Direct measurement of airway narrowing in cultured whole airway segments – a new method to assess functional outcomes in culture

Asthma is characterized by excessive airway narrowing to contractile stimuli, termed airway hyper-responsiveness (AHR). Changes in airway smooth muscle (ASM) protein expression or mass are possible contributing mechanisms underlying AHR and have been examined using cell culture techniques. However, how these cellular changes to ASM relate to airway narrowing at the level of the whole airway is unclear.
We describe a new method to track changes in airway narrowing (responsiveness) in culture.
Whole airway segments (generation 12-17) from sheep or pig lungs were studied prior to (fresh) and after 24 and 48 hours in culture in Dulbecco’s Modified Eagle Medium with 2% Bovine-Serum Albumin, 1% L-Glutamine and antibiotics. Airway narrowing was measured from the % decrease in airway volume under a fixed transmural pressure, using a servo controlled syringe pump and organ bath apparatus.

Fresh airway segments narrowed strongly and approached closure with an Emax of 89.7% ± 9.5 (± SEM) and pD2 of 4.4 ± 0.1. Airway narrowing responses were preserved in culture, with no significant difference in maximal response or sensitivity to ACh after either 24 (Emax 89.6% ± 4.7, pD2 4.8 ± 0.3) or 48 hours in culture (Emax 84.4% ± 5.1, pD2 4.4 ± 0.3).
The present study has validated a new method allowing changes occurring at the cellular level in culture to be related to changes in airway responsiveness at the whole airway level.

No relevant conflicts of interest declared.