Establishment of a novel culture method for maintaining intestinal stem cells derived from human induced pluripotent stem cells

Air-liquid interface culture combined with differentiation factors reproducing intestinal cell structure formation in vitro

Reproducing intestinal cells in vitro is important in pharmaceutical research and drug development. Caco-2 cells and human iPS cell-derived intestinal epithelial cells are widely used, but few evaluation systems can mimic the complex crypt-villus-like structure. We attempted to generate intestinal cells mimicking the three-dimensional structure from human iPS cells. After inducing the differentiation of iPS cells into intestinal organoids, these were dispersed into single cells and cultured two-dimensionally. An air-liquid interface culture was used, with CHIR99021, forskolin, and A-83-01 used as key compounds. Long-term culture was also performed by adding Wnt3a, Noggin, and RSPO1, which are frequently used in organoid culture. The air-liquid interface culture combined several compounds that successfully induced the formation of a crypt-villus-like structure, which grew rapidly at around day 6. The expression of pharmacokinetic genes such as CYP3A4 was also enhanced. The intestinal stem cells were efficiently maintained by the addition of Wnt3a, Noggin, and RSPO1. We were able to construct a crypt-villus-like structure on cell culture inserts, which is considered a very simple culture platform. This structure had characteristics extremely similar to living intestinal tissues and may have a superior homeostatic mechanism.

PSC-derived intestinal organoids with apical-out orientation as a tool to study nutrient uptake, drug absorption and metabolism

Intestinal organoids recapitulate many features of the in vivo gastrointestinal tract and have revolutionized in vitro studies of intestinal function and disease. However, the restricted accessibility of the apical surface of the organoids facing the central lumen (apical-in) limits studies related to nutrient uptake and drug absorption and metabolism. Here, we demonstrate that pluripotent stem cell (PSC)-derived intestinal organoids with reversed epithelial polarity (apical-out) can successfully recapitulate tissue-specific functions. In particular, these apical-out organoids show strong epithelial barrier formation with all the major junctional complexes, nutrient transport and active lipid metabolism. Furthermore, the organoids express drug-metabolizing enzymes and relevant apical and basolateral transporters. The scalable and robust generation of functional, apical-out intestinal organoids lays the foundation for a completely new range of organoid-based high-throughput/high-content in vitro applications in the fields of nutrition, metabolism and drug discovery.

Implementing organ-on-chip in a next-generation risk assessment of chemicals: a review

Organ-on-chip (OoC) technology is full of engineering and biological challenges, but it has the potential to revolutionize the Next-Generation Risk Assessment of novel ingredients for consumer products and chemicals. A successful incorporation of OoC technology into the Next-Generation Risk Assessment toolbox depends on the robustness of the microfluidic devices and the organ tissue models used. Recent advances in standardized device manufacturing, organ tissue cultivation and growth protocols offer the ability to bridge the gaps towards the implementation of organ-on-chip technology. Next-Generation Risk Assessment is an exposure-led and hypothesis-driven tiered approach to risk assessment using detailed human exposure information and the application of appropriate new (non-animal) toxicological testing approaches. Organ-on-chip presents a promising in vitro approach by combining human cell culturing with dynamic microfluidics to improve physiological emulation. Here, we critically review commercial organ-on-chip devices, as well as recent tissue culture model studies of the skin, intestinal barrier and liver as the main metabolic organ to be used on-chip for Next-Generation Risk Assessment. Finally, microfluidically linked tissue combinations such as skin-liver and intestine-liver in organ-on-chip devices are reviewed as they form a relevant aspect for advancing toxicokinetic and toxicodynamic studies. We point to recent achievements and challenges to overcome, to advance non-animal, human-relevant safety studies.

Toward Xeno-Free Differentiation of Human Induced Pluripotent Stem Cell-Derived Small Intestinal Epithelial Cells

The small intestinal epithelium has an important role in nutrition, but also in drug absorption and metabolism. There are a few two-dimensional (2D) patient-derived induced pluripotent stem cell (iPSC)-based intestinal models enabling easy evaluation of transcellular transport. It is known that animal-derived components induce variation in the experimental outcomes. Therefore, we aimed to refine the differentiation protocol by using animal-free components. More specifically, we compared maturation of 2D-cultured iPCSs toward small intestinal epithelial cells when cultured either with or without serum, and either on Geltrex or on animal-free, recombinant laminin-based substrata. Differentiation status was characterized by qPCR, immunofluorescence imaging, and functionality assays. Our data suggest that differentiation toward definitive endoderm is more efficient without serum. Both collagen- and recombinant laminin-based coating supported differentiation of definitive endoderm, posterior definitive endoderm, and small intestinal epithelial cells from iPS-cells equally well. Small intestinal epithelial cells differentiated on recombinant laminin exhibited slightly more enterocyte specific cellular functionality than cells differentiated on Geltrex. Our data suggest that functional small intestinal epithelial cells can be generated from iPSCs in serum-free method on xeno-free substrata. This method is easily converted to an entirely xeno-free method.

Vinblastine treatment decreases the undifferentiated cell contamination of human iPSC-derived intestinal epithelial-like cells

Human induced pluripotent stem cell-derived intestinal epithelial cells (hiPSC-IECs) are expected to be utilized in regenerative medicine. To perform a safe transplantation without the risk of tumor formation, residual undifferentiated hiPSCs must be removed from hiPSC-IECs. In this study, we examined whether vinblastine (a multiple drug resistance 1 [MDR1] substrate) could remove residual undifferentiated hiPSCs in hiPSC-IECs and attempted to generate hiPSC-IECs applicable to transplantation medicine. We found that the expression levels of pluripotent markers were largely decreased and those of intestinal markers were increased by vinblastine treatment. The treatment of undifferentiated hiPSCs with vinblastine significantly decreased their viability. These results suggested that undifferentiated hiPSCs can be eliminated from hiPSC-IECs by vinblastine treatment. We hypothesized that MDR1-negative cells (such as undifferentiated hiPSCs) die upon vinblastine treatment because they are unable to excrete vinblastine. As expected, the cell viability of MDR1-knockout hiPSC-IECs was significantly decreased by vinblastine treatment. Furthermore, teratomas were formed by subcutaneous transplantation of hiPSC-IECs mixed with undifferentiated hiPSCs into mice, but they were not observed when the transplanted cells were pre-treated with vinblastine. Vinblastine-treated hiPSC-IECs would be an effective cell source for safe regenerative medicine.

In Vitro Human Cell-Based Experimental Models for the Evaluation of Enteric Metabolism and Drug Interaction Potential of Drugs and Natural Products

Elements of key enteric drug metabolism and disposition pathways are reviewed to aid the assessment of the applicability of current cell-based enteric experimental systems for the evaluation of enteric metabolism and drug interaction potential. Enteric nuclear receptors include vitamin D receptor, constitutive androstane receptor, pregnane X receptor, farnesoid X receptor, liver X receptor, aryl hydrocarbon receptor, and peroxisome proliferator-activated receptor. Enteric drug metabolizing enzyme pathways include both cytochrome P450 (P450) and non-P450 drug metabolizing enzymes based on gene expression, proteomics, and activity. Both uptake and efflux transporters are present in the small intestine, with P-glycoprotein found to be responsible for most drug-drug and food-drug interactions. The cell-based in vitro enteric systems reviewed are 1) immortalized cell line model: the human colon adenocarcinoma (Caco-2) cells; 2) human stem cell-derived enterocyte models: stem cell enteric systems, either from intestinal crypt cells or induced pluripotent stem cells; and 3) primary cell models: human intestinal slices, cryopreserved human enterocytes, permeabilized cofactor-supplemented (MetMax) cryopreserved human enterocytes, and cryopreserved human intestinal mucosa. The major deficiency with both immortalized cell lines and stem cell-derived enterocytes is that drug metabolizing enzyme activities, although they are detectable, are substantially lower than those for the intestinal mucosa in vivo. Human intestine slices, cryopreserved human enterocytes, MetMax cryopreserved human enterocytes, and cryopreserved human intestinal mucosa retain robust enteric drug metabolizing enzyme activity and represent appropriate models for the evaluation of metabolism and metabolism-dependent drug interaction potential of orally administered xenobiotics including drugs, botanical products, and dietary supplements. SIGNIFICANCE STATEMENT: Enteric drug metabolism plays an important role in the bioavailability and metabolic fate of orally administered drugs as well as in enteric drug-drug and food-drug interactions. The current status of key enteric drug metabolism and disposition pathways and in vitro human cell-based enteric experimental systems for the evaluation of the metabolism and drug interaction potential of orally administered substances is reviewed.