ABSTRACT
The Caco-2 cell model is a valuable tool for studying intestinal biotransformation of xenobiotics and to evaluate the potential of human intestinal absorption of new compounds. These properties were evaluated with Caco-2/TC7 cells in accelerated conditions to reduce maturation lag time from 21-d to 3-d in order to increase time and labor efficiency. Transmission electron and fluorescent microscopy were used for morphological characterization. Alkaline phosphatase and lactate dehydrogenase activities were assessed within time. Cytochrome P450 expression was studied by RT-PCR. Apparent permeabilities of a set of passively absorbed molecules across Caco-2/TC7 cell monolayers were determined to evaluate potential of both systems for prediction of human intestinal absorption. Microscopic images revealed that cells under both conditions differentiated as enterocyte-like cells but did so heterogeneously in the 3-d model. TEER values have shown that the 3-d model is a leakier cell system with higher mannitol Papp (cm/s). Biochemical characterization (hydrolase activities, CYP450 expression) suggested that the 3-d model was at a lower maturation level than the 21-d model. Carrier-mediated uptake of L-Phe was lower in the 3-d model suggesting that this model has limited application for mechanistic studies. Reasonable correlation was obtained between the two models (r2=0.88, p>0.01) for 11 passively absorbed compounds with high potential of rank ordering of compounds. Although results suggested that the 3-d cells are under-differentiated, they could be usable to estimate the oral absorption of passively absorbed compounds.