Evaluating the maturity of cornified envelopes: Hirao has published a review on the signifi cance of cornified envelopes in barrier function of the stratum corneum. Cornified envelopes (CE), which are rigid and insoluble structures surrounding the corneocytes, are assembled by crosslinking of several precursor proteins by transglutaminases. The CE provide the basis for barrier function of the stratum corneum.
Hirao recently established a novel double staining method to evaluate the level of CE maturity in stratum corneum samples collected by non-invasive tape stripping, in order to examine the relationship between CE maturation and barrier function. This method is based on both loss of involucrin antigenicity and acquisition of hydrophobicity during CE maturation.
Hirao applied the method to various kinds of skin and found that immature CE were abundant not only in involved areas inflammatory dermatoses, such as psoriasis and atopic dermatitis, but also in the face of healthy subjects, and were associated with impaired barrier function of the stratum corneum. Ex vivo incubation of the outermost stratum comeum of the face in a humidifi ed environment resulted in conversion of immature CE to mature CE, mediated by transglutaminases. This maturation process was inhibited under low humidity conditions and recovered on application of moisturizers to stratum corneum samples prior to the incubation.
