Inducible synthesis of collagenase and other neutral metalloproteinases by cells of aortic origin

In view of the possible link between collagenase and the formation of aortic aneurysms we have determined whether cells within the aorta are able to synthesize this enzyme. Explanted cells obtained from fragments of lapine abdominal aorta secreted little or no collagenase. Two related metalloproteinases, gelatinase and stromelysin, were also produced at very low levels. Treatment with purified human monocyte interleukin-1β, partially purified lapine, synovial IL-1 or phorbol myristate acetate strongly induced the synthesis of all these enzymes. These activators also increased synthesis of prostaglandin E₂. The identity of collagenase was confirmed by detection of the characteristic TC^A and TC^B breakdown fragments of collagen and by demonstration of collagenase mRNA within activated aortic cells. Unactivated aortic cells contained no detectable collagenase mRNA, suggesting a pretranslational level of regulation. Aortic cells thus possess the ability to express several neutral metalloproteinases and, if a sufficient inflammatory stimulus was present, they might do so in arteries undergoing aneurysmal degeneration.