In mouse senile amyloidosis, apolipoprotein A-ll polymerizes into amyloid fibrils (AApoAll) and deposits systemically. Peripheral injection of AApoAll fibrils into young mice induces systemic amyloidosis (Higuchi et al, 1998). We isolated AApoAll amyloid fibrils from the livers of old R1.P1-Apoa2c mice and injected them with feeding needles into the stomachs of young R1.P1-Apoa2c mice for 5 consecutive days. After 2 months, all mice had AApoAll deposits in the lamina propria of the small intestine. Amyloid deposition extended to the tongue, stomach, heart, and liver at 3 and 4 months after feeding. AApoAll suspended in drinking water also induced amyloidosis. Amyloid deposition was induced in young mice reared in the same cage for 3 months with old mice who had severe amyloidosis. Detection of AApoAll in feces of old mice and induction of amyloidosis by the injection of an amyloid fraction of feces suggested the propagation of amyloidosis by eating feces. Here, we substantiate the transmissibility of AApoAll amyloidosis and present a possible pathogenesis of amyloidosis, ie, oral transmission of amyloid fibril conformation, where we assert that exogenous amyloid fibrils act as templates and change the conformation of endogenous amyloid protein to polymerize into amyloid fibrils.
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