Bronchoscopic polarisation-sensitive optical coherence tomography reveals airway smooth muscle remodelling phenotypes in patients with asthma

Introduction &amp; Aims: Effective treatments for airway smooth muscle (ASM) remodelling are still lacking today, mainly due to the inability to accurately measure ASM in vivo. The study aims to demonstrate feasibility of bronchoscopic polarisation-sensitive optical coherence tomography (PS-OCT) to map the distribution of ASM remodelling in vivo and identify possible structural phenotypes.<br/><br/>Methods: We developed PS-OCT for measurement of ASM during bronchoscopy, sampling an area equivalent to 500 biopsies per subject. Normalised ASM mass (ASM area/lumen perimeter2) was measured in 1,540 cross-sections (154 airways) from 20 adults (9F/11M) with/without (7/13) ‘doctor-diagnosed’ asthma with an ACQ6 of median 1.5±1.1 (SD).<br/><br/>Results: The distribution of remodelling (ASM thickness above normal) in small (&lt;6 mm perimeter) and large (&gt;6 mm perimeter) airways was mapped in 10 min using PS-OCT. In participants with asthma ASM mass was heterogenous and increased (median 0.0072, Q1–Q3 0.0064–0.0089) compared with a control group (0.0039, 0.0035–0.0049), (p=0.012). Further, in the asthma group ASM remodelling was more prevalent (median 44% of airways examined, Q1–Q3 24–53%) than in the control group (median 0%, Q1–Q3 0–4%), (p=0.007). Airway size was not different between groups. Distinct phenotypes of ASM remodelling were observed: ASM remodelling occurring in the large airways only (17%), small airways only (17%), small and large airways (33%), or in neither the large or small airways (33%). <br/><br/>Conclusion: Bronchoscopic PS-OCT provides a feasible and safe way to comprehensively map ASM remodelling, enabling the development and testing of pharmaceuticals that target ASM structure.