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

Objective: To study endogenous sialidase activity in genital tract secretions of pregnant and nonpregnant women.

Design: Laboratory study.

Setting: Department 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.