Endocrine Abstracts

Background: Thyroid hormones are essential for normal development and metabolism. Their synthesis requires a normal function of thyroid follicular cells and adequate nutritional intake of iodine. Immortalized thyroid cell lines are widely used to study thyroid physiology and pathology. The best characterized and most widely used ones include the FRTL5 rat thyroid cell line and a derivative thereof, the PCCL3 cell line. A permanent human thyroid cell line is currently lacking. A recent report described a cell line obtained from human thyroid cells designated as Cl-huThyrEC.

Materials and Methods: Four clones of Cl-huThyrEC cells were obtained and cultured in the presence of thyroid stimulating hormone (TSH). The expression of key genes defining the thyroid follicular cell phenotype was determined by reverse-transcription PCR (RT-PCR) in FRTL5, PCCL3 and Cl-huThyrEC cells. The latter were cultured as monolayers and as organoids in Matrigel. Iodide uptake, which is essential for thyroid hormone synthesis, was measured and compared among cell lines.

Results: Gene expression analysis reveals that Cl-huThyrEC cells express the thyroid-restricted transcription factors (PAX8, NKX2.1, FOXE1), the TSH receptor (TSHR), and thyroglobulin (TG), but not other genes that are essential for thyroid follicular cell function such as the sodium-iodide symporter (NIS), thyroid peroxidase (TPO), and pendrin (SLC26A4). Importantly, Cl-huThyrEC cells are unable to concentrate iodine, a result that is in line with the absence of NIS gene expression.

Conclusion: Despite expression of certain key genes limited or restricted to thyroid follicular cells, Cl-huThyrEC cells lack some of the essential characteristics of thyroid follicular cells, in particular NIS. This limits their value for studies focusing on thyroid cell function.