The oviduct exerts a profound effect on sperm motility prior to fertilization. In several mammals, including cattle, sperm are sequestered in the caudal, or lower, oviduct. During the period surrounding fertilization, sperm gradually ascend to the ampullary region of the oviduct and their motility is hyperactivated. These phenomena have been studied indirectly in large mammals and directly, but to a limited extent, in the mouse. An in vitro system would be extremely useful to examine the endocrinological, physiological, and biochemical mechanisms governing these phenomena. The purpose of this project is to establish an in vitro system for studying the interaction of mammalian sperm with oviductal epithelium, and to ascertain the effect of epithelial secretions upon sperm motility. Four functionally distinct regions of bovine oviduct will be cultured in vitro: the uterotubal junction, the caudal isthmus, the cephalic isthmus, and the ampulla. The effect of the hormonal conditions of the estrous and periovulatory periods on the cultured tissue will be examined by electron microscopy, especially to establish the morphological integrity of the tissue. In the oviduct, these are the critical periods for sperm transport, storage, capacitation, and fertilization. In the second phase of the project, sperm will be co-cultured with the tissue. Observations will be made on sperm interaction with the tissue, such as adherence to isthmic epithelium, suppression of motility by tissue from the caudal isthmus, and hyperactivation of motility by tissue from the cephalic isthmus and ampulla. The role of the hormonal environment will also be examined. Finally, the effect of culture supernatants on sperm behavior will be observed, with the long term goal of identifying factors responsible for such phenomena as hyperactivated motility and motility suppression. In addition to allowing the study of sperm transport and motility, the development of an in vitro system of co-culturing sperm with oviductal tissue could be utilized in the study of sperm capacitation and fertilization.
