The effect of ischemia on the regeneration of the cholestatic liver. An experimental study.

Background/aims: Cholestatic liver is known to be more susceptible to ischemia than normal liver. In this study we assessed the histopathologic features of hepatic ischemic damage and liver regeneration in rats with experimental obstructive jaundice.

Methodology: The study comprised 90 male Wistar rats. These were assigned randomly to 4 groups according to the surgical procedure they underwent: I (n = 10) controls (non-operated), II (n = 10) sham-operated, III (n = 30) occlusion of hepatic artery and portal vein (total liver ischemia), and IV (n = 40) ligation and division of the common bile duct ligation. Rats of group III were sacrificed 15 (IIIa), 30 (IIIb) and 60 min (IIIc) after total liver ischemia was done. Ten days after bile duct ligation, 10 rats of group IV underwent euthanasia, whereas the remaining 30, underwent total liver ischemia and were sacrificed after 15 min (IVb), 30 min (IVc), and 60 min (IVd). Liver wedge biopsies (left anterior lobe) were obtained and histologic examination included hematoxylin and eosin, and immunohistochemical stains for cytokeratin AE1, HEPPAR (hepatocyte paraffin antigen), and antigen Ki67. Immunohistochemical results for Ki67 were expressed following morphometric analysis.

Results: Liver sections from category IVa showed large duct obstruction features, and those from group III, ischemic chages including centrilobular hepatocellular swelling and necrosis, hepatocanalicular cholestasis, and mild portal mononuclear/mixed inflammation. Sections from groups IVB, IVc, IVd displayed together changes of large duct obstruction and ischemia, and in categories IVc (bile duct ligation +30 min total liver ischemia), and IVd (bile duct ligation +60 min total liver ischemia) necrosis of the large bile ducts was present. The total liver parenchymal area affected (% necrosis) was higher in categories IVd, and IVc compared to categories IVb (P < 0.05), and IIIc, IIIb, IIIa (P < 0.01). All 60 total liver ischemia-liver biopsies, developed features of liver regeneration that originated from zone 2, extended to zone 1 and occasionally to zone 3. Immunohistochemical stains revealed cells positive to AE1 and cells positive to HEPPAR. Proliferation rate (% Ki67+ cells) was higher in category IIIa compared to categories IIIb, IIIc, IVb, IVc, and IVd (P < 0.05).

Conclusions: Our study shows that liver ischemia induces more severe hepatocyte damage in livers with obstructive cholangiopathy compared to normal ones. Liver regenerative process is mediated mainly by proliferation of non-necrotic cells that express hepatocellular or ductular epithelial features. Proliferation rate of hepatocytes is lower when liver ischemia and obstructive jaundice coexist.