Fungal Microbiome Diversity in Urban Forest Decreases Asthma and Allergic Inflammation

Purpose: Recent attention has been directed toward understanding how exposure to green areas in residential urban environments can impact asthma morbidity. Limited and inconsistent results have explored the link between exposure to greenness and asthma, highlighting the need for further research in this area. We analyzed airborne fungal microbiomes from urban forests and urban centers to better understand how airborne microorganisms affect asthma and allergic inflammatory responses. Methods: Fungi were isolated from air samples collected from 25 urban forests and 4 urban centers in Seoul Metropolitan City, and the diversity of fungal microbiomes was analyzed. The number of asthma episodes in each district in Seoul Metropolitan City was examined using data from the National Health Insurance. Allergic inflammatory responses of fungi from the urban forests and urban centers were measured using human mast cells (HMC-1) and an experimental asthma animal model. Results: Fungal microbiome diversity in urban forests was significantly higher than in urban centers. A significant inverse correlation was observed between the number of urban forests per each district and asthma episodes among residents. Allergic inflammation in the activated HMC-1 cells and lungs of the asthma animal model was significantly suppressed by the fungal strains isolated from the urban forest samples compared to those from the urban centers. Conclusions: Fungal microbiome diversity, particularly from the urban forests, plays a role in reducing asthma morbidity and can modulate allergic inflammation. Residential proximity to urban forests was positively associated with current asthma, potentially indicating a role in reducing allergic inflammation through the diversity of the fungal microbial flora. These findings support the increasing public recognition of urban forest as an essential component of health-supportive environments.