Rheumatoid synovial cell morphologic changes induced by a mononuclear cell factor in culture

Adherent rheumatoid synovial cells in culture produce large amounts of prostaglandin E₂ (PGE₂) and collagenase. When exposed to a monocyte-derived factor, such cells exhibit marked increases in PGE₂ and collagenase production. In addition, cellular morphology becomes more stellate. In the presence of this factor, indomethacin inhibits both PGE₂ production and the stellate changes, whereas collagenase production usually continues at a high rate. Addition of PGE₂ to cultures reproduces the stellate change as does the cyclic adenosine monophosphate (cAMP) analog 8-bromo-cAMP. Colchicine inhibits morphologic transformation induced by the monocyte-derived factor, whereas cytochalasin B has no effect. It appears that the stellate morphology is dependent upon PGE₂-induced cAMP stimulation and is not related to collagenase production per se.