Spontaneous aortic aneurysms in blotchy mice.

The pathogenesis of aneurysm formation was studied in Blotchy (Blo) mice which have a hereditary defect in collagen and elastin cross-linking. Elastin breakdown began at an early age and progressed rapidly. Changes observed included replacement of elastica by fibroblasts and ground substance. More advanced lesions were characterized by infiltrates of inflammatory cells, hemorrhages, and eventual ruptures of the aortic wall. Accumulations of lipids, Schiff-positive mucopolysaccharides, iron or calcium were not found. The lesions occurred primarily at points of greatest stress and were confined to the thoracic aorta. Androgen-insensitive mice (Tfm/Y) with the Blo gene died at a significantly earlier age than did normal Blo males or Blo/plus females. The Blo mouse is compared with other animal models of spontaneous and experimentally produced aneurysms.