| Summary: | The female reproductive tract acts not only as a complex mediator of sperm function and selection but animal data suggests that it alters protein expression after exposure to sperm, implying two-way communication. We have used single-cell fluorescence imaging to observe [Ca2+]i signalling in human female reproductive tract cells upon initial contact with sperm and in sperm during binding and release events. Parallel experiments were also performed on a model human oviductal cell line, OE E6/E7 and a control, human foreskin fibroblasts. Upon exposure to sperm, tract cells generated [Ca2+]i signals through mobilisation of thapsigargin-sensitive intracellular Ca2+ stores. The percentage of significant [Ca2+]i responses varied in different anatomical regions of the female tract. Furthermore, [Ca2+]i signalling was observed upon exposure to sperm-conditioned media suggesting signalling factors may be shed or secreted by sperm. Human foreskin fibroblasts were unresponsive to sperm. Co-culture of sperm with tract explants induced post-translational modification of sperm proteins through NO-dependant S-nitrosylation. We have also provided initial evidence for [Ca2+]i alterations in sperm during binding to and detachment from oviductal explants. We conclude that sperm can elicit [Ca2+]i signals in female tract cells upon initial contact though mobilisation of intracellular Ca2+ stores. This may reflect events upstream of reported gene and protein expression changes. In addition, human sperm interaction with oviductal epithelium is likely to be important in modulating sperm function during migration and associated events through the female reproductive tract.
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