Serum secreted phosphoprotein 1 level is associated with plaque vulnerability in patients with coronary artery disease

Background

Vulnerable plaque was associated with recurrent cardiovascular events. This study was designed to explore predictive biomarkers of vulnerable plaque in patients with coronary artery disease.

Methods

To reveal the phenotype-associated cell type in the development of vulnerable plaque and to identify hub gene for pathological process, we combined single-cell RNA and bulk RNA sequencing datasets of human atherosclerotic plaques using Single-Cell Identification of Subpopulations with Bulk Sample Phenotype Correlation (Scissor) and Weighted gene co-expression network analysis (WGCNA). We also validated our results in an independent cohort of patients by using intravascular ultrasound during coronary angiography.

Results

Macrophages were found to be strongly correlated with plaque vulnerability while vascular smooth muscle cell (VSMC), fibrochondrocyte (FC) and intermediate cell state (ICS) clusters were negatively associated with unstable plaque. Weighted gene co-expression network analysis showed that Secreted Phosphoprotein 1 (SPP1) in the turquoise module was highly correlated with both the gene module and the clinical traits. In a total of 593 patients, serum levels of SPP1 were significantly higher in patients with vulnerable plaques than those with stable plaque (113.21 [73.65 - 147.70] ng/ml versus 71.08 [20.64 - 135.68] ng/ml; P < 0.001). Adjusted multivariate regression analysis revealed that serum SPP1 was an independent determinant of the presence of vulnerable plaque. Receiver operating characteristic curve analysis indicated that the area under the curve was 0.737 (95% CI 0.697 - 0.773; P < 0.001) for adding serum SPP1 in predicting of vulnerable plaques.

Conclusion

Elevated serum SPP1 levels confer an increased risk for plaque vulnerability in patients with coronary artery disease.

Osteopontin Activation and Microcalcification in Venous Grafts Can Be Modulated by Dexamethasone

BACKGROUND

Osteopontin has been implicated in vascular calcification formation and vein graft intimal hyperplasia, and its expression can be triggered by pro-inflammatory activation of cells. The role of osteopontin and the temporal formation of microcalcification in vein grafts is poorly understood with a lack of understanding of the interaction between haemodynamic changes and the activation of osteopontin.

METHODS

We used a porcine model of vein interposition grafts, and human long saphenous veins exposed to ex vivo perfusion, to study the activation of osteopontin using polymerase chain reaction, immunostaining, and 18F-sodium fluoride autoradiography.

RESULTS

The porcine model showed that osteopontin is active in grafts within 1 week following surgery and demonstrated the presence of microcalcification. A brief pretreatment of long saphenous veins with dexamethasone can suppress osteopontin activation. Prolonged culture of veins after exposure to acute arterial haemodynamics resulted in the formation of microcalcification but this was suppressed by pretreatment with dexamethasone. 18F-sodium fluoride uptake was significantly increased as early as 1 week in both models, and the pretreatment of long saphenous veins with dexamethasone was able to abolish its uptake.

CONCLUSIONS

Osteopontin is activated in vein grafts and is associated with microcalcification formation. A brief pretreatment of veins ex vivo with dexamethasone can suppress its activation and associated microcalcification.

Modulation of Smooth Muscle Cell Phenotype for Translation of Tissue-Engineered Vascular Grafts

Translation of small-diameter tissue-engineered vascular grafts (TEVGs) for the treatment of coronary artery disease (CAD) remains an unfulfilled promise. This is largely due to the limited integration of TEVGs into the native vascular wall-a process hampered by the insufficient smooth muscle cell (SMC) infiltration and extracellular matrix deposition, and low vasoactivity. These processes can be promoted through the judicious modulation of the SMC toward a synthetic phenotype to promote remodeling and vascular integration; however, the expression of synthetic markers is often accompanied by a decrease in the expression of contractile proteins. Therefore, techniques that can precisely modulate the SMC phenotypical behavior could have the potential to advance the translation of TEVGs. In this review, we describe the phenotypic diversity of SMCs and the different environmental cues that allow the modulation of SMC gene expression. Furthermore, we describe the emerging biomaterial approaches to modulate the SMC phenotype in TEVG design and discuss the limitations of current techniques. In addition, we found that current studies in tissue engineering limit the analysis of the SMC phenotype to a few markers, which are often the characteristic of early differentiation only. This limited scope has reduced the potential of tissue engineering to modulate the SMC toward specific behaviors and applications. Therefore, we recommend using the techniques presented in this review, in addition to modern single-cell proteomics analysis techniques to comprehensively characterize the phenotypic modulation of SMCs. Expanding the holistic potential of SMC modulation presents a great opportunity to advance the translation of living conduits for CAD therapeutics.

Osteopontin is a key regulator of vascular smooth muscle cell proliferation in the outflow vein of arteriovenous fistulas

OBJECTIVES

Despite advances in the maintenance of arteriovenous fistulas (AVFs), the patency rates remain suboptimal. Most AVFs fail due to outflow vein stenosis; however, the underlying mechanism of AVF stenosis remains unclear. The present study aimed to identify key factors associated with AVF outflow stenosis.

METHODS

We obtained gene expression profiling data for the outflow vein of AVF from three Gene Expression Omnibus database datasets (GSE39488, GSE97377, and GSE116268) and analyzed the common differentially expressed genes (DEGs). We evaluated a common DEG in an aortocaval mouse model and the stenotic outflow veins of AVFs collected from patients. Furthermore, we isolated vascular smooth muscle cells (VSMCs) from the inferior vena cava (IVC) of wild-type (WT) and osteopontin (Opn)-knockout (KO) mice and assessed the proliferation of VSMCs following stimulation with platelet-derived growth factors (PDGFs).

RESULTS

OPN was the only common upregulated DEG among all datasets. OPN was expressed in the medial layer of the outflow vein of AVF in aortocaval mouse models and co-stained with the VSMC marker (α-smooth muscle actin). OPN expression was markedly increased in the VSMCs of stenotic outflow veins of AVF collected from patients undergoing hemodialysis compared to presurgical veins acquired during AVF formation surgery. PDGF-induced VSMC proliferation was significantly increased in the VSMCs isolated from the IVC of WT mice but not in those isolated from the IVC of Opn-KO mice.

CONCLUSIONS

OPN may be a key gene involved in VSMC proliferation in the AVF outflow veins and a therapeutic target to improve the AVF patency rate.

Large animal model of vein grafts intimal hyperplasia: A systematic review

Coronary artery bypass grafting remains the treatment of choice for a large cohort of patients with significant coronary disease. Despite the increased use of arterial grafts, the long saphenous vein remains the most commonly used conduit. Long-term graft patency continues to be the Achilles heel of saphenous vein grafts. This is due to the development of intimal hyperplasia, a chronic inflammatory disease that results in the narrowing and occlusion of a significant number of vein grafts. Research models for intimal hyperplasia are essential for a better understanding of pathophysiological processes of this condition. Large animal models resemble human anatomical structures and have been used as a surrogate to study disease development and prevention over the years. In this paper, we systematically review all published studies that utilized large animal models of vein graft disease with a focus on the type of model and any therapeutic intervention, specifically the use of external stents/mesh.

miR-16-5p Is a Novel Mediator of Venous Smooth Muscle Phenotypic Switching

Vein graft failure after coronary artery bypass grafting (CABG) is primarily caused by intimal hyperplasia, which results from the phenotypic switching of venous smooth muscle cells (SMCs). This study investigates the role and underlying mechanism of miR-16-5p in the phenotypic switching of venous SMCs. In rats, neointimal thickness and area increased over time within 28 days after CABG, as did the time-dependent miR-16-5p downregulation and SMC phenotypic switching. Platelet-derived growth factor-BB-induced miR-16-5p downregulation in HSVSMCs was accompanied by and substantially linked with alterations in phenotypic switching indicators. Furthermore, miR-16-5p overexpression increased SMCs differentiation marker expression while suppressing HSVSMCs proliferation and migration and drastically inhibiting neointimal development in vein grafts. The miR-16-5p inhibited zyxin expression, which was necessary for HSVSMCs phenotypic switching. The miR-16-5p/zyxin axis is a novel, potentially therapeutic target for preventing and treating venous graft intimal hyperplasia.

Plasmatic osteopontin and vascular access dysfunction in hemodialysis patients: a cross-sectional, case-control study (The OSMOSIS Study)

BACKGROUND AND AIMS

Despite close follow-up of patients with native arteriovenous fistulas (AVFs), up to 10% experience thrombosis each year. The OSMOSIS Study (Osteopontin as a Marker of Stenosis) tested the hypothesis that the systemic osteopontin level, a pro-inflammatory mediator related to vascular remodelling and intimal hyperplasia, increases in AVF stenosis, and may be used in clinical surveillance.

METHODS

Our cross-sectional study compared the level of plasmatic osteopontin (pOPN) between patients with a well-functioning AVF (control group) and patients who required revision of their AVF due to stenosis (stenosis group). Blood samples were collected before dialysis (control group) or before intervention (stenosis group) from the AVF arm, and from the opposite arm as a within-subject control. pOPN level was measured by enzyme-linked immunosorbent assay.

RESULTS

A total of 76 patients were included in the study. Baseline characteristics were similar between the groups (mean age, 70 years; men, 63%; AVF duration, 39 months), apart from prevalence of type 2 diabetes (T2D) (control group, 33%; stenosis group, 57%; p = 0.04). pOPN levels were similar between the AVF arm and the contralateral arm (551 ± 42 ng/mL vs. 521 ± 41 ng/mL, respectively, p = 0.11, paired t-test). Patients in the stenosis group displayed a higher pOPN level than patients in the control group (650.2 ± 59.8 ng/mL vs. 460.5 ± 61.2, respectively, p = 0.03; two-way ANOVA). T2D was not identified as an associated factor in a multivariate analysis (p = 0.50).

CONCLUSIONS

The level of pOPN in hemodialysis patients was associated with the presence of AVF stenosis requiring intervention. Thus, its potential as a diagnostic biomarker should be assessed in a vascular access surveillance program.

Osteopontin in Vascular Disease

Inflammatory cytokines are necessary for an acute response to injury and the progressive healing process. However, when this acute response does not resolve and becomes chronic, the same proteins that once promoted healing then contribute to chronic inflammatory pathologies, such as atherosclerosis. OPN (Osteopontin) is a secreted matricellular cytokine that signals through integrin and CD44 receptors, is highly upregulated in acute and chronic inflammatory settings, and has been implicated in physiological and pathophysiologic processes. Evidence from the literature suggests that OPN may fit within the Goldilocks paradigm with respect to cardiovascular disease, where acute increases are protective, attenuate vascular calcification, and promote postischemic neovascularization. In contrast, chronic increases in OPN are clinically associated with an increased risk for a major adverse cardiovascular event, and OPN expression is a strong predictor of cardiovascular disease independent of traditional risk factors. With the recent finding that humans express multiple OPN isoforms as the result of alternative splicing and that these isoforms have distinct biologic functions, future studies are required to determine what OPN isoform(s) are expressed in the setting of vascular disease and what role each of these isoforms plays in vascular disease progression. This review aims to discuss our current understanding of the role(s) of OPN in vascular disease pathologies using evidence from in vitro, animal, and clinical studies. Where possible, we discuss what is known about OPN isoform expression and our understanding of OPN isoform contributions to cardiovascular disease pathologies.

Expression of osteopontin, matrix metalloproteinase-2 and -9 proteins in vascular instability in brain arteriovenous malformation

Background

Matrix metalloproteinase (MMP)-2 and -9 are Osteopontin (OPN) dependent molecules implicated in the destabilization of blood vessels. OPN and MMPs have been studied in brain arteriovenous malformation (BAVM) patients’ tissues and blood samples before intervention. In this study, we compared the serum level of these markers before and after treatment, as well as assessed their protein expressions in BAVM tissues to evaluate their roles in this disease.

Methodology

Serum samples from six BAVM patients and three control subjects were analyzed using enzyme-linked immunoabsorbent assay (ELISA) for OPN. A total of 10 BAVM patients and five control subjects were analyzed using Multiplex ELISA for MMPs. A total of 16 BAVM tissue samples and two normal brain tissue samples were analyzed using immunohistochemistry.

Result

MMP-2 and -9 were significantly higher in the serum of BAVM patients before and after treatment than in control patients. There were no significant differences of OPN and MMP-9 serum level in BAVM patients before and after treatment. MMP-2 showed a significant elevation after the treatment. Expression of OPN, MMP-2 and -9 proteins were seen in endothelial cells, perivascular cells and brain parenchyma of BAVM tissues.

Conclusion

Findings revealed that the level of MMP-2 and -9 in the serum correlated well with the expression in BAVM tissues in several cases. Knockdown studies will be required to determine the relationships and mechanisms of action of these markers in the near future. In addition, studies will be required to investigate the expression of these markers’ potential applications as primary medical therapy targets for BAVM patients.

Stiffness of Aligned Fibers Regulates the Phenotypic Expression of Vascular Smooth Muscle Cells

Electrospun uniaxially aligned ultrafine fibers show great promise in constructing vascular grafts mimicking the anisotropic architecture of native blood vessels. However, understanding how the stiffness of aligned fibers would impose influences on the functionality of vascular cells has yet to be explored. The present study aimed to explore the stiffness effects of electrospun aligned fibrous substrates (AFSs) on phenotypic modulation in vascular smooth muscle cells (SMCs). A stable jet coaxial electrospinning (SJCES) method was employed to generate highly aligned ultrafine fibers of poly(l-lactide- co-caprolactone)/poly(l-lactic acid) (PLCL/PLLA) in shell-core configuration with a remarkably varying stiffness region from 0.09 to 13.18 N/mm. We found that increasing AFS stiffness had no significant influence on the cellular shape and orientation along the fiber direction with the cultured human umbilical artery SMCs (huaSMCs) but inhibited the cell adhesion rate, promoted cell proliferation and migration, and especially enhanced the F-actin fiber assembly in the huaSMCs. Notably, higher fiber stiffness resulted in significant downregulation of contractile markers like alpha-smooth muscle actin (α-SMA), smooth muscle myosin heavy chain, calponin, and desmin, whereas upregulated the gene expression of pathosis-associated osteopontin ( OPN) in the huaSMCs. These results allude to the phenotype of huaSMCs on stiffer AFSs being miserably modulated into a proliferative and pathological state. Consequently, it adversely affected the proliferation and migration behavior of human umbilical vein endothelial cells as well. Moreover, stiffer AFSs also revealed to incur significant upregulation of inflammatory gene expression, such as interleukin-6 ( IL-6), monocyte chemoattractant protein-1 ( MCP-1), and intercellular adhesion molecule-1 ( ICAM-1), in the huaSMCs. This study stresses that although electrospun aligned fibers are capable of modulating native-like oriented cell morphology and even desired phenotype realization or transition, they might not always direct cells into correct functionality. The integrated fiber stiffness underlying is thereby a critical parameter to consider in engineering structurally anisotropic tissue-engineered vascular grafts to ultimately achieve long-term patency.

Differential gene expression patterns in vein regions susceptible versus resistant to neointimal hyperplasia

Arteriovenous hemodialysis graft (AVG) stenosis results in thrombosis and AVG failure, but prevention of stenosis has been unsuccessful due in large part to our limited understanding of the molecular processes involved in neointimal hyperplasia (NH) formation. AVG stenosis develops chiefly as a consequence of highly localized NH formation in the vein-graft anastomosis region. Surprisingly, the vein region just downstream of the vein-graft anastomosis (herein termed proximal vein region) is relatively resistant to NH. We hypothesized that the gene expression profiles of the NH-prone and NH-resistant regions will be different from each other after graft placement, and analysis of their genomic profiles may yield potential therapeutic targets to prevent AVG stenosis. To test this, we evaluated the vein-graft anastomosis (NH-prone) and proximal vein (NH-resistant) regions in a porcine model of AVG stenosis with a porcine microarray. Gene expression changes in these two distinct vein regions, relative to the gene expression in unoperated control veins, were examined at early (5 days) and later (14 days) time points following graft placement. Global genomic changes were much greater in the NH-prone region than in the NH-resistant region at both time points. In the NH-prone region, genes related to regulation of cell proliferation and osteo-/chondrogenic vascular remodeling were most enriched among the significantly upregulated genes, and genes related to smooth muscle phenotype were significantly downregulated. These results provide insights into the spatial and temporal genomic modulation underlying NH formation in AVG and suggest potential therapeutic strategies to prevent and/or limit AVG stenosis.

Osteopontin may be a driver of abdominal aortic aneurysm formation

OBJECTIVE

Previous in vitro and animal studies have suggested that osteopontin (OPN), an inflammatory extracellular matrix protein, is involved in the formation and growth of abdominal aortic aneurysms (AAAs). However, the mechanism by which this occurs continues to be nebulous. The relationship between OPN and inflammation-suppressing lymphocytes present in the human AAA condition was investigated and presented herein.

METHODS

Serum OPN concentrations were measured in healthy, risk factor-matched non-AAA and AAA patients by enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry was used to determine the source of OPN secretion using aortic tissue collected from multiorgan donors and AAA patients undergoing open surgical repair. Vascular smooth muscle cells (VSMCs) were exposed to various inflammatory mediators, and OPN expression was evaluated by quantitative reverse transcriptase-polymerase chain reaction and ELISA. The inflammatory nature of OPN and the aortic wall was determined using a TR1 suppressor cell induction assay as a surrogate and characterized by ELISA and fluorescence-activated cell sorting.

RESULTS

OPN was found to be elevated in both the plasma and aortic homogenate of AAA patients compared with controls. On immunohistochemistry, OPN localized to the tunica media of the diseased aorta but was minimally expressed in healthy aorta. In vitro, cigarette smoke extract was the most potent stimulator of OPN secretion by VSMCs and increased both messenger RNA and supernatant concentrations. OPN demonstrated an ability to inhibit the induction of interleukin 10-secreting TR1 lymphocytes, a depleted population in the AAA patient, from naive precursors. Last, neutralizing receptor targets of OPN in the setting of AAA homogenate coincubation abrogated the inhibition of TR1 induction.

CONCLUSIONS

OPN, secreted by the VSMCs of the tunica media, is elevated in the circulating plasma and aortic wall of patients with AAA. It can inhibit the induction of the TR1 suppressor cell, leading to an overall proinflammatory state contributing to progressive aortic wall breakdown and dilation.

High expression of ubiquitin-specific peptidase 39 is associated with the development of vascular remodeling

Vascular remodeling is the primary cause underlying the failure of angioplasty surgeries, including vascular stenting, transplant vasculopathy and vein grafts. Multiple restenosis‑associated proteins and genes have been identified to account for this. In the present study, the functions of ubiquitin‑specific peptidase 39 (USP39) were investigated in the context of two vascular remodeling models (a mouse common carotid artery ligation and a pig bilateral saphenous vein‑carotid artery interposition graft). USP39 has previously been observed to be upregulated in ligated arteries, and this result was confirmed in the pig vein graft model. In addition, Transwell assay results demonstrated that vascular smooth muscle cell (VSMC) migration was suppressed by lentiviral vector‑mediated downregulation of USP39 and enhanced by upregulation of USP39. Furthermore, knockdown of USP39 inhibited VSMC cell proliferation and the expression of cyclin D1 and cyclin‑dependent kinase 4, as analyzed via cell counting, MTT assay and western blotting. These results suggest that USP39 may represent a novel therapeutic target for treating vascular injury and preventing vein-graft failure.

Osteopontin - a multi-modal marker and mediator in atherosclerotic vascular disease

Atherosclerosis is a chronic inflammatory process of the vessel wall with systemic correlates. It is now well established that patients' outcome is tightly linked to atherosclerotic plaque stability, potentially more so than to the mere plaque size. Osteopontin (OPN) is an integrin-binding ligand, N-linked glycoprotein, which was recognized as a significant participant in the atherosclerotic inflammatory milieu. Evidence from several genetic mouse models suggests that OPN is an enhancer of atherosclerosis. This may be mediated by its capacity to enhance inflammation in the atherosclerotic plaque. Interestingly, OPN may also possess potentially protective vascular effects, such as attenuation of vascular calcification. In humans circulating levels of OPN were found to be independently associated with the severity of coronary atherosclerosis. Moreover, several studies report that high plasma OPN levels were associated with increased risk for major adverse cardiac events. This review aims to critically assess current understanding of the role of OPN in the atherosclerotic process, from animal models to clinical practice. Specific focus is given to evaluating whether OPN could serve as a marker for monitoring coronary atherosclerosis severity, and in parallel, assess the evidence for its role as a mediator in the pathogenic pathways leading to atherosclerotic vascular disease.

Bone morphogenic protein-4 contributes to venous endothelial dysfunction in patients with diabetes undergoing coronary revascularization

BACKGROUND

Hyperglycemia-induced venous endothelial dysfunction accelerates the progression of vein graft failure in patients with diabetes undergoing surgical coronary revascularization. Recent studies suggest the importance of bone morphogenic protein-4 (BMP4)-induced arterial endothelial dysfunction in the development of hypertension and atherosclerosis. The present study investigated the potential role of BMP4 in the pathogenesis of venous endothelial dysfunction in the setting of diabetes.

METHODS

Segments of saphenous vein from pigs and from patients with diabetes or patients without diabetes, as well as human umbilical venous endothelial cells (HUVECs), were used. The changes of BMP4 expression in veins from patients and in HUVECs cultured under hyperglycemic conditions were evaluated by Western blot assay. The effects of BMP4 on the production of reactive oxygen species (ROS) and endothelium-dependent venous relaxation were assessed by using dihydroethidium fluorescence and isometric tension measurements, respectively.

RESULTS

The impaired venous endothelium-dependent relaxations (2.9%±4.8% versus control group 74.1%±10%; p<0.01) accompanied by markedly increased BMP4 expression were observed in the diabetic group. The level of BMP4 expression in HUVECs treated with high levels of glucose were elevated in a glucose concentration-dependent manner. Ex vivo treatment with the BMP4 antagonist noggin significantly improved endothelium-dependent relaxations and inhibited accumulation of ROS in saphenous veins from patients with diabetes. Noggin treatment had no effect on the venous endothelium-dependent relaxations in individuals without diabetes. Meanwhile, BMP4 inhibited acetylcholine-induced relaxation (control group, 90%±7.1% versus BMP4-treated group, 52%±12.6%; p<0.05) and enhanced ROS production in porcine saphenous veins. Such harmful effects were again reversed by noggin.

CONCLUSIONS

The increased BMP4 expression and related ROS overproduction may play an important role in the development of hyperglycemia-induced venous endothelial dysfunction.

External support in preventing vein graft failure

Saphenous vein remains a widely used conduit in coronary surgery. However, the long-term success of surgical myocardial revascularization is largely limited by the development of neointimal hyperplasia and superimposed atherosclerosis in vein grafts. Although strategies for preventing vein graft failure have been constantly explored, few therapeutic interventions to date have shown sustained benefits in the clinical setting. The application of external support has emerged as a promising strategy for modulating the overall biomechanical responses in venous wall. Nonetheless, clinical translation of this intervention has been formerly challenged, primarily due to several technique limitations. The purpose of the current review is to summarize the possible mechanisms involved in the external support strategy for preventing vein graft failure. Furthermore, several previously tested biomaterials and delivery techniques are also highlighted.