Improvement of development of vitrified two-cell mouse embryos by vero cell coculture

Quality of vitrified porcine immature oocytes is improved by coculture with fresh oocytes during in vitro maturation

It is essential to enhance the in vitro maturation (IVM) condition for immature oocytes after cryopreservation, particularly if limited numbers of oocytes collected from specific donors. The objective of this study was to determine if quality of vitrified porcine immature oocytes was enhanced by coculturing with fresh oocytes during IVM. To distinguish fresh versus vitrified oocytes, we used two types of coculture systems: (a) transwell two-chamber coculture; (b) labeling and tracing fresh oocytes with CellTracker™ Green CMFDA during conventional culture. Coculture systems significantly accelerated meiotic progression of vitrified oocytes and significantly increased blastocyst formation rates following parthenogenetic activation and somatic cell nuclear transfer. Reactive oxygen species generation in vitrified oocytes was ameliorated by the coculture conditions, with no significant difference between fresh and vitrified oocytes for intracellular glutathione level. Both coculture systems significantly increased rate of normal mitochondrial distribution in vitrified oocytes, but did not affect fluorescence intensity of mitochondria. The percentage of oocytes with normal endoplasmic reticulum (ER) distribution and ER fluorescence intensity were significantly higher in vitrified oocytes cocultured with fresh oocytes. After 20 hr of IVM, mRNA expression of COX2, HAS2, PTX3, and TNFAIP6 remained significantly higher in cumulus cells derived from vitrified oocytes and coculture systems significantly decreased the expression of these genes. Additionally, coculture methods prevented the reduction of mRNA expression for BMP15, ZAR1, POU5F1, and DNMT3A in vitrified oocytes. In conclusion, oocyte quality and subsequent embryo development of vitrified porcine immature oocytes were significantly improved by fresh oocyte coculture during IVM.

Closed-system solid surface vitrification versus slow programmable freezing of mouse 2-cell embryos

PURPOSE

To compare closed-system solid surface vitrification with slow freezing.

METHODS

Mouse 2-cell embryos (n = 348) were divided into vitrification, slow freezing and non-frozen groups. For vitrification, embryos were exposed to 10% ethylene glycol (EG), 10% dimethylsulfoxide (DMSO) and 10% fetal bovine serum (FBS) in phosphate-buffered saline (PBS) for 10 min, then transferred into 17.5% EG, 17.5% DMSO, 0.25 M trehalose and 10% FBS in PBS. They were placed on hemi-straws and inserted into 0.5 ml straws inside a previously cooled aluminum cylinder. Slow freezing was done in straws by the conventional method.

RESULTS

Vitrified embryos had significantly higher survival, further cleavage and blastocyst formation rates than those in the slow freezing group (p < 0.001) and were comparable to controls. Blastocysts in the vitrification and control groups had significantly more cells than those in the slow freezing group (p < 0.05).

CONCLUSIONS

Closed-system vitrification was more effective than conventional slow freezing.

Development of vitrified-warmed mouse embryos co-cultured with polarized or non-polarized uterine epithelial cells using sequential culture media

PURPOSE

To our knowledge, little is known about the effect of polarized and non-polarized uterine epithelial cells on cryopreserved embryo growth. This study was, therefore, set up to investigate the effect of these monolayers together with sequential culture media on vitrified-warmed mouse embryos in terms of blastocyst development, blastocyst quality, incidence of apoptosis and related genes expression.

METHODS

Two cell vitrified-warmed mouse embryos were cultured in G-1ver3 medium to the eight-cell stage when they were randomly assigned to three treatment groups of no co-culture (control), non-polarized and polarized mouse uterine epithelial monolayer co-culture. The culture medium was G-2ver3 during the treatment phase. After 96 h on treatment, the significance of differences were evaluated by the one way analysis of variance for continuous data.

RESULTS

In the polarized monolayer group, the hatched blastocyst formation and blastocyst quality improved significantly than other two groups (P < 0.05). Whereas the incidence of apoptosis and related gene expression such as Bax were higher in the blastocysts of control group (P < 0.05). The relative abundance of Bcl-2 mRNA to the beta-tubulin was similar for all treatments.

CONCLUSION

Co-culture system involving polarized uterine epithelial cells and sequential culture media is a promising method for the improvement of vitrified-warmed mouse embryo development.

Granulocyte-macrophage colony stimulating factor (GM-CSF) and co-culture can affect post-thaw development and apoptosis in cryopreserved embryos

PURPOSE

The objective of this study was to evaluate the effects of growth factor supplementation and Vero cell co-culture on apoptosis and development of frozen thawed one-cell mouse embryos.

METHODS

The following treatment regimens were assessed: (a) control medium (b) Vero cell co-culture and (c) growth factor supplemented medium. The individual growth factors tested were: GM-CSF, IGF-I, IGF-II, TNF-alpha, FGF-4, LIF, TGF-alpha, TGF-beta, IL-6, PDGF and EGF. Blastocyst development and differentiation were monitored. At termination of the experiments, overall blastomere number and apoptosis were assessed using the TUNEL assay.

RESULTS

No differences were observed in blastulation and hatching rates. ICM differentiation in thawed embryos was notably improved with either co-culture or growth factor supplementation. The only growth factor significantly modulating apoptosis in thawed embryos was granulocyte-macrophage colony stimulating factor (GM-CSF). GM-CSF enhanced continued cell survival and prevented apoptosis but did not influence overall cell number in developing blastocysts. Vero cell co-culture significantly increased cell number in blastocysts (124+/-42 vs 100+/-44 in control; P<0.05). Embryonic apoptosis was higher in the co-cultured embryos. The increased presence of apoptotic cells in blastocysts of high cell number may reflect the regulatory role of apoptosis in balancing ICM: TE ratios.

CONCLUSION

These data indicate that culture conditions can modulate post-thaw embryonic development and apoptosis.