Comparison of suction blistering and tape stripping for analysis of epidermal genes, proteins and lipids.

Analysis of epidermal genes, proteins and lipids is important in the research and diagnosis of skin diseases. Although punch biopsy is the first-choice technique for the skin sampling, it is unnecessarily invasive for obtaining a sample just for the epidermal analysis. Here we compare two less invasive methods, suction blistering (SB) and tape stripping (TS), for the analysis of selected epidermal genes (quantitative real-time reverse transcription PCR, qRT-PCR), proteins (western blotting, WB), and lipids in ten healthy volunteers. TS provided significantly less material than SB and no viable epidermal layers could be obtained according to the reflectance confocal microscopy. Consistently, only the SC protein filaggrin and housekeeping GAPDH together with FLG and RPL13A mRNA were detected by TS. In the SB samples, WB and qRT-PCR could easily detect all the selected proteins (claudin-1, occludin, filaggrin, laminin and GAPDH) and genes (CLDN1, OCLN, FLG, LAMA3 and RPL13A), respectively. A single SB sample further provided enough of material for immunohistochemistry and lipid analyses, which was not feasible with the TS samples. Immunohistochemistry of the SB samples showed intact epidermal structure and a characteristic expression of claudin-1. Infrared spectroscopy showed well-ordered lipids with both orthorhombic and hexagonal packing and high-performance thin layer chromatography confirmed all lipid classes (including ceramide subclasses) in correct proportions. Taken together, SB represents a reliable sampling technique that can be utilized for multipurpose epidermal analyses in various studies.

The barrier function of organotypic non-melanoma skin cancer models.

Non-melanoma skin cancer (NMSC) is the most frequent human cancer with continuously rising incidences worldwide. Herein, we investigated the molecular basis for the impaired skin barrier function of organotypic NMSC models. We unraveled disturbed epidermal differentiation by reflectance confocal microscopy and histopathological evaluation. While the presence of claudin-4 and occludin were distinctly reduced, zonula occludens protein-1 was more wide-spread, and claudin-1 was heterogeneously distributed within the NMSC models compared with normal reconstructed human skin. Moreover, the cancer altered stratum corneum lipid packing and profile with decreased cholesterol content, increased phospholipid amount, and altered ceramide subclasses. These alterations contributed to increased surface pH and to 1.5 to 2.6-fold enhanced caffeine permeability of the NMSC models. Three topical applications of ingenol mebutate gel (0.015%) caused abundant epidermal cell necrosis, decreased Ki-67 indices, and increased lactate dehydrogenase activity. Taken together, our study provides new biological insights into the microenvironment of organotypic NMSC models, improves the understanding of the disease model by revealing causes for impaired skin barrier function in NMSC models at the molecular level, and fosters human cell-based approaches in preclinical drug evaluation.