Expression of fibromodulin in carotid atherosclerotic plaques is associated with diabetes and cerebrovascular events.

The small leucine-rich proteoglycans fibromodulin and lumican are functionally related extracellular matrix proteins involved in the regulation of collagen fiber formation. Fibromodulin-deficient apolipoprotein E-null mice have decreased vascular retention of lipids and reduced development of atherosclerosis suggesting that fibromodulin may influence the disease process. The aim of the present study was to investigate if fibromodulin and lumican are expressed in human carotid plaques and to determine if their expression is associated with the occurrence of preoperative symptoms and with risk for postoperative cardiovascular events

The Novel Collagen Matrikine, Endotrophin, is Associated with Mortality and Cardiovascular Events in Patients with Atherosclerosis

Background: Rupture of atherosclerotic plaques is the major cause of acute cardiovascular events. The biomarker PRO-C6 measuring Endotrophin, a matrikine of collagen type VI, may provide valuable information detecting subjects in need of intensified strategies for secondary prevention. Objective: In this study, we evaluate endotrophin in human atherosclerotic plaques and circulating levels of PRO-C6 in patients with atherosclerosis, to determine the predictive potential of the biomarker. Methods: Sections from the stenotic human carotid plaques were stained with the PRO-C6 antibody. PRO-C6 was measured in serum of patients enrolled in the Carotid Plaque Imagining Project (CPIP) (discovery cohort, n = 577) and the innovative medicines initiative surrogate markers for micro- and macrovascular hard end-points for innovative diabetes tools (IMI-SUMMIT, validation cohort, n = 1,378). Median follow-up was 43 months. Kaplan–Meier curves and log-rank tests were performed in the discovery cohort. Cox proportional hazard regression analysis (HR with 95% CI) was used in the discovery cohort and binary logistic regression (OR with 95% CI) in the validation cohort. Results: PRO-C6 was localized in the core and shoulder of the atherosclerotic plaque. In the discovery cohort, PRO-C6 independently predicted future cardiovascular events (HR 1.089 [95% CI 1.019 −1.164], p = 0.01), cardiovascular death (HR 1.118 [95% CI 1.008 −1.241], p = 0.04) and all-cause death (HR 1.087 [95% CI 1.008 −1.172], p = 0.03). In the validation cohort, PRO-C6 predicted future cardiovascular events (OR 1.063 [95% CI 1.011 −1.117], p = 0.017). Conclusion: PRO-C6 is present in the atherosclerotic plaque and associated with future cardiovascular events, cardiovascular death and all-cause mortality in two large prospective cohorts

Extracellular matrix in atherosclerotic plaques: its role in plaque stability

Atherosclerosis is a systemic disease affecting the large arteries caused by the accumulation of lipids in the vessel wall. Cardiovascular disease due to atherosclerosis is today the most common cause of death globally through its end consequences: myocardial infarctions and stroke. The extracellular matrix (ECM) is a network of structural fibrous proteins, proteoglycans and glycoproteins. ECM proteins are involved in all steps of the disease progression from the initial lipoprotein accumulation to the failure of the fibrous cap causing clinical symptoms. It is therefore attractive to focus on these proteins to find novel ways of treating atherosclerosis. The basement membrane is a sheet like structure composed of ECM proteins underlying the endothelial cells and surrounding smooth muscle cells. The two major proteins in the basement membrane are the network forming collagen type IV and laminin. In the clinical context there is a great need of finding the patients that are at high risk of suffering from impending cardiovascular events, thereby qualifiying them for a more intensive treatement. The ECM is continuously being degraded by matrix metalloproteinases (MMPs) and synthesized mostly by smooth muscle cells. The balance between these two processes are important for tissue homeostasis and stability in the atherosclerotic plaque. The purpose of this thesis was to explore the role of different parts of the ECM and their association to plaque vulnerability. We measured the the small leucin rich proteogylcans (SLRPs), neoepitopes of degraded ECM proteins and the three isoforms of transforming growth factor-β in human atherosclerotic plaque tissue. Plaque sections, homogenate and blood samples were obtained from the Carotid Plaque Imaging Project (CPIP). In this thesis three different SLRPs, fibromodulin lumican and mimecan were examined by immunohistochemistry and their association to plaque components, vulnerable plaque features and their association with future cardiovascular events were explored. We also explored the association of serum levels of the degraded basement membrane proteins collagen typ IV (C4M), laminin (LG1M) and collagen typ I (C1M) and the risk of suffering from future cardiovascular events and death. Finally, we assessed the three isoforms of TGF-β (TGF-β1, TGF-β2 and TGF-β3) in 223 plaques, to investigate if they were associated to a specific plaque phenotype and future cardiovascular events. Fibromodulin, lumican and mimecan were all expressed in the atherosclerotic plaque tissue and fibromodulin plaque area was greated in symptomatic and diabetic plaques and correlated to plaque levels of lipids and proinflammatory cytokines. Mimecan plaque area was associated with a vulnerable plaque phenotype, the proinflammatory cytokine MCP-1 and matrix degrading proteinase MMP-9. Larger plaques areas of mimecan were also associated with an increased risk for cardiovascular death. All three isoforms of TGF-β were detected in the human plaque tissue although TGF-β2 was present in much higher levels. TGF-β2 was also found to correlate to features of plaque stability and tissue remodelling. C4M, LG1M and C1M were in varying degrees independently associated with all-cause mortality, cardiovascular death and cardiovascular events.The regulation of ECM synthesis and degradation harbour the potential of novel and beneficial reparatory mechanisms that awaits to be discovered. The findings in this thesis may lead to the discovery of new mechanisms involved in vascular repair

Carotid Plaque Morphology is Similar in Patients with Reduced and Normal Renal Function

Background: Chronic Kidney Disease (CKD) is associated with an increased risk for cardiovascular events such as stroke. However, it is still unclear if decreased kidney function is associated with a vulnerable atherosclerotic plaque phenotype. To explore if renal function was associated with carotid plaque vulnerability we analyzed carotid plaques obtained at surgery from the Carotid Plaque Imaging Project (CPIP). Methods: Patients were enrolled through the CPIP cohort. The indication for surgery was plaques with stenosis >70%, associated with ipsilateral symptoms or plaques with stenosis >80% not associated with symptoms. Transversal sections from the most stenotic plaque region were analyzed for connective tissue, calcium, lipids, macrophages, intraplaque hemorrhage, and smooth muscle cells. Homogenates were analyzed for collagen and elastin. Results: Carotid endarterectomy specimens from 379 patients were obtained. The median GFR was 73 ml/min/1.73 m2. Plaque characteristics showed no significant association with eGFR, neither when eGFR was divided in CKD groups nor when eGFR was handled as a continuous variable and adjusting for other known risk factors (ie, age, diabetes, hypertension, and smoking). Conclusions: The higher risk of cardiovascular disease such as stroke in CKD is not associated with increased plaque vulnerability and other factors have to be sought

Plaque vulnerability index predicts cardiovascular events : A histological study of an endarterectomy cohort

BACKGROUND: The balance between stabilizing and destabilizing atherosclerotic plaque components is used in experimental studies and in imaging studies to identify rupture prone plaques. However, we lack the evidence that this balance predicts future cardiovascular events. Here we explore whether a calculated histological ratio, referred to as vulnerability index (VI), can predict patients at higher risk to suffer from future cardiovascular events. METHODS AND RESULTS: Carotid plaques and clinical information from 194 patients were studied. Tissue sections were used for histological analysis to calculate the VI (CD68 [cluster of differentiation 68], alpha-actin, Oil red O, Movat pentachrome, and glycophorin A). Postoperative cardiovascular events were identified through the Swedish National Inpatient Health Register (2005-2013). During the follow-up (60 months) 45 postoperative cardiovascular events were registered. Patients with a plaque VI in the fourth quartile compared with the first to third quartiles had significantly higher risk to suffer from a future cardiovascular event (P=0.0002). The VI was an independent predictor and none of the 5 histological variables analyzed separately predicted events. In the 13 patients who underwent bilateral carotid endarterectomy, the VI of the right plaque correlated with the VI of the left plaque and vice versa (r=0.7, P=0.01). CONCLUSIONS: Our findings demonstrate that subjects with a high plaque VI have an increased risk of future cardiovascular events, independently of symptoms and other known cardiovascular risk factors. This strongly supports that techniques which image such plaques can facilitate risk stratification for subjects in need of more intense treatment

Dystrophin deficiency reduces atherosclerotic plaque development in ApoE-null mice.

Dystrophin of the dystrophin-glycoprotein complex connects the actin cytoskeleton to basement membranes and loss of dystrophin results in Duchenne muscular dystrophy. We have previously shown injury-induced neointima formation of the carotid artery in mice with the mdx mutation (causing dystrophin deficiency) to be increased. To investigate the role of dystrophin in intimal recruitment of smooth muscle cells (SMCs) that maintains plaque stability in atherosclerosis we applied a shear stress-modifying cast around the carotid artery of apolipoprotein E (ApoE)-null mice with and without the mdx mutation. The cast induces formation of atherosclerotic plaques of inflammatory and SMC-rich/fibrous phenotypes in regions of low and oscillatory shear stress, respectively. Unexpectedly, presence of the mdx mutation markedly reduced the development of the inflammatory low shear stress plaques. Further characterization of the low shear stress plaques in ApoE-null mdx mice demonstrated reduced infiltration of CD3(+) T cells, less laminin and a higher SMC content. ApoE-null mdx mice were also found to have a reduced fraction of CD3(+) T cells in the spleen and lower levels of cytokines and monocytes in the circulation. The present study is the first to demonstrate a role for dystrophin in atherosclerosis and unexpectedly shows that this primarily involves immune cells

Markers of basement membrane remodeling are associated with higher mortality in patients with known atherosclerosis

Background-Patients with atherosclerosis have a high risk of cardiovascular events and death. Atherosclerosis is characterized by accumulation of lipids, cells and extracellular matrix proteins in the intima. We hypothesized that dysregulated remodeling of the basement membrane proteins may be associated with clinical outcomes in patients with atherosclerosis. Methods and Results-Neoepitope fragments of collagen type IV (C4M) and laminin (LG1M) were assessed by ELISAs in serum from 787 endarterectomy patients. Matrix metalloproteinases were measured using proximity extension assay and correlated to C4M and LG1M levels using Spearman correlations. A total of 473 patients were followed up for 6 years using national registers, medical charts, and telephone interviews. The incidence of cardiovascular events, cardiovascular mortality, and all-cause mortality were associated to levels of C4M and LG1M using Kaplan–Meier curves and Cox regression analyses. A total of 101 patients had cardiovascular events, 39 died of cardiovascular mortality, and 64 patients died from all-cause mortality. C4M levels were increased in patients with symptomatic carotid atherosclerotic disease before surgery (P=0.048). High C4M and LG1M levels were associated with increased risk of all-cause mortality (P=0.020 and 0.031, respectively) and predicted all-cause death together with glomerular filtration rate and diabetes mellitus. Conclusions-High LG1M and C4M levels were associated with all-cause mortality, together with glomerular filtration rate and diabetes mellitus. These novel biomarkers need further evaluation but might be tools to identify high-risk patients

Increased proteolytic cleavage of osteoglycin is associated with a stable plaque phenotype and lower risk of cardiovascular events

Background and aims: Extracellular matrix (ECM) remodeling is one of the key components in the formation of vulnerable atherosclerotic plaques and cardiovascular events. We recently showed that the full-length ECM-proteoglycan osteoglycin was associated with plaque vulnerability and future cardiovascular events. In the present study, we aimed to investigate the association of cleaved osteoglycin with plaque phenotype. Methods: Two-hundred human carotid plaques were analyzed by immunohistochemistry. Cleaved osteoglycin and active caspase-3 were assessed by ELISA. ECM components (collagen, elastin and glycosaminoglycans) were assessed by colorimetric assays in plaque tissue homogenates. Matrix metalloproteinases (MMPs) were assessed using Milliplex. MMP-cleavage of osteoglycin and its effect on apoptosis were studied in vitro. Cardiovascular events were recorded during follow-up using national registries. Results: Plaque levels of cleaved osteoglycin were significantly higher in asymptomatic plaques and correlated to α-actin plaque area, collagen, elastin and inversely to lipids, active. caspase-3 and a histological vulnerability index. Cleaved osteoglycin correlated to several MMPs, especially MMP-12, which was also shown to cleave osteoglycin in vitro. In vitro cleavage of osteoglycin was also associated with less smooth muscle cell apoptosis. Patients with high plaque levels of cleaved osteoglycin had a significantly lower risk to suffer from future cardiovascular events. Conclusions: The current study shows that cleaved osteoglycin is associated with a stable plaque phenotype and lower risk for future cardiovascular events. Potentially due to reduced cell apoptosis and ability to retain LDL. These results indicate that targeting the cleavage of osteoglycin may be a potential therapeutic strategy to stabilize plaques

The proteoglycan mimecan is associated with carotid plaque vulnerability and increased risk of future cardiovascular death

Background and aims: A vulnerable plaque is an atherosclerotic plaque that is rupture-prone with a higher risk to cause cardiovascular symptoms such as myocardial infarction or stroke. Mimecan or osteoglycin is a small leucine-rich proteoglycan, important for collagen fibrillogenesis, that has been implicated in atherosclerotic disease, yet the role of mimecan in human atherosclerotic disease remains unknown. Methods: 196 human atherosclerotic carotid plaques were immunostained for mimecan. Smooth muscle cells, macrophages and intraplaque haemorrhage were also measured with immunohistochemistry. Neutral lipids were stained with Oil Red O and calcium deposits were quantified. Plaque homogenate levels of MCP-1, IL-6 and MIP-1β were measured using a Proximity Extension Assay and MMP-9 levels were measured using Mesoscale. Glycosaminoglycans, collagen and elastin were assessed by colorimetric assays and TGF-β1, β2 and β3 were measured using a multiplex assay. Mimecan gene expression in THP-1 derived macrophages was quantified by qPCR and protein expression in vitro was visualized with immunofluorescence. Cardiovascular events were registered using medical charts and national registers during follow-up. Results: Mimecan correlated positively with plaque area of lipids, macrophages, intraplaque haemorrhage and inversely with smooth muscle cell staining. Mimecan also correlated positively with plaque levels of MMP-9 and MCP-1. Mimecan was upregulated in THP-1 derived macrophages upon stimulation with MCP-1. Patients with high levels of mimecan (above median) had higher risk for cardiovascular death. Conclusions: This study indicates that mimecan is associated with a vulnerable plaque phenotype, possibly regulated by plaque inflammation. In line, plaque levels of mimecan independently predict future cardiovascular death

Reduced oxidized LDL in T2D plaques is associated with a greater statin usage but not with future cardiovascular events

BACKGROUND: Type 2 diabetes (T2D) patients are at a greater risk of cardiovascular events due to aggravated atherosclerosis. Oxidized LDL (oxLDL) has been shown to be increased in T2D plaques and suggested to contribute to plaque ruptures. Despite intensified statin treatment during the last decade the higher risk for events remains. Here, we explored if intensified statin treatment was associated with reduced oxLDL in T2D plaques and if oxLDL predicts cardiovascular events, to elucidate whether further plaque oxLDL reduction would be a promising therapeutic target. METHODS: Carotid plaque OxLDL levels and plasma lipoproteins were assessed in 200 patients. Plaque oxLDL was located by immunohistochemistry. Plaque cytokines, cells and scavenger receptor gene expression were quantified by Luminex, immunohistochemistry and RNA sequencing, respectively. Clinical information and events during follow-up were obtained from national registers. RESULTS: Plaque oxLDL levels correlated with markers of inflammatory activity, endothelial activation and plasma LDL cholesterol (r = 0.22-0.32 and p ≤ 0.01 for all). T2D individuals exhibited lower plaque levels of oxLDL, sLOX-1(a marker of endothelial activation) and plasma LDL cholesterol (p = 0.001, p = 0.006 and p = 0.009). No increased gene expression of scavenger receptors was identified in T2D plaques. The lower oxLDL content in T2D plaques was associated with a greater statin usage (p = 0.026). Supporting this, a linear regression model showed that statin treatment was the factor with the strongest association to plaque oxLDL and plasma LDL cholesterol (p < 0.001 for both). However, patients with T2D more frequently suffered from symptoms and yet plaque levels of oxLDL did not predict cardiovascular events in T2D (findings are summarized in Fig. 1a). CONCLUSIONS: This study points out the importance of statin treatment in affecting plaque biology in T2D. It also implies that other biological components, beyond oxLDL, need to be identified and targeted to further reduce the risk of events among T2D patients receiving statin treatment