Expression profile of drug absorption related genes in MDCK in vitro model

Cell culture models are utilized in the pharmaceutical industry to screen potential drug candidate compounds for their ability to cross epithelial barriers. In this work the expression levels of genes involved in drug absorption were evaluated in the Madin-Darby Canine Kidney (MDCK) in vitro model. The cells were grown on plastic surfaces (for 3 days) or differentiated on transwell membrane filters (for 3, 5, 7, and 9 days), and the expression of ABC transporters, SLC transporters, and cytochrome P450 (CYP) enzymes was determined using the AffymetrixRTM canine GeneChip RTM. Expression changes during the differentiation process were examined by statistical analysis of the signals of the confirmed probe sets representing transporter and CYP genes. Major differences in expression profile for MDCK cells grown on transwells vs. plastic surfaces were observed. After 3 days of growth, expression of 16% (891 out of 5,554) of the genes was statistically different between the cells grown on plastic and on transwells based on cutoff of 1.5-fold change and false discovery rate of 0 in the two-class unpaired Significance Analysis of Microarray. Proliferation and/or differentiation related genes were enriched among genes whose expression changed the most during the differentiation process. Gene expression stabilized after 5-7 days of growth on transwells. Expression of a small number of genes encoding SLC, ABC, and CYP was detected in MDCK cells, with most of them exhibiting low hybridization signals. Expression of ABCB1 (MDR1), SLC15A1 (PEPT1) and SLC15A2 (PEPT2) genes was confirmed by independent RT-PCR results. When compared to publicly available array data from MDCK cells differentiated on transwells, remarkable similarities of gene expression were observed. This study provides the first systematic evaluation of the expression profiles of genes involved in drug absorption in MDCK cells. The MDCK model can be used for fast permeability prediction in human for passive permeation, and for carrier mediated absorption of particular classes of drug compounds. The study results will also assist the design of drug-transporter and/or drug-enzyme interaction studies based on endogenous gene expression in the cells, and improve understanding of the contributions of various transporters and metabolic enzymes over-expressed in MDCK cells.