Early morphological changes of porcine serum-induced hepatic fibrosis.

When porcine serum is used to induce hepatic fibrosis in rats, linear septal fibrosis develops and outlines the periphery of Rappaport's functional liver acinus. A sequential morphological study was done to clarify the histogenesis of this hepatic fibrosis, especially in the early stages. Under light microscopic examination, the fibrotic septa developed as a thin fibrotic strand connecting terminal hepatic veins without any massive necrosis. Electron microscopic examination, however, revealed a thickening of the walls of the portal veins with narrowing lumen and damage to hepatocytes prior to the development of fibrosis. There was only mild inflammation and examination showed three types of mesenchymal cells; Ito cells, myofibroblasts, and fibroblasts. These changes suggested that this fibrosis is a result of hepatic damage, which in turn was possibly caused by disturbance of the portal vein.