In Vitro Excised Models

Excised nasal mucosae obtained from various animal species are tools frequently used to study nasal transport and metabolism ([53], Chap. 4). Maintaining the viability of the excised nasal tissues during the experimental period is crucial. Most studies were performed with epithelia excised from rabbits, bovine, sheep, and dogs tissues [54-57], This excised nasal tissue model has been shown to be well suited for studies on nasal permeation and metabolism of drugs. However, species differences in the activity of various enzymes found in human versus these animal nasal mucosae have become an important issue. 

RPMI 2650 is the only human nasal epithelial cell line derived from a spontaneously formed tumor. This particular cell line has been mostly used for nasal metabolism studies, since it grows into a multilayer and does not form confluent monolayers (although perijunctional actin rings are present). Thus, RPMI 2650 cell monolayer is rarely used for nasal transport studies [44, 58], 

In Vitro Primary and Passaged Cell Culture Models 

Because mucin and/or cilia systems of AIC cultured epithelial cells may work as a barrier for drug transport, lower Papp values are expected in cell layers cultured in AIC than in LCC methods. However, it was interesting to note that no significant differences in Rapp values were observed between the cell layers cultured with the two methods (Table 9.1). This is in contrast to solute permeabilities reported previously for cell layers cultured with LCC versus AIC methods [76, 80], For example, Yang et al. reported that Rapp of lipophilic solutes (e.g., various /3-blockers) across the primary cultured conjunctival epithelial cell layer are about threefold lower when cultured under AIC than LCC conditions, suggesting that the permeability of AIC cultured cell layers generally better reflects that of the excised tissue than LCC counterparts. Mathias et al. [76] also reported that the permeability of hydrophilic solutes across the primary rabbit tracheal epithelial cell layer cultured under AIC conditions was only half of that observed for cell layers cultured under 

Source Data from Ref. [46]. AIC, Air-interfaced culture. LCC, Liquid-covered culture. 

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