Fibrilization in mouse senile amyloidosis is fibril conformation- dependent

Amyloidosis refers to a group of diseases characterized by tissue deposition of amyloid fibrils. A single intravenous injection of a very small amount of the native mouse senile amyloid fibrils (AApoAII) induced severe systemic amyloid deposition in young mice having the amyloidogenic apoA-II gene (Apoa2 c ). After AApoAII injection, amyloid deposition occurred rapidly and advanced in an accelerated manner, as observed in spontaneous senile amyloidosis in mice. However, the injection of denatured AApoAII, native apoA-II in high-density lipoprotein (HDL), and denatured apoA-II monomer, which have the same primary structure but without a fibril conformation, did not induce amyloidosis. No amyloid deposition was observed in mice having an amyloid-resistant apoA-II gene (Apoa2 b ) even 3 months after AApoAII injection. Significantly less amyloid deposition was observed in mice having both types of apoA-II genes heterozygously (Apoa2 b/c ). These findings suggest that the nucleation-dependent polymerization found in vitro also occurs in vivo, and that the fibril conformation is required for the injected amyloid fibrils to act as seeds in vivo. Fibril conformation-dependent fibrillization is proposed as a general model of the pathogenesis of various kinds of amyloidosis occurring in vivo; it may be useful in both elucidating the pathogenesis of amyloidosis and developing effective therapeutic modalities to treat this disease.