Hydra regeneration from recombined ectodermal and endodermal tissue. I. Epibolic ectodermal spreading is driven by...

Area of Science:

• Developmental Biology
• Cell Biology
• Regenerative Medicine

Background:

• Epithelial sheet formation is fundamental for organismal development and regeneration.
• Understanding cell-cell interactions is key to deciphering developmental processes.

Purpose of the Study:

• To investigate cell-cell interactions and rearrangement during epithelial sheet formation in regenerating Hydra cell aggregates.
• To elucidate the mechanisms underlying ectodermal spreading and epithelial organization.

Main Methods:

• Separation of ectodermal and endodermal cell layers in Hydra magnipapillata using procaine treatment.
• Dissociation and reaggregation of cells to form ectodermal and endodermal aggregates.
• Recombination of aggregates, fluorescent dye-staining for cell movement analysis, and observation of regeneration.

Main Results:

• Recombined Hydra aggregates rapidly adhered, followed by ectodermal cell spreading over the endoderm, mimicking epiboly.
• Fluorescent dye studies revealed radial cell intercalation at the contact surface, driving aggregate growth and envelopment.
• A tryptic extract of hydra membrane fraction inhibited ectodermal spreading, suggesting a signaling factor.

Conclusions:

• Radial cell intercalation is critical for ectodermal spreading and establishing epithelial sheet organization in regenerating Hydra aggregates.
• Cell-cell contact and signaling at the surface likely activate this intercalation process.
• A membrane-bound factor may regulate the signaling mechanism involved in epithelial sheet formation.