Interaction of Equine Spermatozoa with Oviduct Epithelial Cell Explants is Affected by Estrous Cycle and Anatomic Origin of Explant1

Abstract

Regulation of attachment of equine spermatozoa to homologous oviduct epithelium was investigated by co-culture of spermatozoa with oviductal epithelial cell explants. Stallion spermatozoa were incubated with explants derived from the isthmus and ampulla of follicular, postovulatory, and diestrous mares. Steroid treatments (estradiol, progesterone, or control) were applied across all explant groups. Estimates of motility and total numbers of attached spermatozoa were made 0.5, 24, and 48 h after initiation of co-culture. Equine spermatozoa attached by their rostral acrosomal region to both ciliated and nonciliated oviduct epithelial cells. Steroid treatment had no effect on either motility or total number of attached spermatozoa. Motility of spermatozoa attached to ampullar and isthmic explants did not differ. However, at both 24 h and 48 h, motility of spermatozoa attached to follicular-stage explants exceeded that of spermatozoa attached to postovulatory or diestrous-stage explants (p < 0.05). The number of spermatozoa that bound to explants was affected by stage of cycle, anatomic origin of explant, and time in co-culture (p < 0.001), as well as the interaction of cycle stage, anatomic origin, and time in co-culture (p < 0.001). More spermatozoa bound to explants of isthmic than ampullar origin, and more spermatozoa bound to follicular and postovulatory explants than to diestrous explants (p < 0.05). These data support the existence of a spermatozoal reservoir in the oviductal isthmus of the mare and suggest that there may be cycle stage-specific regulation of both motility and the number of spermatozoa attached to oviductal epithelium.

Oviduct binding ability of porcine spermatozoa develops in the epididymis and can be advanced by incubation with caudal fluid

“…A similar observation has been made by other workers in pigs [11] and in the horse [56]. These differences imply that individual variation in the level of fertility between boars could be attributed to the number of spermatozoa that form the sperm reservoir.…”

“…Moreover, spermatozoa from the horse and human have also been reported to bind in greater numbers to the isthmus than to the ampulla [56,57]. It is important to realise that regional differences in the expression of glycoconjugates are apparent between segments of the porcine oviduct, and across the different stages of the oestrous cycle, thereby affecting the available binding sites [58].…”

Distribution of sialoglycoconjugates in the oviductal isthmus of the horse during anoestrus, oestrus and pregnancy: a lectin histochemistry study

“…In horse, asialofetuin blocks the binding of sperm to the oviductal epithelium by means of its terminal galactose residues (Lefebvre, 1995;Dobrinski et al 1996).The sialylglycoconjugates contained on the luminal surface of non-ciliated cells seem to belong mainly to O-linked oligosaccharides (mucyn-type glycans) that are typical secretory moieties and contain more complex and heterogeneous carbohydrates than N-linked types (Fukuda, 1994). The differences in the isthmus distribution of O-linked oligosaccharides during the investigated stages may be related to the existence of a cycle-specific regulation of the spermatozoa attachment to the oviductal epithelium of horse (Thomas et al, 1994). It has been proposed that, in other mammals, O-linked glycans are involved in a variety of biological phenomena including in vitro sperm capacitation (Banerjee and Chowdhry, 1994;Focarelli et al, 1995), a selective barrier to sperm transport, modulation of sperm ascent to the site of fertilization (DeSouza and Murray, 1995) and sperm-egg interaction (Geng et al, 1997;Tulsiani et al, 1997).…”

“…Each one of these regions is involved in specific biological events. The isthmus is considered to be a spermatozoal reservoir for several species such as cattle (Suarez et al, 1990;Hunter et al, 1991), hamsters (Smith and Yanagimachi 1991;Smith et al, 1991), mice (Suarez, 1987), pigs (Hunter 1981;Suarez et al, 1991), rabbits (Oversteet et al, 1978), sheep (Hunter and Nichol, 1983), and horses (Thomas et al, 1994;Dobrinski et al, 1996). The isthmic region of the oviduct represents a unique biochemical milieu able to i) prevent polyspermic fertilization, ii) maintain the fertility of sperm, and iii) regulate capacitation and motility hyperactivation in order to ensure the effective condition of sperm when ovulation occurs (Suarez, 2002).Thus, the role of the isthmus appear to be of utmost importance in horses where the fertilization may occur up to 6 days after mating (Day, 1942;Burkhardt, 1949) As in other species (Suarez, 2002), equine sperm binding to oviductal epithelium is established by interactions between oligosaccharides of cell surface-associated glycoproteins (Lefebvre et al, 1995;Dobrinski et al, 1996).…”

Induction of Dog Sperm Capacitation by Oviductal Fluid.

“…In spite of this long delay, a single mating can be fertile even when it occurs on the first day of estrus. Therefore, it appears that the fertile life of canine sperm must be maintained for at least 5 days in the female reproductive tract.There is evidence that the oviduct has the function to store sperm [27] and to maintain sperm viability [7,16,37] until the time of ovulation and fertilization. The ewe [5], pig [35], rabbit [4], hamster [18] and mouse [26] have been found to have high rates of freely swimming (FS) sperm exhibiting star-spin-like active movement or vigorous flagellar movement called "hyperactivation" in their oviducts.…”