Mouse embryo cryopreservation utilizing a novel high-capacity vitrification spatula

Minimum volume Spatula MVD vitrification method improves embryo survival compared to traditional slow freezing, both for in vivo and in vitro produced mice embryos

This study was conducted to compare the effect of minimum volume Spatula MVD vitrification (VIT) versus traditional slow freezing (SLF) of mouse embryos. A total of 2,617 8-cell in vivo derived and 2-cell in vitro produced B6D2 mouse embryos were subjected to freezing/thawing or vitrification/warming, while fresh embryos were used as control group. Embryo recovery, survival and development rate, pregnancy rate and offspring production were analyzed. In Experiment 1, 8-cell in vivo derived embryos were subjected to in vitro culture, resulting in greater survival and development rates at 3.5 days post coitum stage in VIT than in SLF group (P < 0.05). Although both methods reached an acceptable hatching rate (41.0% and 49.7% for VIT and SLF, respectively; P=NS), it was significantly lower respect to the control group (67.8%, P < 0.01). In Experiment 2, 2-cell in vitro produced mouse embryos showed a similar recovery rate from the device after freezing/thawing or vitrification/warming (∼84%), however survival rate was significantly higher for vitrified/warmed (94.7%) than frozen/thawed embryos (85.1%; P < 0.01). Vitrified/warmed and control fresh embryos were transferred to surrogate mothers, revealing no differences both in pregnancy and offspring production rates. Our data demonstrate that minimum volume Spatula MVD method is a simple home-made useful technique for vitrification of 2-cell and 8-cell mouse embryos produced either in vitro or in vivo.

Mouse Embryo Cryopreservation by Rapid Cooling

Embryo cryopreservation has been used to archive mouse strains. Protocols have evolved over this time and now vary considerably in terms of cryoprotectant solution, cooling and warming rates, methods to add and remove cryoprotectant, container or carrier type, volume of cryoprotectant, the stage of preimplantation development, and the use of additional treatments such as blastocyst puncture and microinjection. The rapid cooling methods use concentrated solutions of cryoprotectants to reduce the water content of the cell before cooling commences, thus preventing the formation of ice crystals. Embryos are equilibrated with the cryoprotectants, loaded into a carrier, and then rapidly cooled (e.g., by being plunged directly into LN₂ or onto a surface cooled in LN₂). The rapid cooling methods eliminate the need for controlled-rate freezers and seeding procedures. However, they are much more sensitive to minor variations when performing the steps. The rapid-cooling protocol described here is suitable for use with plastic insemination straws. Because it uses relatively large volumes, it is less technically demanding than some other methods that use minivolume devices.

Cryopreservation of oocytes and embryos

Two hundred years have passed since the first description of supercooled water by Gey-Lussac to the recently high survival rates of embryo and oocytes after vitrification. This review discusses important milestones that have made vitrification the method of choice for oocytes and embryos cryopreservation. We will go through the first cells ever to survive low temperature exposure in the beginning of the last century, the finding of glycerol in the late 1940s and the first mouse and bovine embryos freezing in the 1970s. During the 1980s, embryo vitrification began and the time since is a tribute to the development of oocytes vitrification. Standardization and an automatic vitrification procedure are currently under development. The next evolutionary step in oocyte and embryo cryopreservation will be preserving them in the dry state at room temperature, allowing home storage for future use a reality.

Melatonin modulates the expression of BCL-xl and improve the development of vitrified embryos obtained by IVF in mice

PURPOSE

Antioxidant and anti-apoptotic effects of melatonin on development of in vitro fertilization (IVF)/vitrified two-cell mouse embryos were evaluated in this study.

METHODS

The IVF two-cell embryos were vitrified by cryotop, and were cultured in KSOM medium in different concentrations of melatonin (10(-6), 10(-9), 10(-12) M) and without melatonin. The blastocyst cell number, apoptotic cells and glutathione (GSH) level were evaluated by differential, TUNEL and cell tracker blue staining, respectively. The expression of Bax and Bcl-xl genes was evaluated by qPCR. The expression of melatonin receptors (Mtnr1a and Mtnr1b) in mouse 2-cell embryos and blastocysts was evaluated by RT-PCR.

RESULTS

Melatonin increased the rate of cleavage and blastulation at 10(-12) M concentration (p < 0.05). The number of trophectoderm and inner cell mass showed a significant increase (p < 0.05) in 10(-9) M melatonin. The 10(-9) M and 10(-12) M melatonin treatments significantly reduced (p < 0.05) the apoptotic index. The significant increase in the expression of Bcl-xl observed at 10(-9) M concentration however, reduced expression of Bax was not statistically significant. The levels of GSH in 10(-9) and 10(-12) M groups were significantly improved relative to the control group (p < 0.05). The Mtnr1a was expressed in 2-cell embryos and blastocysts in all groups, but the expression of Mntr1b was not detected.

CONCLUSION

Melatonin may have a special role against oxidative stress in protection of IVF/vitrified embryos.

Current progress in oocyte and embryo cryopreservation by slow freezing and vitrification

Preservation of female genetics is currently done primarily by means of oocyte and embryo cryopreservation. The field has seen much progress during its four-decade history, progress driven predominantly by research in humans, cows, and mice. Two basic cryopreservation techniques rule the field – controlled-rate freezing, the first to be developed, and vitrification, which, in recent years, has gained a foothold. While much progress has been achieved in human medicine, the cattle industry, and in laboratory animals, this is far from being the case for most other mammals and even less so for other vertebrates. The major strides and obstacles in human and other vertebrate oocyte and embryo cryopreservation will be reviewed here.

Cryopreservation of mammalian embryos: Advancement of putting life on hold

Rodent transgenesis and human-assisted reproductive programs involve multistep handling of preimplantation embryos. The efficacy of production and quality of results from conventionally scheduled programs are limited by temporal constraints other than the quality and quantities of embryos per se. The emergence of vitrification, a water ice-free cryopreservation technique, as a reliable way to arrest further growth of preimplantation embryos, provides an option to eliminate the time constraint. In this article, current and potential applications of cryopreservation to facilitate laboratory animal experiments, colony management, and human-assisted reproductive programs are reviewed. Carrier devices developed for vitrification in the last two decades are compared with an emphasis on their physical properties that infer cooling rate of samples and sterility assurance. Biological impacts of improved cryopreservation on preimplantation embryos are also discussed.