Role of osteopontin in rheumatoid arthritis

Clinical significance of microRNA-328-3p and bone metabolism biomarkers in gout patients with different musculoskeletal ultrasonography imaging

AIMS

MicroRNA (miRNA) participates in the pathophysiological processes of multiple metabolic diseases, including gout. In gout patients, there is concomitant derangement of bone metabolism. The study aimed to explore the correlation of different ultrasonic manifestations and miR-328-3p levels with bone metabolic markers in gout patients.

METHODS

A total of 320 gout patients were grouped according to musculoskeletal ultrasound (MSUS) imaging. Serum osteocalcin (BGP), C-terminal telopeptide of type I collagen (CTX-I) and osteopotin (OPN) levels were detected to evaluate bone metabolism. Serum miR-328-3p levels were detected via qRT-PCR. Pearson's correlation analysis was performed to explore the relationships between the variables.

RESULTS

Patients with tophi accompanied by bone erosion demonstrated significantly elevated levels of BGP and OPN compared to those with tophi or aggregate of MSU crystals in the absence of bone erosions. Cases with long course of disease exhibited more severe bone destruction. Cases without specific clinical manifestations presented the highest levels of serum miR-328-3p, whereas those with bone erosions demonstrated the lowest values. Significantly negative correlations were also detected for serum miR-328-3p levels with BGP and OPN values in all gout patients.

CONCLUSION

Serum miR-328-3p levels were associated with diverse MSUS manifestations in gout patients. MSUS imaging and miR-328-3p levels are capable of reflecting the joint impairment in gout patients.

Osteopontin inhibits autophagy via CD44 and avβ3 integrin and promotes cell proliferation in osteoarthritic fibroblast-like synoviocytes

OBJECTIVE

Osteoarthritis (OA) is closely related to aging, and autophagy is implicated in the retardation of aging. Activated synoviocytes play important roles in OA; the synoviocytes could produce osteopontin (OPN) and its main receptors CD44 and integrin, which are all involved in OA. The purpose of this study is to investigate whether OPN has an effect on autophagy in osteoarthritic synoviocytes.

METHODS

We cultured human OA fibroblast-like synoviocytes (FLS) and treated them with rhOPN and antibodies against CD44 and CD51/61 (αvβ3 integrin) or isotype IgG to block the interaction between receptors and ligands. Infection with lentivirus mRFP-GFP-LC3, laser confocal imaging and Western blotting were used to determine changes in the expression of autophagy markers, and cell proliferation of FLS was assessed with a CCK-8 assay.

RESULTS

Our results showed the expression level of autophagy marker protein LC3 II and the mRFP-GFP-LC3 puncta were significantly decreased after treatment with rhOPN when compared with the control group, when the FLS were incubated with antibodies against CD44 or CD51/61 (αvβ3 integrin) or with control isotype IgG for 1 h, followed by rhOPN treatment for 48 h, rhOPN could suppress the relative expression of LC3 II and Beclin1 via integrin and CD44 in the FLS, CCK-8 assay also showed that rhOPN significantly increased the cell proliferation and viability of FLS.

CONCLUSIONS

OPN could inhibit autophagy via CD44 and αvβ3 integrin and promote the proliferation of FLS, playing an important role in OA synovitis.

Osteopontin in rheumatic diseases: A systematic review and meta-analysis

Osteopontin (OPN), a glycoprotein involved in immune regulation and inflammation, is a potential candidate biomarker for rheumatic diseases (RDs). However, variability across studies limits its clinical utility. This meta-analysis evaluated OPN concentrations in RD patients compared to healthy controls and explored sources of heterogeneity. A systematic search identified 37 studies (43 comparator groups) including 3,201 RD patients and 2,543 controls. Standardized mean differences (SMDs) were calculated, and subgroup and meta-regression analyses examined the modulating role of demographic and clinical variables. Publication bias was assessed using Begg's and Egger's tests. OPN concentrations were significantly higher in RD patients than controls (SMD = 1.54, 95 % CI: 1.17-1.90, p < 0.001). Subgroup analysis revealed consistent elevations in systemic lupus erythematosus (SLE, SMD = 0.97, I2 = 0 %) and rheumatoid arthritis (RA, SMD = 0.70, I2 = 92.5 %), with osteoarthritis showing the largest effect size (SMD = 4.02). Age significantly moderated OPN concentrations (p = 0.030). Although publication bias was detected (p < 0.05), removing seven studies eliminated bias and maintained significant between-group differences (SMD = 0.78, 95 % CI: 0.62-0.93; p < 0.001). The high concentrations of OPN support its possible use as a candidate biomarker for RDs, particularly in SLE and RA. Resolution of heterogeneity and standardization may improve its clinical utility.

A druggable targets discovery strategy for diseases (DTDS): Taking Rheumatoid arthritis as a case

Identifying effective druggable targets with disease-specific for diseases is a tremendous challenge in new drug development. However, current studies of druggable targets identification are most based on either druggability or disease-specific, lacking a combination of two factors. To further improve the accuracy of druggable targets discovery, a druggable target discovery strategy for diseases (DTDS) was proposed, which combined druggable targets prediction by machine learning and key targets identification by tissue-level and cellular-level transcriptomics analysis. Rheumatoid arthritis (RA), an autoimmune disease that cannot be treated entirely, was taken as a case. First, the protein-protein interaction network was constructed as the disease background network, and the classification models were established based on the topological parameters of known RA-druggable targets with druggability and non-RA targets without therapeutic effects on RA. 168 potential druggable targets were predicted by the classification models from 264 RA-related targets. Subsequently, 40 RA-specific targets were identified by tissue-level and cellular-level transcriptomics analysis from 168 potential druggable targets. Most of them were RA-druggable targets except PSMB9 and PTPRC. Finally, PSMB9 and PTPRC were further verified by in vitro experiments. The results showed that the inhibitor of PSMB9 or PTPRC could effectively inhibit inflammation and abnormal proliferation of synovial cells, proving that PSMB9 and PTPRC were potential RA-druggable targets, and further indicating that DTDS had high accuracy. In conclusion, the DTDS strategy established in this study is reliable and has been proven in identification of potential RA-druggable targets, which is expected to provide ideas and methods for systematic discovery of potential druggable targets for diseases.

The chromatin landscape of pathogenic transcriptional cell states in rheumatoid arthritis

Synovial tissue inflammation is a hallmark of rheumatoid arthritis (RA). Recent work has identified prominent pathogenic cell states in inflamed RA synovial tissue, such as T peripheral helper cells; however, the epigenetic regulation of these states has yet to be defined. Here, we examine genome-wide open chromatin at single-cell resolution in 30 synovial tissue samples, including 12 samples with transcriptional data in multimodal experiments. We identify 24 chromatin classes and predict their associated transcription factors, including a CD8 + GZMK+ class associated with EOMES and a lining fibroblast class associated with AP-1. By integrating with an RA tissue transcriptional atlas, we propose that these chromatin classes represent 'superstates' corresponding to multiple transcriptional cell states. Finally, we demonstrate the utility of this RA tissue chromatin atlas through the associations between disease phenotypes and chromatin class abundance, as well as the nomination of classes mediating the effects of putatively causal RA genetic variants.

Immunoregulatory Roles of Osteopontin in Diseases

Osteopontin (OPN) is a multifunctional protein that plays a pivotal role in the immune system. It is involved in various biological processes, including cell adhesion, migration and survival. The study of the immunomodulatory effects of OPN is of paramount importance due to its potential therapeutic applications. A comprehensive understanding of how OPN regulates the immune response could pave the way for the development of novel treatments for a multitude of diseases, including autoimmune disorders, infectious diseases and cancer. Therefore, in the following paper, we provide a systematic overview of OPN and its immunoregulatory roles in various diseases, laying the foundation for the development of OPN-based therapies in the future.

The Chromatin Landscape of Pathogenic Transcriptional Cell States in Rheumatoid Arthritis

Synovial tissue inflammation is the hallmark of rheumatoid arthritis (RA). Recent work has identified prominent pathogenic cell states in inflamed RA synovial tissue, such as T peripheral helper cells; however, the epigenetic regulation of these states has yet to be defined. We measured genome-wide open chromatin at single cell resolution from 30 synovial tissue samples, including 12 samples with transcriptional data in multimodal experiments. We identified 24 chromatin classes and predicted their associated transcription factors, including a CD8+ GZMK+ class associated with EOMES and a lining fibroblast class associated with AP-1. By integrating an RA tissue transcriptional atlas, we found that the chromatin classes represented 'superstates' corresponding to multiple transcriptional cell states. Finally, we demonstrated the utility of this RA tissue chromatin atlas through the associations between disease phenotypes and chromatin class abundance as well as the nomination of classes mediating the effects of putatively causal RA genetic variants.

The Role and Clinical Relevance of Osteopontin in Allergic Airway Diseases

The airway epithelium is exposed to numerous external irritants including infectious agents, environmental allergens, and atmospheric pollutants, releasing epithelial cytokines including thymic stromal lymphopoietin (TSLP), IL-33, and IL-25 and initiating downstream type 2 (IL-4, IL-13, and IL-5) and IgE-driven pathways. These pathways trigger the initiation and progression of allergic airway diseases, including chronic rhinosinusitis with nasal polyps (CRSwNP), allergic rhinitis (AR), and allergic asthma. However, the use of biological agents that target downstream cytokines, such as IL-5, IL-4, and IL-13 receptors and IgE, might not be sufficient to manage some patients successfully. Instead of blocking downstream cytokines, targeting upstream epithelial cytokines has been proposed to address the complex immunologic networks associated with allergic airway diseases. Osteopontin (OPN), an extracellular matrix glyco-phosphoprotein, is a key mediator involved in Th1-related diseases, including systemic lupus erythematosus, multiple sclerosis, inflammatory bowel disease, and rheumatoid arthritis. Emerging evidence, including ours, indicates that epithelial-cell-derived OPN also plays an essential role in Th2-skewed airway diseases, including CRSwNP, AR, and allergic asthma involving the Th17 response. Therefore, we reviewed the current knowledge of epithelial-cell-derived OPN in the pathogenesis of three type-2-biased airway diseases and provided a direction for its future investigation and clinical relevance.

Baseline Plasma Osteopontin Protein Elevation Predicts Adverse Outcomes in Hospitalized COVID-19 Patients

More than three years have passed since the first case, and COVID-19 is still a health concern, with several open issues such as the lack of reliable predictors of a patient’s outcome. Osteopontin (OPN) is involved in inflammatory response to infection and in thrombosis driven by chronic inflammation, thus being a potential biomarker for COVID-19. The aim of the study was to evaluate OPN for predicting negative (death or need of ICU admission) or positive (discharge and/or clinical resolution within the first 14 days of hospitalization) outcome. We enrolled 133 hospitalized, moderate-to-severe COVID-19 patients in a prospective observational study between January and May 2021. Circulating OPN levels were measured by ELISA at admission and at day 7. The results showed a significant correlation between higher plasma concentrations of OPN at hospital admission and a worsening clinical condition. At multivariate analysis, after correction for demographic (age and gender) and variables of disease severity (NEWS2 and PiO2/FiO2), OPN measured at baseline predicted an adverse prognosis with an odds ratio of 1.01 (C.I. 1.0–1.01). At ROC curve analysis, baseline OPN levels higher than 437 ng/mL predicted a severe disease evolution with 53% sensitivity and 83% specificity (area under the curve 0.649, p = 0.011, likelihood ratio of 1.76, (95% confidence interval (CI): 1.35–2.28)). Our data show that OPN levels determined at the admission to hospital wards might represent a promising biomarker for early stratification of patients’ COVID-19 severity. Taken together, these results highlight the involvement of OPN in COVID-19 evolution, especially in dysregulated immune response conditions, and the possible use of OPN measurements as a prognostic tool in COVID-19.

Identification of anti-citrullinated osteopontin antibodies and increased inflammatory response by enhancement of osteopontin binding to fibroblast-like synoviocytes in rheumatoid arthritis

BACKGROUND

Anti-citrullinated protein/peptide antibodies (ACPAs) are present in patients at onset and have important pathogenic roles during the course of rheumatoid arthritis (RA). The characteristics of several molecules recognized by ACPA have been studied in RA, but the positivity rate of autoantibodies against each antigen is not high, and the pathogenic mechanism of each antibody is not fully understood. We investigated the role of anti-citrullinated osteopontin (anti-cit-OPN) antibodies in RA pathogenesis.

METHODS

Enzyme-linked immunosorbent assays on RA patients' sera were used to detect autoantibodies against OPN. Fibroblast-like synoviocytes (FLS) isolated from RA patients were used to test the binding activity and inflammatory response of OPN mediated by anti-cit-OPN antibodies, and their effect was tested using an inflammatory arthritis mouse model immunized with cit-OPN. Anti-cit-OPN antibody positivity and clinical characteristics were investigated in the patients as well.

RESULTS

Using sera from 224 RA patients, anti-cit-OPN antibodies were positive in approximately 44% of RA patients, while approximately 78% of patients were positive for the cyclic citrullinated peptide (CCP2) assay. IgG from patients with anti-cit-OPN antibody increased the binding activity of OPN to FLSs, which further increased matrix metalloproteinase and interleukin-6 production in TNF-stimulated FLSs. Mice immunized with cit-OPN antibodies experienced severe arthritis. Anti-cit-OPN antibodies in RA patients decreased the drug survival rate of tumor necrosis factor (TNF) inhibitors, while it did not decrease that of CTLA4-Ig.

CONCLUSIONS

Anti-cit-OPN antibodies were detected in patients with RA. IgG from patients with anti-cit-OPN antibodies aggravated RA, and anti-cit-OPN antibody was a marker of reduced the survival rate of TNF inhibitors in RA patients.

Use of some bone-related cytokines as predictors for rheumatoid arthritis severity by neural network analysis

Background. Rheumatoid arthritis (RA) is characterized by synovial membrane inflammation that results in joint damage. Many earlier studies have measured cytokines for a better diagnosis of RA. In the present study, three bone biomarkers (osteopontin, Stromelysin-1 (MMP3), and vascular endothelial growth factor-A (VEGF)) are examined for their ability to estimate the severity of disease by using artificial neural network (NN) analysis and regression analysis. Methods: The study enrolled 87 RA patients and 44 healthy control subjects. The biomarkers were measured by the enzyme-linked immunosorbent assay (ELISA) technique. Disease Activity Score (28 joints) and C-reactive protein (CRP) (DAS28-CRP) was calculated by using (DAS28-CRP) calculator. The patients with DAS28-CRP5.1 are considered as having high disease activity (HDA). While patients group with DAS28-CRP5.1 are considered as moderate disease activity (MDA). The neural network (NN) analysis was used for the differentiation between groups. Results. Results showed that the most sensitive predictor for high disease activity (HDA) of RA is MMP3, followed by osteopontin and VEGF. These three biomarkers can differentiate significantly between HDA and moderate disease activity (MDA) with a relatively high size effect (Partial 2=0.323, p0.001). HDA group has a significantly higher MMP3, CRP, RF, and anti-citrullinated protein antibodies (ACPA) than the MDA group. Conclusions. The use of the NN analysis indicated that the measured biomarkers help predict the HDA state in RA patients. MMP3 and osteopontin are diagnostic biomarkers for the severity of RA disease and related to many disease-related characteristics with a sensitivity of 88.9% and specificity of 68.4%.

Organokines in Rheumatoid Arthritis: A Critical Review

Rheumatoid arthritis (RA) is a systemic autoimmune disease that primarily affects the joints. Organokines can produce beneficial or harmful effects in this condition. Among RA patients, organokines have been associated with increased inflammation and cartilage degradation due to augmented cytokines and metalloproteinases production, respectively. This study aimed to perform a review to investigate the role of adipokines, osteokines, myokines, and hepatokines on RA progression. PubMed, Embase, Google Scholar, and Cochrane were searched, and 18 studies were selected, comprising more than 17,000 RA patients. Changes in the pattern of organokines secretion were identified, and these could directly or indirectly contribute to aggravating RA, promoting articular alterations, and predicting the disease activity. In addition, organokines have been implicated in higher radiographic damage, immune dysregulation, and angiogenesis. These can also act as RA potent regulators of cells proliferation, differentiation, and apoptosis, controlling osteoclasts, chondrocytes, and fibroblasts as well as immune cells chemotaxis to RA sites. Although much is already known, much more is still unknown, principally about the roles of organokines in the occurrence of RA extra-articular manifestations.

Osteopontin in autoimmune disorders: current knowledge and future perspective

Osteopontin (OPN) is a multifunctional cytokine and adhesion molecule, as well as an unusual regulator for both innate and adaptive immune responses. Several immune cells can produce OPN, including dendritic cells (DCs), macrophages, and T lymphocytes. OPN expression is reported to be increased in a wide range of disorders, including autoimmunity, cancer, and allergy. The overexpression of OPN in several autoimmune disorders, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), multiple sclerosis (MS), Type 1 diabetes (T1D), inflammatory bowel disease (IBD), Sjögren's, and myasthenia gravis, have been shown to be correlated with disease severity. Regarding the important regulatory roles of OPN in the immune system, this study aimed to review the role of this molecule in autoimmune disorders and to provide a complete view of the current knowledge in this field.

Umbilical Cord Mesenchymal Stromal Cells for Cartilage Regeneration Applications

Chondropathies are increasing worldwide, but effective treatments are currently lacking. Mesenchymal stromal cell (MSCs) transplantation represents a promising approach to counteract the degenerative and inflammatory environment characterizing those pathologies, such as osteoarthritis (OA) and rheumatoid arthritis (RA). Umbilical cord- (UC-) MSCs gained increasing interest due to their multilineage differentiation potential, immunomodulatory, and anti-inflammatory properties as well as higher proliferation rates, abundant supply along with no risks for the donor compared to adult MSCs. In addition, UC-MSCs are physiologically adapted to survive in an ischemic and nutrient-poor environment as well as to produce an extracellular matrix (ECM) similar to that of the cartilage. All these characteristics make UC-MSCs a pivotal source for a stem cell-based treatment of chondropathies. In this review, the regenerative potential of UC-MSCs for the treatment of cartilage diseases will be discussed focusing on in vitro, in vivo, and clinical studies.

Osteopontin and Transplantation: Where Are We Now?

Organ transplantation represents the optimal therapeutic tool for patients with end-stage organ failure. Hematopoietic stem cell transplantation (HSCT) is likewise an effective therapy for a wide range of malignant and non-malignant diseases. Better understanding of transplantation immunology and the use of multi-modal immunosuppression protocols, can decrease the risk of graft failure and graft-versus-host disease (GVHD) after HSCT. Nevertheless, a major challenge of modern transplantology still seems to be finding non-invasive biomarkers for recipients selection, monitoring of allograft function, and diagnosis of rejection. Since proinflammatory cytokine osteopontin (OPN) is closely involved in regulating both adaptive and innate immune responses, as well as the pathogenesis of inflammatory and autoimmune diseases, it is likely to play an important role in organ and HSC transplantation. This review is to summarize recent advances in our knowledge about OPN function in the kidney, heart, liver, lung, and HSC transplantation. Most studies found that elevated OPN is associated with poorer graft function in kidney, heart, liver and lung recipients. Moreover, some reports suggested that this protein can play role in GVHD pathogenesis. However, due to relatively small number of similar studies, as well as some inconclusive results, future investigation in this field is needed to verify if OPN can serve as a biomarker of organ and HSC transplantation. The knowledge about such markers will promote our understanding of the mechanisms underlying graft dysfunction and posttransplant mortality. In addition, such knowledge may be helpful in the development of new treatment strategies and identification of recipients with increased risk of allograft failure.

The elevated level of osteopontin in patients with pemphigus vulgaris: A cytokine-like protein with a therapeutic potential

BACKGROUND

Pemphigus vulgaris (PV) is a life-threatening autoimmune disease with no certain treatment. Anticytokine therapy is being increasingly discussed in multiple autoimmune diseases. Osteopontin (OPN) is a glycoprotein produced by a variety of immune cells. Increased OPN serum levels have been reported in several autoimmune diseases, with targeting OPN considered as a promising therapy in these diseases. However, the role of OPN in PV has not been well studied so far.

OBJECTIVE

To investigate whether OPN level is elevated in PV patients in the active stage of the disease and to examine its possible relationship with disease severity and anti-desmoglein (anti-Dsg) antibodies levels.

MATERIALS AND METHODS

This study included 53 consecutive subjects affected by PV and 38 age- and sex-matched healthy controls. Clinical characteristics and Autoimmune Bullous Skin Disorder Intensity Score (ABSIS) were assessed. Serum OPN levels (pg/mL) and anti-Dsg antibodies were also measured.

RESULTS

The serum OPN level of the patient group proved to be statistically higher than that of the control group (11.08 ± 5.24 vs 8.47 ± 5.68; p = .02). No significant relationship were detected between the serum OPN level and anti-Dsg1 or anti-Dsg3 antibodies (r = 0.1, p = .2 and r = 0.1, p = .4), respectively. In addition, no correlation was found between serum OPN levels and severity of PV as measured by ABSIS (r = 0.08 and p = .5).

CONCLUSION

The growth observed in OPN levels in pemphigus patients suggests the role of OPN in pemphigus pathogenesis, but there is a need for more extensive studies to show how OPN can be associated with the PV pathogenesis and whether OPN could be used as an important therapeutic target in pemphigus disease.

THE EFFECT OF ANTITHYROID DRUGS ON OSTEOPONTIN AND OXIDATIVE STRESS IN GRAVES' DISEASE

OBJECTIVE

The aim of the present study is to evaluate the effects of methimazole (MTZ) and propylthiouracil (PTU) treatments on osteopontin (OPN) and oxidative stress in Graves' disease (GD).

MATERIAL AND METHODS

The study included 60 cases with GD in hyperthyroid state and taking no antithyroid treatment, and 30 healthy volunteers. GD patients were randomly separated into two groups; 30 of them took PTU, and the other 30 took MTZ treatments. Blood samples were taken from the patients with GD before the treatment, and three months after the treatment was begun, when they were in the euthyroid state; blood samples of the healthy control subjects were also taken at these times.

RESULTS

TAS and OSI levels before treatment were significantly higher in the GD group, when compared to the control group (p<0.001, for each). GD subjects taking PTU treatment had significantly higher TAS levels (p=0.001), and significantly lower TOS and OSI levels (p=0.008 and p=0.001, respectively). TAS levels significantly decreased in the patients taking MTZ treatment (p=0.029), but TOS and OSI levels did not change significantly (p>0.05). Pretreatment OPN levels were significantly higher in GD patients, when compared to the control group (p=0.014). OPN level significantly decreased in the GD group taking PTU treatment; however OPN levels in the group taking MTZ treatment did not change significantly when compared to the pretreatment value.

CONCLUSION

PTU treatment is more effective in decreasing OPN and oxidative stress in GD patients, when compared to the MTZ treatment.

Circulating Levels of Osteoprotegerin, Osteocalcin and Osteopontin in Patients with Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

OBJECTIVE

Currently published data regarding the potential role of osteoprotegerin (OPG), osteocalcin (OCN) and osteopontin (OPN) for the discrimination between rheumatoid arthritis (RA) and osteoarthritis (OA) are contradictory. To derive a more precise evaluation, a meta-analysis was performed.

METHODS

Published literatures comparing plasma/serum OPG, OCN and OPN levels between RA group and OA controls were searched in PubMed, Embase and the Cochrane Library. The Newcastle-Ottawa Scale was used to assess the study quality. Pooled standard mean difference (SMD) with 95% confidence interval (CI) was calculated by random-effect model analysis. Heterogeneity test was performed by the Q statistic and quantified using I².

RESULTS

Nine studies including 438 RA patients and 255 OA patients were finally incorporated in the meta-analysis after examining title, type, abstracts and full text. The results showed that RA patients had higher plasma/serum OPN (pooled SMD = -2.57, 95% CI = -4.72 to -0.41) levels when compared to OA patients. No significant difference in plasma/serum OPG (pooled SMD = -0.29, 95% CI = -1.07‒0.49) and OCN (pooled SMD = -0.09, 95% CI = -0.48‒0.31) levels were found between RA patients and OA patients. Subgroup analysis indicated that plasma/serum OPG levels had no significant differences between RA patients and OA patients in Europe and Asian.

CONCLUSIONS

Overall, there is no significant difference in circulating OPG and OCN levels between RA patients and OA patients. However, plasma/serum OPN level is significantly higher in RA patients compared with OA patients.

Assessing the Feasibility of Neutralizing Osteopontin with Various Therapeutic Antibody Modalities

Osteopontin is a secreted glycophosphoprotein that is highly implicated in many physiological and pathological processes such as biomineralization, cell-mediated immunity, inflammation, fibrosis, cell survival, tumorigenesis and metastasis. Antibodies against osteopontin have been actively pursued as potential therapeutics for various diseases by pharmaceutical companies and academic laboratories. Many studies have demonstrated the efficacy of osteopontin inhibition in a variety of preclinical models of diseases such as rheumatoid arthritis, cancer, nonalcoholic steatohepatitis, but clinical utility has not yet been demonstrated. To evaluate the feasibility of osteopontin neutralization with antibodies in a clinical setting, we measured its physiological turnover rate in humans, a sensitive parameter required for mechanistic pharmacokinetic and pharmacodynamic (PK/PD) modeling of biotherapeutics. Results from a stable isotope-labelled amino acid pulse-chase study in healthy human subjects followed by mass spectrometry showed that osteopontin undergoes very rapid turnover. PK/PD modeling and simulation of different theoretical scenarios reveal that achieving sufficient target coverage using antibodies can be very challenging mostly due to osteopontin’s fast turnover, as well as its relatively high plasma concentrations in human. Therapeutic antibodies against osteopontin would need to be engineered to have much extended PK than conventional antibodies, and be administered at high doses and with short dosing intervals.

Traditional Chinese medicine formula Bi-Qi capsule alleviates rheumatoid arthritis-induced inflammation, synovial hyperplasia, and cartilage destruction in rats

BACKGROUND

Traditional Chinese medicine (TCM) formula Bi-Qi capsule (Bi-Qi) is a commonly prescribed drug to treat rheumatoid arthritis (RA). However, the mechanism of Bi-Qi-mediated amelioration of RA pathogenesis is still a mystery. Collagen induced arthritis (CIA) in rats is an established model that shares many similarities with RA in humans. In this study we investigated the effect of Bi-Qi on the pathogenesis of CIA in rats.

METHODS

CIA was developed in Sprague-Dawley (S.D) rats (n = 60, female) and used as a model resembling RA in humans. Rats were treated with a high or moderate dose of Bi-Qi, or methotrexate (MTX). Effects of the treatment on local joint and systemic inflammation, synovial hyperplasia, cartilage destruction, and other main features in the pathogenesis of CIA were analyzed.

RESULTS

Inflamed and swollen ankles and joints were observed in arthritic rats, while Bi-Qi or MTX treatment alleviated these symptoms. Only the Bi-Qi moderate dose decreased RA-induced serum levels of tumor necrosis factor-alpha (TNF-α). Both Bi-Qi and MTX reduced the interleukin (IL)-18 serum level. Protein levels of cartilage oligomeric matrix protein and osteopontin in serum, synovium, and cartilage were elevated in arthritic rats, while Bi-Qi alleviated these effects. Synovial hyperplasia, inflammatory cell infiltration in synovium and a high degree of cartilage degradation was observed in RA, and Bi-Qi or MTX alleviated this effect. Bi-Qi at the moderate dose was the most effective in mitigating CIA-related clinical complications.

CONCLUSIONS

Our findings showed that Bi-Qi alleviates CIA-induced inflammation, synovial hyperplasia, cartilage destruction, and the other main features in the pathogenesis of CIA. This provides fundamental evidence for the anti-arthritic properties of Bi-Qi and corroborates the use of Bi-Qi TCM formula for the treatment of RA.

Adiponectin aggravates bone erosion by promoting osteopontin production in synovial tissue of rheumatoid arthritis

Background

We have previously reported that adiponectin (AD), an adipokine that is secreted by adipocytes, correlates well with progressive bone erosion in rheumatoid arthritis (RA). The exact mechanism of AD in promoting joint destruction remains unclear. Osteopontin (OPN) is required for osteoclast recruitment. We hypothesized that AD exacerbates bone erosion by inducing OPN expression in synovial tissue. This study aimed to evaluate a novel role for AD in RA.

Methods

The serum levels of AD and OPN were determined in 38 patients with RA, 40 patients with osteoarthritis (OA), and 20 healthy controls using enzyme-linked immunosorbent assay (ELISA). AD and OPN production were measured by double immunofluorescence in RA and OA synovial tissue. Quantitative real-time PCR and immunofluorescence were used to evaluate the mRNA and protein expression levels of OPN in RA synovial fibroblasts (RASFs) and OA synovial fibroblasts after pre-incubation with AD, respectively. Migration of the RAW264.7 osteoclast precursor cell line was assessed using the Transwell migration assay and co-culture system. Bone destruction and osteoclastogenesis were assessed by immunohistochemical staining, microcomputed tomography and tartrate-resistant acid phosphatase (TRAP) staining in AD-treated collagen-induced arthritis (CIA) mice with or without OPN silencing. The expression levels of OPN and integrin α_vβ₃ in the ankle joint tissues of the mice were examined by double immunofluorescence.

Results

Our results indicated that the AD and OPN expression levels increased noticeably and were associated with each other in the RA serum. The AD distribution was coincident with that of OPN in the RA synovial tissue. AD stimulation of RASFs increased OPN production in a dose-dependent manner. AD-treated RASFs promoted RAW264.7 cell migration, and the effect was blocked with a specific antibody against OPN. Silencing of OPN using lentiviral-OPN short hairpin RNA reduced the number of TRAP-positive osteoclasts and the extent of bone erosion in the AD-treated CIA mice. When bound to integrin α_vβ₃, OPN functions as a mediator of AD and osteoclasts.

Conclusions

Our study provides new evidence of AD involvement in bone erosion. AD induces the expression of OPN, which recruits osteoclasts and initiates bone erosion. These data highlight AD as a novel target for RA treatment.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1526-y) contains supplementary material, which is available to authorized users.

T Cells in Osteoarthritis: Alterations and Beyond

Although osteoarthritis (OA) has been traditionally regarded as a non-inflammatory disease, reports increasingly suggest that it is inflammatory, at least in certain patients. OA patients often exhibit inflammatory infiltration of synovial membranes by macrophages, T cells, mast cells, B cells, plasma cells, natural killer cells, dendritic cells, granulocytes, etc. Although previous reviews have summarized the knowledge of inflammation in the pathogenesis of OA, as far as we know, no report review our current understanding about T cells, especially, each T cell subtype, in the biology of OA. This review highlights the current understanding of the role of T cells in the pathogenesis of OA, with attention to Th1 cells, Th2 cells, Th9 cells, Th17 cells, Th22 cells, regulatory T cells, follicular helper T cells, cytotoxic T cells, T memory cells, and even unconventional T cells (e.g., γδ T cells and cluster of differentiation 1 restricted T cells). The findings highlight the importance of T cells to the development and progression of OA and suggest new therapeutic approaches for OA patients based on the manipulation of T-cell responses.

Endogenous bone morphogenetic protein 2 plays a role in vascular smooth muscle cell calcification induced by interleukin 6 in vitro

Systemic inflammation is involved in vascular calcification and cardiovascular disease which is the leading cause of mortality in rheumatoid arthritis (RA). A high level of serum interleukin (IL)-6 plays a key role in local and systemic inflammation in RA. However, the underlying mechanisms remain unclear. We established a human umbilical artery smooth muscle cell (HUASMC) culturing method to investigate the possible role of IL-6 on vascular calcification. HUASMCs were obtained from umbilical arteries of healthy neonates. To detect calcification effects, HUASMCs were treated with (experimental group) or without (control group) recombinant human (rh) IL-6. The calcium deposition stain and calcium concentrations were measured, as well as the mRNA and protein levels of the regulating factor of osteogenic differentiation-bone morphogenetic protein (BMP) 2 and those calcifying related molecules including bone-specific alkaline phosphatase (BAP), osteoprotegerin (OPG), and osteopontin (OPN). Our study showed that rhIL-6 induced calcification of HUASMCs in a time- and dose-dependent manner, and upregulated expressions of BMP2, BAP, OPG, and OPN of HUASMCs. We then used the anti-BMP2 siRNA to knockdown the expression of endogenous BMP2 to confirm its role. HUASMCs were transfected with negative siRNA (control group) or the valid anti-BMP2 siRNA (experimental group) before they were treated with rhIL-6. Cells transfected with negative siRNA without IL-6 stimulating served as the blank group. The results showed that anti-BMP2 siRNA markedly decreased expressions of BMP2, BAP, OPG, and OPN, and also partly reduced the calcification of HUASMCs induced by rhIL-6. Collectively, according to our study, rhIL-6 could induce the extracellular calcification and osteogenic differentiation of human artery smooth muscle cells through upregulating endogenous BMP2 in vitro. This may be one of the underlying mechanisms of the overwhelming vascular calcification in RA.

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.

Osteopontin inhibition of miR-129-3p enhances IL-17 expression and monocyte migration in rheumatoid arthritis

BACKGROUND

Osteopontin (OPN) is an important proinflammatory cytokine in rheumatoid arthritis (RA). Levels of OPN have been shown to be significantly correlated with interleukin-17 (IL-17) production and expression of Th17 cells in the synovial fluid of RA patients. Here, we investigated the role of OPN in monocyte migration, IL-17 production and osteoblasts.

METHODS

OPN and IL-17 expression profiles in osteoarthritis (OA) and RA synovial fluid were determined by enzyme-linked immunosorbent assay (ELISA). The expression of the microRNA, miR-129-3p, in osteoblasts was analyzed by real-time quantitative polymerase chain reaction (qPCR). Immunoreactive proteins were spotted by Western blotting. We used the collagen-induced arthritis (CIA) mouse model to investigate the role of OPN in monocyte migration during RA.

RESULTS

OPN and IL-17 expression were higher in RA synovial fluid as compared to OA samples. We also found that OPN promotes IL-17 expression in osteoblasts and thereby enhances monocyte migration via the Syk/PI3K/Akt signaling pathway. miR-129-3p expression was found to be negatively regulated by OPN via the Syk/PI3K/Akt signal cascade. In contrast, lentiviral vectors expressing short hairpin RNA inhibited OPN expression and ameliorated articular swelling, cartilage erosion and monocyte infiltration in the ankle joints of CIA mice.

CONCLUSION

To our knowledge, our study is the first to describe how OPN promotes monocyte migration by upregulating IL-17 expression in osteoblasts in RA disease.

SIGNIFICANCE

These findings indicate that OPN could serve as a potential therapeutic target for the treatment of RA.

Methylene tetrahydrofolate reductase, transforming growth factor-β1 and lymphotoxin-α genes polymorphisms and susceptibility to rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis is a widely prevalent autoimmune disorder with suggested genetic predisposition.

OBJECTIVES

The aim of this study is to detect the pattern of genetic polymorphism of methylene tetrahydrofolate reductase (MTHFR C677 T and A1298 C), transforming growth factor-β1 (TGF-β1 T869 C) and lymphotoxin-α (LT-α A252G) in patients having rheumatoid arthritis and correlate these patterns to disease activity and serum levels of tumor necrosis factor-alpha (TNF-α), B-Cell Activating Factor (BAFF), and osteopontin.

METHODS

A total of 194 subjects, 90 controls and 104 patients with rheumatoid arthritis were genotyped for MTHFR C677 T and A1298 C, TGF-β1 T869 C and LT-α A252G polymorphisms using a methodology based on PCR-RFLP. Also serum levels of TNF-α, osteopontin and BAFF were measured by ELISA kits.

RESULTS

The CT genotype and T allele of MTHFR C677 T and GG genotype and G allele of LT-α A252G are associated with the risk of RA and with higher levels of the pro-inflammatory cytokine, TNF-α in patients with rheumatoid arthritis.

CONCLUSION

Our findings suggest that there is association between MTHFR C677 T and LT-α A252G genes polymorphisms and increased risk of RA in this sample of Egyptian population.

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.

Matricellular proteins in drug delivery: Therapeutic targets, active agents, and therapeutic localization

Extracellular matrix is composed of a complex array of molecules that together provide structural and functional support to cells. These properties are mainly mediated by the activity of collagenous and elastic fibers, proteoglycans, and proteins such as fibronectin and laminin. ECM composition is tissue-specific and could include matricellular proteins whose primary role is to modulate cell-matrix interactions. In adults, matricellular proteins are primarily expressed during injury, inflammation and disease. Particularly, they are closely associated with the progression and prognosis of cardiovascular and fibrotic diseases, and cancer. This review aims to provide an overview of the potential use of matricellular proteins in drug delivery including the generation of therapeutic agents based on the properties and structures of these proteins as well as their utility as biomarkers for specific diseases.