Abstract
ABSTRACTOrganization of epithelial cells during follicular lumen formation is crucial for thyroid morphogenesis and function of the thyroid gland; however, the molecular mechanisms underlying this are poorly understood. To investigate this process, we established three-dimensional (3D) epithelial culture model systems using Fischer rat thyroid (FRT) cells or murine primary thyrocytes that developed polarized spherical structures with a central lumen, mimicking thyroid follicles. Using microarray-based differential expression analysis of FRT cells grown under 2D or 3D conditions, followed by RNA-mediated interference (RNAi) and morphogenetic analysis, we identified a key role for the thyroid transcription factor Pax8 and its target cadherin-16 (Cdh16) in the generation of polarized follicle-like structures. Silencing Pax8 expression inhibited the acquisition of apical–basal membrane polarity and impaired lumen formation. Both laminin and β1-integrin (Itgb1) expression was reduced, and cell cytoskeleton polarized distribution was altered. Silencing Cdh16 expression also led to the formation of defective structures characterized by very low laminin expression at the follicle–matrix interface, downregulation of Itgb1, and unpolarized distribution of cell cytoskeleton. Our results demonstrate that Pax8 controls apical–basal follicular polarization and follicle formation through Cdh16.
Highlights
The thyroid follicle is the structural and functional unit of the thyroid gland and consists of a single layer of follicular cells enclosing a central lumen where thyroid hormones are synthesized and stored
Organization of epithelial cells during follicular lumen formation is crucial for thyroid morphogenesis and function of the thyroid gland; the molecular mechanisms underlying this are poorly understood
Using microarray-based differential expression analysis of Fischer rat thyroid (FRT) cells grown under 2D or 3D conditions followed by RNA-mediated interference (RNAi) and morphogenetic analysis, we identified a key role for the thyroid transcription factor Pax8 and its target Cadherin-16 (Cdh16) in the generation of polarized follicle-like structures
Summary
The thyroid follicle is the structural and functional unit of the thyroid gland and consists of a single layer of follicular cells enclosing a central lumen where thyroid hormones are synthesized and stored. More refined organotypic 3D epithelial cell cultures have been developed using gels rich in ECM components, allowing the organization of epithelial cells into structures similar to those of the organs from which they derive. Cell lines such as MDCK, of renal origin, intestinal Caco-2 and breast MCF-10A, are regularly cultured embedded in a reconstituted basement membrane (MatrigelTM), where they generate fully polarized cysts and acini (Debnath et al, 2003; Ivanov et al, 2008; O'Brien et al, 2001), providing useful in vitro cell models to explore mechanisms associated with essential pathways of epithelial morphogenesis. While FRT cells have been extensively used in studies investigating polarized protein traffic (Imjeti et al, 2011; Lipardi et al, 2002; Zurzolo et al, 1992), their ability to form polarized follicles in 3D Matrigel is unknown
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
