Evaluation of in vitro rat and human airway epithelial models for acute inhalation toxicity testing

In vivo models (mostly rodents) are currently accepted by regulatory authorities for assessing acute inhalation toxicity. Considerable efforts have been made in recent years to evaluate in vitro human airway epithelial models (HAEM) as replacements for in vivo testing. In the current work, an organotypic in vitro rat airway epithelial model (RAEM), rat EpiAirway™, was developed and characterized to allow a direct comparison with the available HAEM, human EpiAirway™, in order to address potential interspecies variability in responses to harmful agents. The rat and human models were evaluated in two independent laboratories with 14 reference chemicals, selected to cover a broad range of chemical structures and reactive groups, as well as known acute animal and human toxicity responses, in three replicate rounds of experiments. Toxicity endpoints included changes in tissue viability (MTT assay), epithelial barrier integrity (TEER, transepithelial electrical resistance), and tissue morphology (histopathology). The newly developed rat EpiAirway™ model produced reproducible results across all replicate experiments in both testing laboratories. Furthermore, a high level of concordance was observed between the RAEM and HAEM toxicity responses (determined by IC25) in both laboratories, with R2 = 0.78 and 0.88 when analyzed by TEER; and R2 = 0.92 for both when analyzed by MTT. These results indicate that rat and human airway epithelial tissues respond similarly to acute exposures to chemicals. The new in vitro RAEM will help extrapolate to in vivo rat toxicity responses and support screening as part of a 3Rs program.

目前监管机构已普遍接受体内模型（in vivo，多为啮齿类动物）用于评估急性吸入毒性。近年来，学界已投入大量精力探索体外（in vitro）人呼吸道上皮模型（human airway epithelial models, HAEM）作为体内测试的替代方案。本研究构建并表征了一种器官型体外大鼠呼吸道上皮模型（rat airway epithelial model, RAEM）——大鼠EpiAirway™，以便与现有人源HAEM（人EpiAirway™）开展直接对比，从而探究有害物暴露下不同物种间的反应差异。
本研究在两家独立实验室中，通过三轮重复实验，使用14种参考化学品对大鼠及人源模型进行评估。所选参考化学品涵盖了广泛的化学结构与活性基团，同时覆盖了已知的急性动物及人体毒性反应类型。
本次评价的毒性终点包括组织活力变化（MTT试验，MTT assay）、上皮屏障完整性（跨上皮电阻，transepithelial electrical resistance, TEER）以及组织形态学改变（组织病理学检测）。
新构建的大鼠EpiAirway™模型在两家实验室的所有重复实验中均表现出良好的可重复性。此外，两家实验室中RAEM与HAEM的毒性反应（以IC25值表征）均呈现高度一致性：通过TEER分析得到的决定系数R²分别为0.78与0.88；通过MTT试验分析得到的R²均为0.92。
上述结果表明，大鼠与人类呼吸道上皮组织在急性化学物暴露下的反应相似。这款新型体外RAEM模型将有助于外推大鼠体内毒性反应，并可作为3R（替代、减少、优化）动物实验项目的筛查工具提供支持。