Airway smooth muscle and long-term clinical efficacy following bronchial thermoplasty in severe asthma

Abstract

The mechanism of action of bronchial thermoplasty (BT) treatment for patients with severe asthma is incompletely understood. This study investigated the 2.5-year impact of BT on airway smooth muscle (ASM) mass and clinical parameters by paired data analysis in 22 patients. Our findings demonstrate the persistence of ASM mass reduction of >50% after 2.5 years. Furthermore, sustained improvement in asthma control, quality of life and exacerbation rates was found, which is in line with previous reports. An association was found between the remaining ASM and both the exacerbation rate (r=0.61, p=0.04 for desmin, r=0.85, p<0.01 for alpha smooth muscle actin (SMA)) and post-bronchodilator forced expiratory volume in 1 s predicted percentage (r=-0.69, p=0.03 for desmin, r=-0.58, p=0.08 for alpha SMA). This study provides new insight into the long-term impact of BT.

Keywords: Asthma.

Figure 1

The graphs show (A) the ASM desmin% area and (B) alpha actin% area data expressed as medians (IQRs) of 12 patients with asthma. Examples of biopsies showing ASM mass stained by desmin and alpha actin at baseline, 0.5 year post-BT and 2.5 years post-BT. P values are given between baseline and 0.5 year post-BT and between baseline and 2.5 years post-BT and calculated with the Wilcoxon signed-rank test. ASM, airway smooth muscle; BT, bronchial thermoplasty.