Gene Expression Profiles of Acute Asthma Subphenotypes of ...

Gene Expression Profiles of Acute Asthma: Subphenotypes of Treatment Response Kelly Allred Metz, MD Cincinnati Children’s Hospital Medical Center Asthma Admissions  At CCHMC, 3000 children are seen annually in the ED for acute asthma exacerbations 25% admitted  25% of admitted stay > 24 hours   Among hospitalized children for treatment of acute asthma exacerbation, up to 27% require longer than 3 day stay Heterogeneity of Asthma  Heterogeneous phenotype among those admitted 75% discharged within 24 hours – “good responders”  25% take longer – “poor responders”   Molecular classification of phenotypes may enable informed treatment plans Where’s Waldo? Where’s Waldo? Microarray   Study expression of large numbers of genes simultaneously Identify gene expression profiles associated with disease states Microarray and Bronchial Tissue  Comparison of gene expression profiles from bronchial tissues of asthmatics before and after treatment with ICS 79 known genes differentially expressed in asthmatics  After 28 days of ICS treatment, 26 (33%) of the genes responded to ICS  Microarray studies can identify genes modulated by treatment in the context of asthma  You’re going to do what? Nasal Epithelium and Asthma  Upper airway reflects pathophysiologic changes in the lower airway Nasal Epithelium in Asthma     Similar inflammatory processes underlie rhinitis and asthma Nasal allergen challenge initiates pulmonary inflammation Segmental allergen challenge in the lung induces inflammation in bronchial and nasal mucosa Eosinophil counts in the nose correlate with those in the lung in patients with nonallergic asthma Multiple studies, see reference list Microarray and Nasal Epithelium  There are consistent gene expression profile signatures that are present in nasal epithelial RNA samples from children experiencing an acute asthma attack (v. stable asthma) at the time they present in the ED Patient Group non-asthma stable-asthma acute-asthma OBSERVED PATTERN down in acute down in acute and stable 872 probesets up in acute up in acute and stable down in stable up in stable Summary   Microarray has been used previously to identify gene profiles associated with asthma, but previous studies have been limited to adult patients and to RNA derived from peripheral blood cells or bronchial biopsy specimens Microarray is validated by fact that many genes found to be induced in childhood asthma have been implicated in the pathogenesis of asthma in other studies Summary (cont)    Human studies are limited by access to tissue Nasal epithelial cells serve as an accessible alternative proxy for lower respiratory epithelium Exacerbated asthma status is distinguished from stable asthma based on strong gene expression signatures in nasal epithelial samples Hypothesis   The gene expression profiles of children who respond to treatment quickly (< 24 hours) will be different than children who take longer (≥ 24 hours) to respond at ~24 hours and 2 weeks The change in the gene expression profile of each individual will change from initial presentation (before steroid), to ~24 hours, and 2 week follow up Hypothesis (cont.) ED ≤24 hrs 2 weeks A1 discharge A2 A3 B1 B2 discharge B3    A2 ≠B2 A1 ≠A2≠A3 B1 ≠B2≠B3 Faster Patient Populations    Ongoing registry of children with asthma and children presenting to the ED with asthma Ages 5-18 years Greater Cincinnati Metropolitan area Fellowship Goal: PILOT STUDY Sample Size   80-100 admitted patients (15-20 patients for pilot) Over-sample 320-400 patients in ED Inclusion/Exclusion Criteria  Inclusion criteria:     Exclusion criteria:   Age 5-18 years History of asthma Acute Asthma Exacerbation Nasal or systemic steroids in past 30 days Nebulized or inhaled steroids with face mask in past 30 days (may use mouthpiece & spacer)       Received Magnesium sulfate or Heliox Nasal obstruction Comoribid lung condition (CF, congenital, bronchopulmonary dysplasia, etc) D/c from NICU on O2 Dependence on oral steroid or immunosuppressant Bleeding diathesis Outcomes  Profile RNA expression pattern from nasal epithelium of children admitted for asthma exacerbations at 3 time points Will compare to:      to determine molecular heterogeneity of response to therapy Pediatric Asthma Severity Score (PASS) Asthma Control Test score (ACT) PFTs FENO Why are gene expression changes important?  Can it be predictive? Not designed to predict treatment response  Is designed to determine heterogeneity of response as measured by changes in gene expression profile over time  Why are gene expression changes important?  Implications If identify a gene in poor responders that does not respond to current treatment, may become target for novel therapy  If identify a poor responder based on profile, in future may consider using alternative existing treatment, different dosing of same treatment, or longer course  Potential Issues  Definitions  Good (≤ 24 hours) vs. poor responder (> 24 hours) Time to response to treatment, or time when eligible for discharge, will be based on when patient gets to Q4h x 2  Allows for increased length of stay due to social or hospital system issues  Potential Issues (cont.)  Variables affecting the gene expression profile  Severity of asthma exacerbation Exclude ICU admissions  Exclude those who receive magnesium or Heliox  Exclude mild exacerbations that are discharged home   Prior treatment Exclude nasal steroids in past 30 days  Exclude inhaled steroids IF nebulized or via face mask  Exclude systemic steroids in past 30 days  Potential Issues (cont.)  Variables affecting the gene expression profile  Concomitant respiratory infection Viral PCR performed on each patient, in collaboration with James Gern, MD in Madison, WI  Examine relationship of presence of virus to change in profile in analysis   Allergic rhinitis Including AR patients, excluding nasal steroids  Examine relationship of specific IgE to change in profile in analysis  Potential Gene Targets? up in acute-1 Cilia, flagella, motility, B cell differentiation down in acute Apoptosis, angiogenesis, proteolysis, signaling up in acute-2 Epigenetic regulation, RNA metabolism, nucleolus, B cell differentiation Epithelial, transcription, membrane protein signaling, carbohydrate catabolism up in stabilized down in stabilized Transcription, membrane protein signaling, adhesion Myeloid activation, K-channel adhesion, endothelial cell regeneration up in stabilized and acute non-asthma stabilized -asthma acuteasthma non-asthma stabilized -asthma acuteasthma Investigators         Gurjit Hershey, MD, PhD – Allergy & Immunology Rick Strait, MD – Emergency Medicine Richard Ruddy, MD – Emergency Medicine Carolyn Kercsmar, MD – Pulmonary Jeffrey Simmons, MD – General Pediatrics Robert Kahn, MD – General Pediatrics Dennis Drotar, PhD – Adherence Psychology Bruce Aronow, PhD – Bioinformatics Thanks     Dr. Elizabeth Matsui, MD Dr. Gurjit Khurana Hershey, MD, PhD Dr. Umasundari Sivaprasad, PhD Hershey lab members Additional References  Nasal Epithelium and Asthma Additional References (cont.)