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It will depend on the cell type as well as the origin and disease state of the cells being used. For example, the amount of time can depend on whether you are using freshly isolated primary cells or commercially available cells and whether the cells have been cryopreserved. This can impact how long it takes for the cells to form a tight monolayer before the ALI can be established. Once the cells have been air-lifted, it typically takes 3-4 weeks for a fully differentiated pseudostratified epithelium to be generated. The culture media and permeable support coating can also impact this timing. For example, when using human airway epithelial cells at the air liquid interface (ALI) on collagen I-coated Transwell inserts using Stemcell Technologies’ Pneumacult Ex plus and Pneumacult ALI medium, a fully differentiated pseudostratified epithelium is generated in 4-5 weeks.
As to how long can you keep the model viable in culture again it will depend on the cell type and source. For example, commercially available ALI models can have a long lifetime (3–12 months). Long term maintenance of the cultures relies on regular media changes and the use of good aseptic technique to ensure that contamination is not introduced. Examples of commercial ALI human airway models include EpiAirway developed by MatTek Corporation, and OncoCilAirTM and MucilAirTM from Epithelix.
This information is specific to air-liquid interface culture of airway epithelial cells on permeable supports. Organoid models are also increasingly being used to model the human airway. References for organoid airway models can be found here.