Characterization of a polarized porcine uterine epithelial model system.
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A porcine uterine epithelial cell (pUE) culture system that retains structural and functional properties of the surface epithelium in vivo was developed. Uterine luminal epithelial cells were isolated after pancreatin-dispase enzymatic release of epithelium from hysterectomized gilts. Cells were seeded on Millicell filters precoated with Matrigel in 24-well plates and subsequently allowed to proliferate to confluence. Purity of the isolation was confirmed by the presence of > 99% cytokeratin-positive cells. Epithelial cells became polarized in vitro and compared favorably in morphology to uterine epithelial cells in situ once a transepithelial resistance of > 600 omega cm2 was established. Microscopic analysis confirmed the presence of a simple columnar epithelium with prominent microvilli on the apical cell surface and a well-developed junctional complex containing tight junctions, belt and spot desmosomes, and interdigitating lateral cell processes. Indirect immunofluorescence of the tight junction-associated protein, ZO-1, indicated the formation of tight junctional complexes in the subapical region of the polarized cells. Functional polarity of epithelial cultures was also verified by 1) electrical resistance measurements, 2) basal preference for the secretion of prostaglandins F2 alpha and E2, 3) apical preference for the release of 35S-methionine-incorporated secretory proteins, and 4) apically and basally distinct secretory protein profiles. Steroid treatment (estrogen, progesterone, or estrogen plus progesterone) of the polarized pUE cells affected the release of radiolabeled methionine-incorporated secretory proteins. In addition, the protein profiles as compared to samples treated with fetal bovine serum or charcoal/dextran-stripped fetal bovine serum were altered. Steroid treatments did not alter the electrical resistance or the basal preference for prostaglandin secretion. This culture system may be useful for in vitro analysis of maternal recognition of pregnancy paradigms as well as the study of the direct actions of hormones, prostaglandin secretion, and epithelial-stromal interactions.