Establishment of MDR1-knockout human enteroids for pharmaceutical application

Effect of knocking out mouse Slc44a4 on colonic uptake of the microbiota-generated thiamine pyrophosphate and colon physiology

Humans and mammals obtain vitamin B1 from dietary and gut microbiota sources. A considerable amount of the microbiota-generated vitamin exists in the form of thiamine pyrophosphate (TPP), and colonocytes are capable of absorbing TPP via a specific carrier-mediated process that involves the colonic TPP transporter (cTPPT encoded by SLC44A4). Little is known about the relative contribution of the SLC44A4 transporter toward total colonic carrier-mediated TPP uptake and its role in colon physiology. To address these issues, we generated an Slc44a4 knockout (KO) mouse model (by Cre-Lox recombination) and found a near-complete inhibition in colonic carrier-mediated [3H]TPP uptake in the Slc44a4 KO compared with wild-type (WT) littermates. We also observed a significant reduction in KO mice's body weight and a shortening of their colon compared with WT. Using RNAseq and Ingenuity pathway analysis (IPA) approaches, we found that knocking out the colonic Slc44a4 led to changes in the level of expression of many genes, including upregulation in those associated with intestinal inflammation and colitis. Finally, we found that the Slc44a4 KO mice were more susceptible to the effect of the colitogenic dextran sodium sulfate (DSS) compared with WT animals, a finding that lends support to the recent prediction by multiple genome-wide association studies (GWAS) that SLC44A4 is a possible colitis susceptibility gene. In summary, the results of these investigations show that Slc44a4 is the predominant or only transporter involved in the colonic uptake of TPP, that the transporter is important for colon physiology, and that its deletion increases susceptibility to inflammation.NEW & NOTEWORTHY This study shows that Slc44a4 is the predominant or only transport system involved in the uptake of the gut microbiota-generated thiamine pyrophosphate (TPP) in the colon and that its deletion affects colon physiology and increases its susceptibility to inflammation.

The roles of ABCB1/P-glycoprotein drug transporters in regulating gut microbes and inflammation: insights from animal models, old and new

Commensal enteric bacteria have evolved systems that enable growth in the ecologic niche of the host gastrointestinal tract. Animals evolved parallel mechanisms to survive the constant exposure to bacteria and their metabolic by-products. We propose that drug transporters encompass a crucial system to managing the gut microbiome. Drug transporters are present in the apical surface of gut epithelia. They detoxify cells from small molecules and toxins (xenobiotics) in the lumen. Here, we review what is known about commensal structure in the absence of the transporter ABCB1/P-glycoprotein in mammalian models. Knockout or low-activity alleles of ABCB1 lead to dysbiosis, Crohn's disease and ulcerative colitis in mammals. However, the exact function of ABCB1 in these contexts remain unclear. We highlight emerging models-the zebrafish Danio rerio and sea urchin Lytechinus pictus-that are poised to help dissect the fundamental mechanisms of ATP-binding cassette (ABC) transporters in the tolerance of commensal and pathogenic communities in the gut. We and others hypothesize that ABCB1 plays a direct role in exporting inflammatory bacterial products from host epithelia. Interdisciplinary work in this research area will lend novel insight to the transporter-mediated pathways that impact microbiome community structure and accelerate the pathogenesis of inflammatory bowel disease when perturbed. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Functional intestinal monolayers from organoids derived from human iPS cells for drug discovery research

BACKGROUND

Human induced pluripotent stem (iPS) cell-derived enterocyte-like cells (ELCs) are expected to be useful for evaluating the intestinal absorption and metabolism of orally administered drugs. However, it is difficult to generate large amounts of ELCs with high quality because they cannot proliferate and be passaged.

METHODS

To solve the issue above, we have established intestinal organoids from ELCs generated using our protocol. Furthermore, monolayers were produced from the organoids. We evaluated the usefulness of the monolayers by comparing their functions with those of the original ELCs and the organoids.

RESULTS

We established organoids from ELCs (ELC-org) that could be passaged and maintained for more than a year. When ELC-org were dissociated into single cells and seeded on cell culture inserts (ELC-org-mono), they formed a tight monolayer in 3 days. Both ELC-org and ELC-org-mono were composed exclusively of epithelial cells. Gene expressions of many drug-metabolizing enzymes and drug transporters in ELC-org-mono were enhanced, as compared with those in ELC-org, to a level comparable to those in adult human small intestine. The CYP3A4 activity level in ELC-org-mono was comparable or higher than that in primary cryopreserved human small intestinal cells. ELC-org-mono had the efflux activities of P-gp and BCRP. Importantly, ELC-org-mono maintained high intestinal functions without any negative effects even after long-term culture (for more than a year) or cryopreservation. RNA-seq analysis showed that ELC-org-mono were more mature as intestinal epithelial cells than ELCs or ELC-org.

CONCLUSIONS

We have successfully improved the function and convenience of ELCs by utilizing organoid technology.

Establishment of human intestinal organoids derived from commercially available cryopreserved intestinal epithelium and evaluation for pharmacokinetic study

Human intestinal organoids (HIOs) have been reported to exert their functions in a way that mimics living organs, and HIOs-derived monolayers are expected to be applied to in vitro intestinal pharmacokinetic studies. However, HIOs are established from human tissue, which raises issues of availability and ethics. In the present study, to solve these problems, we have established intestinal organoids using commercially available cryopreserved human intestinal epithelial cells (C-IOs), and compared their functions with biopsy-derived human intestinal organoids (B-IOs) from a pharmacokinetic point of view. Both C-IOs and B-IOs reproduced the morphological features of the intestinal tract and were shown to be composed of epithelial cells. Monolayers generated from C-IOs and B-IOs (C-IO-2D, B-IO-2D, respectively) structurally mimic the small intestine. The C-IOs showed gene expression levels comparable to those of the B-IOs, which were close to those of adult human small intestine. Importantly, the C-IOs-2D showed levels of pharmacokinetics-related protein expression and activity-including cytochrome P450 3A4 (CYP3A4) and carboxylesterase 2 (CES2) enzymatic activities and P-glycoprotein (P-gp) transporter activities -similar to those of B-IOs-2D. This study addresses the difficulties associated with B-IOs and provides fundamental characteristics for the application of C-IOs in pharmacokinetic studies.

Recent Advances in the Gastrointestinal Complex in Vitro Model for ADME Studies

Intestinal absorption is a complex process involving the permeability of the epithelial barrier, efflux transporter activity, and intestinal metabolism. Identifying the key factors that govern intestinal absorption for each investigational drug is crucial. To assess and predict intestinal absorption in humans, it is necessary to leverage appropriate in vitro systems. Traditionally, Caco-2 monolayer systems and intestinal Ussing chamber studies have been considered the 'gold standard' for studying intestinal absorption. However, these methods have limitations that hinder their universal use in drug discovery and development. Recently, there has been an increasing number of reports on complex in vitro models (CIVMs) using human intestinal organoids derived from intestinal tissue specimens or iPSC-derived enterocytes plated on 2D or 3D in microphysiological systems. These CIVMs provide a more physiologically relevant representation of key ADME-related proteins compared to conventional in vitro methods. They hold great promise for use in drug discovery and development due to their ability to replicate the expressions and functions of these proteins. This review highlights recent advances in gut CIVMs employing intestinal organoid model systems compared to conventional methods. It is important to note that each CIVM should be tailored to the investigational drug properties and research questions at hand.

Quantitative Prediction of Intestinal Absorption of Drugs from In Vitro Study: Utilization of Differentiated Intestinal Epithelial Cells Derived from Intestinal Stem Cells at Crypts

Prediction of intestinal absorption of drugs in humans is one of the critical elements in the development process for oral drugs. However, it remains challenging, because intestinal absorption of drugs is influenced by multiple factors, including the function of various metabolic enzymes and transporters, and large species differences in drug bioavailability hinder the prediction of human bioavailability directly from in vivo animal experiments. For the screening of intestinal absorption properties of drugs, a transcellular transport assay with Caco-2 cells is still routinely used by pharmaceutical companies because of its convenience, but the predictability of the fraction of the oral dose that goes to the portal vein of metabolic enzyme/transporter substrate drugs was not always good because the cellular expression of metabolic enzymes and transporters is different from that in the human intestine. Recently, various novel in vitro experimental systems have been proposed such as the use of human-derived intestinal samples, transcellular transport assay with induced pluripotent stem-derived enterocyte-like cells, or differentiated intestinal epithelial cells derived from intestinal stem cells at crypts. Crypt-derived differentiated epithelial cells have an excellent potential to characterize species differences and regional differences in intestinal absorption of drugs because a unified protocol can be used for the proliferation of intestinal stem cells and their differentiation into intestinal absorptive epithelial cells regardless of the animal species and the gene expression pattern of differentiated cells is maintained at the site of original crypts. The advantages and disadvantages of novel in vitro experimental systems for characterizing intestinal absorption of drugs are also discussed. SIGNIFICANCE STATEMENT: Among novel in vitro tools for the prediction of human intestinal absorption of drugs, crypt-derived differentiated epithelial cells have many advantages. Cultured intestinal stem cells are rapidly proliferated and easily differentiated into intestinal absorptive epithelial cells simply by changing the culture media. A unified protocol can be used for the establishment of intestinal stem cell culture from preclinical species and humans. Region-specific gene expression at the collection site of crypts can be reproduced in differentiated cells.