Regulation of differentiated properties and proliferation of arterial smooth muscle cells

Survivin regulates intracellular stiffness and extracellular matrix production in vascular smooth muscle cells

Vascular dysfunction is a common cause of cardiovascular diseases characterized by the narrowing and stiffening of arteries, such as atherosclerosis, restenosis, and hypertension. Arterial narrowing results from the aberrant proliferation of vascular smooth muscle cells (VSMCs) and their increased synthesis and deposition of extracellular matrix (ECM) proteins. These, in turn, are modulated by arterial stiffness, but the mechanism for this is not fully understood. We found that survivin is an important regulator of stiffness-mediated ECM synthesis and intracellular stiffness in VSMCs. Whole-transcriptome analysis and cell culture experiments showed that survivin expression is upregulated in injured femoral arteries in mice and in human VSMCs cultured on stiff fibronectin-coated hydrogels. Suppressed expression of survivin in human VSMCs significantly decreased the stiffness-mediated expression of ECM components related to arterial stiffening, such as collagen-I, fibronectin, and lysyl oxidase. By contrast, expression of these ECM proteins was rescued by ectopic expression of survivin in human VSMCs cultured on soft hydrogels. Interestingly, atomic force microscopy analysis showed that suppressed or ectopic expression of survivin decreases or increases intracellular stiffness, respectively. Furthermore, we observed that inhibiting Rac and Rho reduces survivin expression, elucidating a mechanical pathway connecting intracellular tension, mediated by Rac and Rho, to survivin induction. Finally, we found that survivin inhibition decreases FAK phosphorylation, indicating that survivin-dependent intracellular tension feeds back to maintain signaling through FAK. These findings suggest a novel mechanism by which survivin potentially modulates arterial stiffness.

Survivin as a mediator of stiffness-induced cell cycle progression and proliferation of vascular smooth muscle cells

Stiffened arteries are a pathology of atherosclerosis, hypertension, and coronary artery disease and a key risk factor for cardiovascular disease events. The increased stiffness of arteries triggers a phenotypic switch, hypermigration, and hyperproliferation of vascular smooth muscle cells (VSMCs), leading to neointimal hyperplasia and accelerated neointima formation. However, the mechanism underlying this trigger remains unknown. Our analyses of whole-transcriptome microarray data from mouse VSMCs cultured on stiff hydrogels simulating arterial pathology identified 623 genes that were significantly and differentially expressed (360 upregulated and 263 downregulated) relative to expression in VSMCs cultured on soft hydrogels. Functional enrichment and gene network analyses revealed that these stiffness-sensitive genes are linked to cell cycle progression and proliferation. Importantly, we found that survivin, an inhibitor of apoptosis protein, mediates stiffness-dependent cell cycle progression and proliferation as determined by gene network and pathway analyses, RT-qPCR, immunoblotting, and cell proliferation assays. Furthermore, we found that inhibition of cell cycle progression did not reduce survivin expression, suggesting that survivin functions as an upstream regulator of cell cycle progression and proliferation in response to ECM stiffness. Mechanistically, we found that the stiffness signal is mechanotransduced via the FAK-E2F1 signaling axis to regulate survivin expression, establishing a regulatory pathway for how the stiffness of the cellular microenvironment affects VSMC behaviors. Overall, our findings indicate that survivin is necessary for VSMC cycling and proliferation and plays a role in regulating stiffness-responsive phenotypes.

Arterial mechanics, extracellular matrix, and smooth muscle differentiation in carotid arteries deficient for Rac1

Stiffening of the extracellular matrix (ECM) occurs after vascular injury and contributes to the injury-associated proliferation of vascular smooth muscle cells (SMCs). ECM stiffness also activates Rac-GTP, and SMC Rac1 deletion strongly reduces the proliferative response to injury in vivo . However, ECM stiffening and Rac can affect SMC differentiation, which, in itself, can influence ECM stiffness and proliferation. Here, we used pressure myography and immunofluorescence analysis of mouse carotid arteries to ask if the reported effect of Rac1 deletion on in vivo SMC proliferation might be secondary to a Rac effect on basal arterial stiffness or SMC differentiation. The results show that Rac1 deletion does not affect the abundance of arterial collagen-I, -III, or -V, the integrity of arterial elastin, or the arterial responses to pressure, including the axial and circumferential stretch-strain relationships that are assessments of arterial stiffness. Medial abundance of alpha-smooth muscle actin and smooth muscle-myosin heavy chain, markers of the SMC differentiated phenotype, were not statistically different in carotid arteries containing or deficient in Rac1. Nor did Rac1 deficiency have a statistically significant effect on carotid artery contraction to KCl. Overall, these data argue that the inhibitory effect of Rac1 deletion on in vivo SMC proliferation reflects a primary effect of Rac1 signaling to the cell cycle rather than a secondary effect associated with altered SMC differentiation or arterial stiffness.

Protease-Activated Receptor 2 Controls Vascular Smooth Muscle Cell Proliferation in Cyclic AMP-Dependent Protein Kinase/Mitogen-Activated Protein Kinase Kinase 1/2-Dependent Manner

INTRODUCTION

Cardiovascular disorders are characterized by vascular smooth muscle (VSM) transition from a contractile to proliferative state. Protease-activated receptor 2 (PAR2) involvement in this phenotypic conversion remains unclear. We hypothesized that PAR2 controls VSM cell proliferation in phenotype-dependent manner and through specific protein kinases.

METHODS

Rat clonal low (PLo; P3-P6) and high passage (PHi; P10-P15) VSM cells were established as respective models of quiescent and proliferative cells, based on reduced PKG-1 and VASP. Western blotting determined expression of cytoskeletal/contractile proteins, PAR2, and select protein kinases. DNA synthesis and cell proliferation were measured 24-72 h following PAR2 agonism (SLIGRL; 100 nM-10 μm) with/without PKA (PKI; 10 μm), MEK1/2 (PD98059; 10 μm), and PI3K (LY294002; 1 μm) blockade.

RESULTS

PKG-1, VASP, SM22α, calponin, cofilin, and PAR2 were reduced in PHi versus PLo cells. Following PAR2 agonism, DNA synthesis and cell proliferation increased in PLo cells but decreased in PHi cells. Western analyses showed reduced PKA, MEK1/2, and PI3K in PHi versus PLo cells, and kinase blockade revealed PAR2 controls VSM cell proliferation through PKA/MEK1/2.

DISCUSSION

Findings highlight PAR2 and PAR2-driven PKA/MEK1/2 in control of VSM cell growth and provide evidence for continued investigation of PAR2 in VSM pathology.

FoxO3 normalizes Smad3-induced arterial smooth muscle cell growth

Transition of arterial smooth muscle (ASM) from a quiescent, contractile state to a growth-promoting state is a hallmark of cardiovascular disease (CVD), a leading cause of death and disability in the United States and worldwide. While many individual signals have been identified as important mechanisms in this phenotypic conversion, the combined impact of the transcription factors Smad3 and FoxO3 in ASM growth is not known. The purpose of this study was to determine that a coordinated, phosphorylation-specific relationship exists between Smad3 and FoxO3 in the control of ASM cell growth. Using a rat in vivo arterial injury model and rat primary ASM cell lysates and fractions, validated low and high serum in vitro models of respective quiescent and growth states, and adenoviral (Ad-) gene delivery for overexpression (OE) of individual and combined Smad3 and/or FoxO3, we hypothesized that FoxO3 can moderate Smad3-induced ASM cell growth. Key findings revealed unique cellular distribution of Smad3 and FoxO3 under growth conditions, with induction of both nuclear and cytosolic Smad3 yet primarily cytosolic FoxO3; Ad-Smad3 OE leading to cytosolic and nuclear expression of phosphorylated and total Smad3, with almost complete reversal of each with Ad-FoxO3 co-infection in quiescent and growth conditions; Ad-FoxO3 OE leading to enhanced cytosolic expression of phosphorylated and total FoxO3, both reduced with Ad-Smad3 co-infection in quiescent and growth conditions; Ad-FoxO3 inducing expression and activity of the ubiquitin ligase MuRF-1, which was reversed with concomitant Ad-Smad3 OE; and combined Smad3/FoxO3 OE reversing both the pro-growth impact of singular Smad3 and the cytostatic impact of singular FoxO3. A primary takeaway from these observations is the capacity of FoxO3 to reverse growth-promoting effects of Smad3 in ASM cells. Additional findings lend support for reciprocal antagonism of Smad3 on FoxO3-induced cytostasis, and these effects are dependent upon discrete phosphorylation states and cellular localization and involve MuRF-1 in the control of ASM cell growth. Lastly, results showing capacity of FoxO3 to normalize Smad3-induced ASM cell growth largely support our hypothesis, and overall findings provide evidence for utility of Smad3 and/or FoxO3 as potential therapeutic targets against abnormal ASM growth in the context of CVD.

Extracellular matrix proteins in construction and function of in vitro blood-brain barrier models

The blood-brain barrier (BBB) is a highly impermeable barrier separating circulating blood and brain tissue. A functional BBB is critical for brain health, and BBB dysfunction has been linked to the pathophysiology of diseases such as stroke and Alzheimer’s disease. A variety of models have been developed to study the formation and maintenance of the BBB, ranging from in vivo animal models to in vitro models consisting of primary cells or cells differentiated from human pluripotent stem cells (hPSCs). These models must consider the composition and source of the cellular components of the neurovascular unit (NVU), including brain microvascular endothelial cells (BMECs), brain pericytes, astrocytes, and neurons, and how these cell types interact. In addition, the non-cellular components of the BBB microenvironment, such as the brain vascular basement membrane (BM) that is in direct contact with the NVU, also play key roles in BBB function. Here, we review how extracellular matrix (ECM) proteins in the brain vascular BM affect the BBB, with a particular focus on studies using hPSC-derived in vitro BBB models, and discuss how future studies are needed to advance our understanding of how the ECM affects BBB models to improve model performance and expand our knowledge on the formation and maintenance of the BBB.

Cell contractility and focal adhesion kinase control circumferential arterial stiffness

Arterial stiffening is a hallmark of aging and cardiovascular disease. While it is well established that vascular smooth muscle cells (SMCs) contribute to arterial stiffness by synthesizing and remodeling the arterial extracellular matrix, the direct contributions of SMC contractility and mechanosensors to arterial stiffness, and particularly the arterial response to pressure, remain less well understood despite being a long-standing question of biomedical importance. Here, we have examined this issue by combining the use of pressure myography of intact carotid arteries, pharmacologic inhibition of contractility, and genetic deletion of SMC focal adhesion kinase (FAK). Biaxial inflation-extension tests performed at physiological pressures showed that acute inhibition of cell contractility with blebbistatin or EGTA altered vessel geometry and preferentially reduced circumferential, as opposed to axial, arterial stiffness in wild-type mice. Similarly, genetic deletion of SMC FAK, which attenuated arterial contraction to KCl, reduced vessel wall thickness and circumferential arterial stiffness in response to pressure while having minimal effect on axial mechanics. Moreover, these effects of FAK deletion were lost by treating arteries with blebbistatin or by inhibiting myosin light-chain kinase. The expression of arterial fibrillar collagens, the integrity of arterial elastin, or markers of SMC differentiation were not affected by the deletion of SMC FAK. Our results connect cell contractility and SMC FAK to the regulation of arterial wall thickness and directionally specific arterial stiffening.

A machine learning pipeline revealing heterogeneous responses to drug perturbations on vascular smooth muscle cell spheroid morphology and formation

Machine learning approaches have shown great promise in biology and medicine discovering hidden information to further understand complex biological and pathological processes. In this study, we developed a deep learning-based machine learning algorithm to meaningfully process image data and facilitate studies in vascular biology and pathology. Vascular injury and atherosclerosis are characterized by neointima formation caused by the aberrant accumulation and proliferation of vascular smooth muscle cells (VSMCs) within the vessel wall. Understanding how to control VSMC behaviors would promote the development of therapeutic targets to treat vascular diseases. However, the response to drug treatments among VSMCs with the same diseased vascular condition is often heterogeneous. Here, to identify the heterogeneous responses of drug treatments, we created an in vitro experimental model system using VSMC spheroids and developed a machine learning-based computational method called HETEROID (heterogeneous spheroid). First, we established a VSMC spheroid model that mimics neointima-like formation and the structure of arteries. Then, to identify the morphological subpopulations of drug-treated VSMC spheroids, we used a machine learning framework that combines deep learning-based spheroid segmentation and morphological clustering analysis. Our machine learning approach successfully showed that FAK, Rac, Rho, and Cdc42 inhibitors differentially affect spheroid morphology, suggesting that multiple drug responses of VSMC spheroid formation exist. Overall, our HETEROID pipeline enables detailed quantitative drug characterization of morphological changes in neointima formation, that occurs in vivo, by single-spheroid analysis.

Review of cadmium exposure and smoking-independent effects on atherosclerotic cardiovascular disease in the general population

BACKGROUND

Exposure to cadmium (Cd) via food and smoking is associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD). Blood and urine levels of Cd are established biomarkers of exposure.

OBJECTIVES

To review (1) the smoking-independent associations between Cd exposure and ASCVD, including the possible presence of a nonlinear dose-response relationship with Cd exposure and (2) the causal effects of Cd exposure on different stages of atherosclerosis.

METHODS

Narrative review.

RESULTS

Cd confers increased risk of ASCVD and asymptomatic atherosclerosis in the carotid and coronary arteries above B-Cd >0.5 μg/L or U-Cd >0.5 μg/g creatinine, but it has not been shown below a threshold of these exposure levels. Adjustment for smoking does not exclude the possibility of residual confounding, but several studies in never-smoking cohorts have shown associations between Cd and ASCVD, and experimental studies have demonstrated pro-atherosclerotic effects of Cd. Cd accumulates in arterial walls and atherosclerotic plaques, reaching levels shown to have proatherosclerotic effects. Suggested early effects are increased subendothelial retention of atherogenic lipoproteins, which become oxidized, and endothelial dysfunction and damage with increased permeability for monocytes, which in the intima turn to macrophages and then to foam cells. Later, Cd may contribute to plaque rupture and erosion by endothelial apoptosis and degradation of the fibrous cap. Finally, by having prothrombotic and antifibrinolytic effects, the CVD risk may be further increased.

CONCLUSIONS

There is strong evidence that Cd causes ASCVD above a suggested exposure level via mechanisms in early as well as the late stages of atherosclerotic disease.

Basement membrane proteins in various arterial beds from individuals with and without type 2 diabetes mellitus: a proteome study

BACKGROUND

Basement membrane (BM) accumulation is a hallmark of micro-vessel disease in diabetes mellitus (DM). We previously reported marked upregulation of BM components in internal thoracic arteries (ITAs) from type 2 DM (T2DM) patients by mass spectrometry. Here, we first sought to determine if BM accumulation is a common feature of different arteries in T2DM, and second, to identify other effects of T2DM on the arterial proteome.

METHODS

Human arterial samples collected during heart and vascular surgery from well-characterized patients and stored in the Odense Artery Biobank were analysed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). We included ascending thoracic aortas (ATA) (n = 10 (type 2 DM, T2DM) and n = 10 (non-DM)); laser capture micro-dissected plaque- and media compartments from carotid plaques (n = 10 (T2DM) and n = 9 (non-DM)); and media- and adventitia compartments from ITAs (n = 9 (T2DM) and n = 7 (non-DM)).

RESULTS

We first extended our previous finding of BM accumulation in arteries from T2DM patients, as 7 of 12 pre-defined BM proteins were significantly upregulated in bulk ATAs consisting of > 90% media. Although less pronounced, BM components tended to be upregulated in the media of ITAs from T2DM patients, but not in the neighbouring adventitia. Overall, we did not detect effects on BM proteins in carotid plaques or in the plaque-associated media. Instead, complement factors, an RNA-binding protein and fibrinogens appeared to be regulated in these tissues from T2DM patients.

CONCLUSION

Our results suggest that accumulation of BM proteins is a general phenomenon in the medial layer of non-atherosclerotic arteries in patients with T2DM. Moreover, we identify additional T2DM-associated effects on the arterial proteome, which requires validation in future studies.

Micro-RNA-338-3p Promotes the Development of Atherosclerosis by Targeting Desmin and Promoting Proliferation

Atherosclerosis (AS) is a dynamic and multi-stage process that involves various cells types, such as vascular smooth muscle cells (VSMCs) and molecules such as microRNAs. In this study, we investigated how miR-338-3p works in the process of AS. To determine how miR-338-3p was expressed in AS, an AS rat model was established and primary rat VSMCs were cultured. Real-time polymerase chain reaction was performed to detect miR-338-3p expression. Markers of different VSMC phenotypes were tested by Western blot. Immunofluorescent staining was employed to observe the morphologic changes of VSMCs transfected with miR-338-3p mimics. A dual luciferase reporter assay system was used to verify that desmin was a target of miR-338-3p. To further identify the role of miR-338-3p in the development of AS, VSMC proliferation and migration were evaluated by EdU incorporation assay, MTT assay, and wound healing assay. miR-338-3p expression was upregulated in the aortic tissues of an AS rat model and in primary rat VSMCs from a later passage. The transfection of miR-338-3p mimics in VSMCs promoted the synthetic cell phenotype. Bioinformatics analysis proposed desmin as a candidate target for miR-338-3p and the dual luciferase reporter assay confirmed in vivo that desmin was a direct target of miR-338-3p. The MTT and EdU incorporation assay revealed increased cell viability when miR-338-3p mimics were transfected. The increased expression of PCNA was a consistent observation, although a positive result was not obtained with respect to VSMC mobility. In AS, miR-338-3p expression was elevated. Elevated miR-338-3p inhibited the expression of desmin, thus promoting the contractile-to-synthetic VSMC phenotypic transition. In addition to morphologic changes, miR-338-3p enhanced the proliferative but not mobile ability of VSMCs. In summary, miR-338-3p promotes the development of AS.

Mechanosensitive smooth muscle cell phenotypic plasticity emerging from a null state and the balance between Rac and Rho

Reversible differentiation of vascular smooth muscle cells (VSMCs) plays a critical role in vascular biology and disease. Changes in VSMC differentiation correlate with stiffness of the arterial extracellular matrix (ECM), but causal relationships remain unclear. We show that VSMC plasticity is mechanosensitive and that both the de-differentiated and differentiated fates are promoted by the same ECM stiffness. Differential equations developed to model this behavior predicted that a null VSMC state generates the dual fates in response to ECM stiffness. Direct measurements of cellular forces, proliferation, and contractile gene expression validated these predictions and showed that fate outcome is mediated by Rac-Rho homeostasis. Rac, through distinct effects on YAP and TAZ, is required for both fates. Rho drives the contractile state alone, so its level of activity, relative to Rac, drives phenotypic choice. Our results show how the cellular response to a single ECM stiffness generates bi-stability and VSMC plasticity.

Reversible differentiation/de-differentiation of smooth muscle cells plays a critical role in vascular biology and disease. Talwar et al. show that these differentiated and de-differentiated phenotypes emerge from a null state that is regulated by ECM stiffness and bidirectional effects of Rac on YAP and TAZ transcriptional coregulators.

Regulation of SMC traction forces in human aortic thoracic aneurysms

Smooth muscle cells (SMCs) usually express a contractile phenotype in the healthy aorta. However, aortic SMCs have the ability to undergo profound changes in phenotype in response to changes in their extracellular environment, as occurs in ascending thoracic aortic aneurysms (ATAA). Accordingly, there is a pressing need to quantify the mechanobiological effects of these changes at single cell level. To address this need, we applied Traction Force Microscopy (TFM) on 759 cells coming from three primary healthy (AoPrim) human SMC lineages and three primary aneurysmal (AnevPrim) human SMC lineages, from age and gender matched donors. We measured the basal traction forces applied by each of these cells onto compliant hydrogels of different stiffness (4, 8, 12, 25 kPa). Although the range of force generation by SMCs suggested some heterogeneity, we observed that: 1. the traction forces were significantly larger on substrates of larger stiffness; 2. traction forces in AnevPrim were significantly higher than in AoPrim cells. We modelled computationally the dynamic force generation process in SMCs using the motor-clutch model and found that it accounts well for the stiffness-dependent traction forces. The existence of larger traction forces in the AnevPrim SMCs were related to the larger size of cells in these lineages. We conclude that phenotype changes occurring in ATAA, which were previously known to reduce the expression of elongated and contractile SMCs (rendering SMCs less responsive to vasoactive agents), tend also to induce stronger SMCs. Future work aims at understanding the causes of this alteration process in aortic aneurysms.

Distribution Pattern of Atherosclerosis in the Abdomen and Lower Extremities and Its Association with Clinical and Hematological Factors

PURPOSE

Abdominal arteries differ from the arteries located at the extremities in histological composition and clinical features. This study investigated the distributional pattern of atherosclerosis in arteries of the abdomen and lower extremities and its association with clinical and hematologic factors.

PATIENTS AND METHODS

This retrospective study included 227 patients with atherosclerosis who underwent computed tomography angiography (CTA) of the abdomen and lower extremities. The distributional pattern of atherosclerosis was categorized into type 1 (suprainguinal elastic), type 2 (infrainguinal muscular), and type 3 (both arterial involvement). Chi-square tests, Mann-Whitney U-tests, and logistic regression analysis were used to investigate the data.

RESULTS

Of the 227 patients, 132 (58%) had type 1 and 95 (42%) had type 3 atherosclerosis. None had type 2. Older age, heavier smoking, and higher levels of HbA1c and homocysteine were the significant risk factors for type 3 atherosclerosis (odds ratio: 1.076, 1.023, 1.426, and 1.130, respectively). Patients with type 3 showed significantly lower right and left ankle and toe brachial indices compared to type 1 (P: 0.029, 0.023, 0.003, and <0.001, respectively).

CONCLUSION

In arteries of the abdomen and lower extremities, atherosclerosis may occur initially at suprainguinal elastic arteries. In addition, the significant risk factors for type 3 atherosclerosis may contribute to the development of atherosclerosis at infrainguinal muscular arteries and deteriorate the peripheral arterial circulation. Therefore, if atherosclerotic lesions are found at the suprainguinal elastic arteries on CTA, to prevent atherosclerosis at infrainguinal muscular arteries and subsequent peripheral arterial ischemic disease, cessation of smoking and control of blood glucose and homocysteine may be recommended, especially in elderly patients.

Behaviour of Vascular Smooth Muscle Cells on Amine Plasma-Coated Materials with Various Chemical Structures and Morphologies

Amine-coated biodegradable materials based on synthetic polymers have a great potential for tissue remodeling and regeneration because of their excellent processability and bioactivity. In the present study, we have investigated the influence of various chemical compositions of amine plasma polymer (PP) coatings and the influence of the substrate morphology, represented by polystyrene culture dishes and polycaprolactone nanofibers (PCL NFs), on the behavior of vascular smooth muscle cells (VSMCs). Although all amine-PP coatings improved the initial adhesion of VSMCs, 7-day long cultivation revealed a clear preference for the coating containing about 15 at.% of nitrogen (CPA-33). The CPA-33 coating demonstrated the ideal combination of good water stability, a sufficient amine group content, and favorable surface wettability and morphology. The nanostructured morphology of amine-PP-coated PCL NFs successfully slowed the proliferation rate of VSMCs, which is essential in preventing restenosis of vascular replacements in vivo. At the same time, CPA-33-coated PCL NFs supported the continuous proliferation of VSMCs during 7-day long cultivation, with no significant increase in cytokine secretion by RAW 264.7 macrophages. The CPA-33 coating deposited on biodegradable PCL NFs therefore seems to be a promising material for manufacturing small-diameter vascular grafts, which are still lacking on the current market.

Apolipoprotein E deficient rats generated via zinc-finger nucleases exhibit pronounced in-stent restenosis

The long-term success of coronary stent implantation is limited by in-stent restenosis (ISR). In spite of a broad variety of animal models available, an ideal high-throughput model of ISR has been lacking. Apolipoprotein E (apoE) deficient rats enable the evaluation of human-sized coronary stents while at the same time providing an atherogenic phenotype. Whereas apoE deficient rats have been proposed as animal model of atherosclerosis, to date it is unknown whether they also develop pronounced ISR. We sought to assess ISR after abdominal aorta stent implantation in apoE deficient rats. A total of 42 rats (16 wildtype, 13 homozygous apoE^−/− and 13 heterozygous apoE^+/− rats) underwent abdominal aorta stent implantation. After 28 days blood samples were analyzed to characterize lipid profiles. ISR was assessed by histomorphometric means. Homozygous apoE^−/− rats exhibited significantly higher total cholesterol and low-density cholesterol levels than wildtype apoE^+/+ and heterozygous apoE^+/− rats. ISR was significantly pronounced in homozygous apoE^−/− rats as compared to wildtype apoE^+/+ (p = <0.0001) and heterozygous apoE^+/− rats (p = 0.0102) on western diet. Abdominal aorta stenting of apoE^−/− rats is a reliable model to investigate ISR after stent implantation and thus can be used for the evaluation of novel stent concepts. Apolipoprotein E (apoE) deficient rats have been proposed as animal model of atherosclerosis. We investigated the development of restenosis 28 days after stent implantation into the abdominal aorta of wildtype apoE^+/+, homozygous apoE^−/− and heterozygous apoE^+/− rats, respectively. Homozygous apoE^−/− rats exhibited significantly higher LDL and significantly lower HDL cholesterol levels compared to wildtype apoE^+/+ and heterozygous apoE^+/− rats. Restenosis after stent implantation was significantly pronounced in western-diet-fed homozygous apoE^−/− rats, accompanied by a significantly increased neointimal thickness. Thus, apoE knockout rats exhibit elevated restenosis and might provide a novel tool for testing of innovative stent concepts.

Elevated Neuropeptide Y in Endothelial Dysfunction Promotes Macrophage Infiltration and Smooth Muscle Foam Cell Formation

Endothelial dysfunction has been linked to vascular inflammation and foam cell formation but the underlying mechanisms still remain unclear. We sought to define the factors inducing inflammation and smooth muscle foam cell formation under endothelial dysfunction using endothelial nitric oxide synthase (eNOS)-deficient mice. Vascular smooth muscle cells (VSMCs) from eNOS-deficient mice displayed increased expression of macrophage-related genes and elevated lipid uptake. Neuropeptide Y (NPY) was upregulated in the aorta from the eNOS-deficient mice and promoted macrophage chemotaxis toward VSMCs while enhancing the activity of matrix metalloproteinase-3. Notably, NPY induced lipid uptake in VSMCs, facilitating smooth muscle foam cell formation, in association with enhanced expression of genes related to modified low-density lipoprotein uptake and macrophages. NPY was augmented by inflammatory pentraxin 3 (PTX3) in VSMCs. PTX3 enhanced macrophage migratory capacity through the NPY/neuropeptide Y receptor axis and this effect was attenuated by pharmacological inhibition with a receptor-specific antagonist. These observations suggest that endothelial dysfunction leads to the elevation of NPY that amplifies vascular inflammation by increasing inflammatory cell chemotaxis and triggers smooth muscle foam cell formation.

Spatially selective myosin regulatory light chain regulation is absent in dedifferentiated vascular smooth muscle cells but is partially induced by fibronectin and Klf4

The phosphorylation state of myosin regulatory light chain (MRLC) is central to the regulation of contractility that impacts cellular homeostasis and fate decisions. Rho-kinase (ROCK) and myosin light chain kinase (MLCK) are major kinases for MRLC documented to selectively regulate MRLC in a subcellular position-specific manner; specifically, MLCK in some nonmuscle cell types works in the cell periphery to promote migration, while ROCK does so at the central region to sustain contractility. However, it remains unclear whether or not the spatially selective regulation of the MRLC kinases is universally present in other cell types, including dedifferentiated vascular smooth muscle cells (SMCs). Here, we demonstrate the absence of the spatial regulation in dedifferentiated SMCs using both cell lines and primary cells. Thus, our work is distinct from previous reports on cells with migratory potential. We also observed that the spatial regulation is partly induced upon fibronectin stimulation and Krüppel-like factor 4 overexpression. To find clues to the mechanism, we reveal how the phosphorylation state of MRLC is determined within dedifferentiated A7r5 SMCs under the enzymatic competition among three major regulators ROCK, MLCK, and MRLC phosphatase (MLCP). We show that ROCK, but not MLCK, predominantly regulates the MRLC phosphorylation in a manner distinct from previous in vitro-based and in silico-based reports. In this ROCK-dominating cellular system, the contractility at physiological conditions was regulated at the level of MRLC diphosphorylation, because its monophosphorylation is already saturated. Thus, the present study provides insights into the molecular basis underlying the absence of spatial MRLC regulation in dedifferentiated SMCs.

Endothelial Function: A Short Guide for the Interventional Cardiologist

An impaired function of the coronary endothelium is an important determinant of all stages of atherosclerosis, from initiation, to mediation of functional phenomena—such as spasm and plaque erosion, to atherothrombotic complications. Endothelial function is modified by therapies, including stent implantation. Finally, endothelial function changes over time, in response to physical stimuli and pharmocotherapies, and its assessment might provide information on how individual patients respond to specific therapies. In this review, we describe the role of the endothelium in the continuum of coronary atherosclerosis, from the perspective of the interventional cardiologist. In the first part, we review the current knowledge of the role of endothelial (dys)function on atherosclerotic plaque progression/instabilization and on the mechanisms of ischemia, in the absence of coronary artery stenosis. In the second part of this review, we describe the impact of coronary artery stenting on endothelial function, platelet aggregation, and inflammation.

The effects of stenting on coronary endothelium from a molecular biological view: Time for improvement?

Coronary artery stenting following balloon angioplasty represents the gold standard in revascularization of coronary artery stenoses. However, stent deployment as well as percutaneous transluminal coronary angioplasty (PTCA) alone causes severe injury of vascular endothelium. The damaged endothelium is intrinsically repaired by locally derived endothelial cells and by circulating endothelial progenitor cells from the blood, leading to re‐population of the denuded regions within several weeks to months. However, the process of re‐endothelialization is often incomplete or dysfunctional, promoting in‐stent thrombosis and restenosis. The molecular and biomechanical mechanisms that influence the process of re‐endothelialization in stented segments are incompletely understood. Once the endothelium is restored, endothelial function might still be impaired. Several strategies have been followed to improve endothelial function after coronary stenting. In this review, the effects of stenting on coronary endothelium are outlined and current and future strategies to improve endothelial function after stent deployment are discussed.

A role for collagen type IV in cardiovascular disease?

Over the past decade, studies have repeatedly found single-nucleotide polymorphisms located in the collagen ( COL) 4A1 and COL4A2 genes to be associated with cardiovascular disease (CVD), and the 13q34 locus harboring these genes is one of ~160 genome-wide significant risk loci for coronary artery disease. COL4A1 and COL4A2 encode the α₁- and α₂-chains of collagen type IV, a major component of basement membranes in various tissues including arteries. Despite the growing body of evidence indicating a role for collagen type IV in CVD, remarkably few studies have aimed to directly investigate such a role. The purpose of this review is to summarize the clinical reports linking 13q34 to coronary artery disease, atherosclerosis, and artery stiffening and to assemble the scattered pieces of evidence from experimental studies based on vascular cells and tissue collectively supporting a role for collagen type IV in atherosclerosis and other macrovascular disease conditions.

Mining the Stiffness-Sensitive Transcriptome in Human Vascular Smooth Muscle Cells Identifies Long Noncoding RNA Stiffness Regulators

OBJECTIVE

Vascular extracellular matrix stiffening is a risk factor for aortic and coronary artery disease. How matrix stiffening regulates the transcriptome profile of human aortic and coronary vascular smooth muscle cells (VSMCs) is not well understood. Furthermore, the role of long noncoding RNAs (lncRNAs) in the cellular response to stiffening has never been explored. This study characterizes the stiffness-sensitive (SS) transcriptome of human aortic and coronary VSMCs and identifies potential key lncRNA regulators of stiffness-dependent VSMC functions.

APPROACH AND RESULTS

Aortic and coronary VSMCs were cultured on hydrogel substrates mimicking physiological and pathological extracellular matrix stiffness. Total RNAseq was performed to compare the SS transcriptome profiles of aortic and coronary VSMCs. We identified 3098 genes (2842 protein coding and 157 lncRNA) that were stiffness sensitive in both aortic and coronary VSMCs (false discovery rate <1%). Hierarchical clustering revealed that aortic and coronary VSMCs grouped by stiffness rather than cell origin. Conservation analyses also revealed that SS genes were more conserved than stiffness-insensitive genes. These VSMC SS genes were less tissue-type specific and expressed in more tissues than stiffness-insensitive genes. Using unbiased systems analyses, we identified MALAT1 as an SS lncRNA that regulates stiffness-dependent VSMC proliferation and migration in vitro and in vivo.

CONCLUSIONS

This study provides the transcriptomic landscape of human aortic and coronary VSMCs in response to extracellular matrix stiffness and identifies novel SS human lncRNAs. Our data suggest that the SS transcriptome is evolutionarily important to VSMCs function and that SS lncRNAs can act as regulators of stiffness-dependent phenotypes.

Layered smooth muscle cell-endothelial progenitor cell sheets derived from the bone marrow augment postinfarction ventricular function

OBJECTIVE

The angiogenic potential of endothelial progenitor cells (EPCs) may be limited by the absence of their natural biologic foundation, namely smooth muscle pericytes. We hypothesized that joint delivery of EPCs and smooth muscle cells (SMCs) in a novel, totally bone marrow-derived cell sheet will mimic the native architecture of a mature blood vessel and act as an angiogenic construct to limit post infarction ventricular remodeling.

METHODS

Primary EPCs and mesenchymal stem cells were isolated from bone marrow of Wistar rats. Mesenchymal stem cells were transdifferentiated into SMCs by culture on fibronectin-coated culture dishes. Confluent SMCs topped with confluent EPCs were detached from an Upcell dish to create a SMC-EPC bi-level cell sheet. A rodent model of ischemic cardiomyopathy was then created by ligating the left anterior descending artery. Rats were randomized into 3 groups: cell sheet transplantation (n = 9), no treatment (n = 12), or sham surgery control (n = 7).

RESULTS

Four weeks postinfarction, mature vessel density tended to increase in cell sheet-treated animals compared with controls. Cell sheet therapy significantly attenuated the extent of cardiac fibrosis compared with that of the untreated group (untreated vs cell sheet, 198 degrees [interquartile range (IQR), 151-246 degrees] vs 103 degrees [IQR, 92-113 degrees], P = .04). Furthermore, EPC-SMC cell sheet transplantation attenuated myocardial dysfunction, as evidenced by an increase in left ventricular ejection fraction (untreated vs cell sheet vs sham, 33.5% [IQR, 27.8%-35.7%] vs 45.9% [IQR, 43.6%-48.4%] vs 59.3% [IQR, 58.8%-63.5%], P = .001) and decreases in left ventricular dimensions.

CONCLUSIONS

The bone marrow-derived, spatially arranged SMC-EPC bi-level cell sheet is a novel, multilineage cellular therapy obtained from a translationally practical source. Interactions between SMCs and EPCs augment mature neovascularization, limit adverse remodeling, and improve ventricular function after myocardial infarction.

FAM3B mediates high glucose-induced vascular smooth muscle cell proliferation and migration via inhibition of miR-322-5p

The proliferation and migration of vascular smooth muscle cells (VSMCs) play an essential role during the development of cardiovascular diseases (CVDs). While many factors potentially contribute to the abnormal activation of VSMCs, hyperglycemia is generally believed to be a major causative factor. On the other hand, FAM3B (named PANDER for its secretory form) is a uniquely structured protein strongly expressed within and secreted from the endocrine pancreas. FAM3B is co-secreted with insulin from the β-cell upon glucose stimulation and regulates glucose homeostasis. In the present study, we sought to determine the roles of FAM3B in the regulation of VSMC physiology, especially under the hyperglycemic condition. We found that FAM3B expression was induced by hyperglycemia both in vivo and in vitro. FAM3B knockdown inhibited, whereas FAM3B overexpression accelerated VSMC proliferation and migration. At the molecular level, FAM3B inhibited miR-322-5p expression, and enforced expression of miR-322-5p antagonized FAM3B-induced VSMC proliferation and migration, suggesting that FAM3B facilitated VSMC pathological activation via miR-322-5p. Taken together, FAM3B mediates high glucose-induced VSMC proliferation and migration via inhibition of miR-322-5p. Thus, FAM3B may therefore serve as a novel therapeutic target for diabetes-related CVDs.

miR-26b-5p regulates hypoxia-induced phenotypic switching of vascular smooth muscle cells via the TGF-β/Smad4 signaling pathway

Hypoxia contributes to the phenotypic switch of vascular smooth muscle cells (VSMCs). Various microRNAs (miRNAs) participate in this process as post‑transcriptional regulators, however the mechanism remains unclear. In the present study, mouse VSMCs (mVSMCs) harvested from aortas were cultured in normoxic and hypoxic conditions, and the mRNA levels of miR-26b-5p, desmin, H‑caldesmon and smoothelin were quantified using reverse transcription‑quantitative polymerase chain reaction. Following treatment with a miR‑26b‑5p antagonist (agomir) or non‑targeting control (scramble), the cell areas of normoxic and hypoxic mVSMCs were analyzed by immunofluorescence staining. In addition, the protein expression levels of collagen Iα, Smad2/phosphorylated (p)‑Smad2, Smad3/p‑Smad3 and Smad4 were determined by western blotting. Potential miRNA26b‑5p binding sequences in the 3'‑untranslated region (UTR) of Smad4 were investigated, and the distribution of Smad4 in mVSMCs was visualized using immunofluorescence methods. Hypoxic mVSMCs exhibited a significant downregulation miR‑26b‑5p, upregulation of hypoxia inducible factor‑1α mRNA and suppression of desmin, H‑caldesmon and smoothelin mRNA levels. Additionally, miR‑26b‑5p agomir reduced the cell area and decreased collagen Iα expression levels in hypoxic mVSMCs compared with normoxic mVSMCs transfected with agomir, and the area was comparable with those of normoxic mVSMCs transfected with agomir or scramble. Furthermore, miR‑26b‑5p suppressed Smad4 expression in hypoxic mVSMCs, but did not change the expression levels of Smad2 and Smad3, p‑Smad2 and p‑Smad3, however p‑Smad2 and p‑Smad3 levels were upregulated in response to hypoxic stimuli. Additionally, the miR‑26b‑5p agomir caused weak immunoreactivity with Smad4 in hypoxic mVSMCs. The binding motif of miR‑26b‑5p in the Smad4 3'‑UTR was identified as UACUUGA at position 978-984. These findings suggest that miR‑26b‑5p regulates hypoxia‑induced phenotypic switching of VSMCs via the transforming growth factor β/Smad4 signaling pathway.

Influence of cell confluence on the cAMP signalling pathway in vascular smooth muscle cells

The influence of cell confluence on the β-adrenoceptor (β-AR)/cAMP/phosphodiesterase (PDE) pathway was investigated in cultured rat aortic smooth muscle cells (RASMCs). Cells were plated either at low density (LD: 3·10³cells/cm²) or high density (HD: 3·10⁴cells/cm²) corresponding to non-confluent or confluent cells, respectively, on the day of experiment. β-AR-stimulated cAMP was monitored in real-time using the fluorescence resonance energy transfer (FRET)-based cAMP sensor, Epac2-camps. A brief application (15s) of the β-AR agonist isoprenaline (Iso) induced a typical transient FRET signal, reflecting cAMP production followed by its rapid degradation. The amplitude of this response, which increased with the concentration of Iso (10 or 100nM), was higher in HD than in LD cells, whatever the Iso concentration used. However, activation of adenylyl cyclase by L-858051 (100μM) induced a similar saturating response in both LD and HD cells. A β₁-AR antagonist (CGP 20712A, 100nM) reduced the Iso (100nM) response in HD but not LD cells, whereas a β₂-AR antagonist (ICI 118,551, 5nM) reduced this response in HD cells and almost abolished it in LD cells. Competitive [¹²⁵I]-ICYP binding experiments with betaxolol, a β-AR ligand, identified two binding sites in HD cells, corresponding to β₁- and β₂-ARs with a proportion of 11% and 89%, respectively, but only one binding site in LD cells, corresponding to β₂-ARs. Total cAMP-PDE activity (assessed by a radioenzymatic assay) was increased in HD cells compared to LD cells. This increase was associated with a rise in mRNA expression of five cAMP-PDEs subtypes (PDE1A, 3A, 4A, 4B and 7B) in HD cells, and a decrease in basal [cAMP]_i (assessed by an EIA assay). PDE4 inhibition with Ro-20-1724 (10μM) strongly prolonged the Iso response in LD and HD cells, whereas PDE3 inhibition with cilostamide (1μM) slightly prolonged Iso response only in LD cells. Interestingly, inhibition of PDE4 unmasked an effect of PDE3 in HD cells. Our results show that in cultured RASMCs, the β-AR/cAMP/PDE signalling pathway is substantially modulated by the cell density. In HD cells, Iso response involves both β₁- and β₂-AR stimulation and is mainly controlled by PDE4, PDE3 being recruited only after PDE4 inhibition. In LD cells, Iso response involves only β₂-AR stimulation and is controlled by PDE4 and to a lower degree by PDE3. This low density state is associated with an absence of membrane expression of the β₁-AR, a lower cAMP-PDE activity and a higher basal [cAMP]_i. This study highlights the critical role of the cellular environment in controlling the vascular β-AR signalling.

Effects of five candidate laxatives derived from Liriope platyphylla on the 5-HT receptor signaling pathway in three cell types present in the transverse colon

The laxative effects of aqueous extract of Liriope platyphylla (AEtLP) on loperamide (Lop)‑induced constipation have been reported; however, the key compounds and the mechanism underlying these effects remain unclear. Therefore, the laxative effects of five candidates derived from L. platyphylla: Diosgenin (DG), 5-hydroxymethylfurfural (5-HMF), adenosine (AD), hydroxypropyl cellulose (HPC) and uridine (UD) were investigated by examining the alteration of G protein α (Gα) expression, protein kinase C (PKC) phosphorylation and inositol triphosphate (IP3) concentration levels in the 5-hydroxytryptamine (5‑HT; serotonin) receptor signaling pathway. Primary rat intestine smooth muscle cells (pRISMCs), intestinal epithelial cells (IEC)‑18 and B35 cells were cotreated with Lop and the five compounds in order to screen the candidates. AEtLP, prucalopride (PCP) and bisacodyl (BS) served as positive controls. In pRISMCs, Gα expression levels were recovered in the majority of candidate‑treated groups, whereas PKC phosphorylation recovery was observed only in the DG, 5‑HMF and AD treatment groups. In IEC‑18 cells, the AD treatment group mimicked the effects of PCP on PKC phosphorylation levels, whereas the DG, 5‑HMF, HPC and UD treatment groups mimicked the effects of AEtLP and BS. In B35 cells, a greater upregulation of PKC phosphorylation levels were observed in the UD treatment group compared with the PCP and BS treatment groups, whereas DG, 5‑HMF and AD treatment reduced the PKC phosphorylation levels to a greater extent than AEtLP treatment. However, effects similar to AEtLP, PCP and BS on Gα expression levels were not detected in any treatment groups in IEC‑18 and B35 cells. Furthermore, the level of IP3 was enhanced only in pRISMCs, in which all five candidates were effective, while the greatest concentration was observed in the UD treatment group. In conclusion, the results of the present study suggest that UD may be considered the compound with the greatest laxative activity, which may regulate the 5‑HT receptor signaling pathway.

Isolation and trans-differentiation of mesenchymal stromal cells into smooth muscle cells: Utility and applicability for cell-sheet engineering

BACKGROUND

Bone marrow (BM)-derived mesenchymal stromal cells (MSCs) have shown potential to differentiate into various cell types, including smooth muscle cells (SMCs). The extracellular matrix (ECM) represents an appealing and readily available source of SMCs for use in tissue engineering. In this study, we hypothesized that the ECM could be used to induce MSC differentiation to SMCs for engineered cell-sheet construction.

METHODS

Primary MSCs were isolated from the BM of Wistar rats, transferred and cultured on dishes coated with 3 different types of ECM: collagen type IV (Col IV), fibronectin (FN), and laminin (LM). Primary MSCs were also included as a control. The proportions of SMC (a smooth muscle actin [aSMA] and SM22a) and MSC markers were examined with flow cytometry and Western blotting, and cell proliferation rates were also quantified.

RESULTS

Both FN and LM groups were able to induce differentiation of MSCs toward smooth muscle-like cell types, as evidenced by an increase in the proportion of SMC markers (aSMA; Col IV 42.3 ± 6.9%, FN 65.1 ± 6.5%, LM 59.3 ± 7.0%, Control 39.9 ± 3.1%; P = 0.02, SM22; Col IV 56.0 ± 7.7%, FN 74.2 ± 6.7%, LM 60.4 ± 8.7%, Control 44.9 ± 3.6%) and a decrease in that of MSC markers (CD105: Col IV 64.0 ± 5.2%, FN 57.6 ± 4.0%, LM 60.3 ± 7.0%, Control 85.3 ± 4.2%; P = 0.03). The LM group showed a decrease in overall cell proliferation, whereas FN and Col IV groups remained similar to control MSCs (Col IV, 9.0 ± 2.3%; FN, 9.8 ± 2.5%; LM, 4.3 ± 1.3%; Control, 9.8 ± 2.8%).

CONCLUSIONS

Our findings indicate that ECM selection can guide differentiation of MSCs into the SMC lineage. Fibronectin preserved cellular proliferative capacity while yielding the highest proportion of differentiated SMCs, suggesting that FN-coated materials may be facilitate smooth muscle tissue engineering.

Measuring the Stiffness of Ex Vivo Mouse Aortas Using Atomic Force Microscopy

Arterial stiffening is a significant risk factor and biomarker for cardiovascular disease and a hallmark of aging. Atomic force microscopy (AFM) is a versatile analytical tool for characterizing viscoelastic mechanical properties for a variety of materials ranging from hard (plastic, glass, metal, etc.) surfaces to cells on any substrate. It has been widely used to measure the stiffness of cells, but less frequently used to measure the stiffness of aortas. In this paper, we will describe the procedures for using AFM in contact mode to measure the ex vivo elastic modulus of unloaded mouse arteries. We describe our procedure for isolation of mouse aortas, and then provide detailed information for the AFM analysis. This includes step-by-step instructions for alignment of the laser beam, calibration of the spring constant and deflection sensitivity of the AFM probe, and acquisition of force curves. We also provide a detailed protocol for data analysis of the force curves.

Ultrastructural Changes in the Venous Wall Induced by Experimental Diabetes: Preliminary Findings

Objective:

To study whether experimental streptozotocin (STZ) induced diabetes results in structural alterations to the venous wall of the femoral vein in adult rats, in order to develop further studies using this model.

Design:

A prospective study of femoral veins obtained from controls and STZ-induced diabetes rats.

Setting:

Department of Morphology, Universidad de Las Palmas de Gran Canaria, Spain.

Interventions:

Experimental diabetes induced by intraperitoneal injection of streptozotocin.

Main outcome measures:

The samples were studied at 6 and 12 weeks post-injection using light and transmission electron microscopy.

Results:

The results show that the venous wall is affected by an increase in the deposition of extracellular tissue. In addition the endothelial, muscular and adventitial cells show morphological changes.

Conclusions:

Our results demonstrate significant alterations in the venous wall due to hyperglycaemia in the STZ-animal model.

Oxidative Stress and Cardiovascular Dysfunction Associated with Cadmium Exposure: Beneficial Effects of Curcumin and Tetrahydrocurcumin

Cadmium (Cd) is a non-essential heavy metal with high toxicity potential. Humans are exposed to Cd present in diet, polluted air, and cigarette smoke. Cd exposure has been associated with increased risk of chronic diseases, including hypertension, atherosclerosis, diabetes, and nephropathy, all of which could be attributable to dysfunctional endothelial and smooth muscle cells. Cd toxicity is correlated with increased reactive oxygen formation and depletion of antioxidants, resulting in an oxidative stress. Chelation of Cd has proved useful in the removal of the Cd burden. However, several chelating agents cause side effects in clinical usage. Recent studies have shown that the antioxidant compounds curcumin and tetrahydrocurcumin can alleviate vascular dysfunction and high blood pressure caused by Cd toxicity. In chronic Cd exposure, these antioxidants protect vascular endothelium by increasing nitric oxide (NO•) bioavailability and improving vascular function. Antioxidant activity against Cd intoxication results directly and/or indirectly through free radical scavenging, metal chelation, enhanced expression of the antioxidant defense system, regulation of inflammatory enzymes, increase in NO• bioavailability, and reduction of gastrointestinal absorption and tissue Cd accumulation. This review summarizes current knowledge of Cd-induced oxidative stress and cardiovascular dysfunction and a possible protective effect conferred by the antioxidants curcumin and tetrahydrocurcumin.

Role of macrophage colony-stimulating factor in the development of neointimal thickening following arterial injury

Evidence suggests that macrophage colony-stimulating factor (M-CSF) participates critically in atherosclerosis; little is known about the role of M-CSF in the development of neointimal hyperplasia following mechanical vascular injury. We examined the expression of M-CSF and its receptor, c-fms, in rodent and rabbit models of arterial injury. Injured rat carotid arteries expressed 3- to 10-fold higher levels of M-CSF and c-fms mRNA and protein following balloon injury as compared to uninjured arteries. In the rabbit, M-CSF protein expression was greatest in neointimal smooth muscle cells (SMCs) postinjury, with some expression in medial SMCs. M-CSF-positive SMCs exhibited markers of proliferation. At 30days postinjury, neointimal SMCs in the adjacent healed area near the border between injured and uninjured zone lost both proliferative activity and overexpression of M-CSF. The presence of induced M-CSF and c-fms expression correlated with the initiation of SMCs proliferation. M-CSF stimulated incorporation of [(3)H] thymidine in human aortic smooth muscle cells in a concentration-dependent manner. Serum-free conditioned medium from aortic SMCs also promoted DNA synthesis, and this effect was blocked by M-CSF specific antibody. To test further the role of M-CSF in vivo, we induced arterial injury by placing a periadventitial collar around the carotid arteries in compound mutant mice lacking apolipoprotein apoE (apoE(-/-)) and M-CSF. Loss of M-CSF abolished the neointimal hyperplastic response to arterial injury in apoE(-/-) mice. Local delivery of M-CSF to the injured artery restored neointimal proliferation, suggesting a critical role of M-CSF for the development of neointimal thickening following arterial injury.

Plumericin inhibits proliferation of vascular smooth muscle cells by blocking STAT3 signaling via S-glutathionylation

The etiology of atherosclerosis and restenosis involves aberrant inflammation and proliferation, rendering compounds with both anti-inflammatory and anti-mitogenic properties as promising candidates for combatting vascular diseases. A recent study identified the iridoid plumericin as a new scaffold inhibitor of the pro-inflammatory NF-κB pathway in endothelial cells. We here examined the impact of plumericin on the proliferation of primary vascular smooth muscle cells (VSMC). Plumericin inhibited serum-stimulated proliferation of rat VSMC. It arrested VSMC in the G1/G0-phase of the cell cycle accompanied by abrogated cyclin D1 expression and hindered Ser 807/811-phosphorylation of retinoblastoma protein. Transient depletion of glutathione by the electrophilic plumericin led to S-glutathionylation as well as hampered Tyr705-phosphorylation and activation of the transcription factor signal transducer and activator of transcription 3 (Stat3). Exogenous addition of glutathione markedly prevented this inhibitory effect of plumericin on Stat3. It also overcame downregulation of cyclin D1 expression and the reduction of biomass increase upon serum exposure. This study revealed an anti-proliferative property of plumericin towards VSMC which depends on plumericin's thiol reactivity and S-glutathionylation of Stat3. Hence, plumericin, by targeting at least two culprits of vascular dysfunction -inflammation and smooth muscle cell proliferation -might become a promising electrophilic lead compound for vascular disease therapy.

Decreased levels of stem cell factor in subjects with incident coronary events

BACKGROUND

It has been proposed that vascular progenitor cells play an important role in vascular repair, but their possible clinical importance in cardiovascular disease has not been fully characterized. Vascular endothelial growth factor A, placental growth factor and stem cell factor (SCF) are three growth factors that are important in recruiting vascular progenitor cells. In this study, we investigated the association between the plasma levels of these growth factors and incident coronary events (CEs).

METHODS

Levels of the three growth factors were measured using the proximity extension assay technique in baseline plasma samples from 384 subjects with a first CE (mean follow-up 14.0 ± 4.3 years) and 409 event-free control subjects matched by sex and age, as well as in homogenates from 201 endarterectomy specimens.

RESULTS

After controlling for known cardiovascular disease risk factors in a Cox regression model, subjects in the lowest SCF tertile had a hazard ratio of 1.70 (95% confidence interval 1.14-2.54) compared with subjects in the highest SCF tertile. Lower SCF levels were also associated with more severe carotid disease, less fibrous atherosclerotic plaques and an increased incidence of heart failure. Expression of the SCF receptor c-kit was demonstrated in the subendothelial layer and fibrous cap of human atherosclerotic plaques. Smokers and subjects with diabetes had decreased levels of SCF compared with control subjects.

CONCLUSION

To our knowledge, this is the first clinical study to provide evidence to support a key role for SCF and progenitor cells in vascular repair. We suggest that the SCF-c-kit pathway may be a promising biomarker and therapeutic target in cardiovascular disease.

Isolation, Culture, and Characterization of Vascular Smooth Muscle Cells

Smooth muscle cells (SMC) are the predominant cell type involved in the pathogenesis of atherosclerosis, vascular calcification and restenosis after angioplasty; however, they are also important in the de novo formation of blood vessels through differentiation of mesenchymal cells under the influence of mediators secreted by endothelial cells. In angiogenesis, vascular SMC are formed by proliferation of existing SMC or maturation and differntiation of pericytes. Experimental findings have demonstrated a potential role of putative smooth muscle progenitor cells in the circulation or within adult tissues and the perivascular adventitia in the development of atherosclerotic plaques, restenosis and angiogenesis. Modulation of vascular smooth muscle phenotype, SMC migration and hypertrophy are now recognized as key events in the development of vascular diseases. This has led to an increase in experimental research on SMC function in response to growth factors, extracellular matrix components, modified lipoproteins, biomechanical forces and other pro-atherogenic and pro-angiogenic mediators to address the cellular mechanisms involved. This chapter highlights well established methodologies used for vascular SMC and pericyte isolation and culture as well as their characterisation. A better understanding of vascular SMC and pericyte biology and their phenotypic modulation is required to identify therapeutic strategies to target angiogenesis and treat cardiovascular diseases.

Matrix metalloproteinase-12 is an essential mediator of acute and chronic arterial stiffening

Arterial stiffening is a hallmark of aging and risk factor for cardiovascular disease, yet its regulation is poorly understood. Here we use mouse modeling to show that matrix metalloproteinase-12 (MMP12), a potent elastase, is essential for acute and chronic arterial stiffening. MMP12 was induced in arterial smooth muscle cells (SMCs) after acute vascular injury. As determined by genome-wide analysis, the magnitude of its gene induction exceeded that of all other MMPs as well as those of the fibrillar collagens and lysyl oxidases, other common regulators of tissue stiffness. A preferential induction of SMC MMP12, without comparable effect on collagen abundance or structure, was also seen during chronic arterial stiffening with age. In both settings, deletion of MMP12 reduced elastin degradation and blocked arterial stiffening as assessed by atomic force microscopy and immunostaining for stiffness-regulated molecular markers. Isolated MMP12-null SMCs sense extracellular stiffness normally, indicating that MMP12 causes arterial stiffening by remodeling the SMC microenvironment rather than affecting the mechanoresponsiveness of the cells themselves. In human aortic samples, MMP12 levels strongly correlate with markers of SMC stiffness. We conclude that MMP12 causes arterial stiffening in mice and suggest that it functions similarly in humans.

IL-22 affects smooth muscle cell phenotype and plaque formation in apolipoprotein E knockout mice

OBJECTIVE

IL-22 is a recently discovered cytokine that belongs to the family of IL-10 related cytokines. It is produced by activated T-cells and innate lymphoid cells and has been suggested to be involved in tissue repair. As both inflammation and repair play important roles in atherosclerosis we investigated if IL-22 deficiency influences the disease process in Apoe(-/-) mice.

METHODS

We generated IL-22(-/-)Apoe(-/-) mice and fed them high-fat-diet for 14 weeks to characterize atherosclerosis development.

RESULTS

IL-22(-/-)Apoe(-/-) mice exhibited reduced plaque size both in the aorta (p = 0.0036) and the aortic root compared (p = 0.0012) with Apoe(-/-) controls. Moreover, plaque collagen was reduced in IL-22(-/-)Apoe(-/-) mice (p = 0.02) and this was associated with an increased expression of smooth muscle cell (SMC)-α-actin (p = 0.04) and caldesmon (p = 0.016) in the underlying media. Carotid arteries from IL-22(-/-)Apoe(-/-) mice displayed increased expression of genes associated with a contractile SMC phenotype e.g. α-actin (p = 0.004) and caldesmon (p = 0.03). Arterial SMCs were shown to express the IL-22 receptor and in vitro exposure to IL-22 resulted in a down-regulation of alpha actin and caldesmon gene expression in these cells.

CONCLUSION

Our observations demonstrate that IL-22 is involved in plaque formation and suggest that IL-22 released by immune cells is involved in activation of vascular repair by stimulating medial SMC dedifferentiation into a synthetic phenotype. This response contributes to plaque growth by enabling SMC migration into the intima but may also help to stabilize the plaque.

Notch signaling governs phenotypic modulation of smooth muscle cells

A feature of vascular smooth muscle cells is their unique ability to exist in multiple phenotypes permitting a broad range of functions that include contraction, proliferation, or synthesis and secretion of extracellular matrix. Although it is known that these phenotypes can be overlapping, the mechanisms that regulate phenotypic modulation are still unclear. Given that endothelial cells are known to convey signals to smooth muscle cells that govern their activities within the vasculature; we sought to better define how endothelial cells regulate phenotypic changes of smooth muscle cells in coculture conditions. Using human aortic smooth muscle cells, we show that endothelial cells promote an increase in a differentiated/contractile phenotype while decreasing proliferation. Analysis of the synthetic phenotype demonstrates that endothelial cells also increase collagen synthesis and secretion. Characterization of pathways important for these endothelial cell-dependent phenotypes reveal that Notch signaling plays an important role in the establishment of these smooth muscle properties. These data highlight the ability of endothelial cells to control phenotypic modulation in a unique and previously undefined manner.

Smooth muscle-protein translocation and tissue function

Smooth muscle (SM) tissue is a complex organization of multiple cell types and is regulated by numerous signaling molecules (neurotransmitters, hormones, cytokines, etc.). SM contractile function can be regulated via expression and distribution of the contractile and cytoskeletal proteins, and activation of any of the second messenger pathways that regulate them. Spatial-temporal changes in the contractile, cytoskeletal or regulatory components of SM cells (SMCs) have been proposed to alter SM contractile activity. Ca(2+) sensitization/desensitization can occur as a result of changes at any of these levels, and specific pathways have been identified at all of these levels. Understanding when and how proteins can translocate within the cytoplasm, or to-and-from the plasmalemma and the cytoplasm to alter contractile activity is critical. Numerous studies have reported translocation of proteins associated with the adherens junction and G protein-coupled receptor activation pathways in isolated SMC systems. Specific examples of translocation of vinculin to and from the adherens junction and protein kinase C (PKC) and 17 kDa PKC-potentiated inhibitor of myosin light chain phosphatase (CPI-17) to and from the plasmalemma in isolated SMC systems but not in intact SM tissues are discussed. Using both isolated SMC systems and SM tissues in parallel to pursue these studies will advance our understanding of both the role and mechanism of these pathways as well as their possible significance for Ca(2+) sensitization in intact SM tissues and organ systems.

Kruppel-like factors in an endothelial and vascular smooth muscle cell coculture model: impact of a diabetic environment and vitamin D

Endothelial cells (EC) and vascular smooth muscle cells (VSMC) are involved in the development of local and diffuse vasculopathies by participating in inflammatory processes that can lead to uncontrolled vascular complications. Our aim was to study the possible interactions of EC and VSMC in an in vitro coculture model exposed to diabetic-like conditions and the effect of vitamin D on cellular pathways that might lead to an inflammatory response. EC and VSMC were isolated from different umbilical cords and stimulated in an in vitro coculture model in a diabetic-like environment and calcitriol for 24 h. Total RNA and protein were extracted from cells and analyzed for the expression of selected inflammatory-related markers. The EC-VSMC coculture in a diabetic-like environment induced the expression of inflammatory markers such as Kruppel-like factors, thioredoxin-interacting protein (TXNIP), IL-6, and IL-8. Addition of vitamin D to the EC-VSMC coculture induced selective changes in the inflammatory response. This model could lead to a better understanding of the interactions between EC and VSMC in the inflammatory processes involved in diabetes and emphasizes the role of vitamin D in the inflammatory response. The use of different donors strengthens the significance of our findings showing that genetic variations do not affect the impact of vitamin D on the expression of inflammatory-related proteins in our model.

Decreasing mitochondrial fission diminishes vascular smooth muscle cell migration and ameliorates intimal hyperplasia

AIMS

Vascular smooth muscle cell (VSMC) migration in response to arterial wall injury is a critical process in the development of intimal hyperplasia. Cell migration is an energy-demanding process that is predicted to require mitochondrial function. Mitochondria are morphologically dynamic, undergoing continuous shape change through fission and fusion. However, the role of mitochondrial morphology in VSMC migration is not well understood. The aim of the study is to understand how mitochondrial fission contributes to VSMC migration and provides its in vivo relevance in the mouse model of intimal hyperplasia.

METHODS AND RESULTS

In primary mouse VSMCs, the chemoattractant PDGF induced mitochondrial shortening through the mitochondrial fission protein dynamin-like protein 1 (DLP1)/Drp1. Perturbation of mitochondrial fission by expressing the dominant-negative mutant DLP1-K38A or by DLP1 silencing greatly decreased PDGF-induced lamellipodia formation and VSMC migration, indicating that mitochondrial fission is an important process in VSMC migration. PDGF induced an augmentation of mitochondrial energetics as well as ROS production, both of which were found to be necessary for VSMC migration. Mechanistically, the inhibition of mitochondrial fission induced an increase of mitochondrial inner membrane proton leak in VSMCs, abrogating the PDGF-induced energetic enhancement and an ROS increase. In an in vivo model of intimal hyperplasia, transgenic mice expressing DLP1-K38A displayed markedly reduced ROS levels and neointima formation in response to femoral artery wire injury.

CONCLUSIONS

Mitochondrial fission is an integral process in cell migration, and controlling mitochondrial fission can limit VSMC migration and the pathological intimal hyperplasia by altering mitochondrial energetics and ROS levels.

Mig-6 gene knockout induces neointimal hyperplasia in the vascular smooth muscle cell

Although advances in vascular interventions can reduce the mortality associated with cardiovascular disease, neointimal hyperplasia remains a clinically significant obstacle limiting the success of current interventions. Identification of signaling pathways involved in migration and proliferation of vascular smooth muscle cells (SMCs) is an important approach for the development of modalities to combat this disease. Herein we investigate the role of an immediate early response gene, mitogen-inducible gene-6 (Mig-6), in the development of neointimal hyperplasia using vascular smooth muscle specific Mig-6 knockout mice. We induced endoluminal injury to one side of femoral artery by balloon dilatation in both Mig-6 knockout and control mice. Four weeks following injury, the artery of Mig-6 knockout mice demonstrated a 5.3-fold increase in the neointima/media ratio compared with control mice (P = 0.04). In addition, Mig-6 knockout vascular SMCs displayed an increase in both cell migration and proliferation compared with wild-type SMCs. Taken together, our data suggest that Mig-6 plays a critical role in the development of atherosclerosis. This finding provides new insight into the development of more effective ways to treat and prevent neointimal hyperplasia, particularly in-stent restenosis after percutaneous vascular intervention.

Association between the hypomethylation of osteopontin and integrin β3 promoters and vascular smooth muscle cell phenotype switching in great saphenous varicose veins

Lower extremity varicose veins are a common condition in vascular surgery and proliferation of vascular smooth muscle cells (VSMCs) in the intima is a significant pathological feature of varicosity. However, the pathogenesis of varicose veins is not fully understood. Osteopontin (OPN) could promote the migration and adhesion of VSMCs through the cell surface receptor integrin β3 and the cooperation of OPN and integrin β3 is involved in many vascular diseases. However, the role of OPN and integrin β3 in varicosity remains unclear. In the current study, we found that the methylation levels in the promoter regions of OPN and integrin β3 genes in the VSMCs of varicose veins are reduced and the protein expression of OPN and integrin β3 are increased, compared with normal veins. Furthermore, it was observed that VSMCs in the neointima of varicose veins were transformed into the synthetic phenotype. Collectively, hypomethylation of the promoter regions for OPN and integrin β3 genes may increase the expression of these genes in varicosity, which is closely related to VSMC phenotype switching. Hypomethylation of the promoter regions for OPN and integrin β3 genes may be a key factor in the pathogenesis of varicosity.

The pigeon (Columba livia) model of spontaneous atherosclerosis

Multiple animal models have been employed to study human atherosclerosis, the principal cause of mortality in the United States. Each model has individual advantages related to specific pathologies. Initiation, the earliest disease phase, is best modeled by the White Carneau (WC-As) pigeon. Atherosclerosis develops spontaneously in the WC-As without either external manipulation or known risk factors. Furthermore, susceptibility is caused by a single gene defect inherited in an autosomal recessive manner. The Show Racer (SR-Ar) pigeon is resistant to atherosclerosis. Breed differences in the biochemistry and metabolism of celiac foci cells have been described. For example, WC-As have lower oxidative metabolism but higher amounts of chondroitin-6-sulfate and nonesterified fatty acids compared with SR-Ar. Gene expression in aortic smooth muscle cells was compared between breeds using representational difference analysis and microarray analysis. Energy metabolism and cellular phenotype were the chief gene expression differences. Glycolysis and synthetic cell types were related to the WC-As but oxidative metabolism and contractile cell types were related to the SR-Ar. Rosiglitazone, a PPARγ agonist, blocked RNA binding motif (RBMS1) expression in WC-As cells. The drug may act through the c-myc oncogene as RBMS1 is a c-myc target. Proteomic tests of aortic smooth muscle cells supported greater glycosylation in the WC-As and a transforming growth factor β effect in SR-Ar. Unoxidized fatty acids build up in WC-As cells because of their metabolic deficiency, ultimately preventing the contractile phenotype in these cells. The single gene responsible for the disease is likely regulatory in nature.

A FAK-Cas-Rac-lamellipodin signaling module transduces extracellular matrix stiffness into mechanosensitive cell cycling

Tissue and extracellular matrix (ECM) stiffness is transduced into intracellular stiffness, signaling, and changes in cellular behavior. Integrins and several of their associated focal adhesion proteins have been implicated in sensing ECM stiffness. We investigated how an initial sensing event is translated into intracellular stiffness and a biologically interpretable signal. We found that a pathway consisting of focal adhesion kinase (FAK), the adaptor protein p130Cas (Cas), and the guanosine triphosphatase Rac selectively transduced ECM stiffness into stable intracellular stiffness, increased the abundance of the cell cycle protein cyclin D1, and promoted S-phase entry. Rac-dependent intracellular stiffening involved its binding partner lamellipodin, a protein that transmits Rac signals to the cytoskeleton during cell migration. Our findings establish that mechanotransduction by a FAK-Cas-Rac-lamellipodin signaling module converts the external information encoded by ECM stiffness into stable intracellular stiffness and mechanosensitive cell cycling. Thus, lamellipodin is important not only in controlling cellular migration but also for regulating the cell cycle in response to mechanical signals.