Sputum levels of transforming growth factor-beta1 in asthma: relation to clinical and computed tomography findings.
BACKGROUND
Transforming growth factor (TGF) beta1 is considered to play central roles in the pathogenesis of airway remodeling in asthma. This notion is based primarily on the results of experimental studies; clinical evidence is limited.


OBJECTIVE
To ascertain the involvement of TGF-beta1 in asthma.


METHODS
We studied 27 patients with moderate-to-severe, but stable, asthma treated with inhaled corticosteroids and 8 healthy controls. Helical computed tomography scans were acquired at full inspiration. Airway wall thickness (WT) was assessed on the basis of wall area corrected for body surface area (WA/BSA) and absolute WT corrected for BSA (WT/square root of BSA) according to a validated method. Induced sputum concentrations of TGF-beta1 were measured by enzyme-linked immunosorbent assay. Pulmonary function was evaluated.


RESULTS
Indices of expiratory airflow were significantly lower in the asthmatic patients than in the controls. WA/BSA, WT/square root of square root of BSA, and sputum concentrations of TGF-beta1 were significantly higher in the asthmatic patients. Sputum TGF-beta1 concentrations correlated positively with WA/BSA and WT/square root of BSA and negatively with forced expiratory volume in 1 second in both asthmatic and control subjects.


CONCLUSIONS
Levels of TGF-beta1 in induced sputum are elevated in asthmatic patients despite treatment with inhaled corticosteroids and are associated with airflow obstruction and airway wall thickening. TGF-beta1 is involved in the pathogenesis of airway remodeling and resultant functional impairment and it may be a target for specific medical treatment.
Yamaguchi
M
M
Department of Respiratory Medicine, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Niimi
A
A
Matsumoto
H
H
Ueda
T
T
Takemura
M
M
Matsuoka
H
H
Jinnai
M
M
Otsuka
K
K
Oguma
T
T
Takeda
T
T
Ito
I
I
Chin
K
K
Mishima
M
M
D000305:Adrenal Cortex Hormones / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D001249:Asthma / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D008875:Middle Aged; D013183:Sputum / Q000737:chemistry*; D036542:Tomography, Spiral Computed; D053773:Transforming Growth Factor beta1 / Q000032:analysis*
D000305:Adrenal Cortex Hormones; D018927:Anti-Asthmatic Agents; D053773:Transforming Growth Factor beta1