Development and Evaluation of in vitro human Airway 3D model to predict human inhalation toxicity of volatile liquids, mists, and sprays.

Abstract

Animal models are accepted by regulators for acute respiratory toxicity (ART) but they have been discredited as predictors of human responses on physiological and ethical grounds. The goal was to develop ART tests utilizing the EpiAirway tissue model, to demonstrate correlation to GHS categories, and investigate reproducibility after extended transportation times. EpiAirway tissues produced at MatTek (USA) were exposed to test articles (TA, n=53) using the Direct Application Protocol (DAP) for exposure to mists, and the Vapor Cap Protocol (VCP) for exposure to volatile liquids. Tissues were exposed for 4hr to 4 doses to mimic in vivo rat exposure and tissue viability (MTT assay) was determined. The effective doses which reduced tissue viability by 25% (ED-25) or 50% (ED-50) were interpolated for the DAP and VCP, respectively, and correlated to the GHS categories. The DAP discriminated between GHS Cat.1&2/3&4/5&NC with a Sensitivity/ Specificity/ Accuracy (S/S/A) of 63.5/76.1/69.8%. In the VCP, tissues were exposed to TA vapor. The VCP correlated to GHS categories with S/S/A of 70.8/83.2/77.0. Tissues shipped to Kurabo (Japan) gave TEER values which were statistically equivalent values in the US (p value= 0.824) and hence it is likely that assay results in Japan will be similar to those obtained in the US. Both the VCP and DAP demonstrated good predictivity of GHS categories. They provide organ-specific in vitro tests that can improve the predictivity of human responses, reduce the number of animals being used, and help establish confidence for regulatory applications.