Expression and distribution of osteopontin in human tissues: widespread association with luminal epithelial surfaces

Role of osteopontin and its regulation in pancreatic islet

Osteopontin (OPN) is involved in various physiological processes and also implicated in multiple pathological states. It has been suggested that OPN may have a role in type 2 diabetes (T2D) by protecting pancreatic islets and interaction with incretins. However, the regulation and function of OPN in islets, especially in humans, remains largely unexplored. In this study, we performed our investigations on both diabetic mouse model SUR1-E1506K+/+ and islets from human donors. We demonstrated that OPN protein, secretion and gene expression was elevated in the diabetic SUR1-E1506K+/+ islets. We also showed that high glucose and incretins simultaneously stimulated islet OPN secretion. In islets from human cadaver donors, OPN gene expression was elevated in diabetic islets, and externally added OPN significantly increased glucose-stimulated insulin secretion (GSIS) from diabetic but not normal glycemic donors. The increase in GSIS by OPN in diabetic human islets was Ca²⁺ dependent, which was abolished by Ca²⁺-channel inhibitor isradipine. Furthermore, we also confirmed that OPN promoted cell metabolic activity when challenged by high glucose. These observations provided evidence on the protective role of OPN in pancreatic islets under diabetic condition, and may point to novel therapeutic targets for islet protection in T2D.

Non-invasive detection of bladder cancer via expression-targeted gene delivery

BACKGROUND

Because of the time and expense associated with the procedures and possible distress to the patient, cystoscopy or other imaging techniques are typically not used for bladder cancer detection before symptoms become present. Alternatively, commercial assays for urinary tumor markers exist but are marred by low sensitivity and high cost. There is a need for a simple and sensitive means of tumor detection, such as via the analysis of urine.

METHODS

Plasmids encoding the secretable reporter Gaussia Luciferase (G.LUC), under the control of cmv, cox2 or opn promoters, were delivered via polyethylenimine into bladder tumor cells in culture and into the bladders of mice. Expression profiles of the reporter were recorded, the optimal times for reporter detection were determined and the relationship of reporter expression with tumor size was calculated.

RESULTS

In vitro results showed that both the cox2 and opn promoters can drive significant expression of G.LUC in bladder carcinoma cells in a targeted fashion. In vivo results demonstrated that the cox2 promoter caused expression of G.LUC at detectable levels in the urine, with local signal maxima occurring at 48 and 72 h post-transfection. G.LUC levels in the urine had a 24-h periodicity, with the periodicity partly being the result of an agent secreted by tumor cells that served to mask the luciferase signal.

CONCLUSIONS

Having shown tumor specificity and having been calibrated with respect to circadian expression patterns, the detection system shows great promise for future investigation of tumor presence both in the urinary bladder and other models of cancer.

A Potent Tartrate Resistant Acid Phosphatase Inhibitor to Study the Function of TRAP in Alveolar Macrophages

The enzyme tartrate resistant acid phosphatase (TRAP, two isoforms 5a and 5b) is highly expressed in alveolar macrophages, but its function there is unclear and potent selective inhibitors of TRAP are required to assess functional aspects of the protein. We found higher TRAP activity/expression in lungs of patients with chronic obstructive pulmonary disease (COPD) and asthma compared to controls and more TRAP activity in lungs of mice with experimental COPD or asthma. Stimuli related to asthma and/or COPD were tested for their capacity to induce TRAP. Receptor activator of NF-κb ligand (RANKL) and Xanthine/Xanthine Oxidase induced TRAP mRNA expression in mouse macrophages, but only RANKL also induced TRAP activity in mouse lung slices. Several Au(III) coordination compounds were tested for their ability to inhibit TRAP activity and [Au(4,4′-dimethoxy-2,2′-bipyridine)Cl₂][PF₆] (AubipyOMe) was found to be the most potent inhibitor of TRAP5a and 5b activity reported to date (IC50 1.3 and 1.8 μM respectively). AubipyOMe also inhibited TRAP activity in murine macrophage and human lung tissue extracts. In a functional assay with physiological TRAP substrate osteopontin, AubipyOMe inhibited mouse macrophage migration over osteopontin-coated membranes. In conclusion, higher TRAP expression/activity are associated with COPD and asthma and TRAP is involved in regulating macrophage migration.

Lung cancer-associated brain metastasis: Molecular mechanisms and therapeutic options

BACKGROUND

Lung cancer is the most common cause of cancer-related mortality in humans. There are several reasons for this high rate of mortality, including metastasis to several organs, especially the brain. In fact, lung cancer is responsible for approximately 50% of all brain metastases, which are very difficult to manage. Understanding the cellular and molecular mechanisms underlying lung cancer-associated brain metastasis brings up novel therapeutic promises with the hope to ameliorate the severity of the disease. Here, we provide an overview of the molecular mechanisms underlying the pathogenesis of lung cancer dissemination and metastasis to the brain, as well as promising horizons for impeding lung cancer brain metastasis, including the role of cancer stem cells, the blood-brain barrier, interactions of lung cancer cells with the brain microenvironment and lung cancer-driven systemic processes, as well as the role of growth factor/receptor tyrosine kinases, cell adhesion molecules and non-coding RNAs. In addition, we provide an overview of current and novel therapeutic approaches, including radiotherapy, surgery and stereotactic radiosurgery, chemotherapy, as also targeted cancer stem cell and epithelial-mesenchymal transition (EMT)-based therapies, micro-RNA-based therapies and other small molecule or antibody-based therapies. We will also discuss the daunting potential of some combined therapies.

CONCLUSIONS

The identification of molecular mechanisms underlying lung cancer metastasis has opened up new avenues towards their eradication and provides interesting opportunities for future research aimed at the development of novel targeted therapies.

Evaluation of dermal wound healing activity of synthetic peptide SVVYGLR

SVVYGLR peptide (SV peptide) is a 7-amino-acid sequence with angiogenic properties that is derived from osteopontin in the extracellular matrix and promotes differentiation of fibroblasts to myofibroblast-like cells and the production of collagen type Ⅲ by cardiac fibroblasts. However, the effects of SV peptide on dermal cells and tissue are unknown. In this study, we evaluated the effects of this peptide in a rat model of dermal wound healing. The synthetic SV peptide was added to dermal fibroblasts or keratinocytes, and their cellular motility was evaluated. In an in vivo wound healing exeriment, male rats aged 8 weeks were randomly assigned to the SV peptide treatment, non-treated control, or phosphate-buffered saline (PBS) groups. Wound healing was assessed by its repair rate and histological features. Scratch assay and cell migration assays using the Chemotaxicell method showed that SV peptide significantly promoted the cell migration in both fibroblasts and keratinocytes. In contrast the proliferation potency of these cells was not affected by SV peptide. In the rat model, wound healing progressed faster in the SV peptide-treated group than in the control and PBS groups. The histopathological analyses showed that the SV peptide treatment stimulated the migration of fibroblasts to the wound area and increased the number of myofibroblasts. Immunohistochemical staining showed a marked increase of von Willebland factor-positive neomicrovessels in the SV peptide-treated group. In conclusion, SV peptide has a beneficial function to promote wound healing by stimulating granulation via stimulating angiogenesis, cell migration, and the myofibroblastic differentiation of fibroblasts.

SERUM OSTEOPONTIN LEVEL IS ASSOCIATED WITH PRESENCE OF ATRIAL FIBRILLATION IN CALCIFIC AORTIC VALVE STENOSIS

Identification of risk factors associated with presence of atrial fibrillation (AF) in patients with aortic valve stenosis (AS) remains to be unraveled.The aim of the study was to investigate relationship between profibrotic biomarkers and presence of AF in AS patientsMethods. 191 patients (29,8% male, 77,7±0,59 years) with AS (defined as aortic valve area (AVA) ≤ 2,0 sm2) were enrolled in the study. Clinical, echocardiographic and biochemical variables, including serum TGFβ1 and osteopontin levels were compared between 2 groups of patients: with and without AF. Results. 83(36,5%) of AS patients had AF. In logistic regression models independent associations between AVA index (p=0,040), left atrial volume (p=0,021), OPN (р=0,009) and presence of AF were found. Patients with serum OPN level > 10,05 ng/ml had twice more higher AF incidence comparedto patients with serum OPN level ≤ 10,05 ng/ml (53,8% and 29,2%, respectively, p=0,020).Conclusion. Serum OPN level was independently associated with presence of AF in AS patients, thus we speculate on it’s predominant profibrotic role in the left atrium.

Osteopontin: its potential role in cancer of children and young adults

Objective: Osteopontin (OPN) is aglyco-phosphoprotein, involved in tissue remodeling, inflammation and boneresorption. In various adult neoplasms OPN was shown to correlate with cancer progression, invasiveness and metastasis. Aim: to define the role of OPN in malignancies of children and young adults. Material and methods: a structured PubMed and Google Scholar literature analysis based on reports published in English between I'1995 and XII'2015. Results: 14 studies (four on hematological malignancies, four on bone tumors, three on CNS tumors, two on dendritic proliferative diseases and one on renal tumors) were identified. Higher levels of serum and cerebro-spinal fluid OPN protein, and high expressions of OPN mRNA and SPP1 gene were present in more aggressive and advanced childhood malignancies. In children with acute lymphoblastic leukemia with CNS involvement and with atypical teratoid/rhabdoid tumor (AT/RT) and medulloblastoma, the serum and CSF OPN levels reflected tumor bulk and response to therapy, while in children with AT/RT and multisystem Langerhans cell histiocytosis with high-risk organs involvement, high OPN serum levels correlated with poorer survival. To the contrary, in osteosarcoma, high OPN mRNA and SPP1 gene expressions correlated with better survival and good response to chemotherapy. Conclusions: The literature review suggests that OPN may play important roles in the development and progression of selected cancers of children and young adults, including acute lymphoblastic leukemia, malignant gliomas, AT/RT and Langerhans cell histiocytosis. However, limited number of published studies prevents from definite concluding on the clinical utility of OPN as a marker of diagnosis, prognosis and treatment monitoring in these pediatric cancers. Further studies performed in more numerous groups of patients with particular types of cancers of children and young adults are warranted.

Osteopontin attenuates acute gastrointestinal graft-versus-host disease by preventing apoptosis of intestinal epithelial cells

BACKGROUND AND AIMS

Acute graft-versus-host disease (GVHD) is a major complication after allogeneic hematopoietic stem cell transplantation, which often targets gastrointestinal (GI) tract. Osteopontin (OPN) plays an important physiological role in the efficient development of Th1 immune responses and cell survival by inhibiting apoptosis. The role of OPN in acute GI-GVHD is poorly understood. In the present study, we investigated the role of OPN in donor T cells in the pathogenicity of acute GI-GVHD.

METHODS

OPN knockout (KO) mice and C57BL/6 (B6) mice were used as donors, and (C57BL/6 × DBA/2) F1 (BDF1) mice were used as allograft recipients. Mice with acute GI-GVHD were divided into three groups: the control group (BDF1→BDF1), B6 group (B6→BDF1), and OPN-KO group (OPN-KO→BDF1). Bone marrow cells and spleen cells from donors were transplanted to lethally irradiated recipients. Clinical GVHD scores were assessed daily. Recipients were euthanized on day 7 after transplantation, and colons and small intestines were collected for various analyses.

RESULTS

The clinical GVHD score in the OPN-KO group was significantly increased compared with the B6 and control groups. We observed a difference in the severity of colonic GVHD between the OPN-KO group and B6 group, but not small intestinal-GVHD between these groups. Interferon-γ, Tumor necrosis factor-α, Interleukin-17A, and Interleukin-18 gene expression in the OPN-KO group was differed between the colon and small intestine. Flow cytometric analysis revealed that the fluorescence intensity of splenic and colonic CD8 T cells expressing Fas Ligand was increased in the OPN-KO group compared with the B6 group.

CONCLUSION

We demonstrated that the importance of OPN in T cells in the onset of acute GI-GVHD involves regulating apoptosis of the intestinal cell via the Fas-Fas Ligand pathway.

Osteopontin and the dento-osseous pathobiology of X-linked hypophosphatemia

Seven young patients with X-linked hypophosphatemia (XLH, having inactivating PHEX mutations) were discovered to accumulate osteopontin (OPN) at the sites of defective bone mineralization near osteocytes - the so-called hallmark periosteocytic (lacunar) "halos" of XLH. OPN was also localized in the pericanalicular matrix extending beyond the osteocyte lacunae, as well as in the hypomineralized matrix of tooth dentin. OPN, a potent inhibitor of mineralization normally degraded by PHEX, is a member of a family of acidic, phosphorylated, calcium-binding, extracellular matrix proteins known to regulate dental, skeletal, and pathologic mineralization. Associated with the increased amount of OPN (along with inhibitory OPN peptide fragments) in XLH bone matrix, we found an enlarged, hypomineralized, lacuno-canalicular network - a defective pattern of skeletal mineralization that decreases stiffness locally at: i) the cell-matrix interface in the pericellular environment of the mechanosensing osteocyte, and ii) the osteocyte's dendritic network of cell processes extending throughout the bone. Our findings of an excess of inhibitory OPN near osteocytes and their cell processes, and in dentin, spatially correlates with the defective mineralization observed at these sites in the skeleton and teeth of XLH patients. These changes likely contribute to the dento-osseous pathobiology of XLH, and participate in the aberrant bone adaptation and remodeling seen in XLH.

Osteopontin and Mucosal Protection

Protection of mucosal tissues of the oral cavity, intestines, respiratory tract, and urogenital tract from the constant challenge of pathogens is achieved by the combined barrier function of the lining epithelia and specialized immune cells. Recent studies have indicated that osteopontin (OPN) has a pivotal role in the development of immune responses and in the tissue destruction and the subsequent repair processes associated with inflammatory diseases. While expression of OPN is increased in immune cells—including neutrophils, macrophages, T- and B-lymphocytes—and in epithelial, endothelial, and fibroblastic cells of inflamed tissues, deciphering the specific functions of OPN has been difficult. In part, this is due to the broad range of biological activities of OPN that are mediated by multiple receptors which recognize several signaling motifs whose activities are influenced by post-translational modifications and proteolytic processing of OPN. Understanding the role of OPN in mucosal inflammation is further complicated by its contributions to the barrier function of the lining epithelia and the complexity of the specialized mucosal immune system. In an attempt to provide some insights into the involvement of OPN in mucosal diseases, this review summarizes current knowledge of the biological activities of OPN involved in the development of inflammatory responses and in wound healing, and indicates how these activities may affect the protection of mucosal tissues.

Role of Osteopontin in Liver Diseases

Osteopontin (OPN), a multifunctional protein, is involved in numerous pathological conditions including inflammation, immunity, angiogenesis, fibrogenesis and carcinogenesis in various tissues. Extensive studies have elucidated the critical role of OPN in cell signaling such as regulation of cell proliferation, migration, inflammation, fibrosis and tumor progression. In the liver, OPN interacts with integrins, CD44, vimentin and MyD88 signaling, thereby induces infiltration, migration, invasion and metastasis of cells. OPN is highlighted as a chemoattractant for macrophages and neutrophils during injury in inflammatory liver diseases. OPN activates hepatic stellate cells (HSCs) to exert an enhancer in fibrogenesis. The role of OPN in hepatocellular carcinoma (HCC) has also generated significant interests, especially with regards to its role as a diagnostic and prognostic factor. Interestingly, OPN acts an opposing role in liver repair under different pathological conditions. This review summarizes the current understanding of OPN in liver diseases. Further understanding of the pathophysiological role of OPN in cellular interactions and molecular mechanisms associated with hepatic inflammation, fibrosis and cancer may contribute to the development of novel strategies for clinical diagnosis, monitoring and therapy of liver diseases.

Expression kinetics of hepatic progenitor markers in cellular models of human liver development recapitulating hepatocyte and biliary cell fate commitment

Due to the limitations of research using human embryos and the lack of a biological model of human liver development, the roles of the various markers associated with liver stem or progenitor cell potential in humans are largely speculative, and based on studies utilizing animal models and certain patient tissues. Human pluripotent stem cell-based in vitro multistage hepatic differentiation systems may serve as good surrogate models for mimicking normal human liver development, pathogenesis and injury/regeneration studies. Here, we describe the implications of various liver stem or progenitor cell markers and their bipotency (i.e. hepatocytic- and biliary-epithelial cell differentiation), based on the pluripotent stem cell-derived model of human liver development. Future studies using the human cellular model(s) of liver and biliary development will provide more human relevant biological and/or pathological roles of distinct markers expressed in heterogeneous liver stem/progenitor cell populations.

Osteopontin expression is correlated with differentiation and good prognosis in medullary thyroid carcinoma

BACKGROUND

Osteopontin (OPN) or secreted phosphoprotein 1 (SPP1) is a matricellular glycoprotein whose expression is elevated in various types of cancer and has been shown to be involved in tumourigenesis and metastasis in many malignancies, including follicular cell-derived thyroid carcinomas. Its role in C-cell-derived thyroid lesions and tumours remains to be established.

OBJECTIVE

The objective of this study is to clarify the role of OPN expression in the development of medullary thyroid carcinoma (MTC).

METHODS

OPN expression was analysed in a series of 116 MTCs by immunohistochemistry and by qPCR mRNA quantification of the 3 OPN isoforms (OPNa, OPNb and OPNc) in six cases from which fresh frozen tissue was available. Statistical tests were used to evaluate the relationship of OPN expression and the clinicopathological and molecular characteristics of patients and tumours.

RESULTS

OPN expression was detected in 91 of 116 (78.4%) of the MTC. We also observed high OPN expression in C-cell hyperplasia as well as in C-cells scattered in the thyroid parenchyma adjacent to the tumours. OPN expression was significantly associated with smaller tumour size, PTEN nuclear expression and RAS status, and suggestively associated with non-invasive tumours. OPNa isoform was expressed significantly at higher levels in tumours than in non-tumour samples. OPNb and OPNc presented similar levels of expression in all samples. Furthermore, OPNa isoform overexpression was significantly associated with reduced growth and viability in the MTC-derived cell line (TT).

CONCLUSION

The expression of OPN in normal C-cells and C-cell hyperplasia suggests that OPN is a differentiation marker of C-cells, rather than a marker of biological aggressiveness in this setting. At variance with other cancers, OPN expression is associated with good prognostic features in MTC.

Polycystic ovary syndrome is associated with increased osteopontin levels

OBJECTIVE

Osteopontin (OPN) is a multi-functional secreted glycoprotein that plays a crucial role in glucose metabolism and inflammatory process. Growing evidence suggests that there is a link between OPN and ovarian function. However, no such link has yet been found for OPN in polycystic ovary syndrome (PCOS). Our aim was to ascertain whether circulating OPN levels are altered in women with PCOS and to determine whether OPN levels differ between the follicular phase and mid-cycle of the menstrual cycle in eumenorrheic women.

DESIGN AND METHODS

In total, 150 women with PCOS and 150 age- and BMI-matched controls without PCOS were recruited for this prospective observational study. OPN levels were measured using ELISA. Metabolic parameters were also determined.

RESULTS

Circulating OPN levels were significantly elevated in PCOS women compared with controls (69.12±31.59  ng/ml vs 42.66±21.28  ng/ml; P<0.001). OPN levels were significantly higher at mid-cycle than in the follicular phase in eumenorrheic women. OPN was positively correlated with BMI, homeostasis model assessment of insulin resistance (HOMA-IR), free testosterone, and high sensitivity C-reactive protein (hs-CRP). Multivariate logistic regression analyses revealed that the odds ratio (OR) for PCOS was 3.64 for patients in the highest quartile of OPN compared with those in the lowest quartile (OR=3.64; 95% CI=2.42-5.57; P=0.011). Our findings indicate that BMI, HOMA-IR, hs-CRP, and free testosterone are independent factors influencing serum OPN levels and that OPN is an independent predictor for HOMA-IR.

CONCLUSION

PCOS is associated with increased OPN levels.

Pyruvate Kinase M2: A Novel Biomarker for the Early Detection of Acute Kidney Injury

The identification of biomarkers for the early detection of acute kidney injury (AKI) is clinically important. Acute kidney injury (AKI) in critically ill patients is closely associated with increased morbidity and mortality. Conventional biomarkers, such as serum creatinine (SCr) and blood urea nitrogen (BUN), are frequently used to diagnose AKI. However, these biomarkers increase only after significant structural damage has occurred. Recent efforts have focused on identification and validation of new noninvasive biomarkers for the early detection of AKI, prior to extensive structural damage. Furthermore, AKI biomarkers can provide valuable insight into the molecular mechanisms of this complex and heterogeneous disease. Our previous study suggested that pyruvate kinase M2 (PKM2), which is excreted in the urine, is a sensitive biomarker for nephrotoxicity. To appropriately and optimally utilize PKM2 as a biomarker for AKI requires its complete characterization. This review highlights the major studies that have addressed the diagnostic and prognostic predictive power of biomarkers for AKI and assesses the potential usage of PKM2 as an early biomarker for AKI. We summarize the current state of knowledge regarding the role of biomarkers and the molecular and cellular mechanisms of AKI. This review will elucidate the biological basis of specific biomarkers that will contribute to improving the early detection and diagnosis of AKI.

Serum osteopontin level and common carotid artery intima-media wall thickness in psoriasis

BACKGROUND

The association between psoriasis and cardiovascular disease is well documented, but the underlying mechanisms remain unknown. The relationship between osteopontin and psoriasis has been studied. High serum levels of osteopontin are reported in psoriasis, with increased cardiovascular risk factors in these patients.

OBJECTIVES

We evaluate the extent of subclinical atherosclerosis by measuring the mean intima-media wall thickness (MIMT) of the common carotid artery (CCA) in patients with psoriasis and assessing its correlation with osteopontin to identify vascular risk factors associated with psoriasis.

METHODS

Intima-media wall thickness of the CCA and plasma osteopontin were determined in 40 patients and 40 age- and sex-matched healthy control subjects.

RESULTS

Median serum osteopontin was significantly higher in patients with psoriasis than in healthy control subjects. Mean intima-media wall thickness of the CCA was positively associated with plasma osteopontin level (r = 0.47, P < 0.0001), body mass index (r = 0.62, P < 0.0001), age (r = 0.54, P < 0.0001), total cholesterol (r = 0.54, P < 0.0001), and triglycerides (r = 0.65, P < 0.0001).

CONCLUSIONS

This study shows higher levels of plasma osteopontin and MIMT-CCA in psoriasis patients than in healthy controls. This is the first study to show a positive correlation between plasma osteopontin and MIMT-CCA.

Utility of Plasma Osteopontin Levels in Management of Community-Acquired Pneumonia

Osteopontin (OPN) is an essential cytokine involved in immune cell recruitment and an important regulator of inflammation. The purpose of this study was to examine differences in OPN plasma levels between before and after antibiotic treatment in hospitalized adult patients with community-acquired pneumonia (CAP). OPN levels were measured in 93 patients with CAP and 54 healthy controls using a commercial enzyme-linked immunosorbent assay (ELISA). The CURB-65, Pneumonia Severity Index (PSI), and Acute Physiology and Chronic Health Evaluation II (APACHE II) scores were used to determine the CAP severity in patients upon initial hospitalization. A decline in the number of white blood cells (WBCs) and neutrophils, and decreases in the levels of OPN and C-reactive protein (CRP) were observed after antibiotic treatment. Only the plasma level of OPN, but not CRP, was correlated with the severity of CAP based on the PSI (r = 0.514, p < 0.001), CURB-65 (r = 0.396, p < 0.001), and APACHE II scores (r = 0.473, p < 0.001). The OPN level also showed a significant correlation with the length of hospital stay (r = 0.210, p = 0.044). In conclusion, plasma level of OPN may act as diagnostic adjuvant biomarkers for CAP and further play a role in clinical assessment of the severity of CAP, which could potentially guide the development of treatment strategies.

New Findings on Breast Cancer Stem Cells: A Review

Since the introduction of the "cancer stem cell" theory, significant developments have been made in the understanding of cancer and the heterogenic structure of tumors. In 2003, with the isolation of cancer stem cells from the first solid tumor, breast cancer, and recognition of the tumorigenicity of these cells, this theory suggested that the main reason for therapy failure might be the presence of cancer stem cells. This review article describes breast cancer stem cell origin, the related cellular and molecular characteristics, signaling pathways, and therapy resistance mechanisms. The databases PubMed, SCOPUS, and Embase were explored, and articles published on these topics between 1992 and 2015 were investigated. It appears that this small subpopulation of cells, with the capacity for self-renewal and a high proliferation rate, originate from normal stem cells, are identified by specific markers such as CD44(+)/CD24(-/low), and enhance a tumor's capacity for metastasis, invasion, and therapy resistance. Cancer stem cell characteristics depend on their interactions with their microenvironment as well as on the inducing factors and elements. Although uncertainties about breast cancer stem cells exist, many of researchers believe that cancer stem cells should be considered as possible therapeutic targets.

(1)H, (15)N, (13)C resonance assignment of human osteopontin

Osteopontin (OPN) is a 33.7 kDa intrinsically disordered protein and a member of the SIBLING family of proteins. OPN is bearing a signal peptide for secretion into the extracellular space, where it exerts its main physiological function, the control of calcium biomineralization. It is often involved in tumorigenic processes influencing proliferation, migration and survival, as well as the adhesive properties of cancer cells via CD44 and integrin signaling pathways. Here we report the nearly complete NMR chemical shift assignment of recombinant human osteopontin.

Defective Initiation of Liver Regeneration in Osteopontin-Deficient Mice after Partial Hepatectomy due to Insufficient Activation of IL-6/Stat3 Pathway

The initial process in liver regeneration after partial hepatectomy involves the recruitment of immune cells and the release of cytokines. Osteopontin (OPN), a pro-inflammatory protein, plays critical roles in immune cell activation and migration. Although OPN has been implicated in the pathogenesis of many liver diseases, the role of OPN in liver regeneration remains obscure. In the present study, we found that serum and hepatic OPN protein levels were significantly elevated in wild-type (WT) mice after partial hepatectomy (PHx) and that bile ductal epithelia were the major cell source of hepatic OPN. Compared to WT mice, OPN knockout (KO) mice exhibited delayed liver regeneration after PHx. This delay in OPN^-/- mice was attributed to impaired hepatic infiltration of macrophages and neutrophils, decreased serum and hepatic IL-6 levels, and blunted activation of macrophages after PHx. Furthermore, we demonstrate that the attenuated activation of macrophages is at least partially due to decreased hepatic and portal vein LPS levels in OPN^-/- mice. In response to decreased IL-6 levels, the activation of signal transducer and transcription (Stat) 3 was reduced in hepatocytes of OPN^-/- mice compared to WT mice after PHx. Consequently, hepatic activation of the downstream direct targets of IL6/Stat3, such as c-fos, c-jun, and c-myc, was also suppressed post-PHx in OPN^-/- mice compared to WT mice. Collectively, these results support a unique role for OPN during the priming phase of liver regeneration, in which OPN enhances the recruitment of macrophages and neutrophils, and triggers hepatocyte proliferation through Kupffer cell-derived IL-6 release and the downstream activation of Stat3.

Osteopontin Deficiency Accelerates Spontaneous Colitis in Mice with Disrupted Gut Microbiota and Macrophage Phagocytic Activity

BACKGROUND

Osteopontin (OPN) is a multifunctional protein expressed in a variety of tissues and cells. Recent studies revealed increased OPN expression in the inflamed intestinal tissues of patients with inflammatory bowel disease (IBD). The role of OPN in the pathophysiology of IBD, however, remains unclear.

AIMS

To investigate the role of OPN in the development of intestinal inflammation using a murine model of IBD, interleukin-10 knock out (IL-10 KO) mice.

METHODS

We compared the development of colitis between IL-10 KO and OPN/IL-10 double KO (DKO) mice. OPN expression in the colonic tissues of IL-10 KO mice was examined by fluorescence in situ hybridization (FISH) analysis. Enteric microbiota were compared between IL-10 KO and OPN/IL-10 DKO mice by terminal restriction fragment length polymorphism analysis. The effect of OPN on macrophage phagocytic function was evaluated by phagocytosis assay.

RESULTS

OPN/IL-10 DKO mice had an accelerated onset of colitis compared to IL-10 KO mice. FISH analysis revealed enhanced OPN synthesis in the colonic epithelial cells of IL-10 KO mice. OPN/IL-10 DKO mice had a distinctly different enteric bacterial profile with a significantly lower abundance of Clostridium subcluster XIVa and a greater abundance of Clostridium cluster XVIII compared to IL-10 KO mice. Intracellular OPN deletion in macrophages impaired phagocytosis of fluorescence particle-conjugated Escherichia coli in vitro. Exogenous OPN enhanced phagocytosis by OPN-deleted macrophages when administered at doses of 1 to 100 ng/ml, but not 1000 ng/ml.

CONCLUSIONS

OPN deficiency accelerated the spontaneous development of colitis in mice with disrupted gut microbiota and macrophage phagocytic activity.

Suppression of tumor growth in lung cancer xenograft model mice by poly(sorbitol-co-PEI)-mediated delivery of osteopontin siRNA

Small interfering RNA (siRNA)-mediated gene silencing represents a promising strategy for treating diseases such as cancer; however, specific gene silencing requires an effective delivery system to overcome the instability and low transfection efficiency of siRNAs. To address this issue, a polysorbitol-based transporter (PSOT) was prepared by low molecular weight branched polyethylenimine (bPEI) crosslinked with sorbitol diacrylate (SDA). Osteopontin (OPN) gene, which is highly associated with non-small cell lung cancer (NSCLC) was targeted by siRNA therapy using siRNA targeting OPN (siOPN). Characterization study confirmed that PSOT formed compact complexes with siOPN and protected siOPN against degradation by RNase. PSOT/siOPN complexes demonstrated low cytotoxicity and enhanced transfection efficiency in vitro, suggesting that this carrier may be suitable for gene silencing. In the A549 and H460 lung cancer cell lines, PSOT/siOPN complexes demonstrated significant silencing efficiency at both RNA and protein levels. To study in vivo tumor growth suppression, two lung cancer cell-xenograft mouse models were prepared and PSOT/siOPN complexes were delivered into the mice through intravenous injection. The siOPN-treated groups demonstrated significantly reduced OPN expression at both the RNA and protein levels as well as suppression of tumor volume and weight. Taken together, siOPN delivery using PSOT may present an effective and novel therapeutic system for lung cancer treatment.

Osteopontin Potentiates Pulmonary Inflammation and Fibrosis by Modulating IL-17/IFN-γ-secreting T-cell Ratios in Bleomycin-treated Mice

Lung fibrosis is a life-threatening disease caused by overt or insidious inflammatory responses. However, the mechanism of tissue injury-induced inflammation and subsequent fibrogenesis remains unclear. Recently, we and other groups reported that Th17 responses play a role in amplification of the inflammatory phase in a murine model induced by bleomycin (BLM). Osteopontin (OPN) is a cytokine and extracellular-matrix-associated signaling molecule. However, whether tissue injury causes inflammation and consequent fibrosis through OPN should be determined. In this study, we observed that BLM-induced lung inflammation and subsequent fibrosis was ameliorated in OPN-deficient mice. OPN was expressed ubiquitously in the lung parenchymal and bone-marrow-derived components and OPN from both components contributed to pathogenesis following BLM intratracheal instillation. Th17 differentiation of CD4⁺ αβ T cells and IL-17-producing γδ T cells was significantly reduced in OPN-deficient mice compared to WT mice. In addition, Th1 differentiation of CD4⁺ αβ T cells and the percentage of IFN-γ-producing γδ T cells increased. T helper cell differentiation in vitro revealed that OPN was preferentially upregulated in CD4⁺ T cells under Th17 differentiation conditions. OPN expressed in both parenchymal and bone marrow cell components and contributed to BLM-induced lung inflammation and fibrosis by affecting the ratio of pathogenic IL-17/protective IFN-γ T cells.

Vorinostat protects against calcium oxalate-induced kidney injury in mice

The present study aimed to examine the effect of the histone deacetylase inhibitor, vorinostat (SAHA), on renal function in a calcium oxalate crystal mouse model, and to investigate the mechanism underlying the renoprotective effect of SAHA. Calcium oxalate crystal formation was induced in 8 week-old male C57BL/6 mice by administering 100 mg/kg glyoxylate for 7 days. A total of 24 male C57BL/6 mice were randomly divided into a control group and the following experimental groups: 50 mg/kg normal saline + 100 mg/kg glyoxylate; 50 mg/kg dimethyl sulfoxide (DMSO) + 100 mg/kg glyoxylate; and 50 mg/kg SAHA + 100 mg/kg glyoxylate. The mice in each of the experimental groups were injected with the saline, DMSO or SAHA into their abdominal cavities 6 h prior to the glyoxylate injection. The mice were sacrificed after 7 days, following which blood and urine samples were collected. The kidneys were harvested to analyze the levels of calcium concentrations and the levels of malondialdehyde (MDA), superoxide dismutase and glutathione reductase. Immunohistochemical staining and semi-quantitative analyses were performed to detect the expression levels of osteopontin (OPN) and CD44. Renal tubular cell apoptosis was detectedusing a TUNEL assay. The concentrations of calcium and malondialdehyde were significantly decreased in the SAHA group, and calcium oxalate crystals in the kidney tissue and the expression levels of OPN and CD44 in the SAHA group were lower, compared with the other experimental groups. SAHA significantly reduced the urinary excretion of KIM-1 and renal tubular cell apoptosis. In conclusion, SAHA reduced calcium oxalate crystal deposition and protected against kidney injury.

Osteopontin-induced brown adipogenesis from white preadipocytes through a PI3K-AKT dependent signaling

Recent studies have shown that OPN (osteopontin) plays critical roles in cell survival, differentiation, bio-mineralization, cancer and cardiovascular remodeling. However, its roles in the differentiation of brown adipocytes and the underlying mechanisms remain unclear. Therefore, the aim of this study was to investigate the roles of OPN in the brown adipogenesis and the underlying mechanisms. It was shown that the OPN successfully induced the differentiation of 3T3-L1 white preadipocytes into the PRDM16(+) (PRD1-BF1-RIZ1 homologous domain containing 16) and UCP-1(+) (uncoupling protein-1) brown adipocytes in a concentration and time-dependent manner. Also, activation of PI3K (phosphatidylinositol 3-kinase)-AKT pathway was required for the OPN-induced brown adipogenesis. The findings suggest OPN plays an important role in promoting the differentiation of the brown adipocytes and might provide a potential novel therapeutic approach for the treatment of obesity and related disorders.

Mechanisms involved in breast cancer liver metastasis

Liver metastasis is a frequent occurrence in patients with breast cancer; however, the available treatments are limited and ineffective. While liver-specific homing of breast cancer cells is an important feature of metastasis, the formation of liver metastases is not random. Indeed, breast cancer cell factors contribute to the liver microenvironment. Major breakthroughs have been achieved recently in understanding breast cancer liver metastasis (BCLM). The process of liver metastasis consists of multiple steps and involves various factors from breast cancer cells and the liver microenvironment. A further understanding of the roles of breast cancer cells and the liver microenvironment is crucial to guide future work in clinical treatments. In this review we discuss the contribution of breast cancer cells and the liver microenvironment to liver metastasis, with the aim to improve therapeutic efficacy for patients with BCLM.

Microvascular density and vascular endothelial growth factor and osteopontin expression during the implantation window in a controlled ovarian hyperstimulation rat model

Vascular endothelial growth factor (VEGF) and osteopontin (OPN) are suggested to facilitate angiogenesis and vascular remodeling in endometrial receptivity. Determination of the endometrial microvascular density (MVD) is the commonest method used to indirectly assess the levels of vasculogenesis and angiogenesis; however, the associations among VEGF, OPN and MVD remain unclear. Controlled ovarian hyperstimulation (COH) with the gonadotrophin-releasing hormone agonist-long protocol may impair endometrial receptivity, and Traditional Chinese Medicine (TCM) may exert therapeutic effects to relieve this impairment. The aim of the present study was to investigate the effects of COH on implantation biology and pregnancy outcome, and to explore the potential therapeutic role of the TCM Zi Dan Yin (ZDY). Female Sprague Dawley rats were divided into four groups: Control, COH, ZDY and COH + ZDY. On days 3, 4 and 5 of pregnancy (D3, D4 and D5, respectively), endometrial MVD was measured with cluster of differentiation 34 immunohistochemical detection, and VEGF and OPN protein and mRNA expression was detected through western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. On D10, the average number of implantation sites was observed. Subsequent to conceiving and bearing newborn rats, the number of live births from each group was recorded. COH was shown to have adverse effects on implantation and pregnancy outcome. The MVD was found to be significantly increased in the COH group compared with that in the control, ZDY and COH+ZDY groups. The results of the protein and RT-qPCR analysis of VEGF and OPN revealed the same trend. Conversely, ZDY reversed the changes in endometrial MVD, VEGF and OPN, and was indicated to improve uterine receptivity and pregnancy outcome. No significant difference was observed among the control, ZDY and COH + ZDY groups. In conclusion, since the results for MVD and VEGF and OPN expression were consistent, MVD could be used as an alternative approach to identify the period of receptivity in rats.

The osteopontin transgenic mouse is a new model for Sjögren's syndrome

Osteopontin (Opn) is a cytokine involved in both physiological and pathological processes, and is elevated in many autoimmune diseases. Sjögren's syndrome (SS) is an autoimmune disease with a strong female predilection characterized by lymphocytic infiltration of exocrine glands. We hypothesized that Opn contributes to SS pathogenesis. We examined an established SS model and found increased Opn locally and systemically. Next, we examined Opn transgenic (Opn Tg) mice for evidence of SS. Opn Tg animals exhibited lymphocytic infiltration of salivary and lacrimal glands, and Opn co-localized with the infiltrates. Moreover, saliva production was reduced, and SS autoantibodies were observed in the serum of these mice. Finally, female Opn Tg mice showed more severe disease compared to males. Taken together, these data support a role for Opn in SS pathogenesis. We identify a new model of spontaneous SS that recapitulates the human disease in terms of sex predilection, histopathology, salivary deficits, and autoantibodies.

Osteopontin expression in the intestine of chukar partridge (Alectoris chukar, Gray, 1830)

The intestinal mucosa is under continuous attack of microorganisms and is defended by the joint action of epithelial cells and specialized immune cells. Osteopontin (OPN), a member of the Small Integrin-Binding Ligand, N-linked Glycoprotein (SIBLING) family, is an adhesive phosphorylated glyco-protein that is synthesized by a variety of nonimmune and immune cells that is involved in interactions with cells mediating signaling. OPN is especially required for the maintenance of the epithelial barrier. To gain a better understanding of the biology of OPN, in the avian intestinal tract, we examined subcellular localization of OPN in the small and large intestine using immunohistochemistry. Immunostaining for OPN was prominently and significantly detected in the epithelial cells of the small and large intestine. However, intestinal stromal cells of the small intestine and the smooth muscle cells in the wall of the large intestine did not exhibit OPN immunoreactivity. Our results show that the differences between the localizations of OPN in the chukar partridge’s small and large intestine may be associated with functional differences of intestine parts. Therefore, the expression of OPN in the chukar partridge intestine may play a crucial role in barrier function, host defence, and/or secretion.

Gonadotropin regulation and role of ovarian osteopontin in the periovulatory period

Osteopontin (OPN), a secreted glycoprotein, has multiple physiological functions. This study investigated the regulation and roles of OPN in the mouse ovary during the periovulatory stages. Immature female mice were treated with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) to simulate follicle maturation and ovulation. In situ hybridization and real-time RT-PCR were performed to assess expression of Opn in the periovulatory ovary. Granulosa cells (GCs) from PMSG-primed immature mice were cultured with or without hCG in the presence or absence of OPN, and effects on expression of Opn, progesterone synthesis, and vascular endothelial growth factor (VEGF) signaling were assessed by real-time RT-PCR, ELISA, and western blotting analysis. Opn transcripts were significantly upregulated 3 h after hCG treatment, followed by a peak at 16 h, and the transcripts localized to GCs. Incubation with hCG significantly increased quantities of Opn transcripts in GCs and OPN levels in the culture medium at 12 and 24 h. Furthermore, OPN treatment caused a significant increase in the levels of Star protein, P 450 cholesterol side-chain cleavage enzyme (p450scc), 3-beta-hydroxysteroid dehydrogenase (Hsd3b), and progesterone in the culture medium. OPN treatment promoted Vegf expression in GCs, which was significantly suppressed by a phosphoinositide 3-kinase (PI3K) inhibitor. In addition, OPN treatment stimulated phosphorylation of AKT, a downstream PI3K signaling molecule. In conclusion, expression of Opn was upregulated in mouse ovarian GCs in response to a gonadotropin surge through epidermal growth factor receptor signaling, which enhances progesterone synthesis and Vegf expression during the early-luteal phase.

Osteopontin: a leading candidate adhesion molecule for implantation in pigs and sheep

Osteopontin (OPN; also known as Secreted Phosphoprotein 1, SPP1) is a secreted extra-cellular matrix (ECM) protein that binds to a variety of cell surface integrins to stimulate cell-cell and cell-ECM adhesion and communication. It is generally accepted that OPN interacts with apically expressed integrin receptors on the uterine luminal epithelium (LE) and conceptus trophectoderm to attach the conceptus to the uterus for implantation. Research conducted with pigs and sheep has significantly advanced understanding of the role(s) of OPN during implantation through exploitation of the prolonged peri-implantation period of pregnancy when elongating conceptuses are free within the uterine lumen requiring extensive paracrine signaling between conceptus and endometrium. This is followed by a protracted and incremental attachment cascade of trophectoderm to uterine LE during implantation, and development of a true epitheliochorial or synepitheliochorial placenta exhibited by pigs and sheep, respectively. In pigs, implanting conceptuses secrete estrogens which induce the synthesis and secretion of OPN in adjacent uterine LE. OPN then binds to αvβ6 integrin receptors on trophectoderm, and the αvβ3 integrin receptors on uterine LE to bridge conceptus attachment to uterine LE for implantation. In sheep, implanting conceptuses secrete interferon tau that prolongs the lifespan of CL. Progesterone released by CL then induces OPN synthesis and secretion from the endometrial GE into the uterine lumen where OPN binds integrins expressed on trophectoderm (αvβ3) and uterine LE (identity of specific integrins unknown) to adhere the conceptus to the uterus for implantation. OPN binding to the αvβ3 integrin receptor on ovine trophectoderm cells induces in vitro focal adhesion assembly, a prerequisite for adhesion and migration of trophectoderm, through activation of: 1) P70S6K via crosstalk between FRAP1/MTOR and MAPK pathways; 2) MTOR, PI3K, MAPK3/MAPK1 (Erk1/2) and MAPK14 (p38) signaling to stimulate trohectoderm cell migration; and 3) focal adhesion assembly and myosin II motor activity to induce migration of trophectoderm cells. Further large in vivo focal adhesions assemble at the uterine-placental interface of both pigs and sheep and identify the involvement of sizable mechanical forces at this interface during discrete periods of trophoblast migration, attachment and placentation in both species.

Ran GTPase in nuclear envelope formation and cancer metastasis

Ran is a small ras-related GTPase that controls the nucleocytoplasmic exchange of macromolecules across the nuclear envelope. It binds to chromatin early during nuclear formation and has important roles during the eukaryotic cell cycle, where it regulates mitotic spindle assembly, nuclear envelope formation and cell cycle checkpoint control. Like other GTPases, Ran relies on the cycling between GTP-bound and GDP-bound conformations to interact with effector proteins and regulate these processes. In nucleocytoplasmic transport, Ran shuttles across the nuclear envelope through nuclear pores. It is concentrated in the nucleus by an active import mechanism where it generates a high concentration of RanGTP by nucleotide exchange. It controls the assembly and disassembly of a range of complexes that are formed between Ran-binding proteins and cellular cargo to maintain rapid nuclear transport. Ran also has been identified as an essential protein in nuclear envelope formation in eukaryotes. This mechanism is dependent on importin-β, which regulates the assembly of further complexes important in this process, such as Nup107-Nup160. A strong body of evidence is emerging implicating Ran as a key protein in the metastatic progression of cancer. Ran is overexpressed in a range of tumors, such as breast and renal, and these perturbed levels are associated with local invasion, metastasis and reduced patient survival. Furthermore, tumors with oncogenic KRAS or PIK3CA mutations are addicted to Ran expression, which yields exciting future therapeutic opportunities.

Differentiation capacity of mouse dental pulp stem cells into osteoblasts and osteoclasts

OBJECTIVE

Our research attempted to show that mouse dental pulp stem cells (DPSCs) with characters such as accessibility, propagation and higher proliferation rate can provide an improved approach for generate bone tissues. With the aim of finding and comparing the differentiation ability of mesenchymal stem cells derived from DPSCs into osteoblast and osteoclast cells; morphological, molecular and biochemical analyses were conducted.

MATERIALS AND METHODS

In this experimental study, osteoblast and osteoclast differentiation was induced by specific differentiation medium. In order to induce osteoblast differentiation, 50 μg mL(-1) ascorbic acid and 10 mM β-glycerophosphate as growth factors were added to the complete medium consisting alpha-modified Eagle's medium (α-MEM), 15% fetal bovine serum (FBS) and penicillin/streptomycin, while in order to induce the osteoclast differentiation, 10 ng/mL receptor activator of nuclear factor kappa-B ligand (RANKL) and 5 ng/mL macrophage-colony stimulating factor (M-CSF) were added to complete medium. Statistical comparison between the osteoblast and osteoclast differentiated groups and control were carried out using t test.

RESULTS

Proliferation activity of cells was estimated by 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. Statistical results demonstrated significant difference (p<0.05) between the control and osteoblastic induction group, whereas osteoclast cells maintained its proliferation rate (p>0.05). Morphological characterization of osteoblast and osteoclast was evaluated using von Kossa staining and May-Grunwald-Giemsa technique, respectively. Reverse transcription-polymerase chain reaction (RT-PCR) molecular analysis demonstrated that mouse DPSCs expressed Cd146 and Cd166 markers, but did not express Cd31, indicating that these cells belong to mesenchymal stem cells. Osteoblast cells with positive osteopontin (Opn) marker were found after 21 days, whereas this marker was negative for DPSCs. CatK, as an osteoclast marker, was negative in both osteoclast differentiation medium and control group. Biochemical analyses in osteoblast differentiated groups showed alkaline phosphatase (ALP) activity significantly increased on day 21 as compared to control (p<0.05). In osteoclast differentiated groups, tartrate-resistant acid phosphatase (TRAP) activity representing osteoclast biomarker didn't show statistically significant as compared to control (p>0.05).

CONCLUSION

DPSCs have the ability to differentiate into osteoblast, but not into osteoclast.

Expression and regulation of secreted phosphoprotein 1 in the bovine corpus luteum and effects on T lymphocyte chemotaxis

Secreted phosphoprotein 1 (SPP1) in the bovine corpus luteum (CL) regulates cell function during the transitional periods of luteinization and luteal regression. The objectives were to i) characterize SPP1 expression in the CL throughout the estrous cycle, ii) determine factors that regulate SPP1 expression in luteal cells, and iii) examine the role of SPP1 in lymphocyte chemotaxis, proliferation, and function. SPP1 mRNA was greater in fully functional (d10) CL and late cycle (d18) CL compared with developing (d4) CL. Additionally, SPP1 mRNA increased within 1 h and remained elevated 4 and 8 h following induction of luteolysis with prostaglandin (PG)F2α. Expression of the SPP1 receptor, β3 integrin, was not different throughout the estrous cycle but decreased following induction of luteolysis. Expression of CD44 increased during the estrous cycle but did not change during luteal regression. In cultured luteal cells, SPP1 mRNA was upregulated by PGF2α and/or tumor necrosis factor α. Western blots revealed the presence of both full-length SPP1 and multiple cleavage products in cultured luteal cells and luteal tissue. Depletion of endogenous SPP1 did not hinder luteal cell-induced lymphocyte proliferation or lymphocyte phenotype but did inhibit lymphocyte migration toward luteal cells. Based on these data, it is concluded that SPP1 is initially activated to establish and maintain cellular interactions between steroidogenic and nonsteroidogenic cells during the development of the CL. Upon induction of luteolysis, SPP1 serves as a signaling molecule to recruit or activate immune cells to facilitate luteal regression and tissue degradation.

Adipose tissue immunity and cancer

Inflammation and altered immune response are important components of obesity and contribute greatly to the promotion of obesity-related metabolic complications, especially cancer development. Adipose tissue expansion is associated with increased infiltration of various types of immune cells from both the innate and adaptive immune systems. Thus, adipocytes and infiltrating immune cells secrete pro-inflammatory adipokines and cytokines providing a microenvironment favorable for tumor growth. Accumulation of B and T cells in adipose tissue precedes macrophage infiltration causing a chronic low-grade inflammation. Phenotypic switching toward M1 macrophages and Th1 T cells constitutes an important mechanism described in the obese state correlating with increased tumor growth risk. Other possible synergic mechanisms causing a dysfunctional adipose tissue include fatty acid-induced inflammation, oxidative stress, endoplasmic reticulum stress, and hypoxia. Recent investigations have started to unravel the intricacy of the cross-talk between tumor cell/immune cell/adipocyte. In this sense, future therapies should take into account the combination of anti-inflammatory approaches that target the tumor microenvironment with more sophisticated and selective anti-tumoral drugs.

Role of osteopontin in modulation of hydroxyapatite formation

The presence of osteopontin (OPN) at high levels in both mineralized tissues such as bone and ectopic calcifications such as atherosclerotic plaque presents a conundrum: is OPN a promoter or inhibitor of hydroxyapatite (HA) formation? In vitro studies show that OPN adsorbs tightly to HA and is a potent inhibitor of crystal growth. Although the mechanism of the OPN-HA interaction is not fully understood, it is probably electrostatic in nature. Phosphorylation enhances OPN's ability to adsorb to and inhibit the growth of HA crystals, although other anionic groups also contribute to these properties. Recent findings suggest that OPN is an intrinsically unordered protein and that its lack of folded structure facilitates the protein's adsorption by allowing multiple binding geometries and the sequential formation of ionic bonds with Ca(2+) ions of the crystal surface. By analogy with other biominerals, it is likely that adsorption of OPN to HA results in "pinning" of growth steps. The abundance of OPN at sites of ectopic calcification reflects upregulation of the protein in response to crystal formation or even in response to elevated phosphate levels. Therefore, it appears that OPN is one of a group of proteins that function to prevent crystal formation in soft tissues. The role of OPN in bone mineralization, if any, is less clear. However, it is possible that it modulates HA formation, either by preventing crystal growth in "inappropriate" areas such as the osteoid seam or by regulating crystal growth habit (size and shape).

Transgenic mammary epithelial osteopontin (spp1) expression induces proliferation and alveologenesis

Osteopontin (OPN) Spp1 is involved in differentiation of the mammary gland. We engineered mice to overexpress OPN in mammary epithelium and describe an altered mammary phenotype. Three transgenic (Tg) founder lines FVB/N Tg(MMTV-Opn)((1-3BOR)) were propagated after FVB/NJ pronuclear injections. Mammary glands from Tg-OPN mice compared to littermate controls showed, at 4 weeks of age, exaggerated terminal end buds; at 8 and 12 weeks, more numerous and complex ducts with increased luminal protein; and at 16 weeks, increased lobulogenesis. Lactational Tg-OPN mammary glands showed more rapid lobulogenesis and lactational changes with slower gland involution and regression following weaning. Ex vivo lobulogenesis was noticeably increased from organoids of Tg-OPN mice. Immunohistochemistry revealed cytoplasmic OPN accumulation and increased Ki-67 positive mammary epithelial cells in Tg-OPN mammary glands. OPN appears to convey a proliferative stimulus for mammary epithelial cells and alters development and differentiation. These OPN mammary overexpressing mice provide a means to study the role of OPN in cancer progression.

Nephrolithiasis: molecular mechanism of renal stone formation and the critical role played by modulators

Urinary stone disease is an ailment that has afflicted human kind for many centuries. Nephrolithiasis is a significant clinical problem in everyday practice with a subsequent burden for the health system. Nephrolithiasis remains a chronic disease and our fundamental understanding of the pathogenesis of stones as well as their prevention and cure still remains rudimentary. Regardless of the fact that supersaturation of stone-forming salts in urine is essential, abundance of these salts by itself will not always result in stone formation. The pathogenesis of calcium oxalate stone formation is a multistep process and essentially includes nucleation, crystal growth, crystal aggregation, and crystal retention. Various substances in the body have an effect on one or more of the above stone-forming processes, thereby influencing a person's ability to promote or prevent stone formation. Promoters facilitate the stone formation while inhibitors prevent it. Besides low urine volume and low urine pH, high calcium, sodium, oxalate and urate are also known to promote calcium oxalate stone formation. Many inorganic (citrate, magnesium) and organic substances (nephrocalcin, urinary prothrombin fragment-1, osteopontin) are known to inhibit stone formation. This review presents a comprehensive account of the mechanism of renal stone formation and the role of inhibitors/promoters in calcium oxalate crystallisation.

Tissue expression and correlation of a panel of urinary biomarkers following cisplatin-induced kidney injury

In recent years, there has been considerable activity to identify urinary biomarkers of nephrotoxicity as noninvasive measurements with greater sensitivity and specificity than traditional biomarkers, such as serum creatinine and blood urea nitrogen. Our study aimed to use cisplatin-treated rats to evaluate the use of immunohistochemistry directed at multiple urinary biomarkers in kidney tissue. Tissue levels were compared to urinary levels of these biomarkers to demonstrate tissue specificity and sensitivity. These techniques could also be used in studies where urine samples are not available, such as retrospective studies in drug safety testing, to demonstrate the potential utility of using these biomarkers in future preclinical or clinical studies. All of the biomarkers investigated showed either an increase (kidney injury molecule [KIM-1], osteopontin [OPN], and, clusterin) or a decrease (alpha-glutathione S-transferase and trefoil factor 3) except beta 2 microglobulin (β2MG) that showed no significant changes 5 days after 1.0 mg/kg or 2.5 mg/kg cisplatin treatment. All of the biomarkers except β2MG showed utility as tissue biomarkers, but KIM-1 and OPN expression correlated closely with urinary biomarker measurements and reflect tissue damage. Future studies are needed to determine the wider application of these two markers for detecting renal toxicity following administration of other nephrotoxicants.

Osteopontin: participation in inflammation or mucosal protection in inflammatory bowel diseases?

BACKGROUND

Osteopontin (OPN) is associated with the Th1 immune response in inflammatory bowel diseases (IBD). While OPN has been shown to play an important role in maintaining the epithelial barrier, its role in IBD remains unclear.

AIM

The aim of this study was to assess OPN function in patients with IBD and in the mouse colitis model.

METHODS

Osteopontin expression in colonic samples from IBD patients was determined by a semi-quantitative immunohistochemical staining method. Colitis in BALB/c mice was induced by 5 % dextran sodium sulfate (DSS), followed by treatment with salazosulfapyridine (SASP) and infliximab, respectively. The plasma OPN concentration was measured by an enzyme-linked immunosorbent assay. The expression of OPN in colonic tissues was detected by reverse transcriptase PCR, real-time PCR and Western blot, and the localization of OPN was determined by a semi-quantitative immunohistochemical staining method. The immune function of OPN was investigated by measuring the production of cytokines, and the amount of cytokines produced was then used to determine OPN immune functions.

RESULTS

Osteopontin expression in intestinal epithelial cells was significantly lower in IBD patients than in controls, while its expression in lamina propria exudative cells was significantly higher in IBD patients than in controls. In DSS-induced mice, OPN expression in plasma and colonic tissues increased significantly, and this increase was significantly reduced after the mice were treated with SASP and infliximab. OPN promoted the Th1 immune response and strengthened inflammation in the mouse colitis model.

CONCLUSIONS

Our results indicate that OPN plays an important role in the immune response and is also involved in the mucosal protective mechanism in IBD.

Differential expression of secreted phosphoprotein 1 in the motor cortex among primate species and during postnatal development and functional recovery

We previously reported that secreted phosphoprotein 1 (SPP1) mRNA is expressed in neurons whose axons form the corticospinal tract (CST) of the rhesus macaque, but not in the corresponding neurons of the marmoset and rat. This suggests that SPP1 expression is involved in the functional or structural specialization of highly developed corticospinal systems in certain primate species. To further examine this hypothesis, we evaluated the expression of SPP1 mRNA in the motor cortex from three viewpoints: species differences, postnatal development, and functional/structural changes of the CST after a lesion of the lateral CST (l-CST) at the mid-cervical level. The density of SPP1-positive neurons in layer V of the primary motor cortex (M1) was much greater in species with highly developed corticospinal systems (i.e., rhesus macaque, capuchin monkey, and humans) than in those with less developed corticospinal systems (i.e., squirrel monkey, marmoset, and rat). SPP1-positive neurons in the macaque monkey M1 increased logarithmically in layer V during postnatal development, following a time course consistent with the increase in conduction velocity of the CST. After an l-CST lesion, SPP1-positive neurons increased in layer V of the ventral premotor cortex, in which compensatory changes in CST function/structure may occur, which positively correlated with the extent of finger dexterity recovery. These results further support the concept that the expression of SPP1 may reflect functional or structural specialization of highly developed corticospinal systems in certain primate species.

Osteopontin Expression in Patients with Hepatolith

To investigate the role of osteopontin (OPN) in the formation of hepatolith, we have immunohistochemically studied the involvement of OPN in hepatolithiasis in the intrahepatic bile ducts and the intramural and extramural glands, and in stones. In our hospital, 17 hepatic resections for hepatolithiasis were carried out from June 2006 to October 2009. Immunohistochemistry was performed on 17 liver specimens with hepatolith and on 24 control liver specimens without hepatolith. We compared the osetopontin expression in the epithelia of the intrahepatic bile ducts and peribiliary glands or periglandular macrophages. Staining for OPN was positive in the cytoplasm of the epithelial cells of stone-containing intrahepatic bile ducts and the intramural and extramural glands, and in stones. But there were no significant differences between the hepatolithiasis group and the control group for the OPN immunoreactivity of the luminal surface of the epithelial cells of the intrahepatic bile ducts and intramural and extramural glands. The stone-containing intrahepatic bile ducts were infiltrated by macrophages that showed intense staining for OPN. The core and matrix of the stones showed OPN immunoreactivity. The degree of OPN from the cytoplasm of the epithelia of the intrahepatic bile ducts and peribiliary glands or periglandular macrophages was different between hepatolithiasis and control groups. Our result suggests that the OPN from the intrahepatic bile ducts and peribiliary glands plays a role in the formation of intrahepatic stone.