The Potential Role of bcl-2 and Bax Expression, Apoptosis and Cell Proliferation, after Partial Hepatectomy with and without Ischemia, on Cholestatic Livers in Rats: An Experimental Study
AC Tsamandas, J Maroulis, N Siassos, D Karavias. University of Patras Medical School, Patras, Greece
Background: Liver regeneration after partial hepatectomy (PHx) is regulated by several factors that activate or inhibit hepatocyte proliferation. Apoptosis seems to play an important role in cellular proliferation and liver regeneration. Bax and Bcl-2 oncogenes regulate apoptotic process. This study investigates the expression of bcl-2 and bax, and the presence of apoptosis and cell proliferation (Ki67+ cells) after partial hepatectomy with and without ischemia, on cholestatic livers in rats.
Design: Sixty male Wistar rats were randomly divided into four groups (15 rats each): group I: controls, group II: common bile duct ligation (BDL) for 10 days, group III: total liver ischemia (total occlusion of hepatic artery and portal vein-TLI) for 30 minutes, and group IV: BDL for 10 days followed by TLI for 30min. After all procedures (BDL or TLI or both) were completed all 60 rats underwent PHx (68%). All rats were sacrificed 24 and 48 hrs after PHx was completed. Liver tissues were evaluated for a) Bax, Bcl-2 mRNA levels (real time RT-PCR) and distribution (in situ hybridization, b) Bax, Bcl-2 protein levels (Western blot), and distribution (immunohistochemistry), c) cell proliferation (Ki67+ cells-immunohistochemistry) and d) apoptosis (TUNEL method). Results were expressed following image analysis.
Results: Before hepatectomy, bcl-2 and bax levels (protein/mRNA), and apoptotic body index (ABI) were higher in jaundiced rats (groups II and IV) compared to non-jaundiced rats (groups I and III) (p<0.01 in each case). After hepatectomy, there was an early (at 24 hrs) decrease in bcl-2 levels (protein/mRNA), and a late (at 48 hrs) increase of bax levels (protein/mRNA) and of ABI in jaundiced rats (groups II and IV) compared to non-jaundiced rats (groups I and III) (p<0.01 in each case). Proliferation of hepatocytes (Ki67+ hepatocytes) was lower in group V (BDL + TLI), compared to that of groups II (BDL only) implying that superimposed ischemia impairs regeneration that follows PHx in cholestatic livers.
Conclusions: This study shows that hepatocyte apoptosis takes place in cholestatic livers with or without superimposed ischemia. This process may contribute to the impaired regenerative response observed in livers of jaundiced rats after partial hepatectomy.
Category: Liver & Pancreas
Tuesday, March 23, 2010 9:30 AM
Poster Session III # 245, Tuesday Morning