Cell culture
Primary NECs were harvested from the inferior surface of the anterior turbinate using a purpose designed curette (ASI Rhino-Pro, Arlington Scientific, USA). Scrapings were suspended in 2ml of RPMI (Roswell Park Memorial Institute) media and immediately transported to the laboratory 6. Cells were pelleted by centrifugation, grown in submerged culture until they reached passage 2 (approximately 3 weeks) and then cryopreserved 6. When required, cells were thawed and grown in ALI culture into a well differentiated epithelium, validated by the presence of beating cilia under light microscopy (see online supplement). Epithelial integrity was validated by measuring the resistance to an electric current travelling across the cell culture (Trans-epithelial electrical resistance, TEER) using an EVOM2 Epithelial Voltohmmeter (World Precision Instruments Inc., Sarasota, FL, USA) connected to STX2 Chopstick Electrode (World Precision Instruments Inc.).