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1.  Epigenetic contributions in the development of rheumatoid arthritis 
Rheumatoid arthritis (RA) is an autoimmune disease, characterized by chronic inflammation of the joints with severe pain and swelling, joint damage and disability, which leads to joint destruction and loss of function. Despite extensive research efforts, the underlying cause for RA is still unknown and current therapies are more or less effective in controlling symptoms but still fail to cure the disease. In recent years, epigenetic modifications were found to strongly contribute to the development of RA by affecting diverse aspects of the disease and modifying gene expression levels and behavior of several cell types, first and foremost joint resident synovial fibroblasts (SF). RASF are the most common cell type at the site of invasion. Owing to their aggressive, intrinsically activated phenotype, RASF are active contributors in joint damage. RASF are characterized by their ability to secrete cytokines, chemokines and joint-damaging enzymes. Furthermore, these cells are resistant to apoptosis, leading to hyperplasia of the synovium. In addition, RASF have invasive and migratory properties that could lead to spreading of the disease to unaffected joints. Epigenetic modifications, including DNA methylation and post-translational histone modifications, such as histone (de)acetylation, histone methylation and histone sumoylation were identified as regulatory mechanisms in controlling aggressive cell activation in vitro and in disease outcome in animal models in vivo. In the last 5 years, the field of epigenetics in RA has impressively increased. In this review we consider the role of diverse epigenetic modifications in the development of RA, with a special focus on epigenetic modifications in RASF.
doi:10.1186/ar4074
PMCID: PMC3674613  PMID: 23164162
2.  Hypoxia. Hypoxia in the pathogenesis of systemic sclerosis 
Autoimmunity, microangiopathy and tissue fibrosis are hallmarks of systemic sclerosis (SSc). Vascular alterations and reduced capillary density decrease blood flow and impair tissue oxygenation in SSc. Oxygen supply is further reduced by accumulation of extracellular matrix (ECM), which increases diffusion distances from blood vessels to cells. Therefore, severe hypoxia is a characteristic feature of SSc and might contribute directly to the progression of the disease. Hypoxia stimulates the production of ECM proteins by SSc fibroblasts in a transforming growth factor-β-dependent manner. The induction of ECM proteins by hypoxia is mediated via hypoxia-inducible factor-1α-dependent and -independent pathways. Hypoxia may also aggravate vascular disease in SSc by perturbing vascular endothelial growth factor (VEGF) receptor signalling. Hypoxia is a potent inducer of VEGF and may cause chronic VEGF over-expression in SSc. Uncontrolled over-expression of VEGF has been shown to have deleterious effects on angiogenesis because it leads to the formation of chaotic vessels with decreased blood flow. Altogether, hypoxia might play a central role in pathogenesis of SSc by augmenting vascular disease and tissue fibrosis.
doi:10.1186/ar2598
PMCID: PMC2688169  PMID: 19473554
3.  Epigenetic modifications in rheumatoid arthritis 
Over the last decades, genetic factors for rheumatoid diseases like the HLA haplotypes have been studied extensively. However, during the past years of research, it has become more and more evident that the influence of epigenetic processes on the development of rheumatic diseases is probably as strong as the genetic background of a patient. Epigenetic processes are heritable changes in gene expression without alteration of the nucleotide sequence. Such modifications include chromatin methylation and post-translational modification of histones or other chromatin-associated proteins. The latter comprise the addition of methyl, acetyl, and phosphoryl groups or even larger moieties such as binding of ubiquitin or small ubiquitin-like modifier. The combinatory nature of these processes forms a complex network of epigenetic modifications that regulate gene expression through activation or silencing of genes. This review provides insight into the role of epigenetic alterations in the pathogenesis of rheumatoid arthritis and points out how a better understanding of such mechanisms may lead to novel therapeutic strategies.
doi:10.1186/ar2500
PMCID: PMC2592785  PMID: 18947370
4.  Cells of the synovium in rheumatoid arthritis. Synovial fibroblasts 
For some time synovial fibroblasts have been regarded simply as innocent synovial cells, mainly responsible for synovial homeostasis. During the past decade, however, a body of evidence has accumulated illustrating that rheumatoid arthritis synovial fibroblasts (RASFs) are active drivers of joint destruction in rheumatoid arthritis. Details regarding the intracellular signalling cascades that result in long-term activation and synthesis of proinflammatory molecules and matrix-degrading enzymes by RASFs have been analyzed. Molecular, cellular and animal studies have identified various interactions with other synovial and inflammatory cells. This expanded knowledge of the distinct role played by RASFs in the pathophysiology of rheumatoid arthritis has moved these fascinating cells to the fore, and work to identify targeted therapies to inhibit their joint destructive potential is underway.
doi:10.1186/ar2337
PMCID: PMC2246247  PMID: 18177509
5.  Proteinases in the joint: clinical relevance of proteinases in joint destruction 
Proteinases are involved in essential steps in cartilage and bone homeostasis. Consequently, efforts have been made to establish their potential role in the pathology of rheumatic conditions such as rheumatoid arthritis, osteoarthritis and spondyloarthritis. Matrix metalloproteinases (MMPs) are sensitive markers of disease severity and response to treatment, and therefore they have potential in the assessment of rheumatic diseases. Despite disappointing early results with synthetic inhibitors of MMPs, there is still much scope for developing effective and safe MMPs inhibitors, and consequently to deliver new options to inhibit joint destruction.
doi:10.1186/ar2304
PMCID: PMC2212555  PMID: 18001502
6.  Fibroblast biology: Role of synovial fibroblasts in the pathogenesis of rheumatoid arthritis 
Arthritis Research  2000;2(5):361-367.
There is growing evidence that activated synovial fibroblasts, as part of a complex cellular network, play an important role in the pathogenesis of rheumatoid arthritis. In recent years, significant progress has been made in elucidating the specific features of these fibroblasts. It has been understood that although macrophage and lymphocyte secreted factors contribute to their activation, rheumatoid arthritis synovial fibroblasts (RA-SFs) do not merely respond to stimulation by pro-inflammatory cytokines, but show a complex pattern of molecular changes also maintained in the absence of external stimulation. This pattern of activation is characterized by alterations in the expression of regulatory genes and signaling cascades, as well as changes in pathways leading to apoptosis. These together result in the upregulation of adhesion molecules that mediate the attachment of RA-SFs to the extracellular matrix and in the overexpression of matrix degrading enzymes that mediate the progressive destruction of the joints. In addition, activated RA-SFs exert specific effects on other cell types such as macrophages and lymphocytes. While the initiating step in the activation of RA-SFs remains elusive, several key pathways of RA-SF activation have been identified. However, there is so far no single, specific marker for this phenotype of RA-SF. It appears that activated RA-SFs are characterized by a set of specific properties which together lead to their aggressive behavior.
doi:10.1186/ar113
PMCID: PMC130137  PMID: 11094449
fibroblasts; rheumatoid arthritis
7.  EULAR recommendations for terminology and research in individuals at risk of rheumatoid arthritis: report from the Study Group for Risk Factors for Rheumatoid Arthritis 
Annals of the Rheumatic Diseases  2012;71(5):638-641.
The Study Group for Risk Factors for Rheumatoid Arthritis was established by the EULAR Standing Committee on Investigative Rheumatology to facilitate research into the preclinical and earliest clinically apparent phases of rheumatoid arthritis (RA). This report describes the recommendation for terminology to be used to define specific subgroups during different phases of disease, and defines the priorities for research in this area. Terminology was discussed by way of a three-stage structured process: A provisional list of descriptors for each of the possible phases preceding the diagnosis of RA were circulated to members of the study group for review and feedback. Anonymised comments from the members on this list were fed back to participants before a 2-day meeting. 18 participants met to discuss these data, agree terminologies and prioritise important research questions. The study group recommended that, in prospective studies, individuals without RA are described as having: genetic risk factors for RA; environmental risk factors for RA; systemic autoimmunity associated with RA; symptoms without clinical arthritis; unclassified arthritis; which may be used in a combinatorial manner. It was recommended that the prefix ‘pre-RA with:’ could be used before any/any combination of the five points above but only to describe retrospectively a phase that an individual had progressed through once it was known that they have developed RA. An approach to dating disease onset was recommended. In addition, important areas for research were proposed, including research of other tissues in which an adaptive immune response may be initiated, and the identification of additional risk factors and biomarkers for the development of RA, its progression and the development of extra-articular features. These recommendations provide guidance on approaches to describe phases before the development of RA that will facilitate communication between researchers and comparisons between studies. A number of research questions have been defined, requiring new cohorts to be established and new techniques to be developed to image and collect material from different sites.
doi:10.1136/annrheumdis-2011-200990
PMCID: PMC3329228  PMID: 22387728

Results 1-7 (7)