Interlaboratory validation of the in vitro eye irritation tests for cosmetic ingredients. (6) Evaluation of MATREX (TM)

MATREX(TM) is a test system for evaluating eye irritation potential, using the living dermal model (LDM). The LDM consists of normal human dermal fibr oblasts in a contracted collagen lattice, which eventually forms a three-di mensional structure. This system has several advantages. It can be applied to insoluble substances and does not require sterile conditions for operati on. In the present study, MATREX was introduced as an alternative to the Dr aize eye irritation lest (Draize test) for cosmetics ingredients. MATREX wa s evaluated through a three-phase series interlaboratory validation as part of a joint project of the National institute of Health Sciences (NIHS) and Japan Cosmetic Industry Association (JCIA). Toxicity for LDM was mainly ev aluated by cytotoxicity, the indicator was EC50 (concentration that inhibit s the viability of the cell to 50% of control) value. Additionally, MATREX score indicating the grade of cytotoxicity was also introduced in the third phase of the validation study. Both test procedures were controlled under the same standard operating procedure (SOP), at all the participating labor atories. A total of 39 test substances both water-soluble and -insoluble we re examined. LDM was applicable to almost all substances that could be eval uated by the Draize test. Furthermore interlaboratory variance was relative ly low. The correlation coefficient between the EC50 value and the maximal average Draize total score (MAS) was -0.672. The MATREX score was closely r elated to the EC50 value. Moreover, the MATREX scoring method showed a simi lar prediction ability for eye irritation potential to the EC50 method. Thu s, the MATREX scoring method, a simplified EC50 method, appears to be a via ble alternative to the current EC50 measurement method. The present results demonstrate the possibility that the MATREX system would form part of a pr ediction system of Draize test results. (C) 1999 Elsevier Science Ltd. All rights reserved.