Okechukwu Ukairo
Hepregen Corporation, USA
Title: Exploring chronic drug dosing in engineered human liver cultures using global expression profiling
Biography
Biography: Okechukwu Ukairo
Abstract
Global gene expression changes can provide insights into the mechanism of action of drug candidates. Furthermore, signatures of gene expression may distinguish compounds with potential to cause overt toxicity from non-toxic compounds. Primary human hepatocytes are widely considered to be the most suitable to assess drug-induced gene expression changes in vitro, as they contain the full repertoire of regulatory pathways; however, hepatocytes display a precipitous decline in phenotypic functions when left in suspension or cultured in a sandwich of extracellular matrix proteins. Therefore, conventional systems are generally unsuitable for assessment of gene expression changes upon chronic exposure of clinically relevant dosing regimens. We have previously developed microscale models of the human liver, or micropatterned co-cultures (MPCCs), in which primary human hepatocytes are organized in colonies of empirically optimized dimensions and subsequently surrounded by supportive stromal cells. Here, we sought to discern the effects of acute (24 hours) and chronic (7 to 14 days) drug exposure on the transcriptome of primary human hepatocytes using the hepatotoxic and non-toxic structural analogs, troglitazone and rosiglitazone, respectively. MPCCs were chronically exposed to a sub-lethal, clinically relevant Cmax dose. Messenger RNA was collected and hybridized to whole genome human Affymetrix GeneChips. Subsequent analysis of gene expression data revealed a time-dependent increase in gene expression changes induced by both troglitazone and rosiglitazone as compared to vehicle controls. In particular, troglitazone caused up-regulation of several genes involved in cellular pathways such as oxidation-reduction, lipid metabolism and biosynthesis, and stress/wounding response. Moreover, when the dosing concentration of rosiglitazone was increased to that of troglitazone, a significant number of genes were identified as differentially expressed in response to both compounds. In the future, MPCCs may be utilized with both gene expression and biochemical assays to select optimal drug candidates in both drug discovery and development.