Ultrastructural characteristics of synovial fluid cells in rheumatoid arthritis and osteoarthritis

Abstract

Aim The aim of the study was to evaluate the range of activation changes of polymorphonuclear leukocytes and the ratio of apoptosis and necrosis in synovial cells of patients with rheumatoid arthritis (RA) and osteoarthritis (OA), to study and compare the ultrastructural features of synovial fluid (SF) cells from RA and OA patients, to correlate it to activities of the diseases, and to produce microscopic translation to the events that occurred in the joint. Patients and methods Synovial effusions were aspirated from the knee joints of patients with RA (seven samples) and with primary OA (14 samples). Cytospin preparations were processed for transmission electron microscopy and assessed for the incidence of the neutrophil granulocytes, the dominating cell population in the arthritic SF, apoptosis, and cytophagocytic cells (CPCs) in the SF. Results In all samples under investigation, most of the synovial effusion cells had intact ultrastructure with a certain amount of apoptotic cells dominating over the cells with signs of necrosis and with few CPC. The highest rate of apoptosis was discovered in the synovial effusions of patients with RA and the lowest in those with OA; in addition, the incidence of CPC was lower in patients with OA. In RA, the current disease activity correlated with the incidence of the neutrophil granulocytes and of the apoptotic cells. Conclusion These data suggest that, in RA, despite exposure to the antiapoptotic signals, apoptosis of the synovial effusion polymorphonuclear leukocytes is maintained at a significantly higher level than in OA, providing elimination of the neutrophils accumulating in the joint cavity, and thus stimulating resolution of joint inflammation.