Plasma Osteopontin Concentrations Research Articles

Plasma concentrations of matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1 and osteopontin reflect severity of heart failure in DOCA-salt hypertensive rat

The matrix metalloproteinases (MMPs) and their endogenous inhibitors, the tissue inhibitors of metalloproteinases (TIMPs) play a key role in extracellular matrix maintenance and are altered in the failing heart, both in experimental models and in chronic end-stage heart failure in humans. As the common diagnostic markers of heart failure, atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) primarily reflect increased pressure loading, determination of soluble, heart-derived MMPs and TIMPs in plasma, as well as the determination of the emerging fibrosis marker osteopontin (OPN) might be valuable tools for detecting heart fibrosis. In this study the effect of spironolactone treatment on plasma MMP-2, TIMP-1 and OPN levels was assessed in a heart failure animal model. Unilaterally nephrectomized Sprague Dawley rats received subcutaneous injection of 100 mg deoxycorticosterone acetate (DOCA) once a week and 1% (w/v) NaCl in drinking water. Blood pressure was monitored weekly and blood samples were collected after 1, 2 and 4 weeks. After 6 weeks, left ventricular contractility (LVC) and heart weight-to-body weight ratio (HW/BW) were assessed. DOCA treatment increased plasma MMP-2, TIMP-1 and OPN concentrations. Alterations of plasma marker levels were correlated with changes of HW/BW and paralleled impaired LVC. Furthermore, beneficial effects of spironolactone treatment were observed. In DOCA-salt hypertensive rats, plasma concentrations of MMP-2, TIMP-1 and OPN reflected heart failure associated with haemodynamic, functional and morphological changes. Based on these findings, it appears reasonable to use plasma markers of fibrosis to monitor the development of heart failure.

Osteopontin Expression in Human and Murine Obesity: Extensive Local Up-Regulation in Adipose Tissue but Minimal Systemic Alterations

Obesity is associated with a chronic low-grade inflammation characterized by macrophage infiltration of adipose tissue (AT) that may underlie the development of insulin resistance and type 2 diabetes. Osteopontin (OPN) is a multifunctional protein involved in various inflammatory processes, cell migration, and tissue remodeling. Because these processes occur in the AT of obese patients, we studied in detail the regulation of OPN expression in human and murine obesity. The study included 20 morbidly obese patients and 20 age- and sex-matched control subjects, as well as two models (diet-induced and genetic) of murine obesity. In high-fat diet-induced and genetically obese mice, OPN expression was drastically up-regulated in AT (40 and 80-fold, respectively) but remained largely unaltered in liver (<2-fold). Moreover, OPN plasma concentrations remained unchanged in both murine models of obesity, suggesting a particular local but not systemic importance for OPN. OPN expression was strongly elevated also in the AT of obese patients compared with lean subjects in both omental and sc AT. In addition, we detected three OPN isoforms to be expressed in human AT and, strikingly, an obesity induced alteration of the OPN isoform expression pattern. Analysis of AT cellular fractions revealed that OPN is exceptionally highly expressed in AT macrophages in humans and mice. Moreover, OPN expression in AT macrophages was strongly up-regulated by obesity. In conclusion, our data point toward a specific local role of OPN in obese AT. Therefore, OPN could be a critical regulator in obesity induced AT inflammation and insulin resistance.

Plasma Osteopontin Levels and Expression in Adipose Tissue Are Increased in Obesity

Obesity acts as a cardiovascular risk factor by mechanisms that are not fully understood. Osteopontin (OPN) is a proinflammatory mediator involved in tissue remodeling that plays a role in atherosclerosis and diabetes. The aim of the present study was to compare the circulating concentrations of OPN and its mRNA expression in omental adipose tissue of lean, overweight, and obese individuals and to analyze the effect of weight loss. Plasma concentrations of OPN were measured in 77 volunteers. OPN mRNA expression in omental adipose tissue obtained from 12 women was quantified by real-time PCR. In addition, the concentrations of OPN in 12 obese men were measured before and after weight loss following a dietetic program. The study was conducted at a University Hospital. Obese and overweight patients exhibited significantly increased circulating OPN concentrations as compared with lean subjects (obese 72.6 +/- 28.5, overweight 68.2 +/- 20.8, lean 42.7 +/- 27.9 ng/ml; P < 0.001). A significant positive correlation was found between OPN levels and body fat (r = 0.45; P < 0.0001). Obese individuals showed significantly increased (P < 0.05) mRNA expression of OPN in omental adipose tissue as compared with lean volunteers, which was further increased in obese diabetic patients. Diet-induced weight loss significantly decreased OPN concentrations from 64.7 +/- 22.1 to 36.6 +/- 20.1 ng/ml (P = 0.006). These findings represent the first observation that plasma OPN and mRNA expression of OPN in omental adipose tissue are increased in overweight/obese patients with the latter being further elevated in obesity-associated diabetes. Moreover, weight loss reduces OPN concentrations, which may contribute to the beneficial effects accompanying weight reduction. Measurement of OPN might be useful for evaluating the outcomes of various clinical interventions for obesity-related cardiovascular diseases.

Plasma and crevicular fluid osteopontin levels in periodontal health and disease

The level of osteopontin in gingival crevicular fluid has been found to correlate with clinical measures of periodontal disease. The present study was designed to assess the relationship between clinical parameters and osteopontin levels of the gingival crevicular fluid from inflamed gingivae, periodontitis sites and after treatment of periodontitis sites, and to correlate them to the osteopontin levels of the plasma. Thirty, gender-matched subjects were divided into three groups--healthy, gingivitis and chronic periodontitis--based on modified gingival index scores and clinical attachment loss. The fourth group consisted of 10 subjects in the periodontitis group, 6-8 wk after initial therapy. Plasma and gingival crevicular fluid samples were collected and quantified for osteopontin using an enzyme immunoassay. The highest mean gingival crevicular fluid and plasma osteopontin concentrations were observed in the periodontitis group (1575.01 and 1273.21 ng/mL, respectively) and the lowest in the healthy group (1194.80 and 476.35 ng/mL, respectively). After treatment of the periodontitis group, the level of osteopontin decreased to 1416.15 in gingival crevicular fluid and to 1051.68 ng/mL in plasma. In all groups the gingival crevicular fluid osteopontin levels showed a statistically significant positive correlation with that of plasma and clinical attachment loss. Osteopontin levels were highest in the gingival crevicular fluid from sites with periodontal destruction; however, periodontal treatment resulted in the reduction of osteopontin levels. Gingival crevicular fluid and plasma osteopontin levels showed a positive correlation in all of the groups.

Osteopontin levels are associated with cholesterol synthesis markers in mildly hypercholesterolaemic patients

Objective — Atherosclerotic lesions are characterized by an accumulation of inflammatory cells and lipids. Osteopontin (OPN) is a cell-binding phosphoprotein, and it seems to promote the development of atherosclerosis.The purpose of our study was to find out whether plasma levels of OPN are associated with cholesterol metabolites in plasma or tissues.Methods and results — Forty-three normal or mildly hypercholesterolaemic subjects, aged 31 to 69, were studied.The plasma level of OPN correlated negatively with muscle lathosterol (r = –0.52, P < 0.0001) and with the muscle lathosterol to muscle cholesterol ratio (r = –0.48, P=0.001). Lathosterol concentrations in muscle (P=0.003) and in relation to cholesterol (P=0.005) were also significantly different among the OPN tertiles. OPN correlated negatively and significantly with muscle lathosterol in men (r = –0.58, P=0.001, n=29) but not in women (r = –0.21, P =0.48, n=14). Correspondingly, it also correlated negatively and significantly with the muscle lathosterol to muscle cholesterol ratio (r = –0.60, P=0.001) in men but not in women (r = –0.13, P=0.65). Plasma levels of OPN had a non-significant inverse correlation with plasma lathosterol and the plasma lathosterol to plasma cholesterol ratio. Plasma OPN concentrations were not related to plant sterols, cholesterol and 27-hydroxycholesterol.Conclusions — Tissue markers of cholesterol synthesis were related to plasma OPN, particularly in men.This suggests that there is interplay between OPN and cholesterol metabolism in human cells.

High Plasma Osteopontin Levels in Patients With Inflammatory Bowel Disease

Osteopontin (OPN) plays a key role in the progression of T(H)1-immune-mediated disease in models of multiple sclerosis and rheumatoid arthritis. To determine whether plasma OPN levels in patients with inflammatory bowel disease are associated with disease activity. Plasma samples were obtained from patients with ulcerative colitis (UC, n=30), Crohn's disease (CD, n=30), and healthy volunteers (controls, n=30) and enzyme immunoassay was performed. Plasma OPN concentrations were significantly higher in patients with Crohn's disease than in controls (951.9+/-538.5 ng/mL and 659.0+/-163.7 ng/mL, respectively). OPN concentrations in patients with UC were also higher than in the controls (1149.6+/-791.0 and 659.0+/-163.7, respectively). There was a significant difference in plasma OPN level between active UC and inactive UC (2102.0+/-552.8 and 649.4+/-313.0, respectively). Moreover, a significant correlation was observed between plasma OPN concentration and disease activity, as determined by the clinical activity index in patients with UC. Our results indicate that the plasma concentrations of OPN are elevated in patients with UC and that OPN expression is correlated with clinical activity. These results provide insight into UC pathogenesis and suggest that OPN may be a useful tool for assessing disease activity.

P38 MAPK inhibitors suppress biomarkers of hypertension end-organ damage, osteopontin and plasminogen activator inhibitor-1

The assessment of target organ damage is important in defining the optimal treatment of hypertension and blood pressure-related cardiovascular disease. The aims of the present study were (1) to investigate candidate biomarkers of target organ damage, osteopontin (OPN) and plasminogen activator inhibitor-1 (PAI-1), in models of malignant hypertension with well characterized end-organ pathology; and (2) to evaluate the effects of chronic treatment with a p38 MAPK inhibitor. Gene expression, plasma concentrations, and renal immunohistochemical localization of OPN and PAI-1 were measured in stroke-prone spontaneously hypertensive rats on a salt–fat diet (SFD SHR-SP) and in spontaneously hypertensive rats receiving Nω-nitro-L-arginine methyl ester (L-NAME SHR). Plasma concentrations of OPN and PAI-1 increased significantly in SFD SHR-SP and L-NAME SHR as compared with controls, (2.5–4.5-fold for OPN and 2.0–9.0-fold for PAI-1). The plasma levels of OPN and PAI-1 were significantly correlated with the urinary excretion of albumin (p<0.0001). Elevations in urinary albumin, plasma OPN and PAI-1 were abolished by chronic treatment (4–8 weeks) with a specific p38 MAPK inhibitor, SB-239063AN. OPN immunoreactivity was localized predominantly in the apical portion of tubule epithelium, while PAI-1 immunoreactivity was robust in glomeruli, tubules and renal artery endothelium. Treatment with the p38 MAPK inhibitor significantly reduced OPN and PAI-1 protein expression in target organs. Kidney gene expression was increased for OPN (4.9- and 7.9-fold) and PAI-1 (2.8- and 11.5-fold) in SFD SHR-SP and L-NAME SHR, respectively. In-silico pathway analysis revealed that activation of p38 MAPK was linked to OPN and PAI-1 via SP1, c-fos and c-jun; suggesting that these pathways may play an important role in p38 MAPK-dependent hypertensive renal dysfunction. The results suggest that enhanced OPN and PAI-1 expression reflects end-organ damage in hypertension and that suppression correlates with end-organ protection regardless of overt antihypertensive action.

Biological variation and reference intervals for circulating osteopontin, osteoprotegerin, total soluble receptor activator of nuclear factor kappa B ligand and high‐sensitivity C‐reactive protein

Objective. Monitoring inflammatory diseases and osteoclastogenesis with osteopontin (OPN), osteoprotegerin (OPG), total soluble receptor activator of nuclear factor kappa B ligand (total sRANKL) and high‐sensitivity C‐reactive protein (hsCRP) has recently attracted increased interest. The purpose of our study was to determine reference intervals, variability caused by sampling time, biological variation and stability after repeated freeze–thaw cycles of circulating levels of OPN, OPG, total sRANKL and hsCRP. Material and methods. Plasma OPN and plasma OPG concentrations were determined with sandwich ELISA; serum total sRANKL concentration was determined using a two‐site sandwich ELISA; and hsCRP was analysed by turbidimetry in 300 Danish blood donors (183 M and 117 F) with a median age of 43 years (range 18–64 years). Variability due to biological variation and sampling time was studied in serial samples from 38 healthy subjects. Results. The 95th percentiles in the donors were 76 µg/L for OPN, 4.2 pmol/L for OPG, 40.2 nmol/L for total sRANKL and 12 mg/L for hsCRP. The overall medians for both genders were 51 µg/L, 2.2 pmol/L, 0.66 nmol/L and 1.0 mg/L, respectively. We found a significant correlation between hsCRP and OPN (rho = 0.173; p<0.003). The biological within‐subject variations were calculated to be 8.2 % for OPN, 8.8 % for total sRANKL and 50 % for hsCRP. Conclusions. Reference intervals have been established with a high analytic performance for OPN and an acceptable analytic performance for OPG and total sRANKL. The study revealed low biological variation for OPN and total sRANKL and high biological variation for hsCRP.

Elevated osteopontin (OPN) plasma levels are highly prognostic in advanced non-small cell lung cancer (NSCLC): Analysis of SWOG S0003

7198 Background: OPN is a secreted glycoprotein with a diverse array of functions, including induction of uPA &amp; increased cell migration. OPN has been shown to be elevated in a number of tumor types, &amp; its downregulation reduces tumorigenicity &amp; metastasis in tumor models. High levels have also been associated with tumor hypoxia/angiogenesis, as are vascular endothelial growth factor (VEGF) &amp; plasminogen activator inhibitor (PAI-1). We hypothesized that secreted levels of these biomarkers would correlate with clinical outcome after treatment. Methods: Plasma concentrations of OPN, VEGF &amp; PAI-1 were measured by ELISA in 160 NSCLC patients enrolled on the Southwest Oncology Group (SWOG) trial S0003 (paclitaxel/carboplatin ± the hypoxic cytotoxin tirapazamine). Post-treatment plasma samples were available in 56 patients. Results: Baseline OPN plasma levels correlated significantly with patient overall survival (OS). High interpatient variability was observed, with levels ranging from undetectable to 2560 ng/ml, (median: 606.5 ng/ml). When dichotomized, median OS was 11 months for patients below median OPN levels &amp; 7 months for those above (p = 0.004). Survival decreases with increasing OPN concentration. Furthermore, OPN levels correlated with response rate (RR) (median responders: 497; median non-responders: 698 ng/ml. Wilcoxon rank-sum p = 0.03). No association between baseline levels of either VEGF or PAI-1 with RR or OS was observed. However, plasma levels of both PAI-1 &amp; VEGF were significantly inter-related &amp; trended together (p &lt; 0.0001), &amp; both decreased significantly after treatment (p = 0.0004 &amp; 0.04, respectively). Median decrease: OPN: 17%, PAI: 44%, VEGF: 42%. No significant differences were observed between study arms, suggesting that OPN is prognostic in NSCLC, but not predictive for response to tirapazamine. Conclusions: 1) There is a great need for development of tumor biomarkers which can be serially assessed pre- &amp; post-therapy. 2) High OPN plasma levels were significantly associated with reduced RR &amp; OS for patients on this trial. OPN is a strong candidate for inclusion in a panel of prognostic (&amp; perhaps predictive) markers for NSCLC. Supported by the Hope Foundation &amp; R01-CA107228. No significant financial relationships to disclose.

Prognostic significance of plasma osteopontin levels in patients with chronic stable angina

Levels of the secreted glycophosphoprotein osteopontin (OPN) have been associated with the presence and extent of coronary artery disease (CAD). The present study assessed the relationship between plasma OPN concentrations and prognosis in patients with chronic stable angina (CSA). OPN was measured in baseline plasma samples from 799 patients with stable angina pectoris and angiographically documented CAD. Participants were prospectively followed-up for a median of 2.7 years (maximum 4.1 years). The primary study endpoint was the composite of non-fatal myocardial infarction and death from cardiovascular causes. In the univariate Cox proportional hazard analysis, the log-transformed OPN level [hazard ratio (HR) 1.79, 95% CI 1.35-2.36, P < 0.001] was significantly related to adverse outcome. In addition, hypertension, levels of C-reactive protein, and statin use were associated with future adverse events. Levels of OPN (HR, 1.88; P < 0.001) and C-reactive protein (HR, 1.42; P = 0.003), as well as the presence of hypertension (HR, 2.39; P = 0.008) remained statistically significant, independent predictors of adverse cardiovascular outcome in a multivariable Cox proportional hazard analysis. Baseline levels of OPN are an independent predictor of future adverse cardiac events in patients with CSA and may be useful for risk stratification.

Plasma osteopontin, hypoxia, and response to the hypoxia sensitiser nimorazole in radiotherapy of head and neck cancer: results from the DAHANCA 5 randomised double-blind placebo-controlled trial

The concentration of osteopontin (SPP1) in plasma is associated with tumour hypoxia. The DAHANCA 5 trial found that the hypoxia radiosensitiser nimorazole significantly improved the outcome of radiotherapy for patients with head and neck cancer compared with placebo. However, whether all patients benefit from such modification of hypoxia is unclear. We aimed to assess whether the concentration of plasma osteopontin could predict response to the hypoxia radiosensitiser. Plasma concentrations of osteopontin were measured by use of ELISA from stored samples of 320 patients randomised in the DAHANCA 5 trial. Samples were grouped into tertiles according to high (167-1382 microg/L), intermediate (69-166 microg/L), or low (0-68 microg/L) concentrations of plasma osteopontin, and analysed for locoregional tumour control and disease-specific survival at 5 years. Overall, locoregional tumour failure and disease-specific mortality were more frequent in patients assigned placebo than in those assigned nimorazole (relative risk [RR] 0.51 [95% CI 0.32-0.79] and 0.54 [0.35-0.85], respectively). Locoregional tumour failure was more frequent in patients with high concentrations of osteopontin assigned placebo than in those with high concentrations assigned nimorazole (0.19 [0.08-0.44]), as was disease-specific mortality (0.25 [0.11-0.59]). However, neither locoregional tumour failure nor disease-specific mortality differed between groups for patients with low concentrations of plasma osteopontin (0.79 [0.26-1.70]) and (0.69 [0.31-1.51]) or for those with intermediate concentrations (0.90 [0.41-1.98] and 0.89 [0.41-1.96], respectively). High plasma concentrations of osteopontin are associated with a poor outlook after radiotherapy for patients with head and neck cancer, but can be improved by use of nimorazole. High concentrations of osteopontin can predict clinically relevant hypoxia, and might identify patients who will benefit from modification of hypoxia during radiotherapy.

Elevation of plasma osteopontin concentration is correlated with disease activity in patients with systemic lupus erythematosus

Osteopontin (OPN) is an extracellular matrix cell adhesion phosphoprotein with immunological activities including stimulation of macrophage chemotaxis, T-helper type 1 lymphocyte response and B-cell antibody synthesis. Overexpression of OPN has been associated with the development of the autoimmune/lymphoproliferative syndrome. We measured the plasma concentration and ex vivo production of OPN, and the plasma proinflammatory IL-18 concentration in 54 SLE patients with or without renal impairment (RSLE group and SLE group, respectively) and 26 sex- and age-matched control (NC) subjects using an enzyme-linked immunoabsorbent assay. Plasma OPN concentrations were significantly higher in RSLE and SLE patients than in the NC group (both P<0.001). Increase in OPN concentration correlated positively and significantly with SLEDAI score in all SLE patients (r = 0.308, P = 0.023). The ex vivo production of OPN upon mitogen activation of peripheral blood mononuclear cells was significantly higher in the RSLE and SLE groups than in the NC group (both P<0.001). In RSLE patients, plasma OPN concentration showed a significant positive correlation with proinflammatory cytokine IL-18 concentration (r = 0.404, P = 0.037). The above results suggest that the production of OPN is associated with the inflammatory process and SLE development, and may serve as a potential disease marker of SLE.

High plasma concentrations of osteopontin in patients with interstitial pneumonia

Osteopontin (OPN) produced by alveolar macrophages functions as a fibrogenic cytokine in the development of bleomycin (BLM)-induced murine pulmonary fibrosis, and OPN mRNA is expressed on lung tissues from patients with idiopathic pulmonary fibrosis (IPF). The present study investigates plasma OPN levels in human interstitial pneumonia (IP) and their relationships with disease severity by analyzing the correlation between plasma OPN concentrations and pulmonary functions. The concentrations of OPN in plasma were measured in 17 patients with IP, in 9 with sarcoidosis and in 20 healthy controls using an antigen-capture enzyme-linked immunosorbent assay. The concentrations of OPN in plasma were significantly higher in IP patients than in those with sarcoidosis or in controls. Based on a Receiver Operating Characteristic curve analysis, cut-off points between 300 and 380 ng/ml discriminated between IP and control subjects with 100% sensitivity and 100% specificity. In such case, the sensitivity for sarcoidosis decreased (55.5–33.3%) in cut-offs with 100% specificity. Plasma OPN levels inversely and closely correlated with arterial oxygen tension (PaO 2) in patients with IP. Immunohistochemically, OPN was localized predominantly in macrophages and airway epithelium. These findings suggest that plasma OPN levels were found to be associated with the presence of IP, and that OPN play an important role in the development of IP.

A Locus on Chromosome 7 Determines Dramatic Up-Regulation of Osteopontin in Dystrophic Cardiac Calcification in Mice

Calcification of necrotic tissue is frequently observed in chronic inflammation and atherosclerosis. A similar response of myocardium to injury, referred to as dystrophic cardiac calcinosis (DCC), occurs in certain inbred strains of mice. We now examined a putative inhibitor of calcification, osteopontin, in DCC after transdiaphragmal myocardial freeze-thaw injury. Strong osteopontin expression was found co-localizing with calcification in DCC-susceptible strain C3H/HeNCrlBr, which exhibited low osteopontin plasma concentrations otherwise. Osteopontin mRNA induction was 20-fold higher than in resistant strain C57BL/6NCrlBr, which exhibited fibrous lesions without calcification and little osteopontin expression. Sequence analysis identified several polymorphisms in calcium-binding and phosphorylation sites in osteopontin cDNA. Their potential relevance for DCC was tested in congenic mice, which shared the osteopontin locus with C57BL/6NCrlBr, but retained a chromosomal segment from C3H/HeNCrlBr on proximal chromosome 7. These mice exhibited strong osteopontin expression and DCC comparable to C3H/HeNCrlBr suggesting that a trans-activator of osteopontin transcription residing on chromosome 7 and not the osteopontin gene on chromosome 5 was responsible for the genetic differences in osteopontin expression. A known osteopontin activator encoded by a gene on chromosome 7 is the transforming growth factor-beta1, which was more induced (3.5x) in C3H/HeNCrlBr than in C57BL/6NCrlBr mice.

Dietary silicon affects bone turnover differently in ovariectomized and sham‐operated growing rats

AbstractAn experiment was performed to test the hypothesis that low dietary silicon affects blood, bone, and urine indices associated with bone formation and breakdown, bone strength and physical characteristics, and the circulating amount of an extracellular matrix protein (osteopontin) involved in bone cell adhesion and activation. A second objective was to ascertain whether ovariectomy (estrogen deficiency) alters the effects of low dietary silicon on bone formation. Female rats weighing about 56 g were assigned to groups of 10 in a factorially arranged experiment. The variables were supplemental dietary silicon at 0 or 35 mg/kg and ovariectomy (estrogen‐deficient) or sham operation at the start of the experiment. The basal silicon‐low diet contained about 2 mg Si/kg. Low dietary silicon compared with adequate silicon decreased plasma osteopontin concentration, increased plasma sialic acid concentration, and increased urinary helical peptide excretion. Low dietary silicon also affected the response to estrogen deficiency. Ovariectomy increased plasma alkaline phosphatase in the silicon‐supplemented, but not in the silicon‐low rats. In contrast, ovariectomy decreased liver ornithine aminotransferase in silicon‐low but not in silicon‐supplemented rats. Ovariectomy increased the urinary excretion of deoxypyridinoline and decreased the femur concentration of sialic acid more markedly in silicon‐supplemented than silicon‐low rats. Silicon and an interaction between silicon and ovariectomy only mildly changed bone strength and physical measurements and did not affect femur calcium concentration. The findings suggest that silicon has a biochemical function that affects bone growth processes before bone crystal formation by affecting bone collagen turnover and sialic acid‐containing extracellular matrix proteins such as osteopontin. J. Trace Elem. Exp. Med. 17:137–149, 2004. Published 2004 Wiley‐Liss, Inc.

Enhanced production of osteopontin in multiple myeloma: clinical and pathogenic implications.

In this study, we examined osteopontin (OPN) production in myeloma cells and plasma OPN levels in multiple myeloma (MM) patients. We assessed OPN production in bone marrow cells (BMCs) by immunocytochemistry and enzyme-linked immunosorbent assay (ELISA). We also assessed OPN production in various B-cell malignant cell lines, including three myeloma cell lines by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. In addition, we measured plasma OPN concentrations by ELISA in 30 MM patients, 21 monoclonal gammopathy of undetermined significance (MGUS) patients and 30 healthy volunteers. As a result, in an immunocytochemical study, abundant OPN was detected in BMCs from overt MM patients, whereas no OPN was detected in BMCs from patients with other haematological diseases, including MGUS. Cultured BMCs from overt MM patients produced more OPN than those from patients with either smouldering MM or MGUS. Myeloma cell lines spontaneously produced OPN. Plasma OPN levels of MM patients were significantly higher than those of MGUS patients and healthy volunteers (P < 0.05). Moreover, they correlated with both progression and bone destruction of the disease (P < 0.05). These suggest that myeloma cells actively produce OPN, which possibly contributes to osteoclastic bone resorption in MM. Plasma OPN levels may be a useful biomarker for assessing bone destruction in MM and distinguishing MM from MGUS or smouldering MM.

Osteopontin is released from the heart into the coronary circulation in patients with a previous anterior wall myocardial infarction.

The present study was designed to clarify whether osteopontin, an extracellular matrix protein, is released from the heart into the coronary circulation in patients with a previous (>3 months) anterior wall myocardial infarction (MI). Using a commercially available enzyme immunoassay kit, plasma concentrations of osteopontin were measured in 30 patients (26 men, 4 women; mean age, 61+/-12 years). Blood samples were obtained from the aortic root and coronary sinus. The difference in the plasma concentrations of osteopontin in the aortic root and coronary sinus, which reflects the cardiac production of osteopontin released into the coronary circulation, was compared with the left ventricular ejection fraction (LVEF) and volumes obtained from contrast left ventriculography. Plasma osteopontin concentrations were significantly higher in the coronary sinus than in the aortic root (672+/-446 vs 610+/-398 ng/ml, p=0.02). The transcardiac gradient of plasma osteopontin concentration correlated negatively with LVEF (r=-0.55, p=0.0005) and positively with left ventricular (LV) end-diastolic (r=0.63, p=0.0001) and end-systolic volume indexes (r=0.79, p<0.0001). This is the first study to show that in patients with a previous anterior wall MI osteopontin is released from the heart into the coronary circulation in proportion to the LV systolic function and volumes, suggesting that this extramatrix protein is associated with post-MI LV remodeling.

Expression of osteopontin at sites of bone erosion in a murine experimental arthritis model of collagen‐induced arthritis: Possible involvement of osteopontin in bone destruction in arthritis

To investigate the involvement of osteopontin (OPN) in bone destruction in a murine experimental arthritis model of collagen-induced arthritis (CIA). The expression of OPN was examined at both the messenger RNA (mRNA) and protein levels in various arthritic lesions in mice with CIA by in situ hybridization and immunohistochemistry, respectively. In addition, the expression of alpha(v)beta3 integrin, a receptor for OPN, the ligation of which is thought to be essential for bone resorption by osteoclasts, was examined by immunohistochemistry. Plasma concentrations of OPN were measured at different time points in the course of CIA by enzyme-linked immunosorbent assay. OPN mRNA was detected mainly at sites of bone erosion in arthritic lesions, where activated osteoclasts were present; OPN protein was also detected at sites of bone erosion. In the arthritic synovium, OPN was predominantly expressed in the synovial lining layer, but not in lymphoid aggregates. In addition, alpha(v)beta3 integrin was detected coincident with OPN at sites of bone erosion (bone-pannus junction). Plasma OPN levels were markedly elevated at the time points that corresponded to arthritis flares, and higher levels were maintained during the progression of arthritis. OPN may mediate bone resorption by osteoclasts in arthritis through ligation with its receptor, alpha(v)beta3 integrin. OPN may be a useful therapeutic target molecule in the prevention of bone destruction in arthritis.

Soluble Osteopontin and Vascular Calcification in Hemodialysis Patients

Background: Vascular calcification often occurs in patients with uremia. As osteopontin (OPN) is not only involved in the physiological but also the pathological calcification of tissues, OPN may be associated with the pathogenesis of aortic calcification in hemodialysis (HD) patients. Methods: We examined the expression of OPN in atherosclerotic aortas of HD patients. In addition, we performed a prospective longitudinal study by using CT scans to detect aortic calcifications and by measuring the plasma OPN concentration by ELISA in HD patients (20 men, 16 women; mean age 55.2 ± 21.3 years) and in healthy volunteers (18 men, 17 women; mean age 54.0 ± 13.2 years). Results: By immunohistochemical staining, OPN was abundantly localized in atherosclerotic plaques of HD patients. The macrophages surrounding the atheromatous plaques were identified as the OPN-expressing cells. We furthermore found that the concentration of soluble plasma OPN was significantly higher in HD patients as compared with the concentrations in age-matched healthy volunteers (837.3 ± 443.2 vs. 315.1 ± 117.4 ng/ml, p < 0.01). The OPN concentration was positively correlated with the aortic calcification index in HD patients (r = 0.749, p < 0.01). Conclusion: These data suggest that OPN, secreted by macrophages, plays a role in the calcification of atheromatous plaques in HD patients.