The interaction of fresh and frozen-thawed ram spermatozoa with oviducal epithelial cells in vitro

Abstract

In order to investigate the interaction of fresh and frozen–thawed spermatozoa with oviduct epithelial cells, spermatozoa were co-incubated with ovine oviduct epithelial cell monolayers (OECM) derived from either complete oviducts, at any stage of the oestrous cycle (Experiments 1 and 2), or from different regions of the oviduct at different stages of the cycle (Experiment 3). Fresh and frozen—thawed spermatozoa displayed different patterns of binding to, and release from, the OECM. Frozen—thawed spermatozoa immediately bound to the complete oviduct OECM and were released after 2 h. A small proportion of fresh spermatozoa bound immediately, increasing to a maximum after 2 h, and were gradually released thereafter. When only the cells that were released from the OECM were observed by chlortetracycline staining in Experiment 2, it was found that the presence of an OECM increased the number of capacitated fresh spermatozoa while decreasing the number of capacitated frozen–thawed spermatozoa. Overall, the OECM advanced the membrane state of both types of spermatozoa from uncapacitated to acrosome-reacted. Fresh and frozen—thawed spermatozoa bound to OECM derived from the cells of the isthmus and the ampulla in similar proportions. However, more spermatozoa were capacitated when incubated with OECM derived from isthmic rather than ampullary cells. Higher proportions of fresh spermatozoa bound to, and were acrosome-reacted following incubation with OECM derived from post- rather than pre-ovulatory tracts. Such differences were not observed for frozen—thawed spermatozoa. The findings reported in this study show that fresh and frozen—thawed spermatozoa behave differently when in contact with oviduct cells in vitro. This may be a consequence of the more advanced membrane state of the frozen spermatozoa upon thawing.