Role of interleukin-1 in induction of matrix metalloproteinases synthesized by rat temporomandibular joint chondrocytes and disc cells

To identify cartilage-degrading enzymes and cell types that can be specifically induced by interleukin-l (IL-1)alpha, we studied matrix metalloproteinase (MMP) activities of cultured rat temporomandibular joint (TMJ) chondrocytes and disc cells. The cells were isolated from TMJs pre-injected with normal physiological saline (CR) or recombinant human IL-1 alpha (AR). MMP activities in the conditioned media were assayed by gelatin enzymography, and they were identified by Western blot analyses. MMP mRNAs in these cells were also detected by RT-PCR. IL-1 alpha significantly induced an increase of active MMP9 as well as pro- and active MMP3, but had no effect on the MMP2 activity in both types of cells. MMP3 and MMP9 mRNAs were also inducible in these cells by IL-1 alpha stimulation. Furthermore, disc cells were more susceptible to IL-1 alpha than chondrocytes. AR cells spontaneously produced the same MMPs bz vitro as the CR cells synthesized under IL-1 alpha stimulation. The results indicate that MMP9 and MMP3 were predominantly produced by disc cells, and these may be considered to play a pivotal role in ECM degradation during pathological conditions of the TMJ, such as IL-1-induced TMJ arthritis.