Arthritis News - 1999
One of
the cardinal features of RA is erosion of periarticular bone. Osteoclasts
play a key role in bone resorption but the mechanisms by which osteoclasts
are formed from progenitor cells is not fully understood. In this study,
Kotake, etal (J Clin Invest 103:1345, 1999) observed that Interleukin 17
(IL-17), a newly discovered cytokine, could induce the formation of osteoclast-like
cells in cocultures of mouse hemopoietic cells and primary osteoblasts.
This IL-17 induced osteoclastogenesis was inhibited by indomethacin, a selective
inhibitor of cyclooxygenas-2 (COX-2). The synovial fluids from rheumatoid
arthritis patients were found to have significantly higher levels of IL-17
as compared to osteoarthritis patients. Furthermore, using immunostaining,
IL-17-positive mononuclear cells were detected in the synovial tissues of
RA patients and not in tissue from OA patients. These findings indicate
that IL-17 may contribute to bone erosion and joint damage in RA and may
therefore, be another target for inhibition.