After partial hepatectomy (PH) the remnant liver (RL) presents a regenerative response, always keeping a percent relationship with the host. There are no precise data in the literature about hepatic regeneration of the RL during hypothermal preservation. The objective of the present study is to analyze RL regeneration after PH under conditions of hypothermal preservation with and without laser light simulation. Method: Using Kelley and Maxwell sample size calculation, 112 male Wistar rats will be studied. Fifty-six rats will be divided into four groups of 14 animals each: control-NPTL (non-perfused total liver); PTL (perfused total liver); PHS (70% in situ PH), and PHP (70% PH perfused ex situ). The groups will be compared to 56 rats similarly divided into the same four groups but receiving laser light at 660 nm wavelength and 30 mW power, with an irradiation dose of 22.5 J/cm2. All animals (n = 112) will then be submitted to general anesthesia and operated. The liver will be perfused with 250 ml of Celsior solution with a catheter connected to a 1.30-m high liquid column. Eighteen hours after surgery, hepatic tissue samples will be analyzed for protein expression of Ki67 and PCNA, for the profile of of microRNA expression (miR-21 and miR-16 ) by real time PCR and for mitochondrial function by the polarographic method. Data will be analyzed statistically by the Mann-Whitney test, with the level of significance set at 5%.
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