Yu-Na Kang

Ischemic preconditioning and intermittent clamping confer protection against ischemic injury in the cirrhotic mouse liver

Surgery on cirrhotic livers is fraught with complications, and many surgeons refrain from operating on patients with cirrhosis. Surgical procedures include temporal occlusion of blood flow resulting in ischemia. The mechanisms of protective strategies to prevent ischemic injury in patients with cirrhosis are not fully understood. The aim of this study was to evaluate how the cirrhotic liver tolerates an ischemic insult, whether mechanisms other than those observed in the normal liver are active, and whether intermittent clamping and preconditioning, which are known as safe surgical strategies in normal and steatotic livers, confer protection to the cirrhotic liver. We applied partial hepatic inflow occlusion to cirrhotic mice fed carbon tetrachloride according to different vascular occlusion protocols: intermittent clamping with 15 or 30 minute cycles of ischemia or ischemic preconditioning prior to 60 or 75 minutes of ischemia. Continuous ischemia (60 or 75 minutes) served as controls. The results showed that the cirrhotic liver was significantly more susceptible to 60 minutes of ischemia than the normal liver. Apoptosis was higher in the normal liver, whereas necrosis was a predominant feature in the cirrhotic liver. Both protocols of intermittent vascular occlusion and ischemic preconditioning dramatically prevented injury compared to continuous occlusion for 60 minutes. This protection was associated with reduced necrosis and apoptosis, and particularly reduced activation of the apoptotic pathway through mitochondria. In conclusion, this study extends the protective effects of ischemic preconditioning and intermittent clamping to the cirrhotic liver, highlighting a diminished apoptotic pathway with dramatic improvement in the development of necrosis. Liver Transpl 14:980–988, 2008.

Reevaluation of Experimental Model of Hepatic Fibrosis Induced by Hepatotoxic Drugs: An Easy, Applicable, and Reproducible Model

Establishing an easy and reproducible model for hepatic fibrosis is absolutely necessary for research on liver reperfusion injury. We compared the characteristics of several hepatic cirrhosis models in terms of the degree of fibrosis, reproducibility, histologic characteristics, and success rate to achieve sufficient fibrosis. In mice & rats, we administered three different hepatotoxic drugs (thioacetamide, dimethylnitrosamine, and carbon tetrachloride [CCl4]) through two different routes (oral feeding and intraperitoneal injection). The animals fed thioacetamide exhibited little fibrosis; rather, more inflammatory cells infiltrated into periportal areas with bile duct proliferation. The livers from hosts administered dimethylnitrosamine showed greater early injury and severe inflammatory reactions in the peritoneal cavity. The liver showed a marked degree of piecemeal necrosis with limited fibrosis. The mice administered a 50% solution of CCl4 (2 mL/kg orally) tolerated the entire induction period of 12 weeks. The degree of fibrosis correlated well with the duration of induction. Livers from hosts administered CCl4 orally twice a week for 10 weeks was the most effective to achieve sufficient fibrosis and greatest reproducibility with acceptable animal survival.

Optimal cycle of intermittent portal triad clamping during liver resection in the murine liver

We designed this experimental study to determine the optimal cycle for intermittent inflow occlusion during liver resection. A cycle of intermittent clamping (IC) for 15 minutes of ischemia followed by reperfusion for 5 minutes during liver resection is currently the most popular protocol used by experienced liver centers. As each period of reperfusion is associated with bleeding, longer periods of clamping would be advantageous. However, the longest safe duration of successive ischemia is unknown. Three groups of mice were subjected to a total liver ischemic period for 90 minutes; 2 groups underwent IC for 15 or 30 minutes, respectively, followed by 5 minutes of reperfusion, while the control group was subjected to continuous inflow occlusion only. The degree of tissue injury was assessed using biochemical and histological markers, as well as animal survival. While serious injury was observed in the continuous clamping group, both IC groups were associated with minimal injury, including lesser degrees of apoptosis and necrosis. All animals survived in the IC groups, while all animals died following 90 minutes of continuous inflow occlusion. In conclusion, intermittent portal pedicle clamping with 15‐ or 30‐minute cycles is highly protective. A period of 30 minutes clamping should be preferred, since this would decrease the amount of blood loss associated with each cycle. This data should be confirmed in humans, and may represent a change in the current practice of hepatic surgery. (Liver Transpl 2004;10:794–801.)

Inhibitory Effect of Nuclear Factor-κB Decoy Oligodeoxynucleotide on Liver Fibrosis Through Regulation of the Epithelial–Mesenchymal Transition

The epithelial-mesenchymal transition (EMT) has been recognized to occur during embryonic development, fibrosis, and tumor metastasis. Nuclear factor (NF)-κB plays a central role in mediating the inflammation and wound-healing responses during liver fibrogenesis. However, the involvement of NF-κB during EMT in liver cells remains unidentified. To develop a therapeutic approach to EMT during liver fibrosis, we examined the inhibition of transcription factor NF-κB, using a decoy oligodeoxynucleotide (ODN) strategy in liver fibrosis in vitro and in vivo. NF-κB decoy ODN contains consensus binding sequences of the NF-κB-binding site. NF-κB decoy ODN effectively suppresses transforming growth factor-β(1)-induced EMT in AML12 murine hepatocytes. Liver fibrosis induced by CCl(4) administration was suppressed by NF-κB decoy ODN. Furthermore, NF-κB decoy ODN was shown to inhibit the EMT process in fibrotic liver in vivo. This study demonstrates the feasibility of NF-κB decoy ODN treatment for preventing liver fibrosis via EMT processes.

The Inhibitory Effect of siRNAs on The High Glucose-Induced Overexpression of TGF-β1 in Mesangial Cells

Diabetic nephropathy is characterized by an expansion of the glomerular mesangium, caused by mesangial cell proliferation and an excessive accumulation of extracellar matrix (ECM) proteins, which eventually leading to glomerulosclerosis. TGF-β1 was found to play an important role in the accumulation of ECM in the kidney. In this study, TGF-β1 RNA interference was used as an effective therapeutic strategy. The inhibitory effect of TGF-β1 small interfering RNAs (siRNAs) on the high glucose-induced overexpression of TGF-β1 in rat mesangial ceys (RMCs). A high levels of glucose induces TGF-β1 mRNA and protein, and TGF-β1 siRNAs reduce the ability of high glucose to stimulate their expression. We also examined the inhibitory effect of TGF-β1 siRNAs on the expression of plasminogen activator inhibitor (PAI)-1 and Collagen Type I which are down-regulators of TGF-β1. The expression of TGF-β1, PAI-1 and Collagen Type I was increased in RMCs that were stimulated by 30 mM glucose. TGF-β1 siRNAs reduces high glucose-induced TGF-β1, PAI-1, and Collagen Type I mRNA and protein expression in a dose-dependent manner. In conclusion, the present study demonstrates that TGF-β1 siRNAs effectively inhibits TGF-β1 mRNA and protein expression in RMCs. These suggest that TGF-β1 siRNAs through RNAi may be a useful tool for developing new therapeutic applications for the treatment of diabetic nephropathy.

Nonsurgical Treatment of Gastric Perforation Complicated By Endoscopic Mucosal Resection and Endoscopic Submucosal Dissection

Background/Aims: Endoscopic Mucosal Resection (EMR) and Endoscopic Submucosal Dissection (ESD) are novel techniques used for the treatment of early gastric cancer and precancerous lesions of the stomach. However, complications such as bleeding and perforation may occur during the procedure, and these complications may raise the morbidity and mortality rates. EMR/ESD-induced perforations can be treated with conservative medical or non-surgical methods. Furthermore, an increasing number of reports have addressed conservative management of EMR/ESD-induced perforations. We evaluated the effectiveness and safety of implementing conservative treatment for perforations associated with EMR and ESD. Methods: We reviewed 482 patients with 507 lesions who underwent EMR or ESD due to early gastric cancers or gastric adenomas between February 2003 and December 2007. We identified 14 perforations occurring as complications of EMR/ESD and investigated their clinical outcomes. Results: Fourteen perforations (14/507 [2.8%]) occurred, 11 of which were immediately clipped during the procedure, and 3 of which were diagnosed after the procedure when free air was visualized on the radiograph. All patients were managed conservatively with fluid resuscitation and antibiotics (mean, 5.8 days). They recovered without surgery and were discharged in stable condition at a mean of 7.2 days post-procedure. Conclusions: Endoscopic clip application might be an effective and safe option for conservative management of EMR/ESD-induced perforations. (Korean J Gastrointest Endosc 2008;37:97-104)