We thank M. Kapitza, Margit Henry, Tamara Rotshteyn, Susan Rohani and Cornelia B&#246;ttinger for excellent technical support. This work was supported by grants from the German Research Foundation (RTG 1331) and the German Ministry for Research (BMBF).

<ol>
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The authors have nothing to disclose.

Traditional approaches to toxicological testing involve extensive animal studies thus making testing costly and time-consuming. Moreover, due to the interspecies differences the preclinical animal safety studies are not always valid to predict toxicity effects of potential drugs relevant for humans. Although non-human primates are most predictable, still strong ethical, and socioeconomical demands are rapidly raising by modern societies for developing sensitive and robust in vitro test system relevant t...

The ability of human embryonic stem cells (hESC) to differentiate into various types of cells opened up a new era of in vitro toxicity testing1, disease modelling and regenerative medicine2. The stem cells are endowed with the capacity to self-replicate, to keep their pluripotent state, and to differentiate into specialized cells3,4. The properties of hESC (capacity to differentiate to all major cell types) are also found in other human pluripotent stem cells, such as human induced pluripotent stem cells (hiPSC) or cells generated by nuclear transfer5. For instance, many different hESC lines have been differentiated into neurons6, renal cells7, neural crest cells8, cardiomyocytes9-12, or hepatocytes like cells13,14. Moreover, hESC can spontaneously differentiate into cells of all three germ layers15-18 in embryoid bodies (EBs)19,20. Early embryonic development is regulated by differential expression of various genes related to the different germ layers which has been captured at mRNA level by transcriptomics using microarray technology15. These efforts resulted in the establishment of organ specific toxicological models based on hESC/hiPSC and transcriptomics analysis (for review see 21,22). These models have advantages over the traditional use of laboratory animals for toxicological studies, as preclinical studies using laboratory animals are not always predictive of human safety. The drug induced toxicities encountered in patients are often related to metabolic or signaling processes that differ between humans and experimental animals. The species difference has prevented the reliable early detection of developmental toxicity in humans, and for instance drugs such as thalidomide23,24 and diethylstilbestrol25,26 were withdrawn from the market due to teratogenicity. Thalidomide has not shown any developmental toxicity in rats or mice. Environmental chemicals such as methyl mercury27 resulted in prenatal developmental toxicity with respect to the nervous system in various species, but human manifestations have been hard to model in animals. To address the problem of species specificity issues, scientists working under different projects based on stem cells like ReProTect, ESNATS, DETECTIVE etc. are engaged in the development of different models for embryonic toxicity, neurotoxicity, cardiotoxicity, hepatotoxicity and nephrotoxicity using human toxicants suspected to affect humans. Under the European consortium project &#39;Embryonic Stem cell-based Novel Alternative Testing Strategies (ESNATS)&#39; five test systems have been established. One test system the so called UKK (Universit&#228;tsklinikum K&#246;ln) test system partially captures early human embryonic development. In this system human embryonic H9 cells are differentiated in to three germ layers (ectoderm, endoderm and mesoderm)15 and germ layer specific signatures have been captured by transcriptomics profile using the Affymetrix microarray platform. Various developmental toxicants like thalidomide28, valproic acid, methyl mercury16,17, or cytosine arabinoside15 have been tested in this system, and toxicant specific gene signatures have been obtained. In a second test system, the so called the UKN1 (University of Konstanz) test system 1, H9 cells are differentiated to neuroectodermal progenitor cells (NEP) for 6 days. This is evidenced by high expression of neural gene markers such as PAX6 and OTX2. During differentiation for 6 days, NEP cells have been exposed to developmental neuro-toxicants such as VPA, methyl mercury. Toxicant-specific de-regulated transcriptomics profiles have been obtained as well by using the Affymetrix microarray platform16,29.
The new vision for toxicology of the 21st century envisages that test systems do not only yield phenotypic descriptions like histopathology in vivo, or transcriptome changes at the end of long-term toxicant incubations. It rather suggests that assays provide mechanistic information3, and that this information can be mapped to so-called adverse outcome pathways (AOP) that provide a scientific rationale for hazardous effects30. To provide such information, the test systems applied have to be highly quality controlled31, as for instance documented by robust standard operation procedures. Moreover, time-dependent changes need to be mapped with high resolution. This requires test systems with synchronized changes32. The UKN1 and UKK test systems described here have been optimized for these requirements.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>DMEM/F-12</td>
			<td>Life Technologies</td>
			<td>11320082</td>
			<td>Dulbecco&#39;s Modified Eagle Medium:Nutrient Mixture F-12</td>
		</tr>
		<tr>
			<td>KOSR</td>
			<td>Life Technologies</td>
			<td>10828028</td>
			<td>Knockout Serum Replacement</td>
		</tr>
		<tr>
			<td>GlutaMAX</td>
			<td>Life Technologies</td>
			<td>35050061</td>
			<td>GlutaMAX supplement</td>
		</tr>
		<tr>
			<td>NEAA</td>
			<td>Life Technologies</td>
			<td>11140050</td>
			<td>MEM Nonessential Amino Acids Solution</td>
		</tr>
		<tr>
			<td>DPBS</td>
			<td>Life Technologies</td>
			<td>14190-0144</td>
			<td>Dulbecco&#39;s Phosphate-Buffered Saline, without calcium, without magnesium</td>
		</tr>
		<tr>
			<td>mTeSR medium</td>
			<td>Stemcell Technologies</td>
			<td>5850</td>
			<td></td>
		</tr>
		<tr>
			<td>Pluronic F-127</td>
			<td>Sigma</td>
			<td>P2443-250G</td>
			<td></td>
		</tr>
		<tr>
			<td>V bottom plate</td>
			<td>VWR</td>
			<td>734-0483</td>
			<td>Plate,Microwell,V BTTM,96 Well,Sterile 1 * 50 ST</td>
		</tr>
		<tr>
			<td>Vbottom plate lid</td>
			<td>VWR</td>
			<td>634-0011</td>
			<td>Lid, Microtitre plates, Cond. Ring 1 * 50 ST</td>
		</tr>
		<tr>
			<td>Pen/Strep</td>
			<td>Life Technologies</td>
			<td>15140-122</td>
			<td>Penicillin- Streptomycin, Liquid</td>
		</tr>
		<tr>
			<td>Distilled Water</td>
			<td>Life Technologies</td>
			<td>15230-089.</td>
			<td>Sterile Distilled Water</td>
		</tr>
		<tr>
			<td>Human FGF-2 (bFGF)</td>
			<td>Millipore</td>
			<td>GF003AF-100UG</td>
			<td>Fibroblast Growth Factor basic, human recombinant, animal-free</td>
		</tr>
		<tr>
			<td>Filter 0.22 &#956;m</td>
			<td>Millipore</td>
			<td>SCGPU02RE</td>
			<td>Stericup-GP, 0.22 &#956;m, polyethersulfone, 250 ml, radio- sterilized</td>
		</tr>
		<tr>
			<td>StemPro EZPassageTM Disposablte</td>
			<td>Invitrogen</td>
			<td>23181010</td>
			<td></td>
		</tr>
		<tr>
			<td>BD MatrigelTM, hESC qualified Matrix</td>
			<td>Stemcell Technologies</td>
			<td>354277</td>
			<td>5 ml vial</td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma</td>
			<td>D-2650</td>
			<td></td>
		</tr>
		<tr>
			<td>RNAlater Stabilization Solution</td>
			<td>Life Technologies</td>
			<td>AM7020</td>
			<td>It stabilizes and protect the RNA integrity in unfrozen samples.</td>
		</tr>
		<tr>
			<td>70 &#956;m Cell Strainer</td>
			<td>Becton Dickinson</td>
			<td>352350</td>
			<td>Cell strainer with 70 &#956;m Nylon mesh</td>
		</tr>
		<tr>
			<td>35 &#956;m Lid cell strainer, 5 ml tube</td>
			<td>Becton Dickinson</td>
			<td>352235</td>
			<td>5 ml polystyrene round bottom test tube, with a cell strainer cap (35 &#956;m)</td>
		</tr>
		<tr>
			<td>50 ml sterile Polypropylene tube</td>
			<td>Greiner Bio-One</td>
			<td>227261</td>
			<td>50 ml Polypropylene tube with conical bottom, Sterile</td>
		</tr>
		<tr>
			<td>T75 flask</td>
			<td>Greiner Bio-One</td>
			<td>658175</td>
			<td>CELLSTAR Filter Cap Cell Culture 75 cm2 Flasks</td>
		</tr>
		<tr>
			<td>TRIzol</td>
			<td>Life Technologies</td>
			<td>10296010</td>
			<td></td>
		</tr>
		<tr>
			<td>96 well optical bottom plates</td>
			<td>Thermo Scientific</td>
			<td>165305</td>
			<td></td>
		</tr>
		<tr>
			<td>CellTiter-Blue</td>
			<td>Promega</td>
			<td>G8081</td>
			<td></td>
		</tr>
		<tr>
			<td>Accutase</td>
			<td>PAA</td>
			<td>L11-007</td>
			<td></td>
		</tr>
		<tr>
			<td>Apotransferin</td>
			<td>Sigma-Aldrich</td>
			<td>T-2036</td>
			<td></td>
		</tr>
		<tr>
			<td>Dispase</td>
			<td>Worthington Biochemicals</td>
			<td>LS002104</td>
			<td></td>
		</tr>
		<tr>
			<td>Dorsomorphin</td>
			<td>Tocris Bioscience</td>
			<td>3093</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Roth</td>
			<td>8043.2</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>PAA</td>
			<td>A15-101</td>
			<td></td>
		</tr>
		<tr>
			<td>FGF-2</td>
			<td>R&#38;D Systems</td>
			<td>233-FB</td>
			<td></td>
		</tr>
		<tr>
			<td>Gelatine</td>
			<td>Sigma-Aldrich</td>
			<td>G1890-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>G7021-100G</td>
			<td></td>
		</tr>
		<tr>
			<td>GlutaMAX</td>
			<td>Gibco Invitrogen</td>
			<td>35050-038</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Gibco Invitrogen</td>
			<td>15630-056</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>Sigma-Aldrich</td>
			<td>I-6634</td>
			<td></td>
		</tr>
		<tr>
			<td>Knockout DMEM</td>
			<td>Gibco Invitrogen</td>
			<td>10829-018</td>
			<td></td>
		</tr>
		<tr>
			<td>Matrigel</td>
			<td>BD Biosciences</td>
			<td>354234</td>
			<td></td>
		</tr>
		<tr>
			<td>Noggin</td>
			<td>R&#38;D Systems</td>
			<td>719-NG</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Biochrom AG</td>
			<td>L1825</td>
			<td></td>
		</tr>
		<tr>
			<td>Progesteron</td>
			<td>Sigma-Aldrich</td>
			<td>P7556</td>
			<td></td>
		</tr>
		<tr>
			<td>Putrescine</td>
			<td>Sigma-Aldrich</td>
			<td>P-5780</td>
			<td></td>
		</tr>
		<tr>
			<td>ROCK inhibitor Y-27632</td>
			<td>Tocris Biosciences</td>
			<td>1254</td>
			<td></td>
		</tr>
		<tr>
			<td>SB431542</td>
			<td>Tocris Biosciences</td>
			<td>1614</td>
			<td></td>
		</tr>
		<tr>
			<td>SDS</td>
			<td>Bio-Rad</td>
			<td>161-0416</td>
			<td></td>
		</tr>
		<tr>
			<td>Selenium</td>
			<td>Sigma-Aldrich</td>
			<td>S-5261</td>
			<td></td>
		</tr>
		<tr>
			<td>&#946;-Mercaptoethanol</td>
			<td>Gibco Invitrogen</td>
			<td>31350-010</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>List of Kits</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>RNeasy Mini Kit (250)</td>
			<td>QIAGEN</td>
			<td>74106</td>
			<td></td>
		</tr>
		<tr>
			<td>GeneChip Hybridization, Wash, and Stain Kit</td>
			<td>Affymetrix</td>
			<td>900721, 22, 23</td>
			<td>This kit provides all reagents required for hybridization wash and staining of microarrays.</td>
		</tr>
		<tr>
			<td>Rnase-Free DNase Set</td>
			<td>QIAGEN</td>
			<td>79254</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td colspan="4">List of equipment.</td>
		</tr>
		<tr>
			<td>Inverted microscope</td>
			<td>Olympus</td>
			<td></td>
			<td>IX71</td>
		</tr>
		<tr>
			<td>Genechip Hybridisation Oven - 645</td>
			<td>Affymetrix</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Genechip Fluidics Station-450</td>
			<td>Affymetrix</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Affymetrix Gene-Chip Scanner-3000-7 G</td>
			<td>Affymetrix</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Spectramax M5</td>
			<td>Molecular Devices</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>List of softwares</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Prism 4</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Affymetrix GCOS</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Partek Genomic Suite 6.25</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Online tools for Functional annotation 
			DAVID 
			Onto-tools Intelligent Systems and Bioinformatics Laboratory</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

human pluripotent stem cell based developmental toxicity assays for chemical safety screening and systems biology data generation

Efficient protocols to differentiate human pluripotent stem cells to various tissues in combination with -omics technologies opened up new horizons for in vitro toxicity testing of potential drugs. To provide a solid scientific basis for such assays, it will be important to gain quantitative information on the time course of development and on the underlying regulatory mechanisms by systems biology approaches. Two assays have therefore been tuned here for these requirements. In the UKK test system, human embryonic stem cells (hESC) (or other pluripotent cells) are left to spontaneously differentiate for 14 days in embryoid bodies, to allow generation of cells of all three germ layers. This system recapitulates key steps of early human embryonic development, and it can predict human-specific early embryonic toxicity/teratogenicity, if cells are exposed to chemicals during differentiation. The UKN1 test system is based on hESC differentiating to a population of neuroectodermal progenitor (NEP) cells for 6 days. This system recapitulates early neural development and predicts early developmental neurotoxicity and epigenetic changes triggered by chemicals. Both systems, in combination with transcriptome microarray studies, are suitable for identifying toxicity biomarkers. Moreover, they may be used in combination to generate input data for systems biology analysis. These test systems have advantages over the traditional toxicological studies requiring large amounts of animals. The test systems may contribute to a reduction of the costs for drug development and chemical safety evaluation. Their combination sheds light especially on compounds that may influence neurodevelopment specifically.

Methyl mercury exposure in UKK test system
The cytotoxicity assay was performed with H9 EBs to obtain an IC10 value (reduction of viability by 10%) for the cytotoxicity of methyl mercury (Figure 1). We also performed a microarray based (affymetrix platform) biomarker study. The H9 EBs have been exposed to methyl mercury (0.25 and 1 &#181;M) for 14 days. On day 14, samples have been collected using TRIzol and RNA was isolated. Transcriptional profiling was performed ...

Watch this Scientific Journal Video about Human Pluripotent Stem Cell Based Developmental Toxicity Assays for Chemical Safety Screening and Systems Biology Data Generation at JoVE.com

Human Pluripotent Stem Cell Based Developmental Toxicity Assays for Chemical Safety Screening and Systems Biology Data Generation

The protocols describe two in vitro developmental toxicity test systems (UKK and UKN1) based on human embryonic stem cells and transcriptome studies. The test systems predict human developmental toxicity hazard, and may contribute to reduce animal studies, costs and the time required for chemical safety testing.

Efficient protocols to differentiate human pluripotent stem cells to various tissues in combination with -omics technologies opened up new horizons for in ...

human-pluripotent-stem-cell-based-developmental-toxicity-assays-for

Research

JoVE Journal

Developmental Biology

12.4K Views.  University of Cologne. The protocols describe two in vitro developmental toxicity test systems (UKK and UKN1) based on human embryonic stem cells and transcriptome studies. The test systems predict human developmental toxicity hazard, and may contribute to reduce animal studies, costs and the time required for chemical safety testing.