Ram spermatozoa cocultured with epithelial cell monolayers: an in vitro model for the study of capacitation and the acrosome reaction.

The effects of different epithelial cells, namely, hamster oviduct, sheep oviduct, and pig kidney epithelial cells (IBRS-2), on the viability, percentage of progressive motility (PPM), and acrosome reactions of ejaculated ram spermatozoa were investigated. Sperm aliquots were cultured on cells, cell-conditioned medium 199, or control medium 199. The PPM of unattached spermatozoa was estimated after 0, 3, 6, 9, 12, and 24 hr of incubation at 37 degrees C under 5% CO2 in air. Viability and the occurrence of true acrosome reactions were assessed using a triple-stain technique. Spermatozoa started to attach within 1 hr of coculture with the hamster or sheep oviductal epithelial cell (OEC) monolayers, and these spermatozoa showed vigorous tail motion. No spermatozoa were found to attach to the IBRS-2 monolayer. The PPM of unattached spermatozoa cocultured with the various types of epithelial cell monolayers for 12 hr was significantly higher than that of spermatozoa incubated in conditioned media or medium 199 alone (54% in hamster OEC vs. 40% in conditioned; 68% in sheep OEC vs. 38% in conditioned; 36% in control medium). On the other hand, after 24 hr of incubation, there were no differences in the PPM of spermatozoa cocultured with epithelial cells or incubated in conditioned media. The percentages of cells undergoing a true acrosome reaction reached maximum values (P < 0.05) in spermatozoa incubated for 9 hr in the presence of hamster OEC (22.5%) or for 12 hr on sheep OEC (20.5%) monolayers.(ABSTRACT TRUNCATED AT 250 WORDS)