Epsilon Open Archive

Abstract

Fundamental reproductive events such as sperm storage and capacitation, fertilization, and early embryo development occur in the oviduct (tuba uterina), processes in which glycosaminoglycans (GAGs) and their binding proteins are involved. An intriguing feature of the oviduct is the suppression of the rejection of parentally derived foreign proteins by the female, which, in some other organs relates to the presence of a Fas-Fas ligand (Fas-FasL) system. The aim of this thesis was to study the intra-luminal milieu of the bovine oviduct, (i) its contents of GAGs in the epithelium and oviductal fluid, (ODF), involving the non-sulphated hyaluronan (HA), its binding proteins, including the HA receptor CD44, and sulphated GAGs (S-GAGs), also in the form of proteoglycans, during well-defined stages of the oestrous cycle and specific anatomical regions; (ii) the capacitation status of bull spermatozoa submitted to incubation with ODF, GAGs, and bicarbonate and, (iii) the presence of Fas and FasL in the tube. The results revealed that HA and its receptor CD44 were abundant in the epithelium of the sperm reservoir (SR) independently of the oestrous cycle stage or pregnant status. The ODF contained HA and S-GAGs during all stages of the oestrous cycle. The ODF concentration of S-GAGs in the ampulla was significantly higher than in the isthmus. There was also a significantly higher concentration of S-GAGs in the oviduct ipsilateral to ovulation. Both ODF and bicarbonate elicited bull sperm capacitation in vitro. The capacitation response to the GAGs was weaker than that to ODF or bicarbonate. Hyaluronan and dermatan sulphate were the only GAGs that significantly enhanced capacitation. Fas and FasL were detected in the tubal epithelium, and FasL in the ODF. The localization of HA and CD44 to the epithelium of the bovine oviductal SR suggests their involvement in sperm preservation during pre-ovulatory tubal storage. Although GAGs in ODF may contribute to sperm capacitation, there may be more factors in ODF modulating the process, such as bicarbonate. The presence of Fas and FasL in the bovine oviduct may lay the basis for the immune privileged status of this organ and mediate survival of spermatozoa and early embryos.