A5.16 miRNA expression profile in Bulgarian patients with rheumatoid arthritis compared to patients with osteoarthritis and healthy controls in regard to their use as biomarkers in the clinical practice

Background and Objectives The pathogenesis of rheumatoid arthritis (RA) is still unknown. Recent data suggest that micro-ribonucleic acids (microRNAs) and their targets are involved in the inflammatory process and may perpetuate the chronic joint involvement. The aim of the study is to compare the expression of certain microRNA in peripheral blood and synovial fluid in Bulgarian patients with RA in relation to their clinical picture and laboratory data. The expression profile of RA samples was compared with samples from patients with osteoarthritis (OA) and healthy controls (HCs). The chosen microRNAs were analysed in regard to their use as biomarkers for disease activity and progression. Materials and Methods 80 RA patients according to the 1987 ACR criteria (17 drug naïve, 29 corticosteroid naïve, 31 DMARDs naïve, 31 biologic naïve patients), 20 OA patients and 20 healthy controls were included in the study. Paired peripheral blood (PB) and synovial fluid (SF) samples were used for detecting miRNA expression. The PB samples were collected in PAX gene tubes and SF samples were collected and stored with RNeasy Protect Cell Mini kit (according to manufacturer’s protocol). MicroRNAs from the samples were isolated and PCR (SYBR green technology) was further performed. The results were analysed in regard to the clinical picture including radiological stage, the laboratory data for disease activity and the immunological status. Preliminary results Our preliminary data showed differences in the expression profile of the chosen miRNAs between PB and SF in RA patients compared to OA and HCs. The miRNA profile was related to the clinical picture in these patients as well as to their immunological status. The further statistical analysis will show if these microRNAs can be used as biomarkers in RA and future studies of the functional rule (microRNA targets) will reveal new aspects of RA pathogenesis. Conclusions The relationship between the clinical picture of RA patients, the laboratory data including immunological status as ANA positivity, RF subclasses, aCCP positivity and DAS 28 score with the expression profile of microRNAs in body fluids will eventually show if these microRNAs can be used as blood/synovial fluid based biomarkers in the clinical practice for patients with RA early in the disease course. This is the first miRNA study in Bulgarian patients with rheumatic diseases.