Abstract
The aim of the present ring trial was to test whether two new methodological approaches for the in vitro classification of eye irritating chemicals can be reliably transferred from the developers’ laboratories to other sites. Both test methods are based on the well-established open source reconstructed 3D hemicornea models. In the first approach, the initial depth of injury after chemical treatment in the hemicornea model is derived from the quantitative analysis of histological sections. In the second approach, tissue viability, as a measure for corneal damage after chemical treatment, is analyzed separately for epithelium and stroma of the hemicornea model. The three independent laboratories that participated in the ring trial produced their own hemicornea models according to the test producer’s instructions, thus supporting the open source concept. A total of 9 chemicals with different physicochemical and eye-irritating properties were tested to assess the between-laboratory reproducibility (BLR), the predictive performance, as well as possible limitations of the test systems. The BLR was 62.5% for the first and 100% for the second method. Both methods enabled to discriminate Cat. 1 chemicals from all non-Cat. 1 substances, which qualifies them to be used in a top-down approach. However, the selectivity between No Cat. and Cat. 2 chemicals still needs optimization.
Highlights
In order to replace the Draize Eye Irritation Test (OECD TG 405) different approaches to develop animal-free alternative test methods have been pursued
The test of methyl pentynol led to discordant results, because the Depth of Injury (DOI) mean was below the 90% cut-off value in laboratory 3
Irrespective of whether the relative viability after topical treatment with chemicals was determined in an MTT assay of the whole tissue (Engelke et al, 2013), or whether sets of chemicals different from those used in the current study were assessed with the CCC and DOI methods, respectively (Zorn-Kruppa et al, 2014; Tandon et al, 2015; Bartok et al, 2015), the GHS Cat. 1 chemicals were always clearly separated from the other chemicals
Summary
In order to replace the Draize Eye Irritation Test (OECD TG 405) different approaches to develop animal-free alternative test methods have been pursued. In order to overcome this limitation in predictivity, two test methods, both based on a bioartificially produced 3D human corneal equivalent (hemicornea), were developed (Zorn-Kruppa et al, 2014; Bartok et al, 2015). Both methods predict the eye-irritation potential of chemicals for all 3 GHS categories within one test. Reliability and predictivity of both methods have been demonstrated in the developers’ laboratories with sets of reference chemicals representing all GHS categories and different physicochemical properties (Zorn-Kruppa et al, 2014; Bartok et al, 2015; Tandon et al, 2015)
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