Abstract
Spermatozoa need to conduct a series of biochemical changes termed capacitation in order to fertilize. In vivo, capacitation is sequentially achieved during sperm transport and interaction with the female genital tract, by mechanisms yet undisclosed in detail. However, when boar spermatozoa are stored in the tubal reservoir pre-ovulation, most appear to be in a non-capacitated state. This study aimed at deciphering the transcriptomics of capacitation-related genes in the pig pre-ovulatory oviduct, following the entry of semen or of sperm-free seminal plasma (SP). Ex-vivo samples of the utero-tubal junction (UTJ) and isthmus were examined with a microarray chip (GeneChip® Porcine Gene 1.0 ST Array, Thermo Fisher Scientific) followed by bioinformatics for enriched analysis of functional categories (GO terms) and restrictive statistics. The results confirmed that entry of semen or of relative amounts of sperm-free SP modifies gene expression of these segments, pre-ovulation. It further shows that enriched genes are differentially associated with pathways relating to sperm motility, acrosome reaction, single fertilization, and the regulation of signal transduction GO terms. In particular, the pre-ovulation oviduct stimulates the Catsper channels for sperm Ca2+ influx, with AKAPs, CATSPERs, and CABYR genes being positive regulators while PKIs and CRISP1 genes appear to be inhibitors of the process. We postulate that the stimulation of PKIs and CRISP1 genes in the pre-ovulation sperm reservoir/adjacent isthmus, mediated by SP, act to prevent premature massive capacitation prior to ovulation.
Highlights
The complex nature of maternal-gamete communication has gained increased interest over the past decades
Setting the fold change to 1/−1 and p-value to
Sci. 2020, 21, 1840 genes were differentially expressed in the isthmus (Isth) after mating (M), and 1662 (UTJ) and 886 (Isth) were DEG after artificial insemination (P1-artificial cervical deposition (AI)), compared to controls sows
Summary
The complex nature of maternal-gamete communication has gained increased interest over the past decades. It is known that the signals provided by the gametes and interactions with the female genital tract are capable of rapidly influencing the local environment, stimulating a broad range of events towards successful fertilization and subsequent pregnancy [1,2]. These signals are critical in influencing a wide number of gamete functions such as final gamete maturation, gamete transport and survival, and are initiated by the gametes themselves immediately after ovulation or through mating/artificial insemination [3]. A recent study has demonstrated the activation of a local immune response in the endometrium and the oviduct as rapidly as 24 h after semen or even seminal plasma (SP) has been deposited in the porcine female genital tract [10]
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