[Development of prediction models for three in vitro embryotoxicity tests which are evaluated in an ECVAM validation study] [Article in German]

Abstract

In 1997 ZEBET started the co-ordination of a study funded by the European Centre for the Validation of Alternative Methods (ECVAM) with the aim of prevalidation and validation of three in vitro embryotoxicity tests. These tests employ the cultivation of postimplantation whole rat embryos (WEC test), cultures of primary limb bud cells of rat embryos (micromass test, MM-Test ), and cultures of a pluripotent mouse embryonic stem cell line (embryonic stem cell test, EST). In the current Validation Study each of the tests is evaluated in four laboratories under blind conditions. In an initial phase of the validation study six out of 20 test chemicals comprising different embryotoxic potential (non, weak and strong embryotoxic) were tested. The results were used to improve the prediction models (PM) for the WEC test and the MM-Test in order to identify the embryotoxic potential of test chemicals. In addition, the existing PM for the EST was evaluated using the results from testing of the initial six chemicals. The PM for the EST was developed using the results of a previous prevalidation study (Scholz et al.,1999), in which 943.3% of the learning sample were classified correctly. Applying this PM to the results of the initial phase of the current validation study, 80% of the experiments were classified correctly according to the embryotoxic potential of the tested chemicals in vivo. Applying the PM for the MM-Test and the WEC test that were developed during the current validation study in both tests, 79.2% correct classifications were achieved. Since the PM of the WEC-Test took into account only parameters of growth and development, but not cytotoxicity data, a second PM (PM2) for the WEC was developed that was improved by incorporating cytotoxicity data of the differentiated mouse fibroblast cell line 3T3 derived from the EST. This approach, which has previously never been used as an adjunct to the WEC test, resulted in an increase of correct classifications to 96%.