No abstract

Background Epiboly represents the process by which keratinocytes migrate to envelop a surface. We have been investigating a living bilayered skin construct (BSC) that is used in the treatment of lower extremity wounds due to venous insufficiency and diabetes. The construct demonstrates epiboly after injury and incubation in vitro, and this model may be useful for studying epidermal migration and the process of skin maturation. Punch biopsies of the construct in vitro were cultured and immunostained for specific keratins at baseline, and at 24–72 hours. For comparison, skin biopsy specimens from human chronic venous ulcers and acute healing wounds were similarly processed. We found that K1 and K10 were fully expressed in the epidermis of the fully epibolized surface on BSC. K1 was also present in the migrating edge of specimens, while K10 was not detectable. K16 and K6 were evident in normal skin and the epibolized area of the construct; K6 expression was very prominent in the migrating edge. Importantly, K17 was distinctly limited to the epibolized surface and the migrating edge, and its expression was very similar to that observed in healing human wounds. In conclusion, differential expression of keratins in this epiboly model closely reflects in vivo studies and supports keratin specificity in the processes of migration and differentiation of new epidermis. Therefore, these findings provide further and important validity for the study of epithelialization and the hope of developing prognostic markers for venous ulcer healing.

Growing evidence demonstrates that various nevoid proliferations such as keratinocytic epidermal nevi and nevus sebaceous result from somatic mosaicism. Many of the mutations identified have been within the RAF/RAS/MAPK pathway, hence supporting the previously introduced term "mosaic RASopathy" for these nevi. In this issue, Kinsler et al. were among the first to characterize certain pigmented melanocytic nevi that may also fit this paradigm. To better frame these findings, we provide a summary of the analogous genotypic profiles for epidermal and melanocytic nevi from recent studies.