Abstract
The evaluation of drug pharmacokinetics in the small intestine is critical for developing orally administered drugs. Caucasian colon adenocarcinoma (Caco-2) cells are employed to evaluate drug absorption in preclinical trials of drug development. However, the pharmacokinetic characteristics of Caco-2 cells are different from those of the normal human small intestine. Besides this, it is almost impossible to obtain primary human intestinal epithelial cells of the same batch. Therefore, human iPS cell-derived enterocytes (hiPSEs) with pharmacokinetic functions similar to human intestinal epithelial cells are expected to be useful for the evaluation of drug absorption. Previous studies have been limited to the use of cytokines and small molecules to generate hiPSEs. Dietary fibers play a critical role in maintaining intestinal physiology. We used gellan gum (GG), a soluble dietary fiber, to optimize hiPSE differentiation. hiPSEs cocultured with GG had significantly higher expression of small intestine- and pharmacokinetics-related genes and proteins. The activities of drug-metabolizing enzymes, such as cytochrome P450 2C19, and peptide transporter 1 were significantly increased in the GG treatment group compared to the control group. At the end point of differentiation, the percentage of senescent cells increased. Therefore, GG could improve the differentiation efficiency of human iPS cells to enterocytes and increase intestinal maturation by extending the life span of hiPSEs.
Highlights
During drug discovery and development, many candidate drugs fail to enter clinical trials despite the fact that a large amount of money and time has been spent [1,2]
To evaluate the optimal concentration of dietary fiber required for differentiation, we preliminarily investigated the effects of several dietary fibers, including crystalline cellulose (0.015%), chitin powder (0.015%), bamboo pulp (0.015%), and gellan gum (GG) (0.015%), on differentiation (Figure 1)
The expression levels of small intestinal-specific markers, including villin 1 [23,24], intestine specific homeobox (ISX) [25], fatty acid-binding protein 2 (FABP2) [26], dipeptidyl peptidase-4 (DPP4) [27], and caudal-type homeobox 2 (CDX2) [25,28], and the tight junction marker occludin were significantly increased in the presence of GG (Figure 2a)
Summary
During drug discovery and development, many candidate drugs fail to enter clinical trials despite the fact that a large amount of money and time has been spent [1,2]. In preclinical trials of drug development, Caucasian colon adenocarcinoma (Caco-2) cells and intestinal microsomes are used to evaluate intestinal drug absorption and metabolism, respectively [6,7]. These systems have some disadvantages, possibly leading to drug development failures. The expression patterns of drug transporters in Caco-2 cells are different from those in the normal human small intestine [8,9,10]. It is almost impossible to obtain primary human intestinal epithelial cells of the same batch for pharmacokinetic studies [11]. Microsomes can only evaluate drug metabolism by the enzymes existing in the fraction
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