Methimazole inhibits FRTL5 thyroid cell proliferation by inducing S-phase arrest of the cell cycle.

Abstract

Previous studies, using tritiated thymidine uptake assays, had indicated a nil or stimulatory effect of methimazole (MMI) on thyroid cell proliferation. Whilst examining cell cycle kinetics of FRTL5 thyrocytes, we observed an inhibitory effect of MMI on thyroid cell proliferation. To further examine this observation, FRTL5 cells whilst in log phase proliferation were exposed to media containing either 6H or MMI in 6H. Cell number and cell cycle kinetics were examined using flow cytometric DNA analysis every 24 hrs for 96 hrs. We found that MMI inhibited cell proliferation (as assessed by cell number) throughout the experimental period. Cell cycle analysis revealed a persistent arrest of cells in S phase. Concomitantly, there was a fall in the proportion of cells in both G0G1 and G2M phases, in keeping with cell cycle arrest in S phase. Taken in isolation, the finding of a high proportion of cells in S phase would suggest stimulation of cell proliferation, consistent with the findings of previous studies which used tritiated thymidine uptake assays to assess cell proliferation. However, the absence of a concomitant increase in total cell number renders this argument invalid and argues for a specific effect of MMI on the cell cycle. This study demonstrates a hitherto unrecognised inhibitory action of MMI on FRTL5 thyroid cell proliferation which has implications in understanding the broader effects of MMI on thyroid cell physiology. Additionally, this study highlights the dangers of using tritiated thymidine uptake measures as the sole indicator of mitogenic activity.

Differentiation of murine embryonic stem cells to thyrocytes requires insulin and insulin-like growth factor-1

“…We then added insulin and IGF-1 alone or in combination to the cultures in an attempt to induce the maturation of thyrocytes. Some cells were cultured in the presence of 6H medium, which promotes growth in FRTL-5 cells [13]. As shown in Figure 2E, the expression of NIS, TSHR , GFP, Foxa2 and Sox17 can be detected after a total of 11 days of differentiation.…”

SOX2 Activation Using CRISPR/dCas9 Promotes Wound Healing in Corneal Endothelial Cells

“…The G0/G1 phase is a resting phase wherein cells exit the cycle and do not proliferate [25]. During S-phase, DNA is replicated in proliferating cells [26]. Although the cell cycle of corneal endothelium in vivo stops at the G0/G1 phase [3], the overexpression of SOX2 may cause the cell cycle to progress.…”

Protective effect of maternal vitamin E supplementation on phenytoin-induced teratogenicity in rat pups

“…[24] Next morning each female rat was examined for any sign of mating in the form of blood stained vagina or a vaginal plug. [25,26] The presence of any sign of mating is considered as day zero of pregnancy. Absence of any apparent sign of mating led to vaginal wash which was obtained on glass slide and observed under microscope for presence of spermatozoa.…”

“…After one week, the pups were processed through 95% ethanol and acetone then placed in 4% KOH for a period of 1-2 weeks for clearing. [25] After clearing, they were bulk stained using 0.001% alizarin red in 1% KOH. [28] This technique clearly demonstrated the ossified bone while the unossified bone remained unstained.…”