Effects of experimental joint inflammation on bone marrow and periarticular bone. A study of two types of arthritis, using variable degrees of inflammation.

The effects of joint inflammation on bone marrow and periarticular bone were studied in mice using antigen-induced arthritis and zymosan-induced arthritis as models for an immune and a non-immune-mediated chronic inflammation. To allow for a comparison of the two types of arthritis care was taken to induce comparable degrees of inflammation as evaluated with 99mTechnetium uptake and histology. The antigen-induced arthritis caused a significant suppression of the mitotic activity in the bone marrow close to the inflammatory focus during the first days of arthritis. The zymosan-induced arthritis did not produce alterations of the bone marrow activity. Both types of arthritis were able to induce long-lasting and irreversible damage to cartilaginous and bony structures. Apposition of bone was observed in both types of arthritis although much earlier in the antigen-induced arthritis. The apposition of bone was found to emerge largely from the periosteum and not from the epiphyseal plates, as shown by 125I-deoxyuridine autoradiography. Qualitative and quantitative differences suggest that joint inflammation which is immunologically mediated, results in more severe (peri)articular tissue damage than a non-immunological arthritis.