Reelin levels are increased in synovial fluid of patients with rheumatoid arthritis

Objectives. To evaluate the presence and the glycosylation pattern of reelin in synovial fluid and serum of patients affected by different rheumatic pathologies. Methods. Reelin levels were evaluated in patients affected by rheumatoid arthritis (RA), psoriatic arthritis (PsA), spondyloarthritis (SpA) and osteoarthritis (OA). Reelin semi-quantitative assays were performed by western blot. The glycosylation pattern was evaluated by immunoblotting performed by sepharose conjugated lectins. RT-PCR was used to detect the presence of mRNA encoding for reelin and its receptors. Results. Reelin is detectable in both sinovial fluids and sera and its levels are more elevated in patients affected by RA with respect to those affected by other inflammatory and non inflammatory joint diseases. The glycosylation pattern of the protein differs in synovial fluid and serum. Fibroblast-like synoviocytes (FLS) express the mRNAs encoding for reelin and its receptors. Conclusions. Since its levels are higher in RA then in the other analysed pathologies, reelin can represent a candidate suitable for the differential diagnosis of this pathology. Moreover, the observation that this protein is encoded by FLS and differentially glycosylated in blood and synovial fluid supports the hypothesis that it is locally produced in the joints, where it could play an important role in RA development and maintenance.