Background: The umbilical cord (UC) is composed of connective tissue called Wharton Jelly, covered by a simple epithelium believed to derive from amniotic membrane epithelium. In previous studies, we observed that the umbilical cord epithelium (UCE) in situ displayed stratified epithelial structures, in some areas that expressed cytokeratins and differentiation markers as characteristic of keratinocytes under airlifted condition in vitro, UCE cells grown on collagen gel displayed more keratinocytes characteristics.
Objective: To study the ability of UCE cells to undergo terminal differentiation when grown in the most proper environment.
Methods: UCE cells were seeded onto the surface of a fibroblast-populated collagen gel then grafted onto the back of nude mice and examined using immunohistochemical techniques and by transmission electron microscope (TEM).
Results: Post-grafted UCE cells formed a stratified epithelial structure similar to that formed by keratinocytes. Although immunohistochemical staining of UCE cells in skin grafts showed a similar pattern to that seen with the keratinocyte controls, UCE cells maintained many of their own intrinsic characteristics, such as stronger expression of mucous membrane cytokeratins and expression of simple epithelial cytokeratin. Notably, with longer transplant periods, expression of keratinocyte characteristics in UCE cells increased while expression of simple epithelial properties decreased. We observed formation of a complete basement membrane, which had not been achieved using an in vitro model.
Conclusions: Grafted UCE cells in an animal model maintain their own intrinsic characteristics, but display the stratified morphogenesis, terminal differentiation and ultrastructures similar to those seen in keratinocytes.