AB0101 INCREASED DNA DAMAGE AND LACK OF DNA REPAIR IN FIBROBLAST-LIKE SYNOVIOCYTES OF INDIVIDUALS AT RISK OF DEVELOPING RHEUMATOID ARTHRITIS

Abstract

BackgroundRheumatoid arthritis (RA) is a chronic inflammatory immune-mediated disease leading to synovial tissue inflammation and bone destruction. Inflammation-induced DNA damage in fibroblast-like synoviocytes (FLS) is thought to play an important role in RA pathogenesis. However, since a recent functional genomics study revealed a causal role for FLS in the genetic susceptibility of RA and synovial inflammation is absent in autoantibody positive individuals at risk for RA, we aimed to investigate whether DNA damage in FLS is present before onset of disease.ObjectivesDetermine the extent of DNA damage in FLS and their capacity to repair this damage during the earliest phases of systemic autoimmunity.MethodsWe included individuals with arthralgia who were IgM rheumatoid factor (RF) and/or anti-citrullinated protein antibody (ACPA) positive but without any evidence of arthritis (RA-risk individuals, n=6), RA patients (n=6), osteoarthritis (OA) patients (n=6) and controls without inflammatory disease (n=6). Synovial tissue biopsies were collected either during joint surgery or individuals underwent a mini-arthroscopy of a knee joint. Subsequently, FLS were in vitro expanded upon enzymatic synovial tissue digestion. DNA damage in FLS (passage 6) was assessed by immunofluorescence staining for yH2AX. DNA damage repair was assessed by first irradiating the cells with 1 gray to induce DNA damage and assess yH2AX staining directly and after 3 and 24 hours of culture to allow for DNA repair.ResultsPreliminary immunofluorescence staining for yH2AX shows that DNA damage is present in RA-risk and RA FLS to more extent compared with FLS from non-inflammatory controls. OA FLS exhibit even more DNA damage and their nuclei show signs of impaired chromosomal segregation, forming micronuclei with high yH2AX staining intensity. Overall, DNA damage repair is slower in FLS from RA-risk individuals, RA and OA patients compared with controls as shown by persistent yH2AX staining after inducing DNA damage.ConclusionThese findings reveal increased DNA damage and concomitant impaired DNA repair in FLS of not only patients with synovial inflammation but also in FLS from RA-risk individuals, suggesting that DNA damage is already present in absence of overt synovial tissue inflammation and before clinical disease onset. More research is needed to investigate DNA damage or lack of DNA repair as potential driver in development of RA.Disclosure of InterestsNone declared