of the changes associated with senescence. Changes in functioning of the immune system are particularly marked in the aged, combining diminishing effectiveness with increasing ineffective and harmful activity. Melatonin treatment appears able to moderate and partially reverse this detrimental drift toward immune incompetence.

Visfatin is a multifaceted molecule that exerts regulation effects on inflammation and apoptosis in RAW264.7 cells and mice immune organs

Visfatin, a multifunctional adipocytokine, is particularly important in the regulation of apoptosis and inflammation through an unidentified mechanism. Clarifying the control mechanisms of visfatin on inflammation and apoptosis in RAW264.7 cells and mice immunological organs was the goal of the current investigation. In order to create a pathophysiological model, the RAW264.7 cells were stimulated with 200 ng/mL visfatin and 20 μg/mL lipopolysaccharide (LPS), either separately or combined. The effects of exogenous visfatin on inflammation and apoptosis in RAW264.7 cells were investigated by flow cytometry assay, RNA-seq analysis and fluorescence quantitative PCR. According to the findings, exogenous visfatin exhibits dual effects on inflammation by modulating the expression of IL-1α, TNFRSF1B, and LIF as well as taking part in various signaling pathways, including the MAPK and Rap1 signaling pathways. By controlling the expression levels of Bcl2l1, Bcl2a1a, and Fas and primarily participating in the PI3K/AKT signaling pathway and Hippo signaling pathway, exogenous visfatin can inhibit apoptosis in RAW264.7 cells. The visfatin inhibitor FK866 was used to further confirm the effects of visfatin on inflammation and apoptosis in mice immune organs. Subsequently, mice spleen and thymus were collected. It is interesting to note that in LPS-treated mice, suppression of endogenous visfatin might worsen the immune system's inflammatory response and even result in rapid mortality. Additionally, endogenous visfatin promotes the apoptosis in mice immune organs by regulating the expression levels of Bcl2l1, Fas, Caspase 3, Bcl2a1a, and Bax. Together, these results imply that visfatin is a multifaceted molecule that regulates inflammation and apoptosis in RAW264.7 cells and mice immunological organs by taking part in a variety of biological processes and regulating the amounts of associated cytokines expression. Our findings offer additional understandings of how visfatin affects apoptosis and inflammation.

Macrophages regulate vascular smooth muscle cell function during atherosclerosis progression through IL-1β/STAT3 signaling

Vascular smooth muscle cells (VSMCs) play a central role in atherosclerosis progression, but the functional changes in VSMCs and the associated cellular crosstalk during atherosclerosis progression remain unknown. Here we show that scRNA-seq analysis of proximal adjacent (PA) and atherosclerotic core (AC) regions of human carotid artery plaques identifies functional alterations in macrophage-like VSMCs, elucidating the main state differences between PA and AC VSMCs. And, IL-1β mediates macrophage-macrophage-like VSMC crosstalk through regulating key transcription factors involved in macrophage-like VSMCs functional alterations during atherosclerosis progression. In vitro assays reveal VSMCs trans-differentiated into a macrophage-like phenotype and then functional alterations in response to macrophage-derived stimuli. IL-1β promots the adhesion, inflammation, and apoptosis of macrophage-like VSMCs in a STAT3 dependent manner. The current findings provide interesting insight into the macrophages-macrophage-like VSMC crosstalk, which would drive functional alterations in the latter cell type through IL-1β/STAT3 axis during atherosclerosis progression.

Shear stress and intravascular pressure effects on vascular dynamics: two-phase blood flow in elastic microvessels accounting for the passive stresses

We study the steady hemodynamics in physiological elastic microvessels proposing an advanced fluid-structure interaction model. The arteriolar tissue is modeled as a two-layer fiber-reinforced hyperelastic material representing its Media and Adventitia layers. The constitutive model employed (Holzapfel et al. in J Elast 61:1-48, 2000) is parametrized via available data on stress-strain experiments for arterioles. The model is completed by simulating the blood/plasma flow in the lumen, using the thixotropic elasto-viscoplastic model in its core, and the linear Phan-Thien and Tanner viscoelastic model in its annular part. The Cell-Free Layer (CFL) and the Fåhraeus and Fåhraeus-Lindqvist effects are considered via analytical expressions based on experimental data (Giannokostas et al. in Materials (Basel) 14:367, 2021b). The coupling between tissue deformation and blood flow is achieved through the experimentally verified pressure-shear hypothesis (Pries et al. Circ Res 77:1017-1023, 1995). Our calculations confirm that the increase in the reference inner radius produces larger expansion. Also, by increasing the intraluminal pressure, the thinning of the walls is more pronounced and it may reach 40% of the initial thickness. Comparing our predictions with those in rigid-wall microtubes, we conclude that apart from the vital importance of vasodilation, there is an up to 25% reduction in wall shear stress. The passive vasodilation contributes to the decrease in the tissue stress fields and affects the hemodynamic features such as the CFL thickness, reducing the plasma layer when blood flows in vessels with elastic walls, in quantitative agreement with previous experiments. Our calculations verify the correctness of the pressure-shear hypothesis but not that of the Laplace law.

Molecular Signature of Antibody-Mediated Chronic Vasculopathy in Heart Allografts in a Novel Mouse Model

Cardiac allograft vasculopathy (CAV) limits the long-term success of heart transplants. Generation of donor-specific antibodies (DSAs) is associated with increased incidence of CAV clinically, but mechanisms underlying development of this pathology remain poorly understood. Major histocompatibility complex-mismatched A/J cardiac allografts in B6.CCR5-/- recipients have been reported to undergo acute rejection with little T-cell infiltration, but intense deposition of C4d in large vessels and capillaries of the graft accompanied by high titers of DSA. This model was modified to investigate mechanisms of antibody-mediated CAV by transplanting A/J hearts to B6.CCR5-/- CD8-/- mice that were treated with low doses of anti-CD4 monoclonal antibody to decrease T-cell-mediated graft injury and promote antibody-mediated injury. Although the mild inhibition of CD4 T cells extended allograft survival, the grafts developed CAV with intense C4d deposition and macrophage infiltration by 14 days after transplantation. Development of CAV correlated with recipient DSA titers. Transcriptomic analysis of microdissected allograft arteries identified the Notch ligand Dll4 as the most elevated transcript in CAV, associated with high versus low titers of DSA. More importantly, these analyses revealed a differential expression of transcripts in the CAV lesions compared with the matched apical tissue that lacks large arteries. In conclusion, these findings report a novel model of antibody-mediated CAV with the potential to facilitate further understanding of the molecular mechanisms promoting development of CAV.

Innate and Adaptive Immune Cells Associates with Arteriovenous Fistula Maturation and Failure

Creation of arteriovenous fistula (AVF) causes local injury resulting in immune response of the body and infiltration of immune cells. Acute inflammation is favorable to control inflammation and proceed AVF towards maturation while chronic inflammation in AVF lead to AVF maturation failure. Chronic inflammation in AVF is due to chronic infiltration of immune cells and secretion of inflammatory cytokines. A balance between pro-inflammatory and anti-inflammatory response is must for AVF maturation and an overwhelmed proinflammatory infiltrate endue chronic inflammation and AVF failure. Since immune cell infiltration plays a critical role in maturation and failure of AVF, it is important to investigate the role of immune cells as well as their density in early and late phase of AVF maturation. The role of inflammation has been discussed in the literature and this review article focuses on the role of pro- and anti-inflammatory immune cells including macrophages, dendritic cells, T-cells, and T-regulatory cells in AVF maturation and maturation failure.

The why and how of adaptive immune responses in ischemic cardiovascular disease

Atherosclerotic cardiovascular disease is a major cause of disability and death worldwide. Most therapeutic approaches target traditional risk factors but ignore the fundamental role of the immune system. This is a huge unmet need. Recent evidence indicates that reducing inflammation may limit cardiovascular events. However, the concomitant increase in the risk of lifethreatening infections is a major drawback. In this context, targeting adaptive immunity could constitute a highly effective and safer approach. In this Review, we address the why and how of the immuno-cardiovascular unit, in health and in atherosclerotic disease. We review and discuss fundamental mechanisms that ensure immune tolerance to cardiovascular tissue, and examine how their disruption promotes disease progression. We identify promising strategies to manipulate the adaptive immune system for patient benefit, including novel biologics and RNA-based vaccination strategies. Finally, we advocate for establishing a molecular classification of atherosclerosis as an important milestone in our quest to radically change the understanding and treatment of atherosclerotic disease.

Atherogenesis, Transcytosis, and the Transmural Cholesterol Flux: A Critical Review

The recently described phenomenon of cholesterol-loaded low-density lipoproteins (LDL) entering the arterial wall from the lumen by transcytosis has been accepted as an alternative for the long-held concept that atherogenesis involves only passive LDL movement across an injured or dysfunctional endothelial barrier. This active transport of LDL can now adequately explain why plaques (atheromas) appear under an intact, uninjured endothelium. However, the LDL transcytosis hypothesis is still questionable, mainly because the process serves no clear physiological purpose. Moreover, central components of the putative LDL transcytosis apparatus are shared by the counter process of cholesterol efflux and reverse cholesterol transport (RCT) and therefore can essentially create an energy-wasting futile cycle and paradoxically be pro- and antiatherogenic simultaneously. Hence, by critically reviewing the literature, we wish to put forward an alternative interpretation that, in our opinion, better fits the experimental evidence. We assert that most of the accumulating cholesterol (mainly as LDL) reaches the intima not from the lumen by transcytosis, but from the artery's inner layers: the adventitia and media. We have named this directional cholesterol transport transmural cholesterol flux (TCF). We suggest that excess cholesterol, diffusing from the avascular (i.e., devoid of blood and lymph vessels) media's smooth muscle cells, is cleared by the endothelium through its apical membrane. A plaque is formed when this cholesterol clearance rate lags behind its rate of arrival by TCF.

Neuropilin-1 deficiency in vascular smooth muscle cells is associated with hereditary hemorrhagic telangiectasia arteriovenous malformations

Patients with hereditary hemorrhagic telangiectasia (HHT) have arteriovenous malformations (AVMs) with genetic mutations involving the activin-A receptor like type 1 (ACVRL1 or ALK1) and endoglin (ENG). Recent studies have shown that Neuropilin-1 (NRP-1) inhibits ALK1. We investigated the expression of NRP-1 in livers of patients with HHT and found that there was a significant reduction in NRP-1 in perivascular smooth muscle cells (SMCs). We used Nrp1^SM22KO mice (Nrp1 was ablated in SMCs) and found hemorrhage, increased immune cell infiltration with a decrease in SMCs, and pericyte lining in lungs and liver in adult mice. Histologic examination revealed lung arteriovenous fistulas (AVFs) with enlarged liver vessels. Evaluation of the retina vessels at P5 from Nrp1^SM22KO mice demonstrated dilated capillaries with a reduction of pericytes. In inflow artery of surgical AVFs from the Nrp1^SM22KO versus WT mice, there was a significant decrease in Tgfb1, Eng, and Alk1 expression and phosphorylated SMAD1/5/8 (pSMAD1/5/8), with an increase in apoptosis. TGF-β1–stimulated aortic SMCs from Nrp1^SM22KO versus WT mice have decreased pSMAD1/5/8 and increased apoptosis. Coimmunoprecipitation experiments revealed that NRP-1 interacts with ALK1 and ENG in SMCs. In summary, NRP-1 deletion in SMCs leads to reduced ALK1, ENG, and pSMAD1/5/8 signaling and reduced cell death associated with AVM formation.

Two-stage degradation and novel functional endothelium characteristics of a 3-D printed bioresorbable scaffold

Bioresorbable scaffolds have emerged as a new generation of vascular implants for the treatment of atherosclerosis, and designed to provide a temporary scaffold that is subsequently absorbed by blood vessels over time. Presently, there is insufficient data on the biological and mechanical responses of blood vessels accompanied by bioresorbable scaffolds (BRS) degradation. Therefore, it is necessary to investigate the inflexion point of degradation, the response of blood vessels, and the pathophysiological process of vascular, as results of such studies will be of great value for the design of next generation of BRS. In this study, abdominal aortas of SD rats were received 3-D printed poly-l-actide vascular scaffolds (PLS) for various durations up to 12 months. The response of PLS implanted aorta went through two distinct processes: (1) the neointima with desirable barrier function was obtained in 1 month, accompanied with slow degradation, inflammation, and intimal hyperplasia; (2) significant degradation occurred from 6 months, accompanied with decreasing inflammation and intimal hyperplasia, while the extracellular matrix recovered to normal vessels which indicate the positive remodeling. These in vivo results indicate that 6 months is a key turning point. This “two-stage degradation and vascular characteristics” is proposed to elucidate the long-term effects of PLS on vascular repair and demonstrated the potential of PLS in promoting endothelium function and positive remodeling, which highlights the benefits of PLS and shed some light in the future researches, such as drug combination coatings design.

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Proposed two-stage degradation of a PLLA BRS to reveal distinct neointimal recovery and vascular responsive processes.

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Revealed novel benefits of BRS, including fine endothelium function, anti-thrombosis, and anti-inflammatory.

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Drug combination coatings should be designed concerning special degradation of BRS and the key turning point, 6 months.

New insights into the pathogenesis of giant cell arteritis: are they relevant for precision medicine?

Giant cell arteritis is a primary granulomatous vasculitis characterised by a strict tissue tropism for large and medium-size vessels, occurring in people older than 50 years. Although considerable progress in understanding some of the pathophysiological mechanisms involved in the pathogenesis of giant cell arteritis has been made in the past 10 years, specific triggers of disease and mechanisms of chronic damage have not yet been identified. The definition of a specific pro-inflammatory hierarchy between the multiple cell types and the different cytokines or chemokines involved in the inflammatory process are still unexplored areas of study. The overall goal of precision medicine is to identify the best possible therapeutic approach for an individual or group of individuals with a given disease. The fundamental prerequisite of this approach is the identification, at baseline, of clinical and imaging findings and of molecular biomarkers that allow a precise stratification of patients and an adequate prediction of the therapeutic response. In this regard, the possibility of obtaining temporal artery biopsies for diagnostic purposes offers incredible exploratory possibilities to define different disease pathotypes potentially susceptible to different therapeutic interventions. In this Series paper, we will describe the most recent evidence relating to the pathogenesis of giant cell arteritis, trying to define, if possible, a new pathogenetic-centred approach to patients with giant cell arteritis.

The Impact of Inflammation on the Immune Responses to Transplantation: Tolerance or Rejection?

Transplantation (Tx) remains the optimal therapy for end-stage disease (ESD) of various solid organs. Although alloimmune events remain the leading cause of long-term allograft loss, many patients develop innate and adaptive immune responses leading to graft tolerance. The focus of this review is to provide an overview of selected aspects of the effects of inflammation on this delicate balance following solid organ transplantation. Initially, we discuss the inflammatory mediators detectable in an ESD patient. Then, the specific inflammatory mediators found post-Tx are elucidated. We examine the reciprocal relationship between donor-derived passenger leukocytes (PLs) and those of the recipient, with additional emphasis on extracellular vesicles, specifically exosomes, and we examine their role in determining the balance between tolerance and rejection. The concept of recipient antigen-presenting cell "cross-dressing" by donor exosomes is detailed. Immunological consequences of the changes undergone by cell surface antigens, including HLA molecules in donor and host immune cells activated by proinflammatory cytokines, are examined. Inflammation-mediated donor endothelial cell (EC) activation is discussed along with the effect of donor-recipient EC chimerism. Finally, as an example of a specific inflammatory mediator, a detailed analysis is provided on the dynamic role of Interleukin-6 (IL-6) and its receptor post-Tx, especially given the potential for therapeutic interdiction of this axis with monoclonal antibodies. We aim to provide a holistic as well as a reductionist perspective of the inflammation-impacted immune events that precede and follow Tx. The objective is to differentiate tolerogenic inflammation from that enhancing rejection, for potential therapeutic modifications. (Words 247).

Vascular Mechanobiology: Homeostasis, Adaptation, and Disease

Cells of the vascular wall are exquisitely sensitive to changes in their mechanical environment. In healthy vessels, mechanical forces regulate signaling and gene expression to direct the remodeling needed for the vessel wall to maintain optimal function. Major diseases of arteries involve maladaptive remodeling with compromised or lost homeostatic mechanisms. Whereas homeostasis invokes negative feedback loops at multiple scales to mediate mechanobiological stability, disease progression often occurs via positive feedback that generates mechanobiological instabilities. In this review, we focus on the cell biology, wall mechanics, and regulatory pathways associated with arterial health and how changes in these processes lead to disease. We discuss how positive feedback loops arise via biomechanical and biochemical means. We conclude that inflammation plays a central role in overriding homeostatic pathways and suggest future directions for addressing therapeutic needs.

Macrophage ontogeny and functional diversity in cardiometabolic diseases

Macrophages are the dominant immune cell types in the adipose tissue, the liver or the aortic wall and they were originally believed to mainly derived from monocytes to fuel tissue inflammation in cardiometabolic diseases. However, over the last decade the identification of tissue resident macrophages (trMacs) from embryonic origin in these metabolic tissues has provided a breakthrough in the field forcing to better comprehend macrophage diversity during pathological states. Infiltrated monocyte-derived macrophages (moMacs), similar to trMacs, adapt to the local metabolic environment that eventually shapes their functions. In this review, we will summarize the emerging versatility of macrophages in cardiometabolic diseases with a focus in the control of adipose tissue, liver and large vessels homeostasis.

Heterogeneous subpopulations of adventitial progenitor cells regulate vascular homeostasis and pathological vascular remodeling

Cardiovascular diseases are characterized by chronic vascular dysfunction and provoke pathological remodeling events such as neointima formation, atherosclerotic lesion development, and adventitial fibrosis. While lineage-tracing studies have shown that phenotypically modulated smooth muscle cells (SMCs) are the major cellular component of neointimal lesions, the cellular origins and microenvironmental signaling mechanisms that underlie remodeling along the adventitial vascular layer are not fully understood. However, a growing body of evidence supports a unique population of adventitial lineage-restricted progenitor cells expressing the stem cell marker, stem cell antigen-1 (Sca1; AdvSca1 cells) as important effectors of adventitial remodeling and suggests that they are at least partially responsible for subsequent pathological changes that occur in the media and intima. AdvSca1 cells are being studied in murine models of atherosclerosis, perivascular fibrosis, and neointima formation in response to acute vascular injury. Depending on the experimental conditions, AdvSca1 cells exhibit the capacity to differentiate into SMCs, endothelial cells, chondrocytes, adipocytes, and pro-remodeling cells such as myofibroblasts and macrophages. These data indicate that AdvSca1 cells may be a targetable cell population to influence the outcomes of pathologic vascular remodeling. Important questions remain regarding the origins of AdvSca1 cells and the essential signaling mechanisms and microenvironmental factors that regulate both maintenance of their stem-like, progenitor phenotype and their differentiation into lineage-specified cell types. Adding complexity to the story, recent data indicate that the collective population of adventitial progenitor cells is likely composed of several smaller, lineage-restricted subpopulations which are not fully defined by their transcriptomic profile and differentiation capabilities. The aim of this review is to outline the heterogeneity of Sca1+ adventitial progenitor cells, summarize their role in vascular homeostasis and remodeling, and comment on their translational relevance in humans.

Complementary roles of mechanotransduction and inflammation in vascular homeostasis

Arteries are exposed to relentless pulsatile haemodynamic loads, but via mechanical homeostasis they tend to maintain near optimal structure, properties and function over long periods in maturity in health. Numerous insults can compromise such homeostatic tendencies, however, resulting in maladaptations or disease. Chronic inflammation can be counted among the detrimental insults experienced by arteries, yet inflammation can also play important homeostatic roles. In this paper, we present a new theoretical model of complementary mechanobiological and immunobiological control of vascular geometry and composition, and thus properties and function. We motivate and illustrate the model using data for aortic remodelling in a common mouse model of induced hypertension. Predictions match the available data well, noting a need for increased data for further parameter refinement. The overall approach and conclusions are general, however, and help to unify two previously disparate literatures, thus leading to deeper insight into the separate and overlapping roles of mechanobiology and immunobiology in vascular health and disease.

Visfatin Exerts Immunotherapeutic Effects in Lipopolysaccharide-Induced Acute Lung Injury in Murine Model

Visfatin acts as a significant regulator of inflammatory cytokines. However, the immunological response and therapeutic effects of visfatin under bacterial stress in murine lung tissue are still not clear. To investigate the role of visfatin on lipopolysaccharide (LPS)-induced acute lung injury (ALI), thirty Kunming mice were divided into Saline, LPS, and LPS + visfatin groups. After routine blood examination, the effects of visfatin on inflammatory cytokines, lung tissue structure, and expression of inflammatory mediators were explored through hematoxylin-eosin (H&E), Masson and immunohistochemical staining, quantitative polymerase chain reaction (Q-PCR), and Western blotting. Compared with the Saline group, neutrophil percentage, peripheral blood neutrophil count, and the ratio of lymphocyte count (NLR) were upregulated in LPS group. Moreover, Masson staining showed alterations in lung tissue structure; the mRNA level of different cytokines (IL-6, IL-1β, TNF-α, IL-10, TLR4, IFN-γ) was upregulated; and the protein expression of interleukin (IL)-6, myeloperoxidase (MPO), and transforming growth factor-β1 (TGF-β) was significantly (p < 0.05) different in LPS group. Compared with LPS group, neutrophil percentage significantly decreased (p < 0.01), the numbers of lymphocytes significantly (p < 0.05) increased, NLR decreased, Masson staining of the lung was extremely different (p < 0.01), the structure of the lung was slightly damaged, and the myeloperoxidase values of lung showed no differences in LPS + visfatin. Hence, visfatin inhibits the lung inflammation induced by ALI. During the ALI, visfatin acts by decreasing NLR, downregulated the expression of MPO, enhanced antioxidant capacity, and regulated the inflammatory factors IL-1β, IL-6, IL-10, and TNF-α to reduce the lung injury.

Proliferative, degradative smooth muscle cells promote aortic disease

Aneurysms are common in the abdominal and thoracic regions of the aorta and can cause death due to dissection or rupture. Traditionally, thoracic aortic aneurysms have been labeled as a degenerative disease, characterized by alterations in extracellular matrix and loss of smooth muscle cells (SMCs) in the medial layer of the aortic wall. In this issue of the JCI, Li and colleagues introduce an unconventional concept by demonstrating that mTOR-dependent proliferative SMCs render the aortic wall vulnerable to dilatation and dissection rather than prevent disease progression. These vascular SMCs, termed degradative SMCs, compromise the medial properties and function of the aortic wall by enhanced proteolytic and phagocytic activity; however, the cells do not transdifferentiate into macrophages. The degradative SMC phenotype also worsens atherosclerotic disease and could thus be considered as a therapeutic target for diverse aortic diseases.

Cellular Signaling Pathways in Medium and Large Vessel Vasculitis

Autoimmune and autoinflammatory diseases of the medium and large arteries, including the aorta, cause life-threatening complications due to vessel wall destruction but also by wall remodeling, such as the formation of wall-penetrating microvessels and lumen-stenosing neointima. The two most frequent large vessel vasculitides, giant cell arteritis (GCA) and Takayasu arteritis (TAK), are HLA-associated diseases, strongly suggestive for a critical role of T cells and antigen recognition in disease pathogenesis. Recent studies have revealed a growing spectrum of effector functions through which T cells participate in the immunopathology of GCA and TAK; causing the disease-specific patterning of pathology and clinical outcome. Core pathogenic features of disease-relevant T cells rely on the interaction with endothelial cells, dendritic cells and macrophages and lead to vessel wall invasion, formation of tissue-damaging granulomatous infiltrates and induction of the name-giving multinucleated giant cells. Besides antigen, pathogenic T cells encounter danger signals in their immediate microenvironment that they translate into disease-relevant effector functions. Decisive signaling pathways, such as the AKT pathway, the NOTCH pathway, and the JAK/STAT pathway modify antigen-induced T cell activation and emerge as promising therapeutic targets to halt disease progression and, eventually, reset the immune system to reestablish the immune privilege of the arterial wall.

Inflammatory cells in perivascular adipose tissue and the integrity of the tunica media in atherosclerotic coronary arteries

Obstructive coronary artery disease (CAD) is characterized by inflammation within the atherosclerotic coronary arteries. Infiltration of inflammatory cells into muscular media can lead to remodeling and weakening of the arterial wall. We examined the relationship between inflammatory infiltration in perivascular adipose tissue (PVAT), state of the external elastic membrane, and the intensity of inflammatory infiltration in the tunica media of coronary arteries obtained by endarterectomy from symptomatic patients with diffuse CAD. We analyzed endarterectomy sequesters from 22 coronary arteries that contained the intima, media, a part of the adventitia, and PVAT in at least one part of the sequester. The coronary arteries were divided into two groups according to the presence or absence of inflammatory infiltration in PVAT. Staining with hematoxylin-eosin and by the Movat's method showed atherosclerotic changes in the intima and media. Immunohistochemistry (anti-leukocyte common antigen [LCA] antibody) was used for the detection of leukocytes. We found a significant positive correlation between inflammatory infiltration in PVAT and preservation of the external elastic membrane of coronary arteries. Furthermore, we found a significant negative correlation between inflammatory infiltration in PVAT and the intensity of inflammatory infiltration in the media. It seems that the integrity of the external elastic membrane and the proinflammatory properties of PVAT restrain inflammatory cells within PVAT. Both effects may prevent the migration of inflammatory cells into the media and delay the development of CAD.

Inflammation, immunity, and vascular remodeling in pulmonary hypertension; Evidence for complement involvement?

Pulmonary (arterial) hypertension (PH/PAH) is a life-threatening cardiopulmonary disorder. Experimental evidence suggests involvement of inflammatory and autoimmune processes in pathogenesis of PH/PAH, however the triggering and disease-promoting mechanisms remain unknown. The complement system is a key arm of innate immunity implicated in various pro-inflammatory and autoimmune diseases, yet, surprisingly little is known about the role of complement in PH/PAH pathogenesis. The preponderance of the existing data associates complement with PH/PAH via analysis of plasma and does not study the lung directly. Therefore, we aimed to resolve this by analyzing both the mechanisms of local lung-specific complement activation and the correlation of dysregulated plasma complement to clinical outcome in PAH patients. In our recent studies, reviewed herein, we show, for the first time, that  immunoglobulin-driven activation of the complement cascade, specifically its alternative pathway, in the pulmonary perivascular areas, is a key mechanism initiating pro-inflammatory processes in the early stage of experimental hypoxic PH (a form of "sterile inflammation"). In human patients with end-stage PAH, we have demonstrated that perivascular deposition of immunoglobulin G (IgG) and activation of the complement cascade are "longitudinally" persistent in the disease. We also showed, using unbiased network analysis, that plasma complement signaling, including again the Alternative pathway, is a prognostic factor of survival in patients with idiopathic PAH (IPAH). Based on these initial findings, we suggest that vascular-specific, immunoglobulin-driven dysregulated complement signaling triggers and maintains pulmonary vascular remodeling and PH. Future experiments in this area would facilitate discoveries on whether complement signaling can serve both as a biomarker and therapeutic target in PH/PAH.

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.

Pathogenesis of atherosclerosis in the tunica intima, media, and adventitia of coronary arteries: An updated review

Atherosclerosis is a chronic inflammatory disease of arteries and it affects the structure and function of all three layers of the coronary artery wall. Current theories suggest that the dysfunction of endothelial cells is one of the initial steps in the development of atherosclerosis. The view that the tunica intima normally consists of a single layer of endothelial cells attached to the subendothelial layer and internal elastic membrane has been questioned in recent years. The structure of intima changes with age and it becomes multilayered due to migration of smooth muscle cells from the media to intima. At this stage, the migration and proliferation of smooth muscle cells do not cause pathological changes in the intima. The multilayering of intima is classically considered to be an important stage in the development of atherosclerosis, but in fact atherosclerotic plaques develop only focally due to the interplay of various processes that involve the resident and invading inflammatory cells. The tunica media consists of multiple layers of smooth muscle cells that produce the extracellular matrix, and this layer normally does not contain microvessels. During the development of atherosclerosis, the microvessels from the tunica adventitia or from the lumen may penetrate thickened media to provide nutrition and oxygenation. According to some theories, the endothelial dysfunction of these nutritive vessels may significantly contribute to the atherosclerosis of coronary arteries. The adventitia contains fibroblasts, progenitor cells, immune cells, microvessels, and adrenergic nerves. The degree of inflammatory cell infiltration into the adventitia, which can lead to the formation of tertiary lymphoid organs, correlates with the severity of atherosclerotic plaques. Coronary arteries are surrounded by perivascular adipose tissue that also participates in the atherosclerotic process.

Monocyte-to-High-Density Lipoprotein Ratio Predicts the Outcome of Acute Ischemic Stroke

Aim: Monocyte-to-high-density lipoprotein ratio (MHR) recently emerged as an inflammatory marker and has been reported to be a novel prognostic indicator of cardiovascular diseases. However, the relationship between MHR and prognosis of acute ischemic stroke (AIS) remains unclear.

Methods: Consecutive AIS patients were prospectively identified from January 2015 to December 2017. Functional outcome was evaluated by the modified Rankin Scale (mRS). Poor outcome was defined as of mRS 3–6. Multivariate logistic regression analysis was conducted to evaluate the relationship between MHR and poor outcome.

Results: A total of 1090 AIS patients within 24 hours of the onset of symptoms were recruited. MHR was higher in poor outcome group compared to that in good outcome group [0.53 (0.37–0.69) vs. 0.48 (0.33–0.60), P = 0.007]. Multivariate logistic regression analysis indicated that higher MHR level was independently associated with the poor outcome at 3 months (OR 2.58, 95% CI, 1.21–5.51, P = 0.015), especially the stroke subtype of large artery atherosclerosis (OR 2.52, 95% CI, 1.03–6.19, P = 0.034). Receiver operating curve (ROC) analysis showed that the area under the ROC curves for MHR was 0.67 and the best predictive cutoff value of MHR was 0.51, with a sensitivity of 62.3% and a specificity of 66.5%.

Conclusions: MHR may be a significant and independent predictor of poor functional outcome in patients with AIS.

Dickkopf-3 in aberrant endothelial secretome triggers renal fibroblast activation and endothelial-mesenchymal transition

Background

Our laboratory has previously demonstrated that Sirt1endo-/- mice show endothelial dysfunction and exaggerated renal fibrosis, whereas mice with silenced endothelial transforming growth factor beta (TGF-β) signaling are resistant to fibrogenic signals. Considering the fact that the only difference between these mutant mice is confined to the vascular endothelium, this indicates that secreted substances contribute to these contrasting responses.

Methods

We performed an unbiased proteomic analysis of the secretome of renal microvascular endothelial cells (RMVECs) isolated from these two mutants. We cultured renal fibroblasts and RMVECs and used microfluidic devices for coculturing.

Results

Dickkopf-3 (DKK3), a putative ligand of the Wnt/β-catenin pathway, was present exclusively in the fibrogenic secretome. In cultured fibroblasts, DKK3 potently induced myofibroblast activation. In addition, DKK3 antagonized effects of DKK1, a known inhibitor of the Wnt pathway, in conversion of fibroblasts to myofibroblasts. In RMVECs, DKK3 induced endothelial-mesenchymal transition and impaired their angiogenic competence. The inhibition of endothelial outgrowth, enhanced myofibroblast formation and endothelial-mesenchymal transition were confirmed in coculture. In reporter DKK3-eGFP × Col3.6-GFPcyan mice, DKK3 was marginally expressed under basal conditions. Adriamycin-induced nephropathy resulted in upregulation of DKK3 expression in tubular and, to a lesser degree, endothelial compartments. Sulindac sulfide was found to exhibit superior Wnt pathway-suppressive action and decreased DKK3 signals and the extent of renal fibrosis.

Conclusions

In conclusion, this unbiased proteomic screen of the profibrogenic endothelial secretome revealed DKK3 acting as an agonist of the Wnt pathway, enhancing formation of myofibroblasts and endothelial-mesenchymal transition and impairing angiogenesis. A potent inhibitor of the Wnt pathway, sulindac sulfide, suppressed nephropathy-induced DKK3 expression and renal fibrosis.

miR-27a regulates vascular remodeling by targeting endothelial cells' apoptosis and interaction with vascular smooth muscle cells in aortic dissection

Rationale: Aortic dissection (AD) is caused by functional disorder of cells in the aortic wall, which is largely attributed to vascular remodeling. Therapeutic strategies for AD remain limited due to our incomplete understanding of the role of endothelial cells (ECs) in AD pathogenesis. This study aimed to identify the regulatory role of miR-27a in AD and provide a mechanistic basis for a non-invasive treatment of AD.

Methods: We harvested aortas from normal and AD patients to explore the expression of miR-27a. In vitro and in vivo assays were preformed to explore the biological effects of differential expression of miR-27a in ECs and its regulatory effect on AD.

Results: MiR-27a was lower in intima of AD samples than in healthy individuals. Downregulation of miR-27a in EC was due to up-regulated expression of fas-associated protein with death domain (FADD) and the activation of apoptosis pathway, which led to apoptosis of ECs. Migration of vascular smooth muscle cells was promoted by EC after downregulation of miR-27a due to enhancement of growth/differentiation factor 8 (GDF8) and repression of matrix metalloproteinase-20 (MMP20) in the co-culture system supernatants. Increase in FADD and apoptosis of ECs to induce AD was shown using mouse models of AD in which miR-27a was stably knocked-down by antagomir. Up-regulation of miR-27a by agomir led to a protective effect on AD.

Conclusion: Treatment with miR-27a activator that targets apoptosis of ECs strongly diminished occurrence of AD, providing a new strategy for this disease.

Hot topics in the mechanisms of pulmonary arterial hypertension disease: cancer-like pathobiology, the role of the adventitia, systemic involvement, and right ventricular failure

In order to intervene appropriately and develop disease-modifying therapeutics for pulmonary arterial hypertension, it is crucial to understand the mechanisms of disease pathogenesis and progression. We herein discuss four topics of disease mechanisms that are currently highly debated, yet still unsolved, in the field of pulmonary arterial hypertension. Is pulmonary arterial hypertension a cancer-like disease? Does the adventitia play an important role in the initiation of pulmonary vascular remodeling? Is pulmonary arterial hypertension a systemic disease? Does capillary loss drive right ventricular failure? While pulmonary arterial hypertension does not replicate all features of cancer, anti-proliferative cancer therapeutics might still be beneficial in pulmonary arterial hypertension if monitored for safety and tolerability. It was recognized that the adventitia as a cell-rich compartment is important in the disease pathogenesis of pulmonary arterial hypertension and should be a therapeutic target, albeit the data are inconclusive as to whether the adventitia is involved in the initiation of neointima formation. There was agreement that systemic diseases can lead to pulmonary arterial hypertension and that pulmonary arterial hypertension can have systemic effects related to the advanced lung pathology, yet there was less agreement on whether idiopathic pulmonary arterial hypertension is a systemic disease per se. Despite acknowledging the limitations of exactly assessing vascular density in the right ventricle, it was recognized that the failing right ventricle may show inadequate vascular adaptation resulting in inadequate delivery of oxygen and other metabolites. Although the debate was not meant to result in a definite resolution of the specific arguments, it sparked ideas about how we might resolve the discrepancies by improving our disease modeling (rodent models, large-animal studies, studies of human cells, tissues, and organs) as well as standardization of the models. Novel experimental approaches, such as lineage tracing and better three-dimensional imaging of experimental as well as human lung and heart tissues, might unravel how different cells contribute to the disease pathology.

Cytokines, growth factors and proteases in medium and large vessel vasculitis

Giant cell arteritis and Takayasu arteritis are autoimmune vasculitides that cause aneurysm formation and tissue infarction. Extravascular inflammation consists of an intense acute phase response. Deeper understanding of pathogenic events in the vessel wall has highlighted the loss of tissue protective mechanisms, the intrusion of immune cells into "forbidden territory", and the autonomy of self-renewing vasculitic infiltrates. Adventitial vasa vasora critically control vessel wall access and drive differentiation of tissue-invasive T cells. Selected T cells establish tissue residency and build autonomous, self-sufficient inflammatory lesions. Pathogenic effector T cells intrude and survive due to failed immune checkpoint inhibition. Vasculitis-sustaining T cells and macrophages provide a broad portfolio of effector functions, involving heterogeneous populations of pro-inflammatory T cells and diverse macrophage subsets that ultimately induce wall capillarization and intimal hyperplasia. Redirecting diagnostic and therapeutic strategies from control of extravascular inflammatory markers to suppression of vascular inflammation will improve disease management.

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.

Hypoxia inducible factor 1α in vascular smooth muscle cells promotes angiotensin II-induced vascular remodeling via activation of CCL7-mediated macrophage recruitment

The process of vascular remodeling is associated with increased hypoxia. However, the contribution of hypoxia-inducible factor 1α (HIF1α), the key transcription factor mediating cellular hypoxic responses, to vascular remodeling is established, but not completely understood. In the angiotensin II (Ang II)-induced vascular remodeling model, HIF1α was increased and activated in vascular smooth muscle cells (VSMCs). Selective genetic disruption of Hif1a in VSMCs markedly ameliorated Ang II-induced vascular remodeling, as revealed by decreased blood pressure, aortic thickness, collagen deposition, inflammation, and aortic stiffness. VSMC Hif1a deficiency also specifically suppressed Ang II-induced infiltration of CD45⁺CD11b⁺F4/80⁺CD206⁻ M1 macrophages into the vessel. Mechanistically, HIF1α deficiency in VSMCs dramatically suppressed the expression of CCL7, a chemokine critical for macrophage recruitment. Bioinformatic analysis and chromatin immunoprecipitation assays revealed three functional hypoxia-response elements in the Ccl7 promoter, indicating that Ccl7 is a direct HIF1α target gene. Blocking CCL7 with antibody in vivo alleviated Ang II-induced hypertension and vascular remodeling, coincident with decreased macrophage infiltration. This study provides direct evidence that HIF1α activation in VSMCs exacerbates Ang II-induced macrophage infiltration and resultant vascular remodeling via its target gene Ccl7, and thus may serve as a potential therapeutic target for remodeling-related vascular disease.

Coronary Artery Remodeling and Fibrosis With Continuous-Flow Left Ventricular Assist Device Support

BACKGROUND

Coronary artery fluid dynamics may be altered because of the nonphysiological flow seen in continuous-flow left ventricular assist devices (CF-LVADs). Our aim was to study the structure and composition of coronary vessels after CF-LVAD.

METHODS AND RESULTS

Coronary arteries were collected from patients with heart failure (HF) at the time of transplantation, of whom 15 were supported with a CF-LVAD before transplant (HF+LVAD group) and 9 were not (HF non-LVAD group). In addition, coronary samples were obtained from 5 nonfailing age-matched donors (nonfailing group). Histological analysis was performed to quantify coronary morphology, composition, vascular fibrosis, and vasa vasorum density. The age and sex mix of the 3 groups were similar, and the mean duration of LVAD support was 213 days. Compared with patients with HF and nonfailing donors, the arteries from patients with HF+LVAD had expansion of the adventitia, breakdown of the internal elastic lamina, and increased adventitial collagen deposition and density of vasa vasorum.

CONCLUSIONS

Among patients supported with CF-LVADs, the coronary arteries develop marked remodeling with increased adventitial fibrosis. The physiological consequences of these structural changes are unknown, but it is possible that arterial contractility may be impaired, thus limiting coronary flow reserve and promoting myocardial ischemia. This may contribute to CF-LVAD complications, such as ventricular arrhythmias and right ventricular failure. As more patients receive CF-LVADs and new pump technology attempts to modulate flow profiles and pulsatility, further research is needed to understand the mechanisms and long-term sequela of these changes in coronary arteries and other vascular beds.

NLRC5 inhibits neointima formation following vascular injury and directly interacts with PPARγ

NLR Family CARD Domain Containing 5 (NLRC5), an important immune regulator in innate immunity, is involved in regulating inflammation and antigen presentation. However, the role of NLRC5 in vascular remodeling remains unknown. Here we report the role of NLRC5 on vascular remodeling and provide a better understanding of its underlying mechanism. Nlrc5 knockout (Nlrc5^−/−) mice exhibit more severe intimal hyperplasia compared with wild-type mice after carotid ligation. Ex vivo data shows that NLRC5 deficiency leads to increased proliferation and migration of human aortic smooth muscle cells (HASMCs). NLRC5 binds to PPARγ and inhibits HASMC dedifferentiation. NACHT domain of NLRC5 is essential for the interaction with PPARγ and stimulation of PPARγ activity. Pioglitazone significantly rescues excessive intimal hyperplasia in Nlrc5^−/− mice and attenuates the increased proliferation and dedifferentiation in NLRC5-deficient HASMCs. Our study demonstrates that NLRC5 regulates vascular remodeling by directly inhibiting SMC dysfunction via its interaction with PPARγ.

NLRC5 is known for its role in inflammation and antigen presentation. Here Luan et al. find that NLRC5 protects mice from intimal hyperplasia following vascular injury, and regulates the response of vascular smooth muscle cells to injury through direct interaction with PPARγ.

2,3,7,8-Tetrachlorodibenzo-p-dioxin promotes injury-induced vascular neointima formation in mice

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental pollutant that causes cardiovascular toxicity. The phenotypic transformation of vascular smooth muscle cells (VSMCs) from the contractile to the synthetic phenotype is a hallmark of vascular response to injury. However, the precise role and molecular mechanism of TCDD in vascular remodeling remains unknown. In the present study, we found that TCDD treatment promoted VSMC phenotypic transition from contractile to synthetic phenotype and exaggerated vascular neointimal hyperplasia after wire injury in mice. TCDD treatment enhanced VSMC entry into cell cycle from G0/G1 phase to S and G2/M phase. The expression of cyclin D1, cyclin-dependent kinase 4 (CDK4), and its phosphorylation were coordinately increased in response to TCDD treatment. Knocking down of aryl hydrocarbon receptor (AHR) inhibited VSMC phenotypic transition induced by TCDD and promoted S/G2 phase cell cycle arrest. TCDD treatment markedly increased oncogenic c-Jun gene expression in VSMCs. ChIP assay revealed the direct binding of AHR on the promoter of c-Jun to up-regulate the mRNA expression of c-Jun. Silencing of c-Jun gene enhanced the expression of p53 and p21, whereas attenuated the expression of CDK4 and cyclin D1 leading to the decrease in the TCDD-stimulated VSMC proliferation and synthetic phenotype transition in vitro. In vivo study showed that genetic ablation of c-Jun in VSMCs restricted injury-induced neointimal hyperplasia in TCDD-treated mice. Thus, TCDD exposure exaggerated injury-induced vascular remodeling by the activation of AHR and up-regulation of the expression of its target gene c-Jun, indicating that inhibition of AHR may be a promising prevention strategy for TCDD-associated cardiovascular diseases.-Guo, S., Zhang, R., Liu, Q., Wan, Q., Wang, Y., Yu, Y., Liu, G., Shen, Y., Yu, Y., Zhang, J. 2,3,7,8-Tetrachlorodibenzo-p-dioxin promotes injury-induced vascular neointima formation in mice.

The role of vascular smooth muscle cell membrane-bound thrombomodulin in neointima formation

BACKGROUND AND AIMS

Thrombomodulin (TM) is an endothelial cell membrane-bound anticoagulant protein expressed in normal arteries. After vascular injury, medial and neointimal smooth muscle cells (SMCs) exhibit large amounts of TM. The purpose of this study was to investigate the physiological significance of vascular SMC-bound TM.

METHODS

The morphology, expression of phenotype markers and cell behaviors of cultured aortic SMCs after knockdown of TM were observed. Transgenic mice with SMC-specific TM deletion were generated, and carotid neointima formation was induced by carotid ligation.

RESULTS

Cultured human aortic SMCs displayed a synthetic phenotype with a rhomboid-shaped morphology and expressed TM. TM knockdown induced a spindle-shaped change in morphology with an increased expression of contractile phenotype marker and decreased expression of synthetic phenotype marker. TM knockdown not only attenuated the proliferation of SMCs but also reduced tumor necrosis factor-α-induced nuclear factor-κB activation and interlukin-6 production. In a carotid artery ligation model, transgenic mice with SMC-specific TM deletion (SM22-cre^tg/TM^flox/flox) had significantly less cellular proliferation in arterial walls compared with wild type mice (SM22-cre^tg/TM^+/+). The neointima area and neointima/media area ratio were smaller in SM22-cre^tg/TM^flox/flox mice at 4 weeks after ligation.

CONCLUSIONS

Our results indicate that vascular SMC-bound TM plays a role in changes of the SMC phenotype. It also influences SMC cell behavior and injury-induced neointima formation.

Vascular Smooth Muscle Cell Plasticity and Autophagy in Dissecting Aortic Aneurysms

Objective- Recent studies suggested the occurrence of phenotypic switching of vascular smooth muscle cells (VSMCs) during the development of aortic aneurysm (AA). However, lineage-tracing studies are still lacking, and the behavior of VSMCs during the formation of dissecting AA is poorly understood. Approach and Results- We used multicolor lineage tracing of VSMCs to track their fate after injury in murine models of Ang II (angiotensin II)-induced dissecting AA. We also addressed the direct impact of autophagy on the response of VSMCs to AA dissection. Finally, we studied the relevance of these processes to human AAs. Here, we show that a subset of medial VSMCs undergoes clonal expansion and that VSMC outgrowths are observed in the adventitia and borders of the false channel during Ang II-induced development of dissecting AA. The clonally expanded VSMCs undergo phenotypic switching with downregulation of VSMC differentiation markers and upregulation of phagocytic markers, indicative of functional changes. In particular, autophagy and endoplasmic reticulum stress responses are activated in the injured VSMCs. Loss of autophagy in VSMCs through deletion of autophagy protein 5 gene ( Atg5) increases the susceptibility of VSMCs to death, enhances endoplasmic reticulum stress activation, and promotes IRE (inositol-requiring enzyme) 1α-dependent VSMC inflammation. These alterations culminate in increased severity of aortic disease and higher incidence of fatal AA dissection in mice with VSMC-restricted deletion of Atg5. We also report increased expression of autophagy and endoplasmic reticulum stress markers in VSMCs of human dissecting AAs. Conclusions- VSMCs undergo clonal expansion and phenotypic switching in Ang II-induced dissecting AAs in mice. We also identify a critical role for autophagy in regulating VSMC death and endoplasmic reticulum stress-dependent inflammation with important consequences for aortic wall homeostasis and repair.

FGF signaling contributes to atherosclerosis by enhancing the inflammatory response in vascular smooth muscle cells

The contractile to synthetic phenotypic switching of vascular smooth muscle cells (VSMCs) in response to fibroblast growth factor (FGF) has been previously described. However, the role of the inflammatory response induced by FGF signaling in VSMCs and its occurrence in atherosclerosis remains unclear. In the present study, FGF signaling promoted a contractile to secretory phenotypic transition in VSMCs. VSMCs (primary human aortic smooth muscle cells) treated with FGF exhibited a decrease in the protein expression levels of factors involved in contractility and the secretion of various chemokines was increased, as assessed by reverse transcription-quantitative PCR and ELISA. Additionally, inhibition of FGF signaling by silencing FGF receptor substrate 2 (FRS2) decreased the protein expression levels of various chemokines. Furthermore, VSMCs in the medial layers of arteries from apolipoprotein E-deficient mice and human atherosclerotic samples exhibited an increase in FGF signaling that was identified to be associated with an increase in the protein expression levels of pro-inflammatory molecules, including C-C motif chemokine ligand 2, C-X-C motif chemokine ligand (CXCL) 9, CXCL10 and CXCL11, compared with wild-type mice and healthy control samples, respectively. The present results suggested that FGF signaling induced dedifferentiation of contractile VSMCs and the transition to a secretory phenotype, which may be involved in the progression of atherosclerosis. Collectively, the present results suggested that the FGF signaling pathway may represent a novel target for the treatment of atherosclerosis.

CD28 Signaling Controls Metabolic Fitness of Pathogenic T Cells in Medium and Large Vessel Vasculitis

BACKGROUND

In giant cell arteritis, vessel-wall infiltrating CD4 T cells and macrophages form tissue-destructive granulomatous infiltrates, and the artery responds with a maladaptive response to injury, leading to intramural neoangiogenesis, intimal hyperplasia, and luminal occlusion. Lesion-residing T cells receive local signals, which represent potential therapeutic targets.

OBJECTIVES

The authors examined how CD28 signaling affects vasculitis induction and maintenance, and which pathogenic processes rely on CD28-mediated T-cell activation.

METHODS

Vasculitis was induced by transferring peripheral blood mononuclear cells from giant cell arteritis patients into immunodeficient NSG mice engrafted with human arteries. Human artery-NSG chimeras were treated with anti-CD28 domain antibody or control antibody. Treatment effects and immunosuppressive mechanisms were examined in vivo and in vitro applying tissue transcriptome analysis, immunohistochemistry, flow cytometry, and immunometabolic analysis.

RESULTS

Blocking CD28-dependent signaling markedly reduced tissue-infiltrating T cells and effectively suppressed vasculitis. Mechanistic studies implicated CD28 in activating AKT signaling, T-cell proliferation and differentiation of IFN-γ and IL-21-producing effector T cells. Blocking CD28 was immunosuppressive by disrupting T-cell metabolic fitness; specifically, the ability to utilize glucose. Expression of the glucose transporter Glut1 and of glycolytic enzymes as well as mitochondrial oxygen consumption were all highly sensitive to CD28 blockade. Also, induction and maintenance of CD4+CD103+ tissue-resident memory T cells, needed to replenish the vasculitic infiltrates, depended on CD28 signaling. CD28 blockade effectively suppressed vasculitis-associated remodeling of the vessel wall.

CONCLUSIONS

CD28 stimulation provides a metabolic signal required for pathogenic effector functions in medium and large vessel vasculitis. Disease-associated glycolytic activity in wall-residing T-cell populations can be therapeutically targeted by blocking CD28 signaling.

Disruption of the Gut Microbiota With Antibiotics Exacerbates Acute Vascular Rejection

BACKGROUND

The gut microbiota influences many immunological processes but how its disruption affects transplant rejection is poorly understood.

METHODS

Interposition grafting of aortic segments was used to examine vascular rejection. The gut microbiota was disrupted in graft recipients using an antibiotic cocktail (ampicillin, vancomycin, metronidazole, neomycin sulfate) in their drinking water.

RESULTS

Treatment of mice with antibiotics severely reduced total bacterial content in the intestine and disrupted the bacterial composition. Short-term treatment of mice for only the first 3 weeks of life resulted in the population of the intestine in mature mice with bacterial communities that were mildly different from untreated mice, containing slightly more Clostridia and less Bacteroides. Antibiotic disruption of the gut microbiota of graft recipients, either for their entire life or only during the first 3 weeks of life, resulted in increased medial injury of allograft arteries that is reflective of acute vascular rejection but did not affect intimal thickening reflective of transplant arteriosclerosis. Exacerbated vascular rejection resulting from disruption of the gut microbiota was related to increased infiltration of allograft arteries by neutrophils.

CONCLUSIONS

Disruption of the gut microbiota early in life results in exacerbation of immune responses that cause acute vascular rejection.

The biphasic effects of the oxLDL/β2GPI/anti-β2GPI complex on VSMC proliferation and apoptosis

In our previous study, the oxLDL/β₂GPI/anti-β₂GPI complex was demonstrated to further enhance the foam cell formation and migration of VSMC, as well as the expression of inflammatory cytokines, via the TLR4/NF-κB pathway. However, sparse information is available on other pro-atherogenic pathogenic effects of the oxLDL/β₂GPI/anti-β₂GPI complex, such as effects on proliferation and apoptosis. In the present study, we focused on the biphasic effects and underlying mechanisms of the oxLDL/β₂GPI/anti-β₂GPI complex on VSMC survival. The data showed that short exposure to the oxLDL/β₂GPI/anti-β₂GPI complex could activate NF-κB and ERK1/2 pathways and stimulate cell proliferation in VSMC. In contrast, longer exposure increased the level of p38 pathway activation and cell apoptosis. Additionally, the promotion effect of the oxLDL/β₂GPI/anti-β₂GPI complex on both proliferation and apoptosis, as well as signaling pathway activation, was stronger than that of the other control groups. The use of selective blockers showed that TLR4/NF-κB and ERK1/2 partly mediated oxLDL/β₂GPI/anti-β₂GPI complex-induced proliferation and had an inhibitory effect on complex-stimulated apoptosis. Conversely, TLR2/p38 partly mediated oxLDL/β₂GPI/anti-β₂GPI complex-induced apoptosis and had a negative effect on complex-stimulated proliferation. Specific inhibitors of NF-κB and ERK1/2 activation could augment the oxLDL/β₂GPI/anti-β₂GPI complex-induced phosphorylation of p38 and vice versa. Under pretreatment with NADPH oxidase inhibitors, intracellular ROS generation was confirmed to participate in oxLDL/β₂GPI/anti-β₂GPI complex-induced proliferation and apoptosis, as well as the phosphorylation of NF-κB and MAPKs. Taken together, our data clearly revealed that the oxLDL/β₂GPI/anti-β₂GPI complex had biphasic effects on VSMC survival, partly mediated by ROS-induced NF-κB and MAPKs activation. The TLR4/NF-κB and TLR2/p38 pathways played supporting roles in this dual effects-initiated signal network, and there is a trade-off relationship between the phosphorylation of NF-κB, ERK1/2 and p38. The dual effects of the oxLDL/β₂GPI/anti-β₂GPI complex on VSMC survival contribute to the development of the structure typical of atherosclerotic lesions, particularly focal excessive growth alternating with necrosis.

AIP1 Suppresses Transplant Arteriosclerosis Through Inhibition of Vascular Smooth Muscle Cell Inflammatory Response to IFNγ

IFNγ-induced vascular smooth muscle cells (VSMCs) inflammatory response plays a key role in transplant arteriosclerosis (TA). However, the mechanisms regulating this process remains poorly defined. Here, we show that ASK1-interacting protein 1 (AIP1) deletion markedly augments the expression of IFNγ-induced chemokines in mouse aortic allografts. Subsequently, donor arterial grafts from AIP1 deficient mice exhibited an accelerated development of TA. Furthermore, AIP1 knockdown significantly increased IFNγ signaling activation in cultured VSMCs and thus enhances chemokines production in response to IFNγ. Together, we conclude that AIP1 functions as an inhibitor of VSMCs inflammation by regulating IFNγ signaling and therefore suppresses TA progression. Our findings suggest that AIP1 might be a potential therapeutic target for chronic transplant rejection. Anat Rec, 302:1587-1593, 2019. © 2018 American Association for Anatomy.

Modeling mechano-driven and immuno-mediated aortic maladaptation in hypertension

Uncontrolled hypertension is a primary risk factor for diverse cardiovascular diseases and thus remains responsible for significant morbidity and mortality. Hypertension leads to marked changes in the composition, structure, properties, and function of central arteries; hence, there has long been interest in quantifying the associated wall mechanics. Indeed, over the past 20 years there has been increasing interest in formulating mathematical models of the evolving geometry and biomechanical behavior of central arteries that occur during hypertension. In this paper, we introduce a new mathematical model of growth (changes in mass) and remodeling (changes in microstructure) of the aortic wall for an animal model of induced hypertension that exhibits both mechano-driven and immuno-mediated matrix turnover. In particular, we present a bilayered model of the aortic wall to account for differences in medial versus adventitial growth and remodeling and we include mechanical stress and inflammatory cell density as determinants of matrix turnover. Using this approach, we can capture results from a recent report of adventitial fibrosis that resulted in marked aortic maladaptation in hypertension. We submit that this model can also be used to identify novel hypotheses to guide future experimentation.

Immune cells and vasa vasorum in the tunica media of atherosclerotic coronary arteries

In coronary artery disease (CAD), the disruption of the tunica media immune privilege manifests as increased leukocyte infiltration and the formation of vasa vasorum. We aimed to characterize the immune privilege status of the tunica media in human coronary arteries (CAs) with atherosclerotic plaques, by comparing the abundance and composition of immune-cell infiltrates within the individual arterial-wall layers, and by evaluating vasa vasorum neovascularization of the tunica media. The tissue samples were obtained from 36 symptomatic patients with diffuse CAD (aged 60-72 years) who underwent coronary endarterectomy. T and B cells, macrophages and endothelial cells in the CAs were detected by immunohistochemistry. Morphological analysis of CAs showed significant atherosclerotic changes in all specimens. In the media, we observed damage and loss of smooth muscle cells, destruction of the extracellular matrix architecture, and fibrosis. There were 43.3% of immune cells in the intima, 50% in the adventitia, and 6.7% in the media. In the media, 51.1% of the immune cells were T cells (p ˂ 0.001 compared to B cells and macrophages; ANOVA, Scheffe post hoc analysis), 23.5% were B cells, and 25.4% were macrophages. The number of vasa vasorum in the media was 1 in 38.9% of CAs, 2-3 in 36.1%, and ≥4 in 25% of CAs. Our results indicate that, in atherosclerotic CAs, the immune privilege of the media is disrupted by the infiltration of T and B cells, macrophages, and the presence of vasa vasorum.