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Identification of microplastics in human tear fluid and meibum: Implications for dry eye disease pathogenesis
Jingyi Wang1, Huanmin Kang2, Xixuan Huang3
1Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Laboratory, Beijing 100730, China.
Abstract:
Microplastics (MPs) are emerging environmental pollutants that are increasingly being detected in various human tissues. However, their impact on ocular health is underexplored. This study investigated the presence of MPs in tear fluid and meibum of 45 patients with dry eye disease (DED). Various examinations were conducted, including the Schirmer I test, fluorescein tear film break-up time (FBUT) and other dry eye-related assessments. MPs were identified in the tear fluid and meibum and were categorized into five distinct types, with polyethylene (PE) being the most predominant. Notably, PE levels exhibited significant correlations with key DED parameters, such as Schirmer I test scores and FBUT. In in-vitro studies, PE exposure reduced the viability and induced apoptosis of human corneal epithelial cells and conjunctival epithelial cells in a dose-dependent manner. In mouse models, topical exposure to PE drops, which imitate airborne PE exposure, induced typical dry eye signs, reduced goblet cell numbers, and triggered conjunctival inflammation. PE-treated meibomian glands exhibited changes, but these changes were not statistically significant, possibly because of the limited duration of the study. This study is the first to confirm the presence of microplastics (MPs) in human tear fluid and meibum while also offering novel insights into the potential pathogenic effects of airborne MP exposure on ocular health.
Insights
Microplastics (MPs) are found in human tears and meibum, potentially worsening dry eye disease (DED). Polyethylene MPs correlated with DED severity and caused cellular damage and inflammation in lab and animal models.
Area of Science:
- Ocular toxicology
- Environmental health
- Ophthalmology
Background:
- Microplastics (MPs) are pervasive environmental pollutants found in human tissues.
- The ocular health effects of MPs remain largely unknown.
- Dry eye disease (DED) affects millions globally, with multifactorial causes.
Purpose of the Study:
- To investigate the presence and impact of microplastics in the tear fluid and meibum of patients with DED.
- To explore the pathogenic mechanisms of microplastic exposure on ocular surface cells and tissues.
Main Methods:
- Analysis of tear fluid and meibum from 45 DED patients for microplastic identification and characterization.
- In vitro studies using human corneal and conjunctival epithelial cells exposed to polyethylene (PE).
- In vivo studies in mouse models simulating airborne PE exposure via topical application.
Main Results:
- Microplastics were detected in the tear fluid and meibum of DED patients, with polyethylene (PE) being the most common type.
- PE levels significantly correlated with DED severity indicators like Schirmer I test scores and tear film break-up time (FBUT).
- In vitro and in vivo studies demonstrated that PE exposure induces epithelial cell apoptosis, reduces cell viability, causes dry eye signs, and triggers ocular inflammation.
Conclusions:
- This study provides the first evidence of microplastics in human tear fluid and meibum.
- Airborne microplastic exposure, particularly polyethylene, may contribute to the pathogenesis of dry eye disease.
- Further research is warranted to elucidate the long-term effects and clinical implications of ocular microplastic contamination.
