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Development of an In Vitro Human Thyroid Microtissue Model for Chemical Screening
Citation:
Deisenroth, C., V. Soldatow, J. Ford, W. Stewart, C. Brinkman, D. Macmillan, E. LeCluyse, AND R. Thomas. Development of an In Vitro Human Thyroid Microtissue Model for Chemical Screening. Presented at Society of Toxicology annual meeting, Baltimore, MD, March 10 - 14, 2019. https://doi.org/10.23645/epacomptox.7848353
Impact/Purpose:
Poster to be presented at Society of Toxicology annual meeting in March 2019. The objective was to develop an in vitro organotypic culture model for evaluating disruption of thyroid hormone synthesis in the human thyroid gland. Inhibition of key molecular initiating events in the thyroid gland such as Thyroid Stimulating Hormone Receptor (TSHR), Thyroperoxidase (TPO), and the Sodium Iodide Symporter (NIS) lead to decreased serum thyroxine (T4) levels, resulting in adverse neurodevelopmental outcomes in mammals. An assay that evaluates the function of these targets in an integrated functional model is required to evaluate chemical hazards identified in high-throughput screening platforms.
Description:
Thyroid hormones (TH) are essential for regulating a number of diverse physiological processes required for normal growth, development, and metabolism. The US EPA Endocrine Disruptor Screening Program (EDSP) has identified several molecular thyroid targets relevant to hormone synthesis dynamics that include the TSH receptor (TSHR), Sodium/Iodide Symporter (NIS), Thyroperoxidase (TPO), Dual Oxidase (DUOX), Iodotyrosine Deiodinase (IYD), and Pendrin. High-throughput screening assays for TSHR, TPO, and NIS have been used to screen chemicals across the ToxCast/Tox21 chemical inventories to identify potential thyroid disrupting chemicals (TDCs). The uncertainty surrounding the specificity of hits identified in these screens, the relevance to human biology, and the quantitative potency relationship of molecular perturbation to decreased TH synthesis are notable data gaps in hazard identification for TDCs. The objective of this study was to develop a medium-throughput organotypic screening assay comprised of reconstructed human thyroid microtissues to quantitatively evaluate the disruptive effects of chemicals on TH production and secretion. Cells procured from qualified euthyroid donors were analyzed for retention of NK2 homeobox 1 (NKX2-1), Cytokeratin 7 (KRT7), and Thyroglobulin (TG) expression by high-content image analysis to verify enrichment of follicular epithelial cells. A direct comparison of two-dimensional (2D) and three-dimensional (3D) 96-well culture formats was employed to evaluate TG and TH (T3 and T4) secretion over the course of 20 days. The results of serial sampling in the 2D format revealed considerable loss of TG expression with no subsequent production of T3 or T4. In contrast, the 3D model continued to increase TG levels over time, with sustained output of T3 and T4. Inhibition of TH synthesis in an optimized 3D culture format was demonstrated with reference chemicals Methimazole, 6-Propyl-2-thiouracil, and Sodium Perchlorate. Overall, the 3D thyroid microtissue assay will prove to be a valuable resource for extending screening efforts currently underway in ToxCast/Tox21 and EDSP. This abstract does not necessarily reflect the policy of the US EPA.
URLs/Downloads:
DOI: Development of an In Vitro Human Thyroid Microtissue Model for Chemical Screening
2-22-19_DEISENROTH_SOT_THYROID OCM_POSTER_FINAL.PDF (PDF, NA pp, 2025.35 KB, about PDF)