Abstract
BackgroundCell culture systems are useful in studying toxicological effects of chemicals such as Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), however little is known as to how accurately isolated cells reflect responses of intact organs. In this work, we compare transcriptional responses in livers of Sprague-Dawley rats and primary hepatocyte cells after exposure to RDX to determine how faithfully the in vitro model system reflects in vivo responses.ResultsExpression patterns were found to be markedly different between liver tissue and primary cell cultures before exposure to RDX. Liver gene expression was enriched in processes important in toxicology such as metabolism of amino acids, lipids, aromatic compounds, and drugs when compared to cells. Transcriptional responses in cells exposed to 7.5, 15, or 30 mg/L RDX for 24 and 48 hours were different from those of livers isolated from rats 24 hours after exposure to 12, 24, or 48 mg/Kg RDX. Most of the differentially expressed genes identified across conditions and treatments could be attributed to differences between cells and tissue. Some similarity was observed in RDX effects on gene expression between tissue and cells, but also significant differences that appear to reflect the state of the cell or tissue examined.ConclusionLiver tissue and primary cells express different suites of genes that suggest they have fundamental differences in their cell physiology. Expression effects related to RDX exposure in cells reflected a fraction of liver responses indicating that care must be taken in extrapolating from primary cells to whole animal organ toxicity effects.
Highlights
Cell culture systems are useful in studying toxicological effects of chemicals such as Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), little is known as to how accurately isolated cells reflect responses of intact organs
We have examined the gene expression responses in primary hepatic cells freshly isolated from liver tissue
Liver tissues were associated with 305 different terms with terms related to amino acid metabolism and catabolism, lipid and fatty acid metabolism, and aromatic and drug metabolism being unique to liver cells. 24 hr cells were associated with 398 different terms with terms related to cell division, organ development, response to DNA damage unique to 24 hr cells
Summary
Cell culture systems are useful in studying toxicological effects of chemicals such as Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), little is known as to how accurately isolated cells reflect responses of intact organs. Primary cell cultures offer several advantages over animals in determining mechanisms of chemical toxicity. Primary hepatocyte cells are freshly prepared from liver tissue by proteolytic digestion and enrichment of hepatocyte cells through centrifugation. These cells enable high throughput testing methods to examine toxicity. The responses to chemical exposure in isolated cells may not reflect those of intact organs in animals especially as organs are often composed of more than one cell type potentially complicating direct comparisons. Conservation of gene expression patterns in hepatocytes isolated from livers have been shown to diverge from liver tissue as the cells adapt to culture conditions [8,9] and may respond to chemicals in a manner different from liver tissue [10]
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