Exploring the biological domain of the cardiac embryonic stem cell test: In search for biomarkers of developmental toxicity for optimizing an animal-free alternative test system

The use of animals to assess the safety of potentially hazardous chemicals and drugs for humans is becoming increasingly controversial. Animal-free tests are being developed to reduce and replace animal testing, for example by culturing cells in Petri dishes. Such cell cultures are also called in vitro tests. This dissertation describes investigations on a stem cell-based in vitro test for predicting chemical safety for early embryo development. Stem cells have the capacity to become every cell type within the body and in the stem cell test they are stimulated to become heart muscle cells. The overall aim was to explore and improve our knowledge on the available biological processes within the stem cell test besides heart muscle cell development, and to use this knowledge to better discriminate between molecules of the same class of structurally related chemicals. This work contributes to our mechanism-based knowledge for hazard assessment of chemicals, which is generally lacking in the standard developmental toxicity studies in laboratory animals. The achievements in this dissertation also included the identification of additional cell types like neural crest cells and neural cells. Further insight was gained on the impact of in vitro culture conditions like the oxygen levels in the cell’s surroundings. These findings can influence the discrimination between structurally related chemicals. In the future, this in vitro test can contribute to animal-free safety testing of chemicals, when used together with other in vitro tests and computer models. More research is needed to improve our understanding of such in vitro tests even more and to implement them into animal-free test systems