Effects of human oviductal in vitro secretion on spermatozoa and search of sperm–oviductal proteins interactions

Abstract

It has been suggested that oviductal proteins could be involved in modulating sperm function and fertilizing ability through as yet not well-known mechanisms. The objective of the study was to investigate the pattern of proteins secreted by human oviductal tissue cultures and the effects of their conditioned media (CM) on sperm function under capacitating conditions and in phosphate buffered saline (PBS). In addition, interactions between spermatozoa and oviductal proteins were examined. The oviductal tissue was obtained from pre-menopausal patients scheduled for hysterectomies because of uterine fibromyoma. Normozoospermic semen samples were obtained from healthy donors. Cultures of human fallopian tissue were carried out and CM were collected for analysis of the de novo production of [35S]-methionine-labelled proteins by SDS-PAGE. Motile spermatozoa were incubated under capacitating conditions and in PBS, with or without CM, and sperm fertilizing ability was assessed by ionophore-induced acrosome reaction (AR) and the acrosome reaction to ionophore challenge (ARIC) score. The ionophore-induced AR was evaluated by the Pisum sativum technique. Sixteen de novo produced proteins were detected in CM. One of these proteins (molecular weight 79 kDa) was detected in extracts from spermatozoa pre-incubated with CM. Sperm survival and motility were maintained in the presence of CM, although results showed a significant decrease in ARIC score (p < 0.05), with respect to controls. The presence of CM significantly decreased sperm fertilizing ability, without affecting sperm survival. These results suggest that the oviductal secretion could contribute to preserve sperm viability and motility, and to prevent a premature response of spermatozoa to AR inducers.