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Updated: Sep 10, 2025
Methodology for Sputum Induction and Laboratory Processing
Published on: December 17, 2017
Sputum Transcriptomic Analysis and Clustering Reveals Insight Into Asthma Heterogeneity
Janne Goossens1, Anne-Charlotte Jonckheere1, Sien De Boodt1
1KU Leuven, Department of Microbiology, Immunology and Transplantation, Allergy and Clinical Immunology Research Group, Herestraat 49 Box 811, 3000, Leuven, Belgium.
Introduction:
Asthma is a heterogenous disease shaped by different inflammatory pathways. The aim is to investigate transcriptomic profiles in asthmatic patients and associate these with inflammation, airway damage and lung function.
Methods:
Adult asthma patients attending the outpatient pneumology clinic in our tertiary center, underwent diagnostic sputum induction and upon consent remaining sputum RNA was used for bulk RNA-sequencing (n = 56) coupled with unsupervised clustering. A retrospective analysis of comorbidities was performed. Sputum cytokine mRNA levels were determined via qPCR. Airway damage markers were determined in sputum supernatant RESULTS: Unsupervised clustering subdivided all asthmatic patients in one of three clusters. Cluster 1 contained most of the pauci-granulocytic asthma patients in whom oxidative stress was upregulated and TLR-signalling and several cytokine pathways down-regulated. Cluster 2 had upregulated S100 family signalling pathway genes, was mostly associated to type 2 inflammation with elevated sputum eosinophils, epithelial damage, IL-4 mRNA levels and allergy. Asthma patients in cluster 3 had worse lung function, upregulated inflammatory genes, increased sputum neutrophils and calprotectin levels.
Conclusion:
Three different asthma clusters could be identified bridging over the classical type 2/non-type 2 classification.
Clinical Trial:
ClinicalTrials.gov Identifier: NCT01224938 registered on 19 October 2010.
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