D18-01 Small Microplastics in Human Lung Tissue: Detection, Quantification and Characterization

Abstract Introduction We are surrounded by household plastics that slowly break down into smaller stable fragments.1 The effects of airborne small (1-100 µm) microplastics (sMPs) inhalation in human health are concerning due to their environmental accumulation. We investigated the presence and impact of sMPs in human lung parenchyma. Methods We received human frozen distal lung tissues from 56 different subjects; one cohort from the Lung Tissue Research Consortium, NHLBI (US) comprising five healthy donors and five Idiopathic Pulmonary Fibrosis (IPF) (10 subjects), one cohort from the KU Leuven Lung Biobank (Belgium 1) comprising ten donors, ten IPF and ten Chronic Obstructive Pulmonary Disease (COPD) (30 subjects) and a second cohort from KU Leuven Lung Biobank (Belgium 2) from eight young and eight old healthy donors (16 subjects). Tissues were digested in KOH solution and filtered or embedded in optimal tissue compound and sectioned in a cryostat (Fig 1a). Filters and tissue sections were imaged in an epifluorescence microscope at 390/420 nm long pass filter. We manually counted sMPs (particles and fibers) in filters and normalized by wet lung sample weight. A selection of sMPs in filters were analyzed by Quantum Cascade Laser Infrared Spectroscopy (QCL-IR) and statistically matched to standards. We imaged regions of interest showing presence of sMPs in tissue sections. Graphs and statistics were performed in GraphPad 9.5.0. Results Filtration of digested lungs showed abundant and variable amounts of sMPs with most samples containing between 5,000 and 20,000 sMPs per gram of wet lung tissue (Fig 1b,c,g). QCL-IR confirmed heterogenous sMPs composition in lungs with Nylon, crumb rubber from used tires and Polyvinyl chloride being most abundant in the samples analyzed. Histology suggested sMPs alignment in the mucosal layer of some airways (Fig 1d,e) although staining confirmation is ongoing. The second Belgium cohort showed significantly higher sMPs amount than the rest (Fig 1g). We did not find a significant difference in sMPs among diseases (Fig 1h) but we observed a decreasing trend with age, that did not reach significance (Fig 1i). We are performing bulk RNA sequencing between samples containing high and low abundance of sMPs (Fig 1j) to assess molecular changes in tissues, followed by spatial transcriptomics to localized different biological responses. Conclusions sMPs are abundant and variable in lung tissue and likely influenced by the person’s lifestyle. Further analysis is needed to elucidate a possible biological response within the lung. References: 1 doi.org/10.1016/j.scitotenv.2022.159943 This abstract is funded by: BEST Initiative Deheyn Lab; European Commission H2020-MSC-IF (101033565)