Objective: 

Forestomach epithelia of ruminants have an extensive absorptive capacity for products of bacterial fermentation, such as short chain fatty acids. At the same time, their barrier properties allow the maintanance of steep ionic gradients between lumen and blood. Forestomachs are lined by cornified stratified squamous epithelia that differentiate from the homogenous cells of the stratum basale. It was the aim of the study to develop a cell culture model to facilitate investigation of both transport and barrier properties of these epithelia.

Methods: 

Cells of the stratum basale of sheep forestomach epithelia were isolated using fractional trypsinization, seeded onto filter supports and cultured to confluence. Cell layer properties were characterized and compared to native epithelia, using molecular biological, immunohistochemical and electrophysiological techniques.

Results: 

Confluent cell layers developed transepithelial resistances, reaching plateau values in the order of 1000 W×cm² after 5 to 7 days. Confocal laser microscopy revealed a frequently multilayered structure with expression of occludin and claudins 1, 4 and 7, whereas claudins 2, 5, 8 and 10 were not expressed. Native tissues expressed the same tight junction proteins. Their identity was verified by Western Blot and PCR. Preliminary flux studies indicated that all layers from stratum basale to stratum granulosum act as a barrier, with an additional barrier located within the stratum granulosum, near the apical side of the epithelium.

Conclusions: 

Cells isolated and cultured from ruminant forestomach tissue grow into tight cell layers that mirror barrier properties of the native tissue.