To investigate the association between immunohistopathological and morphological features of synovitis in rheumatoid arthritis and the amounts of collagen degradation products pyridinoline and deoxypyridinoline in the synovial tissue and in body fluids in order to discover potential markers of erosive disease.
Histopathological analysis of synovial tissue samples from 22 patients with RA was performed according to the histopathologic scoring system of RA synovitis by P. Stiehl. Accordingly, the samples were (a) classified into type I synovitis, type II synovitis, or undifferentiated synovitis and were (b) characterized for local features of disease activity, including basic activity and actual activity. The contents of pyridinoline and deoxypyridinoline were measured in the synovial tissue, the synovial fluid, serum and urine by HPLC analysis.
The amounts of pyridinoline in synovial tissue samples characterized by type II synovitis were 1.7-fold and 2.7-fold higher compared with those with type I synovitis and undifferentiated synovitis, respectively. In contrast, the content of deoxypyridinoline was not different between the histopathologic types of synovitis. At the same time, increased amounts of pyridinoline, but not deoxypyridinoline, were detected in synovial tissue samples with basic activity or actual activity grade II compared with synovial tissue samples with basic activity or actual activity grade I. The concentrations of both collagen degradation products in the synovial fluid, serum and urine did not differ between patients when they were analyzed either for histopathologic types of synovitis or local disease activity.
The amount of cartilage collagen degradation product pyridinoline in synovial tissue is positively correlated with the histopathological grading of local disease activity. Furthermore, the increased amounts of pyridinoline in synovial tissue samples with type II synovitis suggest a more erosive course of RA in patients with this type of synovitis.