Significant peri-operative reduction in plasma osteopontin levels after coronary artery by-pass grafting

The Role of Osteopontin in Atherosclerosis and Its Clinical Manifestations (Atherosclerotic Cardiovascular Diseases)-A Narrative Review

Atherosclerotic cardiovascular diseases (ASCVDs) are the most common and severe public health problem nowadays. Osteopontin (OPN) is a multifunctional glycoprotein highly expressed at atherosclerotic plaque, which has emerged as a potential biomarker of ASCVDs. OPN may act as an inflammatory mediator and/or a vascular calcification (VC) mediator, contributing to atherosclerosis progression and eventual plaque destabilization. In this article, we discuss the complex role of OPN in ASCVD pathophysiology, since many in vitro and in vivo experimental data indicate that OPN contributes to macrophage activation and differentiation, monocyte infiltration, vascular smooth muscle cell (VSMC) migration and proliferation and lipid core formation within atherosclerotic plaques. Most but not all studies reported that OPN may inhibit atherosclerotic plaque calcification, making it "vulnerable". Regarding clinical evidence, serum OPN levels may become a biomarker of coronary artery disease (CAD) presence and severity. Significantly higher OPN levels have been found in patients with acute coronary syndromes than those with stable CAD. In limited studies of patients with peripheral artery disease, circulating OPN concentrations may be predictive of future major adverse cardiovascular events. Overall, the current literature search suggests the contribution of OPN to atherosclerosis development and progression, but more robust evidence is required.

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.

Clinical and Molecular Implications of Osteopontin in Heart Failure

The matricellular protein osteopontin modulates cell-matrix interactions during tissue injury and healing. A complex multidomain structure of osteopontin enables it not only to bind diverse cell receptors but also to interact with various partners, including other extracellular matrix proteins, cytokines, and growth factors. Numerous studies have implicated osteopontin in the development and progression of myocardial remodeling in diverse cardiac diseases. Osteopontin influences myocardial remodeling by regulating extracellular matrix production, the activity of matrix metalloproteinases and various growth factors, inflammatory cell recruitment, myofibroblast differentiation, cardiomyocyte apoptosis, and myocardial vascularization. The exploitation of osteopontin loss- and gain-of-function approaches in rodent models provided an opportunity for assessment of the cell- and disease-specific contribution of osteopontin to myocardial remodeling. In this review, we summarize the recent knowledge on osteopontin regulation and its impact on various cardiac diseases, as well as delineate complex disease- and cell-specific roles of osteopontin in cardiac pathologies. We also discuss the current progress of therapeutics targeting osteopontin that may facilitate the development of a novel strategy for heart failure treatment.

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.

The Emerging Role of Bone Markers in Diagnosis and Risk Stratification of Patients With Coronary Artery Disease

Molecules that govern bone metabolism, such as osteoprotegerin (OPG) and osteopontin (OPN), have been isolated from other tissues, including blood vessels. Atherosclerosis and coronary artery disease (CAD) are leading causes of mortality worldwide. Despite novel biochemical and imaging techniques, early detection of CAD is still unsatisfactory. Experimental data indicate that bone turnover markers (BTMs) contribute to the development of atherosclerosis. This finding has sparked interest in their clinical use. This narrative review analyzed information from >50 human studies, which strongly suggest that OPG, OPN, and alkaline phosphatase (ALP) serum concentrations are altered in patients with CAD. Osteoprotegerin seems to be more useful for the detection of early disease, while OPN and ALP are recruited in vessels after the establishment of disease. Osteocalcin may be used as a flow cytometry marker for endothelial progenitor cells and can constitute a marker to monitor response to interventional treatments and risk of restenosis. However, most data derive from observational studies. Incorporation of BTMs in multifactorial computational algorithms could further determine their role in CAD diagnosis and prognosis together with other imaging techniques and biochemical markers.

Impact of valve surgery on serum osteopontin levels in patients with mitral regurgitation

OBJECTIVE

Osteopontin (OPN), a sialoprotein present within atherosclerotic lesions, especially in calcified plaques, is linked to the progression of coronary artery disease and heart failure. We assessed the impact of valve surgery on serum OPN and left ventricular (LV) function in patients with mitral regurgitation (MR).

METHODS

Thirty-two patients with severe MR scheduled for surgery were included in the study. Echocardiography markers were assessed preoperatively and at 3 months following the surgery and matched with the serum OPN levels.

RESULTS

Valve surgery was associated with a reduction of the ejection fraction (EF) from 55.2 ± 6.3 to 48.8 ± 7.1% after surgery, p < 0.001. Following surgery, the OPN level was significantly higher than preoperatively (mean 245, range 36-2,284 ng/ml vs. 76, 6-486 ng/ml, p = 0.007). Preoperative OPN exhibited a slight negative correlation with the EF (r = -0.35, p = 0.04), and a moderate correlation with vena contracta (r = -0.38, p = 0.02). There were no other meaningful correlations between conventional echocardiographic parameters and OPN.

CONCLUSION

Following valve surgery due to severe MR, patients exhibited a decrease in EF and an increase in OPN levels. The assessment of preoperative OPN failed to strongly predict probable LV dysfunction.

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.

Osteopontin and Osteoprotegerin as Potential Biomarkers in Abdominal Aortic Aneurysm before and after Treatment

Aim. Although osteopontin (OPN) and osteoprotegerin (OPG) have been associated with abdominal aortic aneurysms (AAAs), no association of these two biomarkers with AAA surgical or endovascular treatment has been reported. Material and Methods. Seventy-four AAA patients were prospectively selected for open or endovascular repair. All aneurysms were classified (Types A–E) according to aneurysmal extent in CT imaging (EUROSTAR criteria). All patients had preoperative serum OPN and OPG values measurements and 1 week after the procedure. Preoperative and postoperative values were compared with a control group of twenty patients (inguinal hernia repair). Results. Preoperative OPN values in patients with any type of aneurysm were higher than in the control group, while OPG values showed no difference. Postoperative OPN values in AAA patients were higher than in the control group. OPN values increased after open surgery and after EVAR. OPG values increased after open surgery but not after EVAR. There was no difference in OPN/OPG values between EVAR and open surgery postoperatively. Conclusions. OPN values are associated with aneurysm presence but not with aneurysm extent. OPG values are not associated either with aneurysm presence or with aneurysm extent. OPN values increase after AAA repair, independently of the type of repair.