Partial liver resection in rats
This study was designed based on a previous study. In this study, we randomly categorized 120 (age, 9 weeks; male) Sprague–Dawley rats into four groups and subjected them to sham operation, partial liver resection by the ADPJ system, an UA (CUSA→ Excel+; aspiration, 30%; irrigation, 2 mL/min; amplitude, 30; tissue select, standard), and a radio knife (Diatermo MB122K; GIMA, Gessate, Italy; Monopolar COAG mode, 15 V; n = 30/group). The rats were supplied by Kumagai-shigeyasu Co.,Ltd, (sendai, Miyagi, Japan). Thise rats were placed inside each cage in a temperature-controlled room, with food and water provided ad libitum under a 12-h light/dark diurnal cycle. All rats were anesthetized with inhalation of an isoflurane anesthesia apparatus (MK-A110; Muromachi Kikai Co., Ltd., Tokyo, Japan). In the sham group, the rats’ abdomens were opened but immediately closed. In the ADPJ system group, after opening the abdomen, we lifted the left lateral lobe of the liver. Then, the liver capsule was cut with a scalpel, and the liver parenchyma was dissected by the ADPJ system (input voltage, 25 V; water supply, 4 mL/min; pulsed water jet ejection rate, 400 Hz; Fig. 7a). Next, we ligated the preserved fine blood vessels using the ADPJ system by silk thread (Fig. 7b). Notably, the mean weight of the removed liver tissue was 1.47 g. Likewise, in the radio knife and UA groups, we dissected the liver parenchyma using each device. The weight of the removed liver in these groups corroborated that in the ADPJ system group (P = 0.981). All operative procedure times were recorded, and all operations were performed by a single surgeon.
All rats were again anesthetized with isoflurane. At 1, 3, 7, 14, 28, and 56 days after partial liver resection, we humanely euthanized five rats from each group with exsanguination under deep anesthesia in the laboratory, after collecting blood samples and harvested all residual livers (n = 5/group, during each period). In addition, blood was also collected from 5 new 9-week-old rats for comparison. All experiments conducted in this study were approved by the Institutional Review Board at the Center for Laboratory Animal Research, Tohoku University (the approval code: 2017MdA-202).
We assessed liver damage after partial liver resection by aspartate aminotransferase (AST), alanine aminotransferase (ALT), and glutamate dehydrogenase (GLDH) concentrations in the serum. AST and ALT were measured using a clinical analyzer (FUJI DRI-CHEM 7000V; Fuji Film Co., Ltd., Tokyo, Japan), whereas GLDH was measured using an Enzyme-Linked ImmunoSorbent Assay kit (CSB-E13841r; Cusabio Technology LLC, Houston, USA).
All harvested entire livers were immediately immersed in 10% neutral-buffered formalin solution. First, we embedded the livers in paraffin, which were sectioned to 3-mm sections, and examined using hematoxylin–eosin (HE) staining. Next, coagulation necrosis was defined as degeneration, and the maximum depth of degeneration from the resection surface was verticallymeasured. In addition, we counted the number of rats in which denaturation had completely disappeared in the preparations.All preparations were observed with a microscope (AxioCam MRc, Carl Zeiss Microimaging GmbH, Göttingen, Germany) and measured.
In this study, statistical analyses were performed using JMP 13 Pro statistical software (SAS Institute Inc., Cary, NC). All data are presented as mean ± standard deviation. All four groups were compared using one-way analysis of variance. In addition,individual groups were compared using t-test, whereas the number of rats with disappeared denaturation was compared using Fisher’s exact test. P< 0.05 was considered statistically signiﬁcant.