Successful pregnancy requires an appropriate communication between the mother and the embryo. Recently, exosomes and microvesicles, both membrane-bound extracellular vesicles (EVs) present in the oviduct fluid have been proposed as key modulators of this unique cross-talk. However, little is known about their content and their role during oviduct-embryo dialog. Given the known differences in secretions by and oviduct epithelial cells (OEC), we aimed at deciphering the oviduct EVs protein content from both sources. Moreover, we analyzed their functional effect on embryo development. Our study demonstrated for the first time the substantial differences between and oviduct EVs secretion/content. Mass spectrometry analysis identified 319 proteins in EVs, from which 186 were differentially expressed when and EVs were compared ( < 0.01). Interestingly, 97 were exclusively expressed in EVs, 47 were present only in and 175 were common. Functional analysis revealed key proteins involved in sperm-oocyte binding, fertilization and embryo development, some of them lacking in EVs. Moreover, we showed that-produced embryos were able to internalize EVs during culture with a functional effect in the embryo development. EVs increased blastocyst rate, extended embryo survival over time and improved embryo quality. Our study provides the first characterization of oviduct EVs, increasing our understanding of the role of oviduct EVs as modulators of gamete/embryo-oviduct interactions. Moreover, our results point them as promising tools to improve embryo development and survival under conditions.

Early development in canine species follows a very specific pattern. Oocytes are ovulated at the germinal vesicle stage and meiotic resumption occurs in the oviduct. However, because of difficulties in the accurate determination of ovulation time and in the observation of oocyte nuclear stage by light microscopy, these early events have not been fully described. Moreover, the oocyte stage at which sperm penetration occurs is still uncertain since fertilization of immature oocytes has been reported in vivo and in vitro. The aim of this study was to establish the exact timing of in vivo meiotic resumption, fertilization and early embryo development in the bitch with reference to ovulation. Ovulation was first determined by ultrasonography, artificial inseminations were performed daily and oocytes/embryos were collected between 17 and 138 h after ovulation. After fixation and DNA/tubulin staining, the nuclear stage was observed by confocal microscopy. Of the 195 oocytes/embryos collected from 50 bitches, the germinal vesicle stage was the only one present until 44 h post-ovulation, and the first metaphase II stage was observed for the first time at 54 h. Sperm penetration of immature oocytes appeared to be exceptional (three out of 112 immature oocytes). In most cases, fertilization occurred from 90 h post-ovulation in metaphase II oocytes. Embryonic development was observed up to the eight-cell stage. No significant influence of bitch breed and age on ovulation rate, maturation and developmental kinetics was observed. However, some heterogeneity in the maturation/development process was observed within the cohort of oocytes/embryos collected from one bitch. In conclusion, the most peculiar aspect of the canine species remains oocyte meiotic maturation whereas fertilization follows the same pattern as in other mammals. Reproduction (2005) 130 193-201

Syncytins are envelope protein genes of retroviral origin that have been captured for a function in placentation. Two such genes have already been identified in simians, two distinct, unrelated genes have been identified in Muridae, and a fifth gene has been identified in the rabbit. Here, we searched for similar genes in the Laurasiatheria clade, which diverged from Euarchontoglires—primates, rodents, and lagomorphs—shortly after mammalian radiation (100 Mya). In silico search for envelope protein genes with full-coding capacity within the dog and cat genomes identified several candidate genes, with one common to both species that displayed placenta-specific expression, which was revealed by RT-PCR analysis of a large panel of tissues. This gene belongs to a degenerate endogenous retroviral element, with precise proviral integration at a site common to dog and cat. Cloning of the gene for an ex vivo pseudotype assay showed fusogenicity on both dog and cat cells. In situ hybridization on placenta sections from both species showed specific expression at the level of the invasive fetal villi within the placental junctional zone, where trophoblast cells fuse into a syncytiotrophoblast layer to form the maternofetal interface. Finally, we show that the gene is conserved among a series of 26 Carnivora representatives, with evidence for purifying selection and conservation of fusogenic activity. The gene is not found in the Pholidota order and, therefore, it was captured before Carnivora radiation, between 60 and 85 Mya. This gene is the oldest syncytin gene identified to date, and it is the first in a new major clade of eutherian mammals.