Roles of the reproductive tract in modifications of the sperm membrane surface

Abstract

Successful fertilization requires viable and functional spermatozoa to recognize and fuse with the oocyte. In most mammalian species, mature spermatozoa are not capable of fertilizing the oocytes immediately after ejaculation. However, unlike somatic cells, spermatozoa, after leaving the testis, are transcriptionally and translationally silent; therefore, upon completion of spermiogenesis, spermatozoa carry only a minimal amount of essential proteins on their membranes as well as within their restricted volume of cytoplasm. To develop into a fully functional and competent sperm that is capable of successful fertilization, modifications of the sperm membrane surface during its transit in the reproductive tracts is critical. These post-spermatogenesis modifications advance the maturation of epididymal spermatozoa. In addition, components secreted into the lumen of the reproductive tracts that are later added onto the sperm membrane surface also regulate (inhibit or activate) the functions of the spermatozoa. This acquisition of additional proteins from the reproductive tracts may compensate for the inactivity of morphologically mature spermatozoa. In this review, we discuss the contributions of the male and female genital tracts to modifications of the sperm membrane surface at different stages of fertilization.

Flow cytometry analysis of spermatozoa: Is it time for flow spermetry?

“…Classical tests evaluate the physical integrity of the plasmalemma, being the combination of SYBR‐14/PI one of the most widely used (Garner, Thomas, & Allen, ). However, the plasma membrane is much more than an inert envelope (Tapia et al., ), being actively involved in critical sperm functions, that imply, among many others, the recognition of specific receptors in the female genital tract, or in the egg, activation of channels, changes in fluidity, permeability, and fusogenicity (Flesch & Gadella, ; Kuo, Li, Maeda, Gadella, & Tsai, ; Leahy & Gadella, ; Tsai, Garcia‐Gil, van Haeften, & Gadella, ; Tsai, van Haeften, & Gadella, ). These changes have to occur at specific intervals and in specific regions of the female genital tract to lead to a successful fertilization.…”

Reproductive tract modifications of the boar sperm surface

“…Sperm maturation in the epididymis takes approximately 2 weeks in boars, and transits the sperm form caput to cauda regions of this organ (Dacheux et al, ). Substantial rearrangement of the sperm surface is accomplished during this process, resulting in (i) removal of the cytoplasmic droplet; (ii) a change in metabolism, which allows for sperm to acquire motility; and (iii) removal and adsorption of peripheral proteins on the sperm surface (Guyonnet et al, ), which are particularly relevant to fertility as proteins involved in zona pellucida recognition originate from the epithelial lining of the epididymis (Kuo, Li, Maeda, Gadella, & Tsai, ; van Gestel et al, ). Sperm in the cauda epididymis are able to fertilize an egg in vitro (Matás et al, ), which indicates their state of maturation.…”

Flagellar hyperactivation of bull and boar spermatozoa

“…One of the changes which are observed during early stage of capacitation is release of decapacitation factors from sperm surface. So far, surface coating proteins (eg acrosomal stabilizing factor and seminal vesicle secretions) and lipids (eg cholesterol), which stabilize sperm membranes, have been identified as decapacitation factors. As explained previously, seminal vesicle secretion 2 (SVS2) is one of major proteins secreted from mouse seminal vesicle and exposed to spermatozoa at ejaculation.…”