Temperature-sensitive regulation of epidermal morphogenesis and the expression of cornified envelope precursors by EGF and TGF alpha

Epidermis reconstructed on de-epidermized dermis was used to investigate the effects of growth factors and culture temperature on epidermal morphogenesis and the expression of cornified envelope precursors. Cultures grown at 33 degreesC or 37 degreesC in the absence or presence of transforming growth factor alpha (TGFalpha), keratinocyte growth factor (KGF), basic fibroblast growth factor (bFGF), or insulin-like growth factor (IGF) show a similar morphology to that of native epidermis. Loricrin and SPRR2 are expressed in the stratum granulosum and SPRR3 is absent. Cultures grown in epidermal growth factor (EGF)-supplemented medium at 37 degrees C have a normal morphology, whereas cultures grown at 33 degrees C have a disorganized basal layer, no stratum granulosum, and nuclei are present in the stratum corneum. Loricrin is absent, and SPRR2 and SPRR3 expression extend into the spinous layers. Irrespective of the culture condition used, involucrin is aberrantly expressed in all suprabasal layers. EGF stimulated keratinocyte proliferation and migration to a greater degree than TGFalpha. Epidermis reconstructed on fibroblast-populated collagen gels at 33 degrees C led to the same disturbances in keratinocyte differentiation as seen in cultures grown on de-epidermized dermis at 33 degrees C in the presence of EGF, whereas parallel cultures grown at 37 degrees C have a similar morphology to that of native epidermis.