MONOCLONAL EXPANSION OF SYNOVIOCYTES IN RHEUMATOID-ARTHRITIS

Objective. To examine whether synoviocytes from patients with rheumato id arthritis (RA) have a stronger growth ability than those from patie nts with osteoarthritis (OA), and to determine whether these Synoviocy tes clonally expand in situ, Methods. Synovial tissues from 13 RA pati ents and 4 OA patients were cultured, and their ability to form coloni es in soft agarose was examined. RA and OA synoviocytes were also exam ined in varying concentrations of fetal calf serum (FCS)-containing me dium to test the effects of FCS on colony formation. DNA was extracted from clones with colony-forming ability in nonpannus lesions and from synoviocytes in pannus lesions. Restriction fragment length polymorph ism (RFLP) analysis was used to examine phosphoglycerate kinase 1 (PGK -1) gene patterns, Production of cytokines by these cells was also ass essed, Results. All 13 RA synoviocytes exhibited colony formation, whe reas none of the 4 OA synoviocytes did. This tendency was also seen wi th all of the concentrations of FCS examined, although growth varied i h a dose-dependent manner. In contrast to OA synovial clones, cloned R i synoviocytes obtained from colonies exhibited a partial RFLP PGK-I g ene pattern, suggesting that the clones originated from monoclonal cel ls. Of note, 3 of 7 noncloned synoviocytes from pannus lesions exhibit ed a monoclonal pattern. Pannus cells produced high levels of transfor ming growth factor beta and platelet-derived growth factor. Conclusion . These findings suggest that synoviocytes with a strong growth abilit y are present in the rheumatoid synovium, and that these cells expand monoclonally, particularly in pannus lesions.