Date Published: January 20, 2017
Publisher: Public Library of Science
Author(s): Jie Ji, Anna Hedelin, Maria Malmlöf, Vadim Kessler, Gulaim Seisenbaeva, Per Gerde, Lena Palmberg, Amitava Mukherjee.
Exposure to agents via inhalation is of great concerns both in workplace environment and in the daily contact with particles in the ambient air. Reliable human airway exposure systems will most likely replace animal experiment in future toxicity assessment studies of inhaled agents.
In this study, we successfully established a combination of an exposure system (XposeALI) with 3D models mimicking both healthy and chronic bronchitis-like mucosa by co-culturing human primary bronchial epithelial cells (PBEC) and fibroblast at air-liquid interface (ALI). Light-, confocal microscopy, scanning- and transmission electron microscopy, transepithelial electrical resistance (TEER) measurement and RT-PCR were performed to identify how the PBEC differentiated under ALI culture condition. Both models were exposed to palladium (Pd) nanoparticles which sized 6–10 nm, analogous to those released from modern car catalysts, at three different concentrations utilizing the XposeALI module of the PreciseInhale® exposure system.
Exposing the 3D models to Pd nanoparticles induced increased secretion of IL-8, yet the chronic bronchitis-like model released significantly more IL-8 than the normal model. The levels of IL-8 in basal medium (BM) and apical lavage medium (AM) were in the same ranges, but the secretion of MMP-9 was significantly higher in the AM compared to the BM.
This combination of relevant human bronchial mucosa models and sophisticated exposure system can mimic in vivo conditions and serve as a useful alternative animal testing tool when studying adverse effects in humans exposed to aerosols, air pollutants or particles in an occupational setting.
As more and more ethical concerns are raised over the use of animal models in medical research, attempts are made to reduce and replace animal experiments. For primary contact organs like the lung, in vivo exposure occurs at an air-liquid interface (ALI) close to the apical cell surfaces while in vitro submerge exposure poorly represents the in vivo route of exposure. Moreover, when exposing epithelial cells in vitro to particles under submerged condition, a substantial fraction of the particles will either remain in the liquid or be lost to the lateral walls of the culture vessel, which alter the dose of particles as well as the interaction with the cells. Some in vitro techniques for exposing primary or cell line cultures in ALI have been described in the literature[1–3], also several ALI cell cultures are commercially available and have been used for inhalation toxicology research, for instance MucilAirTM-HF (Epithelix, Genève, Switzerland) and EpiAirwayTM (MatTek, Ashland, USA).
In this study, we succeeded in combining 3D models mimicking both healthy and chronic bronchitis-like mucosa (by using PBEC and fibroblast) which consisted of all types of cells presentin vivo with controlled aerosol exposure module (XposeALI). In order to evaluate this combined system, exposure to Pd nanoparticles induced an increased secretion of IL-8, where chronic bronchitis-like model released significantly more IL-8 than normal models.
In present study, we succeeded in combining relevant human airway wall models with controlled aerosol exposures using the XposeALI exposure module. In addition, the modification of the 3D model leading to mucus producing cell metaplasia and hyperplasia, which are phenomena observed in airway diseases such as COPD and chronic bronchitis, are suited for mimicking interactions between nanoparticle exposures and the innate immune response in chronic bronchitis patients. For both healthy subjects, and subjects with respiratory diseases, our chosen test substrate, Pd nanoparticles present in polluted ambient air, is of clinical importance. With further development and validation, this exposure setting could form part of an in vitro testing strategy to reduce the requirement for animal inhalation studies.