Cathepsin K gene disruption does not affect murine aneurysm formation

Contrary to our expectations, catK deficiency did not protect against aneurysm formation, nor did it affect medial elastin breaks. Proteolytic activity in abdominal aortic lysates were comparable between apoE−/− and catK−//−apoE−/− mice. Adventitial presence of catS- and catC-expressing cells was significantly increased in catK−/−//apoE−/− versus apoE−/− mice, which might have compensated for the deficiency of catK-derived proteolysis in the aneurysm tissue of catK deficient apoE−/− mice. Circulating granulocytes and activated T cell numbers were significantly increased in Ang II-infused catK−/−//apoE−/− mice, which is consistent with the borderline significant increase in adventitial leukocyte content in catK−/−//apoE−/− compared to apoE−/− mice. Strikingly, despite unchanged proteolytic activity in AAA lesions, collagen content in the aneurysm was significantly increased in catK−//−apoE−/− mice. In conclusion, while catK deficiency has major impact on various vasculopathies, it did not affect murine aneurysm formation.