Chlorine inhalation toxicology‐on‐a‐chip

Abstract

Accidental or environmental exposures to chlorine (Cl2 ) gas represent a major health threat. In particular, inhalation toxicology of Cl2 is an area of active research that focuses on investigating the deleterious effects of Cl2 on the human respiratory system and developing effective countermeasures to mitigate the risk of Cl2 -induced lung injury. While traditional cell culture models have gained widespread use as a simple and convenient research tool for in vitro investigation of Cl2 toxicity, they have limited capacity to recapitulate the complexity of native human lung tissues and thus largely fail to generate accurate predictions on pulmonary responses to Cl2 . Here we present two distinct microengineered biomimetic models that reconstruct the small airway and alveolar regions of the human lung for experimental studies of respiratory toxicity of Cl2 in the distal lung, which remains an outstanding question in inhalation toxicology of Cl2 . Our microengineered small airway model is composed of two microfabricated 3D chambers separated by a semipermeable membrane. The design of this microdevice makes it possible to mimic tissue compartmentalization in native airways by permitting long-term co-culture of primary human small airway epithelial cells, primary human pulmonary microvascular endothelial cells, and lung fibroblasts in a physiological 3D microenvironment to engineer fully differentiated airway epithelium directly exposed to air and supported by vascularized, perfusable 3D stromal tissues. The alveolar model, which is constructed in the same device, uses primary human type II pneumocytes harvested from iPSC-derived human alveolar organoids, some of which are transdifferentiated into type I alveolar epithelial cells during the course of controlled microfluidic culture in our device. In this study, these models were capable of producing human lung tissues that exhibited differentiated phenotype and functional capacity that could be maintained for extended periods (over 1 month). Notably, our data revealed the potential of the underlying pulmonary vasculature to accelerate and promote differentiation and maturation of lung epithelial cells during air-liquid interface culture. Using the lung-on-a-chip systems in conjunction with an in-house Cl2 exposure system, we conducted a preliminary study in which the devices were exposed to various concentrations of Cl2 gas (10, 50, 100 and 300 ppm) for 15 min. Our preliminary data showed the deleterious potential of Cl2 to induce acute injury of both small airway and alveolar tissues in a dose-dependent manner. Studies are underway for more extensive screening of Cl2 toxicity and in-depth analysis of lung injury in our models at the molecular, cellular, and tissue levels. We believe that the microengineered systems developed in this work represent an important advance in our ability to model acute respiratory responses to toxic gases and may provide a potentially powerful in vitro platform to study biochemical threats and develop medical countermeasures against them.