Osteopontin expression in cardiovascular diseases

Matricellular proteins in atherosclerosis development

The extracellular matrix (ECM) is an intricate network composed of various multi-domain macromolecules like collagen, proteoglycans, and fibronectin, etc., that form a structurally stable composite, contributing to the mechanical properties of tissue. However, matricellular proteins are non-structural, secretory extracellular matrix proteins, which modulate various cellular functions via interacting with cell surface receptors, proteases, hormones, and cell-matrix. They play essential roles in maintaining tissue homeostasis by regulating cell differentiation, proliferation, adhesion, migration, and several signal transduction pathways. Matricellular proteins display a broad functionality regulated by their multiple structural domains and their ability to interact with different extracellular substrates and/or cell surface receptors. The expression of these proteins is low in adults, however, gets upregulated following injuries, inflammation, and during tumor growth. The marked elevation in the expression of these proteins during atherosclerosis suggests a positive association between their expression and atherosclerotic lesion formation. The role of matricellular proteins in atherosclerosis development has remained an area of research interest in the last two decades and studies revealed these proteins as important players in governing vascular function, remodeling, and plaque formation. Despite extensive research, many aspects of the matrix protein biology in atherosclerosis are still unknown and future studies are required to investigate whether targeting pathways stimulated by these proteins represent viable therapeutic approaches for patients with atherosclerotic vascular diseases. This review summarizes the characteristics of distinct matricellular proteins, discusses the available literature on the involvement of matrix proteins in the pathogenesis of atherosclerosis and suggests new avenues for future research.

The Role of Extracellular Matrix Proteins in Breast Cancer

The extracellular matrix is a structure composed of many molecules, including fibrillar (types I, II, III, V, XI, XXIV, XXVII) and non-fibrillar collagens (mainly basement membrane collagens: types IV, VIII, X), non-collagenous glycoproteins (elastin, laminin, fibronectin, thrombospondin, tenascin, osteopontin, osteonectin, entactin, periostin) embedded in a gel of negatively charged water-retaining glycosaminoglycans (GAGs) such as non-sulfated hyaluronic acid (HA) and sulfated GAGs which are linked to a core protein to form proteoglycans (PGs). This highly dynamic molecular network provides critical biochemical and biomechanical cues that mediate the cell–cell and cell–matrix interactions, influence cell growth, migration and differentiation and serve as a reservoir of cytokines and growth factors’ action. The breakdown of normal ECM and its replacement with tumor ECM modulate the tumor microenvironment (TME) composition and is an essential part of tumorigenesis and metastasis, acting as key driver for malignant progression. Abnormal ECM also deregulate behavior of stromal cells as well as facilitating tumor-associated angiogenesis and inflammation. Thus, the tumor matrix modulates each of the classically defined hallmarks of cancer promoting the growth, survival and invasion of the cancer. Moreover, various ECM-derived components modulate the immune response affecting T cells, tumor-associated macrophages (TAM), dendritic cells and cancer-associated fibroblasts (CAF). This review article considers the role that extracellular matrix play in breast cancer. Determining the detailed connections between the ECM and cellular processes has helped to identify novel disease markers and therapeutic targets.

Osteopontin accumulates in basal deposits of human eyes with age-related macular degeneration and may serve as a biomarker of aging

A common clinical phenotype of several neurodegenerative and systemic disorders including Alzheimer's disease and atherosclerosis is the abnormal accumulation of extracellular material, which interferes with routine cellular functions. Similarly, patients with age-related macular degeneration (AMD), the leading cause of vision loss among the aged population, present with extracellular lipid- and protein-filled basal deposits in the back of the eye. While the exact mechanism of growth and formation of these deposits is poorly understood, much has been learned from investigating their composition, providing critical insights into AMD pathogenesis, prevention, and therapeutics. We identified human osteopontin (OPN), a phosphoprotein expressed in a variety of tissues in the body, as a newly discovered component of basal deposits in AMD patients, with a distinctive punctate staining pattern. OPN expression within these lesions, which are associated with AMD disease progression, were found to co-localize with abnormal calcium deposition. Additionally, OPN puncta colocalized with an AMD risk-associated complement pathway protein, but not with apolipoprotein E or vitronectin, two other well-established basal deposit components. Mechanistically, we found that retinal pigment epithelial cells, cells vulnerable in AMD, will secrete OPN into the extracellular space, under oxidative stress conditions, supporting OPN biosynthesis locally within the outer retina. Finally, we report that OPN levels in plasma of aged (non-AMD) human donors were significantly higher than levels in young (non-AMD) donors, but were not significantly different from donors with the different clinical subtypes of AMD. Collectively, our study defines the expression pattern of OPN in the posterior pole as a function of disease, and its local expression as a potential histopathologic biomarker of AMD.

Both Full-Length and Protease-Cleaved Products of Osteopontin Are Elevated in Infectious Diseases

Circulating full-length osteopontin (FL-OPN) is elevated in plasma from patients with various infectious diseases, such as adult T-cell leukemia, Mycobacterium tuberculosis (TB), hepatitis virus infection, leptospirosis, acquired immune deficiency syndrome (AIDS), AIDS/TB, and coronavirus disease 2019 (COVID-19). Proteolysis of OPN by thrombin, matrix metalloproteases, caspase 8/3, cathepsin D, plasmin, and enterokinase generates various cleaved OPNs with a variety of bioactivities by binding to different target cells. Moreover, OPN is susceptible to gradual proteolysis. During inflammation, one of the cleaved fragments, N-terminal thrombin-cleaved OPN (trOPN or OPN-Arg¹⁶⁸ [OPN-R]), induces dendritic cell (DC) adhesion. Further cleavage by carboxypeptidase B2 or carboxypeptidase N removes Arg¹⁶⁸ from OPN-R to OPN-Leu¹⁶⁷ (OPN-L). Consequently, OPN-L decreases DC adhesion. In particular, the differences in plasma level over time are observed between FL-OPN and its cleaved OPNs during inflammation. We found that the undefined OPN levels (mixture of FL-OPN and cleaved OPN) were elevated in plasma and reflected the pathology of TB and COVID-19 rather than FL-OPN. These infections are associated with elevated levels of various proteases. Inhibition of the cleavage or the activities of cleaved products may improve the outcome of the therapy. Research on the metabolism of OPN is expected to create new therapies against infectious diseases.

Regulatory role of mammalian target of rapamycin signaling in exosome secretion and osteogenic changes in smooth muscle cells lacking acid ceramidase gene

Acid ceramidase (murine gene code: Asah1) (50 kDa) belongs to N-terminal nucleophile hydrolase family. This enzyme is located in the lysosome, which mediates conversion of ceramide (CER) into sphingosine and free fatty acids at acidic pH. CER plays an important role in intracellular sphingolipid metabolism and its increase causes inflammation. The mammalian target of rapamycin complex 1 (mTORC1) signaling on late endosomes (LEs)/lysosomes may control cargo selection, membrane biogenesis, and exosome secretion, which may be fine controlled by lysosomal sphingolipids such as CER. This lysosomal-CER-mTOR signaling may be a crucial molecular mechanism responsible for development of arterial medial calcification (AMC). Torin-1 (5 mg/kg/day), an mTOR inhibitor, significantly decreased aortic medial calcification accompanied with decreased expression of osteogenic markers like osteopontin (OSP) and runt-related transcription factor 2 (RUNX2) and upregulation of smooth muscle 22α (SM22-α) in mice receiving high dose of Vitamin D (500 000 IU/kg/day). Asah1^fl/fl /SM^Cre mice had markedly increased co-localization of mTORC1 with lysosome-associated membrane protein-1 (Lamp-1) (lysosome marker) and decreased co-localization of vacuolar protein sorting-associated protein 16 (VPS16) (a multivesicular bodies [MVBs] marker) with Lamp-1, suggesting mTOR activation caused reduced MVBs interaction with lysosomes. Torin-1 significantly reduced the co-localization of mTOR vs Lamp-1, increased lysosome-MVB interaction which was associated with reduced accumulation of CD63 and annexin 2 (exosome markers) in the coronary arterial wall of mice. Using coronary artery smooth muscle cells (CASMCs), P_i -stimulation significantly increased p-mTOR expression in Asah1^fl/fl /SM^Cre CASMCs as compared to WT/WT cells associated with increased calcium deposition and mineralization. Torin-1 blocked P_i -induced calcium deposition and mineralization. siRNA mTOR and Torin-1 significantly reduce co-localization of mTORC1 with Lamp-1, increased VPS16 vs Lamp-1 co-localization in P_i -stimulated CASMCs, associated with decreased exosome release. Functionally, Torin-1 significantly reduces arterial stiffening as shown by restoration from increased pulse wave velocity and decreased elastin breaks. These results suggest that lysosomal CER-mTOR signaling may play a critical role for the control of lysosome-MVB interaction, exosome secretion and arterial stiffening during AMC.

Plasma and follicular fluid osteopontin levels during ovarian cycle and their correlation with follicular fluid vascular endothelial growth factor levels

Osteopontin (OPN) is a multifunctional secreted glycoprotein. We evaluated OPN concentrations in blood and follicular fluid (FF) during the ovarian cycle and their relationship with the production of vascular endothelial growth factor (VEGF), which is involved in the pathophysiology of ovarian hyperstimulation syndrome (OHSS). Twenty-two women undergoing in vitro fertilization (minimal stimulation protocol with clomiphene citrate) were enrolled. Samples were collected (a) on the third day of withdrawal bleeding, (b) 2 days before oocyte retrieval, and (c) on the day of oocyte retrieval. FF was collected during oocyte retrieval. The OPN concentration in each specimen and the VEGF concentration in FF was measured by enzyme-linked immunosorbent assays. Plasma OPN concentrations were (in ng/mL): (a) 416 ± 37.2, (b) 378 ± 35.8, and (c) 390 ± 40.0, with no significant differences between the groups. The OPN concentration in FF was 106 ± 13.4 ng/mL. A positive correlation was found between OPN concentrations in FF and plasma samples. A positive correlation was also found between plasma OPN and FF VEGF concentrations, irrespective of the blood-sampling period. Plasma OPN concentration is suggested to reflect the FF VEGF level at oocyte retrieval and maybe a novel clinical marker for predicting the risk for OHSS.

Apolipoprotein D

ApoD is a 25 to 30 kDa glycosylated protein, member of the lipocalin superfamily. As a transporter of several small hydrophobic molecules, its known biological functions are mostly associated to lipid metabolism and neuroprotection. ApoD is a multi-ligand, multi-function protein that is involved lipid trafficking, food intake, inflammation, antioxidative response and development and in different types of cancers. An important aspect of ApoD's role in lipid metabolism appears to involve the transport of arachidonic acid, and the modulation of eicosanoid production and delivery in metabolic tissues. ApoD expression in metabolic tissues has been associated positively and negatively with insulin sensitivity and glucose homeostasis in a tissue dependent manner. ApoD levels rise considerably in association with aging and neuropathologies such as Alzheimer's disease, stroke, meningoencephalitis, moto-neuron disease, multiple sclerosis, schizophrenia and Parkinson's disease. ApoD is also modulated in several animal models of nervous system injury/pathology.

Abnormal Lysosomal Positioning and Small Extracellular Vesicle Secretion in Arterial Stiffening and Calcification of Mice Lacking Mucolipin 1 Gene

Recent studies have shown that arterial medial calcification is mediated by abnormal release of exosomes/small extracellular vesicles from vascular smooth muscle cells (VSMCs) and that small extracellular vesicle (sEV) secretion from cells is associated with lysosome activity. The present study was designed to investigate whether lysosomal expression of mucolipin-1, a product of the mouse Mcoln1 gene, contributes to lysosomal positioning and sEV secretion, thereby leading to arterial medial calcification (AMC) and stiffening. In Mcoln1-/- mice, we found that a high dose of vitamin D (Vit D; 500,000 IU/kg/day) resulted in increased AMC compared to their wild-type littermates, which was accompanied by significant downregulation of SM22-α and upregulation of RUNX2 and osteopontin in the arterial media, indicating a phenotypic switch to osteogenic. It was also shown that significantly decreased co-localization of lysosome marker (Lamp-1) with lysosome coupling marker (Rab 7 and ALG-2) in the aortic wall of Mcoln1-/- mice as compared to their wild-type littermates. Besides, Mcoln1-/- mice showed significant increase in the expression of exosome/ sEV markers, CD63, and annexin-II (AnX2) in the arterial medial wall, accompanied by significantly reduced co-localization of lysosome marker (Lamp-1) with multivesicular body (MVB) marker (VPS16), suggesting a reduction of the lysosome-MVB interactions. In the plasma of Mcoln1-/- mice, the number of sEVs significantly increased as compared to the wild-type littermates. Functionally, pulse wave velocity (PWV), an arterial stiffening indicator, was found significantly increased in Mcoln1-/- mice, and Vit D treatment further enhanced such stiffening. All these data indicate that the Mcoln1 gene deletion in mice leads to abnormal lysosome positioning and increased sEV secretion, which may contribute to the arterial stiffness during the development of AMC.

Arterial Medial Calcification through Enhanced small Extracellular Vesicle Release in Smooth Muscle-Specific Asah1 Gene Knockout Mice

Arterial medial calcification (AMC) involves an increased small extracellular vesicle (sEV) secretion and apatite calcium precipitation in the arterial wall. The mechanisms mediating AMC remain poorly understood. In the present study, smooth muscle-specific acid ceramidase (Ac) gene knockout mice (Asah1^fl/fl/SM^Cre) were used to demonstrate the role of lysosomal ceramide signaling pathway in AMC. Asah1^fl/fl/SM^Cre mice were found to have more severe AMC in both aorta and coronary arteries compared to their littermates (Asah1^fl/fl/SM^wt and WT/WT mice) after receiving a high dose vitamin D. These mice also had pronounced upregulation of osteopontin and RUNX2 (osteogenic markers), CD63, AnX2 (sEV markers) and ALP expression (mineralization marker) in the arterial media. In cultured coronary arterial smooth muscle cells (CASMCs) from Asah1^fl/fl/SM^Cre mice, high dose of P_i led to a significantly increased calcium deposition, phenotypic change and sEV secretion compared to WT CASMCs, which was associated with reduced lysosome-multivesicular body (MVB) interaction. Also, GW4869, sEV release inhibitor decreased sEV secretion and calcification in these cells. Lysosomal transient receptor potential mucolipin 1 (TRPML1) channels regulating lysosome interaction with MVBs were found remarkably inhibited in Asah1^fl/fl/SM^Cre CASMCs as shown by GCaMP3 Ca²⁺ imaging and Port-a-Patch patch clamping of lysosomes. Lysosomal Ac in SMCs controls sEV release by regulating lysosomal TRPML1 channel activity and lysosome-MVB interaction, which importantly contributes to phenotypic transition and AMC.

Medial calcification in the arterial wall of smooth muscle cell-specific Smpd1 transgenic mice: A ceramide-mediated vasculopathy

Arterial medial calcification (AMC) is associated with crystallization of hydroxyapatite in the extracellular matrix and arterial smooth muscle cells (SMCs) leading to reduced arterial compliance. The study was performed to test whether lysosomal acid sphingomyelinase (murine gene code: Smpd1)-derived ceramide contributes to the small extracellular vesicle (sEV) secretion from SMCs and consequently leads to AMC. In Smpd1trg /SMcre mice with SMC-specific overexpression of Smpd1 gene, a high dose of Vit D (500 000 IU/kg/d) resulted in increased aortic and coronary AMC, associated with augmented expression of RUNX2 and osteopontin in the coronary and aortic media compared with their littermates (Smpd1trg /SMwt and WT/WT mice), indicating phenotypic switch. However, amitriptyline, an acid sphingomyelinase (ASM) inhibitor, reduced calcification and reversed phenotypic switch. Smpd1trg /SMcre mice showed increased CD63, AnX2 and ALP levels in the arterial wall, accompanied by reduced co-localization of lysosome marker (Lamp-1) with multivesicular body (MVB) marker (VPS16), a parameter for lysosome-MVB interaction. All these changes related to lysosome fusion and sEV release were substantially attenuated by amitriptyline. Increased arterial stiffness and elastin disorganization were found in Smpd1trg /SMcre mice as compared to their littermates. In cultured coronary arterial SMCs (CASMCs) from Smpd1trg /SMcre mice, increased Pi concentrations led to markedly increased calcium deposition, phenotypic change and sEV secretion compared with WT CASMCs, accompanied by reduced lysosome-MVB interaction. However, amitriptyline prevented these changes in Pi -treated CASMCs. These data indicate that lysosomal ceramide plays a critical role in phenotype change and sEV release in SMCs, which may contribute to the arterial stiffness during the development of AMC.

Bone Mineral Density as a Predictor of Atherogenic Indexes of Cardiovascular Disease, Especially in Nonobese Adults

Purpose

This study is aimed at determining whether bone mineral density (BMD) values are related to atherogenic indexes (AIs) and could predict the risk of cardiovascular disease (CVD) in southern Taiwanese adults.

Methods

Medical records of 3249 adults who underwent health examinations between June 2014 and February 2018 at a regional hospital in southern Taiwan were reviewed. Data collected included health history, anthropomorphic characteristics, exercise habits, diets (vegetarian or nonvegetarian), clinical laboratory results (lipid profile, systemic blood pressure (SBP), glucose level, creatinine (Cre) level, and hemoglobin (Hb) level), and bone mineral density (BMD), which were used to identify the associations of these parameters, especially BMD, with lipid profile and calculated AIs through simple and multiple linear regressions.

Results

The mean age of the patients was 58.0 years, and 71.4% were male. Body mass index (BMI), SBP, glucose level, Cre level, Hb level, and all BMD values were positively correlated with triglyceride (TG) level and AIs and were negatively correlated with high-density lipoprotein cholesterol (HDL-C) level. The significant positive correlations of BMD at all the measured sites with AIs remained after adjusting for age, sex, SBP, glucose level, Cre level, Hb level, smoking, exercise habits, and vegetarian state. The expanded adjusting model for TG/HDL-C remained significant at all the BMD measured sites in nonobese men, at bilateral femoral neck and total hips in nonobese women, and at the bilateral total hips in obese women.

Conclusions

AIs are predictive markers for CVD, and BMD values are predictors of AIs, especially the novel AI, i.e., TG/HDL-C ratio, in nonobese adult men and women after dividing the patients into subgroups to eliminate the effect of BMI as a confounding factor. Thus, BMD values could predict AIs of CVD, especially in nonobese adults.

Unique transmembrane domain interactions differentially modulate integrin αvβ3 and αIIbβ3 function

Lateral transmembrane (TM) helix-helix interactions between single-span membrane proteins play an important role in the assembly and signaling of many cell-surface receptors. Often, these helices contain two highly conserved yet distinct interaction motifs, arranged such that the motifs cannot be engaged simultaneously. However, there is sparse experimental evidence that dual-engagement mechanisms play a role in biological signaling. Here, we investigate the function of the two conserved interaction motifs in the TM domain of the integrin β3-subunit. The first motif uses reciprocating "large-large-small" amino acid packing to mediate the interaction of the β3 and αIIb TM domains and maintain the inactive resting conformation of the platelet integrin αIIbβ3. The second motif, S-x₃-A-x₃-I, is a variant of the classical "G-x₃-G" motif. Using site-directed mutagenesis, optical trap-based force spectroscopy, and molecular modeling, we show that S-x₃-A-x₃-I does not engage αIIb but rather mediates the interaction of the β3 TM domain with the TM domain of the αv-subunit of the integrin αvβ3. Like αIIbβ3, αvβ3 on circulating platelets is inactive, and in the absence of platelet stimulation is unable to interact with components of the subendothelial matrix. However, disrupting any residue in the β3 S-x₃-A-x₃-I motif by site-directed mutations is sufficient to induce αvβ3 binding to the αvβ3 ligand osteopontin and to the monoclonal antibody WOW-1. Thus, the β3-integrin TM domain is able to engage in two mutually exclusive interactions that produce alternate α-subunit pairing, creating two integrins with distinct biological functions.

Osteopontin and its spatiotemporal relationship with glial cells in the striatum of rats treated with mitochondrial toxin 3-nitropropionic acid: possible involvement in phagocytosis

Background

Osteopontin (OPN, SPP1) is upregulated in response to acute brain injury, and based on its immunoreactivity, two distinct forms have been identified: intracellular OPN within brain macrophages and small granular OPN, identified as OPN-coated degenerated neurites. This study investigates the spatiotemporal relationship between punctate OPN deposition and astroglial and microglial reactions elicited by 3-nitropropionic acid (3-NP).

Methods

Male Sprague-Dawley rats were intraperitoneally injected with mitochondrial toxin 3-NP and euthanized at 3, 7, 14, and 28 days. Quantitative and qualitative light and electron microscopic techniques were used to assess the relationship between OPN and glial cells. Statistical significance was determined by Student’s t test or a one-way analysis of variance followed by Tukey’s multiple comparisons test.

Results

Punctate OPN-immunoreactive profiles were synthesized and secreted by amoeboid-like brain macrophages in the lesion core, but not by reactive astrocytes and activated microglia with a stellate shape in the peri-lesional area. Punctate OPN accumulation was detected only in the lesion core away from reactive astrocytes in the peri-lesional area at day 3, but had direct contact with, and even overlapped with astroglial processes at day 7. The distance between the OPN-positive area and the astrocytic scar significantly decreased from days 3 to 7. By days 14 and 28 post-lesion, when the glial scar was fully formed, punctate OPN distribution mostly overlapped with the astrocytic scar. Three-dimensional reconstructions and quantitative image analysis revealed numerous granular OPN puncta inside the cytoplasm of reactive astrocytes and brain macrophages. Reactive astrocytes showed prominent expression of the lysosomal marker lysosomal-associated membrane protein 1, and ultrastructural analysis confirmed OPN-coated degenerating neurites inside astrocytes, suggesting the phagocytosis of OPN puncta by reactive astrocytes after injury.

Conclusions

Punctate OPN-immunoreactive profiles corresponded to OPN-coated degenerated neurites, which were closely associated with, or completely engulfed by, the reactive astrocytes forming the astroglial scar in 3-NP lesioned striatum, suggesting that OPN may cause astrocytes to migrate towards these degenerated neurites in the lesion core to establish physical contact with, and possibly, to phagocytose them. Our results provide novel insights essential to understanding the recovery and repair of the central nervous system tissue.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1489-1) contains supplementary material, which is available to authorized users.

Osteopontin Attenuates Secondary Neurodegeneration in the Thalamus after Experimental Stroke

Cortical cerebral ischemia elicits neuroinflammation as well as secondary neuronal degeneration in remote areas. Locally distinct and specific secondary neurodegeneration affecting thalamic nuclei connected to cortical areas highlights such processes. Osteopontin (OPN) is a cytokine-like glycoprotein that is excreted in high amounts after cerebral ischemia and exerts various immunomodulatory functions. We here examined putative protective effects of OPN in secondary thalamic degeneration. We subjected male Wistar rats to photothrombosis and subsequently injected OPN or placebo intracerebroventricularly. Immunohistochemical and fluorescence staining was used to detect the extent of neuronal degeneration and microglia activation. Ex vivo autoradiography with radiotracers available for human in vivo PET studies, i.e., CIS-4-[¹⁸F]Fluor-D-Proline (D-cis-[¹⁸F]FPRO), and [6-³H]thymidine ([³H]thymidine), confirmed degeneration and proliferation, respectively. We found secondary neurodegeneration in the thalamus characterized by microglial activation and neuronal loss. Neuronal loss was restricted to areas of microglial infiltration. Treatment with OPN significantly decreased neurodegeneration, inflammation and microglial proliferation. Microglia displayed morphological signs of activation without expressing markers of M1 or M2 polarization. D-CIS-[¹⁸F]FPRO-uptake mirrored attenuated degeneration in OPN-treated animals. Notably, [³H]thymidine and BrdU-staining revealed increased stem cell proliferation after treatment with OPN. The data suggest that OPN is able to ameliorate secondary neurodegeneration in thalamic nuclei. These effects can be visualized by radiotracers D-CIS-[¹⁸F]FPRO and [³H]thymidine, opening new vistas for translational studies. Graphical Abstract Intracerebroventricular injection of osteopontin attenuates thalamic degeneration after cortical ischemia (pink area). Disruption of thalamocortical connections (blue) and degeneration of thalamic nuclei (encircled) leads to microglia activation. Osteopontin protects from both neurodegeneration and microglia activation as assessed by histological analysis and autoradiograpic studies.

Bioluminescence imaging visualizes osteopontin-induced neurogenesis and neuroblast migration in the mouse brain after stroke

Background

Osteopontin (OPN), an acidic phosphoglycoprotein, is upregulated in the brain after cerebral ischemia. We previously reported that OPN supports migration, survival, and proliferation of neural stem cells (NSC) in primary cell culture, as well as their differentiation into neurons. We here analyzed the effects of OPN on neuroblasts in vivo in the context of cerebral ischemia.

Methods

Transgenic mice expressing luciferase under the control of the neuroblast-specific doublecortin (DCX)-promoter, allowing visualization of neuroblasts in vivo using bioluminescence imaging (BLI), were injected with OPN intracerebroventricularly while control mice were injected with vehicle buffer. To assess the effects of OPN after ischemia, additional mice were subjected to photothrombosis and injected with either OPN or vehicle.

Results

OPN enhanced the migration of neuroblasts both in the healthy brain and after ischemia, as quantified by BLI in vivo. Moreover, the number of neural progenitors was increased following OPN treatment, with the maximum effect on the second day after OPN injection into the healthy brain, and 14 days after OPN injection following ischemia. After ischemia, OPN quantitatively promoted the endogenous, ischemia-induced neuroblast expansion, and additionally recruited progenitors from the contralateral hemisphere.

Conclusions

Our results strongly suggest that OPN constitutes a promising substance for the targeted activation of neurogenesis in ischemic stroke.

Association of Osteopontin, Neopterin, and Myeloperoxidase With Stroke Risk in Patients With Prior Stroke or Transient Ischemic Attacks: Results of an Analysis of 13 Biomarkers From the Stroke Prevention by Aggressive Reduction in Cholesterol Levels Trial

BACKGROUND AND PURPOSE

Established risk factors do not fully identify patients at risk for recurrent stroke. The SPARCL trial (Stroke Prevention by Aggressive Reduction in Cholesterol Levels) evaluated the effect of atorvastatin on stroke risk in patients with a recent stroke or transient ischemic attack and no known coronary heart disease. This analysis explored the relationships between 13 plasma biomarkers assessed at trial enrollment and the occurrence of outcome strokes.

METHODS

We conducted a case-cohort study of 2176 participants; 562 had outcome strokes and 1614 were selected randomly from those without outcome strokes. Time to stroke was evaluated by Cox proportional hazards models.

RESULTS

There was no association between time to stroke and lipoprotein-associated phospholipase A₂, monocyte chemoattractant protein-1, resistin, matrix metalloproteinase-9, N-terminal fragment of pro-B-type natriuretic peptide, soluble vascular cell adhesion molecule-1, soluble intercellular adhesion molecule-1, or soluble CD40 ligand. In adjusted analyses, osteopontin (hazard ratio per SD change, 1.362; P<0.0001), neopterin (hazard ratio, 1.137; P=0.0107), myeloperoxidase (hazard ratio, 1.177; P=0.0022), and adiponectin (hazard ratio, 1.207; P=0.0013) were independently associated with outcome strokes. After adjustment for the Stroke Prognostic Instrument-II and treatment, osteopontin, neopterin, and myeloperoxidase remained independently associated with outcome strokes. The addition of these 3 biomarkers to Stroke Prognostic Instrument-II increased the area under the receiver operating characteristic curve by 0.023 (P=0.015) and yielded a continuous net reclassification improvement (29.1%; P<0.0001) and an integrated discrimination improvement (42.3%; P<0.0001).

CONCLUSIONS

Osteopontin, neopterin, and myeloperoxidase were independently associated with the risk of recurrent stroke and improved risk classification when added to a clinical risk algorithm.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique Identifier: NCT00147602.

The Effect of Osteopontin on Microglia

Osteopontin (OPN) is a proinflammatory cytokine that can be secreted from many cells, including activated macrophages and T-lymphocytes, and is widely distributed in many tissues and cells. OPN, a key factor in tissue repairing and extracellular matrix remodeling after injury, is a constituent of the extracellular matrix of the central nervous system (CNS). Recently, the role of OPN in neurodegenerative diseases has gradually caused widespread concern. Microglia are resident macrophage-like immune cells in CNS and play a vital role in both physiological and pathological conditions, including restoring the integrity of the CNS and promoting the progression of neurodegenerative disorders. Microglia's major function is to maintain homeostasis and the normal function of the CNS, both during development and in response to CNS injury. Although the functional mechanism of OPN in CNS neurodegenerative diseases has yet to be fully elucidated, most studies suggest that OPN play a role in pathogenesis of neurodegenerative diseases or in neuroprotection by regulating the activation and function of microglia. Here, we summarize the functions of OPN on microglia in response to various stimulations in vitro and in vivo.

Human osteopontin: Potential clinical applications in cancer (Review)

Human osteopontin (OPN) is a glycosylated phosphoprotein which is expressed in a variety of tissues in the body. In recent years, accumulating evidence has indicated that the aberrant expression of OPN is closely associated with tumourigensis, progression and most prominently with metastasis in several tumour types. In this review, we present the current knowledge on the expression profiles of OPN and its main splice variants in human cancers, as well as the potential implications in patient outcome. We also discuss its putative clinical application as a cancer biomarker and as a therapeutic target.

Osteopontin Bridging Innate and Adaptive Immunity in Autoimmune Diseases

Osteopontin (OPN) regulates the immune response at multiple levels. Physiologically, it regulates the host response to infections by driving T helper (Th) polarization and acting on both innate and adaptive immunity; pathologically, it contributes to the development of immune-mediated and inflammatory diseases. In some cases, the mechanisms of these effects have been described, but many aspects of the OPN function remain elusive. This is in part ascribable to the fact that OPN is a complex molecule with several posttranslational modifications and it may act as either an immobilized protein of the extracellular matrix or a soluble cytokine or an intracytoplasmic molecule by binding to a wide variety of molecules including crystals of calcium phosphate, several cell surface receptors, and intracytoplasmic molecules. This review describes the OPN structure, isoforms, and functions and its role in regulating the crosstalk between innate and adaptive immunity in autoimmune diseases.

Plasma Osteopontin Levels and Adverse Cardiovascular Outcomes in the PEACE Trial

Osteopontin (OPN) is a secreted glycophosphoprotein that has a role in inflammation, immune response and calcification. We hypothesized that plasma OPN levels are associated with adverse cardiovascular outcomes in patients with stable coronary artery disease (CAD) and preserved ejection fraction (EF) enrolled in the PEACE trial. We measured plasma OPN levels at baseline in 3567 CAD patients (mean age 64.5 ± 8.1 years, 81% men) by a sandwich chemiluminescent assay (coefficient of variation = 4.1%). OPN levels were natural log (Ln) transformed prior to analyses. We assessed whether Ln OPN levels were associated with the composite primary endpoint of cardiovascular death, non-fatal myocardial infarction and hospitalization for heart failure using multiple event multivariable Cox proportional hazards regression. Adjustment was performed for: (a) age and sex; (b) additional potential confounders; and (c) a parsimonious set of statistically significant 10 variates. During a median follow-up of 4.8 years, 416 adverse cardiovascular outcomes occurred in 366 patients. Ln OPN was significantly associated with the primary endpoint; HR (95% CI) = 1.56 (1.27, 1.92); P <0.001, and remained significant after adjustment for age and sex [1.31 (1.06, 1.61); P = 0.01] and after adjustment for relevant covariates [1.24 (1.01, 1.52); P = 0.04]. In a secondary analysis of the individual event types, Ln OPN was significantly associated with incident hospitalization for heart failure: HR (95% CI) = 2.04 (1.44, 2.89); P <0.001, even after adjustment for age, sex and additional relevant covariates. In conclusion, in patients with stable CAD and preserved EF on optimal medical therapy, plasma OPN levels were independently associated with the composite incident endpoint of adverse cardiovascular outcomes as well as incident hospitalization for heart failure.

Inhibition of Cellular Adhesion by Immunological Targeting of Osteopontin Neoepitopes Generated through Matrix Metalloproteinase and Thrombin Cleavage

Osteopontin (OPN), a secreted protein involved in inflammatory processes and cancer, induces cell adhesion, migration, and activation of inflammatory pathways in various cell types. Cells bind OPN via integrins at a canonical RGD region in the full length form as well as to a contiguous cryptic site that some have shown is unmasked upon thrombin or matrix metalloproteinase cleavage. Thus, the adhesive capacity of osteopontin is enhanced by proteolytic cleavage that may occur in inflammatory conditions such as obesity, atherosclerosis, rheumatoid arthritis, tumor growth and metastasis. Our aim was to inhibit cellular adhesion to recombinant truncated proteins that correspond to the N-terminal cleavage products of thrombin- or matrix metalloproteinase-cleaved OPN in vitro. We specifically targeted the cryptic integrin binding site with monoclonal antibodies and antisera induced by peptide immunization of mice. HEK 293 cells adhered markedly stronger to truncated OPN proteins than to full length OPN. Without affecting cell binding to the full length form, the raised monoclonal antibodies specifically impeded cellular adhesion to the OPN fragments. Moreover, we show that the peptides used for immunization were able to induce antisera, which impeded adhesion either to all OPN forms, including the full-length form, or selectively to the corresponding truncated recombinant proteins. In conclusion, we developed immunological tools to selectively target functional properties of protease-cleaved OPN forms, which could find applications in treatment and prevention of various inflammatory diseases and cancers.

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.

Controlled release of osteopontin and interleukin-10 from modified endovascular coil promote cerebral aneurysm healing

Cerebral aneurysm is a bulging of the artery inside the brain that results from a weakened or thin area of the artery wall. Ruptured cerebral aneurysm could lead to serious brain damage or even death, thus the proper treatment is essential. Compared with the conventional microsurgical clipping approach, the endovascular coiling treatment has many advantages, however, with a major disadvantage of high recurrence rate. One way to lower the recurrence rate, which has been tried since one decade ago, is to modify the coil to be bioactive and releasing biological molecules to stimulate tissue ingrowth and aneurysm healing. We have identified three candidates including osteopontin (OPN), IL-10 and matrix metallopeptidase 9 (MMP-9) from previous studies and generated platinum coils coated with these proteins in the carrier of poly-DL-lactic glycolic acid (PLGA). We were interested to know whether coils coated with OPN, IL-10 and MMP-9 were able to promote aneurysm healing and we have tested it in the rat carotid aneurysm model. We found that OPN and IL-10 coated coils had shown significant improvement in tissue ingrowth while MMP-9 coated coils failed to enhance tissue ingrowth compared with the control group. Our studies suggested the possible application of OPN and IL-10 coated coils in aneurysm treatment to overcome the recurrence.

Osteopontin expression in reactive lesions of gingiva

Reactive proliferations of the gingiva comprise lesions such as pyogenic granuloma (PG), inflammatory fibroepithelial hyperplasia (IFH), peripheral ossifying fibroma (POF), and peripheral giant cell lesion. Osteopontin (OPN) has a dual role, it promotes mineralization when it is bound to solid substrate, and on the other hand, it inhibits mineralization when it is seen in association with solution. Objectives The study aimed to evaluate the expression of osteopontin in normal gingival tissue and different types of focal reactive proliferations of gingival tissue, and its role in the development of calcification within it. Material and Methods The presence and distribution of osteopontin was assessed using immunohistochemistry in five cases of normal gingival tissue and 30 cases of focal reactive proliferations of gingiva. Results There was no expression of osteopontin in normal subjects. Few cases of pyogenic granuloma, inflammatory fibroepithelial hyperplasia, and all the cases of peripheral ossifying fibroma showed positivity for osteopontin in the inflammatory cells, stromal cells, extracellular matrix, and in the calcifications. Conclusion The expression of osteopontin in all the cases of peripheral ossifying fibroma speculates that the majority of the cases of peripheral ossifying fibroma originate from the periodontal ligament cells. The treatment modalities for peripheral ossifying fibroma should differ from other focal reactive proliferations of gingiva.

Macrophage-derived osteopontin induces reactive astrocyte polarization and promotes re-establishment of the blood brain barrier after ischemic stroke

Infarcted regions of the brain after stroke are segregated from the intact brain by scar tissue comprising both fibrous and glial components. The extent and quality of scarring is influenced by inflammation. The matricellular glycoprotein osteopontin (OPN) is strongly induced in myeloid cells after stroke and may contribute to repair of ischemic brain lesions. To elucidate the role of OPN in scar formation, we induced photothrombotic brain infarction, characterized by circumscribed cortical infarctions with a well-defined border zone toward the intact brain parenchyma. The cellular source and functional role of OPN was addressed by studies in OPN null (OPN(-/-) ) mice, wild-type mice depleted of hematogenous monocytes/macrophages by clodronate-filled liposome treatment, and CCR2(-/-) bone marrow chimeric mice characterized by impaired hematogenous macrophage influx into the infarctions. OPN was mainly produced by hematogenous macrophages infiltrating into the inner border zone of the infarcts whereas astrocyte activation occurred in the outer border zone. In OPN(-/-) as well as macrophage-depleted mice, reactive astrocytes failed to properly extend processes from the periphery toward the center of the infarctions. This was associated with incomplete coverage of neovessels by astrocytic endfeet and persistent leakiness of the damaged blood brain barrier. In conclusion, OPN produced by hematogenous macrophages induces astrocyte process extension toward the infarct border zone, which may contribute to repair of the ischemic neurovascular unit.

Mechanisms of Healing in Coiled Intracranial Aneurysms: A Review of the Literature

Recanalization of intracranial aneurysms following endovascular coiling remains a frustratingly common occurrence. An understanding of the molecular and histopathologic mechanisms of aneurysm healing following coil embolization is essential to improving aneurysm occlusion rates. Histopathologic studies in coiled human and experimental aneurysms suggest that during the first month postcoiling, thrombus formation and active inflammation occur within the aneurysm dome. Several months following embolization, the aneurysm is excluded from the parent vessel by formation of a neointimal layer, which is often thin and discontinuous, across the aneurysm neck. Numerous coil modifications and systemic therapies have been tested in animals and humans in an attempt to improve the aneurysm-healing process; these modifications have met with variable levels of success. In this review, we summarize the histopathologic and molecular biology of aneurysm healing and discuss how these findings have been applied in an attempt to improve angiographic outcomes in patients with intracranial aneurysms.

Osteopontin mediates survival, proliferation and migration of neural stem cells through the chemokine receptor CXCR4

Introduction

Osteopontin (OPN) is a phosphoglycoprotein with important roles in tissue homeostasis, wound healing, immune regulation, and stress responses. It is expressed constitutively in the brain and upregulated during neuroinflammatory responses; for example, after focal cerebral ischemia. To date, its effects on neural stem cells (NSC) remain to be elucidated and are, accordingly, the subject of this study.

Method

Primary fetal rat NSC were cultured as homogenous monolayers and treated with different concentrations of OPN. Fundamental properties of NSC were assessed following OPN exposure, including proliferative activity, survival under oxidative stress, migration, and differentiation potential. To elucidate a putative action of OPN via the CXC chemokine receptor type 4 (CXCR4), the latter was blocked with AMD3100. To investigate effects of OPN on endogenous NSC in vivo, recombinant OPN was injected into the brain of healthy adult rats as well as rats subjected to focal cerebral ischemia. Effects of OPN on NSC proliferation and neurogenesis in the subventricular zone were studied immunohistochemically.

Results

OPN dose-dependently increased the number of NSC in vitro. As hypothesized, this effect was mediated through CXCR4. The increase in NSC number was due to both enhanced cell proliferation and increased survival, and was confirmed in vivo. Additionally, OPN dose-dependently stimulated the migration of NSC via CXCR4. Moreover, in the presence of OPN, differentiation of NSC led to a significant increase in neurogenesis both in vitro as well as in vivo after cerebral ischemia.

Conclusion

Data show positive effects of OPN on survival, proliferation, migration, and neuronal differentiation of NSC. At least in part these effects were mediated via CXCR4. Results suggest that OPN is a promising substance for the targeted activation of NSC in future experimental therapies for neurological disorders such as stroke.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0098-x) contains supplementary material, which is available to authorized users.

Assessment of serum levels of osteopontin, selenium and prolactin in patients with psoriasis compared with healthy controls, and their association with psoriasis severity

BACKGROUND

The association between psoriasis and cardiovascular diseases is well documented, but the underlying mechanisms remain unknown. Overexpression of osteopontin (OPN) has been reported in the plasma of patients with psoriasis, with increased cardiovascular risk factors in these patients. Selenium compounds are effective in downregulating OPN expression.

OBJECTIVE

We investigated the levels of OPN, selenium and prolactin (PRL) in psoriasis, and their association with metabolic status in patients to identify a possible link between these markers and observed comorbidities.

METHODS

Plasma samples from 40 patients with psoriasis and 40 age- and sex-matched healthy controls (HCs) were collected for ELISA. The clinical significance of plasma OPN, selenium and PRL levels in patients compared with controls was analysed in relation to metabolic disorders.

RESULTS

There was no significant difference in median serum selenium levels between the two groups. Serum levels of PRL were not significantly different from those of HCs, but levels of OPN were significantly higher in patients with psoriasis than in HCs.

CONCLUSIONS

High plasma OPN is a predictor for occurrence of psoriasis. Our study showed that serum selenium and PRL were not decreased in patients with psoriasis, but there was a negative statistically significant correlation between OPN and selenium in all participants.

Clinical Application of Mesenchymal Stem Cells and Novel Supportive Therapies for Oral Bone Regeneration

Bone regeneration is often needed prior to dental implant treatment due to the lack of adequate quantity and quality of the bone after infectious diseases, trauma, tumor, or congenital conditions. In these situations, cell transplantation technologies may help to overcome the limitations of autografts, xenografts, allografts, and alloplastic materials. A database search was conducted to include human clinical trials (randomized or controlled) and case reports/series describing the clinical use of mesenchymal stem cells (MSCs) in the oral cavity for bone regeneration only specifically excluding periodontal regeneration. Additionally, novel advances in related technologies are also described. 190 records were identified. 51 articles were selected for full-text assessment, and only 28 met the inclusion criteria: 9 case series, 10 case reports, and 9 randomized controlled clinical trials. Collectively, they evaluate the use of MSCs in a total of 290 patients in 342 interventions. The current published literature is very diverse in methodology and measurement of outcomes. Moreover, the clinical significance is limited. Therefore, the use of these techniques should be further studied in more challenging clinical scenarios with well-designed and standardized RCTs, potentially in combination with new scaffolding techniques and bioactive molecules to improve the final outcomes.

Under-expression of α8 integrin aggravates experimental atherosclerosis

Integrins play an important role in vascular biology. The α8 integrin chain attenuates smooth muscle cell migration but its functional role in the development of atherosclerosis is unclear. Therefore, we studied the contribution of α8 integrin to atherosclerosis and vascular remodelling. We hypothesized that α8 integrin expression is reduced in atherosclerotic lesions, and that its under-expression leads to a more severe course of atherosclerosis. α8 Integrin was detected by immunohistochemistry and qPCR and α8 integrin-deficient mice were used to induce two models of atherosclerotic lesions. First, ligation of the carotid artery led to medial thickening and neointima formation, which was quantified in carotid cross-sections. Second, after crossing into ApoE-deficient mice, the formation of advanced vascular lesions with atherosclerotic plaques was quantified in aortic en face preparations stained with Sudan IV. Parameters of renal physiology and histopathology were assessed: α8 integrin was detected in the media of human and murine vascular tissue and was down-regulated in arteries with advanced atherosclerotic lesions. In α8 integrin-deficient mice (α8(-/-) ) as well as α8(+/-) and α8(+/+) littermates, carotid artery ligation increased media:lumen ratios in all genotypes, with higher values in ligated α8(-/-) and α8(+/-) compared to ligated α8(+/+) animals. Carotid artery ligation increased smooth muscle cell number in the media of α8(+/+) mice and, more prominently, of α8(-/-) or α8(+/-) mice. On an ApoE(-/-) background, α8(+/-) and α8(-/-) mice developed more atherosclerotic plaques than α8(+/+) mice. α8 Integrin expression was reduced in α8(+/-) animals. Renal damage with increased serum creatinine and glomerulosclerosis was detected in α8(-/-) mice only. Thus, under-expression of α8 integrin aggravates vascular lesions, while a complete loss of α8 integrin results in reduced renal mass and additional renal disease in the presence of generalized atherosclerosis. Our data support the hypothesis that integrin α8β1 has a protective role in arterial remodelling and atherosclerosis.

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.

A novel cryptic binding motif, LRSKSRSFQVSDEQY, in the C-terminal fragment of MMP-3/7-cleaved osteopontin as a novel ligand for α9β1 integrin is involved in the anti-type II collagen antibody-induced arthritis

Osteopontin (OPN) is a multifunctional protein that has been linked to various intractable inflammatory diseases. One way by which OPN induces inflammation is the production of various functional fragments by enzyme cleavage. It has been well appreciated that OPN is cleaved by thrombin, and/or matrix metalloproteinase-3 and -7 (MMP-3/7). Although the function of thrombin-cleaved OPN is well characterized, little is known about the function of MMP-3/7-cleaved OPN. In this study, we found a novel motif, LRSKSRSFQVSDEQY, in the C-terminal fragment of MMP-3/7-cleaved mouse OPN binds to α9β1 integrin. Importantly, this novel motif is involved in the development of anti-type II collagen antibody-induced arthritis (CAIA). This study provides the first in vitro and in vivo evidence that OPN cleavage by MMP-3/7 is an important regulatory mechanism for CAIA.

Association between the hypomethylation of osteopontin and integrin β3 promoters and vascular smooth muscle cell phenotype switching in great saphenous varicose veins

Lower extremity varicose veins are a common condition in vascular surgery and proliferation of vascular smooth muscle cells (VSMCs) in the intima is a significant pathological feature of varicosity. However, the pathogenesis of varicose veins is not fully understood. Osteopontin (OPN) could promote the migration and adhesion of VSMCs through the cell surface receptor integrin β3 and the cooperation of OPN and integrin β3 is involved in many vascular diseases. However, the role of OPN and integrin β3 in varicosity remains unclear. In the current study, we found that the methylation levels in the promoter regions of OPN and integrin β3 genes in the VSMCs of varicose veins are reduced and the protein expression of OPN and integrin β3 are increased, compared with normal veins. Furthermore, it was observed that VSMCs in the neointima of varicose veins were transformed into the synthetic phenotype. Collectively, hypomethylation of the promoter regions for OPN and integrin β3 genes may increase the expression of these genes in varicosity, which is closely related to VSMC phenotype switching. Hypomethylation of the promoter regions for OPN and integrin β3 genes may be a key factor in the pathogenesis of varicosity.

Atorvastatin inhibits hyperglycemia-induced expression of osteopontin in the diabetic rat kidney via the p38 MAPK pathway

Osteopontin (OPN), a large phosphoglycoprotein adhesion molecule, which is up-regulated in the kidneys of humans and mice with diabetes, has emerged as a potentially key pathophysiological contributor in diabetic nephropathy. Here, we investigated the role of OPN in kidney injury caused by diabetic nephropathy and the effect of atorvastatin on the expression of OPN and on diabetic nephropathy. Diabetes was induced with streptozotocin in rats, and atorvastatin (5 mg/kg) was orally administered once a day for 8 weeks. We analyzed the expression and regulation of OPN in the kidneys of streptozotocin-induced diabetic Sprague-Dawley albino rats by immunohistochemistry and western blot analysis. The expression of OPN was increased in diabetic rat kidney, and atorvastatin inhibited this process. Atorvastatin also decreased the expression and phosphorylation of p38. In vitro, atorvastatin inhibited the high glucose-induced OPN expression in Madin-Darby canine kidney epithelial cells through the p38 MAPK signaling pathway. These results suggested that atorvastatin reduced the expression of OPN through inhibition of the p38 MAPK pathway. The expression of OPN was associated with kidney injury. These molecules may represent therapeutic targets for the prevention of acute kidney injury induced by diabetes.

Vitamin D in endometriosis: a causative or confounding factor?

OBJECTIVE

The aim of this paper is to review the evidence from studies that evaluated the relationship between vitamin D and endometriosis.

DESIGN

Comprehensive review.

MATERIALS AND METHODS

Systematic literature search in Medline for relevant publications from 1946 until June 2013.

RESULTS

Endometriosis risk may be influenced by dietary vitamin D intake and plasma hydroxyvitamin D concentration. Vitamin D receptor and vitamin D metabolizing enzymes, 24-hydroxylase and 1-α hydroxylase, are found in the normal cycling endometrium and also in the eutopic and ectopic endometrium of women with endometriosis. The endometrium is a target of 1, 25 dihydroxyvitamin D actions through regulation of specific genes and via immunomodulation. The endometrium in endometriosis expresses dysregulation of some vitamin D enzymes and receptors. If vitamin D and its metabolites are implicated in endometriosis-associated infertility, it is likely through interference with HOXA10 gene expression. The Gc2 phenotype of vitamin D binding protein is prevalent in women with endometriosis and may be implicated in its pathogenesis. In a mouse model, Elocalcitol, a VDR-agonist was shown to reduce the development of endometriotic lesions and recurrence.

CONCLUSION

A biological plausibility for a role of vitamin D, as an immunomodulator and anti-inflammatory agent, in the pathogenesis and treatment of endometriosis is suggested in this article, but is difficult to illustrate due to sparse evidence from human studies limited primarily to case-control studies. A significant knowledge gap precludes the establishment of a clear cause-effect relationship. The intriguing leads presented herein need to be investigated further with placebo-controlled supplementation trials.

Role of the renin-angiotensin system on abdominal aortic aneurysms

BACKGROUND

Abdominal aortic aneurysm (AAA) is a complex degenerative disease, which leads to morbidity and mortality in a large portion of the elderly population. Current treatment options for AAA are quite limited as there is no proven indication for pharmacological therapy and surgery is recommended for AAA larger than 5·5 cm in luminal diameter. Thus, there is a great need to elucidate the underlying pathophysiological cellular and molecular mechanisms to develop effective therapies. In this narrative review, we will discuss recent findings concerning some potential molecular and clinical aspects of the renin-angiotensin system (RAS) in AAA pathophysiology.

MATERIALS AND METHODS

This narrative review is based on the material found on MEDLINE and PubMed up to April 2013. We looked for the terms 'angiotensin, AT1 receptor, ACE inhibitors' in combination with 'abdominal aortic aneurysm, pathophysiology, pathways'.

RESULTS

Several basic research and clinical studies have recently investigated the role of the RAS in AAA. In particular, the subcutaneous infusion of Angiotensin II has been shown to induce AAA in Apo56 knockout mice. On the other hand, the pharmacological treatments targeting this system have been shown as beneficial in AAA patients.

CONCLUSIONS

Emerging evidence suggests that RAS may act as a molecular and therapeutic target for treating AAA. However, several issues on the role of RAS and the protective activities of angiotensin-converting enzyme (ACE) inhibitors and Angiotensin 1 receptors blockers against AAA require further clarifications.

Morphological evidences of Bio-Oss® colonization by CD44-positive cells

OBJECTIVES

Our objectives were to examine vascular and cellular colonization in anorganic bovine bone (ABB) after 6 months of healing in human maxillary sinus augmentation grafts.

MATERIAL AND METHODS

Fifty unilateral maxillary sinus augmentation procedures were performed on 50 consecutive patients. Bone cores were obtained through the implant receptor sites 6 months later and evaluated with morphological image analysis and immunohistochemical techniques.

RESULTS

Image analysis revealed a mean of 35.44 ± 16% vital bone, 31.66 ± 15% non-mineralized tissue, and 32.72 ± 25% remnant ABB particles. In our patients, neovascularization in 46.3% of cases was demonstrated within ABB particles 6 months after sinus floor augmentation surgery. Neovascularization of ABB particles was inversely related to age, directly to osteoclast number per mm², and not influenced by habits or disease. CD44-positive cells colonization was found in 74% of cases. An important correlation was found regarding CD44 expression and number of vessel in ABB particles (r = 0.624 P < 0.001, Pearson). Osteopontin expression was detected on the interstitial boundary of bone with ABB particles and within the osteocyte lacunae and bone canaliculi and was relationship with presence of CD44-positive cells inside ABB particles (r = 0.388, P = 0.046, Pearson).

CONCLUSION

In conclusion, images compatible with osteone colonized by osteocytes CD44 positive and neovascularization in ABB particles were observed after 6 months of graft maturation. These biologic events have not previously been morphologically and immunohistochemically documented.

Osteopontin is an endogenous modulator of the constitutively activated phenotype of pulmonary adventitial fibroblasts in hypoxic pulmonary hypertension

Increased cell proliferation and migration, of several cell types are key components of vascular remodeling observed in pulmonary hypertension (PH). Our previous data demonstrate that adventitial fibroblasts isolated from pulmonary arteries of chronically hypoxic hypertensive calves (termed PH-Fibs) exhibit a "constitutively activated" phenotype characterized by high proliferative and migratory potential. Osteopontin (OPN) has been shown to promote several cellular activities including growth and migration in cancer cells. We thus tested the hypothesis that elevated OPN expression confers the "activated" highly proproliferative and promigratory/invasive phenotype of PH-Fibs. Our results demonstrate that, both in vivo and ex vivo, PH-Fibs exhibited increased expression of OPN, as well as its cognate receptors, α(V)β(3) and CD44, compared with control fibroblasts (CO-Fibs). Augmented OPN expression in PH-Fibs corresponded to their high proliferative, migratory, and invasive properties and constitutive activation of ERK1/2 and AKT signaling. OPN silencing via small interfering RNA or sequestering OPN production by specific antibodies led to decreased proliferation, migration, invasion, and attenuated ERK1/2, AKT phosphorylation in PH-Fibs. Furthermore, increasing OPN levels in CO-Fibs via recombinant OPN resulted in significant increases in their proliferative, migratory, and invasive capabilities to the levels resembling those of PH-Fibs. Thus our data suggest OPN as an essential contributor to the activated (highly proliferative, migratory, and proinvasive) phenotype of pulmonary adventitial fibroblasts in hypoxic PH.

Osteopontin increases the proliferation of neural progenitor cells

We examined the role of osteopontin in the proliferation of neural progenitor cells in vitro. Osteopontin increased the proliferation of neural progenitor cells in the presence of FGF2 as measured by cell proliferation assay and bromodeoxy uridine incorporation studies. In addition, immunoblot analysis demonstrated an increase in the phosphorylation of retinoblastoma protein with a concurrent increase in the content of phospho-Akt and cyclin D1. These results indicate that osteopontin can upregulate the content of phospho-Akt, cyclin D1 and phospho-Rb to subsequently enhance the proliferation of neural progenitor cells in the presence of FGF2.

Arteriolar vascular smooth muscle cell differentiation in benign nephrosclerosis

BACKGROUND

Benign nephrosclerosis (bN) is the most prevalent form of hypertensive damage in kidney biopsies. It is defined by early hyalinosis and later fibrosis of renal arterioles. Despite its high prevalence, very little is known about the contribution of arteriolar vascular smooth muscle cells (VSMCs) to bN. We examined classical and novel candidate markers of the normal contractile and the pro-fibrotic secretory phenotype of VSMCs in arterioles in bN.

METHODS

Sixty-three renal tissue specimens with bN and eight control specimens were examined by immunohistochemistry for the contractile markers caldesmon, alpha-smooth muscle actin (alpha-SMA), JunB, smoothelin and the secretory marker S100A4 and by double stains for caldesmon or smoothelin with S100A4.

RESULTS

Smoothelin immunostaining showed an inverse correlation with hyalinosis and fibrosis scores, while S100A4 correlated with fibrosis scores only. Neither caldesmon, alpha-SMA nor JunB correlated with hyalinosis or fibrosis scores. Cells in the arteriolar wall were exclusively positive either for caldesmon/smoothelin or S100A4.

CONCLUSIONS

This is the first systematic analysis of VSMC differentiation in bN. The results suggest that smoothelin is the most sensitive marker for the contractile phenotype and that S100A4 could be a novel marker for the secretory phenotype in vivo. The other markers did not seem to differentiate these phenotypes in bN. Thus, VSMC phenotype markers should be defined in the context of the vessel segment and disease under examination. S100A4 could not only be a marker of pro-fibrotic secretory VSMCs in bN but also an important mediator of arteriolar fibrosis.

Osteopontin and endostatin concentrations in peripheral blood of patients with adrenal tumors undergoing unilateral adrenalectomy

Peripheral blood osteopontin (OPN) and endostatin (END) levels were studied in 35 patients with adrenal cortex tumors and 10 patients with pheochromocytoma before unilateral adrenalectomy, as well as in 10 healthy subjects (controls). Thirty days after surgery, OPN and END were evaluated again in 16 patients with adrenal cortex tumors and 4 female patients with pheochromocytoma. Before surgery, OPN blood concentrations increased in the group of patients with adrenal cortex carcinomas as compared to controls (p < 0.001) and the group with Conn syndrome (p < 0.05); they did not change after surgery. Before adrenalectomy, OPN blood levels in pheochromocytoma patients were also lower than in Conn syndrome subjects (p < 0.05). After adrenalectomy, the normal concentrations of END decreased only in the group of patients with hormonally inactive cortical adenomas (p < 0.05). We were unable to demonstrate any relationships between removed tumor volumes and OPN or END blood levels.

Aldosterone-induced osteopontin gene transcription in vascular smooth muscle cells involves glucocorticoid response element

Osteopontin (OPN) is known to be one of the cytokines that is involved in the vascular inflammation caused by aldosterone (Aldo). Previous reports have shown that Aldo increases OPN transcripts, and the mechanisms for this remain to be clarified. In this study, we investigated how Aldo increases OPN transcripts in the vascular smooth muscle cells of rats. Aldosterone increased OPN transcripts time-dependently as well as dose-dependently. This increase was diminished by eplerenone, a mineralocorticoid receptor (MR) antagonist. Luciferase promoter assays showed that the OPN promoter deleted to the -1599 site retained the same promoting ability as the full-length OPN promoter when stimulated by 10(-7) M Aldo, but the promoter deleted to the -1300 site lost the promoting ability. A glucocorticoid response element (GRE) is located in that deleted region. Luciferase assays of a mutated promoter without the GRE lost the luciferase upregulation, although mutated promoters with the deletion of other consensus sites maintained the promoter activity. The binding of the Aldo-MR complex to the GRE fragment was confirmed by an electrophoretic-mobility shift assay. This is the first report showing that Aldo regulates the transcriptional levels of OPN and inflammatory responses in the vasculature through a specific GRE site in the OPN promoter region.

Systemic blood osteopontin, endostatin, and E-selectin concentrations after vertical banding surgery in severely obese adults

BACKGROUND

Obesity is associated with endothelial dysfunction and increased inflammation as well as with expansion of the capillary bed in regional adipose deposits, and a balance between these factors is involved in angiogenesis. Osteopontin (OPN) is a proinflammatory cytokine involved in regulating immune processes and mediating chronic inflammation. Its level is usually elevated in the plasma and adipose tissue of obese subjects. E-selectin, an adhesion molecule which is released by dysfunctional endothelial cells, is believed to be a marker of an early atherosclerotic process. Endostatin (END), an angiogenesis inhibitor, is present in the blood of obese subjects. The most effective treatment to achieve weight loss in morbidly obese subjects is bariatric surgery. The aim of the study was to evaluate and compare the circulating concentrations of OPN, E-selectin and END as well as the insulin resistance (HOMA-IR) of severely obese patients with metabolic syndrome before and after vertical banded gastroplasty (VBG).

MATERIAL AND METHODS

The test cohorts comprised eight males and 20 females (total 28 patients) aged from 20 to 59 years with simple obesity and the presence of metabolic syndrome, both before and 3, 6, 12, 24 months after bariatric surgery (six patients were also checked after 36 and four after 48 months).

RESULTS

Bariatric surgery significantly reduced (over 24 months) body weight, BMI, waist circumference, HOMA-IR and blood concentrations of CRP. Plasma OPN gradually increased after VBG and E-selectin in systemic blood decreased. We did not observe any differences in END concentrations from 12 to 48 months after surgery.

CONCLUSION

VBG improves metabolic syndrome parameters, decreases E-selectin and gradually increases OST blood concentrations but it does not have any significant influence on END levels.