Connective tissue activation. xxxv. detection of connective tissue activating peptide–iii isoforms in synovium from osteoarthritis and rheumatoid arthritis patients: patterns of interaction with other synovial cytokines in cell culture

Objective. To determine whether extracts of unincubated osteoarthritis (OA) and rheumatoid arthritis (RA) synovial tissue contain connective tissue activating peptide–III (CTAP‐III) isoforms and prostaglandin E 2 (PGE 2 ), and whether such extracts have growth‐promoting activity, and to determine whether binary combinations of CTAP‐III with other cytokines reported to be present in synovial tissue lead to synergistic, additive, or inhibitory effects on growth. Methods. Acid–ethanol extracts of human synovium were examined for growth‐promoting activity by measuring formation of 14 C‐glycosaminoglycan ( 14 CGAG) and 3 H‐DNA in synovial cell cultures; PGE 2 was measured by enzyme immunoassay, and CTAP‐III isoforms were identified by Western blotting of extracted proteins separated by sodium dodecyl sulfate–polyacrylamide gel electrophoresis. Growth‐promoting activity of CTAP‐III and other cytokines was tested in synovial cultures treated with the agonists singly and in binary combination, by measuring changes in synthesis of 14 C‐GAG and 3 H‐DNA. Results. Platelet‐derived CTAP‐III and a cleavage isoform with the electrophoretic mobility of CTAP‐III–des 1–15/neutrophil‐activating peptide–2 (NAP‐2) and PGE 2 were found in biologically active extracts of synovial samples from patients with RA and OA. Five growth factors (recombinant epidermal growth factor [rEGF], recombinant interleukin‐1β [rIL‐1β], basic fibroblast growth factor [bFGF], PGE 1 , and PGE 2 ) in binary combination with CTAP‐III showed synergism in stimulating GAG synthesis; two (recombinant platelet‐derived growth factor type BB [rPDGF‐BB] and recombinant transforming growth factor β [rTGFβ]) had an additive effect. In combination with CTAP‐III, rEGF and rPDGF‐BB had a synergistic effect in promoting DNA synthesis, rTGFβ and rbFGF had an additive effect, and rIL‐1β, PGE 1 , and PGE 2 were antagonistic. Conclusions. The results suggest that, in addition to endogenous factors, CTAP‐III and other plateletderived cytokines may play roles in regulating synovial cell metabolism in RA and OA, and that combinations of growth factors may be more significant than single agents in amplification or suppression of important cell functions.