Rheumatoid Arthritis: Karouzakis E

Karouzakis E, Gay RE, Gay S, Neidhart M. · Department of Rheumatology, University Hospital Zurich, Zurich, Switzerland. · Nat Rev Rheumatol. · Pubmed #19412193 No free full text.

Abstract: Rheumatoid arthritis synovial fibroblasts (RASFs) are the effector cells of cartilage and bone destruction. These cells show an 'intrinsically' activated and aggressive phenotype that results in the increased production of matrix-degrading enzymes and adhesion molecules, and is conserved over long-term passage in vitro. The three main mechanisms of epigenetic control -- DNA methylation, histone modifications and microRNA activity -- interact in the development of the RASF phenotype. The extent of global DNA methylation is reduced in synoviocytes in situ and RASFs in vitro. In addition, histone hyperacetylation occurs and specific microRNAs are expressed in RASFs. Normal synovial fibroblasts cultured in a hypomethylating milieu acquire an activated phenotype similar to that of RASFs. These findings suggest that epigenetic control, in particular the control of DNA methylation, is deficient in RASFs. Genome-wide analyses of the epigenome will enable the detection of additional genes involved in the pathogenesis of rheumatoid arthritis, the identification of epigenetic biomarkers, and potentially the development of a therapeutic regimen that targets activated RASFs.

Karouzakis E, Neidhart M, Gay RE, Gay S. · Center of Experimental Rheumatology, University Hospital Zurich, Switzerland. · Immunol Lett. · Pubmed #16824621 No free full text.

Abstract: Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with joint destruction. Synovial fibroblasts are key players in this pathological process. They favorise a pro-inflammatory environment in the synovial tissue, interact with the immune system and regulate the differentiation of monocytes into osteoclasts. Synovial hyperplasia is another characteristic of RA, reflecting not only an imbalance between proliferation and apoptosis, but also the migration of cells into the synovial tissue. Gene transfer experiments have been used as important tools for the understanding of molecular and cellular changes that characterize the activated RA synovial fibroblasts. Activated synovial fibroblasts can invade cartilage and bone. Synovial activation is driven by cytokines, such as TNFalpha and IL-1, as well as IL-15, 16, 17, 18, 22, 23, but also by cytokine-independent mechanisms that involve the innate immune system (i.e. TLRs), a unique communication network of microparticles and epigenetic changes (e.g. L1 retroelements).