Introduction: Therapy of atopic dermatitis encloses use of medicated and nonmedicated preparations. Results of clinical and biophysical procedures indirectly describe the condition of the impaired skin barrier (SB). Direct evaluation of SB integrity is only possible by electron microscopical visualization, e.g. intercellular lipid lamellae (ICLL) organization of the stratum corneum. Method: SB integrity was measured by morphometric analysis of ICLL in healthy and atopic skin and after a 15-day treatment (plus 7-day follow-up) of atopic skin with a glycerin preparation. Results: Significant treatment effect was shown by the restoration of the ICLL. Conclusions: The study reveals that morphometric analysis of ICLL organization is suitable to differentiate between healthy and diseased skin and to semiquantitatively determine the effect of a nonmedicated glycerin formulation. Limitation: Small treatment cohort.

Background/Aims: Dry skin, or xerosis, is a common condition and a key feature of skin diseases like atopic dermatitis (AD) and ichthyosis vulgaris. Foot xerosis may exist without underlying disease and could be related to very mild forms of AD or ichthyosis vulgaris. The synthesis of important skin lipids (cholesterol, free fatty acids and ceramides) is reduced in xerosis and AD, and reduced lipid synthesis is responsible for a lack of lipids and enzymes in the skin barrier. This slows down reorganisation of the lipid lamellae in the stratum corneum (SC). Methods: Skin barrier integrity was measured by morphometric analysis of the lipid lamellae in the SC after 4 weeks of treatment with a foam cream (active agent vs. placebo). Results: Significant treatment effects were shown after 2 and 4 weeks by an increasing amount of intercellular lipids in the SC. Conclusion: This study shows that a quick reorganisation of the SC lipids initiates a good restoration of the whole skin barrier after 4 weeks of treatment with a foam cream.

RNA-protein interactions play critical roles in diverse cellular functions and their perturbations may contribute to human disease. A synonymous single nucleotide polymorphism (SNP) in the coding sequence of corneodesmosin (CDSN), a gene essential for normal epidermal differentiation whose mutation leads to peeling skin syndrome, has long been linked to psoriasis in diverse ethnic groups. How the psoriasis-associated CDSN variant might contribute to disease pathogenesis, however, is unclear. To address this, we used new methodology, which we term RNA-Protein Interaction Detection (RaPID), to search for differential protein binding to CDSN mRNA. RaPID uses a RNA-targeted biotin ligase to tag proteins bound to RNA sequences of interest followed by streptavidin pull-down and mass spectrometry (RaPID-MS). RaPID-MS demonstrated that the APOL4 protein strongly bound normal CDSN mRNA but not the disease-associated variant. APOL4 is known to affect lipid transport and has not been previously implicated in RNA binding nor epidermal differentiation, yet displayed >40-fold increased expression during epidermal differentiation in parallel to CDSN induction. Enhancing expression of APOL4 in differentiating keratinocytes (KCS) markedly stabilized CDSN transcripts, leading to 75-fold increase in CDSN mRNA. In contrast, APOL4 gene knockout in normal KCS using CRISPR-Cas9 down-regulated CDSN transcript levels up to 5-fold. These data demonstrate that APOL4 normally binds CDSN mRNA to control its expression and, consistent with CDSN dysregulation observed in human psoriasis, implicate dysregulation of APOL4's control of CDSN in its pathogenesis. They also provide support for future studies of APOL4 in the coordinate regulation of terminal differentiation with lipid barrier formation. Finally, these data demonstrate the capacity of RNA proteomics approaches in living cells to characterize human disease-associated SNPs.

Models of human epidermis are widely employed for basic studies of skin biology and in the development of drugs and cosmetics, but epidermal equivalents prepared with passaged keratinocytes are typically only 10-20 mm thick, whereas full-thickness human epidermis can be up to 100 mm thick. Our established mathematical model of epidermal homeostasis predicted that the undulatory pattern of the papillary layer beneath the epidermis is a key determinant of epidermal thickness. Here, aiming to develop a more physiologically realistic epidermal model, we tested this prediction by seeding human keratinocytes on polyester textiles with various fiber-structural patterns in culture dishes exposed to air. Textile substrate with fiber thickness and inter-fiber distance similar to those of human papillary layer proved most effective, affording a three-dimensional epidermal-equivalent model with thick stratum corneum and intercellular lamellar lipid structure. Cells located around fibers of the textile were proliferating, as indicated by BrdU staining and expression of melanoma-associated chondroitin sulfate proteoglycan. Fillaggrin, loricrin, claudin 1 and ZO-1 were all appropriately expressed. Silencing of the transcriptional coactivator YAP (Yes-associated protein) with siRNA disturbed construction of the three-dimensional structure. This work provides simple methodology for production of high-quality, low-cost epidermal-equivalent models using passaged keratinocytes.