Selective sperm binding to pig oviductal epithelium in vitro

Abstract

The sperm reservoir in the caudal isthmus of the oviduct of a number of species is created by binding of spermatozoa to oviductal epithelium. The sperm reservoir fulfills a number of functions such as control of sperm transport, maintenance of sperm viability and modulation of capacitation. The initial capacities of ejaculated and epididymal boar spermatozoa to bind to oviductal epithelium were investigated using a modified pig oviductal explant assay. The number of spermatozoa that bound to 0.01 mm(2) of explant surface was used as the parameter of binding capacity. Binding of spermatozoa to oviductal epithelial explants was dependent in a linear manner on the number of spermatozoa added (P < or = 0.05). No difference was found in initial sperm binding between isthmic and ampullar explants. There was no effect of the stage of the oestrous cycle or the reproductive status of the female donor. There was a significant effect (P < or = 0.05) of the individual boar on the binding index. The binding index correlated negatively with the percentage of spermatozoa with cytoplasmic droplets and the percentage of morphologically abnormal spermatozoa (P < or = 0.05). Epididymal spermatozoa showed significantly lower initial binding capability than did ejaculated spermatozoa from the same boars (P < or = 0.05); therefore, components of seminal plasma may play a role in the binding process. The individual differences revealed by this study and their relation to morphology and contact of spermatozoa with seminal fluid indicate a selective function of sperm-oviduct binding.

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

“…The number of caudal spermatozoa however, that bind to oviductal explants in the pig is about half that of ejaculated spermatozoa [11], which is consistent with results obtained in this current study. This suggests that seminal plasma must contain factors, including prostasomes that further enhance oviduct binding in these otherwise structurally mature spermatozoa.…”

“…The semen was shipped in a polystyrene esky with an ice pack and usually arrived at the laboratory the day before an experiment was undertaken. Before use, the semen was examined for motility and concentration using a computer-aided semen analyser (CASA) (Hamilton Thorne Research, Beverly, MA, USA) and was directly diluted to 5 x 10 6 spermatozoa per ml with modified Androhep solution (pH 7.4 and 290 mOsm/kg) containing 144.0 mM glucose, 27.2 mM tri-sodium citrate-2-hydrate, 14.3 mM sodium bicarbonate and 37.0 mM HEPES in Nano-Pure deionised water [11].…”

“…The procedures were modified from Petrunkina et al [11] and Wagner et al [25]. Oviducts were obtained from gilts slaughtered at an abattoir in Charters Towers, about 130 km from James Cook University, Townsville.…”

“…Compared to ejaculated spermatozoa, epididymal spermatozoa from the boar show a reduced ability to bind to oviduct epithelium in vitro [11]. However, it is still largely unknown where and when spermatozoa develop this ability to bind to oviductal epithelium and hence form the sperm reservoir.…”

The epididymis, cytoplasmic droplets and male fertility

“…12,75 Flagellar angulation occurs at the site of the cytoplasmic droplet, as it does in the infertile mice, proving that the ejaculated spermatozoa had retained their droplets. The infertility of spermatozoa with droplets has been suggested to reflect poor adherence to the zona pellucida (cows 72 ) and the oviductal epithelium (sows 76,77 ). As spermatozoa with retroflected flagella swim 'backwards' (head against the direction of travel 78 ), it is equally likely that their passage through mucus or the uterotubal junction is hampered and the oocyte is never reached, as is the case for the c-ros KO mice.…”