Culture of bovine oviduct epithelial cells (BOEC)

Bovine oviduct epithelial cells are widely used in co-culture experiments to improve early embryonic development and in vitro fertilization in embryo transfer programmes for domestic animals.

The present study compares different methods for harvesting and culture of bovine oviduct epithelial cells in order to optimize handling. Bovine oviduct epithelial cells were mechanically or enzymatically isolated and cultured on glass, on permeable membranes, or in suspension. Growth of the cells and their state of differentiation was examined by means of classical staining methods, immunohistochemistry and electron microscopy.

Initial cell suspensions contained sheets of ciliated and nonciliated (secretory) cells; 24 h after seeding, free floating epithelial cells formed vesicles with cilia on their external surface. First adhesion of cells was seen 72 h after seeding. Later on, cells grew continuously and confluent monolayers were formed after 7 days. Results were identical after mechanical or enzymatical cell harvesting and were identical on both substrata tested, i.e., on glass and on permeable membranes. Light and electron microscopy proved the monolayers to resemble a polarized, simple, cuboidal to columnar epithelial membrane with intact junctional complexes and numerous apical microvilli. Their epithelial nature was established by immunostaining for cytokeratins. Cilia were missing and secretory granules were scarce. A layer of acidic glycoprotein material was demonstrated on the apical surface. Monolayers of bovine oviduct epithelial cells stored lipid droplets and large quantities of glycogen. About 50% of the seeded cells did not adhere but survived in the culture medium as free floating cells. These suspended cells maintained morphological criteria of differentiation (cilia and secretory granules) until day 12 of culture. Proliferation rates of cultivated cells were determined by counting mitoses and by immunostaining with MIB1 antibody. Results showed coincidence of rapid proliferation and morphological dedifferentiation of monolayers. Suspended cells, by contrast, did not proliferate but retained cellular differentiation under identical culture conditions.

The results strongly suggest that monolayers of bovine oviduct epithelial cells will not fully substitute for original oviduct epithelium when used in co-culture experiments after in vitro fertilization.