CHARACTERIZATION OF EOSINOPHILS IN INDUCED SPUTUM AND LUNG BIOPSY USING SINGLE CELL RNA-SEQ WITHOUT SUBTYPE DISTINCTION

Recently, the existence of different eosinophil subtypes has been suggested based on the differential expression of several surface molecules. However, the existence of eosinophil subtypes remains controversial. So, the objective of this study is to investigate the existence of eosinophil subtypes in induced sputum and lung biopsy. Induced sputum was collected from five patients with severe eosinophilic asthma. Additionally, six lung biopsy samples were taken from three severe asthmatic patients previous biological-treated and three patients after failure of biological drugs. The cell atlas were studied by Single Cell RNA-seq technique on the BD Rhapsody TM scanner. Then, the bioinformatic analysis allowed grouping the different cell types according to their gene expression. Several clusters composed by different cell types such as eosinophils, macrophages, neutrophils, and epithelial cells were established in both induced sputum and in lung biopsies. Eosinophil-related genes were analyzed (EPX, CCR3, CD101, CLC, SELL, ANXA1, SIGLEC10, ADGRE1, ITGAX, ITGB2, ALOX15) , resulting in an “eosinophil gene signature” that allowed to differentiate these cells from other cell types. However, it was not possible to differentiate eosinophil subtypes in either sputum or biopsies. Additionally, in lung biopsies, there were observed differences in the gene expression of ALOX15, POSTN, DPP10 or WFDC2 between both patient groups in eosinophils and, also, eosinophils from non-responder patients showed a different interactome respect to pre-treated asthmatic patients. Single cell RNA-seq enabled the characterization of eosinophils and other cell populations in induced sputum and lung biopsies. However, it was not possible to unequivocally objectify the existence of eosinophil subtypes based on their gene expression. Furthermore, in lung biopsies, cellular interactions between patients before biological drug treatment and non-responder patients were different.