Anti-interleukin-1 and anti-CD44 interventions producing significant inhibition of cartilage destruction in an in vitro model of cartilage invasion by rheumatoid arthritis synovial fibroblasts

Objective. To establish an in vitro model for the investigation of destruct ive processes in rheumatoid arthritis (RA), to study the interaction betwee n fibroblasts, macrophages, and chondrocytes, and to evaluate strategies to inhibit joint destruction in RA. Methods. Human and bovine chondrocytes cultured in sponges pretreated with native bovine embryonic extracellular matrix produced a cartilaginous matri x reflected by the incorporation of S-35 into proteoglycans. The 3-dimensio nal culture system was optimized for the number of chondrocytes (10(5) cell s/ sponge), the timing of 35S incorporation (day 21 after chondrocyte isola tion), and the medium (20% fetal calf serum). RA synovial fibroblasts (RASP ; 10(5)) were added, and the matrix destruction mediated by these RASF was monitored by the release of S-35. The system was modulated by the addition of monocytes (U937 cells), cytokines (interleukin-1 beta [IL-1 beta] and tu mor necrosis factor alpha [TNF alpha]), interleukin-1 receptor antagonist ( IL-1Ra), and monoclonal antibodies against IL-1 beta and CD44. Results. RASF destroyed the bovine cartilaginous matrix within 2 weeks (day s 5-12) and the human cartilaginous matrix within 3 weeks (days 10-18). Com pared with the effect of RASF alone (mean +/- SD 948 +/- 180 counts per min ute/week), the addition of U937 cells (a monocytic cell line), IL-1 beta, o r TNF alpha to the incubation medium increased the destruction of human car tilaginous matrix by at least 71% up to 90% (ranging from 1,618 +/- 204 cpm /week to 1,802 +/- 307 cpm/week). IL-1Ra and anti-IL-1 beta monoclonal anti bodies reduced the destruction of human matrix by 45% and 35%, respectively ; this was partially reversed by the addition of U937 cells. The pretreatme nt of RASF with anti-CD44 monoclonal antibody (an adhesion molecule and rec eptor for hyaluronic acid) inhibited the destruction of the cartilaginous m atrix by an average of 41% over 3 weeks. Conclusion. This model is envisioned to study distinct aspects of human des tructive joint diseases under in vitro conditions and to replace and/or sup plement animal experiments in basic research and drug testing, Based on the fact that proinflammatory cytokines enhance destruction whereas IL-1Ra and antibodies against IL-1 beta and CD44 inhibit the process, it is concluded that;anti-IL-1- and anti-CD44-directed therapies may help prevent cartilag e destruction in RA.