LAUSR

Background: Bronchial Thermoplasty (BT) is a bronchoscopic treatment for severe asthma which reduces airway smooth muscle (ASM). The optimal patient responder profile is still under debate. In asthma, mast cell density is increased within the ASM and relates to bronchial hyper responsiveness. Aim: To determine the effect of BT on mast cells in airway wall biopsies and ASM specific area and relate this to treatment response. Methods: 14 severe asthma patients included in the TASMA trial were evaluated. Airway wall biopsies were obtained before and after BT and stained with ASM specific desmin and mast cell specific tryptase antibodies. Mast cells were manually counted and automatic digital analysis was used to calculate ASM area (Fig 1A-B). Results: Before BT, mast cells within ASM had a median of 35.5/mm2 (range 10-83) and 26.5/mm2 (range 12-73) for the total biopsy area. After BT, ASM (%) reduced with 58% (median 12.0% to 4.98% after BT; p Conclusions: Mast cells within the total airway wall seem to increase following BT. Due to BT induced ASM reduction, mast cells might shift from the ASM to the (sub)mucosal area.