Morphological and Biochemical Characterization of the Cornified Envelopes from Human Epidermal Keratinocytes of Different Origin

The formation of a cornified envelope (CE) is a major event in the terminal differentiation of epidermal cells. Nomarski contrast microscopy of the envelopes purified from different sources reveals the existence of two major, but morphologically distinct classes: the very irregularily shaped fragile type CE_f. Psoriatic scales from different patients show both types in varying proportions. Tape stripping of normal epidermis reveals that type CE_f is present in the lowermost layers of the stratum conreum and type CE_r is present in the upper layers, indicating that the two types represent a different stage of maturation. Cyanogen bromide peptide mapping of electrophoretically purified envelopes reveals striking differences between cultured keratinocytes, normal epidermis, and psoriatic scales but also slight interindividual variations. This variability supports the view that the molecular CE composition is not strictly determined. On the other hand, no difference could be detected in the peptide maps of CE_f and CE_r obtained after tape stripping from the same healthy volunteer indicating that CE maturation within the stratum corneum does not involve the provision of qualitatively new proteins.