Thyroid in a jar: towards an integrated in vitro testing strategy for thyroid-active compounds

Jomaa, B. (2015). Thyroid in a Jar: Towards an Integrated In Vitro Testing Strategy for Thyroid-Active Compounds. PhD thesis, Wageningen University, the Netherlands Abstract The aim of this thesis was to find in vitro and toxicogenomics-based alternatives to in vivo thyroid hormone disruption tests. In vitro alternatives can help reduce the amount of animal testing required under the European Union regulation for the registration, evaluation, authorization and restriction of chemicals (REACH). Moreover, with the use of human cell lines and human-identical synthetic proteins, interspecies differences can be reduced and in some cases eliminated. This thesis has shed light on the relevance of current in vitro assays for thyroid and pituitary cell proliferation, has led to the development of the TSH screen, a luminol-based thyroid peroxidase inhibition assay and the zebrafish-based general development score (GDS) for the detection of developmental toxicants, including those that act through the thyroid hormone system. Moreover, the microarray assay for real-time coregulator-nuclear receptor interaction (MARCoNI) assay was used to reveal the modulating effects of thyroid-active compounds on TRα and TRβ interactions with a peptide array representing 66 different coregulators. These developments along with an in-depth analysis of the thyroid hormone system and the presentation of the state of the art in thyroid disruption testing have highlighted the progress made and at the same time have underlined the challenges that lay ahead.