PATHOGENESIS OF RHEUMATOID ARTHRITIS: THE INTERSECTION OF GENETICS AND EPIGENETICS.

Rheumatoid arthritis is a synovial inflammatory disease marked by joint infiltration by immune cells and damage to the extracellular matrix. Although genetics plays a critical role in heritability and its pathogenesis, the relative lack of disease concordance in identical twins suggests that noncoding influences can affect risk and severity. Environmental stress, which can be reflected in the genome as altered epigenetic marks, also contributes to gene regulation and contributes to disease mechanisms. Studies on DNA methylation suggest that synovial cells, most notably fibroblast-like synoviocytes, are imprinted in rheumatoid arthritis with epigenetic marks and subsequently assume an aggressive phenotype. Even more interesting, the synoviocyte marks are not only disease specific but can vary depending on the joint of origin. Understanding the epigenetic landscape using unbiased methods can potentially identify nonobvious pathways and genes that that are responsible for synovial inflammation as well as the diversity of responses to targeted agents. The information can also be leveraged to identify novel therapeutic approaches.