In vitro fertilization and polyspermy in the pig: Factors affecting fertilization rates and cytoskeletal reorganization of the oocyte

Abstract

Polyspermy is a common phenomenon in the pig. Extensive information has become available from in vitro studies on not only the quality of oocytes but also the quality of spermatozoa. However, little information is available on the relative penetration rates of fresh and frozen spermatozoa from the same ejaculate from boars of different breeds. The present results, based on a total of 15 boars of three different breeds, revealed that the inter-breed variation in fertilization and polyspermic rates is larger than intra-breed variation. It was also shown that the incidence of polyspermy as well as penetration rate was greatly decreased by freezing and thawing, even if a higher number of sperm was coincubated with cumulus-free oocytes for a longer period compared to fresh sperm of the same ejaculate. This study focuses on the cytoskeletal organization of the oocyte with respect to the status of cumulus investment, and monospermic and polyspermic fertilization. The status of cumulus cells correlated with the density of transzonal cumulus-cell processes and with the maturation rate of oocytes and, to some degrees, the incidence of polyspermy. Polyspermic zygotes formed multiple microtubule domains in association with individual male pronuclei (PN), but in a high degree of polyspermy (more than trispermy), the pronuclear apposition did not proceed. The effect of multiple PN of paternal and maternal origin on the cytoskeletal reorganization is also discussed.

Effect of blood plasma collected after adrenocorticotropic hormone administration during the preovulatory period in the sow on oocyte in vitro maturation

“…The characteristics of actin microfilaments observed both in immature (at germinal vesicle stage) and mature (MII) oocytes were similar to those previously described in porcine oocytes [34,35]. Minor differences were observed by CLSM in actin microfilament patterns in mature oocytes after treatment.…”

“…1A-F). These criteria were adapted from previous studies [33][34][35]. Blastocysts were classified into grades I to III according to the integrity of their actin cytoskeleton, as previously described [28,36,37].…”

Pre-incubation of porcine semen reduces the incidence of polyspermy on embryos derived from low quality oocytes

“…Although high polyspermic penetration rates are well documented in pigs (FUNAHASHI 2003;SUZUKI et al, 2003), some interesting interactions of oocyte quality and the sire have been reported in cattle (OHLWEILER et al, 2013), where depending on the technique used to artificially fertilize the oocyte, the embryo development rate was affected or not by the oocyte quality. Unfortunately, oocytes of low quality are predominant in gilt ovaries.…”

“…Great variations have been observed in polyspermy rates of both fresh (SIRARD et al, 1993) and frozen semen (NAGAI et al, 1988). Polyspermy rates are directly related to the sperm number at the site of fertilization (FAUSTINI et al, 2010), and also with the oocyte quality (SUZUKI et al, 2003). It is believed that the oviduct microenvironment participates in polyspermic blocking during in vivo fertilization (LUÑO et al, 2013).…”

“…This failure of the IVC systems results in a poor release of cortical granules after sperm penetration, thus resulting in failure of the zona pellucida reaction, and consequently in polyspermy . These ratios are even greater in low quality oocytes (SUZUKI et al, 2003). In porcine IVF procedures performed with slaughterhouse ovaries it is possible to obtain a great number of oocytes.…”