Diversity of desmosomal proteins in regenerating epidermis: immunohistochemical study using a human skin organ culture model.

We recently established a skin organ culture model for epithelial healing by creating a central defect in freshly excised human skin specimens and keeping them in culture for up to 7 days, either untreated or with transplantation of allogenic or autologous keratinocytes. In this study the molecular diversity of cell-cell junction proteins in the regenerating epidermis was analysed immunohistochemically using a broad spectrum of monoclonal antibodies against glycoproteins (cadherins) and plaque proteins of desmosomes. At all stages studied the entire set of desmosomal cadherins [desmogleins (Dsg) 1-3 and desmocollins (Dsc) 1-3] was detected, with Dsg3, Dsc2 and Dsc3 being the most prominent. In the disordered neoepithelium at day 3 (after transplantation) some desmosomal cadherins appeared in their respective stratum compartments. In regenerating epidermis on day 7, which exhibited a more ordered stratification and a compact horny layer, stratification-related patterns of desmosomal cadherins were more pronounced. However, some immaturity of the day-7 neoepidermis was reflected by relatively low levels of the maturation-associated Dsgl and Dsc1 and a strong basal layer expression of Dsg2 which is sparse in normal epidermis. Desmosomal plaque proteins showed expression patterns similar to those in normal healthy epidermis. The adherens junction-related E-cadherin was also detected. Dendritic cells (melanocytes, Langerhans cells) were mainly present at the wound margins. In conclusion, this study demonstrated partial but not complete epidermal maturation and junction development during regeneration up to day 7. This model should also be useful in future studies to evaluate the effects of growth hormones to be used in therapeutic trials on chronic leg ulcers.