Lung organoids and microplastic fibers: a new exposure model for emerging contaminants

Background Three-dimensional (3D) structured organoids are the most advanced in vitro models for studying human health effects, but they have been applied only once to evaluate the biological effects associated with microplastic exposure. Fibers from synthetic clothes and fabrics are a major source of airborne microplastics, and their release from dryer machines is still poorly understood. Objectives In this study, we aimed to establish an in vitro organoid model of human lung epithelial cells to evaluate its suitability for studying the effects of airborne microplastic contamination on humans. Furthermore, we aimed to characterize the microplastic fibers (MPFs) released in the exhaust filter of a household dryer and to test their interactions and inflammatory effects on the established lung organoids. Methods The polyester fibers emitted from the drying of synthetic fabrics were collected. Morphological characterization of the fibers released into the air filter was performed by optical microscopy and scanning electron microscopy (SEM)/energy dispersive x-ray spectroscopy (EDS). The organoids were exposed to various MPF concentrations (1, 10, and 50 mg L −1 ) and analyzed by optical microscopy, SEM, and confocal microscopy. Gene expression analysis of lung-specific genes, inflammatory cytokines, and oxidative stress-related genes was achieved by quantitative reverse transcription–polymerase chain reaction (qRT-PCR). Results We successfully cultured organoids with lung-specific genes. The presence of MPFs did not inhibit organoid growth, but polarized cell growth was observed along the fibers. Moreover, the MPFs did not cause inflammation or oxidative stress. Interestingly, the MPFs were coated with a cellular layer, resulting in the inclusion of fibers in the organoid. Discussion This work could have potential long-term implications regarding lung epithelial cells undergoing repair. This preliminary exposure study using human lung organoids could form the basis for further research regarding the toxicological assessment of emerging contaminants such as micro- or nanoplastics.