Isolation of a normal human thyroid cell line: hormonal requirement for thyroglobulin regulation

Ex vivo model for elucidating the functional and structural differentiation of the embryonic mouse thyroid

Terminal thyroid gland differentiation - the last developmental step needed to enable thyroid hormone (T4) synthesis - involves profound structural and biochemical changes in the thyroid follicular cells (TFCs). We aimed to develop an ex vivo thyroid model of embryonic mouse thyroid that would replicate the in vivo TFC differentiation program. E13.5 thyroid explants were cultured ex vivo in chemically defined medium for 7 days. Immunostaining and qPCR of thyroid explants showed thyroglobulin production onset, follicle formation, and T4 synthesis onset in 1-, 3-, and 5-day-old cultures, respectively. Differentiation was maintained and follicular growth continued throughout the 7-day culture period. Pharmacological approaches to culture inhibition were performed successfully in the ex vivo thyroids. Our robust and well described ex vivo thyroid culture model replicates the sequence of thyroid differentiation to T4 synthesis seen in vivo. This model can be used to test the effects of pharmacological inhibitors on thyroid hormone production.

Human cancer cell lines: Experimental models for cancer cells in situ? For cancer stem cells?

Established human cancer cell lines are routinely used as experimental models for human cancers. Their validity for such use is analyzed and discussed, with particular focus on thyroid tumors. Although cell lines retain some properties of the cells of origin, from the points of view of their genetics, epigenetics and gene expression, they show clear differences in these properties compared to in vivo tumors. This can be explained by a prior selection of initiating cells and a Darwinian evolution in vitro. The properties of the cell lines are compared to those of the postulated cancer stem cells and their use as models in this regard are discussed. Furthermore, other proper and possible uses of the cell lines are discussed.

Directed differentiation of mouse embryonic stem cells into thyroid follicular cells

Elucidating the molecular mechanisms leading to the induction and specification of thyroid follicular cells is important for our understanding of thyroid development. To characterize the key events in this process, we previously established an experimental embryonic stem (ES) cell model system, which shows that wild-type mouse CCE ES cells can give rise to thyrocyte-like cells in vitro. We extend our analysis in this report by using a genetically manipulated ES cell line in which green fluorescent protein (GFP) cDNA is targeted to the TSH receptor (TSHR) gene, linking GFP expression to the transcription of the endogenous TSHR gene. The appearance of GFP-positive cells was dependent on the formation of embryoid bodies from undifferentiated ES cells and was greatly enhanced by TSH treatment during the first 2-4 d of differentiation. With the support of Matrigel, highly enriched ES cell-derived GFP-positive cells formed thyroid follicle-like clusters in a serum-free medium supplemented with TSH. Importantly, these clusters display the characteristics of thyroid follicular cells. Immunofluorescent studies confirmed the colocalization of TSHR with the Na+/I- symporter in the clusters and indicated that Na+/I- symporter was expressed exclusively in the plasma membrane. In addition, I- uptake activity was observed in these cells. Our results indicate that ES cells can be induced to differentiate into thyroid follicular cells, providing a powerful tool to study embryonic thyroid development and function.

Normal human thyroid cells from the ARAMIS line follow the general concept of growth or differentiation: a study with thyroglobulin as a marker

A cell line of functional normal human adult thyroid cells was isolated 3 years ago. This cell line was used as a model to study human thyroglobulin (hTgb) production quantified in 5% fetal calf serum Click-RPMI medium and in the presence of insulin and thyrotropin (two hormones [2H]) to get maximal hTgb production. In this paper we demonstrate that these cells (line ARAMIS) follow the general dualistic opposition between growth and differentiation. Thyroglobulin cell production in 2H-stimulated cells is dependent on cell density and is not constant with time of culture in growing and in quiescent cells. High serum levels required for cell proliferation antagonize thyroglobulin cell production. Furthermore, in the absence of cell proliferation, the longer the cells stay in the stationary phase in 2H-medium, the better they produce thyroglobulin with time. The longer the cells stay in the stationary phase in 1H (insulin) medium, the higher will be the total thyroglobulin production and the initial rate in thyroglobulin production after TSH addition. The longer the cells stay in the stationary phase in 1H (insulin) medium, the higher are cyclic adenosine monophosphate (cAMP) levels after thyrotropin (TSH) stimulation. This is observed both for initial rates and total production. Neither insulin nor cell-cell interactions occurring during the stationary phase modify basal cAMP levels. Altogether the data demonstrate that in cell culture conditions that exclude proliferation, a gain in TSH sensitivity appears versus time in insulin-stimulated quiescent normal human thyroid cells during their stationary phase. This improved differentiating status appears to be TSH- and cAMP-independent. It could be an insulin or insulin-like growth factor-1 (IGF-1)-dependent trophic effect promoting an increase in TSH-receptor number or sensitivity. But once again and as mentioned previously, we cannot exclude from the data that cell to cell interactions between silent and "informed" cells (in other words, autocrine phenomena) could result, with time, in the recruitment of silent resting cells, explaining the gain in TSH sensitivity.

Thyroglobulin: a specific serum marker for the management of thyroid carcinoma

Thyroglobulin measurements in tissue and serum play an integral role in the evaluation of patients who have thyroid cancer. Immunohistochemical detection of thyroglobulin in surgical specimens is useful in the differential diagnosis of tumors of unknown origin; however, the most important application of thyroglobulin measurement in clinical practice is in the postsurgical management of differentiated thyroid cancer. Serum thyroglobulin is a highly specific and sensitive tumor marker for detecting persistent or recurrent thyroid cancer and for monitoring clinical status. The reappearance of circulating thyroglobulin after total thyroid ablation is pathognomonic for the presence of tumor. The measurement of thyroglobulin in serum is challenging, however, and several analytical problems limit assay performance. Thyroglobulin autoantibody interference is a particularly significant concern that requires all thyroglobulin samples to be screened for their presence. No immunoassay is totally free from interference by thyroglobulin autoantibodies. Measurement of thyroglobulin mRNA to detect circulating tumor cells may help to overcome some of the limitations of current protein-detection methods; serum thyroglobulin will continue to remain the "gold standard." The complex functional features of thyroid carcinomas make sole reliance upon any one diagnostic technique, including thyroglobulin assessments, potentially misleading. Thyroglobulin measurements are a critical component of a multifaceted diagnostic approach to this disease.

Ideology Masquerading as Science: The Case of Endocrine Disrupter Screening Programmes

The global move to develop novel testing methods and strategies to identify suspected endocrine disrupting chemicals offers a unique opportunity to move away from traditional animal testing paradigms in this new area of regulatory concern. Regrettably, the programmes under development, both in the USA and internationally through the OECD, have thus far failed to consider in vitro and other non-animal test methods as more than “pre-screening” or “priority-setting” tools in a larger, animal-based testing strategy. Validation efforts to date have focused almost exclusively on the modification of existing animal tests to detect “endocrine effects”, with no demonstrable effort to promote international coordination or support for the development and validation of relevant non-animal test systems. The current orientation in these programmes reflects ideological, rather than scientific, imperatives, and undermines the commitments of both the US government and the OECD with respect to the Three Rs and the minimisation of animal testing.

Committing embryonic stem cells to differentiate into thyrocyte-like cells in vitro

The derivation of thyrocyte-like cells in culture is of importance in the basic study of early thyroid embryogenesis and the generation of an unlimited clinical source of thyrocytes for genetic manipulation and cell transplantation. We have established an experimental system, which shows that 6-d-old embryoid bodies (EBs) differentiated from mouse embryonic stem (ES) cells expressed a set of genes traditionally associated with thyroid cells. The genes analyzed included the thyroid transcription factor PAX8, the Na(+)/I(-) symporter, thyroperoxidase, thyroglobulin, and the TSH receptor (TSHR). Immunofluorescent analysis demonstrated the presence of TSHR-positive cells as outgrowths from 8-d-old EBs cultured on chamber slides. Accordingly, this area of cells also expressed PAX8 and another thyroid transcription factor TTF2. Of importance, TSH, the main regulator of the thyroid gland, was necessary to maintain the expression of PAX8 and TSHR genes during EB differentiation. Furthermore, thyroid-specific function, such as cAMP generation by TSH, was maintained in this model. Together, these results suggested that the developmental program associated with thyrocyte development is recapitulated in the ES/EB model system. The differentiation of mouse ES cells into thyrocyte-like cells provides a powerful model for the study of thyrocyte developmental diseases associated with this lineage and contributes to the development of thyroid hormone-secreting cell lines.