The oviduct as a complex mediator of mammalian sperm function and selection

Abstract

SUMMARYThe fallopian tube, or oviduct, is no longer considered merely a conduit that joins the uterine horns and the ovaries, being recognised as a venue for the capacitation of spermatozoa and fertilisation. However, recent evidence has implicated the oviduct in the stringent selection of spermatozoa prior to fertilisation, sperm storage prior to fertilisation, the regulation of sperm motility and possibly the guidance of spermatozoa towards the egg. Moreover, the arrival of spermatozoa within the oviduct is now known to regulate gene expression in oviductal epithelial cells with the consequent up-and downregulation of various proteins. In this review, we examine the emerging significance of spermoviduct interactions, as they relate to both physiological functions and the likelihood that the oviduct has a role in post-copulatory sperm selection by females (cryptic female choice) under conditions of sperm competition. The mechanisms by which sperm selection might operate still remain a mystery, especially when the underlying rationale for such mechanism appears to require the recognition by the female tract of sperm qualities related to the intrinsic integrity and information content of the sperm DNA. The oviduct not only selects against spermatozoa containing fragmented DNA but also imposes selection related to the fitness or quality of individual males. This implies the existence of, as yet unrecognised, mechanisms for the detection and interpretation of sperm-surface markers that link phenotypic and genotypic qualities of each individual cell.Mol.

Sperm surface changes and physiological consequences induced by sperm handling and storage

“…(D) When spermatozoa reach the upper portion of the female genital tract (the isthmus of the oviduct), they are triggered to capacitate. The mechanisms are unknown but it is thought that migration of spermatozoa through the uterus and the uterotubal junction causes the removal of decapacitation factors (orange) and that spermatozoa respond to female-derived stimulatory signals (Holt & Fazeli 2010). In vitro, this response is elicited after density gradient washing (which strips decapacitation factors originating from the epididymis and accessory sex glands from the sperm surface) and incubation with capacitation factors such as bicarbonate and albumin.…”

“…In vivo, spermatozoa undergo extreme selection because only a small number of competent spermatozoa are able to cross the uterotubal junction and interact with the epithelium of the oviduct (Sostaric et al 2008, Suarez 2008, Holt & Fazeli 2010, Ikawa et al 2010. It is not well understood how these cells achieve capacitated properties but it is believed that initiation of the process precedes release from oviductal epithelial cells (Lefebvre & Suarez 1996, Fazeli et al 1999) and may be triggered by specific oviductal fluid factors that are released on the initiation of ovulation (Overstreet et al 1978, Hunter 2008, Sostaric et al 2008.…”

Who's My Daddy? Considerations for the influence of sexual selection on multiple paternity in elasmobranch mating systems

“…For instance, in a population of fowl ( Gallus gallus domesticus ) where females are coerced into mating with subordinate males, females were found to differentially expel sperm from males based on their social rankings (Pizzari & Birkhead, 2000). Alternatively, studies in mammals have implicated sperm–female reproductive tract interactions as playing a role in sperm selection by females (Holt & Fazeli, 2010). Given the various opportunities between mating and fertilization afforded to females to exert mate choice as seen in other vertebrate taxa, it would be surprising if elasmobranch females have no mechanism to control male fertilization success.…”

Characterization of electrical and mechanical activities of rabbit uterus associated with the presence of capacitated and non-capacitated spermatozoa

“…In this research, a significant correlation between contractility and electric activity was detected at the UTJ under the influence of capacitated spermatozoa only; regardless of the short time that spermatozoa were allowed to establish an interaction with oviductal epithelial cells, it seems that capacitated spermatozoa were able to modify the uterus activity. The UTJ is certainly critical for blocking the entry of already-capacitated spermatozoa, so it could be that capacitated spermatozoa are making some kind of stimulation that would preferentially block the UTJ (Holt and Fazeli, 2010). When considering these results, one should bear in mind the effects of acepromazine on uterine muscle, which may modify its mechanical and electrical activity; although this drug has adrenergic antagonist effects that can reduce uterine contractility (Katila, 2007), we were able to detect some small changes on uterus activity provoked by seminal plasma and capacitated spermatozoa.…”