Morphological changes in mouse embryos cryopreserved by different techniques

The role of apoptosis in cryopreserved animal oocytes and embryos

Cryopreservation of both gametes and embryos, both for storage and for the preservation of their developmental capacity is a critical aspect of assisted reproductive technology. The survival of reproductive material following cryopreservation protocols is not only vital to clinical applications in the human in vitro fertilisation clinic, but is also important in the in vitro production of livestock embryos. The ability to routinely cryopreserve oocytes and embryos of livestock species has the potential to improve animal welfare, reduce environmental impact, and reduce the associated costs for breeding companies through the reduction of live animal transportation. Unfortunately, frozen oocytes and embryos are regularly documented to contain a higher proportion of apoptotic cells compared to their non-frozen counterparts, with freezing procedures thought to trigger apoptotic pathways of cell death. Comparisons between frozen and non-frozen samples also show changes in the gene expression of apoptotic factors such as Bcl-2 and Bax in response to cryopreservation. Apoptotic inhibition has the potential to improve cryosurvival, and how to achieve this is subject to debate. Here, we review how exposure to low temperatures during cryopreservation may be responsible for the abnormal activation of apoptotic pathways in mammalian oocytes and embryos, and discuss the ways in which they can be influenced to improve cryopreservation protocols, particularly in agriculturally important species.

The profiling of pre- and post-warming DNA in mouse embryos with microsatellite method

Aims:

This research aimed to identify the deoxyribonucleic acid (DNA) profile and changes of post-warming embryo after being frozen with vitrification method using microsatellite method.

Materials and Methods:

This research examined the mouse embryo blastocysts that were divided into four groups: Post-warming living blastocyst, post-warming living blastocyst with half fragmented cell, post-warming dead blastocyst, and pre-freezing living blastocyst. The isolation sample applied phenol-chloroform method. After obtaining polymerase chain reaction results, all the samples of pre-freezing fresh embryo, post-warming living embryo, dead embryo, and degenerated embryo were then examined by single-strand conformation polymorphism (SSCP).

Results:

The amplification with D18mit14 primer was 100 bp and 150bp with D18mit87 primer, 150bp with D7mit22, and 300bp with D7mit25. The result of SSCP with D18mit14 primer showed that the blastocysts were fragmented and dead after warming process and formed into two DNA strand fragments, while the fresh embryos which passed freezing process did not form any fragment. D18mit87 primer SSCP indicated different fragments for each treatment. The result of SSCP using D7mit22 formed two different fragments for each treatment. While using D7mit25, the SSCP result formed some different fragments for each sample. Post-warming living embryo had similar ribbon to pre-freezing fresh embryo.

Conclusion:

D7mit222, D7mit25, and D18mit87 primers could be used as the aneuploidy marker on mouse embryos that were induced by post-warming process. The profile of living blastocyst, dead blastocyst, and post-warming fragmented blastocyst had different DNA tapes.

Apoptosis and developmental capacity of vitrified parthenogenetic pig blastocysts

This study was conducted to evaluate whether the poor developmental capacity of pig embryos after vitrification was related to the occurrence of apoptosis. Parthenogenetic blastocysts were used as the research material. The blastocoel recovery rate, mitochondrial membrane potential (ΔΨm), amount of early apoptosis, activities of several caspases, and relative abundance of mRNA of apoptosis-related genes involved in mitochondria and death receptor apoptotic pathways were detected before or after vitrification. The results indicate that the blastocoel recovery rate (31.0%) and total cells (31.8) of vitrified blastocysts were less than those of fresh blastocysts (100% and 38.2, P <  0.05). The ΔΨm of vitrified blastocysts was 0.46, which was less than that of fresh blastocysts (1.02, P <  0.05). The rate of apoptotic cells in vitrified blastocysts (8.1%) after TUNEL (TdT-mediated dUTP Nick-End Labeling) assay was markedly greater than that in fresh blastocysts (3.9%, P <  0.05). The pan-caspase, caspase-3, caspase-8 and caspase-9 activities of vitrified blastocysts (20.7, 20.6, 17.6 and 19.9) were markedly greater than those of fresh blastocysts (7.4, 6.5, 5.5 and 6.3, P <  0.05). The real-time PCR results indicated that relative abundance of caspase-8 and TNF-α mRNA from death receptor apoptotic pathway and caspase-9 for the mitochondrial apoptotic pathway genes in the vitrified group were greater than those in the fresh group P <  0.05). The relative abundance of Bcl-2 and SOD-1 mRNA for the mitochondrial pathway genes in the vitrified group was less than those in the fresh group (P <  0.05). In conclusion, the poor developmental capacity of vitrified parthenogenetic pig blastocysts was closely related with apoptosis. Both mitochondria and death receptor-mediated apoptotic pathways participated the occurrence of this apoptosis.

Presence of cleaved caspase 3 in swine embryos of different developmental capacities produced by parthenogenetic activation

This study assessed the presence of cleaved caspase 3 (CC3) during the in vitro development of swine embryos produced by parthenogenetic activation (PA). Embryos with high and low capacity to develop into blastocysts and the exposure to a caspase inhibitor (z-DEVD-fmk) were used to investigate the effect of CC3 on embryo development. The blastocyst rate (64.3% vs. 16.4%) and the average number of nuclei per blastocyst (39.7 vs. 19.8) were significantly higher (P < 0.05) in early- (before 24 hr) compared to late- (between 24 and 48 hr) cleaving embryos after PA. CC3 was mainly detected in the cytoplasm of Day-2 and -4 embryos, but was primarily localized in the nucleus of Day-5 and -6 embryos. The fluorescence signal for CC3 relative to negative controls was significantly higher (P < 0.05) in early- (2.42-fold) compared to late-cleaving (1.39-fold) embryos at Day 2 of culture. Treatment with z-DEVD-fmk during the first 24 or 48 hr of the culture period resulted in more embryos developing into blastocysts compared to the control group (55.8% and 55.1% vs. 37%, respectively; P < 0.05). This study confirmed the presence of CC3 in PA embryos from the two-cell to the blastocyst stage, and revealed that CC3 cellular-localization changed during embryo development. CC3 was shown to be more abundant in early-cleaving and more developmentally competent embryos compared to late-cleaving and less developmentally competent embryos. The inhibition of caspase activity at the beginning, but not at the end, of the culture period affected development of PA embryos.

Detection of apoptosis in mammalian development

Mammalian development is dependent on an intricate orchestration of cell proliferation and death. Deregulation in the levels, localization, and type of cell death can lead to disease and even death of the developing embryo. The mechanisms involved in such deregulation are many; alterations and or manipulations of these can aid in the detection, prevention and possible treatments of any effects this de-regulation may have. Here we describe how cell death can be detected during mammalian development, using diverse staining and microscopy methods, while taking advantage of the advancements in cell death mechanisms, derived from biochemical and teratological studies in the field.