The Use of Reconstructed Human Epidermis for Skin Absorption Testing: Results of the Validation Study

Abstract

A formal validation study was performed, in order to investigate whether the commercially-available reconstructed human epidermis (RHE) models, EPISKIN®, EpiDerm™ and SkinEthic®, are suitable for in vitro skin absorption testing. The skin types currently recommended in the OECD Test Guideline 428, namely, ex vivo human epidermis and pig skin, were used as references. Based on the promising outcome of the prevalidation study, the panel of test substances was enlarged to nine substances, covering a wider spectrum of physicochemical properties. The substances were tested under both infinite-dose and finite-dose conditions, in ten laboratories, under strictly controlled conditions. The data were subjected to independent statistical analyses. Intra-laboratory and inter-laboratory variability contributed almost equally to the total variability, which was in the same range as that in preceding studies. In general, permeation of the RHE models exceeded that of human epidermis and pig skin (the SkinEthic RHE was found to be the most permeable), yet the ranking of substance permeation through the three tested RHE models and the pig skin reflected the permeation through human epidermis. In addition, both infinite-dose and finite-dose experiments are feasible with RHE models. The RHE models did not show the expected significantly better reproducibility, as compared to excised skin, despite a tendency toward lower variability of the data. Importantly, however, the permeation data showed a sufficient correlation between all the preparations examined. Thus, the RHE models, EPISKIN, EpiDerm and SkinEthic, are appropriate alternatives to human and pig skin, for the in vitro assessment of the permeation and penetration of substances when applied as aqueous solutions.

Polymeric membranes modulate human keratinocyte differentiation in specific epidermal layers

“…polycarbonate filters in SkinEthic®, a type-I bovine collagen matrix in Episkin®, and a silicone gel in Epiderm® [1]. These models are currently the closest to the human epidermis, with an extensively proven accuracy and reproducibility [1][2][3][4], they represent the entire epidermis. To date, information about the creation of specific and distinct epidermal strata, important for the understanding of the interactions with external agents along the epidermis layers, is still missing.…”

Impact of structural differences in hyperbranched polyglycerol–polyethylene glycol nanoparticles on dermal drug delivery and biocompatibility

“…The efficiency of Nile red loaded PG-PEG particles for dermal drug delivery was evaluated according to validated test procedures using the Franz cell setup and full-thickness pig skin [24]. On the day of the experiment, punched disks of pig skin (2 cm diameter) were mounted onto static-type Franz cells (diameter 15 mm, volume 12 ml, PermeGear, Bethlehem, PA, USA) with the horny layer facing the air and the dermis having contact with the receptor fluid (phosphate buffered saline (PBS) pH 7.4; skin surface temperature 32°C).…”

“…NHK, HUVECS and NHDF (10 4 cells per well) were seeded into 96-well plates (TPP, Trasadingen, Germany). After 24 h, PG-PEG particles SK1-SK5 (0.05% and 0.005%) were added for 24 the cells were incubated with 10 ll MTT solution (5 mg/ml in PBS) for 4 h. After removing the supernatants, 50 ll dimethyl sulfoxide was added to dissolve the formazan salt and its optical density (OD) was measured using a microplate reader setting the excitation to 540 nm. 0.01% SDS served as the positive control.…”

“…For comparison, we also included CMS nanotransporter in the testing. The skin penetration studies were performed in pig skin which is an accepted alternative for human skin due to the limited availability of human skin [24,35]. The representative fluorescence images of skin sections after 6 h exposure to PG-PEG particles and CMS nanotransporters shown in Fig.…”

A custom tailored model to investigate skin penetration in porcine skin and its comparison with human skin

“…Bovine 100 Udder Skin (BUS) was also introduced as a valuable model to inves-101 tigate skin penetration but it has the limitation of a lower skin 102 barrier function compared to human and porcine skin [5,6]. 103 Reconstructed human skin and reconstructed human epidermis 104 also have shown to be promising for permeation and penetration 105 studies, including metabolism, however, barrier function of these 106 artificial reconstructs is still impaired compared to human and 107 porcine skin and reconstructed human epidermis does not contain 108 a dermal compartment [7,8]. Artificial membranes, used e.g.…”