Production of Glycosaminoglycans by the Porcine Oviduct in Relation to Sperm Storage

Abstract

ContentsFollicular and oviductal fluids have shown modulatory effects on sperm capacitation of boar spermatozoa in vitro, implicating glycosaminoglycans (GAGs) in the process. Capacitation in pigs is believed to occur in vivo during storage in the sperm reservoir, where spermatozoa maintain viability and membrane stability awaiting ovulation. Exposure to the nonsulphated GAG hyaluronan induces capacitation in vitro (chlortetracycline‐monitored) without eliciting acrosome exocytosis, indicating that it exerts a protective role on sperm viability. Oviductal fluids (isthmus and ampulla) of cycling sows were collected in vivo to disclose temporal changes in concentrations of both sulphated and nonsulphated GAGs between late pro‐oestrus and meta‐oestrus. Further, heparan‐sulphate and hyaluronan were immunohistochemically localized in the oviductal tissues of uninseminated and inseminated sows, around the period of ovulation. Concentrations of sulphated GAGs were two‐fold higher than hyaluronan. All tubal GAGs increased significantly from late pro‐oestrus and were highest during the pre‐ovulatory period before beginning to decrease postovulation, the exception being the ampullar hyaluronan, whose levels remained high towards meta‐oestrus. Heparan sulphate (syndecans) and hyaluronan were both immunohistochemically detected in the endosalpinx. Syndecan‐immunolabelling was present in the epithelium and stroma along the tube, whereas hyaluronan was always localized in the lamina propria and most of the lining epithelium was negative, during the stages studied. The only exception was the sperm reservoir (deep crypts and furrows of the Utero‐tubal Junction UTJ/isthmus) where sperm clusters were seen close to the epithelial HA‐immunolabelling in the inseminated sows, but only pre‐ovulatory. The presence of GAGs in the tubal fluid and the conspicuous location of hyaluronan suggest they play a role in the formation and function of the sperm reservoir.