Gene expression analysis in airway-secreting extracellular vesicles upon house dust mite exposure

In recent years, extracellular vesicles (EVs), such as exosomes and microvesicles have been attracting attention as an information source for the development of new diagnostic and treatment methods. With regard to the history of exosomes, Johnstone RM et al. had discovered fine particles of approximately 50 nm in size released from sheep reticulocytes, which were later termed ‘exosomes’.1 Lotvall J et al. reported in 2007, approximately 30 years after the original discovery,1 that RNA, such as microRNA (miRNA) and mRNA, is present in the exosomes and that these may be used for cell-to-cell transportation of miRNA. This report resulted in an immediate focus on exosome research.2 Exosomes and microvesicles have various common features, e.g. they are both EVs, approximately 100 nm in size, covered by a lipid bilayer membrane, and contain proteins and RNA in the vesicles3; however, the production processes are significantly different. Exosomes are formed during the production of endolysosomes by the fusion of endosomes and lysosomes; on the other hand, microvesicles are released outside from the cells following budding from the cell membrane. Exosomes contain Testis-specific gene 10, Heat shock protein70 and tetraspanins, such as CD9, CD63 and CD81; furthermore, they contain proteins such as p53, epidermal growth factor and fibroblast growth factor. Because methods for the precise distinction between exosomes and microvesicles have not been established, they are often collectively termed EVs.3 In this article, EVs that are secreted into the airway are abbreviated as airway-secreting EVs (AEVs). Because information in the extracellular vesicles RNA (evRNA) contains intracellular information associated with the cellular response to the pathology of the recipient cells, it is the focus for a new source of biomarkers.4 Sampling of the airway mucosa and the lung tissue is difficult; therefore, evRNA is beneficial because useful information can be obtained non-invasively. In this study, we used a mouse model of asthma induced by the house dust mite (HDM) allergen. AEVs were collected after allergen exposure. By performing a comprehensive analysis of mRNA profiling within AEVs, we examined the usefulness of mRNA as pathological biomarkers of AEVs. Our group has previously reported an experimental method for a mouse asthma model induced by HDM allergen.5 C57BL/6J mice