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Bronchial thermoplasty decreases airway smooth muscle mass, collagen deposition in patients with asthma

Patients with asthma treated with bronchial thermoplasty demonstrated decreased airway smooth muscle mass and type-1 collagen deposition underneath the basement membrane, according to study results.

Jamila Chakir, PhD, of University Institute of Cardiology and Pulmonology of Québec at Université Laval in Québec, and colleagues evaluated the airway smooth muscles mass of 17 patients with asthma who underwent bronchial thermoplasty over the course of three visits.

During the first visit, the researchers performed a lower lobe bronchial biopsy in an area not treated with thermoplasty. All patients received a lower lobe bronchial biopsy of the treated area between 3 weeks and 14 weeks at the second visit. The third visit consisted of nine patients who underwent a subsequent biopsy of the treated lobe, which occurred between 7 weeks and 22 weeks after the initial visit.

The researchers found the airway smooth muscle mass decreased the total biopsy surface from 12.9 ± 1.2% at the first visit to 4.6 ± 0.8% at the second visit (P < .0001). Of the nine patients who underwent the subsequent biopsy at the third visit, the mean airway smooth muscle mass was 5.3 ± 1.3% at that visit (P < .0008).

Results showed type-1 collagen deposition underneath the basement membrane significantly decreased, from 6.8 ± 0.3 μm at the first visit to 4.3 ± 0.2 μm at the second visit. Type-1 collagen deposition was 4.4 ± 0.4 μm for the nine patients evaluated at a third visit (P < .0001).

One year after bronchial thermoplasty, patients demonstrated improvements in asthma control, the number of severe exacerbation events and doses of inhaled corticosteroid.

“Our data demonstrate that, in asthmatics, bronchial thermoplasty significantly modifies the asthmatic airway remodeling by decreasing both airway smooth muscle mass and collagen-1 deposition beneath the basal membrane,” Chakir and colleagues wrote. “This study did not include a nontreated control group, and the changes in airway smooth muscle mass and type-1 collagen were observed few weeks after treatment. Further research [is] needed to confirm these results and to extend the evaluation of bronchial thermoplasty on other airway remodeling parameters, their persistence over time and their correlation with asthma control.”

Disclosure: The researchers report funding from the IUCPQ pulmonary research unit.