OBJECTIVE To compare in vitro expression of β1, β3, and β4 integrins in normal fibroblast-like synoviocytes (FBS) and in FBS from rheumatoid arthritis (RA) synovium and to investigate the adhesion of normal FBS and RA-FBS to the integrin binding extracellular matrix (ECM) proteins: collagen type IV, fibronectin, laminin, and tenascin.

RESULTS Compared with normal FBS, RA-FBS showed increased expression of α1 to α6, β1, and β4 integrin subunits and enhanced binding of ECM proteins. Binding to ECM proteins was partly or completely blocked by an anti-β1 integrin antibody and antibodies to α3, α5, and α6 integrin subunits. The blocking efficiency was significantly (P < 0.05) higher in RA-FBS than in normal FBS.

CONCLUSIONS The enhanced expression of the β1 integrin receptors on cultured RA-FBS correlated with increased attachment to ECM proteins. Adhesion of normal and RA-FBS to ECM proteins is mediated through β1 integrin receptors. Therefore, the tight binding of rheumatoid FBS to the matrix via β1 integrins might play a role in ECM remodelling in the rheumatoid process in vivo.