Thyroid organoid formation in simulated microgravity: Influence of keratinocyte growth factor

The generation of artificial human thyroid tissues in suspension (low-shear environment, present in simulated microgravity [MG] and generated by a rot ary cell culture system [RCCS]), was enhanced by increasing medium kinemati c viscosity with a (3% v/v) suspension of extracellular matrix (basement me mbrane extract [BME]) in serum-free medium to generate artificial human thy roid organoids. Recombinant human keratinocyte growth factor (KGF, 7 ng/mL) facilitated human thyrocyte aggregation and three-dimensional (3-D) differ entiation. There was an MG-associated decrease in extractable DNA that was reversed after addition of keratinocyte growth factor (KGF). In simulated M G, the increase in extractable DNA after KGF addition was up to 170% over n on-KGF control cultures. In contrast, monolayer cultures in unit gravity sh owed a maximum DNA increase of 39% after KGF addition. Morphologically, dif ferentiated thyroid neofollicles displayed polarization and were located in close proximity after 2 weeks of culture. Immunogold labeling with antibod y to human thyroglobulin (Tg) revealed staining of follicular lumina and se cretory vesicles, and a time-dependent increase in human Tg was detected in the culture media. Culture under simulated MG thus allowed direct visualiz ation of KGF-facilitated thyrocyte/extracellular matrix interaction. Such a rtificial human thyroid organoids-generated in MG and in the presence of KG F-structurally resembled natural thyroid tissue. The above findings may hav e implications for autoimmune thyroid disease where KGF (if, for example, s ecreted locally by intraepithelial gamma delta T cells among other cells) m ay contribute to thyroid cell growth.