Effectiveness of bronchial thermoplasty in patients with severe refractory asthma: clinical and histopathological correlations.

The effectiveness of bronchial thermoplasty (BT) has been reported in severe asthma, yet its impact on the different bronchial structures remains unknown.To examine the effect of BT on bronchial structures and to explore their association with clinical outcome in severe refractory asthmatics.Bronchial biopsies (n = 300) were collected from 15 severe uncontrolled asthmatics before and 3 months after BT. Immunostained sections were assessed for airway smooth muscle (ASM) area, sub-epithelial basement membrane thickness, nerve fibers and epithelium neuroendocrine cells. Histopathological findings were correlated with clinical parameters.BT significantly improved asthma control and quality of life at both 3 and 12 months and decreased the numbers of severe exacerbations and the dose of oral corticosteroids. At 3 months, this clinical benefit was accompanied by a reduction in ASM area (median values [25-75 IQR] before and after BT, respectively, 19.7% [15.9-22.4] and 5.3% [3.5-10.1], P < 0.001), in sub-epithelial basement membrane thickening (4.4 μm [4.0-4.7] and 3.9 μm [3.7-4.6], P = 0.02), in sub-mucosal nerves (1.0 ‰ immunoreactivity [0.7-1.3] and 0.3 ‰ immunoreactivity [0.1-0.5], P < 0.001), in ASM-associated nerves (452.6 immunoreactive pixels per mm(2) [196.0-811.2] and 62.7 immunoreactive pixels per mm(2) [0.0-230.3], P = 0.02) and in epithelium neuroendocrine cells (4.9 per mm(2) [0-16.4] and 0.0 per mm(2) [0-0], P = 0.02). Histopathological parameters were associated with asthma control test, number of exacerbations, and visits to emergency department (all P ≤ 0.02), 3 and 12 months after BT.BT is a treatment option in severe therapy-refractory asthma that down-regulates selectively structural abnormalities involved in airway narrowing and bronchial reactivity, particularly ASM, neuroendocrine epithelial cells and bronchial nerve endings.