Citation:

Hopperstad, K., T. Truschel, T. Wahlicht, W. Stewart, A. Eicher, T. May, AND C. Deisenroth. Characterization of Novel Human Immortalized Thyroid Follicular Epithelial Cell Lines. Applied In Vitro Toxicology. Mary Ann Liebert, Inc., Larchmont, NY, 7(2):39-49, (2021). https://doi.org/10.1089/aivt.2020.0027

Impact/Purpose:

Tiered testing strategies are used to evaluate chemical safety in an efficient, risk-based context. These strategies typically use higher throughput approaches to prioritize chemicals for subsequent testing and to screen chemicals for potential hazards. There is a continuing need to develop, demonstrate, and apply emerging technologies to provide actionable information to support tiered decision making. Our group has previously developed a 3D microtissue model of the human thyroid capable of evaluating the effects of potential thyroid disrupting chemicals prioritized by high-throughout assays in a more biologically relevant culture model. The objective of this study was to develop surrogate cell lines for the 3D model that could be a cost effective and reproducible alternative to primary cells derived directly from tissue. The results identified a human thyroid cell line exhibiting many morphological and functional features of primary thyrocytes and may be a valued addition for in vitro disease modeling and toxicity testing across the research community.

Description:

Introduction: Investigation of normal human thyroid function using in vitro culture systems is dependent on cells that recapitulate physiology of differentiated thyrocytes. Primary thyrocytes retain features of the native organ but have limited life span in culture. Immortalized thyrocytes offer an alternative if challenges maintaining phenotypic stability can be overcome to retain functional features of primary cells. Materials and Methods: CI-SCREEN immortalization technology was applied to normal human thyroid tissue to generate four cell line variants. The lines were characterized for transgene integration, biomarker expression, genomic stability, and proliferation rates. Thyroid stimulating hormone (TSH)-dependent morphology, thyroglobulin (TG) production, thyroxine (T4) hormone synthesis, and viability were assessed using conventional two-dimensional (2D) monolayer and three-dimensional (3D) microtissue culture formats in human thyrocyte epithelial cell (huThyrEC) or h7H medium. Results: Despite differential transgene profiles, the lines had similar biomarker expression patterns and proliferation rates. In 2D culture, there was no T4 synthesis or changes in viability, but TSH-dependent TG production was more significant for several lines in h7H than huThyrEC medium. Comparatively, in 3D microtissues, TSH-dependent TG induction was greater for cell lines in h7H medium. Synthesis of T4 in one cell line was higher than background with TSH exposure, but not significantly different than control. Discussion: Immortalization of primary human thyrocytes yielded transgenic lines of epithelial origin. When evaluated in 2D or 3D culture formats, h7H medium supported TG production to a greater magnitude than huThyrEC medium. One cell line cultured in 3D microtissue format marginally recapitulated T4 synthesis under continuous TSH exposure. Conclusion: Select human thyroid cell lines exhibited morphological and functional features of primary thyrocytes, and are a novel resource for in vitro disease modeling and toxicity testing, which will enable reproducible culture models more representative of normal human thyroid function.

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