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The SkinEthic Skin Corrosion Test (SCT) method can be used to predict the potential of chemicals to cause skin corrosion.

The test is based on measuring cytotoxic effects (via an MTT assay) following exposure to a chemical in the SkinEthic reconstructed human epidermis (SkinEthic RHE) model.

The approach has received regulatory approval as a replacement for in vivo skin corrosion tests (i.e. the in vivo Draize rabbit skin corrosion test). The test is also compliant with the OECD test guideline No 431.

The results of the validation study, the ESAC statement and our recommendation will be soon available on TSAR, the Tracking System for Alternative methods towards Regulatory acceptance.

Skin corrosion

[collapsed]For regulatory purposes, skin corrosion usually refers to chemically-induced full thickness destruction of skin tissue. In certain other cases, skin corrosion can also refer to any irreversible alterations in skin tissue that is caused by a chemical.

This contrasts with skin irritation where damage is usually reversible.

The potential of a chemical to cause skin corrosion is an important part of establishing procedures for the safe handling of chemicals as well as their packaging and transport.[/collapse]

SkinEthic Skin Corrosion Test (SCT)

[collapsed]The basis of the SkinEthic Skin Corrosion Test (SCT) is the determination of cytotoxicity in the SkinEthic RHE model following its exposure to a chemical.

The model is a three-dimensional human skin model comprising of a reconstructed epidermis and a functional stratum corneum (this is the outer layer of skin cells that primarily acts as a barrier). Furthermore, the epidermis layer is also differentiated into a number basal, spinous and granular layers.

The test method consists of a topical exposure of the model to a chemical for varying amounts of time, followed by a determination of cell viability (specifically cytotoxicity as determined via the MTT assay).

Viability decrease in treated cells is expressed comparatively to negative controls (i.e. cells treated with water). A positive control is also included in the method. Percentage viability (%) is used to predict and classify skin corrosion potential following a defined prediction model.

The method can be used with solid, liquid, semi-solid, and water-soluble and insoluble substances. It is not possible to assess the effects of gases or aerosols with this method.[/collapse]

Animal testing replacement

[collapsed]The test method has received regulatory approval as a replacement for the Draize skin corrosion test. Specifically, it can be used for hazard identification and the classification of corrosive potential of chemicals.

The test is also recommended for use within the context of a sequential skin corrosion testing strategy. The method can be used to identify corrosive substances and mixtures without the need for subsequent in vivo testing.

The identification of non-corrosive substances is also possible but only when supported by a weight of evidence determination using other existing data. In this case, it may involve data derived from prior experiments that did use animals.[/collapse]

Validation study

[collapsed]The SkinEthic Skin Corrosion Test (SCT) method was assessed in a validation study according to the OECD test guideline No 431.

In short, the previously validated EpiDerm skin corrosion test protocol (with minor modifications) was applied to the SkinEthic model.

After obtaining concordance with two previously validated skin corrosion methods (EpiDerm and EpiSkin models), inter-laboratory reproducibility was assessed in a blind trial in three separate laboratories. 12 reference chemicals were used in the validation study.

OECD test guideline No 431 sets out general conditions that a skin corrosion in vitro test model should meet prior to its use in routine testing.

The test guideline also requires the correct prediction of 12 reference chemicals and the assessment of intra- and inter-laboratory variability.[/collapse]

Validation study outcome

[collapsed]Data obtained in the validation study indicated that the SkinEthic Skin Corrosion Test (SCT) method was reproducible both within and between laboratories and over time. Concordance with previously validated methods was also very good.

The SkinEthic method reportedly could distinguish between corrosive and non-corrosive reference chemicals with an accuracy of 93%.[/collapse]

EURL ECVAM recommendations

[collapsed]On the basis of the outcome of the validation study and ESAC peer review, the EURL ECVAM Scientific Advisory Committee (ESAC) endorsed a statement that the SkinEthic human skin model can be used to distinguish between corrosive and non-corrosive chemical within the context of OECD test guideline No 431.

As a result, the method was recommended for consideration in terms of regulatory acceptance as a replacement for animal-based skin corrosion tests.[/collapse]