Characterization of a human thyroid microtissue model for testing thyroid disrupting chemicals.

Area of Science:

• Endocrinology and Toxicology
• In vitro modeling of human thyroid function

Background:

• Thyroid hormone (T4) synthesis disruption causes human developmental and cognitive disorders.
• Existing in vitro models lack human cellular architecture and T4 production capabilities.
• Species differences necessitate human-based screening systems for thyroid disrupting chemicals (TDCs).

Purpose of the Study:

• To develop and characterize a human-based in vitro model for T4 synthesis and screening TDCs.
• To assess the feasibility of using cryopreserved primary human thyrocytes in 3D microtissues.
• To evaluate the model's ability to recapitulate thyroid cellular architecture and T4 production.

Main Methods:

• Primary human thyrocytes cryopreserved at passage one (p'1) were cultured in 3D microtissues on Matrigel®.
• Thyroid stimulating hormone (TSH) was used to stimulate thyrocytes and induce follicular structure formation.
• Thyroglobulin (TG) and T4 production were measured, and inhibition by prototype TPO inhibitors was assessed.

Main Results:

• Thyrocytes formed stable 3D microtissues with >80% EpCAM+ cells within 4-5 days.
• Optimal TG and T4 production occurred with specific CD90+ cell proportions, seeding densities, and TSH concentrations.
• IC50 values for TPO inhibitors (6-propyl-2-thiouracil and methimazole) were determined in the microtissue model.

Conclusions:

• Cryopreserved p'1 human thyrocytes in 3D microtissues provide a robust in vitro model for thyroid function.
• This model effectively recapitulates thyroid cellular architecture and T4 production.
• The system shows promise for prioritizing potential TDCs acting directly on the thyroid gland.