Geo-epidemiology of autoantibodies in rheumatoid arthritis: comparison between four ethnically diverse populations

MSC-microvesicles protect cartilage from degradation in early rheumatoid arthritis via immunoregulation

OBJECTIVE

As research into preclinical rheumatoid arthritis (pre-RA) has advanced, a growing body of evidence suggests that abnormalities in RA-affected joint cartilage precede the onset of arthritis. Thus, early prevention and treatment strategies are imperative. In this study, we aimed to explore the protective effects of mesenchymal stem cell (MSC)-derived microvesicles (MVs) on cartilage degradation in a collagen-induced arthritis (CIA) mouse model.

METHODS

A CIA mouse model was established to observe early pathological changes in cartilage (days 21-25) through histological and radiological examinations. On day 22, MSCs-MVs were intravenously injected into the mice with CIA. Radiological, histological, and flow cytometric examinations were conducted to observe inflammation and cartilage changes in these mice compared to the mice with CIA and the control mice. In vitro, chondrocytes were cultured with inflammatory factors such as IL-1β and TNFα to simulate inflammatory damage to cartilage. After the addition of MVs, changes in inflammatory levels and collagen expression were measured via Western blotting, immunofluorescence, enzyme-linked immunosorbent assays (ELISAs), and quantitative PCR to determine the role of MVs in maintaining chondrocytes.

RESULTS

MSC-MVs expressed vesicular membrane proteins (CD63 and Annexin V) and surface markers characteristic of MSCs (CD44, CD73, CD90, and CD105). In the early stages of CIA in mice, a notable decrease in collagen content was observed in the joint cartilage. In mice with CIA, injection of MSCs-MVs resulted in a significant reduction in the peripheral blood levels of IL-1β, TNFα, and IL-6, along with a decrease in the ratio of proinflammatory T and B cells. Additionally, MSC-MVs downregulated the expression of IL-1β, TNFα, MMP-13, and ADAMTS-5 in cartilage while maintaining the stability of type I and type II collagen. These MVs also attenuated the destruction of cartilage, which was evident on imaging. In vitro experiments demonstrated that MSC-MVs effectively suppressed the secretion of the inflammatory factors IL-1β, TNFα, and IL-6 in stimulated peripheral blood mononuclear cells (PBMCs).

CONCLUSIONS

MSCs-MVs can inhibit the decomposition of the inflammation-induced cartilage matrix by regulating immune cell inflammatory factors to attenuate cartilage destruction. MSC-MVs are promising effective treatments for the early stages of RA.

Gut microbial metabolite targets HDAC3-FOXK1-interferon axis in fibroblast-like synoviocytes to ameliorate rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease. Early studies hold an opinion that gut microbiota is environmentally acquired and associated with RA susceptibility. However, accumulating evidence demonstrates that genetics also shape the gut microbiota. It is known that some strains of inbred laboratory mice are highly susceptible to collagen-induced arthritis (CIA), while the others are resistant to CIA. Here, we show that transplantation of fecal microbiota of CIA-resistant C57BL/6J mice to CIA-susceptible DBA/1J mice confer CIA resistance in DBA/1J mice. C57BL/6J mice and healthy human individuals have enriched B. fragilis than DBA/1J mice and RA patients. Transplantation of B. fragilis prevents CIA in DBA/1J mice. We identify that B. fragilis mainly produces propionate and C57BL/6J mice and healthy human individuals have higher level of propionate. Fibroblast-like synoviocytes (FLSs) in RA are activated to undergo tumor-like transformation. Propionate disrupts HDAC3-FOXK1 interaction to increase acetylation of FOXK1, resulting in reduced FOXK1 stability, blocked interferon signaling and deactivation of RA-FLSs. We treat CIA mice with propionate and show that propionate attenuates CIA. Moreover, a combination of propionate with anti-TNF etanercept synergistically relieves CIA. These results suggest that B. fragilis or propionate could be an alternative or complementary approach to the current therapies.

Diagnostic value of anti-integrin αvβ6 antibodies in ulcerative colitis

Ulcerative colitis (UC)-related mucosal inflammation is characterized by the production of various autoantibodies with limited clinical relevance. Recent studies have shown that circulating levels of IgG against integrin αvβ6 are increased in UC patients as compared to Crohn's disease (CD) patients and healthy controls (HC). The present study assessed the diagnostic value of circulating IgG anti-αvβ6 in UC. Sera were prospectively collected from 108 outpatients with UC, 103 patients with CD, and 62 HC, and the levels of IgG anti-αvβ6 were measured using a commercially available ELISA kit. The cut-off for positive results was defined as the 95th percentile of the values of the autoantibodies in HC serum samples. Levels of IgG anti-αvβ6 were significantly higher in UC than in CD patients, including those with colonic localization, and HC. Fifty-six of the 108 (51.8%) UC patients had a positive test whereas only 17/103 (16.5%) patients with CD, and among these, 4/16 (25%) patients with colonic CD, were positive. In UC, there was no statistical difference between patients with IgG anti-αvβ6 positivity and those negative in terms of clinical disease activity, fecal calprotectin values, and disease extent. The sensitivity, specificity, predictive positive value, and predictive negative value of the test to differentiate between UC and CD were 51.9% (C.I.42.4-61.3), 83.5% (C.I. 76.3-90.7), 76.7% (C.I. 67.0-86.4), and 62.3% (C.I. 54.2-70.4) respectively. Our study confirms that anti-αvβ6 antibodies are demonstrable in the serum of the majority of UC patients and suggests the necessity of further research to understand if the anti-αvβ6 antibody determination could have a place in the clinical decision-making of IBD.

Assessment of anti-malondialdehyde-acetaldehyde antibody frequencies in rheumatoid arthritis with new data from two independent cohorts, meta-analysis, and meta-regression

BACKGROUND

Autoantibodies are critical elements in RA pathogenesis and clinical assessment. The anti-malondialdehyde-acetaldehyde (anti-MAA) antibodies are potentially useful because of their claimed high sensitivity for all RA patients, including those lacking RF and anti-CCP antibodies. Therefore, we aimed to replicate these findings.

METHODS

We independently attempted replication in Santiago and Barcelona using sera from 517 and 178 RA patients and 272 and 120 healthy controls, respectively. ELISA protocols for anti-MAA antibodies included five antigens (human serum albumin in three formulations, fibrinogen, and a synthetic peptide) and assays for the IgG, IgM, and IgA isotypes. We integrated our results with information found by searching the Web of Science for reports of anti-MAA antibodies in RA. The available patients (4989 in 11 sets) were included in a meta-analysis aimed at heterogeneity between studies. Factors accounting for heterogeneity were assessed with meta-regression.

RESULTS

The sensitivity of anti-MAA antibodies in our RA patients was low, even in seropositive patients, with the percentage of positives below 23% for all ELISA conditions. Our results and bibliographic research showed IgG anti-MAA positive patients ranging from 6 to 92%. The extreme between-studies heterogeneity could be explained (up to 43%) in univariate analysis by sex, African ethnicity, the site of study, or recruitment from the military. The best model, including African ancestry and smoking, explained a high heterogeneity fraction (74%).

CONCLUSION

Anti-MAA antibody sensitivity is extremely variable between RA patient collections. A substantial fraction of this variability cannot be attributed to ELISA protocols. On the contrary, heterogeneity is determined by complex factors that include African ethnicity, smoking, and sex.

The Role of Autophagy as a Trigger of Post-Translational Modifications of Proteins and Extracellular Vesicles in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease, characterized by persistent joint inflammation, leading to cartilage and bone destruction. Autoantibody production is directed to post-translational modified (PTM) proteins, i.e., citrullinated or carbamylated. Autophagy may be the common feature in several types of stress (smoking, joint injury, and infections) and may be involved in post-translational modifications (PTMs) in proteins and the generation of citrullinated and carbamylated peptides recognized by the immune system in RA patients, with a consequent breakage of tolerance. Interestingly, autophagy actively provides information to neighboring cells via a process called secretory autophagy. Secretory autophagy combines the autophagy machinery with the secretion of cellular content via extracellular vesicles (EVs). A role for exosomes in RA pathogenesis has been recently demonstrated. Exosomes are involved in intercellular communications, and upregulated proteins and RNAs may contribute to the development of inflammatory arthritis and the progression of RA. In RA, most of the exosomes are produced by leukocytes and synoviocytes, which are loaded with PTM proteins, mainly citrullinated proteins, inflammatory molecules, and enzymes that are implicated in RA pathogenesis. Microvesicles derived from cell plasma membrane may also be loaded with PTM proteins, playing a role in the immunopathogenesis of RA. An analysis of changes in EV profiles, including PTM proteins, could be a useful tool for the prevention of inflammation in RA patients and help in the discovery of personalized medicine.