[Frontiers in Bioscience 17, 1965-1975, January 1, 2012]

Innovative approaches in the embryonic stem cell test (EST)

Peter T. Theunissen1,2, Aldert H. Piersma1,3

1Laboratory for Health Protection Research, National Institute for Public Health and the Environment, RIVM, Bilthoven, The Netherlands, 2Department of Toxicogenomics, Maastricht University, Maastricht, The Netherlands, 3Institute for Risk Assessment Sciences, Veterinary Faculty, Utrecht University, Utrecht, The Netherlands


1. Abstract
2. Development of the embryonic stem cell test (EST)
2.1. Definition of the EST
2.2. ECVAM validation of the EST
2.3. EST: Post validation
2.4. Defining the applicability domain
2.5. The applicability domain of compound classes for the EST
2.6. Implementation of the EST within testing strategies
3. Quantitative endpoints for the EST
3.1. Alternative EST endpoints
3.2. Optimization of the classical EST
3.3. Molecular endpoints in the EST
3.4. Omics technologies as endpoints for the EST
4. Alternative differentiation models
4.1. Neural differentiation EST
4.2. Osteoblast differentiation EST
4.3. Metabolism in the EST
4.4. Human EST
5. Future Developments
6. References


The embryonic stem cell test (EST) is a high-throughput in vitro screening assay for developmental toxicity free of animal use. The EST uses the ability of murine embryonic stem cells to differentiate into the mesodermal cardiac lineage in combination with two cytotoxicity test systems. Validation of the EST showed that the test system is very promising as an alternative method to animal testing, however to optimize predictability and increase knowledge on the applicability domain of the EST, improvements to the method were proposed and studied. In this review we discuss the first definition of the EST followed by the innovative approaches which have been proposed to increase the predictivity of the EST, including implementation of molecular endpoints in the EST, such as omics technologies and the addition of alternative differentiation models to the testing paradigm, such as neural and osteoblast differentiation and the use of human stem cells. These efforts to improve the EST increase the value of embryonic stem cells used as in vitro systems to predict developmental toxicity.