Cytokine Release and Focal Adhesion Proteins in Normal Thyroid Cells Cultured on the Random Positioning Machine

Spaceflight impacts on the function of the thyroid gland in vivo. In vitro normal and malignant thyrocytes assemble in part to multicellular spheroids (MCS) after exposure to the random positioning machine (RPM), while a number of cells remain adherent (AD). We aim to elucidate possible differences between AD and MCS cells compared to 1g-controls of normal human thyroid cells.

Cells of the human follicular epithelial thyroid cell line Nthy-ori 3-1 were incubated for up to 72 h on the RPM. Afterwards, they were investigated by phase-contrast microscopy, quantitative real-time PCR and by determination of cytokines released in their supernatants.

A significant up-regulation of IL6, IL8 and CCL2 gene expression was found after a 4h RPM-exposure, when the whole population was still growing adherently. MCS and AD cells were detected after 24 h on the RPM. At this time, a significantly reduced gene expression in MCS compared to 1g-controls was visible for IL6, IL8, FN1, ITGB1, LAMA1, CCL2, and TLN1. After a 72 h RPM-exposure, IL-6, IL-8, and TIMP-1 secretion rates were increased significantly.

Normal thyrocytes form MCS within 24 h. Cytokines seem to be involved in the initiation of MCS formation via focal adhesion proteins.