In vitro pituitary and thyroid cell proliferation assays and their relevance as alternatives to animal testing

Abstract

Summary This study investigates the in vitro effect of eleven thyroid-active compounds known to affect pituitary and/or thyroid weights in vivo, using the proliferation of GH3 rat pituitary cells in the so-called "T-screen," and of FRTL-5 rat thyroid cells in a newly developed test denoted "TSH-screen" to gain insight into the relative value of these in vitro proliferation tests for an integrated testing strategy (ITS) for thyroid activity. Pituitary cell proliferation in the T-screen was stimulated by three out of eleven tested compounds, namely thyrotropin releasing hormone (TRH), triiodothyronine (T3) and thyroxine (T4). Of these three compounds, only T4 causes an increase in relative pituitary weight, and thus T4 was the only compound for which the effect in the in vitro assay correlated with a reported in vivo effect. As to the newly developed TSH-screen, two compounds had an effect, namely, thyroid-stimulating hormone (TSH) induced and T4 antagonized FRTL-5 cell proliferation. These effects correlated with in vivo changes induced by these compounds on thyroid weight. Altogether, the results indicate that most of the selected compounds affect pituitary and thyroid weights by modes of action different from a direct thyroid hormone receptor (THR) or TSH receptor (TSHR)-mediated effect, and point to the need for additional in vitro tests for an ITS. Additional analysis of the T-screen revealed a positive correlation between the THR-mediated effects of the tested compounds in vitro and their effects on relative heart weight in vivo, suggesting that the T-screen may directly predict this THR-mediated in vivo adverse effect.

Pesticide toxicogenomics across scales: in vitro transcriptome predicts mechanisms and outcomes of exposure in vivo

“…In the following we use the H, M, L abbreviations to state high, medium and low concentrations, respectively. The chosen concentrations are in or below the range of the doses tested in immortalized thyrocytes for ETU17 and other cell systems for CPF18. Since humans are usually co-exposed, we also treated the cells with the mixtures of ETU and CPF to evaluate possible additive/synergic effects.…”

Developmental toxicity of thyroid-active compounds in a zebrafish embryotoxicity test

“…the pathways involved in human thyroid development are conserved in the zebrafish and so are its tissue architecture, function and feedback regulation by the HPt axis, making it a promising model for the study of thyroid-active compounds (Bourque and Houvras, 2011;Jomaa et al, 2013;Raldúa and Babin, 2009). …”

“…Substances that are marketed or manufactured in quantities above 100 tons per annum are required to be tested for pre-natal developmental toxicity (OeCD 414) (ReACH, 2006). Based on data on chemical production from 1991 to 1994, the eU estimates that 2.6 million animals will be needed for all ReACH testing or a total of 9 million when offspring produced during reproductive and developmental toxicity test-weights used as endpoints in in vivo assays (Jomaa et al, 2013). While the effect of estrogen-mimicking compounds on cell proliferation in the in vitro e-screen was found to correlate with their effects on in vivo uterine weight (r 2 =0.85) , the effects of thyroid-active compounds on thyroid (tSHscreen) and pituitary (t-screen) cell proliferation was found to have poor correlation with their effects on the weight of these respective organs in vivo.…”

Simple and rapid in vitro assay for detecting human thyroid peroxidase disruption

“…While it is currently not possible to replicate thyroid histopathology in vitro, in a previous study we have searched for potential correlation between the effects of chemicals on pituitary and thyroid organ weights in vivo and the effects of the same set of chemicals on cellular proliferation in vitro using pituitary and thyroid model cell lines. To this end, 11 thyroid-active compounds were tested and it was concluded that in vitro cellular proliferation alone correlates poorly with pituitary and thyroid organ weight change in vivo (Jomaa et al, 2013). This is likely due to the complex multi-organ paradigm that the thyroid system represents (Jomaa, 2014).…”