No abstract

Ischemia-reperfusion injury (IRI) causes up to 10% of early liver failures in humans and can lead to a higher incidence of acute and chronic rejection. So far, very few studies have investigated wide gene expression profiles associated with the IRI process. The discovery of novel genes activated by IRI might lead to the identification of potential target genes for the prevention or treatment of the injury. In our study, we compared gene expression levels in reperfused livers (RL group) vs. the basal values before retrieval from the donor (basal liver [BL] group) using oligonucleotide array technology. We examined 10 biopsies from 5 livers, analyzing approximately 33,000 genes represented on the Affymetrix HG-U133APlus 2.0 oligonucleotide arrays (Affymetrix, Santa Clara, CA). About 13,000 individual genes were considered expressed in at least 1 condition. A total of 795 genes whose expression is significantly modified by ischemia-reperfusion in human liver transplantation were identified in this study. Some of them are likely to be completely activated by IRI, as they are not expressed in basal livers. The supervised gene expression analysis revealed that at least 12% of the genes involved in the apoptotic process, 12.5% of the genes involved in inflammatory processes, and 22.5% of the genes encoding for heat shock proteins are differentially expressed in RL samples vs. BL samples. Furthermore, IRI induces the upregulation of some genes' coding for adhesion molecules and integrins. In conclusion, we have identified a relevant amount of early genes regulated in the human liver after 7-9 hours of cold ischemia and 2 hours from reperfusion, many of them not having been described before in this process. Their analyses may help us to better understand the pathophysiology of IRI and to characterize potential target genes for the prevention or treatment of the liver injury in order to increase the number of patients that successfully undergo transplantation. Liver Transpl 13:99-113, 2007. © Orthotopic liver transplantation has become an effective therapeutic approach for end-stage liver diseases. Advances in surgical procedures and immunosuppression protocols have considerably improved patient survival after liver transplantation. However, ischemiareperfusion injury (IRI), an antigen-independent component of the insult to the liver, represents a major problem affecting the outcome of liver transplantation.IRI causes up to 10% of early liver failures and can lead to a higher incidence of acute and chronic rejection. Liver IRI is mediated by several processes that lead to hepatocellular damage, which is triggered when the Abbreviations: IRI, ischemia-reperfusion injury; HO-1, heme oxygenase-1; BL, basal liver; RL, reperfused liver; GO, Gene Ontology; PCR, polymerase chain reaction; IL, interleukin; CCL, cystein cistein ligand; HSP, heat shock protein.

Ischemia/reperfusion injury and delayed graft function (DGF) following organ transplantation adversely affect graft function and survival. A large animal model has not been characterized. We developed a pig kidney allograft model of DGF and evaluated the cytoprotective effects of inhaled carbon monoxide (CO). We demonstrate that donor warm ischemia time is a critical determinant of DGF as evidenced by a transient (4-6 days) increase in serum creatinine and blood urea nitrogen following transplantation before returning to baseline. CO administered to recipients intraoperatively for 1 h restored kidney function more rapidly versus air-treated controls. CO reduced acute tubular necrosis, apoptosis, tissue factor expression and P-selectin expression and enhanced proliferative repair as measured by phosphorylation of retinol binding protein and histone H3. Gene microarray analyses with confirmatory PCR of biopsy specimens showed that CO blocked proinflammatory gene expression of MCP-1 and heat shock proteins. In vitro in pig renal epithelial cells, CO blocks anoxia-reoxygenation-induced cell death while promoting proliferation. This large animal model of DGF can be utilized for testing therapeutic strategies to reduce or prevent DGF in humans. The efficacy of CO on improving graft function posttransplant validates the model and offers a potentially important therapeutic strategy to improve transplant outcomes.

In this study, we propose the design and fabrication of a liver system on a chip. We first chose the most suitable three‐dimensional liver‐like model between cell spheroids and microtissue precursors, both based on the use of hepatocellular carcinoma cells (HepG2) to provide proof‐of‐concept data. Spheroids displayed high cell density but low expression of the typical hepatic biomarkers, whereas microtissue precursors showed stable viability and function over the entire culture time. The two liver‐like models were compared in terms of cell viability, function, metabolism, and the P‐glycoprotein 1 (P‐gp) transport‐protein expression with the microtissue precursors showing the best performance. Thus, we cultured them into a microfluidic biochip featured with three parallel channels shaped to mimic the hepatic sinusoids. To assess the detoxification potential of the microtissue‐loaded biochip we challenged it with a model molecule (ethanol) at different concentrations and time points. Ethanol cytotoxicity was detected by a noninvasive measurement of cell viability based on cell autofluorescence. As expected, a dose‐dependent decrease of albumin and urea secretion was observed in the ethanol‐treated samples. We believe that the described totally human‐derived platform, suitable for integration into a multiorgan microfluidic system, can provide a consistent innovative platform for drug development and toxicity studies.