Sperm selection and competition in pigs may be mediated by the differential motility activation and suppression of sperm subpopulations within the oviduct

Abstract

SUMMARY When spermatozoa from two or more boars are mixed and females inseminated,the resulting litters are often skewed in favour of one male but there is currently no satisfactory physiological explanation for this effect. However,to reach the oocytes, the spermatozoa must enter the oviduct where they are exposed to factors that modulate their activity. They either become sequestered within the oviductal sperm reservoir or bypass the reservoir and proceed towards the oocytes. The oviduct may therefore hold the key to mammalian sperm selection, thereby explaining why laboratory tests of sperm function, performed on whole ejaculates, are unable to account for the boar-specific skewing effects. We have previously shown that boar sperm motility is highly stimulated by bicarbonate, a naturally abundant component of oviductal fluid. Using motility-based sperm subpopulation analysis, we show here that the relative sizes of bicarbonate-responsive and unresponsive sperm subpopulations vary between individual boars. Proteins derived from oviduct epithelial plasma membranes suppress the activation response and modify sperm movement trajectories in a subpopulation-specific and dose-dependent manner. The suppression response varies between boars and some spermatozoa remain unsuppressed in the presence of oviductal proteins. When boars are ranked according to their susceptibility to bicarbonate-induced stimulation, rankings differ depending upon the presence or absence of oviductal proteins. The suppression response is not caused by inhibition of bicarbonate uptake; on the contrary this is enhanced by oviductal proteins. We suggest that the boar-specific and sperm subpopulation-specific interactions between sperm motility activation and suppression responses are likely to result in sperm selection before the spermatozoa meet the oocytes.

Porcine sperm capacitation involves tyrosine phosphorylation and activation of aldose reductase

“…But the sperm must be activated at least twice more to exert those capacities. The constituents surrounding sperm are very important for attaining these activation processes (Boatman 1997, Satake et al 2006. The first activation occurs at ejaculation.…”

The effect of oviductal deleted in malignant brain tumor 1 over porcine sperm is mediated by a signal transduction pathway that involves pro-AKAP4 phosphorylation

“…It was first isolated from the oviduct based on its ability to bind to boar sperm periacrosomal membranes (Marini & Cabada 2003) and produces not only alteration of pig sperm acrosome integrity but also another biological effect, suppression of motility, as well as tyrosine phosphorylation of a 97 kDa sperm protein (p97; Teijeiro et al 2008Teijeiro et al , 2011. The reduction of sperm motility in the oviduct (Overstreet & Cooper 1975, Satake et al 2006 and the existence of damaged sperm at its lumen have been known for long; however, only recently, the study of the mechanisms involved in the oviductal epitheliumsperm signaling dialogue, related to these phenomena, has began to be unraveled.…”

Dinámicas espermáticas subpoblacionales durante el proceso de criopreservación en eyaculados de caprino (Capra aegagrus hircus)

“…Además, la identificación de subpoblaciones espermáticas puede reemplazar estudios realizados mediante análisis estadísticos tradicionales, donde se considera al eyaculado como una población homogénea de células, sin tener la cuenta las diferentes características cinéticas a nivel individual, lo cual convierte al análisis convencional en un análisis poco adecuado (Martí et al, 2012). Así los resultados derivados del sistema CASA, del PCA y del análisis multivariante de conglomerados revelaron características funcionales diferenciales muy interesantes, demostrando que el eyaculado se compone de diferentes grupos celulares (subpoblaciones con características cinéticas diferenciadas) que se comportan de formas específicas dependiendo del proceso al que sea sometido la muestra espermática (Satake et al, 2006). Es necesario remarcar, que no sólo el número de subpoblaciones espermáticas varió notablemente entre las etapas estudiadas, sino que, además, debido probablemente a los diferentes medios utilizados y al sometimiento de las muestras espermáticas a diferentes temperaturas durante el proceso de criopreservación, la distribución de esas muestras espermáticas cambió radicalmente entre las diferentes etapas.…”

“…Desde hace tiempo, la comunidad científica ha llevado a cabo estudios basados en la diferenciación de subpoblaciones espermáticas en el eyaculado las cuales muestran características cinéticas diferentes (Satake et al, 2006;Garcia-Herreros et al, 2012). De hecho, la ESHRE (ESHRE; European Society of Human Reproduction and Embryology, 1998) admite que el uso de análisis estadísticos convencionales basados en valores de medias no son apropiados y tienen un valor limitado debido a que consideran al eyaculado como una población espermática homogénea y ajustada a una distribución normal.…”