New application for assessment of dry eye syndrome induced by particulate matter exposure

Dry eye syndrome (DES) is a multifactorial condition characterized by insufficient tear lubrication and eye irritation. Air pollutants, including particulate matter (PM), are an emerging threat to human health causing DES and other diseases. However, the pathogenic mechanisms of DES induced by PM exposure remain to be fully elucidated. Recent studies have attempted to create DES animal model using PM exposure. In this study, we explored a novel in vivo exposure model of DES, utilizing an inhalation device (aerosol exposure system) to reproduce the natural exposure to atmospheric PM. Rats were exposed to urban PM (UPM) using this aerosol system for 5 h per day over 5 days. Tear volume in UPM-exposed rats decreased significantly, whereas corneal irregularity and lissamine green staining significantly increased following UPM exposure. Additional effects observed following UPM exposure included apoptosis in the corneal epithelium and a decrease in the number of goblet cells in the conjunctiva. UPM also affected the stability of the tear film by disrupting its mucin-4 layer. In conclusion, aerosol exposure systems have proven effective as assessment tools for DES caused by PM.