Generation of Adult Stem Cell Derived Organoid Cultures From Thyroid Follicular Cells

Abstract The thyroid is essential for maintaining systemic homeostasis by regulating thyroid hormone concentrations in the bloodstream. Due to the limited number of representative model systems, there is limited understanding of fundamental thyroid biology as well as thyroid carcinogenesis. To fill the caveats in the understanding of thyroid cell biology, we aimed to develop an adult stem cell-derived three-dimensional (3D) organoid culture system using murine and human thyroid follicular cells (TFCs). We have succeeded to grow such an organoid culture system that harbours the complete machinery of hormone production visualised by the presence of colloid in the lumen and essential transporters and enzymes in a polarised cell layer. Both the established murine as human thyroid organoids express canonical thyroid markers PAX8 and NKX2.1/TTF1. Moreover, the thyroid hormone precursor thyroglobulin is expressed in both cultures to similar levels as in tissue. Extensive characterisation furthermore identifies known and new biological insights in TFC subclassification, subcellular organisation and hormone production using state-of-the art techniques like single cell RNA sequencing, transmission electron microscopy and genome editing. These 3D in vitro cultures allow for a variety of thyroid-related studies including the progression of wild type cells towards cancer. Additionally, due to the success of generating patient-specific tumour organoids of primary differentiated thyroid carcinoma and metastasis, insights in drug resistance and metastases can be identified. In short, this newly developed organoid culture of murine and human wild type TFCs as well as tumour tissue opens up an extensive area of research that will help understand the drivers for growth and development of thyroid (cancer) cells and enable studies upon drug responsiveness.