Cryosurvival of rabbit embryos obtained after superovulation with corifollitropin alfa with or without LH

Multigenerational Effects of a Complex Human-Relevant Exposure during Folliculogenesis and Preimplantation Embryo Development: The FEDEXPO Study

Animal toxicological studies often fail to mimic the complexity of the human exposome, associating low doses, combined molecules and long-term exposure. Since the reproductive potential of a woman begins in the fetal ovary, the literature regarding the disruption of its reproductive health by environmental toxicants remains limited. Studies draw attention to follicle development, a major determinant for the quality of the oocyte, and the preimplantation embryo, as both of them are targets for epigenetic reprogramming. The "Folliculogenesis and Embryo Development EXPOsure to a mixture of toxicants: evaluation in the rabbit model" (FEDEXPO) project emerged from consideration of these limitations and aims to evaluate in the rabbit model the impacts of an exposure to a mixture of known and suspected endocrine disrupting chemicals (EDCs) during two specific windows, including folliculogenesis and preimplantation embryo development. The mixture combines eight environmental toxicants, namely perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH), 2,2'4,4'-tetrabromodiphenyl ether (BDE-47), di(2-ethylhexyl) phthalate (DEHP) and bisphenol S (BPS), at relevant exposure levels for reproductive-aged women based on biomonitoring data. The project will be organized in order to assess the consequences of this exposure on the ovarian function of the directly exposed F0 females and monitor the development and health of the F1 offspring from the preimplantation stage. Emphasis will be made on the reproductive health of the offspring. Lastly, this multigenerational study will also tackle potential mechanisms for the inheritance of health disruption via the oocyte or the preimplantation embryo.

Oocyte quality and in vivo embryo survival after ovarian stimulation in nulliparous and multiparous rabbit does

Superovulation treatments aim to stimulate multifollicular recruitment, maximizing the number of oocytes or transferable embryos produced. Factors associated with the superovulation protocol, female characteristics and many other factors are determinants in the number and quality of oocytes obtained. An accurate way to assess oocyte quality more precise than morphological appearance is genetic expression. The present study aims to compare the response of nulliparous and multiparous females to superovulatory stimulation, studying its effect on the expression of some genes associated with the activation, growth, development and oocyte-embryo transition of oocytes, as well as its impact on in vivo embryonic development and viability rate at birth. In a first experiment, the effect of stimulation treatment on the ovulation response and the expression of the MSY2, MATER, ITPR1, ITPR2, ITPR3, eIF4E, PAR1, PAPOL-A, PAPOL-G, ZAR1 and YY1 genes in nulliparous and multiparous females were determined. In a second experiment, the implantation and viability at birth of embryos from superovulated nulliparous and multiparous females were analysed. The ovulation rate was significantly higher in the superovulation groups than in the control groups. The ovulation rate was significantly increased in nulliparous females compared with multiparous does. From the eleven genes analysed, only the expression of MATER, PAPOL-A, PAPOL-G and ZAR-1 genes was shown to be different among experimental groups. Finally, in terms of implantation rate and viability at birth, the nulliparous control group showed better results than the rest of the groups. Both hyperstimulation treatment and reproductive female's history seem to alter the transcriptome of important genes related to oocyte maturation and competence acquisition, affecting in vivo embryo viability.

The harmful effect of removing the extracellular vitrification medium during embryo cryopreservation using a nylon mesh device in rabbit

During the last decades, many techniques have been developed to reduce sample volume and improve cooling and warming rates during embryo vitrification. The vast majority are based on the "minimum drop size" concept, in which the vitrification solution around embryos is reduced by aspiration, leaving a tiny part of volume surrounding embryos. However, novel cryodevices were aimed to remove the entire vitrification solution. This study was designed to compare the "minimum drop size" technique using Cryotop® with the nylon mesh as cryodevice on rabbit morula embryos. The outcomes assessed were the in vitro development rates (experiment 1) and the offspring rates at birth (experiment 2). Embryos were vitrified in a two-step procedure; equilibrium (10% EG + 10% Me2SO) for 2 min and vitrification (20% EG + 20% Me2SO) for 1 min. In experiment 1, embryos (n = 323) were warmed and subsequently in vitro cultured for 48 h to assess the embryo developmental capability to reach the hatching-hatched blastocyst stage. In experiment 2, embryos were transferred using the laparoscopic technique (n = 369) to assess the offspring rate at birth. In this context, rates of in vitro embryo development were similar between vitrified groups (0.73 ± 0.042% and 0.66 ± 0.047% for Cryotop® and nylon mesh device, respectively), but lower than in the fresh group (0.97 ± 0.016%, p < 0.05). In experiment 2, there were no significant differences in survival rates (offspring born/total embryos transferred) among the Cryotop® device group and fresh group (0.41 ± 0.049% and 0.49 ± 0.050%, respectively). But significantly lower value was obtained in the nylon mesh device group (0.18 ± 0.030%). These results indicate that nylon mesh is not suitable as cryodevice for rabbit morula vitrification, remaining those using the "minimum drop size" methodology as the best option.