Effects of Bronchial Thermoplasty on Airway Smooth Muscle and Collagen Deposition in Asthma.
BACKGROUND
The aim of bronchial thermoplasty is to improve asthma symptoms by reducing central airway smooth muscle mass. Up to now, the reduction of smooth muscle mass has been documented for only 1 group of 10 patients who had 15% or more of their pretreatment total bronchial biopsy area occupied by smooth muscle.


OBJECTIVE
To evaluate the effects of bronchial thermoplasty on airway smooth muscle mass and airway collagen deposition in adult patients with asthma, regardless of pretreatment smooth muscle area.


METHODS
Seventeen patients with asthma underwent bronchial thermoplasty over the course of three visits. At Visit 1, bronchial biopsies were taken from the lower lobe that was not treated during this session. At Visit 2 (3-14 wk after the first visit), all 17 patients underwent biopsy of the lower lobe treated during the first procedure. At Visit 3 (7-22 wk after the first visit), nine patients agreed to undergo biopsy of the same lower lobe. Histological and immunohistochemical analyses were performed on the biopsy specimens.


RESULTS
Bronchial thermoplasty decreased airway smooth muscle from 12.9 ± 1.2% of the total biopsy surface at Visit 1 to 4.6 ± 0.8% at Visit 2 (P < 0.0001). For the nine patients who underwent a third biopsy, mean airway smooth muscle area was 5.3 ± 1.3% at Visit 3 (P = 0.0008 compared with baseline). Bronchial thermoplasty also decreased Type I collagen deposition underneath the basement membrane from 6.8 ± 0.3 μm at Visit 1 to 4.3 ± 0.2 μm at Visit 2 (P < 0.0001) and to 4.4 ± 0.4 μm for nine patients at Visit 3 (P < 0.0001 compared with baseline). Over the course of 1 year after treatment, the doses of inhaled corticosteroid, the number of severe exacerbations, and asthma control all improved (P ≤ 0.02).


CONCLUSIONS
For patients with severe asthma, bronchial thermoplasty reduced the smooth muscle mass of treated airway segments, regardless of the baseline level of muscle mass. Treatment also altered the deposition of collagen. At follow-up, bronchial thermoplasty improved asthma control; however, the limited number of subjects did not allow us to evaluate possible correlations between these improvements and the studied histological parameters. Further studies are needed to confirm these results and evaluate their persistence.
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Jamila
J
Chakir
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Ikhlass
I
Haj-Salem
2 Département des Maladies Respiratoires, AP-HM, Laboratoire INSERM CNRS U 1067, UMR7733, Aix-Marseille Université, Marseille, France.
Delphine
D
Gras
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Philippe
P
Joubert
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Ève-Léa
ÈL
Beaudoin
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Sabrina
S
Biardel
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Noel
N
Lampron
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Simon
S
Martel
2 Département des Maladies Respiratoires, AP-HM, Laboratoire INSERM CNRS U 1067, UMR7733, Aix-Marseille Université, Marseille, France.
Pascal
P
Chanez
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Louis-Philippe
LP
Boulet
1 Institut universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Québec, Canada; and.
Michel
M
Laviolette
D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000328:Adult; D056151:Airway Remodeling; D001249:Asthma / Q000188:drug therapy / Q000473:pathology / Q000601:surgery*; D001706:Biopsy; D001980:Bronchi / Q000601:surgery*; D001999:Bronchoscopy / Q000379:methods; D017115:Catheter Ablation / Q000379:methods*; D024042:Collagen Type I; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000473:pathology*; D016896:Treatment Outcome
D000305:Adrenal Cortex Hormones; D024042:Collagen Type I
airway remodeling; airway smooth muscle; bronchial thermoplasty; severe asthma