Liver perisinusoidal fibrosis in BB rats with or without overt diabetes

Perisinusoidal fibrosis is a vascular lesion observed in the liver of type I diabetic patients. To investigate whether this liver lesion is secondary to hyperglycemia or whether it represents a separate collagen vascular disorder, the authors studied the structure of liver sinusoids in genetically susceptible BB rats in which a spontaneous diabetes develops similar to human type I diabetes. Seven diabetic insulin-treated BB rats, 7 nondiabetic BB rats, and 6 control non-BB rats were studied. Histologic abnormalities of the collagen network were detected on trichrome-stained sections. Perisinusoidal collagen fibers were quantified ultrastructurally by the point-counting method. All control non-BB rats had normal livers; 86% of the diabetic as well as 71% of the nondiabetic BB rats displayed localized sinusoidal thickening corresponding ultrastructurally to perisinusoidal fibrosis; in these abnormal rats the percentage of collagen fibers per sinusoid unit was significantly higher than that in controls. Fibrous septa (2 diabetic and 5 nondiabetic BB rats) and liver nodulation (3 diabetic and 1 nondiabetic BB rats) were also observed. Perisinusoidal fibrosis is a frequent liver vascular abnormality in a strain of rats genetically predisposed to the development of type I diabetes. The lesion is independent of the presence of diabetes. These observations suggest that liver perisinusoidal fibrosis in patients with type I diabetes might be linked to a genetic abnormality rather than to hyperglycemia per se.