Platelet-activating factor acetylhydrolase 1B3 (PAFAH1B3) is required for the formation of the meiotic spindle during in vitro oocyte maturation.

Platelet-activating factor (PAF) is a well-described autocrine growth factor involved in several reproductive processes and is tightly regulated by its hydrolysing enzyme, PAF acetylhydrolase 1B (PAFAH1B). This intracellular enzyme consists of three subunits: one regulatory, 1B1, and two catalytic, 1B2 and 1B3. PAFAH1B3 has remained uncharacterised until now. Here, we report that PAFAH1B3 is present during the different stages of the first meiotic division in bovine, murine and human oocytes. In these species, the PAFAH1B3 subunit was clearly present in the germinal vesicle, while at metaphase I and II, it localised primarily at the meiotic spindle structure. In cattle, manipulation of the microtubules of the spindle by nocodazole, taxol or cryopreservation revealed a close association with PAFAH1B3. On the other hand, disruption of the enzyme activity either by P11, a selective inhibitor of PAFAH1B3, or by PAFAH1B3 antibody microinjection, caused arrest at the MI stage with defective spindle morphology and consequent failure of first polar body extrusion. In conclusion, our results show that one of the catalytic subunits of PAFAH1B, namely PAFAH1B3, is present in bovine, murine and human oocytes and that it plays a functional role in spindle formation and meiotic progression during bovine oocyte maturation.

An improved vitrification protocol for equine immature oocytes, resulting in a first live foal.

BACKGROUND: The success rate for vitrification of immature equine oocytes is low. Although vitrified-warmed oocytes are able to mature, further embryonic development appears to be compromised. OBJECTIVES: The aim of this study was to compare two vitrification protocols, and to examine the effect of the number of layers of cumulus cells surrounding the oocyte during vitrification of immature equine oocytes. STUDY DESIGN: Experimental in vitro and in vivo trials. METHODS: Immature equine oocytes were vitrified after a short exposure to high concentrations of cryoprotective agents (CPAs), or a long exposure to lower concentrations of CPAs. In Experiment 1, the maturation of oocytes surrounded by multiple layers of cumulus cells (CC oocytes) and oocytes surrounded by only corona radiata (CR oocytes) was investigated. In Experiment 2, spindle configuration was determined for CR oocytes vitrified using the two vitrification protocols. In Experiment 3, further embryonic development was studied after fertilisation and culture. Embryo transfer was performed in a standard manner. RESULTS: Similar nuclear maturation rates were observed for CR oocytes vitrified using the long exposure and nonvitrified controls. Furthermore, a lower maturation rate was obtained for CC oocytes vitrified with the short exposure compared to control CR oocytes (P = 0.001). Both vitrification protocols resulted in significantly higher rates of aberrant spindle configuration than the control groups (P<0.05). Blastocyst development only occurred in CR oocytes vitrified using the short vitrification protocol, and even though blastocyst rates were significantly lower than in the control group (P<0.001), transfer of five embryos resulted in one healthy foal. MAIN LIMITATIONS: The relatively low number of equine oocytes and embryo transfer procedures performed. CONCLUSIONS: For vitrification of immature equine oocytes, the use of 1) CR oocytes, 2) a high concentration of CPAs, and 3) a short exposure time may be key factors for maintaining developmental competence.

Role of cumulus cells during vitrification and fertilization of mature bovine oocytes: Effects on survival, fertilization, and blastocyst development.

This study was designed to determine the role of cumulus cells during vitrification of bovine oocytes. Mature cumulus-oocyte complexes (COCs) with many layers of cumulus cells, corona radiata oocytes (CRs), with a few layers of cumulus cells, and denuded oocytes (DOs) without cumulus cells were vitrified in 15% ethylene glycol, 15% dimethyl sulfoxide, and 0.5-M sucrose. Oocytes that survived the vitrification process were fertilized. Denuded oocytes were fertilized with or without supplementation of intact COCs (DOsCOCs). First, survival and embryo development rates were studied. Higher survival rates were obtained for DOs and DOsCOCs (94% and 95%, respectively) compared with COCs (82.7%, P < 0.05). Corona radiata oocytes showed similar survival rates when compared with DOs. The cleavage and blastocyst rates of vitrified DOs were compromised because cumulus cells were not present during the fertilization (34% and 2.7%, respectively). However, the situation could be reverted when DOs were supplemented with intact COCs (DOsCOCs; 62.7% and 12.7%, respectively, P < 0.05). Vitrified CRs showed similar cleavage and blastocyst rate (49.3% and 7.7%, respectively) compared with COCs (54.8% and 4.9%, respectively). In the second experiment, the penetration rate was analyzed. Removing cumulus cells before fertilization reduced the fertilization of vitrified DOs compared with COCs (24.3% vs. 52.8%, P < 0.05). The supplementation of DOs with intact COCs (DOsCOCs) improved the fertilization rate though (49.6%, P < 0.05). No differences in the fertilization rate were found between CRs and COCs. In the third experiment, parthenogenetic activation was examined. Interestingly, the CRs group showed higher cleavage and blastocyst rates (76.8% and 29.6%, respectively) than the COCs (39.1% and 7.5%, respectively, P < 0.05). Furthermore, oocytes from vitrified CRs had the same odds to become a blastocyst as fresh oocytes (1.1 vs. 1.5, respectively). In conclusion, our data reported that cumulus cells reduce survival after the vitrification of mature bovine oocytes. Because cumulus cells are required for fertilization, the use of partially DOs (CRs) or the addition of intact COCs (DOsCOCs) during fertilization can result in higher survival and embryo development after vitrification.