Accumulation, Storage, and Release of Sperm in the Oviduct

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Project Summary Fertility depends on successful fertilization and early development, processes that occur in the oviduct. Common therapies for human infertility, such as in vitro fertilization and intracytoplasmic sperm injection, are expensive and increase risks of a variety of problems. More knowledge of how the oviduct interacts with sperm, the cumulus-oocyte complex (COC) and the developing embryo may improve fertility and reduce the need for therapies. The oviduct serves as a reservoir for sperm, after semen deposition and before fertilization. Binding to the oviduct maintains sperm viability and suppresses motility. Sperm are released to move to the upper oviduct (ampulla) to fertilize oocytes. There are many gaps in this model of sperm-oviduct interaction. Our studies have begun to fill some of these gaps. We have used a glycomic approach to screen 377 glycans and found that all glycans with affinity for porcine sperm have either of two motifs, sulfated Lewis X trisaccharide or branched 6-sialylated complex glycans. Remarkably, if these glycans are immobilized on beads or microscope slides, they can extend sperm lifespan, much like binding to oviduct cells prolongs the lifespan of sperm. We have identified two candidate receptors for both glycans on the sperm membrane, PKDREJ and ADAM5. Notably, mouse sperm deficient in PKDREJ and other ADAMs do not accumulate beyond the utero-tubal junction, but it is not known if this is due to a problem in binding and retention in the oviduct. To determine if these candidate receptors are required for sperm binding to oviduct cells and for fertility, we have produced swine with indels in both PKDREJ and ADAM5. Production of these animals by the NIH-funded National Swine Research and Resource Center was supported by an administrative supplement that was funded just after the COVID-19 pandemic started so production was delayed due to NSRRC lab and abattoir shut-downs. We finally obtained the animals in Sept/Oct of 2021. We received a No Cost Extension to study the animals but unfortunately, all the gene-edited ADAM5 animals were female so additional breeding is required to produce homozygous gene-edited males. Funding from the original RO1 is now depleted so we are unable to complete the studies of PKDREJ-edited males. The goal of this administrative supplement is to preserve these unique genetic resources for further study. I recently submitted a renewal of the original RO1 proposal that will include studies of these gene-edited animals. The Specific Aim is to cryopreserve semen from males, embryos from females, and somatic cells from all animals with indels in ADAMA5 and PKDREJ genes. This preserved genetic material can be used for artificial insemination, for embryo transfer, and for somatic cell nuclear transfer to produce animals for study in the RO1 renewal.