Collagen degradation induced by the combination of IL-1 alpha, and plasminogen in rabbit articular cartilage explant culture

To investigate the effect of plasminogen on cartilage catabolism, we assessed collagen degradation in rabbit articular cartilage explants treated with or without plasminogen and interleukin-1 alpha (IL-1 alpha). The combination of IL-1 alpha and plasminogen induced rapid collagen degradation, amounting to more than 60% of the total collagen by day 7, while neither IL-1 alpha. nor plasminogen alone had any effect, To examine the mechanism of collagen degradation induced by IL-1 alpha and plasminogen, the matrix metalloproteinases (MMPs) in the culture supernatants were examined by ELISA, Western blotting and gelatin zymography, We found that the treatment with IL-1 alpha induced MMP-1, MMP-3, and MMP-9. In addition, plasminogen converted the pro form of MMPs into the active form, Both a tissue inhibitor of metalloproteinases-l (TIMP-1) and a synthetic hydroxamate MMP inhibitor prevented this collagen release, These results suggest that plasminogen causes collagen degradation via activation of MMPs induced by IL-1 alpha.