Markus Stucker, Michael Licht and H Michael Heise
Background: During the final stage of differentiation of cornified squamous epithelia like the human skin epidermis, anucleated corneocytes are formed. Formation of the horny layer and its ongoing desquamation are fundamental processes leading to the formation of an efficient epidermal barrier. Materials and methods: For a better understanding of the desquamation process, the role of corneocyte surface ultra-structure has been investigated using a special preparation technique for scanning electron microscopy (SEM). Human morphologically different corneocytes from the stratum corneum of the fingertip, the thenar eminence (thick skin), and the wrist below the carpus (thin skin) of normal and diabetic subjects were obtained by adhesive tape stripping. Results: The inside surface structure of corneocytes from thick skin shows prominent nubs, which are broader and more extended than those of thin skin. Towards their outside, corneocytes were flat with cavities as indentations of the nubs from neighboured cells providing clues on the mechanical strength of the ‘intercellular stickiness’. As the size of thin skin corneocytes for diabetic subjects was also studied, it was found that their area was slightly nonlinearly dependent on age. Conclusion: Accordingly to a reduced proliferation and differentiation rate, as postulated for diabetic persons, differences in size were as expected but statistically not significant, compared with corneocytes under normal homeostasis conditions. For discussion is a model, for which the interwoven cellular connectivity provides additional mechanical strength for the stratum corneum in thick skin.