Defined Conditions Control the Morphological Dualism of Rat Primitive Extraembryonic Endoderm Stem Cells

Area of Science:

• Developmental Biology
• Stem Cell Biology
• Cellular Plasticity

Background:

• Rat primitive extraembryonic endoderm (pXEN) stem cells maintain early extraembryonic endoderm (ExEn) features in vitro.
• Current methods require undefined serum factors and result in a hybrid mesenchymal-epithelial phenotype.

Purpose of the Study:

• To establish chemically defined conditions for the permanent self-renewal of pXEN stem cells.
• To investigate the signaling pathways governing pXEN proliferation and morphotype plasticity.

Main Methods:

• Utilized two distinct chemically defined culture conditions.
• Manipulated leukemia inhibitory factor (Lif) and Chir99021 (a β-catenin stabilizer).
• Analyzed cell proliferation, morphology, marker expression, and organoid formation.

Main Results:

• Achieved permanent self-renewal of pXEN stem cells in both mesenchymal and epithelial morphotypes.
• Demonstrated interconvertibility and equipotency of the morphotypes.
• Identified essential roles for Lif-type Gp130/Stat3 and noncanonical Wnt signaling in proliferation.
• Showcased β-catenin requirement for epithelial cell proliferation and morphology.

Conclusions:

• Established a robust platform for studying ExEn proliferation and plasticity.
• Revealed the dual mesenchymal-epithelial nature of early ExEn in vivo.
• Highlighted the critical roles of Lif-type and Wnt signaling in ExEn self-renewal.