Immunohistochemical evaluation of hepatic oval cell activation and differentiation toward pancreatic beta-cell phenotype in streptozotocin-induced diabetic mice.

Oval cell (OvCs) involvement in regeneration is a well known phenomenon in models of liver injury, however, the activation of these cells following streptozotocin (STZ)-induced diabetes has not been studied yet. Differentiation of liver cells toward insulin-producing cells in diabetes has been reported, but the cell phenotype is still unclear. The aim of the present study was to confirm by immunohistochemical analysis, the activation of OvCs and their ability to express pancreatic beta-cell phenotype in STZ-induced diabetic mice. Using specific anti-A6 antibodies for mouse OvCs, we found a three-fold increase in periportal number and two-fold higher density of OvCs in diabetic livers, when compared to controls. Unlike non-diabetic controls, double staining technique showed co-localization of A6 and proinsulin in the cytoplasm of OvCs of diabetic animals, but no insulin staining was detected, probably reflecting the premature character of OvCs differentiation toward beta-cell-like phenotype. These data add valuable information concerning the nature and the stage of functional maturity of liver cells undergoing differentiation toward beta-cell phenotype in STZ-induced diabetic animals.