Measures of gene expression in sputum cells can identify TH2-high and TH2-low subtypes of asthma.
BACKGROUND
The 3-gene signature of periostin, chloride channel accessory 1 (CLCA1), and Serpin β2 (SERPINB2) in airway epithelial brushings is used to classify asthma into TH2-high and TH2-low endotypes. Little is known about the utility of gene profiling in sputum as a molecular phenotyping method.


OBJECTIVE
We sought to determine whether gene profiling in sputum cells can identify T(H)2-high and T(H)2-low subtypes of asthma.


METHODS
In induced sputum cell pellets from 37 asthmatic patients and 15 healthy control subjects, PCR was used to profile gene expression of the epithelial cell signature of IL-13 activation (periostin, CLCA1, and SERPINB2), TH2 genes (IL4, IL5, and IL13), and other genes associated with airway TH2 inflammation.


RESULTS
Gene expression levels of CLCA1 and periostin, but not SerpinB2, were significantly higher than normal in sputum cells from asthmatic subjects. Expression levels of IL-4, IL-5, and IL-13 were also significantly increased in asthmatic patients and highly correlated within individual subjects. By combining the expression levels of IL-4, IL-5, and IL-13 in a single quantitative metric ("T(H)2 gene mean"), 26 (70%) of the 37 asthmatic patients had T(H)2-high asthma, which was characterized by more severe measures of asthma and increased blood and sputum eosinophilia. TH2 gene mean values tended to be stable when initial values were very high or very low but fluctuated above or below the T(H)2-high cutoff when initial values were intermediate.


CONCLUSIONS
IL-4, IL-5, and IL-13 transcripts are easily detected in sputum cells from asthmatic patients, and their expression levels can be used to classify asthma into T(H)2-high and T(H)2-low endotypes.
Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, Calif; Cardiovascular Research Institute, University of California, San Francisco, Calif.
Michael C
MC
Peters
Cardiovascular Research Institute, University of California, San Francisco, Calif.
Zesemayat K
ZK
Mekonnen
Cardiovascular Research Institute, University of California, San Francisco, Calif.
Shaopeng
S
Yuan
Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, Calif; Cardiovascular Research Institute, University of California, San Francisco, Calif.
Nirav R
NR
Bhakta
Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, Calif; Cardiovascular Research Institute, University of California, San Francisco, Calif.
Prescott G
PG
Woodruff
Division of Pulmonary and Critical Care Medicine, University of California, San Francisco, Calif; Cardiovascular Research Institute, University of California, San Francisco, Calif. Electronic address: john.fahy@ucsf.edu.
John V
JV
Fahy
D000328:Adult; D001249:Asthma / Q000235:genetics* / Q000276:immunology; D015815:Cell Adhesion Molecules / Q000235:genetics; D018118:Chloride Channels / Q000235:genetics; D016207:Cytokines / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D008297:Male; D008875:Middle Aged; D017396:Plasminogen Activator Inhibitor 2 / Q000235:genetics; D013183:Sputum / Q000166:cytology*; D018418:Th2 Cells / Q000276:immunology*; D055815:Young Adult
C492109:CLCA1 protein, human; D015815:Cell Adhesion Molecules; D018118:Chloride Channels; D016207:Cytokines; C512835:POSTN protein, human; D017396:Plasminogen Activator Inhibitor 2
Asthma; BME; CLCA1; CPA3; Carboxypeptidase A3; Chloride channel accessory 1; Feno; Fraction of exhaled nitric oxide; IL-13; IL-17; IL-4; IL-5; LABA; Long-acting β-agonist; RIN; RNA integrity number; Serpin β2; SerpinB2; T(H)2 cell; UCSF; University of California, San Francisco; cytokines; eosinophils; eotaxin; inflammation; mast cells; phenotypes; sputum; β-Mercaptoethanol