Epithelial differentiation in the absence of extracellular matrix

Abstract

To investigate the regulation of epithelial differentiation, normal human epidermal keratinocytes were cultured floating on the surface of culture medium without attachment to a solid substrate. Keratinocytes spread out on the surface of the medium, proliferated and differentiated either into several flat lacy sheets 1 to 3 cells thick (on medium containing 0.15 mM calcium) or formed one single aggregate of cells from 5 to 15 cells in thickness on medium containing 1.15 mM calcium. The cell aggregates demonstrated a pattern of ordered epithelial differentiation. Levels of progressive differentiation resembling the structure of normal human epidermis were identified by light microscopy, immunohistochemistry, and electron microscopy. Differentiation proceeded from cells at the air side toward cells at the medium side with basal appearing cells on the air side and keratinocytes expressing filaggrin and involucrin on the side toward the medium. These results demonstrate that organized epithelial differentiation can occur in the absence of extracellular matrix. In contrast with other air-liquid interface cultures, epithelial differentiation in the absence of extracellular matrix progresses from air towards medium.

Differentiation of epithelial cells on microporous membranes

“…These observations indicated that (a) an extracellular matrix material or other cell types are not necessary to initiate basal lamina deposition, and (b) the planar nature of the basal plasma membrane might be critical to basal lamina formation. The importance of microporosity and the lack of importance of an extracellular matrix has also been substantiated with NHEK cells that develop a basal lamina-like structure when grown in suspension and at the air-liquid interface in vitro (Krejci et al, 1991). Thus, data suggest that microporosity, and not other substrate conditions, might be critical to the expression of a basal lamina.…”