Human embryonic stem cells as a model system for studying the effects of smoke exposure on the embryo

Effect of cigarette smoke condensate on mouse embryo development and expression of pluripotency and apoptotic genes in vitro

The aim of the present study was to investigate the effect of cigarette smoke condensate (CSC) on in vitro development of mouse embryos. In total 3000 NMRI mice 2PN embryos were divided into six groups (n = 500). The test group was exposed to 20, 40, 80, 160 or 320 μg/ml of CSC. In the control group, CSC was not added to the culture medium during the development of 2PN embryos. The effects of 20 and 80 μg/ml of CSC on genes involved in pluripotency and apoptosis, and also, the aryl hydrocarbon receptor gene was assessed in the blastocysts. Our results showed that CSC had an adverse effect on the viability of mouse embryos at the concentrations of 80, 160 and 320 μg/ml compared with the control group (P < 0.05). In contrast, it had positive effects on the viability of mouse embryos at the concentrations of 20 and 40 μg/ml compared with the control group (P < 0.05). The 20 and 80 μg/ml concentrations of CSC increased the expression of pluripotency, apoptotic, and aryl hydrocarbon receptor genes in the blastocyst embryo stage compared with the control group (P < 0.05). It can be concluded that concentrations higher than 40 μg/ml of CSC have an adverse effect on mouse embryo development in the preimplantation stages. Also, 20 and 80 μg/ml concentrations of CSC have a significant effect on the expression of pluripotency, apoptotic, and the aryl hydrocarbon receptor genes in the blastocyst embryo stage compared with the control group.

Apoptotic effects of cigarette smoke extracts on mouse embryonic stem cells via oxidative stress

Previous studies have reported that cigarette smoke and cigarette smoke extract (CSE) have negative effects on embryonic development. However, no studies have investigated the mechanism through which CSE affects the cellular signaling pathway leading to apoptosis and oxidative stress in embryonic cells, or how the two pathways are cross-linked. Thus, we studied the effects of CSE on apoptosis and oxidative stress in mouse embryonic stem cells (mESCs). Specifically, we measured changes in cell viability in response to CSEs (3R4F and two domestic cigarettes CSE 1 and 2) using a water soluble tetrazolium (WST) assay and a neutral red uptake (NRU) assay, which revealed that cell viability decreased in a concentration-dependent manner. Western blot analysis revealed that the expression of cyclin D1 and cyclin E1 was decreased and that of p21 and p27 was increased by CSE. Additionally, the number of terminal deoxynucleotidyl transferase (TUNEL)-stained cells was increased by CSE, while the levels of Bax and Caspase-3 increased and Bcl-2 decreased. Moreover, a 2',7'-dichlorofluorescin diacetate (DCF-DA) assay and reactive oxygen species (ROS)-Glo H2 O2 assay confirmed that ROS were generated in response to CSE and that they were associated with up-regulated Keaf-1 and CHOP. Overall, the results revealed that cigarette smoke extract (CSE) inhibited cell proliferation by regulating cell cycle-related protein expression and increased oxidative stress by regulating the expression of Kelch-like ECH-associated protein 1 (Keap-1) and CCAAT/enhancer-binding protein homologous protein (CHOP), resulting in apoptosis in mESCs.

Single-Cell RNA Sequencing of Human Embryonic Stem Cell Differentiation Delineates Adverse Effects of Nicotine on Embryonic Development

Nicotine, the main chemical constituent of tobacco, is highly detrimental to the developing fetus by increasing the risk of gestational complications and organ disorders. The effects of nicotine on human embryonic development and related mechanisms, however, remain poorly understood. Here, we performed single-cell RNA sequencing (scRNA-seq) of human embryonic stem cell (hESC)-derived embryoid body (EB) in the presence or absence of nicotine. Nicotine-induced lineage-specific responses and dysregulated cell-to-cell communication in EBs, shedding light on the adverse effects of nicotine on human embryonic development. In addition, nicotine reduced cell viability, increased reactive oxygen species (ROS), and altered cell cycling in EBs. Abnormal Ca2+ signaling was found in muscle cells upon nicotine exposure, as verified in hESC-derived cardiomyocytes. Consequently, our scRNA-seq data suggest direct adverse effects of nicotine on hESC differentiation at the single-cell level and offer a new method for evaluating drug and environmental toxicity on human embryonic development in utero.

Effects of cigarette smoke condensate on proliferation and pluripotency gene expression in mouse embryonic stem cells

BACKGROUND

Embryonic stem cells (ESCs) are derived from the inner cell mass (ICM) of blastocysts. They can be used as valuable experimental models to test the effects of drugs, chemicals, and environmental contaminants such as cigarette smoke condensate (CSC) on preimplantation embryo development. The aim of this study was to evaluate the effect of CSC on ESCs derived from mice with different genetic backgrounds and maternal ages.

METHODS

The study groups consisted of mouse ESCs (mESCs) obtained from three sources: blastocysts developed from fertilized oocytes of two-month-old (2-C57) and six-month-old (6-C57) C57BL/6 inbred mice and those developed from fertilized oocytes of two-month-old (2-NMRI) NMRI outbred mice. The groups of mESCs were exposed to 0.04, 4, and 40 μg/mL CSC. After exposure, we measured cell viability by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and real-time polymerase chain reaction for changes in expressions of Oct4, Sox2, Nanog, Ahr, Bax, Bcl2, TFAM, and POLG. The cell doubling time (DT) of these populations was also determined.

RESULTS

We observed that CSC changed proliferation and DT in the 2-C57 and 6-C57 cells. There was no change in 2-NMRI cells. Exposure to CSC caused changes in the gene expressions and induced apoptosis in all three cell lines.

CONCLUSION

Based on the results of the study, it can be concluded that CSC has an effect on the viability, DT and gene expression patterns in mouse ESCs and its effects vary based on the genetic background and maternal age of isolated mouse ESCs.

Bidirectional Regulation of Mouse Embryonic Stem Cell Proliferation by Nicotine Is Mediated Through Wnt Signaling Pathway

Introduction:

Nicotine is a key biologically active compound of cigarettes. Although nicotine is a risk factor for various health issues, it may also be beneficial when treated at moderate concentrations. Nicotine has been shown to bidirectionally regulate stem cell proliferation and differentiation depending on the doses applied. It is not clear whether or how nicotine regulates mouse embryonic stem cell (mESC) survival and proliferation.

Methods:

Mouse embryonic stem cells were cultured in the presence of 0.01, 0.1, 1, or 10 μM nicotine. The effects of nicotine on cell survival and proliferation were examined. The signaling pathway that mediated these effects was analyzed.

Results:

Cell viability was not affected by nicotine at all 4 concentrations examined. The proliferation of mESCs was promoted by 0.01 and 0.1 μM nicotine and suppressed by 1 and 10 μM. This dose-dependent regulation was mediated through the Wnt/β-catenin pathway. Modulation of Wnt/β-catenin activity either worsens or reverses the effects of nicotine.

Conclusions:

We have identified a bidirectional function of nicotine on mESC proliferation through regulation of the Wnt/β-catenin pathway and this is associated with different doses. This study suggests that concentration of nicotine is a crucial aspect for consideration when designing research or therapeutic strategies.

Effect of nicotine on the proliferation and chondrogenic differentiation of the human Wharton's jelly mesenchymal stem cells

BACKGROUND

Osteoarthritis (OA) is a chronic joint disease characterized by a progressive and irreversible degeneration of articular cartilage. Among the environmental risk factors of OA, tobacco consumption features prominently, although, there is a great controversy regarding the role of tobacco smoking in OA development. Among the numerous chemicals present in cigarette smoke, nicotine is one of the most physiologically active molecules.

OBJECTIVE

The aim of the study was (i) to measure the impact of nicotine on the proliferation and chondrogenic differentiation of mesenchymal stem cells from the human Wharton's jelly (hWJ-MSCs) into chondrocytes, (ii) to investigate whether the α7 nicotinic acetylcholine receptors (nAChRs) was expressed in hWJ-MSCs and could play a role in the process. The project benefits from the availability of an umbilical cord bank from which hWJ-MSCs were originated.

METHODS

The hWJ-MSCs were cultured and used up to passage 5. The proliferation of hWJ-MSCs with 5 μM nicotine was measured by the MTT assay on the 1st, 2nd, 3rd, and 6th day. Flow cytometry analysis was used to detect cell apoptosis/necrosis by Annexin V/PI double-staining. The chondrogenic differentiation grade of hWJ-MSCs induced by TGFβ3 was assessed by the Sirius red and Alcian blue staining. The expression of markers genes was followed by quantitative real-time PCR. The expression of nAChRs was followed by RT-PCR. The functional activity of α7 nAChR was evaluated by calcium (Ca2+) influx mediated by nicotine using the Fluo-4 NW Calcium assay.

RESULTS

The proliferation of hWJ-MSCs was significantly impaired by nicotine (5 μM) from the 3rd day of treatment, but nicotine did not significantly induce modifications on the viability of hWJ-MSCs. Alcian blue staining indicated that the amount of proteoglycan was more abundant in control group than in the nicotine group, but no difference was observed on the total collagen amount using Sirius red staining. The mRNA expression of Sox9, type II collagen (Col2a1), aggrecan in control group was higher than in the nicotine group. We found that hWJ-MSCs expressed α7 nAChR. The receptor agonist nicotine caused calcium (Ca2+) influx into hWJ-MSCs suggesting that the calcium ion channel α7 homopolymer could mediate this response.

CONCLUSIONS

At the concentration used, nicotine had an adverse effect on the proliferation and chondrogenic differentiation of hWJ-MSCs which was probably impaired through a α7 nAChR mediation.

An animal model of effects of nicotine exposure on endometrial receptivity and embryo implantation in pregnancy

OBJECTIVE

This study aims at evaluating the endometrial receptivity in uterus of pregnant rats exposed to nicotine via examination of integrin expression by immunohistochemical effect.

METHODS

In this study, 16 healthy pregnant rats were divided into two groups of control and study groups each comprising eight rats. The rats randomised to study group were given a certain amount of nicotine before and during the pregnancy. Integrin expression was detected in uterus of all rats by immunohistochemical staining. The effect of nicotine exposure on embryo implantation and the endometrial receptivity were immunohistochemically and pathologically evaluated.

RESULTS

Comparison of both groups revealed no difference in living, viable foetuses. Intensity and universality of immunohistochemical staining of Integrin β3 for endometrial epithelium and endometrial stroma were detected to be identical between the groups.

CONCLUSION

No immunochemical effect was observed on integrin expression, which is a very important part of receptivity in an animal model created with pregnant rats that were transdermally exposed to nicotine. Our study demonstrated that the harmful effect of nicotine use before and pregnancy on implantation is limited at the level of integrin expression, in a dose-dependent manner and also by considering the method of administration.

Diverse neurotoxicants target the differentiation of embryonic neural stem cells into neuronal and glial phenotypes

The large number of compounds that needs to be tested for developmental neurotoxicity drives the need to establish in vitro models to evaluate specific neurotoxic endpoints. We used neural stem cells derived from rat neuroepithelium on embryonic day 14 to evaluate the impact of diverse toxicants on their ability to differentiate into glia and neurons: a glucocorticoid (dexamethasone), organophosphate insecticides (chlorpyrifos, diazinon, parathion), insecticides targeting the GABA_A receptor (dieldrin, fipronil), heavy metals (Ni²⁺, Ag⁺), nicotine and tobacco smoke extract. We found three broad groupings of effects. One diverse set of compounds, dexamethasone, the organophosphate pesticides, Ni²⁺ and nicotine, suppressed expression of the glial phenotype while having little or no effect on the neuronal phenotype. The second pattern was restricted to the pesticides acting on GABA_A receptors. These compounds promoted the glial phenotype and suppressed the neuronal phenotype. Notably, the actions of compounds eliciting either of these differentiation patterns were clearly unrelated to deficits in cell numbers: dexamethasone, dieldrin and fipronil all reduced cell numbers, whereas organophosphates and Ni²⁺ had no effect. The third pattern, shared by Ag⁺ and tobacco smoke extract, clearly delineated cytotoxicity, characterized by major cell loss with suppression of differentiation into both glial and neuronal phenotypes; but here again, there was some selectivity in that glia were suppressed more than neurons. Our results, from this survey with diverse compounds, point to convergence of neurotoxicant effects on a specific "decision node" that controls the emergence of neurons and glia from neural stem cells.

Nicotine induces mitochondrial fission through mitofusin degradation in human multipotent embryonic carcinoma cells

Nicotine is considered to contribute to the health risks associated with cigarette smoking. Nicotine exerts its cellular functions by acting on nicotinic acetylcholine receptors (nAChRs), and adversely affects normal embryonic development. However, nicotine toxicity has not been elucidated in human embryonic stage. In the present study, we examined the cytotoxic effects of nicotine in human multipotent embryonal carcinoma cell line NT2/D1. We found that exposure to 10 μM nicotine decreased intracellular ATP levels and inhibited proliferation of NT2/D1 cells. Because nicotine suppressed energy production, which is a critical mitochondrial function, we further assessed the effects of nicotine on mitochondrial dynamics. Staining with MitoTracker revealed that 10 μM nicotine induced mitochondrial fragmentation. The levels of the mitochondrial fusion proteins, mitofusins 1 and 2, were also reduced in cells exposed to nicotine. These nicotine effects were blocked by treatment with mecamylamine, a nonselective nAChR antagonist. These data suggest that nicotine degrades mitofusin in NT2/D1 cells and thus induces mitochondrial dysfunction and cell growth inhibition in a nAChR-dependent manner. Thus, mitochondrial function in embryonic cells could be used to assess the developmental toxicity of chemicals.

Cardiac development in zebrafish and human embryonic stem cells is inhibited by exposure to tobacco cigarettes and e-cigarettes

Background

Maternal smoking is a risk factor for low birth weight and other adverse developmental outcomes.

Objective

We sought to determine the impact of standard tobacco cigarettes and e-cigarettes on heart development in vitro and in vivo.

Methods

Zebrafish (Danio rerio) were used to assess developmental effects in vivo and cardiac differentiation of human embryonic stem cells (hESCs) was used as a model for in vitro cardiac development.

Results

In zebrafish, exposure to both types of cigarettes results in broad, dose-dependent developmental defects coupled with severe heart malformation, pericardial edema and reduced heart function. Tobacco cigarettes are more toxic than e-cigarettes at comparable nicotine concentrations. During cardiac differentiation of hESCs, tobacco smoke exposure results in a delayed transition through mesoderm. Both types of cigarettes decrease expression of cardiac transcription factors in cardiac progenitor cells, suggesting a persistent delay in differentiation. In definitive human cardiomyocytes, both e-cigarette- and tobacco cigarette-treated samples showed reduced expression of sarcomeric genes such as MLC2v and MYL6. Furthermore, tobacco cigarette-treated samples had delayed onset of beating and showed low levels and aberrant localization of N-cadherin, reduced myofilament content with significantly reduced sarcomere length, and increased expression of the immature cardiac marker smooth muscle alpha-actin.

Conclusion

These data indicate a negative effect of both tobacco cigarettes and e-cigarettes on heart development in vitro and in vivo. Tobacco cigarettes are more toxic than E-cigarettes and exhibit a broader spectrum of cardiac developmental defects.

Nicotine exposure during differentiation causes inhibition of N-myc expression

Background

The ability of chemicals to disrupt neonatal development can be studied using embryonic stem cells (ESC). One such chemical is nicotine. Prenatal nicotine exposure is known to affect postnatal lung function, although the mechanisms by which it has this effect are not clear. Since fibroblasts are a critical component of the developing lung, providing structure and secreting paracrine factors that are essential to epithelialization, this study focuses on the differentiation of ESC into fibroblasts using a directed differentiation protocol.

Methods

Fibroblasts obtained from non-human primate ESC (nhpESC) differentiation were analyzed by immunohistochemistry, immunostaining, Affymetrix gene expression array, qPCR, and immunoblotting.

Results

Results of these analyses demonstrated that although nhpESCs differentiate into fibroblasts in the presence of nicotine and appear normal by some measures, including H&E and SMA staining, they have an altered gene expression profile. Network analysis of expression changes demonstrated an over-representation of cell-cycle related genes with downregulation of N-myc as a central regulator in the pathway. Further investigation demonstrated that cells differentiated in the presence of nicotine had decreased N-myc mRNA and protein expression and longer doubling times, a biological effect consistent with downregulation of N-myc.

Conclusions

This study is the first to use primate ESC to demonstrate that nicotine can affect cellular differentiation from pluripotency into fibroblasts, and in particular, mediate N-myc expression in differentiating ESCs. Given the crucial role of fibroblasts throughout the body, this has important implications for the effect of cigarette smoke exposure on human development not only in the lung, but in organogenesis in general.

Telomere shortening and DNA damage of embryonic stem cells induced by cigarette smoke

Embryonic stem cells (ESCs) provide a valuable in vitro model for testing toxicity of chemicals and environmental contaminants including cigarette smoke. Mouse ESCs were acutely or chronically exposed to smoke components, cigarette smoke condensate (CSC), or cadmium, an abundant component of CSC, and then evaluated for their self-renewal, apoptosis, DNA damage and telomere function. Acute exposure of ESCs to high dose of CSC or cadmium increased DNA damage and apoptosis. Yet, ESCs exhibited a remarkable capacity to recover following absence of exposure. Chronic exposure of ESCs to low dose of CSC or cadmium resulted in shorter telomeres and DNA damage. Together, acute exposure of ESCs to CSC or cadmium causes immediate cell death and reduces pluripotency, while chronic exposure of ESCs to CSC or cadmium leads to DNA damage and telomere shortening. Notably, a sub-proportion of ESCs during passages is selected to resist to smoke-induced oxidative damage to telomeres.

Comparison of electronic cigarette refill fluid cytotoxicity using embryonic and adult models

Electronic cigarettes (EC) and refill fluids are distributed with little information on their pre- and postnatal health effects. This study compares the cytotoxicity of EC refill fluids using embryonic and adult cells and examines the chemical characteristics of refill fluids using HPLC. Refill solutions were tested on human embryonic stem cells (hESC), mouse neural stem cells (mNSC), and human pulmonary fibroblasts (hPF) using the MTT assay, and NOAELs and IC(50)s were determined from dose-response curves. Spectral analysis was performed when products of the same flavor had different MTT outcomes. hESC and mNSC were generally more sensitive to refill solutions than hPF. All products from one company were cytotoxic to hESC and mNSC, but non-cytotoxic to hPF. Cytotoxicity was not due to nicotine, but was correlated with the number and concentration of chemicals used to flavor fluids. Additional studies are needed to fully assess the prenatal effect of refill fluids.

Developmental effects of tobacco smoke exposure during human embryonic stem cell differentiation are mediated through the transforming growth factor-β superfamily member, Nodal

While the pathologies associated with in utero smoke exposure are well established, their underlying molecular mechanisms are incompletely understood. We differentiated human embryonic stem cells in the presence of physiological concentrations of tobacco smoke and nicotine. Using post hoc microarray analysis, quantitative PCR, and immunoblot analysis, we demonstrated that tobacco smoke has lineage- and stage-specific effects on human embryonic stem cell differentiation, through both nicotine-dependent and -independent pathways. We show that three major stem cell pluripotency/differentiation pathways, Notch, canonical Wnt, and transforming growth factor-β, are affected by smoke exposure, and that Nodal signaling through SMAD2 is specifically impacted by effects on Lefty1, Nodal, and FoxH1. These events are associated with upregulation of microRNA-302a, a post-transcriptional silencer of Lefty1. The described studies provide insight into the mechanisms by which tobacco smoke influences fetal development at the cellular level, and identify specific transcriptional, post-transcriptional, and signaling pathways by which this likely occurs.

The effect of nicotine on the mechanical properties of mesenchymal stem cells

PURPOSE: To measure the elasticity of the nucleus and cytoplasm of human mesenchymal stem cells (MSCs) as well as changes brought about by exposure to nicotine in vitro. METHODS: MSCs were synchronized to the G(0) stage of the cell cycle through serum deprivation techniques. The cells were then treated with medium containing nicotine (0.1 µM, 0.5 µM, and 1 µM). Atomic force microscopy was then used to measure the Young's modulus of both the nucleus and cytoplasm of these cells. RESULTS: For both unsynchronized and synchronized cells, the nucleus was softer than the cytoplasm, although this difference was not found to be statistically significant. The nucleus of cells treated with nicotine was significantly stiffer than the control for all concentrations. The cytoplasm was significantly stiffer in nicotine-treated cells than in control cells for the 0.5 µM and 1.0 µM concentrations only. CONCLUSIONS: The results of this study could suggest that nicotine affects the biophysical properties of human MSCs in a dose-dependent manner, which may render the cells less responsive to mechanoinduction and other physical stimuli.

Constructing and deconstructing stem cell models of neurological disease

Among the disciplines of medicine, the study of neurological disorders is particularly challenging. The fundamental inaccessibility of the human neural types affected by disease prevents their isolation for in vitro studies of degenerative mechanisms or for drug screening efforts. However, the ability to reprogram readily accessible tissue from patients into pluripotent stem (iPS) cells may now provide a general solution to this shortage of human neurons. Gradually improving methods for directing the differentiation of patient-specific stem cells has enabled the production of several neural cell types affected by disease. Furthermore, initial studies with stem cell lines derived from individuals with pediatric, monogenic disorders have validated the stem cell approach to disease modeling, allowing relevant neural phenotypes to be observed and studied. Whether iPS cell-derived neurons will always faithfully recapitulate the same degenerative processes observed in patients and serve as platforms for drug discovery relevant to common late-onset diseases remains to be determined.

Present state and future perspectives of using pluripotent stem cells in toxicology research

The use of novel drugs and chemicals requires reliable data on their potential toxic effects on humans. Current test systems are mainly based on animals or in vitro–cultured animal-derived cells and do not or not sufficiently mirror the situation in humans. Therefore, in vitro models based on human pluripotent stem cells (hPSCs) have become an attractive alternative. The article summarizes the characteristics of pluripotent stem cells, including embryonic carcinoma and embryonic germ cells, and discusses the potential of pluripotent stem cells for safety pharmacology and toxicology. Special attention is directed to the potential application of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) for the assessment of developmental toxicology as well as cardio- and hepatotoxicology. With respect to embryotoxicology, recent achievements of the embryonic stem cell test (EST) are described and current limitations as well as prospects of embryotoxicity studies using pluripotent stem cells are discussed. Furthermore, recent efforts to establish hPSC-based cell models for testing cardio- and hepatotoxicity are presented. In this context, methods for differentiation and selection of cardiac and hepatic cells from hPSCs are summarized, requirements and implications with respect to the use of these cells in safety pharmacology and toxicology are presented, and future challenges and perspectives of using hPSCs are discussed.

Comparison of the toxicity of smoke from conventional and harm reduction cigarettes using human embryonic stem cells

This study evaluated the hypothesis that smoke from harm reduction cigarettes impedes attachment and proliferation of H9 human embryonic stem cells (hESCs). Smoke from three harm reduction brands was compared with smoke from a conventional brand. Doses of smoke were measured in puff equivalents (PE) (1 PE = the amount of smoke in one puff that dissolves in 1 ml of medium). Cytotoxic doses were determined using morphological criteria and trypan blue staining, and apoptosis was confirmed using Magic Red staining. Attachment and proliferation of hESC were followed at a noncytotoxic dose in time-lapse videos collected using BioStation technology. Data were mined from videos either manually or using video bioinformatics subroutines developed with CL-Quant software. Mainstream (MS) and sidestream (SS) smoke from conventional and harm reduction cigarettes induced apoptosis in hESC colonies at 1 PE. At 0.1 PE (noncytotoxic), SS smoke from all brands inhibited attachment of hESC colonies to Matrigel with the strongest inhibition occurring in harm reduction brands. At 0.1 PE, SS smoke, but not MS smoke, from all brands inhibited hESC growth, and two harm reduction brands were more potent than the conventional brand. In general, hESC appeared more sensitive to smoke than their mouse ESC counterparts. Although harm reduction cigarettes are often marketed as safer than conventional brands, our assays show that SS smoke from harm reduction cigarettes was at least as potent or in some cases more potent than smoke from a conventional brand and that SS smoke was more inhibitory than MS smoke in all assays.

Human pluripotent stem cells in drug discovery and predictive toxicology

Human pluripotent stem cells are a biological resource most commonly considered for their potential in cell therapy or, as it is now called, ‘regenerative medicine’. However, in the near future, their most important application for human health may well be totally different, as they are more and more envisioned as opening new routes for pharmacological research. Pluripotent stem cells indeed possess the main attributes that make them theoretically fully equipped for the development of cell-based assays in the fields of drug discovery and predictive toxicology. These cells are characterized by: (i) an unlimited self-renewal capacity, which make them an inexhaustible source of cells; (ii) the potential to differentiate into any cell phenotype of the body at any stage of differentiation, with probably the notable exception, however, of the most mature forms of many lineages; and (iii) the ability to express genotypes of interest via the selection of donors, whether they be of embryonic origin, through pre-implantation genetic diagnosis, or adults, by genetic reprogramming of somatic cells, so-called iPSCs (induced pluripotent stem cells). In the present review, we provide diverse illustrations of the use of pluripotent stem cells in drug discovery and predictive toxicology, using either human embryonic stem cell lines or iPSC lines.