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1.  Effects of Corticosteroids on Osteopontin Expression in a Murine Model of Allergic Asthma 
Osteopontin (OPN) contributes to the development of T helper 1 (Th1)-mediated immunity and Th1-associated diseases. However, the role of OPN in bronchial asthma is unclear. Corticosteroids reduce airway inflammation, as reflected by the low eosinophil and T-cell counts, and the low level of cytokine expression. We investigated OPN production and the inhibitory effects of corticosteroids on OPN production in a murine model of allergic asthma.
BALB/c mice were sensitized by intraperitoneal injections of ovalbumin (OVA) with alum. Some mice received daily injections of dexamethasone (DEX) or phosphate-buffered saline for 1 week. All OVA-challenged mice were exposed to aerosolized 1% OVA for 30 min an hour after these injections. After the OVA challenge, the mice were killed, and bronchoalveolar lavage (BAL) fluid and lung tissue were examined.
The levels of OPN protein in BAL fluid and OPN mRNA in lung tissue increased after OVA challenge. Most OPN-expressing cells were CD11c+ cells and some were T cells. DEX decreased the levels of OPN protein in the BAL fluid, and those of OPN mRNA and OPN protein in lung tissue.
OPN may play an important role in allergic bronchial asthma. Corticosteroids inhibit OPN production in mice with allergic asthma. The beneficial effect of corticosteroids in bronchial asthma is partly due to their inhibitory effects on OPN production.
PMCID: PMC2844795  PMID: 19494498
Osteopontin; Corticosteroid; Mouse; Dendritic cells; CD11c; Bronchial asthma
2.  The expression of osteopontin and its association with Clara cell 10-kDa protein in allergic rhinitis 
Osteopontin (OPN) is a multifunctional protein which has recently been linked to allergic diseases. Clara cell 10-kDa protein (CC10) is another protein linked to allergy, and has been suggested to have an inhibitory role in inflammatory airway diseases. At this time, it is not known whether OPN is involved in allergic rhinitis (AR) or if there is any association between CC10 and OPN in AR.
To study the expression of OPN and its potential association with CC10 in AR.
The expression of CC10 and OPN in nasal mucosa of AR patients was investigated. AR animal models were established by employing wild-type and CC10-knockout mice. In some experiments, human recombinant CC10 protein was given to AR mice during either sensitization or challenge. The phenotypic changes were examined by histology and real-time RT-PCR. The direct effect of CC10 on OPN expression in spleen mononuclear cells and on OPN-induced inflammatory cytokine expression in BEAS-2B cells was measured through in vitro cell culture.
OPN expression was up-regulated, with a concomitant down-regulation of CC10, in AR patients, showing a significant negative correlation between their expression. Compared with control mice sensitized with PBS, OPN expression was significantly increased in AR mice; such increase was more prominent in CC10-knockout mice, compared to wild-type. Administration of CC10 during both sensitization and challenge could markedly ameliorate Th2-skewed inflammation and OPN expression in nasal mucosa. CC10 administration at the sensitization phase could also reduce spleen OPN expression. The in vitro study showed that CC10 directly down-regulated OPN expression in spleen mononuclear cells stimulated with OVA and suppressed OPN-induced expression of Th2 cytokines and proinflammatory cytokines in BEAS-2B cells.
In the context of allergic airway responses, CC10 can inhibit OPN expression and suppress the Th2 promoting function of OPN, resulting in CC10’s inhibitory biological effects.
PMCID: PMC2948078  PMID: 20553297
allergic rhinitis; Clara cell 10-kDa protein; osteopontin; regulation
3.  Syndecan-4 protects against osteopontin-mediated acute hepatic injury by masking functional domains of osteopontin 
Osteopontin (OPN) is a T helper type 1 immunoregulatory cytokine that plays a critical role in various inflammatory disorders. OPN exerts proinflammatory reactions through interaction with integrin receptors. OPN function can be modulated by protease digestion. However, the molecular mechanisms that regulate OPN function in vivo have not been elucidated. There are two putative heparin-binding domains (HBDs) within the OPN molecule, which may bind both heparin and heparin-like glycosaminoglycans such as syndecan. We show that expression of OPN and syndecan-4 is significantly up-regulated after concanavalin-A (ConA) injection. Syndecan-4 binds to one of the HBDs of OPN, which overlaps with the thrombin cleavage site of OPN. When OPN is associated with syndecan-4, syndecan-4 masks both the thrombin cleavage and the integrin binding sites within OPN. Importantly, syndecan-4–deficient (Syn4KO) mice are more susceptible to hepatic injury, and the thrombin-cleaved form of OPN is significantly elevated in Syn4KO mice as compared with wild-type mice after ConA injection. Finally, we demonstrate that administration of purified syndecan-4 protects mice from ConA-induced hepatic injury. Thus, syndecan-4 is a critical intrinsic regulator of inflammatory reactions via its effects on OPN function and is a potential novel therapeutic tool for treating inflammatory diseases.
PMCID: PMC2234375  PMID: 18158320
4.  Quantitative expression of osteopontin in nasal mucosa of patients with allergic rhinitis: effects of pollen exposure and nasal glucocorticoid treatment 
Osteopontin (OPN) is a multifunctional cytokine that has been primarily investigated in Th1 diseases. Recently, it has also been implicated in Th2-mediated allergic diseases, such as asthma. The expression of OPN in allergic rhinitis (AR) is currently unknown, as is the effect of intranasal glucocorticosteroids (GCs) on that expression.
Subjects with AR were randomised to receive treatment with fluticasone propionate (FP) (n = 12) or a placebo (n = 16) over the grass pollen season and nasal biopsies were taken prior to, and during the season. OPN expression in the nasal mucosa was examined with immunohistochemistry. Healthy non-AR controls (n = 5) were used as a comparator.
OPN expression was detected in epithelial cells, subepithelial infiltrating/inflammatory cells and cells lining the vessels and glands of all subjects. Comparison of the pre- and peak-pollen season biopsy sections in placebo treated patients revealed no increase in OPN expression during the grass pollen season (5.7% vs 6.4%). Treatment with a local glucocorticosteroid did not alter the expression of OPN during pollen exposure (6.2% vs 6.7%).
OPN has been increasingly associated with the pathogenesis of various Th2-mediated diseases. However, our finding that the OPN expression in the nasal mucosa of AR patients is not significantly affected by allergen exposure and is comparable to that of the healthy controls, suggests that intracellular OPN is not directly involved in the pathogenesis of allergic rhinitis.
PMCID: PMC2988772  PMID: 21044308
5.  Differentiation, Maturation, and Survival of Dendritic Cells by Osteopontin Regulation 
Dendritic cells (DCs) are antigen-presenting cells with the ability to induce primary immune responses necessary in innate immunity and adaptive immunity. Osteopontin (OPN) is a secreted acidic phosphoprotein containing an arginine-glycine-aspartate sequence and has been suggested to play an important role in early cellular immune responses. The interaction between DCs and OPN has not been clarified. We hypothesized that there is an important interaction between DCs and OPN, which is an indispensable extracellular matrix component in early cellular immune responses. Human monocyte-derived DCs synthesized OPN especially during the differentiation from monocytes to immature DCs. By blocking of OPN with anti-OPN antibody, cultured DCs became smaller and expressed lower levels of costimulatory molecules and major histocompatibility complex class II antigens than untreated DCs. Furthermore, DCs treated with anti-OPN antibody easily underwent apoptosis. These results suggest that human DCs can produce OPN and that OPN may play a role in the differentiation, maturation, and survival of DCs by autocrine and/or paracrine pathways.
PMCID: PMC540203  PMID: 15643009
6.  Osteopontin in Systemic Sclerosis and its Role in Dermal Fibrosis 
Osteopontin (OPN) is a matricellular protein with proinflammatory and profibrotic properties. Previous reports demonstrate a role for OPN in wound healing and pulmonary fibrosis. Herein, we determined if OPN levels are increased in a large cohort of systemic sclerosis (SSc) patients and if OPN contributes dermal fibrosis. Plasma OPN levels were increased in SSc patients, including patients with limited and diffuse disease, compared to healthy controls. Immunohistology demonstrated OPN on fibroblast-like and inflammatory cells in SSc skin and lesional skin from mice in the bleomycin-induced dermal fibrosis model. OPN deficient (OPN−/−) mice developed less dermal fibrosis compared to wild-type mice in the bleomycin-induced dermal fibrosis model. Additional in vivo studies demonstrated that lesional skin from OPN−/− mice had fewer Mac-3+ cells, fewer myofibroblasts, decreased TGF-beta (TGFβ) and genes in the TGFβ pathway and decreased numbers of cells expressing phosphorylated SMAD2 (pSMAD) and ERK. In vitro, OPN−/− dermal fibroblasts had decreased migratory capacity but similar phosphorylation of SMAD2 by TGFβ. Finally, TGFβ production by OPN deficient macrophages was reduced compared to wild type. These data demonstrate an important role for OPN in the development of dermal fibrosis and suggest that OPN may be a novel therapeutic target in SSc.
PMCID: PMC3365548  PMID: 22402440
7.  Osteopontin Is Involved in the Initiation of Cutaneous Contact Hypersensitivity by Inducing Langerhans and Dendritic Cell Migration to Lymph Nodes 
The Journal of Experimental Medicine  2001;194(9):1219-1230.
Osteopontin (OPN) is a chemotactic protein that attracts immune cells, to inflammatory sites. The sensitization phase of allergic cutaneous contact hypersensitivity (CHS) requires the migration of Langerhans cells/dendritic cells (LCs/DCs) from skin to draining lymph nodes. Characterizing OPN function for LC/DC migration we found upregulated OPN expression in hapten sensitized skin and draining lymph nodes. OPN induces chemotactic LC/DC migration, initiates their emigration from the epidermis, and attracts LCs/DCs to draining lymph nodes by interacting with CD44 and αv integrin. Furthermore, OPN-deficient mice have a significantly reduced CHS response that correlates with an impaired ability of OPN-deficient mice to attract LCs/DCs to draining lymph nodes. In conclusion, OPN is an important factor in the initiation of CHS by guiding LCs/DCs from skin into lymphatic organs.
PMCID: PMC2195976  PMID: 11696588
dendritic cells; Langerhans cells; integrins; CD44; osteopontin
8.  Increased osteopontin expression in dendritic cells amplifies IL-17 production by CD4+ T cells in experimental autoimmune encephalomyelitis and in multiple sclerosis 
Osteopontin (Opn) is a broadly expressed pleiotropic cytokine and has been shown to play an important role in various autoimmune diseases including multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). It is reported that Opn exacerbates EAE by skewing T cell differentiation towards IFN-γ producing Th1 cells. Opn expression in dendritic cells (DCs) and its role in IL-17 induction from T cells during EAE or MS is unknown. We found that during EAE Opn expression is elevated in DCs both in the periphery and in the central nervous system. There was increased expression of Opn receptor on T cells and Opn induced IL-17 production by CD4+ T cells via the β3 integrin receptor and Opn inhibited IL-10 production via the CD44 receptor. Furthermore, anti-Opn treatment reduced clinical severity of EAE by reducing IL-17 production. Anti-Opn was also effective in reducing clinical severity of EAE when given after the appearance of clinical symptoms. Analogous to EAE, in subjects with MS we found increased expression of Opn in DCs and increased expression of the Opn receptors CD44, β3 and αv on T cells. Furthermore, Opn stimulated CD4+ T cells from MS patients produced significantly higher amounts of IL-17. Our results demonstrate a role for DC produced Opn both in EAE and MS that is linked to the production of IL-17.
PMCID: PMC2653058  PMID: 19017937
Dendritic cells; T cells; EAE/MS and Osteopontin
9.  Role of Hepatitis C Virus Induced Osteopontin in Epithelial to Mesenchymal Transition, Migration and Invasion of Hepatocytes 
PLoS ONE  2014;9(1):e87464.
Osteopontin (OPN) is a secreted phosphoprotein which has been linked to tumor progression and metastasis in a variety of cancers including hepatocellular carcinoma (HCC). Previous studies have shown that OPN is upregulated during liver injury and inflammation. However, the role of OPN in hepatitis C virus (HCV)-induced liver disease pathogenesis is not known. In this study, we determined the induction of OPN, and then investigated the effect of secreted forms of OPN in epithelial to mesenchymal transition (EMT), migration and invasion of hepatocytes. We show the induction of OPN mRNA and protein expression by HCV-infection. Our results also demonstrate the processing of precursor OPN (75 kDa) into 55 kDa, 42 kDa and 36 kDa forms of OPN in HCV-infected cells. Furthermore, we show the binding of secreted OPN to integrin αVβ3 and CD44 at the cell surface, leading to the activation of downstream cellular kinases such as focal adhesion kinase (FAK), Src, and Akt. Importantly, our results show the reduced expression of epithelial marker (E-cadherin) and induction of mesenchymal marker (N-cadherin) in HCV-infected cells. We also show the migration and invasion of HCV-infected cells using wound healing assay and matrigel coated Boyden chamber. In addition, we demonstrate the activation of above EMT markers, and the critical players involved in OPN-mediated cell signaling cascade using primary human hepatocytes infected with Japanese fulminant hepatitis (JFH)-1 HCV. Taken together, these studies suggest a potential role of OPN in inducing chronic liver disease and HCC associated with chronic HCV infection.
PMCID: PMC3909125  PMID: 24498111
10.  The role of osteopontin in inflammatory processes 
Osteopontin (OPN) is a matricellular protein that mediates diverse biological functions. OPN is involved in normal physiological processes and is implicated in the pathogenesis of a variety of disease states, including atherosclerosis, glomerulonephritis, cancer, and several chronic inflammatory diseases. Through interactions with several integrins, OPN mediates cell migration, adhesion, and survival in many cell types. OPN also functions as a Th1 cytokine, promotes cell-mediated immune responses, and plays a role in chronic inflammatory and autoimmune diseases. Besides its function in inflammation, OPN is also a regulator of biomineralization and a potent inhibitor of vascular calcification.
PMCID: PMC2778587  PMID: 19798593
Inflammation; Matricellular protein; Osteopontin
11.  The role of osteopontin in inflammatory processes 
Osteopontin (OPN) is a matricellular protein that mediates diverse biological functions. OPN is involved in normal physiological processes and is implicated in the pathogenesis of a variety of disease states, including atherosclerosis, glomerulonephritis, cancer, and several chronic inflammatory diseases. Through interactions with several integrins, OPN mediates cell migration, adhesion, and survival in many cell types. OPN also functions as a Th1 cytokine, promotes cell-mediated immune responses, and plays a role in chronic inflammatory and autoimmune diseases. Besides its function in inflammation, OPN is also a regulator of biomineralization and a potent inhibitor of vascular calcification.
PMCID: PMC2778587  PMID: 19798593
Inflammation; Matricellular protein; Osteopontin
12.  Elevated Osteopontin Levels in Mild Cognitive Impairment and Alzheimer's Disease 
Mediators of Inflammation  2013;2013:615745.
Inflammatory mediators are closely associated with the pathogenesis of neurodegenerative changes in Alzheimer's disease (AD) and mild cognitive impairment (MCI). Osteopontin (OPN) is a proinflammatory cytokine that has been shown to play an important role in various neuroinflammatory diseases. However, the function of OPN in AD and MCI progression is not well defined. Cerebrospinal fluid (CSF) and plasma samples were obtained from 35 AD patients, 31 MCI patients, and 20 other noninflammatory neurologic diseases (OND). Concentrations of OPN in the CSF and plasma were determined by enzyme-linked immunosorbent assay. During a 3-year clinical followup, 13 MCI patients converted to AD (MCI converters), and 18 were clinically stable (MCI nonconverters). CSF OPN concentrations were significantly increased in AD and MCI converters compared to OND, and increased levels of OPN in AD were associated with MMSE score; OPN protein levels both in the CSF and plasma of newly diagnosed AD patients were higher than that of chronical patients. In MCI converters individuals tested longitudinally, both plasma and CSF OPN concentrations were significantly elevated when they received a diagnosis of AD during followup. Further wide-scale studies are necessary to confirm these results and to shed light on the etiopathogenic role of osteopontin in AD.
PMCID: PMC3612435  PMID: 23576854
13.  Secreted Osteopontin Is Highly Polymerized in Human Airways and Fragmented in Asthmatic Airway Secretions 
PLoS ONE  2011;6(10):e25678.
Osteopontin (OPN) is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family and a cytokine with diverse biologic roles. OPN undergoes extensive post-translational modifications, including polymerization and proteolytic fragmentation, which alters its biologic activity. Recent studies suggest that OPN may contribute to the pathogenesis of asthma.
To determine whether secreted OPN (sOPN) is polymerized in human airways and whether it is qualitatively different in asthma, we used immunoblotting to examine sOPN in bronchoalveolar lavage (BAL) fluid samples from 12 healthy and 21 asthmatic subjects (and in sputum samples from 27 healthy and 21 asthmatic subjects). All asthmatic subjects had mild to moderate asthma and abstained from corticosteroids during the study. Furthermore, we examined the relationship between airway sOPN and cellular inflammation.
Principal Findings
We found that sOPN in BAL fluid and sputum exists in polymeric, monomeric, and cleaved forms, with most of it in polymeric form. Compared to healthy subjects, asthmatic subjects had proportionately less polymeric sOPN and more monomeric and cleaved sOPN. Polymeric sOPN in BAL fluid was associated with increased alveolar macrophage counts in airways in all subjects.
These results suggest that sOPN in human airways (1) undergoes extensive post-translational modification by polymerization and proteolytic fragmentation, (2) is more fragmented and less polymerized in subjects with mild to moderate asthma, and (3) may contribute to recruitment or survival of alveolar macrophages.
PMCID: PMC3198733  PMID: 22031818
14.  Osteopontin Regulates Actin Cytoskeleton and Contributes to Cell Proliferation in Primary Erythroblasts* 
The Journal of Biological Chemistry  2008;283(11):6997-7006.
Erythropoietin and stem cell factor are the key cytokines that regulate early stages of erythroid differentiation. However, it remains undetermined whether additional cytokines also play a role in the differentiation program. Here, we report that osteopontin (OPN) is highly expressed and secreted by erythroblasts during differentiation. We also demonstrate that OPN-deficient human and mouse erythroblasts exhibit defects in F-actin filaments, and addition of exogenous OPN to OPN-deficient erythroblasts restored the F-actin filaments in these cells. Furthermore, our studies demonstrate that OPN contributes to erythroblast proliferation. OPN knock-out male mice exhibit lower hematocrit and hemoglobin levels compared with their wild-type counterparts. We also show that OPN mediates phosphorylation or activation of multiple proteins including Rac-1 GTPase and the actin-binding protein, adducin, in human erythroblasts. In addition, we show that the OPN effects include regulation of intracellular calcium in human erythroblasts. Finally, we demonstrate that human erythroblasts expressCD44 and integrins β1 and α4, three known receptors for OPN, and that the integrin β1 receptor is involved in transmitting the proliferative signal. Together these results provide evidence for signal transduction by OPN and contribution to multiple functions during the erythroid differentiation program in human and mouse.
PMCID: PMC3385928  PMID: 18174176
15.  Regulation of T-helper-cell lineage development by osteopontin 
Nature reviews. Immunology  2009;9(2):137-141.
Studies of osteopontin (OPN)-dependent regulation of immune responses have focused on the cytokine activities of the secreted form of this protein. Recent evidence has revealed that an intracellular form of OPN expressed by dendritic cells regulates the expression of pro-inflammatory cytokines and the differentiation of T helper (TH)-cell lineages. In this Opinion article, we discuss the properties of both OPN isoforms and their respective contributions to the immune response. We propose that cell-type-specific expression of secreted and intracellular OPN regulates the development of distinct effector TH cells, including that of TH1 and TH17 cells.
PMCID: PMC2696694  PMID: 19096390
16.  Polyomavirus Middle T Antigen Induces the Transcription of Osteopontin, a Gene Important for the Migration of Transformed Cells▿  
Journal of Virology  2008;82(10):4946-4954.
Middle T antigen (MT) is the principal oncoprotein of murine polyomavirus. Experiments on the acute immediate effects of MT expression on cellular RNA levels showed that expression of osteopontin (OPN) was strongly induced by MT expression. Osteopontin is a protein known to be associated with cancer. It has a role in tumor progression and invasion. Protein analysis confirmed that MT induced the secretion of OPN into the extracellular medium. Expression of antisense OPN RNA had no effect on the growth of MT-transformed cells. However, it had a strong effect on the ability of MT transformants to migrate or to fill a wound. Analysis of MT mutants implicated both the SHC and phosphatidylinositol 3-kinase pathways in OPN induction. Reporter assays showed that MT regulated the OPN promoter through two of its PEA3 (polyoma enhancer activator 3) sites. As critical PEA3 sites are also part of the polyomavirus enhancer, the same signaling important for viral replication also contributes to virally induced metastatic potential.
PMCID: PMC2346735  PMID: 18337582
17.  Neutralization of Osteopontin Inhibits Obesity-Induced Inflammation and Insulin Resistance 
Diabetes  2010;59(4):935-946.
Obesity is associated with a state of chronic low-grade inflammation mediated by immune cells that are primarily located to adipose tissue and liver. The chronic inflammatory response appears to underlie obesity-induced metabolic deterioration including insulin resistance and type 2 diabetes. Osteopontin (OPN) is an inflammatory cytokine, the expression of which is strongly upregulated in adipose tissue and liver upon obesity. Here, we studied OPN effects in obesity-induced inflammation and insulin resistance by targeting OPN action in vivo.
C57BL/6J mice were fed a high-fat diet to induce obesity and were then intravenously treated with an OPN-neutralizing or control antibody. Insulin sensitivity and inflammatory alterations in adipose tissue and liver were assessed.
Interference with OPN action by a neutralizing antibody for 5 days significantly improved insulin sensitivity in diet-induced obese mice. Anti-OPN treatment attenuated liver and adipose tissue macrophage infiltration and inflammatory gene expression by increasing macrophage apoptosis and significantly reducing c-Jun NH2-terminal kinase activation. Moreover, we report OPN as a novel negative regulator for the activation of hepatic signal transducer and activator of transcription 3 (STAT3), which is essential for glucose homeostasis and insulin sensitivity. Consequently, OPN neutralization decreased expression of hepatic gluconeogenic markers, which are targets of STAT3-mediated downregulation.
These findings demonstrate that antibody-mediated neutralization of OPN action significantly reduces insulin resistance in obesity. OPN neutralization partially decreases obesity-associated inflammation in adipose tissue and liver and reverses signal transduction related to insulin resistance and glucose homeostasis. Hence, targeting OPN could provide a novel approach for the treatment of obesity-related metabolic disorders.
PMCID: PMC2844841  PMID: 20107108
18.  Osteopontin Upregulation in Rotavirus-Induced Murine Biliary Atresia Requires Replicating Virus But is Not Necessary for Development of Biliary Atresia 
Virology  2011;417(2):281-292.
Biliary atresia (BA) is a progressive fibro-inflammatory pediatric liver disease in which osteopontin (OPN), a glycoprotein with inflammatory and fibrogenic activity, may play a pathogenic role. The current studies were conducted in a mouse model of rotavirus-induced BA to test the hypotheses that live but not inactivated rotavirus causes antigenemia, upregulation of hepatic OPN expression, and induction of BA and fibrosis; and that OPN is necessary for development of BA. Prolonged or transient antigenemia developed in mice inoculated with live or inactivated virus, respectively, but only live virus upregulated hepatic OPN and caused BA and fibrosis. OPN was expressed in intra- and extrahepatic bile ducts in healthy mice and in mice with BA. OPN-deficient mice, similarly to WT mice, developed BA. Together, these data show that live but not inactivated rotavirus causes upregulation of hepatic OPN expression and BA but that OPN is not necessary for development of BA.
PMCID: PMC3170515  PMID: 21742364
Rotavirus; biliary atresia; osteopontin; antigenemia; fibrosis; cholestasis; pediatrics; liver; bile ducts
19.  Osteopontin/Eta-1 upregulated in Crohn’s disease regulates the Th1 immune response 
Gut  2005;54(9):1254-1262.
Background and aims: The pathogenesis of Crohn’s disease (CD), a chronic inflammatory bowel disease characterised by a Th1 immune response, remains unclear. Osteopontin (OPN) is a phosphoprotein known as an adhesive bone matrix protein. Recent studies have shown that OPN plays an important role in lymphocyte migration, granuloma formation, and interleukin 12 (IL-12) production. The present study investigated expression and the pathophysiological role of OPN in CD.
Methods: Plasma OPN concentration was measured by enzyme linked immunosorbent assay. Expression of OPN in human intestinal mucosa was determined using reverse transcription-polymerase chain reaction and western blot, and localisation of OPN was examined by immunohistochemistry. Expression of integrin β3, an OPN receptor, on lamina propria mononuclear cells (LPMC) was assessed by flow cytometry. Functional activation of OPN in LPMC was investigated by measuring the production of cytokines.
Results: Plasma OPN concentration was significantly higher in patients with CD compared with normal controls or patients with ulcerative colitis (UC). OPN was upregulated in intestinal mucosa from UC and CD patients. OPN producing cells were epithelial or IgG producing plasma cells, or partial macrophages. OPN was detected in areas surrounding granuloma from mucosa in CD. Integrin β3 expressing macrophages infiltrated inflamed mucosa in UC and CD; in contrast, there was no expression of integrin β3 on intestinal macrophages in normal mucosa. OPN induced production of IL-12 from LPMC in CD but not in normal controls or UC.
Conclusions: Increased OPN expression facilitates cytokine production and is closely involved in the Th1 immune response associated with CD.
PMCID: PMC1774642  PMID: 16099792
osteopontin; Crohn’s disease; ulcerative colitis; Th1 immune response
20.  The Role of Osteopontin and Osteopontin Aptamer (OPN-R3) in Fibroblast Activity 
The Journal of Surgical Research  2011;176(1):348-358.
Scarring is believed to be caused by both persistent inflammation and overexuberant fibroblast activation. Osteopontin (OPN) is a cytokine that promotes cell activation. The absence of OPN in vivo reduces dermal scarring. This suggests that OPN is involved in scar formation; however, how OPN exerts these pro-scarring effects is unknown. RNA aptamers are short RNA molecules that bind target proteins with high affinity. The aptamer OPN-R3 (R3) blocks OPN signaling. The role of R3 in preventing dermal fibrosis is unknown.
Fibroblast migration was analyzed with the use of Boyden Chambers and HEMA-3 staining. Inverted confocal microscopy was used to assess fibroblast focal adhesion length. Adhesion was measured by incubating fluorescently stained fibroblasts on OPN coated 96-well plates. CellTiter 96® AQueous Non-Radioactive Cell Proliferation Assay was utilized to investigate the proliferative activity of fibroblasts. Free floating collagen lattices were utilized to assess fibroblast contractility.
Human dermal fibroblasts migrated significantly in response to OPN. OPN did not induce a significant increase in focal adhesion length compared to controls. Adhesion studies demonstrated that OPN increased fibroblast adhesion. Proliferation assays indicate that OPN increased fibroblast growth. OPN increased fibroblast contractility of collagen lattices. The addition of R3 significantly inhibited OPN induced activity.
OPN is associated with scar and exerts pro-scarring effects by increasing cellular migration, adhesion, proliferation, and contractility of human dermal fibroblasts. R3 prevents OPN mediated activity. OPN may be useful for promoting closure of non-healing wounds and the OPN specific aptamer, R3, may be useful for preventing fibrosis.
PMCID: PMC3323744  PMID: 21962803
osteopontin; aptamer; wound healing; fibroblasts
21.  Osteopontin Regulates Ubiquitin-Dependent Degradation of Stat1 in Murine Mammary Epithelial Tumor Cells1 
Neoplasia (New York, N.Y.)  2007;9(9):699-706.
Osteopontin (OPN) is a secreted glycoprotein that mediates cell-matrix interactions and cellular signaling by binding with integrin (primarily αvβ3) and CD44 receptors. OPN regulates cell adhesion, chemotaxis, macrophage-directed IL-10 suppression, stress-dependent angiogenesis, apoptosis prevention, and anchorage-independent growth of tumor cells. However, the molecular mechanisms that define the role of OPN in tumor progression and metastasis are incompletely understood.
In this study, we use a system of 4T1 and 4T07 murine mammary epithelial tumor cell lines that are divergent in both metastatic phenotype and OPN expression. 4T1 expresses OPN and hematogeneously metastasizes, whereas 4T07 does not express OPN and is highly tumorigenic but fails to metastasize.
Our results demonstrate that OPN regulates Stat1 protein degradation through the ubiquitin-proteasome pathway to alter interferon-γ-dependent growth inhibition and p21 expression. We identify Stat-interacting LIM protein as the critical Stat ubiquitin E3 ligase in this setting.
OPN regulates Stat1-dependent functions, such as growth inhibition and p21 expression, in the murine mammary epithelial cells lines 4T1 and 4T07. This relationship between OPN and Stat1 in the context of tumor biology has not been previously examined.
PMCID: PMC1993854  PMID: 17898865
Ubiquitin; SLIM; proteasome; p21; interferon
22.  Osteopontin Splice Variants Differentially Exert Clinicopathological Features and Biological Functions in Gastric Cancer 
Purpose: Gastric cancer (GC) remains a leading cause of death worldwide, and an elevated expression of osteopontin (OPN) may correlate with its poor survival. Alternative splicing of OPN can result in three isoforms, OPN-a, OPN-b and OPN-c. The aim of our current study is to examine the expression pattern and biological functions of OPN splice variants in GC.
Methods: Firstly, we evaluated the expression of OPN splice variants in 7 gastric cell lines, 101 pairs of GC tissues and their adjacent non-tumor tissues by Quantative real-time PCR (QT-PCR). Gain-of-function experiments were subsequently performed to determine their diverse roles in malignant behaviors of GC. Besides, their differential effects on the regulation of crucial downstream molecules were further explored in the anti-apoptotic and pro-metastatic process.
Results: We found that OPN-b is the dominant kind of OPN isoform in GC cell lines. Although the expression levels of three variants were all elevated in GC tissues, increased OPN-b or OPN-c expression could correlate with clinicopathological features. Functional analyses further showed that OPN-b most strongly promoted GC cell survival possibly by regulation of Bcl-2 family proteins and CD44v expressions. Moreover, OPN-c most effectively stimulated GC metastatic activity by increasing secretion of MMP-2, uPa, and IL-8.
Conclusions: Our results suggest that OPN splice variants differentially exert clinicopathological features and biological functions in GC. Therefore, focusing on specific OPN isoform could be a novel direction for developing diagnostic and therapeutic approaches in GC.
PMCID: PMC3535534  PMID: 23289017
OPN splice variants; gastric cancer; clinicopathological feature; biological function; apoptosis; metastasis.
23.  Osteopontin deficiency protects against obesity-induced hepatic steatosis and attenuates glucose production in mice 
Diabetologia  2011;54(8):2132-2142.
Obesity is strongly associated with the development of non-alcoholic fatty liver disease (NAFLD). The cytokine osteopontin (OPN) was recently shown to be involved in obesity-induced adipose tissue inflammation and reduced insulin response. Accumulating evidence links OPN to the pathogenesis of NAFLD. Here we aimed to identify the role of OPN in obesity-associated hepatic steatosis and impaired hepatic glucose metabolism.
Wild-type (WT) and Opn (also known as Spp1) knockout (Opn−/−) mice were fed a high-fat or low-fat diet to study OPN effects in obesity-driven hepatic alterations.
We show that genetic OPN deficiency protected from obesity-induced hepatic steatosis, at least in part, by downregulating hepatic triacylglycerol synthesis. Conversely, absence of OPN promoted fat storage in adipose tissue thereby preventing the obesity-induced shift to ectopic fat accumulation in the liver. Euglycaemic–hyperinsulinaemic clamp studies revealed that insulin resistance and excess hepatic glucose production in obesity were significantly attenuated in Opn−/− mice. OPN deficiency markedly improved hepatic insulin signalling as shown by enhanced insulin receptor substrate-2 phosphorylation and prevented upregulation of the major hepatic transcription factor Forkhead box O1 and its gluconeogenic target genes. In addition, obesity-driven hepatic inflammation and macrophage accumulation was blocked by OPN deficiency.
Our data strongly emphasise OPN as mediator of obesity-associated hepatic alterations including steatosis, inflammation, insulin resistance and excess gluconeogenesis. Targeting OPN action could therefore provide a novel therapeutic strategy to prevent obesity-related complications such as NAFLD and type 2 diabetes.
Electronic supplementary material
The online version of this article (doi:10.1007/s00125-011-2170-0) contains supplementary material, which is available to authorised users.
PMCID: PMC3131508  PMID: 21562757
Gluconeogenesis; High-fat diet; Inflammation; Insulin resistance; Non-alcoholic fatty liver disease
24.  Uterine Micro-Environment and Estrogen-Dependent Regulation of Osteopontin Expression in Mouse Blastocyst 
Embryo implantation is a highly synchronized bioprocess between an activated blastocyst and a receptive uterus. In mice, successful implantation relies on the dynamic interplay of estrogen and progesterone; however, the key mediators downstream of these hormones that act on blastocyst competency and endometrium receptivity acquisition are largely unknown. In this study, we showed that the expression of osteopontin (OPN) in mouse blastocysts is regulated by ovarian estrogen and uterine micro-environment. OPN mRNA is up-regulated in mouse blastocyst on day 4 of pregnancy, which is associated with ovarian estrogen secretion peak. Hormone treatment in vivo demonstrated that OPN expression in a blastocyst is regulated by estrogen through an estrogen receptor (ER). Our results of the delayed and activated implantation model showed that OPN expression is induced after estrogen injection. While estrogen treatment during embryo culture in vitro showed less effect on OPN expression, the tubal ligation model on day 3 of pregnancy confirmed that the regulation of estrogen on OPN expression in blastocyst might, through some specific cytokines, have existed in a uterine micro-environment. Collectively, our study presents that estrogen regulates OPN expression and it may play an important role during embryo implantation by activating blastocyst competence and facilitating the endometrium acceptable for active blastocyst.
PMCID: PMC3742256  PMID: 23852023
implantation; estrogen; uterus; blastocyst; osteopontin
25.  Expression Profile of the Matricellular Protein Osteopontin in Primary Open-Angle Glaucoma and the Normal Human Eye 
The authors identified reduced levels of the matricellular protein osteopontin in primary open-angle glaucoma aqueous humor compared with control. Osteopontin levels are not influenced by latanoprost but may be altered because of a cellular response to increased IOP. The importance of osteopontin and IOP regulation is discussed.
To characterize the role of osteopontin (OPN) in primary open-angle glaucoma (POAG) and normal eyes.
OPN quantification was performed by enzyme-linked immunosorbent assay in aqueous humor (AH) obtained from human donor eyes (POAG and normal) and surgical samples (POAG and elective cataract removal). OPN expression and localization in whole eye tissue sections and primary normal human trabecular meshwork (NTM) cells were studied by Western blot and immunohistochemistry. Latanoprost-free acid (LFA)–treated NTM cells were analyzed for OPN gene and protein expression. Intraocular pressure was measured by tonometry, and central corneal thickness was measured by optical coherence tomography in young OPN−/− and wild-type mice.
OPN levels were significantly reduced in donor POAG AH compared with normal AH (0.54 ± 0.18 ng/μg [n = 8] vs. 0.77 ± 0.23 ng/μg [n = 9]; P = 0.039). A similar trend was observed in surgical AH (1.05 ± 0.31 ng/μg [n = 20] vs. 1.43 ± 0.88 ng/μg [n = 20]; P = 0.083). OPN was present in the trabecular meshwork, corneal epithelium and endothelium, iris, ciliary body, retina, vitreous humor, and optic nerve. LFA increased OPN gene expression, but minimal change in OPN protein expression was observed. No difference in intraocular pressure (17.5 ± 2.0 mm Hg [n = 56] vs. 17.3 ± 1.9 mm Hg [n = 68]) but thinner central corneal thickness (91.7 ± 3.6 μm [n = 50] vs. 99.2 ± 5.5 μm [n = 70]) was noted between OPN−/− and wild-type mice.
OPN is widely distributed in the human eye and was found in lower concentrations in POAG AH. Reduction of OPN in young mice does not affect IOP.
PMCID: PMC3176026  PMID: 21743018

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