ANTIFIBROTIC ACTION OF INTERLEUKIN-1 RECEPTOR ANTAGONIST IN LAPINE MONOARTICULAR ARTHRITIS

Objective-To determine if the administration of interleukin-1 receptor antagonist (IL-1ra) to animals with established antigen induced arthr itis had any beneficial effects on the synovitis and cartilage destruc tion. Methods-Antigen induced arthritis was induced in New Zealand Whi te rabbits, and after two weeks IL-1ra was administered every six hour s over a 72 hour period. Animals were then killed and joint tissues ex amined for the degree of synovitis, synovial fibrosis, and cartilage d amage. Results-The response of the arthritis to the treatment was mino r in terms of joint swelling, leucocyte accumulation, or cartilage pro teoglycan loss. However, the synovial fibrosis was not only halted by administration of IL-1ra, but reversed. The inflamed synovial linings of IL-1ra treated animals showed a significant loss of synovial collag en content and a reappearance of the synovial fat spaces which are pro minent in the normal synovial lining. Conclusion-This study shows that IL-1ra has potent antifibrotic activity and suggests the use of this agent for the reversal of the fibroproliferative process which is so i mportant in the pathology of rheumatoid arthritis.