Osteopontin (OPN) improves risk stratification in pulmonary hypertension (PH)

Osteopontin in Pulmonary Hypertension

Pulmonary hypertension (PH) is a pathological condition with multifactorial etiology, which is characterized by elevated pulmonary arterial pressure and pulmonary vascular remodeling. The underlying pathogenetic mechanisms remain poorly understood. Accumulating clinical evidence suggests that circulating osteopontin may serve as a biomarker of PH progression, severity, and prognosis, as well as an indicator of maladaptive right ventricular remodeling and dysfunction. Moreover, preclinical studies in rodent models have implicated osteopontin in PH pathogenesis. Osteopontin modulates a plethora of cellular processes within the pulmonary vasculature, including cell proliferation, migration, apoptosis, extracellular matrix synthesis, and inflammation via binding to various receptors such as integrins and CD44. In this article, we provide a comprehensive overview of the current understanding of osteopontin regulation and its impact on pulmonary vascular remodeling, as well as consider research issues required for the development of therapeutics targeting osteopontin as a potential strategy for the management of PH.

Proteomics and phosphoproteomics analysis of vitreous in idiopathic epiretinal membrane patients

PURPOSE

The purpose of the present study was to characterize the idiopathic epiretinal membrane (iERM) through proteomics and phosphoproteomics analysis to facilitate the diagnosis and treatment of iERM.

EXPERIMENTAL DESIGN

The vitreous of 25 patients with an iERM and 15 patients with an idiopathic macular hole were analyzed by proteomic and phosphoproteomic analysis based on tandem mass tag. PRM was used to verify the differential proteins.

RESULTS

Proteomic analysis identified a total of 878 proteins, including 50 differential proteins. Tenascin-C, galectin-3-binding protein, glucose-6-phosphate isomerase, neuroserpin, collagen alpha-1(XI) chain, and collagen alpha-1(II) chain were verified to be upregulated in iERM by PRM. Phosphoproteomic analysis identified a total of 401 phosphorylation sites on 213 proteins, including 27 differential phosphorylation sites on 24 proteins. Mitogen-activated protein kinase-activated protein kinase (MAPKAPK)3 and MAPKAPK5 were predicted as the major kinases in the vitreous of iERM. Twenty-six of the differential proteins and phosphorylated proteins may be closely related to fibrosis in iERM.

CONCLUSION AND CLINICAL RELEVANCE

Our results indicated the potential biomarkers or therapeutic targets for iERM, provided key kinases that may be involved in iERM. Fibrosis plays an essential role in iERM, and further exploration of related differential proteins has important clinical significance.

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.

An Overview of Circulating Pulmonary Arterial Hypertension Biomarkers

Pulmonary arterial hypertension (PAH), also known as Group 1 Pulmonary Hypertension (PH), is a PH subset characterized by pulmonary vascular remodeling and pulmonary arterial obstruction. PAH has an estimated incidence of 15-50 people per million in the United States and Europe, and is associated with high mortality and morbidity, with patients' survival time after diagnosis being only 2.8 years. According to current guidelines, right heart catheterization is the gold standard for diagnostic and prognostic evaluation of PAH patients. However, this technique is highly invasive, so it is not used in routine clinical practice or patient follow-up. Thereby, it is essential to find new non-invasive strategies for evaluating disease progression. Biomarkers can be an effective solution for determining PAH patient prognosis and response to therapy, and aiding in diagnostic efforts, so long as their detection is non-invasive, easy, and objective. This review aims to clarify and describe some of the potential new candidates as circulating biomarkers of PAH.

Post-translational regulation and proteolytic activity of the metalloproteinase ADAMTS8

A disintegrin-like and metalloprotease domain with thrombospondin type 1 motifs (ADAMTS)8 is a secreted protease, which was recently implicated in pathogenesis of pulmonary arterial hypertension (PAH). However, the substrate repertoire of ADAMTS8 and regulation of its activity are incompletely understood. Although considered a proteoglycanase because of high sequence similarity and close phylogenetic relationship to the proteoglycan-degrading proteases ADAMTS1, 4, 5, and 15, as well as tight genetic linkage with ADAMTS15 on human chromosome 11, its aggrecanase activity was reportedly weak. Several post-translational factors are known to regulate ADAMTS proteases such as autolysis, inhibition by endogenous inhibitors, and receptor-mediated endocytosis, but their impacts on ADAMTS8 are unknown. Here, we show that ADAMTS8 undergoes autolysis at six different sites within its spacer domain. We also found that in contrast to ADAMTS4 and 5, ADAMTS8 levels were not regulated through low-density lipoprotein receptor-related protein 1 (LRP1)-mediated endocytosis. Additionally, ADAMTS8 lacked significant activity against the proteoglycans aggrecan, versican, and biglycan. Instead, we found that ADAMTS8 cleaved osteopontin, a phosphoprotein whose expression is upregulated in PAH. Multiple ADAMTS8 cleavage sites were identified using liquid chromatography–tandem mass spectrometry. Osteopontin cleavage by ADAMTS8 was efficiently inhibited by TIMP-3, an endogenous inhibitor of ADAMTS1, 4, and 5, as well as by TIMP-2, which has no previously reported inhibitory activity against other ADAMTS proteases. These differences in post-translational regulation and substrate repertoire differentiate ADAMTS8 from other family members and may help to elucidate its role in PAH.

Osteopontin and galectin-3 as biomarkers of maladaptive right ventricular remodeling in pulmonary hypertension

Aim: This study assessed the utility of osteopontin (OPN) and galectin-3 (Gal-3) as biomarkers of maladaptive right ventricular remodeling in pulmonary hypertension (PH). Materials & methods: We examined plasma levels of OPN and Gal-3 in patients with PH (n = 62), dilated cardiomyopathy (n = 34), left ventricular hypertrophy (LVH; n = 47), and controls without right ventricle (RV) or LV abnormalities (n = 38). Results: OPN and Gal-3 levels were higher in PH, dilated cardiomyopathy and LVH than in the controls. OPN concentrations in PH patients with maladaptive RV were significantly higher than in those with adaptive RV. Gal-3 did not differentiate between adaptive and maladaptive RV remodeling in PH. OPN and Gal-3 levels did not correlate with parameters of LV remodeling. Conclusion: OPN is a potential biomarker of RV maladaptation.

Comorbidity in idiopathic pulmonary fibrosis - what can biomarkers tell us?

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive parenchymal scarring, leading to dyspnoea, respiratory failure and premature death. Although IPF is confined to the lungs, the importance of IPF comorbidities such as pulmonary hypertension and ischaemic heart disease, lung cancer, emphysema/chronic obstructive pulmonary disease, gastroesophageal reflux, sleep apnoea and depression has been increasingly recognized. These comorbidities may be associated with increased mortality and significant loss of quality of life, so their identification and management are vital. The development of good-quality biomarkers could lead to numerous gains in the management of these patients. Biomarkers can be used for the identification of predisposed individuals, early diagnosis, assessment of prognosis, selection of best treatment and assessment of response to treatment. However, the role of biomarkers for IPF comorbidities is still quite limited, and mostly based on evidence coming from populations without IPF. The future development of new biomarker studies could be informed by those that have been studied independently for each of these conditions. For now, clinicians should be mostly attentive to clinical manifestations of IPF comorbidities, and use validated diagnostic methods for diagnosis. As research on biomarkers of most common diseases continues, it is expected that useful biomarkers are developed for these diseases and then validated for IPF populations. The reviews of this paper are available via the supplemental material section.

Role of Osteopontin as a Potential Biomarker of Pulmonary Arterial Hypertension in Patients with Systemic Sclerosis and Other Connective Tissue Diseases (CTDs)

Pulmonary arterial hypertension (PAH) is a severe complication of connective tissue diseases (CTD). Its early diagnosis is essential to start effective treatment. In the present paper, we aimed to evaluate the role of plasma osteopontin (OPN) as a candidate biomarker of PAH in a cohort of CTD patients. OPN is a pleiotropic protein involved in inflammation and fibrogenesis and, therefore, potentially promising in this specific clinical context. We performed a cross-sectional observational study on a cohort of 113 CTD patients (females N = 101, 89.4%) affected by systemic sclerosis N = 88 (77.9%), mixed connective tissue disease N = 10 (8.8%), overlap syndrome N = 10 (8.8%) or undifferentiated connective tissue disease N = 5 (4.4%). CTD-PAH patients showed significantly higher OPN plasma values than patients with CTD alone (241.0 (188.8–387.2) vs. 200.7 (133.5–281.6) ng/mL; p = 0.03). Although OPN levels were directly correlated with age and inversely with glomerular filtration rate, they remained associated with PAH at multivariate analysis. In conclusion, OPN was significantly associated with PAH among patients with CTD, suggesting it may have a role as a non-invasive disease biomarker of PAH.

Novel Molecular Mechanisms of Pulmonary Hypertension: A Search for Biomarkers and Novel Drug Targets-From Bench to Bed Site

Pulmonary hypertension (PH) is defined as increased mean pulmonary artery pressure (mPAP) above 25 mmHg, measured at rest by right heart catheterization. The exact global prevalence of PH is difficult to estimate, mainly due to the complex aetiology, and its spread may be underestimated. To date, numerous studies on the aetiology and pathophysiology of PH at molecular level were conducted. Simultaneously, some clinical studies have shown potential usefulness of well-known and widely recognized cardiovascular biomarkers, but their potential clinical usefulness in diagnosis and management of PH is poor due to their low specificity accompanied with numerous other cardiovascular comorbidities of PH subjects. On the other hand, a large body of basic research-based studies provides us with novel molecular pathomechanisms, biomarkers, and drug targets, according to the evidence-based medicine principles. Unfortunately, the simple implementation of these results to clinical practice is impossible due to a large heterogeneity of the PH pathophysiology, where the clinical symptoms constitute only a common denominator and a final result of numerous crosstalking metabolic pathways. Therefore, future studies, based mostly on translational medicine, are needed in order to both organize better the pathophysiological classification of various forms of PH and define precisely the optimal diagnostic markers and therapeutic targets in particular forms of PH. This review paper summarizes the current state of the art regarding the molecular background of PH with respect to its current classification. Novel therapeutic strategies and potential biomarkers are discussed with respect to their limitations in use in common clinical practice.

Akt/eNOS and MAPK signaling pathways mediated the phenotypic switching of thoracic aorta vascular smooth muscle cells in aging/hypertensive rats

Considerable evidence demonstrates that phenotypic switching of vascular smooth muscle cells (VSMCs) is influenced by aging and hypertension. During phenotypic switching, VSMCs undergo a switch to a proliferative and migratory phenotype, with this switch being a common pathology in cardiovascular diseases. The aim of this study was to explore the joint influence of age and hypertension on thoracic aortic smooth muscle phenotypic switching and the balance of Akt and mitogen-activated protein kinase (MAPK) signaling during this switch. Different ages of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were used to establish hypertension and aging models. The phenotypic state was determined by detecting the marker proteins alpha-SM-actin, calponin, and osteopontin (OPN) via immunohistochemical staining and Western blot. Signaling proteins associated with the Akt and MAPK pathways were detected in rat thoracic aorta using Western blot. Both aging and hypertension caused a decrease in contractile (differentiated) phenotype markers (alpha-SM-actin and calponin), while the synthetic (proliferative or de-differentiated) phenotype maker was elevated (OPN). When combining hypertension and aging, this effect was enhanced, with Akt signaling decreased, while MAPK signaling was increased. These results suggested that VSMCs phenotype switching is modulated by a balance between Akt and MAPK signaling in the process of aging and hypertension.

Role of Biomarkers in the Diagnosis, Risk Assessment, and Management of Pulmonary Hypertension

Pulmonary hypertension is a severe and debilitating disease with no definite cure, and the domain of targeted therapies is a promising field for better management of this severe condition. The disease comprises pulmonary arterial remodeling, hypoxia, endothelial dysfunction, and inflammation, with subsequent organ damage including right heart and liver dysfunction. Biomarkers have a valuable role at different levels of the disease, from diagnosis to risk assessment and management, in order to decrease the burden of the disease in terms of both morbidity and mortality.

Persistently elevated osteopontin serum levels predict mortality in critically ill patients

Introduction

Inflammatory, autoimmune and metabolic disorders have been associated with alterations in osteopontin (OPN) serum levels. Furthermore, elevated serum levels of OPN were reported from a small cohort of patients with sepsis. We therefore analyzed OPN serum concentrations in a large cohort of critically ill medical patients.

Methods

A total of 159 patients (114 with sepsis, 45 without sepsis) were studied prospectively upon admission to the medical intensive care unit (ICU) as well as after 3 days of ICU treatment and compared to 50 healthy controls. Clinical data, various laboratory parameters as well as investigational inflammatory cytokine profiles were assessed. Patients were followed for approximately 1 year.

Results

We found significantly elevated serum levels of OPN at admission to the ICU and after 3 days of treatment in critically ill patients compared to healthy controls. OPN concentrations were related to disease severity and significantly correlated with established prognosis scores and classical as well as experimental markers of inflammation and multi-organ failure. In the total cohort, OPN levels decreased from admission to day 3 of ICU treatment. However, persistently elevated OPN levels at day 3 of ICU treatment were a strong independent predictor for an unfavorable prognosis, with similar or better diagnostic accuracy than routinely used markers of organ failure or prognostic scoring systems such as SAPS2 or APACHE II score.

Conclusions

Persistently elevated OPN serum concentrations are associated with an unfavourable outcome in patients with critical illness, independent of the presence of sepsis. Besides a possible pathogenic role of OPN in critical illness, our study indicates a potential value for OPN as a prognostic biomarker in critically ill patients during the early course of ICU treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0988-4) contains supplementary material, which is available to authorized users.

Diagnostic and prognostic value of osteopontin in patients with acute congestive heart failure

AIMS

To evaluate the diagnostic and prognostic value of osteopontin in patients with acute dyspnoea and/or peripheral oedema suspected of having acute congestive heart failure (aCHF).

METHODS AND RESULTS

A total of 401 patients presenting with acute dyspnoea and/or peripheral oedema to the emergency department were prospectively enrolled and followed up for up to 5 years. Blood samples for biomarker measurements were collected on admission to the emergency department. Osteopontin combined with NT-proBNP vs. NT-proBNP alone for diagnosis of aCHF was tested. Additionally, osteopontin vs. NT-proBNP for prognostic outcomes (i.e. all-cause mortality, aCHF-related rehospitalization, and both in combination) was tested. The diagnostic and prognostic capacity of osteopontin was tested by C-statistics, reclassification indices, and multivariable Cox prediction models. Osteopontin plus NT-proBNP improved the diagnostic capacity for aCHF diagnosis [accuracy 76%, 95% confidence interval (CI) 72-80%; specificity 74%, 95% CI 69-79%, net reclassification improvement (NRI) +0.10] compared with NT-proBNP alone in the emergency department (P = 0.0001). Osteopontin independently predicted all-cause mortality and aCHF-related rehospitalization after 1 and 5 years. Compared with NT-proBNP, osteopontin was of superior prognostic value, specifically in aCHF patients and for the prognostic outcome of aCHF-related rehospitalization.

CONCLUSION

Osteopontin improves aCHF diagnosis when combined with NT-proBNP. Osteopontin identifies aCHF patients with high 1- and 5-year mortality and rehospitalization risk, and adds prognostic value to NT-proBNP. Trial registration NCT00143793.

Osteopontin predicts adverse right ventricular remodelling and dysfunction in pulmonary hypertension

BACKGROUND

Osteopontin (OPN) was found upregulated in several heart failure models and appears to play an important role in myocardial remodelling. As we have previously demonstrated that OPN predicts mortality in patients with pulmonary hypertension (PH), we now evaluated whether OPN also predicts adverse right ventricular (RV) remodelling and dysfunction in PH.

METHODS

We prospectively included 71 patients with PH of different etiology in this study. OPN plasma level were determined by ELISA and assessed for correlation with RV dilatation and dysfunction determined by echocardiography.

RESULTS

OPN plasma values significantly correlated with RV end-diastolic diameter, Tricuspid Annular Plane Systolic Excursion (TAPSE) and Tricuspid Annular Systolic Velocity (TASV) (r = 0·43, P = 0·0002; r = -0·46, P = 0·0006; r = -0·31, P = 0·02). Furthermore, stratification of our study population according to RV end-diastolic diameter and RV dysfunction revealed that patients with enlarged and functionally impaired RV's display higher OPN levels (956 ng/mL vs. 628 ng/mL, P = 0·0005; 1108 ng/mL vs. 792 ng/mL; P = 0·02). Next, we determined OPN cut-off values for the detection of RV remodelling and dysfunction by receiver operating curve analyses and further stratified these parameters in a multivariate analysis. Here, OPN emerged as an independent predictor of RV dilatation and dysfunction. Finally, we demonstrate synergism of OPN and NT-proBNP in the prediction of RV dilatation and dysfunction by calculation of the Rothman Synergy Index.

CONCLUSION

In summary, OPN predicts adverse RV remodelling and dysfunction in PH. Together with our previously published data regarding OPN's value for the prognostication of death in PH, we believe that OPN can improve risk stratification in patients with PH beyond current assessment standards.