CFTR and cystic fibrosis: Reproducing the levels of CFTR activity that are naturally present in the airways is complicated, given the regulation of activity by factors such as beta-adrenergic signaling28, VIP29, mechanical stress30 and others that are absent for our culture system; future studies will aim to optimize culture conditions to provide an accurate representation of in vivo airways, particularly (for CF research) regarding spontaneous CFTR activity.