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In vitro Skin Corrosion

In vitro Skin Corrosion

Skin corrosion refers to the production of irreversible damage to the skin manifested as visible necrosis through the epidermis and into the dermis, following the application of a test chemical [as defined by the United Nations (UN) Globally Harmonized System of Classification and Labelling of Chemicals (GHS)].

In Vitro Skin corrosion Test

Skin corrosion refers to the production of irreversible damage to the skin manifested as visible necrosis through the epidermis and into the dermis, following the application of a test chemical [as defined by the United Nations (UN) Globally Harmonized System of Classification and Labelling of Chemicals (GHS)]. An in vitro skin corrosion test is validated as alternatives to animal use for skin corrosion test which avoid pain and suffering of animals. This test addresses the human health endpoint skin corrosion.

 

In Vitro Skin corrosion Test - RhE method

OECD431

It makes use of reconstructed human epidermis (obtained from human derived non-transformed epidermal keratinocytes) which closely mimics the histological, morphological, biochemical and physiological properties of the upper parts of the human skin, i.e., the epidermis.

 

In vitro skin corrosion study is performed to identify the non-corrosive and corrosive potential of chemicals using reconstructed human epidermis (RHE) tissue in accordance with the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS). These test method is applicable to a wide range of chemicals classes and physical states, for both substances and mixtures.  JRF has conducted several in-house validation experiments using 15 different corrosive and non corrosive chemicals with their known skin corrosive property to validate the study in compliance with the OECD 431. Each chemical is applied topically onto three tissue replicates for the period of 3-minutes and 60-minutes. At the end of the treatment period, cytotoxicity is determined by the using MTT Assay. Adapted controls are used for MTT reducing chemicals.

 

In Vitro Skin Corrosion: Transcutaneous Electrical Resistance Test Method (TER)

OECD430

This model/study addresses the human health endpoint skin corrosion. It is based on the rat skin transcutaneous electrical resistance (TER) test method, which utilizes skin discs to identify corrosives by their ability to produce a loss of normal stratum corneum integrity and barrier function.

 

A validation study and other published studies have reported that the rat skin TER test method is able to discriminate between known skin corrosives and non-corrosives with an overall sensitivity of 94% and specificity of 71% for a database of 122 substances

 

The test chemical is applied for up to 24 hours to the epidermal surfaces of skin discs in a two-compartment test system in which the skin discs function as the separation between the compartments. The skin discs are taken from humanely killed rats aged 28-30 days. Corrosive chemicals are identified by their ability to produce a loss of normal stratum corneum integrity and barrier function, which is measured as a reduction in the TER below a threshold level. For rat skin TER, a cut-off value of 5kΩ has been selected based on extensive data for a wide range of substances where the vast majority of values were either clearly well above (often > 10 kΩ), or well below (often < 3 kΩ) this value. Generally, test chemicals that are non-corrosive in animals but are irritant or non-irritant do not reduce the TER below this cut-off value.

 

A dye-binding step is incorporated into the test procedure for confirmation testing of positive results in the TER including values around 5 kΩ. The dye-binding step determines if the increase in ionic permeability is due to physical destruction of the stratum corneum. The TER method utilizing rat skin has shown to be predictive of in vivo corrosivity in the rabbit assessed under OECD guideline 404.

 

A limitation of this Test Guideline, as demonstrated by the validation studies, is that it does not allow the sub-categorization of corrosive substances and mixtures in accordance with the UN GHS.

 

In Vitro Membrane Barrier Test Method for Skin Corrosion

OECD435

Skin corrosivity has traditionally been assessed by applying the test substance to the skin of living animals and assessing the extent of tissue damage after a fixed period of time. The UN GHS tiered testing and evaluation strategy for the assessment and classification of skin corrosivity allows for the use of validated and accepted Alternative test methods. In this tiered strategy, positive results from Alternative test methods can be used to classify a substance as corrosive without the need for animal testing, thus reducing and refining the use of animals in testing.

 

In this study, the test system is composed of two components, a synthetic macromolecular bio-barrier and a CDS; the basis of this test method is that it detects membrane barrier damage caused by corrosive test substances after the application of the test substance to the surface of the artificial membrane barrier, presumably by the same mechanism(s) of corrosion that operate on living skin.

 

Penetration of the membrane barrier (or breakthrough) might be measured by a number of procedures, including a change in the colour of a pH indicator dye or in some other property of the indicator solution below the barrier.

 

The classification assigned is based on the time it takes a substance to penetrate through the membrane barrier to the indicator solution.

 

 


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