Human lung epithelial cell cultures for analysis of inhaled toxicants: Lessons learned and future directions

Abstract

A B S T R A C TThe epithelium that covers the conducting airways and alveoli is a primary target for inhaled toxic substances, and therefore a focus in inhalation toxicology. The increasing concern about the use of animal models has stimulated the development of in vitro cell culture models for analysis of the biological effects of inhaled toxicants. However, the validity of the current in vitro models and their acceptance by regulatory authorities as an alternative to animal models is a reason for concern, and requires a critical review. In this review, focused on human lung epithelial cell cultures as a model for inhalation toxicology, we discuss the choice of cells for these models, the cell culture system used, the method of exposure as well as the various read-outs to assess the cellular response. We argue that rapid developments in the 3D culture of primary epithelial cells, the use of induced pluripotent stem cells for generation of lung epithelial cells and the development of organ-on-a-chip technology are among the important developments that will allow significant advances in this field. Furthermore, we discuss the various routes of application of inhaled toxicants by air-liquid interface models as well as the vast array of read-outs that may provide essential information. We conclude that close collaboration between researchers from various disciplines is essential for development of valid methods that are suitable for replacement of animal studies for inhalation toxicology.

New Approach Methods to Evaluate Health Risks of Air Pollutants: Critical Design Considerations for In Vitro Exposure Testing

“…The types of cells that are commonly used in air pollution research largely consist of cells derived from the respiratory system. Cell line selections for inhalation toxicology research have previously been summarized and reviewed [49]; and as such, this section provides a high-level overview of pertinent cell lines. Some of the most widely used immortalized cell lines represent those that are derived from human tumors or transformed from normal primary cells.…”

“…When deciding which cell type to use in an in vitro study design, it is important to consider the advantages and limitations surrounding cancer vs. primary cell lines, as well as the applicability of the respiratory region in which the cells were derived. As mentioned above, cancer cells lines are more robust and can therefore be more amenable to varying exposure conditions; and transformed cell lines can be more indicative of responses from healthy individuals [49]. Furthermore, the region of the respiratory tract in which the cells were derived is important to consider.…”

Impact of Sea Breeze Dynamics on Atmospheric Pollutants and Their Toxicity in Industrial and Urban Coastal Environments

“…The cellular model chosen was the BEAS 2B cell line (ATCC ® CRL-9609 ™ ), corresponding to human bronchial epithelial cells. BEAS 2B cells are frequently used in air liquid interface (ALI) exposure studies [82,83]. BEAS 2B cells were seeded on Transwell ® inserts with LHC 9 medium in the culture room 24 h before the exposure.…”

High-content screening for rare respiratory diseases: readthrough therapy in primary ciliary dyskinesia

“…Although drugs were applied basolaterally in cell culture medium, it may be possible to develop a system in which aerosolized drugs are applied to cultures. As such, the approach described here is likely to be widely applicable in basic lung biology, in inhalation toxicology [41] and for investigations of other respiratory diseases with epithelial involvement, such as chronic obstructive pulmonary disease (COPD), asthma and pulmonary fibrosis. While organoid culture has been developed as a scalable primary cell culture model in the context of cystic fibrosis [42], where organoid swelling can be used as a proxy for ion channel function [43,44], this approach -even with the development of airway organoids [45,46] -lends itself less well to ciliary diseases, where access to and reliable measurement from the apical surface of the epithelium is essential.…”