Stem Cells in Toxicology and Medicine E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 1581

Veröffentlichungsjahr: 2016

Beschreibung

A comprehensive and authoritative compilation of up-to-date developments in stem cell research and its use in toxicology and medicine

• Presented by internationally recognized investigators in this exciting field of scientific research
• Provides an insight into the current trends and future directions of research in this rapidly developing new field
• A valuable and excellent source of authoritative and up-to-date information for researchers, toxicologists, drug industry, risk assessors and regulators in academia, industry and government 

Leseprobe

Table of Contents

Cover

Title Page

List of Contributors

Preface

Acknowledgements

Part I

1 Introduction

References

2 Application of Stem Cells and iPS Cells in Toxicology

2.1 Introduction

2.2 Significance

2.3 Stem Cell (SC) Classification

2.4 Stem Cells and Pharmacotoxicological Screenings

2.5 Industrial Utilization Showcases Stem Cell Technology as a Research Tool

2.6 Multipotent Stem Cells (Adult Stem Cells) Characteristics and Current Uses

2.7 Mesenchymal Stem Cells (Adult Stem Cells)

2.8 Hematopoietic Stem Cells (Adult Stem Cells)

2.9 Cardiotoxicity

2.10 Hepatotoxicity

2.11 Epigenetic Profile

2.12 Use of SC and iPSC in Drug Safety

2.13 Conclusions and Future Applications

Acknowledgments

References

3 Stem Cells: A Potential Source for High Throughput Screening in Toxicology

3.1 Introduction

3.2 Stem Cells

3.3 High Throughput Screening (HTS)

3.4 Need for a Stem Cell Approach in High Throughput Toxicity Studies

3.5 Role of Stem Cells in High Throughput Screening for Toxicity Prediction

3.6 Conclusion

Acknowledgement

Disclosure Statement

Author’s Contribution

References

4 Human Pluripotent Stem Cells for Toxicological Screening

4.1 Introduction

4.2 The Biological Characteristics of hPSCs

4.3 Screening of Embryotoxic Effects using hPSCs

4.4 The Potential of hPSC-Derived Neural Lineages in Neurotoxicology

4.5 The Potential of hPSC -Derived Cardiomyocytes in Cardiotoxicity

4.6 The Potential of hPSC-Derived Hepatocytes in Hepatotoxicity

4.7 Future Challenges and Perspectives for Embryotoxicity and Developmental Toxicity Studies using hPSCs

Acknowledgments

References

5 Effects of Culture Conditions on Maturation of Stem Cell-Derived Cardiomyocytes

5.1 Introduction

5.2 Lengthening Culture Time

5.3 Substrate Stiffness

5.4 Structured Substrates

5.5 Conclusions

Disclaimer

References

6 Human Stem Cell-Derived Cardiomyocyte

In Vitro

Models for Cardiotoxicity Screening

6.1 Introduction

6.2 Overview of hPSC-Derived Cardiomyocytes

6.3 Human PSC-CM Models for Cardiotoxicity Investigations

6.4 Conclusions and Future Direction

References

7 Disease-Specific Stem Cell Models for Toxicological Screenings and Drug Development

7.1 Evidence for Stem Cell-Based Drug Development and Toxicological Screenings in Psychiatric Diseases, Cardiovascular Diseases and Diabetes

7.2 Disease-Specific Stem Cell Models for Drug Development in Psychiatric Disorders

7.3 Stem Cell Models for Cardiotoxicity and Cardiovascular Disorders

7.4 Stem Cell Models for Toxicological Screenings of EDCs

References

8 Three-Dimensional Culture Systems and Humanized Liver Models Using Hepatic Stem Cells for Enhanced Toxicity Assessment

8.1 Introduction

8.2 Hepatic Cell Lines and Primary Human Hepatocytes

8.3 Embryonic Stem Cells and Induced Pluripotent Stem-Cell Derived Hepatocytes

8.4

Ex Vivo

: Three-Dimensional and Multiple-Cell Culture System

8.5

In Vivo

: Humanized Liver Models

8.6 Summary

Acknowledgments

References

9 Utilization of

In Vitro

Neurotoxicity Models in Pre-Clinical Toxicity Assessment

9.1 Introduction

9.2 Current Models of Drug-Related Clinical Neuropathies and Effects on Electrophysiological Function

9.3 Cell Types that Can Potentially Be Used for

In Vitro

Neurotoxicity Assessment in Drug Development

9.4 Utility of iPSC Derived Neurons in

In Vitro

Safety Assessment

9.5 Summary of Key Points for Consideration in Neurotoxicity Assay Development

9.6 Concluding Remarks

References

10 A Human Stem Cell Model for Creating Placental Syncytiotrophoblast, the Major Cellular Barrier that Limits Fetal Exposure to Xenobiotics

10.1 Introduction

10.2 General Features of Placental Structure

10.3 The Human Placenta

10.4 Human Placental Cells in Toxicology Research

10.5 Placental Trophoblast Derived from hESC

10.6 Isolation of Syncytial Areas from BAP-Treated H1 ESC Colonies

10.7 Developmental Regulation of Genes Encoding Proteins Potentially Involved in Metabolism of Xenobiotics

10.8 Concluding Remarks

Acknowledgments

References

11 The Effects of Endocrine Disruptors on Mesenchymal Stem Cells

11.1 Mesenchymal Stem Cells

11.2 Endocrine Disruptors

11.3 Pesticides

11.4 Alkyl Phenols and Derivatives

11.5 Bisphenol A

11.6 Polychlorinated Biphenyls

11.7 Phthalates

11.8 Areas for Future Research

11.9 Conclusions

Abbreviations

References

12 Epigenetic Landscape in Embryonic Stem Cells

12.1 Introduction

12.2 DNA Methylation in ESCs

12.3 Histone Methylation in ESCs

12.4 Chromatin Remodeling and ESCs Regulation

12.5 Concluding Remarks

Acknowledgements

References

Part II

13 The Effect of Human Pluripotent Stem Cell Platforms on Preclinical Drug Development

13.1 Introduction

13.2 Core Signaling Pathways Underlying hPSC Stemness and Differentiation

13.3 Basic Components of

In Vitro

and

Ex Vivo

hPSC Platforms

13.4 Diverse hPSC Culture Platforms for Drug Discovery

13.5 Representative Analyses of hPSC-Based Drug Discovery

13.6 Current Challenges and Future Considerations

13.7 Concluding Remarks

Acknowledgments

References

14 Generation and Application of 3D Culture Systems in Human Drug Discovery and Medicine

14.1 Introduction

14.2 Traditional Scaffold-Based Tissue Engineering

14.3 Scaffold-Free 3D Culture Systems

14.4 Modular Biofabrication

14.5 3D Bioprinting

14.6 Tissue Modelling and Regenerative Medicine Applications of Pluripotent Stem Cells

14.7 Applications in Drug Discovery and Toxicity

14.8 Conclusions

References

15 Characterization and Therapeutic Uses of Adult Mesenchymal Stem Cells

15.1 Introduction

15.2 MSC Characterization

15.3 MSCs and Tissue or Organ Therapy

15.4 Conclusions

Acknowledgments

References

16 Stem Cell Therapeutics for Cardiovascular Diseases

16.1 Introduction

16.2 Types of Stem/Progenitor Cell-Derived Endothelial Cells

16.3 EPC and Other Stem/Progenitor Cell Therapy in CVDs

16.4 Strategies and Approaches for Enhancing EPC Therapy in CVDs

16.5 Concluding Remarks

Acknowledgments

References

17 Stem-Cell-Based Therapies for Vascular Regeneration in Peripheral Artery Diseases

17.1 Sources of Stem Cells for Vascular Regeneration

17.2 Canonic Mechanisms Governing Vascular Stem Cells Therapeutic Potential

17.3 Stem-Cell-Based Therapies in Patients with Peripheral Artery Disease

18 Gene Modified Stem/Progenitor-Cell Therapy for Ischemic Stroke

18.1 Introduction

18.2 Gene Modified Stem Cells for Ischemic Stroke

18.3 Gene Transfer Vectors

18.4 Unsolved Issues for Gene-Modified Stem Cells in Ischemic Stroke

18.5 Conclusion

Abbreviations

Acknowledgments

References

19 Role of Stem Cells in the Gastrointestinal Tract and in the Development of Cancer

19.1 Introduction

19.2 GI Development and Regeneration

19.3 GI Tumorigenesis and Stemness Gene Expression

19.4 Toxicants and Other Stress Trigger Epigenetic Changes, Dedifferentiation, and Carcinogenesis

19.5 Summary and Perspective

Acknowledgments

References

20 Cancer Stem Cells: Concept, Significance, and Management

20.1 Introduction

20.2 Stem Cells and Cancer: Historical Perspective

20.3 Cancer Stem Cells

20.4 Identification and Isolation of CSCs

20.5 Pathological Significance of Cancer Stem Cells

20.6 Pathways Regulating Cancer Stem Cells

20.7 Therapeutic Strategies Targeting Cancer Stem Cells

20.8 Conclusion and Future Directions

References

21 Stem Cell Signaling in the Heterogeneous Development of Medulloblastoma

21.1 Brain Tumor Cancer Stem Cells

21.2 Medulloblastoma

21.3 Hijacking Cerebellar Development

21.4 Molecular Classification of

MB

21.5 Mouse Models and Cell of Origin

21.6 Additional Drivers of

MB

21.7 Repurposing Off-Patent Drugs

21.8 Emerging Therapies for

MB

21.9 Conclusion

Acknowledgments

References

22 Induced Pluripotent Stem Cell-Derived Outer-Blood-Retinal Barrier for Disease Modeling and Drug Discovery

22.1 Introduction

22.2 The Outer Blood-Retinal Barrier

22.3 iPSC-Based Model of the Outer-Blood-Retinal-Barrier

22.4 iPSC Based OBRB Disease Models

22.5 Applications of iPSC-Based Ocular Disease Models for Drug Discovery

22.6 Conclusion and Future Directions

References

23 Important Considerations in the Therapeutic Application of Stem Cells in Bone Healing and Regeneration

23.1 Introduction

23.2 Stem Cells, Progenitor Cells, Mesenchymal Stem Cells

23.3 Scaffolds

23.4 Animal Models in Bone Healing and Regeneration

23.5 Conclusions and Future Directions

References

24 Stem Cells from Human Dental Tissue for Regenerative Medicine

24.1 Introduction

24.2 Dental Stem Cells

24.3 Potential Clinical Applications

24.4 Safety

24.5 Dental Stem Cell Banking

24.6 Conclusions and Perspective

References

25 Stem Cells in the Skin

25.1 Introduction

25.2 Stem Cells in the Skin

25.3 Isolation and the Biological Markers of Skin Stem Cells

25.4 Skin Stem Cell Niches

25.5 Signaling Control of Stem Cell Differentiation

25.6 Stem Cells in Skin Aging

25.7 Stem Cells in Skin Cancer

25.8 Medical Applications of Skin Stem Cells

25.9 Conclusions and Future Directions

References

Author Index

Subject Index

End User License Agreement

List of Tables

Chapter 02

Table 2.1

Advantage and Disadvantages for the use of hPS cells

Chapter 03

Table 3.1

A brief description of various stem cells is discussed

Chapter 04

Table 4.1

Summary of current development of biomarkers or methods in embryotoxic test using hPSCs

Table 4.2

Summary of current development of biomarkers or methods in neurotoxicology using hPSCs-derived neural lineages

Table 4.3

Summary of current development of biomarkers or methods in cardiotoxicity test using hPSCs-derived CMs

Table 4.4

Summary of current development of biomarkers or methods in hepatotoxicity test using hPSCs-derived hepatocytes

Chapter 05

Table 5.1

Current human gene names and their associated synonyms

Chapter 06

Table 6.1

Illustration of the platforms reviewed, and the overlap of some technologies across electrophysiology, contractility and structural cardiotoxicity applications

Chapter 09

Table 9.1

Cell models amendable to pharmaceutical assessments

Chapter 16

Table 16.1

Stem cell/EPC therapy in pre-clinical (animal) studies of PAD

Table 16.2

Stem cell/EPC therapy in pre-clinical (animal) studies of MI

Table 16.3

Stem/progenitor cell/EPC therapy in clinical studies of CVD

Chapter 17

Table 17.1

Randomized studies reported in peripheral arterial disease

Chapter 18

Table 18.1

Gene modified stem cells therapeutic in human diseases or animal models

Chapter 21

Table 21.1

General summary of MB molecular subtype characteristics

Chapter 22

Table 22.1

Derivation of retinal pigment epithelium from human induced pluripotent stem cells

Table 22.2

Ocular disease models utilizing iPSC-derived RPE

Chapter 23

Table 23.1

Summary of some of the published data where cell-based therapies have been used in bone pre-clinical models

List of Illustrations

Chapter 05

Figure 5.1

(Plate 1)

Examples of substrate patterns that have been used in an attempt to develop more mature cardiomyocytes. Various patterns in the substrate have been used alone or in conjunction with conditions listed on the right to produce a cardiomyocyte with a phenotype that is more similar to that of an adult cardiomyocyte.

Chapter 07

Figure 7.1

Disease-specific stem cell models represent a link between cell models and animal models in drug development and toxicological screenings

Chapter 09

Figure 9.1

(Plate 2)

High level neurotoxicity evaluation cascade in drug development. Preliminary assessments of the potential for neurotoxicity using simple

in vitro

tools aim to improve chemical matter and reduce the number of compounds moving through the pipeline as potential drug candidates. Once promising candidates have been selected, additional risks (depending on the target), and the mechanism of toxicity observed both pre-clinically and clinically can be evaluated in neuronal specific cell assays to query functional effects. Ultimately, these neuronal specific

in vitro

models further reduce the number of compounds that are assessed in animal studies and help to identify the molecular underpinnings of neurotoxicity. This diagram presents approaches conducted both at the early and late phase of drug development process.

Figure 9.2

(Plate 3)

Flowchart illustrating the incorporation of

in vitro

approaches for neurotoxicity assessment in the drug development process and highlights the potential impact on drug candidate selection and neurotoxicity risk assessment aiming to reduce the clinical impact on attrition.

Figure 9.3

(Plate 4)

Flexible dosing and scanning scheme for non-invasive live cell imaging over time using iPSC derived neurons. Cell cultures are maintained in a CO

2

and temperature controlled setting. Changes in neurite dynamics are observed during the experimental timeline, including apoptosis by Caspase 3/7 measurement (not shown). Pattern recognition software enables analysis of neurite length and cell bodies within each well measured over a period of time. D1 indicates Day 1 when the cells are treated and D3 represents Day 3 as the end of assay period. Scale for images is 200 μm

.

Figure 9.4

(Plate 5)

Differences in neurite changes and apoptosis upon treatment with varying doses of microtubule de-stabilizers or proteasome inhibitors on iPSC derived neurons over time. Live cell imaging over time and the capability to incorporate multi-parametric approaches in this assay enables the identification of molecules with different mechanism of action and may increase the sensitivity and neuro-specificity of the assay. Panel A. Microtubule de-stabilizer Vindesine induces neurite changes (A.i) prior to detection of apoptosis (A.ii). Panel B. Proteasome inhibitor Bortezomib induces concomitant toxicity in both parameters (B.i and B.ii)

.

Chapter 10

Figure 10.1

(Plate 6)

Cartoon illustrating some stages in human placental development (Knofler and Pollheimer

2013

). (A) After implantation, the conceptus has sunk below the luminal epithelial cells (LUE) of the uterine wall, and proliferating cells of polar trophectoderm (TE) give rise to a primitive syncytium (PS) by cell fusion. This cellular structure appears to be able to invade into the decidualized endometrium and interact with decidual fibroblasts (DF). Non-cellular areas, called lacunae (L) soon inter-connect with uterine vessels (UV), fill with blood, and are the precursors of the intervillous space. (B) Soon after implantation, columns of proliferating cytotrophoblast (CTB) grow through the syncytium to form primary villi. AE, amnion; UG, uterine gland. (C) The architecture of placental villi and the maternal-fetal interface of the human placenta towards the end of the first trimester of pregnancy. Two kinds of villi are encountered: floating villi unattached to maternal endometrium (not shown) and an anchoring villus (shown) that attaches the fetal placenta to the uterine wall. All the villi are covered with a thin layer of STB (S) above villous cytotrophoblast (vCTB) that provides the exchange surface of the placenta. Note that the STB (S) is directly exposed to maternal blood at its apical surface. The core of the villus is comprised mainly of placental connective tissue (pF) and blood vessels (pV). Extravillous trophoblast forms as columns (CCT) at the tips of the anchoring villi and invade into the maternal decidual tissue (DF). A subpopulation of extravillous trophoblast (eCTB) penetrates maternal spiral arteries (SA) and replaces the resident smooth muscle cells (SMC) and endothelium (EC). Other interstitial types (iCTB) penetrate more deeply into the endometrium and encounter maternal NK cell (uNK). So-called giant cells, which are areas of syncytium, are also present in the endometrium, but their origin is not clear. They may arise through fusion of extravillous trophoblast or be remnants of primitive syncytium from the early invasion stages (James, et al.

2012

; Knofler and Pollheimer

2013

).

Figure 10.2

(Plate 7)

STB emerging within colonies of H1 ESC after six days of BAP treatment (A) and illustration of the ESC/BAP differentiation procedure (B). The region shown here has been stained by immunofluorescence localization for CGA and CGB, and by DAPI for nuclear material. The third panel in (A) shows the merged images. These regions of developing syncytium stain for antigens known to be expressed in placental STB. These include CGA and CGB (shown here). CGA generally becomes expressed earlier in the formation of STB than CGB.

Figure 10.3

(Plate 8)

Images of three cell populations discussed in the text. (A) H1 embryonic stem cells (ESCu) stained by hemotoxilin/eosin (H & E, top) and stained by immunofluorescence localization of CGB and DAPI. The colonies of ESC were completely dissociated, and dispersed cells collected on a glass slide by using a Cytospin centrifuge procedure (www.thermoscientific.com/en/product/cytospin-4-cytocentrifuge.htmle). (B) Same as above, except the colonies had been differentiated to trophoblast by the BAP procedure (ESCd<40) and fractionated by filtration through a sieve (40 µm mesh size). Note that some fragments of STB are present (top) and that a few clumps stain faintly for CGB (bottom). (C) Same as above, except showing cell fractions retained by a sieve with a mesh size of 70 µm (ESCd > 70). Note the presence of many nuclei in extensive cellular sheets (top), most of which stain strongly for CGB (bottom).

Figure 10.4

(Plate 9)

Relative expression of CYP genes in H1 ESC (ESCu, blue/dark gray) and STB (ESCd>70, red/light gray). Genes (on the abscissa) marked with an asterisk (*) were expressed differently by the two cell types (FDR < 0.05). Data were obtained by RNAseq on cells at different passage numbers on three separate occasions. The differential expression analysis was performed by using Cufflinks. All values of < 0.01 were recorded as 0.01 to simplify data presentation. Gene expression values (FPKM; fragments per kilobase of exon per million reads) are shown on the ordinate axis.

Figure 10.5

(Plate 10)

Relative expression of SLC genes in H1 ESC (blue/dark gray) and STB (red/light gray). Genes (on the abscissa) marked with an asterisk (*) were expressed differently by the two cell types (FDR < 0.05). Presentation of data is described in

Fig. 10.4

. However, note the log scale for FPKM values on the ordinate.

Figure 10.6

(Plate 11)

Relative expression of ABC genes in H1 ESC (blue/dark gray) and STB (red/light gray). Genes (on the abscissa) marked with an asterisk (*) were expressed differently by the two cell types (FDR < 0.05). Presentation of data is described in

Fig. 10.4

. However, note the log scale for FPKM values on the ordinate.

Figure 10.7

(Plate 12)

Relative expression of MT genes in H1 ESC (blue/dark gray) and STB (red/light gray). Genes (on the abscissa) marked with an asterisk (*) were expressed differently by the two cell types (FDR < 0.05). Presentation of data is described in

Fig. 10.4

. However, note the log scale for FPKM values on the ordinate.

Chapter 11

Figure 11.1

(Plate 13)

(A) The effects of organophosphate pesticides on ASC differentiation into adipocytes. (B) The effects of organophosphate pesticides on BMSC differentiation into osteoblasts.

Figure 11.2

(Plate 14)

(A) The effects of DDT on preadipocyte differentiation into adipocytes. (B) The effects of DDT on BMSC differentiation.

Figure 11.3

(Plate 15)

(A) The effects of alkylphenols on preadipocyte differentiation into adipocytes. (B) The effects of alkylphenols on induction of apoptosis in osteoblasts.

Figure 11.4

(Plate 16)

(A) The effects of BPA at <10 μM and >10 μM concentrations on ASC differentiation into adipocytes. (B) The effects of BPA on BMSC differentiation into osteoblasts.

Figure 11.5

(Plate 17)

(A) The effects of PCBs on ASC differentiation into adipocytes. (B) The effects of PCBs on osteoblasts.

Figure 11.6

(Plate 18)

(A) The effects of phthalates on preadipocyte differentiation into adipocytes. (B) The effects of phthalates on osteoblasts.

Chapter 12

Figure 12.1

Bivalent domain in ESCs. PRC2 and MLL2 are responsible for H3K27 and H3K4 methylation, respectively

Chapter 15

Figure 15.1

Hypoxia promotes mesenchymal stem cell colony formation.

MSCs were seeded in 4-well chambers at 4500 cells per well (Lab-Tek Chambered #1.0 Borosilicate Coverglass System, Fisher, Rochester, NY). On day 10, the 4-well chambers were rinsed with phosphate-buffered saline (PBS) prior to the addition of methanol. After sitting for 5 minutes, the chambers were again rinsed with PBS. The well cover was removed, and when dry, 1 drop of mounting medium (Vector Laboratories, Inc.; Burlingame, CA) was then added to each well and a cover slip was applied. For analysis, a fluorescence microscope (Zeiss; Ontario, Canada) and Axiovision software were used to image the MSCs. (A) Representative colony under normoxia. (B) Representative colony under hypoxia

Figure 15.2

Radiation decreases AKT activation and increases JNK activation in mesenchymal stem cells (MSCs).

MSCs were irradiated at 4 or 6 Gy at 0.6 Gy/min with

60

Co-γ photons. Cell lysates were collected on day 2 after irradiation. AKT and JNK and their phosphorylation were detected using immunoblotting analysis. (A) Representative gels of AKT and its phosphorylation. (B) Representative gels of JNK and its phosphorylation

Figure 15.3

Radiation reduces ATP in cellular and mitochondria of mesenchymal stem cells (MSCs).

MSCs were irradiated at 4 or 6 Gy at 0.6 Gy/min with

60

Co-γ photons. Cells were collected on day 14 after irradiation. To fractionate intact mitochondria, a reagent-based method was employed using the Mitochondria Isolation Kit for Cultured Cells (Thermo Fisher Scientific, Inc.; Waltham, MA). Cultured cell pellets were gently lysed using a proprietary formulation resulting in maximum yield of mitochondria with minimal damage to integrity. After collecting mitochondrial and cellular fractions, mitochondrial and cellular ATP levels were measured using the ATP Bioluminescence Assay Kit HS II (Roche; Manheim, Germany). Luminescence was measured with a TD-20/20 luminometer (Turner Designs; Sunnyvale, CA). Data were normalized to total protein. ATP in cell (A) and mitochondria (B) was measured. *p < 0.05 vs. control; **p < 0.05 vs. 4 Gy, determined by Student’s t-test

Chapter 19

Figure 19.1

The process of cellular dedifferentiation and reprogramming from somatic cells to stem cells. When the cell accumulates stress including stimulation by somatic cell nuclear transfer (SCNT), transcription factors (TFs) such as Octamer-binding transcription factor 4 (OCT4), etc., chemicals, small molecules, tissue injury and repeated inflammation, apoptosis inducers, and/or hypoxic microenvironment. This results in demethylation, epigenetic barriers, or memory erasing, and finally triggers the dedifferentiation and partial or full reprogramming of the cell

Chapter 20

Figure 20.1

(Plate 19) Proposed models of cancer development and heterogeneity.

The stochastic model of cancer development advocates that all tumor cells have similar potential to divide and support growth of the tumor. These tumor cells are equipotent and can choose stochastically between self-renewal and differentiation. The cancer stem cell (CSCs) model of tumorigenesis proposes a hierarchical manner of cancer development and growth. According to this model, CSCs are the only cells with the potential to proliferate extensively and generate committed progenitor cells. These multiple progenitor cells can then further give rise to more differentiated cells, thus augmenting heterogeneity of the tumor mass.

Figure 20.2

(Plate 20) Origin of cancer stem cells.

The presence of cancer stem cells (CSCs) has been verified in several tumors, and various hypotheses have been proposed to understand the formation of CSCs: (A) CSCs can arise as a result of mutation and/or generic abnormalities in a normal stem cell, or from the progenitor cancer cell generated upon mutations in normal progenitor cells which re-acquire self-renewal ability, and/or of from a normal cell which may acquire mutations predisposing it to form potential CSCs after further mutations; (B) apoptosis of somatic cells in response to stress may cause release of fragmented DNA. These fragmented DNA can be taken up by other stem/progenitor cells through endocytosis or phagocytosis causing nuclear reprogramming of the acceptor cell and formation of potential CSCs. Furthermore, due the presence of viral particles, viral oncogenes can also be taken up by stem cells potentially reprogramming it to generate CSCs; and (C) fusion of cancer cells with a normal stem cell can lead to the generation of heterokaryon (multinucleated cell) or synkaryon (mononucleated cell). Loss of heterozygosity in heterokaryons leads to the generation of synkaryons. These hybrid cell thus generated may possess self-renewal activity as well as properties of transformed cells, that is, properties of CSCs

.

Figure 20.3

(Plate 21) Signaling pathways frequently utilized by cancer stem cells.

Transcription factors downstream of the represented signaling pathways have been associated in generation and maintenance of CSCs in different cancer types by upregulation of transcription factors such as Oct3/4, Sox2, Nanog, KLF-4, and so on, and stemness associated genes. These transcription factors further reinforce stemness and stem cell markers enhancing tumorigenecity and maintenance of CSC sub-population. DVL, Dishevelled homolog; EGF, Epidermal growth factor; FZD, Frizzed; GP130, membrane glycoprotein 130; Hh, Hedgehog; HIF, Hypoxia inducible factor; IL-6, interleukin-6; JAK, Janus kinase; mTOR, mammalian target of rapamycin; NICD, Notch intracellular domain; PDGF, platelet-derived growth factor; PI3K, Phosphoinositide 3-kinase; PTCH, protein Patched homolog; RTK, receptor tyrosine kinase; SMO, Smoothened; STAT, signal transducer and activator of transcription; SUFU, Suppressor of fused homolog; Wnt, Wingless-type

.

Figure 20.4

(Plate 22) A general overview of the concept of cancer stem cell-targeted therapy.

CSCs have been observed to be resistant to almost all of the current chemo and radiation therapies employed in the clinics. Thus, while an initial reduction in tumor burden is observed with these therapies, a relapse is almost always detected in these patients due to the surviving CSCs. Therefore, cancer therapies specifically targeting CSCs or a combination therapy targeting both the CSC subpopulation and differentiated cells have been investigated to enhance therapeutic outcomes

.

Chapter 21

Figure 21.1

Summary graphic of the cancer stem cell hypothesis. (A) Cancer stem cells (CSCs) have the ability to self-renew and differentiate into tumor bulk to re-establish tumor formation upon relapse. (B) Standard treatments that fail to target CSCs result in tumor regrowth, whereas elimination of CSCs in combination with therapies that target the growth of more differentiated cells may prevent relapse

Figure 21.2

Summary graphic of canonical WNT signaling pathway

Figure 21.3

Summary graphic of canonical SHH signaling pathway

Chapter 22

Figure 22.1

(Plate 23)

Diagram of a healthy human retina and outer blood-retinal barrier

.

Figure 22.2

(Plate 24)

Example of an OBRB model in a microfluidic chip with RPE cells in chamber 1 separated by a porous membrane from chamber 2 with endothelial cells

.

Chapter 23

Figure 23.1

(Plate 25)

The complex set of requirements that a successful candidate for a tissue regeneration scaffold should include.

Figure 23.2

(Plate 26)

Schematic representing the various species of graphene structures.

Chapter 24

Figure 24.1

(Plate 27)

Schematic drawing illustrating sources of human dental tissue-derived MSCs. DPSCs: dental pulp stem cells; SHED: stem cells from exfoliated deciduous teeth; PDLSCs: periodontal ligament stem cells; DFPCs: dental follicle progenitor cells; ABMSCs: alveolar bone-derived mesenchymal stem cells; SCAP: stem cells from the apical papilla; TGPCs: tooth germ progenitor cells; GMSCs: gingiva-derived MSCs.

Figure 24.2

(Plate 28)

Multilineage differentiation capacity, tissue regeneration and potential clinical applications of human dental tissue-derived MSCs. AD: Alzheimer’s dementia; PD: Parkinson’s disease; MCAO: middle cerebral artery occlusion; TLSCD: total limbal stem cell deficiency; SCI: spinal cord injury; CIA: collagen-induced arthritis; CHS: contact hypersensitivity; SLE: systemic lupus erythematosus.

Chapter 25

Figure 25.1

(Plate 29)

Distribution and the biological markers of skin stem cells.

Figure 25.2

(Plate 30)

Model of skin stem cell niches.

Figure 25.3

(Plate 31)

Wnt/β-catenin signaling pathway.

Figure 25.4

(Plate 32)

MAPK signaling pathway.

Figure 25.5

(Plate 33)

Notch signaling pathway.

Guide

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Table of Contents

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Stem Cells in Toxicology and Medicine

Editor

SAURA C. SAHU

Center for Food Safety and Applied Nutrition, US Food and Drug Administration, USA

This edition first published 2017© 2017 John Wiley & Sons, Ltd

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Library of Congress Cataloging‐in‐Publication Data

Names: Sahu, Saura C., editor.Title: Stem cells in toxicology and medicine / [edited by] Saura C. Sahu.Description: Chichester, UK ; Hoboken, NJ : John Wiley & Sons, 2017. | Includes bibliographical references and index.Identifiers: LCCN 2016025077 (print) | LCCN 2016039295 (ebook) | ISBN 9781119135418 (cloth) | ISBN 9781119135425 (pdf) | ISBN 9781119135449 (epub)Subjects: LCSH: Stem cells–Research. | Toxicology–Research.Classification: LCC QH588.S83 S74 2016 (print) | LCC QH588.S83 (ebook) | DDC 616.02/774–dc23LC record available at https://lccn.loc.gov/2016025077

A catalogue record for this book is available from the British Library.

Cover Image: thebackground/Gettyimages

Dedication

I lovingly dedicate this book to:My parents, Gopinath and Ichhamoni, for their gifts of life, love and living example.My wife, Jharana, for her life‐long friendship, love and support as well as for her patience and understanding about the long hours spent at home on planning, writing and editing this book.My children, Megha, Sudhir, and Subir, for their love and care.

Saura C. SahuLaurel, Maryland, USA

List of Contributors

David Anderson, Tissue Regeneration Laboratory, Department of Large Animal Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA

Shafquat Azim, Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA

Marjorie Bateman, Center for Stem Cell Research and Regenerative Medicine, Tulane University School of Medicine, New Orleans, LA, USA

Arun Bhardwaj, Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA

Kapil Bharti, Unit on Ocular and Stem Cell Translational Research, National Eye Institute, NIH, Bethesda, MD, USA

Alexandru Biris, Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, Little Rock, AK, USA

Shawn Bourdo, Center for Integrative Nanotechnology Sciences, University of Arkansas at Little Rock, Little Rock, AK, USA

Bruce A. Bunnell, Center for Stem Cell Research and Regenerative Medicine; and Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA

Matthew E. Burow, Department of Medicine, Tulane University School of Medicine, New Orleans, LA, USA

Maria Virginia Caballero, Biobide‐BBD BioPhenix S.L. Mikeletegi Pasealekua, Donostia, Gipuzkoa, Spain

Manila Candiracci, Department of Biomolecular Sciences, University of Urbino “Carlo Bo,” Urbino, Italy

Kevin G. Chen, NIH Stem Cell Unit, National Institute of Neurological Disorders and Stroke, NIH, Bethesda, MD, USA and Department of Microbiology and Immunology, Georgetown University Medical Center, Washington, DC, USA

Tong Cao, Oral Sciences Disciplines, Faculty of Dentistry, & Tissue Engineering Program, Life Sciences Institute, National University of Singapore, and NUS Graduate School for Integrative Science and Engineering, Singapore

Khuram Chaudhary, Safety Pharmacology, Mechanistic Safety and Deposition, GlaxoSmithKline, King of Prussia, PA, USA

Donna Dambach, Safety Assessment, Genentech, South San Francisco, CA, USA

Madhu Dhar, Tissue Regeneration Laboratory, Department of Large Animal Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA

Dunjin Chen, The Third Affiliated Hospital of Guangzhou Medical University, Key Laboratory for Major Obstetric Diseases of Guangdong Province, Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, Guangzhou, P.R. China

Lili Du, The Third Affiliated Hospital of Guangzhou Medical University, Key Laboratory for Major Obstetric Diseases of Guangdong Province, Key Laboratory of Reproduction and Genetics of Guangdong Higher Education Institutes, Guangzhou, P.R. China

Sandra E. Dunn, Phoenix Molecular Designs, Vancouver, BC, Canada

Hoda Elkhenany, Tissue Regeneration Laboratory, Department of Large Animal Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA; and Department of Surgery, Faculty of Veterinary Medicine, Alexandria University, Egypt

Ramon A. Espinoza‐Lewis, Synthetic Genomics Inc., San Diego, CA, USA

Toshihiko Ezashi, Division of Animal Sciences and Bond Life Sciences Center, University of Missouri, Columbia, MO, USA

Shukkur M. Farooq, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Xiaoqing Guan, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Harish K Handral, Oral Sciences Disciplines, Faculty of Dentistry, National University of Singapore, Singapore

Deborah K. Hansen, Division of Systems Biology, FDA/National Center for Toxicological Research, Jefferson, AR, USA

Kate Harris, Safety Pharmacology, Mechanistic Safety and Deposition, GlaxoSmithKline David Jack Centre for Research and Development, Ware, Herts, UK

D.C. Hay, MRC Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, UK

Joshua Holcomb, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Nathan Hotaling, Unit on Ocular and Stem Cell Translational Research, National Eye Institute, NIH, Bethesda, MD, USA

Yuning Hou, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Pengyu Huang, School of Life Science and Technology, ShanghaiTech University, Shanghai, P.R. China

Amy L. Inselman, Division of Systems Biology, FDA/National Center for Toxicological Research, Jefferson, AR, USA

Jun Jeon, Unit on Ocular and Stem Cell Translational Research, National Eye Institute, NIH, Bethesda, MD, USA

Juliane‐Susanne Jung, Department of Anatomy and Cell Biology, Martin Luther University Halle‐Wittenberg, Halle/Saale, Germany

Matthias Jung, Department of Psychiatry, Psychotherapy, and Psychosomatic Medicine, Martin Luther University Halle‐Wittenberg, Halle/Saale, Germany

Juliann G. Kiang, Radiation Combined Injury Program, Scientific Research Department, Armed Forces Radiobiology Research Institute, Department of Pharmacology and Molecular Therapeutics; Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA

Bin Li, Oregon Stem Cell Center, Oregon Health and Science University, Portland, OR, USA

Chunying Li, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Yaning Li, Neuroscience and Neuroengineering Research Center, Med‐X Research Institute and School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China

Junjun Liu, Department of Ophthalmology, Shanghai Tenth People’s Hospital, Tongji University School of Medicine, Shanghai, P.R. China; and Department of Stomatology, Huashan Hospital, Fudan University, Shanghai, P.R. China

Shangfeng Liu, Department of Stomatology, Huashan Hospital, Fudan University, Shanghai, P.R. China

Evie Maifoshie, Screening Profiling and Mechanistic Biology, NCE Molecular Discovery, GlaxoSmithKline Medicines Research Centre, Stevenage, Herts, UK

Saravanakumar Marimuthu, Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA

John McLachlan, Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA, USA

Dinah Misner, Safety Assessment, Genentech, South San Francisco, CA, USA

Mengyuan Niu, Medical School of Nanjing University, Nanjing, P.R. China

Mary C. Patton, Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA

H. Rashidi, MRC Centre for Regenerative Medicine, University of Edinburgh, Edinburgh, UK

R. Michael Roberts, Division of Animal Sciences and Bond Life Sciences Center, University of Missouri, Columbia, MO, USA

Saura C. Sahu, Division of Toxicology, Center for Food Safety and Applied Nutrition, Food and Drug Administration, USA

Jovita Schiller, Department of Psychiatry, Psychotherapy, and Psychosomatic Medicine, Martin Luther University Halle‐Wittenberg, Halle/Saale, Germany

Insa S. Schroeder, Department of Biophysics, GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany

Jean‐Sébastien Silvestre, INSERM UMRS 970, Université Paris Descartes, Sorbonne Paris Cité, Paris, France

Ajay P. Singh, Department of Oncologic Sciences, Mitchell Cancer Institute; and Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL, USA

Seema Singh, Department of Oncologic Sciences, Mitchell Cancer Institute; and Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, AL, USA

David M Smadja, INSERM UMRS 1140, Université Paris Descartes, Sorbonne Paris Cité; and AP‐HP, Hôpital Européen Georges Pompidou, Service d’hématologie Biologique, Paris, France

Nicholas Spellmon, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Shiyu Song, Medical School of Nanjing University, Nanjing, P.R. China

Gopu Sriram, Institute of Medical Biology, Agency for Science, Technology and Research (A*STAR), Singapore

Sanjeev K Srivastava, Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA

Karin Staflin, Safety Assessment, Genentech, South San Francisco, CA, USA

Amy L. Strong, Center for Stem Cell Research and Regenerative Medicine, Tulane University School of Medicine, New Orleans, LA, USA

Ting Su, Department of Dermatology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, P.R. China

Zhonglan Su, Department of Dermatology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, P.R. China

Xiaonan Sun, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Yaqi Sun, Department of Dermatology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, P.R. China

Hideki Taniguchi, Department of Regenerative Medicine, Yokohama City University School of Medicine, Yokohama, Japan

Joanna Triscott, Department of Pathology and Laboratory Medicine, Weill Cornell Medicine, New York, NY, USA

Tracy Walker, Investigative Safety and Drug Metabolism, Mechanistic Safety and Deposition, GlaxoSmithKline David Jack Centre for Research and Development, Ware, Herts, UK

Hongwei Wang, Medical School of Nanjing University, Nanjing, P.R. China

Peijun Wang, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Yongting Wang, Neuroscience and Neuroengineering Research Center, Med‐X Research Institute and School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China

Hui Xu, Medical School of Nanjing University, Nanjing, P.R. China

Wen Xue, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Shinichiro Yabe, Division of Animal Sciences and Bond Life Sciences Center, University of Missouri, Columbia, MO, USA

Guo‐Yuan Yang, Neuroscience and Neuroengineering Research Center, Med‐X Research Institute and School of Biomedical Engineering; and Department of Neurology, Ruijin Hospital, Shanghai Jiao Tong University, School of Medicine, Shanghai, P.R. China

Xi Yang, Division of Systems Biology, FDA/National Center for Toxicological Research, Jefferson, AR, USA

Ying Yang, Division of Animal Sciences and Bond Life Sciences Center, University of Missouri, Columbia, MO, USA

Zhe Yang, Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI, USA

Ran‐Ran Zhang, Department of Regenerative Medicine, Yokohama City University School of Medicine, Yokohama, Japan

Yun‐Wen Zheng, Department of Regenerative Medicine, Yokohama City University School of Medicine, Yokohama, Japan; Department of Advanced Gastroenterological Surgical Science and Technology, University of Tsukuba Faculty of Medicine, Tsukuba, Japan and Regenerative Medicine Research Center, Jiangsu University Hospital, Zhenjiang, China

Haseeb Zubair, Department of Oncologic Sciences, Mitchell Cancer Institute, University of South Alabama, Mobile, AL, USA

Preface

Stem cells are undifferentiated cells in multicellular organisms capable of growing into various differentiated cell types. In recent years they have become an important research tool in biology, medicine and toxicology leading to a rapidly developing new scientific discipline. This monograph focuses on their use in toxicology and medicine at a level designed to take readers to the frontiers of research in this specialized area. The importance of this field of research is evidenced by the increasing number of articles published each year. This rapid development requires new means to report the results of ongoing studies. The contributions presented in this monograph represent a collaborative effort by international experts working in this emerging field of science. The main aim of this book is to present state‐of‐the‐art information on stem cells in one place. Therefore, I sincerely hope that this book will provide a comprehensive and authoritative source of current information on stem cells and prove useful to the investigators and students working in this scientific discipline throughout the world for years to come. It is my hope that the information presented in this book will serve as a stimulus to them. Also it is my hope that it will be of interest to a variety of other scientific disciplines including pharmacology, food, drug, and environmental sciences. In addition, this book should be of interest to the safety assessors and regulators of food, drug, environment, agriculture, and consumer products.

Saura C. SahuLaurel, Maryland, USA

Acknowledgements

Editing this book was a challenge for me. Several people have influenced me directly or indirectly. I express my sincere gratitude to them.

I am indebted to the internationally recognized experts for sharing my enthusiasm for this book and for their generous contributions. I carefully selected them from academia, industry and government for their expertise in their own areas of research. Their works speak for themselves. I am sincerely grateful to these scientists for their strong commitment, cooperation and excellent contributions.

I thank the staff of the John Wiley & Sons, Ltd, especially Jenny Cossham, Rebecca Ralf, and Janine Maer for their excellent help, cooperation, support, and editorial assistance for the timely publication of this book.

Saura C. SahuLaurel, Maryland, USA

Part I

1Introduction

Saura C. Sahu

Division of Toxicology, Center for Food Safety and Applied Nutrition, Food and Drug Administration, USA

Stem cells are the mothers of all cells in multicellular organisms. They have the potential to become any other type of cell in the body. They are undifferentiated cells of the same family capable of dividing throughout life, generating new highly differentiated cells of unlimited potency. Because of their unique regenerative abilities, they can serve as an internal repair system to replenish damaged or dead cells in many tissues. Therefore, they have attracted increasing amounts scientific attention for their potential use in biomedical applications.

The studies by McCulloch and Till published in 1963 (Becker et al., 1963; Siminovitch et al., 1963) gave birth to modern stem cell research. Over a period of approximately half a century, there was exponential growth in this developing new area of scientific research. Stem cells have the capacity to grow in culture continuously in an undifferentiated state renewing themselves to more specialized differentiated cells. Therefore, they have become a very important and useful in vitro research tool in toxicology and medicine. They can be used as excellent in vitro models for predictive toxicity screening of chemicals and new drugs. Thus, the study of stem cells is a new developing scientific discipline and their use in toxicology and medicine is unlimited.

It is becoming increasingly clear from the rate of publications that developments in the use of stem cells in toxicology and medicine are moving so rapidly that new means are needed to report the current status of this new active area of research. As the Editor of this monograph Stem Cells in Toxicology and Medicine, it gives me great pride and pleasure to introduce this unique book that encompasses many aspects of stem cell research never published together before. It is only recently that this exciting area of research has attracted the attention of toxicologists. This book deals with information on stem cells at a level designated to take the reader to the frontier of research in this specific new developing scientific discipline. It is expected that stem cell research, actively pursued throughout the world, will lead to major discoveries of fundamental importance and of great clinical significance. This monograph brings together the ideas and work of investigators of international reputation who have pioneered in this exciting area of research in toxicology and medicine. The book provides up‐to‐date information as well as new challenges in this exciting area of research. This book reflects the remarkable developments in the stem cell technology in recent years. New ideas and new approaches are being brought to bear on explorations of the role played by these unique cells in toxicology and medicine. Therefore, exciting times lie ahead for the future of stem cell research. I sincerely hope that the book will provide authoritative information as well as new ideas and challenges in this area of research for stimulating the creativity of investigators actively engaged in this rapidly developing new scientific discipline.

References

Becker AJ, McCulloch EA, Till JE (1963). Cytological demonstration of the clonal nature of spleen colonies derived from transplanted mouse marrow cells.

Nature

197 (4866): 452–454. Bibcode: 1963Natur.197. 452B. doi: 10.1038/197452a0. PMID 13970094.

Siminovitch L, Mcculloch EA, Till JE (1963). The distribution of colony‐forming cells among spleen colonies.

Journal of Cellular and Comparative Physiology

62 (3): 327

–

336. doi:10.1002/jcp.1030620313. PMID 14086156.

2Application of Stem Cells and iPS Cells in Toxicology

Maria Virginia Caballero1, Ramon A. Espinoza‐Lewis2, and Manila Candiracci3

1 Biobide‐BBD BioPhenix S.L. Mikeletegi Pasealekua, Donostia, Gipuzkoa, Spain

2 Synthetic Genomics Inc., San Diego, CA, USA

3 Department of Biomolecular Sciences, University of Urbino “Carlo Bo,” Urbino, Italy

2.1 Introduction

Fertilization of an oocyte by a spermatozoid, or in general terms, fertilization of the female gamete by the male gamete results in the genesis of the basic unit in the development of an organism, the embryo. The primordial unicellular embryo will, after several rounds of division, develop into a multicellular organism and ultimately into an offspring resembling its progenitors in structure and function. At the molecular level, embryonic development is governed by the expression and interaction of a specific set of genes, certain proteins and peptides, and the signaling of growth factors. In other words, embryonic development is a complex process, which involves a vast but specific genetic network corresponding to its different stages.

Early observations made in the sea urchin (Driesch, 1892, 1893, 1894; Gilbert, 2000; Roux, 1888; Roux, 1894) demonstrated that splitting a two‐cell embryo into single cells resulted in the emergence of two fully developed organisms. Hans Spemann repeated these experiments in the salamander two‐cell embryo, ultimately obtaining two fully developed “twins” (Gilbert, 2000; Spemann, 1921). These early experiments demonstrated the totipotency of the early embryonic cells and the retention of certain “information,” which allows for the development of an organism. This information is progressively lost as the embryo develops and its cells differentiate and reach more specific roles (Gilbert, 2000; Spemann, 1921). However, the question remains, what is the stage at which cells lose this potential?

Further experimentation revealed that cells derived from teratomas, or from mouse blastocysts inner cell mass (ICM) cultured upon a suitable fibroblast feeder layer, continue to proliferate without overt differentiation and remain totipotent (Evans and Kaufman 1981; Martin 1981). Consequently, when these Embryonic Stem Cells (ESc) are removed from the differentiation‐inhibitory influence of the feeder cells, or equivalent, they will spontaneously differentiate into developing embryo‐like structures of increasing complexity, or embryoid bodies (EBs) (Doetschman et al., 1985; Martin and Lock, 1983). Embryoid bodies thus, enable researchers to study different aspects of early embryonic development. Indeed, with the advent of novel molecular biology techniques, it has been demonstrated that these cells are competent for gene targeting via homologous recombination or site directed mutagenesis. They are competent for the generation of genetically modified model systems, including mouse models for the study of developmental embryonic formation, diseases driven by genetic mutation, transcriptional regulation, or molecular toxicological effects (Boch, 2011; Bradley et al., 1984; Capecchi, 1980; Hendel et al., 2015; Koller et al., 1989; Mali et al., 2013; Smithies et al., 1985; Thomas and Capecchi, 1990).

2.2 Significance

Understanding stem cells and iPS cells in terms of their dynamic differential molecular signatures opens new avenues for the study of the effects of pharmaceutical chemicals at the cellular, physiological, and ultimately the molecular levels. Furthermore, stem cells and pluripotent stem cells present clear advantages compared to other model systems currently used for testing pharmaceutical compounds. The traditional methods for compound testing include the use of primary cells and/or live models, such as mouse or zebrafish (Parasuraman, 2011; Sipes et al., 2011). Primary cells from any organ present the difficulty of the initial isolation, quantity and quality per isolated batch, and different proliferation capacities, making industrial scalability a difficult process. Furthermore, genetic background variability leads to inconsistent cellular responses which in turn lead to a broad array of results, interpretations and conclusions (McGivern and Ebert, 2014). Stem cells, and especially induced pluripotent stem cells, circumvent the majority of these obstacles. Indeed, isolation of somatic tissue cells, whether it is skin cells, blood cells, or epithelial cells harvested from urine (Zhao et al., 2013), is relatively easy, non‐invasive, and most importantly, patient specific. Harvested cells are genetically homogenous, whether these are from non‐diseased or diseased patients, allowing for direct experimental testing; cellular responses are consistent and variability is minimal. Pluripotent stem cells possess a high self‐renewal capacity and proliferate unlimitedly. Indeed, recent reports indicate that high cellular passage (higher than 60) have no effect in proliferation rates or in differentiation potential (Burridge et al., 2014). Pluripotent stem cells that possess unlimited proliferation, that is, cells that surpass the Hayflick limit (Hayflick, 1965; Hayflick and Moorhead, 1961), have been reported to be highly related to telomerase activity and hTERT expression necessary for telomere length maintenance (Huang et al., 2011). This unlimited proliferation indicates that scalability necessary for industrial testing is achievable (Couture, 2010). Furthermore, iPS cell growth and differentiation in vitro using cell culture techniques and materials amount to a fraction of the cost invested in live animal models (Burridge et al., 2014). Finally, the most important characteristic of iPS cells is related to their specific human physiological identity. Historically, pharmaceutical testing has been performed in live animal models, such as mice, zebrafish, rats and pigs; however, iPS cells are of human origin, and the molecular, physiological and cellular responses are the most adequate for molecular testing, especially in studies related to electrical conduction such as neuronal or cardiac. It is known, for example, that cardiac ion channels which rectify the cardiac rhythm are different in rats from those in humans, thus, extrapolation of results is inconclusive (Grant, 2009; Han et al., 2010). Finally, iPS cells are derived from differentiated adult human tissue and not from a surplus of fertilized human embryos; therefore, iPS cells are not in conflict with any religious or humanistic ethical principles (McGivern and Ebert, 2014).

As noted previously, the understanding of stem cells, in terms of cell renewal and differentiation capacity, and the acquired knowledge of their dynamic differential molecular signatures, leads to new routes of research to investigate the effects of pharmaceutical chemicals at the cellular, physiological, and molecular levels. Furthermore, iPS cells are physiologically relevant, genetically homogenous, amount to a considerably lower cost and are free of ethical conflicts. Taken all together, these characteristics make stem cells and pluripotent stem cells a highly beneficial research and industrial platform, especially for studies aimed at pharmacodynamic/kinetic outcomes and toxicological screenings (McGivern and Ebert, 2014).

2.3 Stem Cell (SC) Classification

Since their discovery, stem cells have been the object of intense study. As noted above, stem cells were initially identified and characterized as immortal cells isolated from teratomas (cancerous embryoid‐like bodies) (Martin, 1981). However, further research demonstrated that stem cells are varied and tissue‐context dependent. Indeed, embryonic stem cells are found and isolated from the inner cell mass (ICM) of the early mouse blastocyst and from the fetal umbilical cord blood (Evans and Kaufman, 1981). Additionally, stem cells can also be found in skeletal muscle, as a satellite cell population (Hawke and Garry, 2001); the bone marrow, as hematopoietic progenitor cells (Sieburg et al., 2006); the small intestine, as crypt cells (Barker, 2014). In other words, stem cells are found in every tissue/organ and display a differential potential for self‐renewal and regenerative capacity.

Thus, by their origin, stem cells are classified as: (1) Embryonic stem cells, (2) Fetal stem cells, and (3) Adult stem cells. By their potential of self‐renewal and regenerative capacity, stem cells are classified as: (1) Totipotent, (2) Pluripotent, (3) Multipotent, (4) Oligopotent, and (5) Unipotent (Bissels et al., 2013).