The skin corrosion potential of a chemical can be predicted with the EpiDerm skin corrosion test.
The method uses the EpiDerm human epidermal model of MatTek. In short, the skin model is exposed to a test chemical and then cytotoxicity is measured as a proxy for cell damage and hence skin corrosion.
The test has been scientifically validated and granted regulatory approval for the identification and classification of the corrosive potential of chemicals.
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.
[collapsed]Skin corrosion is considered to be the destruction of skin tissue following exposure to a chemical. In certain circumstances, it might also refer to any irreversible alteration of skin tissue following exposure.
This is in contrast to skin irritation where effects are usually considered reversible.
The potential of a chemical to cause skin corrosion is potentially important from the perspective of safe handling of chemicals as well as their safe packaging and transport.[/collapse]
EpiDerm Skin Corrosion Test (SCT)
[collapsed]This test is based on the EpiDerm human epidermal model that is manufactured by MatTek, Slovakia.
This is a reconstructed human epidermal model that is grown from human-derived epidermal keratinocytes (i.e. specific skin cells). They are cultured to form a multilayered and highly differentiated model of the human epidermis.
In more detail, the model consists of organised basal, spinous and granular layers of cells and a multilayer stratum corneum (the outside layer of skin that is essentially dead skin cells) that also includes intercellular lipid layers arranged in patterns analogous to those found in vivo (i.e. in humans). The model is cultured on specially prepared cell culture inserts and is shipped world-wide on a weekly basis as kits together with necessary culture media and handling plates.
For the test, the model is exposed to a test chemical for either three minutes or one hour, as well as positive and negative controls. After exposure, the cells are then washed (to remove the chemical) and exposed to MTT, which is a dye that can be used as a proxy for cytotoxicity, and therefore cell viability.
For corrosivity, a chemical is classed as a corrosive if after three minutes of exposure less than 50% of cells are viable. A chemical is also classed as corrosive in the case of after three minutes, greater than 50% of cells are still viable, but after one hour less than 15% are viable.[/collapse]
Animal testing replacement
[collapsed]The EpiDerm Skin Corrosion Test (SCT) has been granted regulatory approval as a replacement for the Draize (rabbit) skin corrosion test.
Specifically, this approval relates to hazard identification and classification of corrosive potential. The test can also be used to identify non-corrosive substances when used in conjunction with other methods.[/collapse]
[collapsed]In the mid to late 1990s a major validation study was performed by EURL ECVAM to assess four potential in vitro methods (not including the EpiDerm skin corrosion test) that might serve as replacements for the Draize in vivo rabbit skin corrosion test.
Following the successful completion of that study and the validation of two of the methods (TER assay and the EpiSkin skin corrosion assay) issues arose in the manufacturing process that meant the methods were temporarily unavailable. As a result the EpiDerm method was subjected to a catch-up study.[/collapse]
Validation study outcomes
[collapsed]A full elaboration of the prevalidation study, its workup and results, is available here. In short, the EpiDerm skin corrosion test was validated on the basis of high prediction rates on a wide range of chemicals.[/collapse]
EURL ECVAM recommendations
[collapsed]Based on the positive outcome of the study, the EURL ECVAM Scientific Advisory Committee (ESAC) unanimously endorsed the statement that the EpiDerm skin corrosion test method can be used to distinguish between corrosive and non-corrosive chemicals. Subsequently, the method has been included in legislation and is now the subject of an OECD test guideline (No 431).
Please note that subsequent re-evaluation of data revealed an unacceptably high level of false positive cases for certain classes of chemicals. Please see the subsequent ESAC statements (below) that relate to this issue. The validity of the methods (four methods relating to skin corrosion, including the EpiDerm skin corrosion test) were not called into question as a result of this re-analysis.[/collapse]