Endogenous and transplanted small hepatocytes in retrorsine-treated/partially hepatectomized rat liver show differences in growth, phenotype, and proximity to clusters of gamma-glutamyl transpeptidase-positive host hepatocytes

Possible Role of Extracellular Vesicles in Hepatotoxicity of Acetaminophen

We examined proteomic profiles of rat liver extracellular vesicles (EVs) shed following treatment with a sub-toxic dose (500 mg/kg) of the pain reliever drug, acetaminophen (APAP). EVs representing the entire complement of hepatic cells were isolated after perfusion of the intact liver and analyzed with LC-MS/MS. The investigation was focused on revealing the function and cellular origin of identified EVs proteins shed by different parenchymal and non-parenchymal liver cells and their possible role in an early response of this organ to a toxic environment. Comparison of EV proteomic profiles from control and APAP-treated animals revealed significant differences. Alpha-1-macroglobulin and members of the cytochrome P450 superfamily were highly abundant proteins in EVs shed by the normal liver. In contrast, proteins like aminopeptidase N, metalloreductase STEAP4, different surface antigens like CD14 and CD45, and most members of the annexin family were detected only in EVs that were shed by livers of APAP-treated animals. In EVs from treated livers, there was almost a complete disappearance of members of the cytochrome P450 superfamily and a major decrease in other enzymes involved in the detoxification of xenobiotics. Additionally, there were proteins that predominated in non-parenchymal liver cells and in the extracellular matrix, like fibronectin, receptor-type tyrosine-protein phosphatase C, and endothelial type gp91. These differences indicate that even treatment with a sub-toxic concentration of APAP initiates dramatic perturbation in the function of this vital organ.

Changes in the proteome of extracellular vesicles shed by rat liver after subtoxic exposure to acetaminophen

To identify changes in extracellular vesicles (EVs) secreted by the liver following drug-induced liver injury (DILI), rats were treated with a subtoxic dose (500 mg/kg) of the analgesic drug, acetaminophen (APAP). EVs were collected by liver perfusion of sham and APAP-treated rats. Changes in EVs morphology were examined by transmission electron microscopic analysis of negatively stained vesicles. Results from morphometric analysis of EVs revealed striking differences in their size and distribution. Proteome composition of EVs collected by liver perfusion was determined by mass spectrometry using methods of sample preparation that enabled better detection of both highly hydrophobic proteins and proteins with complex post-translational modifications. The collection of EVs after liver perfusion is an approach that enables the isolation of EVs shed not only by isolated hepatocytes, but also by the entire complement of hepatic cells. EVs derived after DILI had a lower content of alpha-1-macroglobulin, ferritin, and members of cytochrome 450 family. Fibronectin, aminopeptidase N, metalloreductase STEAP4, integrin beta, and members of the annexin family were detected only in APAP-treated samples of EVs. These results show that the present approach can provide valuable insights into the response of the liver following drug-induced liver injury.

An Optimal Medium Supplementation Regimen for Initiation of Hepatocyte Differentiation in Human Induced Pluripotent Stem Cells

Human induced pluripotent stem (hiPS) cells are an ideal source for hepatocytes. Glucose and arginine are necessary for cells to survive. Hepatocytes have galactokinase (GALK), which metabolizes galactose for gluconeogenesis, and ornithine transcarbamylase (OTC), which converts ornithine to arginine in the urea cycle. Hepatocyte selection medium (HSM) lacks both glucose and arginine, but contains galactose and ornithine. Although human primary hepatocytes survive in HSM, all the hiPS cells die in 3 days. The aim of this study was to modify HSM so as to initiate hepatocyte differentiation in hiPS cells within 2 days. Hepatocyte differentiation initiating medium (HDI) was prepared by adding oncostatin M (10 ng/ml), hepatocyte functional proliferation inducer (10 nM), 2,2'-methylenebis (1,3-cyclohexanedione) (M50054) (100 μg/ml), 1× non-essential amino acid, 1× sodium pyruvate, nicotinamide (1.2 mg/ml), L-proline (30 ng/ml), and L-glutamine (0.3 mg/ml) to HSM. HiPS cells (201B7 cells) were cultured in HDI for 2 days. RNA was isolated, used as template for cDNA, and subjected to real-time quantitative polymerase chain reaction. Alpha-fetoprotein, γ-glutamyl transpeptidase, and delta-like 1 were upregulated. Expression of albumin was not observed. Expression of transcription factors specific to hepatocytes was upregulated. The expression of GALK2, OTC, and CYP3A4 were increased. In conclusion, differentiation of 201B7 cells to hepatoblast-like cells was initiated in HDI. Limitations were small number of cells were obtained, and the cells with HDI were not mature hepatocytes.