Article

Gene expression analysis offers unique advantages to histopathology in liver biopsy evaluations

National Center for Toxicogenomics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
Toxicologic Pathology (Impact Factor: 1.92). 02/2007; 35(2):276-83. DOI: 10.1080/01926230601178207
Source: PubMed

ABSTRACT Liver diseases that induce nonuniform lesions often give rise to greatly varying histopathology results in needle biopsy samples from the same patient. This study examines whether gene expression analysis of such biopsies could provide a more representative picture of the overall condition of the liver. We utilized acetaminophen (APAP) as a model hepatotoxicant that gives a multifocal pattern of necrosis following toxic doses. Rats were treated with a single toxic or subtoxic dose of APAP and sacrificed 6, 24, or 48 hours after exposure. Left liver lobes were harvested, and both gene expression and histopathological analysis were performed on biopsy-sized samples. While histopathological evaluation of such small samples revealed significant sample to sample differences after toxic doses of APAP, gene expression analysis provided a very homogeneous picture and allowed clear distinction between subtoxic and toxic doses. The main biological function differentiating animals that received sub-toxic from those that had received toxic doses was an acute stress response at 6 hours and signs of energy depletion at later time points. Our results suggest that the use of genomic analysis of biopsy samples together with histopathological analysis could provide a more precise representation of the overall condition of a patient's liver than histopathological evaluation alone.

Download full-text

Full-text

Available from: Richard Paules, Aug 11, 2015
0 Followers
 · 
125 Views
  • Source
    • "Heinloth et al. (2007). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The frequent use of rodent hepatic in vitro systems in pharmacological and toxicological investigations challenges extrapolation of in vitro results to the situation in vivo and interspecies extrapolation from rodents to humans. The toxicogenomics approach may aid in evaluating relevance of these model systems for human risk assessment by direct comparison of toxicant-induced gene expression profiles and infers mechanisms between several systems. In the present study, acetaminophen (APAP) was used as a model compound to compare gene expression responses between rat and human using in vitro cellular models, hepatocytes, and between rat in vitro and in vivo. Comparison at the level of modulated biochemical pathways and biological processes rather than at that of individual genes appears preferable as it increases the overlap between various systems. Pathway analysis by T-profiler revealed similar biochemical pathways and biological processes repressed in rat and human hepatocytes in vitro, as well as in rat liver in vitro and in vivo. Repressed pathways comprised energy-consuming biochemical pathways, mitochondrial function, and oxidoreductase activity. The present study is the first that used a toxicogenomics-based parallelogram approach, extrapolating in vitro to in vivo and interspecies, to reveal relevant mechanisms indicative of APAP-induced liver toxicity in humans in vivo.
    Toxicological Sciences 12/2008; 107(2):544-52. DOI:10.1093/toxsci/kfn237 · 4.48 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Preclinical pharmacokinetic (PK) evaluations are typically conducted in rats before in vivo toxicologic evaluations. It is unclear how the serial bleeding procedures in PK studies affect tissue homeostasis or sensitivity to toxicity. In this study, our objective was to evaluate the impact of serial bleeding on the transcriptome of various major tissues (kidney, heart, liver, spleen) and their response to two well-characterized molecules, doxorubicin and cisplatin. Rats received single i.v. injections of saline, doxorubicin (8 mg/kg) or cisplatin (4 mg/kg). In each group, half of the rats were serially bled by tail vein. Serial bleeding was associated with slight decreases of red blood cell parameters, but did not result in histopathological changes or in increased sensitivity to doxorubicin and cisplatin toxicity based on clinical pathology and histopathology evaluation. In addition, serial bleeding did not induce significant gene expression changes in either vehicle- or compound-treated rats when compared to their respective control groups. Overall, these results suggest that the serial bleeding procedure used in PK studies in our institution minimally affects the tissue response to toxicants, and support the use of these studies to generate early toxicology data in drug discovery.
    Toxicology Letters 02/2008; 176(2):138-48. DOI:10.1016/j.toxlet.2007.09.014 · 3.36 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Some of the biochemical events that lead to necrosis of the liver are well-known. However, the pathogenesis of necrosis of the liver from exposure to hepatotoxicants is a complex biological response to the injury. We hypothesize that gene expression profiles can serve as a signature to predict the level of necrosis elicited by acute exposure of rats to a variety of hepatotoxicants and postulate that the expression profiles of the predictor genes in the signature can provide insight to some of the biological processes and molecular pathways that may be involved in the manifestation of necrosis of the rat liver. Rats were treated individually with one of seven known hepatotoxicants and were analyzed for gene expression by microarray. Liver samples were grouped by the level of necrosis exhibited in the tissue. Analysis of significantly differentially expressed genes between adjacent necrosis levels revealed that inflammation follows programmed cell death in response to the agents. Using a Random Forest classifier with feature selection, 21 informative genes were identified which achieved 90%, 80% and 60% prediction accuracies of necrosis against independent test data derived from the livers of rats exposed to acetaminophen, carbon tetrachloride, and allyl alcohol, respectively. Pathway and gene network analyses of the genes in the signature revealed several gene interactions suggestive of apoptosis as a process possibly involved in the manifestation of necrosis of the liver from exposure to the hepatotoxicants. Cytotoxic effects of TNF-alpha, as well as transcriptional regulation by JUN and TP53, and apoptosis-related genes possibly lead to necrosis. The data analysis, gene selection and prediction approaches permitted grouping of the classes of rat liver samples exhibiting necrosis to improve the accuracy of predicting the level of necrosis as a phenotypic end-point observed from the exposure. The strategy, along with pathway analysis and gene network reconstruction, led to the identification of 1) expression profiles of genes as a signature of necrosis and 2) perturbed regulatory processes that exhibited biological relevance to the manifestation of necrosis from exposure of rat livers to the compendium of hepatotoxicants.
    BMC Genomics 07/2008; 9(1):288. DOI:10.1186/1471-2164-9-288 · 4.04 Impact Factor
Show more