Observational StudyPhenotyping Disease Severity in Asthma

The purpose of this study is to characterize and compare the molecular gene expression profile in endobronchial biopsies and cells recovered in bronchial washings from study subjects who have asthma of varying disease severity and who are on maintenance inhaled corticosteroid (ICS) treatment, with that for healthy control subjects. These studies will produce transcriptomic profiles of gene expression associated with asthma disease severity. The investigators will also culture epithelial cells from study participant endobronchial brushings, including those with asthma of varying disease severity and healthy control subjects, to examine differences in the response to corticosteroids (CS) in vitro. These studies will test whether intrinsic differences exist between the responses to ICS in each group.

60 participants will be recruited with 15 of each mild, moderate and severe asthma as defined by the Global Initiative for Asthma (GINA) guidelines, as well as 15 healthy controls. Participants will undergo an initial visit to obtain informed consent, bloodwork and to assess asthma control using the Asthma Control Questionnaire (ACQ); if >1.5, ICS dose will be increased, as per GINA strategy, for a 2 week 'stabilization' phase. Repeat ACQ, spirometry and sputum induction will be performed at visit 2. Bronchoscopy will be performed at visit 3, 2-4 weeks after visit 2. Mucosal biopsies, bronchial brushings and bronchial washings will be performed and processed as per our prior methods. Mucosal biopsies will be homogenized and processed for RNA, or fixed for later sectioning and histological examination. Biopsy RNA will be assessed for quality and subjected to RNA-sequencing of all human genes (mRNA-seq). Bronchial washing cells will be collected for differential cell counting and mRNA-seq analysis. Bronchial epithelial cells (BECs) from the brushings will be cultured. BECs treated with CS and inflammatory cytokines will allow comparative assessment of BEC responses.