Different expression of positive and negative regulators of hepatocyte growth in growing and shrinking hepatic lobes after portal vein branch ligation in rats.

Portal vein branch embolization is often performed before hepatectomy to prevent postoperative liver failure. It is, however, still not clear how the embolized lobe shrinks and the non-embolized lobe proliferates in counterbalance. We investigated the expression of positive and negative regulators of hepatocyte growth to clarify the mechanisms of liver growth and atrophy in a rat portal vein ligation (PVL) model compared with partial hepatectomy (PH). A significant increase in DNA synthesis within the non-ligated lobe reached a peak at 36 h, a delay of 12 h as compared with PH, while no increase occurred in the ligated lobe. Expression of hepatocyte growth factor mRNA remarkably increased in the non-ligated growing lobe between 6 and 24 h, but was only slightly elevated in the ligated shrinking lobe. Contrarily, negative regulators of hepatocyte proliferation, such as TGF-beta1 and IL-1beta, were strongly expressed in the ligated shrinking lobe. Thus, the changes of portal venous flow and/or pressure caused by PVL may contribute to induction of different kinds of growth factors between the ischemic and non-ischemic lobes; these factors possibly regulate liver regeneration and atrophy after PVL.