Menstrual cycle–related sialidase activity of the female cervical mucus is associated with exosome-like vesicles

ObjectiveTo study endogenous sialidase activity in genital tract secretions of pregnant and nonpregnant women.DesignLaboratory study.SettingDepartment of Evolutionary Biology and Department of Obstetrics and Reproductive Medicine, University of Siena, Siena, Italy.Intervention(s)Vaginal and cervical mucus samples were obtained from pregnant and nonpregnant women in different phases of the menstrual cycle and in different weeks of pregnancy.Main Outcome Measure(s)Sialidase activity was assessed by fluorimetric assay and localized by transmission electron microscopy and differential centrifugation.Result(s)Sialidase activity in cervical mucus of healthy women reaches a maximum in the ovulatory phase. Cervical mucus from pregnant and nonpregnant women had significant sialidase activity that was associated with membranous vesicles having an exosome-like structure.Conclusion(s)Female cervical mucus contains an endogenous menstrual cycle–related sialidase that could be involved in modifying the rheologic properties of mucus to favor sperm progression at fertilization. Its association with exosome-like vesicles also suggests a role in intercellular communication before and after fertilization.