Purpose: To determine whether cultured rabbit corneal epithelial cells (RCEC), grown on permeable supports, provide a suitable in vivo model for characterizing transcellular drug permeation and metabolism.
Methods: Primary rabbit corneal epithelial cells grown in DMEM-F12 were seeded on Transwell-COL inserts coated with fibronectin. The epithelial barrier integrity was evaluated, based on measurements of 14C-mannitol and 3H-PEG900, and their transepithelial electrical resistance (TEER). Ultrastructure evaluation was based on scanning electron microscopy and transmission electron microscopy, which were performed 8 days after seeding. Measurements of beta adrenergic antagonist permeability were performed to assess transcellular permeability.
Results: Eight days after seeding, the TEER reached a peak of 144 omega.cm2 and the 14C-mannitol and 3H-PEG900 permeabilities were 6.8 x 10(-6) and 2.9 x 10(-6) cm/sec, respectively. Ultrastructural analysis revealed a multilayered structure with numerous microplicae and typical cytoplasmic organelles along with desmosomes. The relationship between permeation of beta-blockers and lipophilicity resembled the intact isolated cornea.
Conclusions: This is the first description of cultured RCEC grown on permeable support. Many of its properties mimic those described in the intact corneal epithelium. Even though its electrical tightness is less than that of the intact cornea, the transcellular permeability to lipophilic beta-antagonists is comparable to the isolated preparation. Therefore, this model will facilitate characterization of ocular permeation mechanisms of hydrophobic drugs whose route of permeation is transcellular.