Loss of imprinting of IGF2 characterises high IGF2 mRNA-expressing type of fibroblast-like synoviocytes in rheumatoid arthritis

Long Non-coding RNA Genes Polymorphisms H19 (rs2251375) and MALAT1 (rs3200401) Association with Rheumatoid Arthritis and Their Correlation with Disease Activity in a Cohort of Egyptian Patients: A Pilot Study

Rheumatoid arthritis (RA) is a chronic, progressive, inflammatory, autoimmune disease that could be disabling throughout its course. It affects people in their most reproductive years with relatively high morbidity and mortality. Long non-coding RNAs became one of the epigenetic mechanisms to prove a link to RA pathogenesis and development, including H19 and MALAT1 genes. These two genes' expressions had proved to increase in multiple diseases, attracting attention to their polymorphisms and their possible risk role. Assess the association between H19 SNP (rs2251375) and MALAT1 SNP (rs3200401) and the susceptibility of RA and its disease activity. In this pilot study, 200 hundred subjects (100 RA patients and 100 healthy controls) were investigated for a possible link between the polymorphisms H19 SNP (rs2251375) and MALAT1 SNP (3200401) and RA susceptibility and disease activity. RA-related investigations and clinical assessment were done. Real-time PCR genotyping of both SNPs was done using TaqMan® MGB probes. There was no association between the SNPs and risk of developing RA. However, both SNPs had a significant association with high disease activity. H19 SNP (rs2251375) heterozygous genotype CA had an association with elevated levels of ESR (p = 0.04) and higher DAS28-ESR score (p = 0.03). MALAT1 (rs3200401) C allele had an association with elevated ESR (p = 0.001), DAS28-ESR (p = 0.03), and DAS28-CRP (p = 0.007), while CC genotype had an association with DAS28-CRP (p = 0.015). Linkage disequilibrium and haplotyping of the alleles of both SNPs were analyzed as both genes are present on chromosome 11, but no significant association was found between any of the combinations of the alleles (p > 0.05), denoting that (rs2251375) and (rs3200401) are not in linkage disequilibrium. There is no association between H19 SNP (rs2251375) and MALAT1 SNP (rs3200401) and the susceptibility of RA. However, there is an association between H19 SNP (rs2251375) genotype CA and MALAT1 SNP (rs3200401) genotype CC with RA high disease activity.

Genomic imprinting analyses identify maternal effects as a cause of phenotypic variability in type 1 diabetes and rheumatoid arthritis

Imprinted genes, giving rise to parent-of-origin effects (POEs), have been hypothesised to affect type 1 diabetes (T1D) and rheumatoid arthritis (RA). However, maternal effects may also play a role. By using a mixed model that is able to simultaneously consider all kinds of POEs, the importance of POEs for the development of T1D and RA was investigated in a variance components analysis. The analysis was based on Swedish population-scale pedigree data. With P = 0.18 (T1D) and P = 0.26 (RA) imprinting variances were not significant. Explaining up to 19.00% (± 2.00%) and 15.00% (± 6.00%) of the phenotypic variance, the maternal environmental variance was significant for T1D (P = 1.60 × 10-24) and for RA (P = 0.02). For the first time, the existence of maternal genetic effects on RA was indicated, contributing up to 16.00% (± 3.00%) of the total variance. Environmental factors such as the social economic index, the number of offspring, birth year as well as their interactions with sex showed large effects.

Insulin-Like Growth Factor Binding Protein 6 in Rheumatoid Arthritis: A Possible Novel Chemotactic Factor?

Objectives

Immune cell migration from the bloodstream to target tissues is a hallmark of rheumatoid arthritis (RA) pathogenesis. The role of chemoattractants, mainly chemokines, and their possible targeting for therapeutic purposes have been under intense investigation over the last few years but the results were not as satisfactory as expected. The insulin-like growth factor binding protein 6 (IGFBP6), a direct inhibitor of insulin-like growth factor (IGF)-II, also exerts IGF-independent effects including tumor cell migration in vitro. We aimed to assess the expression of this protein in serum, synovial fluid, and synovial tissue (ST) of RA patients and to identify its possible chemotactic role in this disorder.

Methods

IGFBP6 was measured in RA patients and healthy donors (HD) sera by Luminex xMAP^® technology and in ST of RA patients and osteoarthritis (OA) controls by immunofluorescence. The identification of circulating IGFBP6⁺ cells was evaluated by flow cytometry and an in vitro migration assay was arranged.

Results

We demonstrated that IGFBP6 is able to induce greater in vitro migration of RA as compared to HD and OA T lymphocytes and is overexpressed in serum and ST of RA patients. This in vitro chemotactic activity can be partially inhibited by dexamethasone.

Conclusion

Our findings suggest a pathogenic role of IGFBP6 in RA and support its possible targeting for therapeutic purposes.

Genomic imprinting: A missing piece of the Multiple Sclerosis puzzle?

Evidence for parent-of-origin effects in complex diseases such as Multiple Sclerosis (MS) strongly suggests a role for epigenetic mechanisms in their pathogenesis. In this review, we describe the importance of accounting for parent-of-origin when identifying new risk variants for complex diseases and discuss how genomic imprinting, one of the best-characterized epigenetic mechanisms causing parent-of-origin effects, may impact etiology of complex diseases. While the role of imprinted genes in growth and development is well established, the contribution and molecular mechanisms underlying the impact of genomic imprinting in immune functions and inflammatory diseases are still largely unknown. Here we discuss emerging roles of imprinted genes in the regulation of inflammatory responses with a particular focus on the Dlk1 cluster that has been implicated in etiology of experimental MS-like disease and Type 1 Diabetes. Moreover, we speculate on the potential wider impact of imprinting via the action of imprinted microRNAs, which are abundantly present in the Dlk1 locus and predicted to fine-tune important immune functions. Finally, we reflect on how unrelated imprinted genes or imprinted genes together with non-imprinted genes can interact in so-called imprinted gene networks (IGN) and suggest that IGNs could partly explain observed parent-of-origin effects in complex diseases. Unveiling the mechanisms of parent-of-origin effects is therefore likely to teach us not only about the etiology of complex diseases but also about the unknown roles of this fascinating phenomenon underlying uneven genetic contribution from our parents. This article is part of a Directed Issue entitled: Epigenetics dynamics in development and disease.

Rheumatoid arthritis progression mediated by activated synovial fibroblasts

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by synovial hyperplasia and progressive joint destruction. Rheumatoid arthritis synovial fibroblasts (RASFs) are leading cells in joint erosion and contribute actively to inflammation. RASFs show an activated phenotype that is independent of the inflammatory environment and requires the combination of several factors. Although new aspects regarding RASF activation via matrix degradation products, epigenetic modifications, inflammatory factors, Toll-like receptor (TLR) activation and others have recently been uncovered, the primary pathophysiological processes in early arthritis leading to permanent activation are mostly unknown. Here, we review new findings regarding RASF activation and their altered behavior that contribute to matrix destruction and inflammation as well as their potential to spread RA.