Molecular mechanisms of decreased smooth muscle differentiation marker expression after vascular injury

The mitochondrial protease ClpP is a druggable target that controls VSMC phenotype by a SIRT1-dependent mechanism

Vascular smooth muscle cells (VSMCs), known for their remarkable lifelong phenotypic plasticity, play a pivotal role in vascular pathologies through their ability to transition between different phenotypes. Our group discovered that the deficiency of the mitochondrial protein Poldip2 induces VSMC differentiation both in vivo and in vitro. Further comprehensive biochemical investigations revealed Poldip2's specific interaction with the mitochondrial ATPase caseinolytic protease chaperone subunit X (CLPX), which is the regulatory subunit for the caseinolytic protease proteolytic subunit (ClpP) that forms part of the ClpXP complex - a proteasome-like protease evolutionarily conserved from bacteria to humans. This interaction limits the protease's activity, and reduced Poldip2 levels lead to ClpXP complex activation. This finding prompted the hypothesis that ClpXP complex activity within the mitochondria may regulate the VSMC phenotype. Employing gain-of-function and loss-of-function strategies, we demonstrated that ClpXP activity significantly influences the VSMC phenotype. Notably, both genetic and pharmacological activation of ClpXP inhibits VSMC plasticity and fosters a quiescent, differentiated, and anti-inflammatory VSMC phenotype. The pharmacological activation of ClpP using TIC10, currently in phase III clinical trials for cancer, successfully replicates this phenotype both in vitro and in vivo and markedly reduces aneurysm development in a mouse model of elastase-induced aortic aneurysms. Our mechanistic exploration indicates that ClpP activation regulates the VSMC phenotype by modifying the cellular NAD+/NADH ratio and activating Sirtuin 1. Our findings reveal the crucial role of mitochondrial proteostasis in the regulation of the VSMC phenotype and propose the ClpP protease as a novel, actionable target for manipulating the VSMC phenotype.

Small nucleolar RNA host gene 18 controls vascular smooth muscle cell contractile phenotype and neointimal hyperplasia

AIMS

Long non-coding RNA (LncRNA) small nucleolar RNA host gene 18 (SNHG18) has been widely implicated in cancers. However, little is known about its functional involvement in vascular diseases. Herein, we attempted to explore a role for SNHG18 in modulating vascular smooth muscle cell (VSMC) contractile phenotype and injury-induced neointima formation.

METHODS AND RESULTS

Analysis of single-cell RNA sequencing and transcriptomic datasets showed decreased levels of SNHG18 in injured and atherosclerotic murine and human arteries, which is positively associated with VSMC contractile genes. SNHG18 was upregulated in VSMCs by TGFβ1 through transcription factors Sp1 and SMAD3. SNHG18 gene gain/loss-of-function studies revealed that VSMC contractile phenotype was positively regulated by SNHG18. Mechanistic studies showed that SNHG18 promotes a contractile VSMC phenotype by up-regulating miR-22-3p. SNHG18 up-regulates miR-22 biogenesis and miR-22-3p production by competitive binding with the A-to-I RNA editing enzyme, adenosine deaminase acting on RNA-2 (ADAR2). Surprisingly, we observed that ADAR2 inhibited miR-22 biogenesis not through increasing A-to-I editing within primary miR-22, but by interfering with the binding of microprocessor complex subunit DGCR8 to primary miR-22. Importantly, perivascular SNHG18 overexpression in the injured vessels dramatically up-regulated the expression levels of miR-22-3p and VSMC contractile genes, and prevented injury-induced neointimal hyperplasia. Such modulatory effects were reverted by miR-22-3p inhibition in the injured arteries. Finally, we observed a similar regulator role for SNHG18 in human VSMCs and a decreased expression level of both SNHG18 and miR-22-3p in diseased human arteries; and we found that the expression level of SNHG18 was positively associated with that of miR-22-3p in both healthy and diseased human arteries.

CONCLUSION

We demonstrate that SNHG18 is a novel regulator in governing VSMC contractile phenotype and preventing injury-induced neointimal hyperplasia. Our findings have important implications for therapeutic targeting snhg18/miR-22-3p signalling in vascular diseases.

SM22α deficiency: promoting vascular fibrosis via SRF-SMAD3-mediated activation of Col1a2 transcription following arterial injury

Vascular fibrosis, characterized by increased Type I collagen expression, significantly contributes to vascular remodeling. Our previous studies show that disrupting the expression of SM22α (aka SM22, Tagln) induces extensive vascular remodeling following arterial injury, involving oxidative stress, inflammation, and chondrogenesis within the vessel wall. This study aims to investigate the molecular mechanisms underlying the transcription of Col1a2 , a key fibrotic extracellular matrix marker. We observed upregulation of COL1A2 in the arterial wall of Sm22 -/- mice following carotid injury. Bioinformatics and molecular analyses reveal that Col1a2 transcription depends on a CArG box in the promoter, activated synergistically by SRF and SMAD3. Notably, we detected enhanced nuclear translocation of both SRF and SMAD3 in the smooth muscle cells of the injured carotid artery in Sm22 -/- mice. These findings demonstrate that SM22 deficiency regulates vascular fibrosis through the interaction of SRF and the SMAD3-mediated canonical TGF-β1 signal pathway, suggesting SM22α as a potential therapeutic target for preventing vascular fibrosis.

Vascular dysfunction caused by loss of Brn-3b/POU4F2 transcription factor in aortic vascular smooth muscle cells is linked to deregulation of calcium signalling pathways

Phenotypic and functional changes in vascular smooth muscle cells (VSMCs) contribute significantly to cardiovascular diseases (CVD) but factors driving early adverse vascular changes are poorly understood. We report on novel and important roles for the Brn-3b/POU4F2 (Brn-3b) transcription factor (TF) in controlling VSMC integrity and function. Brn-3b protein is expressed in mouse aorta with localisation to VSMCs. Male Brn-3b knock-out (KO) aortas displayed extensive remodelling with increased extracellular matrix (ECM) deposition, elastin fibre disruption and small but consistent narrowing/coarctation in the descending aortas. RNA sequencing analysis showed that these effects were linked to deregulation of genes required for calcium (Ca2+) signalling, vascular contractility, sarco-endoplasmic reticulum (S/ER) stress responses and immune function in Brn-3b KO aortas and validation studies confirmed changes in Ca2+ signalling genes linked to increased intracellular Ca2+ and S/ER Ca2+ depletion [e.g. increased, Cacna1d Ca2+ channels; ryanodine receptor 2, (RyR2) and phospholamban (PLN) but reduced ATP2a1, encoding SERCA1 pump] and chaperone proteins, Hspb1, HspA8, DnaJa1 linked to increased S/ER stress, which also contributes to contractile dysfunction. Accordingly, vascular rings from Brn-3b KO aortas displayed attenuated contractility in response to KCl or phenylephrine (PE) while Brn-3b KO-derived VSMC displayed abnormal Ca2+ signalling following ATP stimulation. This data suggests that Brn-3b target genes are necessary to maintain vascular integrity /contractile function and deregulation upon loss of Brn-3b will contribute to contractile dysfunction linked to CVD.

Blockade of CD47 function attenuates restenosis by promoting smooth muscle cell efferocytosis and inhibiting their migration and proliferation

Cluster of differentiation 47 (CD47) plays an important role in the pathophysiology of various diseases including atherosclerosis, but its role in neointimal hyperplasia which contributes to restenosis, has not been studied. Using molecular approaches in combination with a mouse vascular endothelial denudation model, we studied the role of CD47 in injury-induced neointimal hyperplasia. We determined that thrombin induced CD47 expression both in human and mouse aortic smooth muscle cells (HASMCs and MASMCs). In exploring the mechanisms, we found that the protease-activated receptor 1 (PAR1)-Gα protein q/11 (Gαq/11)-phospholipase Cβ3 (PLCβ3)-nuclear factor of activated T cells c1 (NFATc1) signaling axis regulates thrombin-induced CD47 expression in HASMCs. Depletion of CD47 levels using its siRNA or interference of its function by its blocking antibody (bAb) blunted thrombin-induced migration and proliferation of HASMCs and MASMCs. In addition, we found that thrombin-induced HASMC migration requires CD47 interaction with integrin β3. On the other hand, thrombin-induced HASMC proliferation was dependent on CD47's role in nuclear export and degradation of CDK-interacting protein 1 (p21Cip1). In addition, suppression of CD47 function by its bAb rescued HASMC efferocytosis from inhibition by thrombin. We also found that vascular injury induces CD47 expression in intimal SMCs and that inhibition of CD47 function by its bAb, while alleviating injury-induced inhibition of SMC efferocytosis, attenuated SMC migration and proliferation resulting in reduced neointima formation. Thus, these findings reveal a pathological role for CD47 in neointimal hyperplasia.

High shear stress attenuated arterial neointimal hyperplasia accompanied by changes in yes-associated protein/jun N-terminal kinase/vascular cell adhesion protein 1 expression

BACKGROUND AND OBJECTIVES

Abnormal neointimal hyperplasia (NIH) is known as the predominant mechanism in the pathogenesis of arterial restenosis after balloon angioplasty. Low shear stress (SS) is known to augment balloon injury-induced NIH. The aim of this study is to study the effect and mechanisms of an increase of shear stress caused by arteriovenous fistula could alleviate arterial NIH caused by balloon injury.

METHODS AND RESULTS

Eighteen male rabbits were randomly divided into three groups: BI-the rabbits received a balloon injury to right common carotid artery (CCA). BI+AVF-the rabbits received a balloon injury to right CCA and a carotid-jugular AVF. Control-the animals received no surgery. After 21 days, CCA samples were harvested for histological staining, immunohistochemistry, and western blot analysis. The luminal shear stress of the BI+AVF group increased from 13.8 ± 1.0 dyn/cm² before surgery to 30.9 ± 1.7 dyn/cm² right after surgery (p < 0.01). This value was higher than that of the BI or Control groups at any timepoint. The neointimal area and neointima/media area ratio in the BI+AVF group were significantly lower than those in the BI group. In the BI group, the cellular proliferation, the protein levels of yes-associated protein (YAP), connective tissue growth factor (CTGF), phospho-c-Jun N-terminal kinase (pJNK), and vascular cell adhesion protein 1 (VCAM1) increased, whereas the protein levels of SMCs specific genes decreased. In the BI+AVF group, the opposite effect was observed as cellular proliferation and the protein levels of YAP, CTGF, pJNK, and VCAM1 decreased, the protein levels of SMCs specific genes increased.

CONCLUSION

The arteriovenous fistula alleviated the balloon injury-induced arterial NIH. It elevated the luminal shear stress and inhibited SMCs phenotypic modulation to the synthetic state, as well as suppressing the over-activation of YAP, JNK, and VCAM1.

BAF60c prevents abdominal aortic aneurysm formation through epigenetic control of vascular smooth muscle cell homeostasis

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease. BAF60c, a unique subunit of the SWItch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex, is critical for cardiac and skeletal myogenesis, yet little is known about its function in the vasculature and, specifically, in AAA pathogenesis. Here, we found that BAF60c was downregulated in human and mouse AAA tissues, with primary staining to vascular smooth muscle cells (VSMCs), confirmed by single-cell RNA-sequencing. In vivo studies revealed that VSMC-specific knockout of Baf60c significantly aggravated both angiotensin II- (Ang II-) and elastase-induced AAA formation in mice, with a significant increase in elastin degradation, inflammatory cell infiltration, VSMC phenotypic switch, and apoptosis. In vitro studies showed that BAF60c knockdown in VSMCs resulted in loss of contractile phenotype, increased VSMC inflammation, and apoptosis. Mechanistically, we demonstrated that BAF60c preserved VSMC contractile phenotype by strengthening serum response factor (SRF) association with its coactivator P300 and the SWI/SNF complex and suppressing VSMC inflammation by promoting a repressive chromatin state of NF-κB target genes as well as preventing VSMC apoptosis through transcriptional activation of KLF5-dependent B cell lymphoma 2 (BCL2) expression. Our identification of the essential role of BAF60c in preserving VSMC homeostasis expands its therapeutic potential in preventing and treating AAA.

A network pharmacology technique used to investigate the potential mechanism of Ligustilide's effect on atherosclerosis

Ligustilide (LIG) is a major active ingredient in traditional Chinese medicines that is also found in plant rhizomes such as carrot, coriander, and others, and it has been demonstrated to have cardiovascular preventive benefits. However, the mechanisms through which LIG protects the cardiovascular and cerebrovascular systems in atherosclerosis (AS) remain unknown. This study was aimed to investigate the mechanisms of LIG in AS utilizing the network pharmacology and molecular docking, and then to validate the putative mechanism through experiments. The network pharmacological analysis indicated that a total of 55 were performed on LIG and AS intersection targets. The genes of LIG and AS intersection targets enriched in the regulation of receptor and enzyme activity, cytokines-related, and transcription factors, indicating that these targets were primarily involved in cell proliferation and migration, regulating cell differentiation and skeletal activities in the development of AS. Finally, molecular docking was used to validate the major targets of LIG and AS intersection targets. Further experiments revealed that LIG may inhibit cell migration induced by AngII by reducing calcium influx, and regulating phenotypic translation-related proteins SM-22α and OPN. The present study investigated the potential targets and signaling pathways of LIG, which provides new insight into its anti-atherosclerosis actions in terms of reducing inflammation, cell proliferation, and migration, and may constitute a novel target for the treatment of AS. PRACTICAL APPLICATIONS: LIG has been shown to have cardiovascular protective benefits, the mechanism by which it protects the cardiovascular and cerebrovascular systems in AS remains unknown. This study uses a holistic network pharmacology strategy to investigate putative treatment pathways and conducts exploratory experimentation. The findings demonstrate that LIG reduces VSMC migration in the treatment of AS, acts as an anti-inflammatory agent, and prevents excessive cell proliferation and migration. Finally, the goal of our research is to uncover the molecular mechanism of LIG's influence on AS. The findings will provide a new research avenue for LIG as well as suggestions for the study of other herbal treatments. These research results will provide a new research direction for LIG and provide guidance for the research of other herbal medicines. This work revealed the multi-component, multi-target, multi-pathway, and multi-disease mechanism of LIG.

A thrombin-triggered self-regulating anticoagulant strategy combined with anti-inflammatory capacity for blood-contacting implants

Interrelated coagulation and inflammation are impediments to endothelialization, a prerequisite for the long-term function of cardiovascular materials. Here, we proposed a self-regulating anticoagulant coating strategy combined with anti-inflammatory capacity, which consisted of thrombin-responsive nanogels with anticoagulant and anti-inflammatory components. As an anticoagulant, rivaroxaban was encapsulated in nanogels cross-linked by thrombin-cleavable peptide and released upon the trigger of environmental thrombin, blocking the further coagulation cascade. The superoxide dismutase mimetic Tempol imparted the antioxidant property. Polyphenol epigallocatechin gallate (EGCG), in addition to its anti-inflammatory function in synergy with Tempol, also acted as a weak cross-linker to stabilize the coating. The effectiveness and versatility of this coating were validated using two typical cardiovascular devices as models, biological valves and vascular stents. It was demonstrated that the coating worked as a precise strategy to resist coagulation and inflammation, escorted reendothelialization on the cardiovascular devices, and provided a new perspective for designing endothelium-like functional coatings.

Vascular smooth muscle cells in atherosclerosis: time for a re-assessment

Vascular smooth muscle cells (VSMCs) are key participants in both early and late-stage atherosclerosis. VSMCs invade the early atherosclerotic lesion from the media, expanding lesions, but also forming a protective fibrous cap rich in extracellular matrix to cover the 'necrotic' core. Hence, VSMCs have been viewed as plaque-stabilizing, and decreased VSMC plaque content-often measured by expression of contractile markers-associated with increased plaque vulnerability. However, the emergence of lineage-tracing and transcriptomic studies has demonstrated that VSMCs comprise a much larger proportion of atherosclerotic plaques than originally thought, demonstrate multiple different phenotypes in vivo, and have roles that might be detrimental. VSMCs down-regulate contractile markers during atherosclerosis whilst adopting alternative phenotypes, including macrophage-like, foam cell-like, osteochondrogenic-like, myofibroblast-like, and mesenchymal stem cell-like. VSMC phenotypic switching can be studied in tissue culture, but also now in the media, fibrous cap and deep-core region, and markedly affects plaque formation and markers of stability. In this review, we describe the different VSMC plaque phenotypes and their presumed cellular and paracrine functions, the regulatory mechanisms that control VSMC plasticity, and their impact on atherogenesis and plaque stability.

Salt-Inducible Kinase 3 Promotes Vascular Smooth Muscle Cell Proliferation and Arterial Restenosis by Regulating AKT and PKA-CREB Signaling

Objective

Arterial restenosis is the pathological narrowing of arteries after endovascular procedures, and it is an adverse event that causes patients to experience recurrent occlusive symptoms. Following angioplasty, vascular smooth muscle cells (SMCs) change their phenotype, migrate, and proliferate, resulting in neointima formation, a hallmark of arterial restenosis. SIKs (salt-inducible kinases) are a subfamily of the AMP-activated protein kinase family that play a critical role in metabolic diseases including hepatic lipogenesis and glucose metabolism. Their role in vascular pathological remodeling, however, has not been explored. In this study, we aimed to understand the role and regulation of SIK3 in vascular SMC migration, proliferation, and neointima formation.

Approach and Results

We observed that SIK3 expression was low in contractile aortic SMCs but high in proliferating SMCs. It was also highly induced by growth medium in vitro and in neointimal lesions in vivo. Inactivation of SIKs significantly attenuated vascular SMC proliferation and up-regulated p21CIP1 and p27KIP1. SIK inhibition also suppressed SMC migration and modulated actin polymerization. Importantly, we found that inhibition of SIKs reduced neointima formation and vascular inflammation in a femoral artery wire injury model. In mechanistic studies, we demonstrated that inactivation of SIKs mainly suppressed SMC proliferation by down-regulating AKT (protein kinase B) and PKA (protein kinase A)-CREB (cAMP response element-binding protein) signaling. CRTC3 (CREB-regulated transcriptional coactivator 3) signaling likely contributed to SIK inactivation-mediated antiproliferative effects.

Conclusions

These findings suggest that SIK3 may play a critical role in regulating SMC proliferation, migration, and arterial restenosis. This study provides insights into SIK inhibition as a potential therapeutic strategy for treating restenosis in patients with peripheral arterial disease.

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.

Purine-rich element binding protein B attenuates the coactivator function of myocardin by a novel molecular mechanism of smooth muscle gene repression

Myocardin is a potent transcriptional coactivator protein, which functions as the master regulator of vascular smooth muscle cell differentiation. The cofactor activity of myocardin is mediated by its physical interaction with serum response factor, a ubiquitously expressed transactivator that binds to CArG boxes in genes encoding smooth muscle-restricted proteins. Purine-rich element binding protein B (Purβ) represses the transcription of the smooth muscle α-actin gene (Acta2) in fibroblasts and smooth muscle cells by interacting with single-stranded DNA sequences flanking two 5' CArG boxes in the Acta2 promoter. In this study, the ability of Purβ to modulate the cofactor activity of myocardin was investigated using a combination of cellular and biochemical approaches. Results of smooth muscle gene promoter-reporter assays indicated that Purβ specifically inhibits the coactivator function of myocardin in a manner requiring the presence of all three single-stranded DNA binding domains in the Purβ homodimer. DNA binding analyses demonstrated that Purβ interacts with CArG-containing DNA elements with a much lower affinity compared to other purine-rich target sequences present in the Acta2 promoter. Co-immunoprecipitation and DNA pull-down assays revealed that Purβ associates with myocardin and serum response factor when free or bound to duplex DNA containing one or more CArG boxes. Functional analysis of engineered Purβ point mutants identified several amino acid residues essential for suppression of myocardin activity. Collectively, these findings suggest an inhibitory mechanism involving direct protein-protein interaction between the homodimeric Purβ repressor and the myocardin-serum response factor-CArG complex.

G6PD activity contributes to the regulation of histone acetylation and gene expression in smooth muscle cells and to the pathogenesis of vascular diseases

We aimed to determine 1) the mechanism(s) that enables glucose-6-phosphate dehydrogenase (G6PD) to regulate serum response factor (SRF)- and myocardin (MYOCD)-driven smooth muscle cell (SMC)-restricted gene expression, a process that aids in the differentiation of SMCs, and 2) whether G6PD-mediated metabolic reprogramming contributes to the pathogenesis of vascular diseases in metabolic syndrome (MetS). Inhibition of G6PD activity increased (>30%) expression of SMC-restricted genes and concurrently decreased (40%) the growth of human and rat SMCs ex vivo. Expression of SMC-restricted genes decreased (>100-fold) across successive passages in primary cultures of SMCs isolated from mouse aorta. G6PD inhibition increased Myh11 (47%) while decreasing (>50%) Sca-1, a stem cell marker, in cells passaged seven times. Similarly, CRISPR-Cas9-mediated expression of the loss-of-function Mediterranean variant of G6PD (S188F; G6PDS188F) in rats promoted transcription of SMC-restricted genes. G6PD knockdown or inhibition decreased (48.5%) histone deacetylase (HDAC) activity, enriched (by 3-fold) H3K27ac on the Myocd promoter, and increased Myocd and Myh11 expression. Interestingly, G6PD activity was significantly higher in aortas from JCR rats with MetS than control Sprague-Dawley (SD) rats. Treating JCR rats with epiandrosterone (30 mg/kg/day), a G6PD inhibitor, increased expression of SMC-restricted genes, suppressed Serpine1 and Epha4, and reduced blood pressure. Moreover, feeding SD control (littermates) and G6PDS188F rats a high-fat diet for 4 mo increased Serpine1 and Epha4 expression and mean arterial pressure in SD but not G6PDS188F rats. Our findings demonstrate that G6PD downregulates transcription of SMC-restricted genes through HDAC-dependent deacetylation and potentially augments the severity of vascular diseases associated with MetS.NEW & NOTEWORTHY This study gives detailed mechanistic insight about the regulation of smooth muscle cell (SMC) phenotype by metabolic reprogramming and glucose-6-phosphate dehydrogenase (G6PD) in diabetes and metabolic syndrome. We demonstrate that G6PD controls the chromatin modifications by regulating histone deacetylase (HDAC) activity, which deacetylates histone 3-lysine 9 and 27. Notably, inhibition of G6PD decreases HDAC activity and enriches H3K27ac on myocardin gene promoter to enhance the expression of SMC-restricted genes. Also, we demonstrate for the first time that G6PD inhibitor treatment accentuates metabolic and transcriptomic reprogramming to reduce neointimal formation in coronary artery and large artery elastance in metabolic syndrome rats.

YY1 directly interacts with myocardin to repress the triad myocardin/SRF/CArG box-mediated smooth muscle gene transcription during smooth muscle phenotypic modulation

Yin Yang 1 (YY1) regulates gene transcription in a variety of biological processes. In this study, we aim to determine the role of YY1 in vascular smooth muscle cell (VSMC) phenotypic modulation both in vivo and in vitro. Here we show that vascular injury in rodent carotid arteries induces YY1 expression along with reduced expression of smooth muscle differentiation markers in the carotids. Consistent with this finding, YY1 expression is induced in differentiated VSMCs in response to serum stimulation. To determine the underlying molecular mechanisms, we found that YY1 suppresses the transcription of CArG box-dependent SMC-specific genes including SM22α, SMα-actin and SMMHC. Interestingly, YY1 suppresses the transcriptional activity of the SM22α promoter by hindering the binding of serum response factor (SRF) to the proximal CArG box. YY1 also suppresses the transcription and the transactivation of myocardin (MYOCD), a master regulator for SMC-specific gene transcription by binding to SRF to form the MYOCD/SRF/CArG box triad (known as the ternary complex). Mechanistically, YY1 directly interacts with MYOCD to competitively displace MYOCD from SRF. This is the first evidence showing that YY1 inhibits SMC differentiation by directly targeting MYOCD. These findings provide new mechanistic insights into the regulatory mechanisms that govern SMC phenotypic modulation in the pathogenesis of vascular diseases.

Curcumin inhibits proliferation, migration and neointimal formation of vascular smooth muscle via activating miR-22

Context: Curcumin has antitumor, antioxidative, anti-inflammatory, and anti-proliferative properties.Objective: To investigate the role of miR-22 during curcumin-induced changes in vascular smooth muscle cells (VSMC) and neointima formation in balloon-injured rat abdominal aorta.Materials and methods: Sprague-Dawley rats were randomised to the sham-operated (n = 10), operated control (injured, n = 10), and curcumin treatment (n = 10) groups. miR-22 expression was determined by real-time PCR. SP1 was assessed by western blot and real-time PCR. Rat aortic smooth muscle A7r5 cells were used to determine VSMC proliferation and migration, which were measured by the MTS, EdU staining, Transwell, and wound healing assays.Results: miR-22 levels declined following arterial balloon injury in vivo (48% at 3d, p < 0.05) and serum stimulation in vitro (45% at 24 h, p < 0.01). Functional studies revealed that miR-22 negatively regulated the proliferation and migration of VSMCs by directly targeting the SP1 transcription factor in VSMCs. Curcumin increased the expression of miR-22 (81%, p < 0.05) and decreased the protein expression of SP1 in VSMCs (25%, p < 0.05). miR-22 inhibition was found to attenuate the effects of curcumin on VSMC functions. Curcumin increased miR-22 (46%, p < 0.01), decreased the SP1 protein (19%, p < 0.05), and inhibited vascular neointimal area (48%, p < 0.01) in vivo.Discussion: The miR-22/SP1 pathway is involved in the protective role of curcumin during arterial balloon injury, but the mechanisms remain unclear.Conclusion: miR-22 is involved in the inhibitory effects of curcumin on VSMCs' proliferation, migration and neointima hyperplasia after arterial balloon injury in rats. Curcumin could be used to prevent neointimal hyperplasia after angioplasty.

Mutual regulation between β-TRCP mediated REST protein degradation and Kv1.3 expression controls vascular smooth muscle cell phenotype switch

BACKGROUND AND AIMS

Phenotypic switch of vascular smooth muscle cells (VSMC) plays a key role in the pathogenesis of atherosclerosis and restenosis after artery intervention. Transcription repressor element 1-silencing transcription factor (REST) has been identified as key regulator of VSMC proliferation. In the present study, we sought to investigate the potential association of E3-ubiquitin ligase β-TRCP mediated REST protein degradation with Kv1.3 expression during VSMC phenotypic switch.

METHODS

Protein and mRNA expression was measured in ex vivo and in vitro models. Protein interaction and ubiquitination were analyzed by immunoprecipitation assays. ChIP assays were performed to assess the relationship between REST and targeted DNA binding site.

RESULTS

We found that the expression level of E3-ubiquitin ligase β-TRCP is significantly increased during VSMC phenotypic switch. REST protein ubiquitination mediated by β-TRCP is critical for VSMC proliferation and migration. We also found that the gene KCNA3 encoding potassium channel protein Kv1.3 contains a functional REST binding site and is repressed by REST. Downregulation of REST by β-TRCP and consequently upregulation of Kv1.3 are important events during VSMC phenotypic switch. Furthermore, upregulated Kv1.3 accelerates β-TRCP modulated REST degradation through Erk1/2 signaling.

CONCLUSIONS

Our results reveal a fundamental role for regulatory interactions between β-TRCP modulated REST degradation and Kv1.3 in the control of the multilayered regulatory programs required for VSMC phenotype switch.

TRPC and TRPV Channels' Role in Vascular Remodeling and Disease

Transient receptor potentials (TRPs) are non-selective cation channels that are widely expressed in vascular beds. They contribute to the Ca²⁺ influx evoked by a wide spectrum of chemical and physical stimuli, both in endothelial and vascular smooth muscle cells. Within the superfamily of TRP channels, different isoforms of TRPC (canonical) and TRPV (vanilloid) have emerged as important regulators of vascular tone and blood flow pressure. Additionally, several lines of evidence derived from animal models, and even from human subjects, highlighted the role of TRPC and TRPV in vascular remodeling and disease. Dysregulation in the function and/or expression of TRPC and TRPV isoforms likely regulates vascular smooth muscle cells switching from a contractile to a synthetic phenotype. This process contributes to the development and progression of vascular disorders, such as systemic and pulmonary arterial hypertension, atherosclerosis and restenosis. In this review, we provide an overview of the current knowledge on the implication of TRPC and TRPV in the physiological and pathological processes of some frequent vascular diseases.

l-Theanine attenuates neointimal hyperplasia via suppression of vascular smooth muscle cell phenotypic modulation

Neointimal hyperplasia is a prominent pathological phenomenon in the process of stent restenosis. Abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) play major pathological processes involved in the development of restenosis. l-Theanine, one of the major amino acid components in green tea, has been reported to improve vascular function. Here we display the effects of l-theanine on neointima formation and the underlying mechanism. In the rat carotid-artery balloon-injury model, l-theanine greatly inhibited neointima formation and prevented VSMCs from a contractile phenotype switching to a synthetic phenotype. In vitro study showed that l-theanine significantly inhibited PDGF-BB-induced VSMC proliferation and migration, which was comparable with the effect of l-theanine on AngII-induced VSMC proliferation and migration. Western blot analysis demonstrated that l-theanine suppressed PDGF-BB and AngII-induced reduction of SMA and SM22α and increment of OPN, suggesting that l-theanine inhibited the transformation of VSMCs from contractile to the synthetic phenotype. Further experiments showed that l-theanine exhibits potential preventive effects on neointimal hyperplasia and related vascular remodeling via inhibition of phosphorylation of Elk-1 and activation of MAPK1. The present study provides the new experimental evidence that l-theanine has potential clinical application as an anti-restenosis agent for the prevention of restenosis.

Homeobox A4 suppresses vascular remodeling by repressing YAP/TEAD transcriptional activity

The Hippo signaling pathway is involved in the pathophysiology of various cardiovascular diseases. Yes-associated protein (YAP) and transcriptional enhancer activator domain (TEAD) transcriptional factors, the main transcriptional complex of the Hippo pathway, were recently identified as modulators of phenotypic switching of vascular smooth muscle cells (VSMCs). However, the intrinsic regulator of YAP/TEAD-mediated gene expressions involved in vascular pathophysiology remains to be elucidated. Here, we identified Homeobox A4 (HOXA4) as a potent repressor of YAP/TEAD transcriptional activity using lentiviral shRNA screen. Mechanistically, HOXA4 interacts with TEADs and attenuates YAP/TEAD-mediated transcription by competing with YAP for TEAD binding. We also clarified that the expression of HOXA4 is relatively abundant in the vasculature, especially in VSMCs. In vitro experiments in human VSMCs showed HOXA4 maintains the differentiation state of VSMCs via inhibition of YAP/TEAD-induced phenotypic switching. We generated Hoxa4-deficient mice and confirmed the downregulation of smooth muscle-specific contractile genes and the exacerbation of vascular remodeling after carotid artery ligation in vivo. Our results demonstrate that HOXA4 is a repressor of VSMC phenotypic switching by inhibiting YAP/TEAD-mediated transcription.

TiO2-Based Nanotopographical Cues Attenuate the Restenotic Phenotype in Primary Human Vascular Endothelial and Smooth Muscle Cells

Coronary and peripheral stents are implants that are inserted into blocked arteries to restore blood flow. After stent deployment, the denudation of the endothelial cell (EC) layer and the resulting inflammatory cascade can lead to restenosis, the renarrowing of the vessel wall due to the hyperproliferation and excessive matrix secretion of smooth muscle cells (SMCs). Despite advances in drug-eluting stents (DES), restenosis remains a clinical challenge and can require repeat revascularizations. In this study, we investigated how vascular cell phenotype can be modulated by nanotopographical cues on the stent surface, with the goal of developing an alternative strategy to DES for decreasing restenosis. We fabricated TiO2 nanotubes and demonstrated that this topography can decrease SMC surface coverage without affecting endothelialization. In addition, to our knowledge, this is the first study reporting that TiO2 nanotube topography dampens the response to inflammatory cytokine stimulation in both endothelial and smooth muscle cells. We observed that compared to flat titanium surfaces, nanotube surfaces attenuated tumor necrosis factor alpha (TNFα)-induced vascular cell adhesion molecule-1 (VCAM-1) expression in ECs by 1.8-fold and decreased TNFα-induced SMC growth by 42%. Further, we found that the resulting cellular phenotype is sensitive to changes in nanotube diameter and that 90 nm diameter nanotubes leads to the greatest magnitude in cell response compared to 30 or 50 nm nanotubes.

Antagonistic relationship between the unfolded protein response and myocardin-driven transcription in smooth muscle

Smooth muscle cells (SMCs) are characterized by a high degree of phenotypic plasticity. Contractile differentiation is governed by myocardin-related transcription factors (MRTFs), in particular myocardin (MYOCD), and when their drive is lost, the cells become proliferative and synthetic with an expanded endoplasmic reticulum (ER). ER is responsible for assembly and folding of secreted proteins. When the load on the ER surpasses its capacity, three stress sensors (activating transcription factor 6 [ATF6], inositol-requiring enzyme 1α [IRE1α]/X-box binding protein 1 [XBP1], and PERK/ATF4) are activated to expand the ER and increase its folding capacity. This is referred to as the unfolded protein response (UPR). Here, we hypothesized that there is a reciprocal relationship between SMC differentiation and the UPR. Tight negative correlations between SMC markers (MYH11, MYOCD, KCNMB1, SYNPO2) and UPR markers (SDF2L1, CALR, MANF, PDIA4) were seen in microarray data sets from carotid arterial injury, partial bladder outlet obstruction, and bladder denervation, respectively. The UPR activators dithiothreitol (DTT) and tunicamycin (TN) activated the UPR and reduced MYOCD along with SMC markers in vitro. The IRE1α inhibitor 4μ8C counteracted the effect of DTT and TN on SMC markers and MYOCD expression. Transfection of active XBP1s was sufficient to reduce both MYOCD and the SMC markers. MRTFs also antagonized the UPR as indicated by reduced TN and DTT-mediated induction of CRELD2, MANF, PDIA4, and SDF2L1 following overexpression of MRTFs. The latter effect did not involve the newly identified MYOCD/SRF target MSRB3, or reduced production of either XBP1s or cleaved ATF6. The UPR thus counteracts SMC differentiation via the IRE1α/XBP1 arm of the UPR and MYOCD repression.

Novel Paracrine Functions of Smooth Muscle Cells in Supporting Endothelial Regeneration Following Arterial Injury

RATIONALE

Regeneration of denuded or injured endothelium is an important component of vascular injury response. Cell-cell communication between endothelial cells and smooth muscle cells (SMCs) plays a critical role not only in vascular homeostasis but also in disease. We have previously demonstrated that PKCδ (protein kinase C-delta) regulates multiple components of vascular injury response including apoptosis of SMCs and production of chemokines, thus is an attractive candidate for a role in SMC-endothelial cells communication.

OBJECTIVE

To test whether PKCδ-mediated paracrine functions of SMCs influence reendothelialization in rodent models of arterial injury.

METHODS AND RESULTS

Femoral artery wire injury was performed in SMC-conditional Prkcd knockout mice, and carotid angioplasty was conducted in rats receiving transient Prkcd knockdown or overexpression. SMC-specific knockout of Prkcd impaired reendothelialization, reflected by a smaller Evans blue-excluding area in the knockout compared with the wild-type controls. A similar impediment to reendothelialization was observed in rats with SMC-specific knockdown of Prkcd. In contrast, SMC-specific gene transfer of Prkcd accelerated reendothelialization. In vitro, medium conditioned by AdPKCδ-infected SMCs increased endothelial wound closure without affecting their proliferation. A polymerase chain reaction-based array analysis identified Cxcl1 and Cxcl7 among others as PKCδ-mediated chemokines produced by SMCs. Mechanistically, we postulated that PKCδ regulates Cxcl7 expression through STAT3 (signal transducer and activator of transcription 3) as knockdown of STAT3 abolished Cxcl7 expression. The role of CXCL7 in SMC-endothelial cells communication was demonstrated by blocking CXCL7 or its receptor CXCR2, both significantly inhibited endothelial wound closure. Furthermore, insertion of a Cxcl7 cDNA in the lentiviral vector that carries a Prkcd shRNA overcame the adverse effects of Prkcd knockdown on reendothelialization.

CONCLUSIONS

SMCs promote reendothelialization in a PKCδ-dependent paracrine mechanism, likely through CXCL7-mediated recruitment of endothelial cells from uninjured endothelium.

Mitochondrial Protein Poldip2 (Polymerase Delta Interacting Protein 2) Controls Vascular Smooth Muscle Differentiated Phenotype by O-Linked GlcNAc (N-Acetylglucosamine) Transferase-Dependent Inhibition of a Ubiquitin Proteasome System

RATIONALE

The mitochondrial Poldip2 (protein polymerase interacting protein 2) is required for the activity of the tricarboxylic acid cycle. As a consequence, Poldip2 deficiency induces metabolic reprograming with repressed mitochondrial respiration and increased glycolytic activity. Though homozygous deletion of Poldip2 is lethal, heterozygous mice are viable and show protection against aneurysm and injury-induced neointimal hyperplasia, diseases linked to loss of vascular smooth muscle differentiation. Thus, we hypothesize that the metabolic reprograming induced by Poldip2 deficiency controls VSMC differentiation.

OBJECTIVE

To determine the role of Poldip2-mediated metabolic reprograming in phenotypic modulation of VSMC.

METHODS AND RESULTS

We show that Poldip2 deficiency in vascular smooth muscle in vitro and in vivo induces the expression of the SRF (serum response factor), myocardin, and MRTFA (myocardin-related transcription factor A) and dramatically represses KLF4 (Krüppel-like factor 4). Consequently, Poldip2-deficient VSMC and mouse aorta express high levels of contractile proteins and, more significantly, these cells do not dedifferentiate nor acquire macrophage-like characteristics when exposed to cholesterol or PDGF (platelet-derived growth factor). Regarding the mechanism, we found that Poldip2 deficiency upregulates the hexosamine biosynthetic pathway and OGT (O-linked N-acetylglucosamine transferase)-mediated protein O-GlcNAcylation. Increased protein glycosylation causes the inhibition of a nuclear ubiquitin proteasome system responsible for SRF stabilization and KLF4 repression and is required for the establishment of the differentiated phenotype in Poldip2-deficient cells.

CONCLUSIONS

Our data show that Poldip2 deficiency induces a highly differentiated phenotype in VSMCs through a mechanism that involves regulation of metabolism and proteostasis. Additionally, our study positions mitochondria-initiated signaling as key element of the VSMC differentiation programs that can be targeted to modulate VSMC phenotype during vascular diseases.

Defective Base Excision Repair of Oxidative DNA Damage in Vascular Smooth Muscle Cells Promotes Atherosclerosis

Supplemental Digital Content is available in the text.

Background:

Atherosclerotic plaques demonstrate extensive accumulation of oxidative DNA damage, predominantly as 8-oxoguanine (8oxoG) lesions. 8oxoG is repaired by base excision repair enzymes; however, the mechanisms regulating 8oxoG accumulation in vascular smooth muscle cells (VSMCs) and its effects on their function and in atherosclerosis are unknown.

Methods:

We studied levels of 8oxoG and its regulatory enzymes in human atherosclerosis, the mechanisms regulating 8oxoG repair and the base excision repair enzyme 8oxoG DNA glycosylase I (OGG1) in VSMCs in vitro, and the effects of reducing 8oxoG in VSMCs in atherosclerosis in ApoE^−/− mice.

Results:

Human plaque VSMCs showed defective nuclear 8oxoG repair, associated with reduced acetylation of OGG1. OGG1 was a key regulatory enzyme of 8oxoG repair in VSMCs, and its acetylation was crucial to its repair function through regulation of protein stability and expression. p300 and sirtuin 1 were identified as the OGG1 acetyltransferase and deacetylase regulators, respectively, and both proteins interacted with OGG1 and regulated OGG1 acetylation at endogenous levels. However, p300 levels were decreased in human plaque VSMCs and in response to oxidative stress, suggesting that reactive oxygen species–induced regulation of OGG1 acetylation could be caused by reactive oxygen species–induced decrease in p300 expression. We generated mice that express VSMC-restricted OGG1 or an acetylation defective version (SM22α-OGG1 and SM22α-OGG1^K-R mice) and crossed them with ApoE^−/− mice. We also studied ApoE^−/− mice deficient in OGG1 (OGG1^−/−). OGG1^−/− mice showed increased 8oxoG in vivo and increased atherosclerosis, whereas mice expressing VSMC-specific OGG1 but not the acetylation mutant OGG1^K-R showed markedly reduced intracellular 8oxoG and reduced atherosclerosis. VSMC OGG1 reduced telomere 8oxoG accumulation, DNA strand breaks, cell death and senescence after oxidant stress, and activation of proinflammatory pathways.

Conclusions:

We identify defective 8oxoG base excision repair in human atherosclerotic plaque VSMCs, OGG1 as a major 8oxoG repair enzyme in VSMCs, and p300/sirtuin 1 as major regulators of OGG1 through acetylation/deacetylation. Reducing oxidative damage by rescuing OGG1 activity reduces plaque development, indicating the detrimental effects of 8oxoG on VSMC function.

Smooth Muscle Cell Phenotypic Diversity

Vascular smooth muscle cells (SMC) play a critical role in controlling blood pressure and blood distribution, as well as maintaining the structural integrity of the blood vessel. SMC also participate in physiological and pathological vascular remodeling due to their remarkable ability to dynamically modulate their phenotype. During the past decade, the development of in vivo fate mapping systems for unbiased identification and tracking of SMC and their progeny has led to major discoveries as well as the reevaluation of well-established concepts about the contribution of vascular SMC in major vascular diseases including atherosclerosis. Lineage tracing studies revealed that SMC undergoes multiple phenotypic transitions characterized by the expression of markers of alternative cell types (eg, macrophage-like and mesenchymal-stem cell-like) and populate injured or diseased vessels by oligoclonal expansion of a limited number of medial SMC. With the development of high-throughput transcriptomics and single-cell RNA sequencing (scRNAseq), the field is moving forward towards in-depth SMC phenotypic characterization. Herein, we review the major observations put forth by lineage and clonality tracing studies and the evidence in support for SMC phenotypic diversity in healthy and diseased vascular tissue. We will also discuss the opportunities and remaining challenges of combining lineage tracing and single-cell transcriptomics technologies, as well as studying the functional relevance of SMC phenotypic transitions and identifying the mechanisms controlling them.

c-Myb regulates transcriptional activation of miR-143/145 in vascular smooth muscle cells

BACKGROUND

MicroRNAs (miR) are small non-coding RNAs that regulate diverse biological functions. The bicistronic gene miR-143/145 determines cell fate and phenotype of vascular smooth muscle cells (VSMC), in part, by destabilizing Elk-1 mRNA. The transcription factor c-Myb also regulates differentiation and proliferation of VSMC, and here we test whether these effects may be mediated by miR-143/145.

METHODS & RESULTS

Flow cytometry of cardiovascular-directed d3.75 embryoid bodies (EBs) isolated smooth muscle progenitors with specific cell surface markers. In c-myb knockout (c-myb -/-) EB, these progenitors manifest low levels of miR-143 (19%; p<0.05) and miR-145 (6%; p<0.01) expression as compared to wild-type (wt) EB. Primary VSMC isolated from transgenic mice with diminished expression (c-myblx/lx) or reduced activity (c-mybh/h) of c-Myb also manifest low levels of miR-143 (c-myblx/lx: 50%; c-mybh/h: 41%), and miR-145 (c-myblx/lx: 49%; c-mybh/h: 56%), as compared to wt (P<0.05). Sequence alignment identified four putative c-Myb binding sites (MBS1-4) in the proximal promoter (PP) of the miR-143/145 gene. PP-reporter constructs revealed that point mutations in MBS1 and MBS4 abrogated c-Myb-dependent transcription from the miR-143/145 PP (P<0.01). Chromatin immunoprecipitation (ChIP) revealed preferential c-Myb binding at MBS4 (p<0.001). By conjugating Elk-1 3'-untranslated region (UTR) to a reporter and co-transducing wt VSMC with this plus a miR-143-antagomir, and co-transducing c-myblx/lx VSMC with this plus a miR-143-mimic, we demonstrate that c-Myb's ability to repress Elk-1 is mediated by miR-143.

CONCLUSION

c-Myb regulates VSMC gene expression by transcriptional activation of miR-143/145.

Inhibition of Aortic Intimal Hyperplasia and Vascular Smooth Muscle Proliferation and Extracellular Matrix Protein Expressions by Astragalus-Angelica Combination

VSMC proliferation and ECM deposition always resulted in intimal hyperplasia. Astragalus–Angelica combination has a protective effect on the cardiovascular system. The inhibition effect of different Astragalus–Angelica combination on the hyperplastic intima after vascular balloon injury in rats was investigated in this study. Astragalus–Angelica combination can inhibit the intima hyperplasia after balloon injury, in which a 1:1 ratio shows excellent results. Astragalus–Angelica combination can enhance the expression of smooth muscle α-actin (SMа-actin) and inhibit the expression of proliferating cell nuclear antigen (PCNA), cyclin D1, cyclin E, collagen I (Col-I), fibronectin (FN), and matrix metallopeptidase-9 (MMP-9) in hyperplastic intima, suggesting that Astragalus–Angelica combination can inhibit the intimal hyperplasia of blood vessels in rats. The mechanism is related to the inhibition of PI3K/Akt signaling pathway activation and thereby inhibits the phenotypic transformation and cell proliferation of VSMCs and thus inhibits the extracellular matrix (ECM) deposition of vascular wall during intimal hyperplasia.

Deletion of ACTA2 in mice promotes angiotensin II induced pathogenesis of thoracic aortic aneurysms and dissections

Background

Mutation of the ACTA2 (α-2 smooth muscle actin) gene accounts for ~15% of all cases of familial thoracic aortic aneurysms and dissections. Surprisingly, no severe vascular phenotypes were observed at baseline in mice carrying this gene mutation. Our aim was to explore whether mutation of ACTA2 promotes the development of aneurysms or dissections in the presence of angiotensin II (AngII) and to determine whether this mutation has an impact on the phenotypic modulation and apoptosis mediated by AngII in vascular smooth muscle cells (VSMCs).

Methods

Mice were divided into three groups: AngII stimulated-wild-type (WT) (AngII) and ACTA2^-/- mice (ACTA2) group, in which AngII were administered subcutaneously into 8-week-old C57 mice and ACTA2^-/- mice, respectively, for 4 weeks using osmotic minipumps, and the control group (WT), in which the WT mice were infused with normal saline (NS). Ultrasound was performed to quantify lumen diameters. RT-qPCR and Western blot were used to assess gene expression, and histobiochemistry was used to evaluate the pathological changes in the thoracoabdominal aortas. TUNEL was used to assess apoptosis in VSMCs.

Results

Compared with the AngII- group, the ACTA2 mice exhibited more severity of dilated lumena of the aortas, a significantly increased expression of osteopontin (OPN), an elevated ratio of Bax/Bcl-2, increased apoptosis, and a decreased expression of α-smooth muscle actin (α-SMA).

Conclusions

Knockout of ACTA2 promoted AngII induced progressive lumen dilation of the aortas, apoptosis, and the phenotypic modulation in VSMCs in mice.

Novel Adipokine, FAM19A5, Inhibits Neointima Formation After Injury Through Sphingosine-1-Phosphate Receptor 2

Background:

Obesity plays crucial roles in the development of cardiovascular diseases. However, the mechanisms that link obesity and cardiovascular diseases remain elusive. Compelling evidence indicates that adipokines play an important role in obesity-related cardiovascular diseases. Here, we found a new adipokine-named family with sequence similarity 19, member A5 (FAM19A5), a protein with unknown function that was predicted to be distantly related to the CC-chemokine family. We aimed to test whether adipose-derived FAM19A5 regulates vascular pathology on injury.

Methods:

DNA cloning, protein expression, purification, and N-terminal sequencing were applied to characterize FAM19A5. Adenovirus infection and siRNA transfection were performed to regulate FAM19A5 expression. Balloon and wire injury were performed in vivo on the rat carotid arteries and mouse femoral arteries, respectively. Bioinformatics analysis, radioactive ligand-receptor binding assays, receptor internalization, and calcium mobilization assays were used to identify the functional receptor for FAM19A5.

Results:

We first characterized FAM19A5 as a secreted protein, and the first 43 N-terminal amino acids were the signal peptides. Both FAM19A5 mRNA and protein were abundantly expressed in the adipose tissue but were downregulated in obese mice. Overexpression of FAM19A5 markedly inhibited vascular smooth muscle cell proliferation and migration and neointima formation in the carotid arteries of balloon-injured rats. Accordingly, FAM19A5 silencing in adipocytes significantly promoted vascular smooth muscle cell activation. Adipose-specific FAM19A5 transgenic mice showed greater attenuation of neointima formation compared with wild-type littermates fed with or without Western-style diet. We further revealed that sphingosine-1-phosphate receptor 2 was the functional receptor for FAM19A5, with a dissociation constant ( K d ) of 0.634 nmol/L. Inhibition of sphingosine-1-phosphate receptor 2 or its downstream G12/13-RhoA signaling circumvented the suppressive effects of FAM19A5 on vascular smooth muscle cell proliferation and migration.

Conclusions:

We revealed that a novel adipokine, FAM19A5, was capable of inhibiting postinjury neointima formation via sphingosine-1-phosphate receptor 2-G12/13-RhoA signaling. Downregulation of FAM19A5 during obesity may trigger cardiometabolic diseases.

MicroRNA-132 targeting PTEN contributes to cilostazol-promoted vascular smooth muscle cell differentiation

BACKGROUND AND AIMS

Cilostazol, beyond its antiplatelet effect, is also capable of promoting vascular smooth muscle cell (VSMC) differentiation. The aim of this study was to explore the potential role of PTEN, known to associate with VSMC differentiation, and its related microRNA (miRNA) in cilostazol-dependent effects.

METHODS AND RESULTS

Microarray analysis in balloon-injured rat carotid arteries comparing with and without balloon injury revealed that miR-132 was differentially expressed. Bioinformatic analysis predicts PTEN as a novel target of miR-132. Western blot and quantitative real-time reverse transcription-polymerase chain reaction along with in situ hybridization documented that cilostazol treatment enhanced PTEN and reduced miR-132 expression in the neointima of balloon-injured arteries. Treatment of cultured rat VSMCs with cilostazol resulted in the up-regulation of PTEN mRNA and the down-regulation of miR-132, supporting an in vitro relevance. Co-transfection experiments showed that transfection of miR-132 mimic into VSMCs suppressed PTEN 3'UTR activities, further reflecting that PTEN is the direct target of miR-132. Over-expression of miR-132 in VSMCs led to an attenuation of cilostazol-induced PTEN and its downstream VSMC differentiation marker (calponin) expression, confirming the critical role of miR-132 in VSMC differentiation. Transient transfection studies demonstrated that cilostazol reduced the activity of miR-132 promoter, which was mediated via cyclic AMP response element-binding protein. Notably, the use of lentivirus to over-express miR-132 in the neointima of balloon-injured arteries could reverse the effect of cilostazol in vivo.

CONCLUSIONS

These results suggest that miR-132 by targeting PTEN may be an important regulator in mediating cilostazol actions on VSMC differentiation.

Redistribution of Mature Smooth Muscle Markers in Brain Arteries in Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

Vascular smooth muscle cells (SMCs) undergo a series of dramatic changes in CADASIL, the most common inherited cause of vascular dementia and stroke. NOTCH3 protein accumulates and aggregates early in CADASIL, followed by loss of mature SMCs from the media of brain arteries and marked intimal proliferation. Similar intimal thickening is seen in peripheral arterial disease, which features pathological intimal cells including proliferative, dedifferentiated, smooth muscle-like cells deficient in SMC markers. Limited studies have been performed to investigate the differentiation state and location of SMCs in brain vascular disorders. Thus, we investigated the distribution of cells expressing SMC markers in a group of genetically characterized, North American CADASIL brains. We quantified brain RNA abundance of these markers in nine genetically verified cases of CADASIL and found that mRNA expression for several mature SMC markers was increased in CADASIL brain compared to age-matched control. Immunohistochemical studies and in situ hybridization localization of mRNA demonstrated loss of SMCs from the arterial media, and SMC marker-expressing cells were instead redistributed into the intima of diseased arteries and around balloon cells of the degenerating media. We conclude that, despite loss of medial smooth muscle cells in diseased arteries, smooth muscle markers are not lost from CADASIL brain, but rather, the localization of cells expressing mature SMC markers changes dramatically.

Understanding the role of non-coding RNA (ncRNA) in stent restenosis

Coronary heart disease (CHD) is one of the leading disorders with the highest mortality rate. Percutaneous angioplasty and stent implantation are the currently available standard methods for the treatment of obstructive coronary artery disease. However, the stent being an exogenous substance causes several complications by promoting the proliferation of vascular smooth muscle cells, immune responses and neointima formation after implantation, leading to post-stent restenosis (ISR) and late thrombosis. The prevention of these adverse vascular events is important to achieve long-term proper functioning of the heart after stent implantation. Non-coding ribonucleic acids (ncRNAs) are RNA molecules not translated into proteins, theyhave a great potential in regulating endothelial cell and vascular smooth muscle function as well as inflammatory reactions. In this review, we outline the regulatory functions of different classes of ncRNA in cardiovascular disease and propose ncRNAs as new targets for stent restonosis treatment.

[Efficacy of dermal scaffold for promoting repair of acute full-thickness skin defects in pigs]

OBJECTIVE

To investigate the efficacy of Lando^® dermal scaffold for promoting repair of acute full-thickness skin defects in pigs and explore the possible mechanism.

METHODS

Three 5 cm×5 cm full-thickness skin defects were created on the left dorsal skin (control group) and another 3 on the right dorsal skin (treatment group) of each of 6 Tibetan pigs. The wounds in the treatment group were covered with a bilayer artificial skin (Lando) and the control wounds with vaseline gauze. In both groups, autogenous split-thickness skin were grafted to the wounds 2 weeks later (with the silicone rubber membrane removed before grafting in the treatment group). At 3 days and 2 and 10 weeks after the injury, the wounds were assessed for general condition and contraction, and tissue samples were collected from the wounds to examine the expressions of α-smooth muscle actin (α-SMA) and transforming growth factor-β1 (TGF-β1) using immunohistochemistry and the expressions of MMP-1 and TIMP-1 mRNA using RT-PCR.

RESULTS

At 3 days after the injury, the wounds in the 2 groups showed no significant differences in the results of any examinations. At 2 weeks after the injury, the wounds in the treatment group showed rich and more smooth granulation tissues with more regular wound edges compared with the control wounds. At 2 and 10 weeks after the injury, the wound contraction rates in the treatment group were (30.5∓3.4)% and (39.2∓2.8)%, respectively, significantly lower than the rates of (51.8∓2.6)% (t=-29.840, P=0.000) and (60.7∓2.2)% (t=-50.213, P=0.000) in the control group. At 2 weeks, the wound tissues in the treatment group expressed significantly higher levels of α-SMA (t=15.921, P=0.000) and TGF-β1 (t=29.995, P=0.000) than the control wounds, but at 10 weeks, the expressions of α-SMA (t=-41.823, P=0.000) and TGF-β1 (t=-99.777, P=0.000) in the treatment group were significantly lower than those in the control group. Compared with those in the control group, the expression of MMP-1 mRNA in the treatment group was significantly lower at 2 weeks (t=-45.412, P=0.000) but significantly higher at 10 weeks (t=78.769, P=0.000), and the expression of TIMP-1 mRNA in the treatment group was significantly lower both at 2 weeks (t=-27.064, P=0.000) and at 10 weeks (t=-40.535, P=0.000).

CONCLUSIONS

Lando^® dermal scaffold can promote granulation tissue growth possibly in relation with increased TGF-β1 and decreased MMP-1 expression in the wounds. This scaffold material also reduces wound contraction and lessens scar hyperplasia and contracture after wound healing, probably as a result of decreased α-SMA, TGF-β1, and TIMP-1 and increased MMP-1 expressions.

Activation and Migration of Adventitial Fibroblasts Contributes to Vascular Remodeling

The rat carotid artery balloon injury model was used to prove the activation and migration of adventitial fibroblasts. We found that at day 7 after injury, adventitial fibroblasts proliferated, transformed into myofibroblasts under transmission electron microscopy in the model group. Simultaneously, we proved that the adventitial cells migrated to the media and intima on seventh day after injury by directly labeled the adventitial cells by the in vivo gene transfer technique. Moreover, we captured the precise moment when the adventitial fibroblasts migrated from the adventitia to the media through the external elastic plate under transmission electron microscope. This study provides direct evidences that adventitial fibroblasts activate and migrate to the media and intima, then actively take part in revascularization. Anat Rec, 301:1216-1223, 2018. © 2018 Wiley Periodicals, Inc.

Cigarette Smoke Initiates Oxidative Stress-Induced Cellular Phenotypic Modulation Leading to Cerebral Aneurysm Pathogenesis

OBJECTIVE

Cigarette smoke exposure (CSE) is a risk factor for cerebral aneurysm (CA) formation, but the molecular mechanisms are unclear. Although CSE is known to contribute to excess reactive oxygen species generation, the role of oxidative stress on vascular smooth muscle cell (VSMC) phenotypic modulation and pathogenesis of CAs is unknown. The goal of this study was to investigate whether CSE activates a NOX (NADPH oxidase)-dependent pathway leading to VSMC phenotypic modulation and CA formation and rupture.

APPROACH AND RESULTS

In cultured cerebral VSMCs, CSE increased expression of NOX1 and reactive oxygen species which preceded upregulation of proinflammatory/matrix remodeling genes (MCP-1, MMPs [matrix metalloproteinase], TNF-α, IL-1β, NF-κB, KLF4 [Kruppel-like factor 4]) and downregulation of contractile genes (SM-α-actin [smooth muscle α actin], SM-22α [smooth muscle 22α], SM-MHC [smooth muscle myosin heavy chain]) and myocardin. Inhibition of reactive oxygen species production and knockdown of NOX1 with siRNA or antisense decreased CSE-induced upregulation of NOX1 and inflammatory genes and downregulation of VSMC contractile genes and myocardin. p47phox^-/- NOX knockout mice, or pretreatment with the NOX inhibitor, apocynin, significantly decreased CA formation and rupture compared with controls. NOX1 protein and mRNA expression were similar in p47phox^-/- mice and those pretreated with apocynin but were elevated in unruptured and ruptured CAs. CSE increased CA formation and rupture, which was diminished with apocynin pretreatment. Similarly, NOX1 protein and mRNA and reactive oxygen species were elevated by CSE, and in unruptured and ruptured CAs.

CONCLUSIONS

CSE initiates oxidative stress-induced phenotypic modulation of VSMCs and CA formation and rupture. These molecular changes implicate oxidative stress in the pathogenesis of CAs and may provide a potential target for future therapeutic strategies.

FOXO3a (Forkhead Transcription Factor O Subfamily Member 3a) Links Vascular Smooth Muscle Cell Apoptosis, Matrix Breakdown, Atherosclerosis, and Vascular Remodeling Through a Novel Pathway Involving MMP13 (Matrix Metalloproteinase 13)

OBJECTIVE

Vascular smooth muscle cell (VSMC) apoptosis accelerates atherosclerosis and promotes breakdown of the extracellular matrix, but the mechanistic links between these 2 processes are unknown. The forkhead protein FOXO3a (forkhead transcription factor O subfamily member 3a) is activated in human atherosclerosis and induces a range of proapoptotic and other transcriptional targets. We, therefore, determined the mechanisms and consequences of FOXO3a activation in atherosclerosis and arterial remodeling after injury.

APPROACH AND RESULTS

Expression of a conditional FOXO3a allele (FOXO3aA3ER) potently induced VSMC apoptosis, expression and activation of MMP13 (matrix metalloproteinase 13), and downregulation of endogenous TIMPs (tissue inhibitors of MMPs). mmp13 and mmp2 were direct FOXO3a transcriptional targets in VSMCs. Activation of endogenous FOXO3a also induced MMP13, extracellular matrix degradation, and apoptosis, and MMP13-specific inhibitors and fibronectin reduced FOXO3a-mediated apoptosis. FOXO3a activation in mice with VSMC-restricted FOXO3aA3ER induced MMP13 expression and activity and medial VSMC apoptosis. FOXO3a activation in FOXO3aA3ER/ApoE^-/- (apolipoprotein E deficient) mice increased atherosclerosis, increased necrotic core and reduced fibrous cap areas, and induced features of medial degeneration. After carotid artery ligation, FOXO3a activation increased VSMC apoptosis, VSMC proliferation, and neointima formation, all of which were reduced by MMP13 inhibition.

CONCLUSIONS

FOXO3a activation induces VSMC apoptosis and extracellular matrix breakdown, in part, because of transcriptional activation of MMP13. FOXO3a activation promotes atherosclerosis and medial degeneration and increases neointima after injury that is partly dependent on MMP13. FOXO3a-induced MMP activation represents a direct mechanistic link between VSMC apoptosis and matrix breakdown in vascular disease.

Vascularization of Lando® dermal scaffold in an acute full-thickness skin-defect porcine model

The Lando^® dermal scaffold is a newly developed, tissue-engineered dermal scaffold material. This study sought to observe its vascularization in an acute full-thickness skin-defect porcine model. There were eight Tibetan pigs in this research. Six 5 × 5 cm full-thickness skin-defect wounds were prepared on the dorsal area of each pig, which were divided into two groups. The experimental group wounds were covered by Lando^® dermal scaffolds, while the other received Vaseline gauzes as blank control. At day 3, 7, 14 and 21 after injury, the general condition of wounds was observed, and wound specimens were obtained for HE staining, Masson staining and the expression of CD31, α-SMA and VEGF, which were examined by immunohistochemistry. The results showed the wounds in the experimental group (Lando) were drier with a lower incidence of infection, and the granulation tissues grew better and smoother than the control group. In the experimental group, the hyperemia, edema and inflammatory reactions were milder, the fibroblasts ingrew earlier, the capillaries grew mostly parallel to the wound surface which resembled normal skin, and the collagen fibers were thicker with more regular arrangement than in the control group. The CD31 + microvessel count, α-SMA + microvessel count and VEGF expression of the experimental group were significantly higher than the control group at day 7 and 14 after injury (p < .05). In conclusion, the Lando^® dermal scaffold showed good vascularization at day 14 post grafting in an acute full-thickness skin-defect porcine model, which may be associated with increased expression of VEGF.

Distinct Cellular Mechanisms Underlie Smooth Muscle Turnover in Vascular Development and Repair

Supplemental Digital Content is available in the text.

Rationale:

Vascular smooth muscle turnover has important implications for blood vessel repair and for the development of cardiovascular diseases, yet lack of specific transgenic animal models has prevented it’s in vivo analysis.

Objective:

The objective of this study was to characterize the dynamics and mechanisms of vascular smooth muscle turnover from the earliest stages of embryonic development to arterial repair in the adult.

Methods and Results:

We show that CD146 is transiently expressed in vascular smooth muscle development. By using CRISPR-Cas9 genome editing and in vitro smooth muscle differentiation assay, we demonstrate that CD146 regulates the balance between proliferation and differentiation. We developed a triple-transgenic mouse model to map the fate of NG2⁺CD146⁺ immature smooth muscle cells. A series of pulse-chase experiments revealed that the origin of aortic vascular smooth muscle cells can be traced back to progenitor cells that reside in the wall of the dorsal aorta of the embryo at E10.5. A distinct population of CD146⁺ smooth muscle progenitor cells emerges during embryonic development and is maintained postnatally at arterial branch sites. To characterize the contribution of different cell types to arterial repair, we used 2 injury models. In limited wire-induced injury response, existing smooth muscle cells are the primary contributors to neointima formation. In contrast, microanastomosis leads to early smooth muscle death and subsequent colonization of the vascular wall by proliferative adventitial cells that contribute to the repair.

Conclusions:

Extensive proliferation of immature smooth muscle cells in the primitive embryonic dorsal aorta establishes the long-lived lineages of smooth muscle cells that make up the wall of the adult aorta. A discrete population of smooth muscle cells forms in the embryo and is postnatally sustained at arterial branch sites. In response to arterial injuries, existing smooth muscle cells give rise to neointima, but on extensive damage, they are replaced by adventitial cells.

Microsomal Prostaglandin E Synthase-1 Expression by Aortic Smooth Muscle Cells Attenuates the Differentiated Phenotype

The development of numerous types of cardiovascular disease is associated with alteration of the vascular smooth muscle cell (SMC) phenotype. We have previously shown that abdominal aortic aneurysm progression in a mouse model of the disease is associated with reduced differentiation of SMCs within the lesion and that cyclooxygenase-2 (COX-2) is critical to initiation and progression of the aneurysms. The current studies used human aortic SMC (hASMC) cultures to better characterize mechanisms responsible for COX-2-dependent modulation of the SMC phenotype. Depending on the culture conditions, hASMCs expressed multiple characteristics of a differentiated and contractile phenotype, or a dedifferentiated and secretory phenotype. The pharmacological inhibition of COX-2 promoted the differentiated phenotype, whereas treatment with the COX-2-derived metabolite prostaglandin E2 (PGE2) increased characteristics of the dedifferentiated phenotype. Furthermore, pharmacological inhibition or siRNA-mediated knockdown of microsomal prostaglandin E synthase-1 (mPGES-1), the enzyme that functions downstream of COX-2 during the synthesis of PGE2, significantly increased expression of characteristics of the differentiated SMC phenotype. Therefore, our findings suggest that COX-2 and mPGES-1-dependent synthesis of PGE2 contributes to a dedifferentiated hASMC phenotype and that mPGES-1 may provide a novel pharmacological target for treatment of cardiovascular diseases where altered SMC differentiation has a causative role.

Cilostazol for Secondary Prevention of Stroke: Should the Guidelines Perhaps Be Extended?

Cilostazol belongs to the new generation antiplatelet agents that have been introduced and studied regarding a potential role in cardiovascular disease prevention or treatment. Although data on peripheral artery disease are sufficient, and the drug has been recommended as first line treatment for intermittent claudication, it has not been approved nor recommended as far as cerebrovascular events are concerned. However, a great volume of randomized as well as pooled data has been published during the last years. Therefore, this review aims to describe the basic mechanisms of cilostazol’s action as well as to present all recent clinical data in order to conclude on whether official guidelines should be extended.

Altered Expression of MicroRNA-15a and Kruppel-Like Factor 4 in Cerebrospinal Fluid and Plasma After Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

Cerebral vasospasm (CVS) is a major determinant of prognosis in patients with subarachnoid hemorrhage (SAH). Alteration in the vascular phenotype contributes to development of CVS. However, little is known about the role of microRNAs (miRNAs) in the phenotypic alteration after SAH. We investigated the expression profile of miRNAs and the chronologic changes in the expression of microRNA-15a (miR-15a) and Kruppel-like factor 4 (KLF4), a potent regulator of vascular phenotype modulation that modulates the expression of miR-15a, in the plasma and cerebrospinal fluid (CSF) of patients with SAH.

METHODS

Peripheral blood and CSF samples were collected from 8 patients with aneurysmal SAH treated with endovascular obliteration. Samples obtained from 3 patients without SAH were used as controls in the analysis. Exosomal miRNAs were isolated and subjected to microarray analysis with the three-dimensional-gene miRNA microarray kit. The time course of the expression of miR-15a and KLF4 was analyzed using quantitative real-time polymerase chain reaction.

RESULTS

Microarray analysis showed that 12 miRNAs including miR-15a were upregulated or downregulated both in the CSF and in plasma after SAH within 3 days. Quantitative real-time polymerase chain reaction showed that miR-15a expression was significantly increased in both the CSF and plasma, with a peak around 3-5 days after SAH, whereas the expression of KLF4 was significantly decreased around 1-3 days after SAH and remained lower than in controls.

CONCLUSIONS

Our results suggest that an early and persistent decrease in KLF4 followed by an increase in miR-15a may contribute to the altered vascular phenotype, resulting in development of CVS.

miR-125a-5p Modulates Phenotypic Switch of Vascular Smooth Muscle Cells by Targeting ETS-1

MicroRNAs are key regulators of vascular smooth muscle cells (VSMCs) phenotypic switch, one of the main events responsible for bare metal in-stent restenosis after percutaneous coronary intervention. miR-125a-5p is an important modulator of differentiation, proliferation, and migration in different cell types; however, its role in VSMCs is still unknown. The aim of this study was to evaluate the role of miR-125a-5p in VSMCs phenotypic switch. Our results suggest that miR-125a-5p is highly expressed in VSMCs, but it is down-regulated after vascular injury in vivo. Its overexpression is sufficient to reduce VSMCs proliferation and migration, and it is able to promote the expression of selective VSMCs markers such as alpha smooth muscle actin, myosin heavy chain 11, and smooth muscle 22 alpha. Interestingly, miR-125a-5p directly targets ETS-1, a transcription factor implicated in cell proliferation and migration and is crucial in PDGF-BB pathway in VSMCs. Thus, miR-125a-5p in this context inhibits PDGF-BB pathway and is therefore a potential regulator of VSMCs phenotypic switch.

Smart mechanosensing machineries enable migration of vascular smooth muscle cells in atherosclerosis-relevant 3D matrices

At the early stage of atherosclerosis, neointima is formed due to the migration of vascular smooth muscle cells (VSMCs) from the media to the intima. VSMCs are surrounded by highly adhesive 3D matrices. They take specific strategies to cross various 3D matrices in the media, including heterogeneous collagen and mechanically strong basement membrane. Migration of VSMCs is potentially caused by biomechanical mechanism. Most in vitro studies focus on cell migration on 2D substrates in response to biochemical factors. How the cells move through 3D matrices under the action of mechanosensing machineries remains unexplored. In this review, we propose that several interesting tension-dependent machineries act as "tractor"-posterior myosin II accumulation, and "wrecker"-anterior podosome maintaining, to power VSMCs ahead. VSMCs embedded in 3D matrices may accumulate a minor myosin II isoform, myosin IIB, at the cell rear. Anisotropic myosin IIB distribution creates cell rear, polarizes cell body, pushes the nucleus and reshapes the cell body, and cooperates with a uniformly distributed myosin IIA to propel the cell forward. On the other hand, matrix digestion by podosome further promote the migration when the matrix becomes denser. Actomyosin tension activates Src to induce podosome in soft 3D matrices and retain the podosome integrity to steadily digest the matrix.

Agonistic Anti-PDGF Receptor Autoantibodies from Patients with Systemic Sclerosis Impact Human Pulmonary Artery Smooth Muscle Cells Function In Vitro

One of the earliest events in the pathogenesis of systemic sclerosis (SSc) is microvasculature damage with intimal hyperplasia and accumulation of cells expressing PDGF receptor. Stimulatory autoantibodies targeting PDGF receptor have been detected in SSc patients and demonstrated to induce fibrosis in vivo and convert in vitro normal fibroblasts into SSc-like cells. Since there is no evidence of the role of anti-PDGF receptor autoantibodies in the pathogenesis of SSc vascular lesions, we investigated the biologic effect of agonistic anti-PDGF receptor autoantibodies from SSc patients on human pulmonary artery smooth muscle cells and the signaling pathways involved. The synthetic (proliferation, migration, and type I collagen gene α1 chain expression) and contractile (smooth muscle-myosin heavy chain and smooth muscle-calponin expression) profiles of human pulmonary artery smooth muscle cells were assessed in vitro after incubation with SSc anti-PDGF receptors stimulatory autoantibodies. The role of reactive oxygen species, NOX isoforms, and mammalian target of rapamycin (mTOR) was investigated. Human pulmonary artery smooth muscle cells acquired a synthetic phenotype characterized by higher growth rate, migratory activity, gene expression of type I collagen α1 chain, and less expression of markers characteristic of the contractile phenotype such as smooth muscle-myosin heavy chain and smooth muscle-calponin when stimulated with PDGF and autoantibodies against PDGF receptor, but not with normal IgG. This phenotypic profile is mediated by increased generation of reactive oxygen species and expression of NOX4 and mTORC1. Our data indicate that agonistic anti-PDGF receptor autoantibodies may contribute to the pathogenesis of SSc intimal hyperplasia.

Endosialin Promotes Atherosclerosis Through Phenotypic Remodeling of Vascular Smooth Muscle Cells

OBJECTIVE

Vascular smooth muscle cells (VSMC) play a key role in the pathogenesis of atherosclerosis, the globally leading cause of death. The transmembrane orphan receptor endosialin (CD248) has been characterized as an activation marker of cells of the mesenchymal lineage including tumor-associated pericytes, stromal myofibroblasts, and activated VSMC. We, therefore, hypothesized that VSMC-expressed endosialin may display functional involvement in the pathogenesis of atherosclerosis.

APPROACH AND RESULTS

Expression of endosialin was upregulated during atherosclerosis in apolipoprotein E (ApoE)-null mice and human atherosclerotic samples analyzed by quantitative real-time polymerase chain reaction and immunohistochemistry. Atherosclerosis, assessed by Oil Red O staining of the descending aorta, was significantly reduced in ApoE/endosialin-deficient mice on Western-type diet. Marker analysis of VSMC in lesions induced by shear stress-modifying cast implantation around the right carotid artery identified a more pronounced contractile VSMC phenotype in the absence of endosialin. Moreover, in addition to contributing to neointima formation, endosialin also potentially regulated the proinflammatory phenotype of VSMC as evidenced in surrogate cornea pocket assay experiments in vivo and corresponding flow cytometry and ELISA analyses in vitro.

CONCLUSIONS

The experiments identify endosialin as a potential regulator of phenotypic remodeling of VSMC contributing to atherosclerosis. The association of endosialin with atherosclerosis and its absent expression in nonatherosclerotic samples warrant further consideration of endosialin as a therapeutic target and biomarker.

Responses of adventitial CD34+ vascular wall-resident stem/progenitor cells and medial smooth muscle cells to carotid injury in rats

Cell culture and carotid injury studies with SD rats were performed to investigate the roles of CD34⁺ vascular wall-resident stem/progenitor cells (VRS/Pcs) and vascular smooth muscle cells (SMCs) in neointimal formation. In vitro, the media-isolated SM MHC⁺ SMCs occupied 93.92±8.62% of total BrdU⁺ cells, whereas the CD34⁺ cells, only 2.61±0.82%, indicating that the cell expansion in SMC culture was attributed to SM MHC⁺ SMCs. The adventitia-isolated CD34⁺ VRS/Pcs responded to PDGF-BB by differentiating into SMC-like cells which expressed SM22α (an early stage SMC marker), but seldom SM MHC (a late stage SMC marker). In carotid injury model, the CD34⁺ VRS/Pcs differentiated SMC-like cells migrated in very few numbers into only the outer layer of the media, and this was further confirmed by a cell tracking analysis. While the neointimal cells were consistently SM MHC⁺ and CD34^- SMCs during whole course of the post-injury remodeling. Thus it is speculated that the adventitial CD34⁺ VRS/Pcs, at least in rat model, do not directly participate in neointimal formation, but function to maintain homeostasis of the media during injury-induced vascular wall remodeling.

Caspase-1 Plays a Critical Role in Accelerating Chronic Kidney Disease-Promoted Neointimal Hyperplasia in the Carotid Artery

To determine whether caspase-1 is critical in chronic kidney disease (CKD)-mediated arterial neointimal hyperplasia (NH), we utilized caspase(-/-) mice and induced NH in carotid artery in a CKD environment, and uremic sera-stimulated human vascular smooth muscle cells (VSMC). We made the following findings: (1) Caspase-1 inhibition corrected uremic sera-mediated downregulation of VSMC contractile markers, (2) CKD-promoted NH was attenuated in caspase(-/-) mice, (3) CKD-mediated downregulation of contractile markers was rescued in caspase null mice, and (4) expression of VSMC migration molecule αvβ3 integrin was reduced in caspase(-/-) tissues. Our results suggested that caspase-1 pathway senses CKD metabolic danger signals. Further, CKD-mediated increase of contractile markers in VSMC and increased expression of VSMC migration molecule αvβ3 integrin in NH formation were caspase-1 dependent. Therefore, caspase-1 is a novel therapeutic target for the suppression of CKD-promoted NH.

Soluble epoxide hydrolase is involved in the development of atherosclerosis and arterial neointima formation by regulating smooth muscle cell migration

Epoxyeicosatrienoic acids (EETs) have beneficial effects on cardiovascular disease. Soluble epoxide hydrolase (sEH) metabolizes EETs to less active diols, thus diminishing their biological activity. sEH inhibitors can suppress the progression of atherosclerotic lesions in animal models. However, the regulation of sEH in vascular smooth muscle cells (VSMCs) and role of sEH in patients with atherosclerosis have not been evaluated. We hypothesize that sEH in VSMCs plays a pivotal role in atherosclerosis and injury-induced neointima formation. In this study, sEH expression in human autopsy atherosclerotic plaque was determined by immunohistochemistry. In cultured rat and human VSMCs, the phenotypic switching marker and sEH expression induced by platelet-derived growth factor-BB (PDGF-BB) were examined by Western blot analysis. Carotid-artery balloon injury was performed after adenovirus-mediated overexpression of sEH or oral administration of a potent sEH inhibitor in Sprague-Dawley rats. sEH was highly expressed in VSMCs of the intima and media within human atherosclerotic plaque. In vitro, PDGF-BB upregulated the expression in VSMCs after transcription and promoted cell proliferation and migration; the latter effect could be largely attenuated by an sEH inhibitor. Adenovirus-mediated overexpression of sEH could mimic the effect of PDGF-BB and induce VSMC proliferation and migration. In vivo, the sEH inhibitor led to a significant decrease in injury-induced neointima formation in a rat carotid-artery injury model. These data establish the effect of sEH expression on atherosclerotic progression and vascular remodeling after injury, thus identifying a novel integrative role for sEH in VSMC phenotypic modulation and migration. Blocking sEH activity may be a potential therapeutic approach for ameliorating vascular occlusive disease.