Structural, biochemical and functional aspects of sperm-oocyte interactions in pigs

Abstract

Polyspermic fertilization is still a major issue in porcine IVF systems. New information is available to characterize the zona pellucida (ZP) at different developmental stages by scanning electron microscopy (SEM) and by confocal microscopy to show the distribution of ZP glycoproteins. SEM images indicated no differences between in vivo and in vitro matured oocytes; however a change in the surface structure between immature and matured oocytes, as well as between mature oocytes and preimplantation embryos was obvious. In addition, spermatozoa were more tightly fixed in the ZP of in vivo produced compared to the ZP of in vitro produced embryos. The ZP undergoes biochemical changes during maturation prior to fertilization. The acidity of the ZP increases during maturation as indicated by a shift of 1.3 pl units for ZPB/ZPC and 0.8 pl units for ZPA in 2D gel electrophoresis, which is based on increasing sulfation of the oligosaccharides during maturation. Mass spectrometry in combination with in-gel deglycosylation allowed the mapping of new glycosylation sites. Functionality of the ZP also depends on its maturation status. Induction of the acrosome reaction was delayed when capacitated spermatozoa were exposed to immature oocytes. .structoral, biocheigiefl and tunctuinai aspects Of sperni4 vte Nitpick if(in pigs i

Sperm binding properties to uterine epithelial cells in vitro employing a primary porcine endometrium culture system

“…The ZP encompasses several putative binding mechanisms by providing several ligands for sperm surface molecule to engage to. The most prominent are the so-called Zona pellucida glycoproteins A, B and C (ZPA-C), containing a large number of highly specific glycans made up of neutral or highly sulphated or sialyted O-and N-links (RATH et al, 2005). ZPA is the largest ZP protein in the pig, containing six potential N-glycosylation sites, meaning that at six potential sites an addition of a carbohydrate to a nitrogen atom within the molecule is possible, whereas the number of O-glycosylation sites remains still unknown.…”

“…It was shown to be present on sperm bound to the ZP and has a high affinity for glycoproteins. After the acrosome reaction it vanishes from the sperm surface and is thus thought to participate in gamete recognition and initial binding but not secondary binding (RATH et al, 2005).…”

“…This activation appears to be regulated on and by the zona pellucida and occurs alongside during acrosome reaction. β-acrosin stimulates the digestion of the ZP during sperm migration through this membrane (RATH et al, 2005).…”