Cryopreservation of mouse embryos at morula/compact stage

Slow freezing and vitrification of mouse morula and early blastocysts

PURPOSE

To assess the relative success of morula and early blastocyst slow freezing and vitrification in regards to survival and implantation rates utilising protocols which could be clinically implemented as a viable alternative to expanded blastocyst stage freezing.

METHODS

Mouse morula and early blastocysts were either slow frozen/thawed or vitrified/warmed. Their subsequent survival, blastocyst development and blastocyst cell number and allocation to either the inner cell mass, trophectoderm or epiblast was assessed. In addition blastocysts were also transferred to pseudopregnant recipients and implantation and fetal development was determined.

RESULTS

Vitrification of both morula and early blastocysts resulted in significantly higher rates of survival and blastocyst development compared to slow freezing. In addition slow frozen early blastocysts had significantly reduced blastocyst cell number compared to control however vitrified morula and early blasocyts and slow frozen morula had equivocal blastocyst cell numbers. Transfer of blastocysts from both methods of cryopreservation resulted in similar implantation rates however the placentas created from slow frozen early blastocysts were significantly lighter than control (95.5 g ± 5.4 vs. 122.0 g ± 4.2 respectively).

CONCLUSIONS

Vitrification resulted in significantly higher rates of morula and early blastocyst survival and blastocyst development compared to slow freezing. In addition this study has validated the use of a closed DMSO free vitrification protocol which could then be investigated for use in the clinical setting as an alternative to expanded blastocyst freezing.

The expression and distribution of aquaporin 3 in mouse embryos before and after vitrification

Purpose

To determine the role of aquaporin 3 (AQP3) isoform in early embryonic development and protecting embryos subjected to freeze–thawing for assisted reproduction, we investigated the expression and distribution of AQP3 in mouse embryos at different developmental stages before and after vitrification.

Methods

Eight-cell embryos, morulae, and blastocysts were obtained from female mice that had been superovulated by controlled ovarian hyperstimulation. Immunofluorescence staining, laser confocal microscopy, and Western blot were used to determine the expression and distribution of AQP3 in preimplantation mouse embryos before and after vitrification.

Results

AQP3 was expressed at the 8-cell to blastocyst stage before and after vitrification. The expression and distribution of AQP3 was developmentally regulated at the 8-cell to blastocyst stage. The expression of AQP3 was significantly decreased in 8-cell embryos and early blastocysts after vitrification. However, at the morulae stage, the expression of AQP3 was increased after vitrification.

Conclusions

The developmental and vitrification-dependent changes in AQP3 expression and distribution suggest that this transmembrane channel might regulate mouse embryo development and contribute to the protective response during vitrification.

Day 4 versus day 3 embryo transfer: a prospective study of clinical outcomes

OBJECTIVE

To compare the clinical outcomes after day 4 or day 3 embryo transfers in controlled ovarian hyperstimulation-IVF/intracytoplasmic sperm injection (ICSI) cycles.

DESIGN

Prospective randomized study.

SETTING

Center for Human Reproduction, 'Genesis Athens' Clinic (private gynecological and surgical clinic), Athens, Greece.

PATIENT(S)

Three hundred fifty women with primary infertility and indication for IVF/ICSI treatment. Patients were randomly allocated to day 4 or day 3 embryo transfer.

INTERVENTION(S)

Controlled ovarian hyperstimulation, oocyte retrieval, IVF/ICSI, embryo transfer.

MAIN OUTCOME MEASURE(S)

Implantation rate; clinical, ongoing, and multiple pregnancy rates.

RESULT(S)

A trend toward higher clinical and ongoing pregnancy rates was noted after day 4 embryo transfers. Implantation and multiple pregnancy rates were comparable after day 4 or day 3 embryo transfers.

CONCLUSION(S)

The transfer of day 4 embryos in IVF/ICSI cycles may result in favorable implantation and pregnancy rates which are at least comparable to those after the transfer of day 3 embryos.

Cryopreservation of human embryos at the morula stage and outcomes after transfer

OBJECTIVE

To evaluate the survival rate of human morula embryo freezing and the morphological alterations during freezing, during and after thawing, and their applications in embryo selection.

DESIGN

Retrospective observational study.

SETTING

Private infertility clinic.

PATIENT(S)

Consecutive patients under age 39 undergoing frozen morula embryo transfers from December 1999 to May 2003.

INTERVENTION(S)

Embryo freezing was performed at the morula stage. Embryo thaw and post-thaw ETs were conducted on the same day, which is equivalent to a day 4 ET.

MAIN OUTCOME MEASURE(S)

Morphological alterations during freezing and thawing and after thawing. Post-thaw embryo survival rates, transferable rates, pregnancy rates, and implantation rates.

RESULT(S)

Morula embryos showed reversed morphological alterations during the freezing process; these alterations were recovered during thawing or shortly after the thawing. Post-thaw survival rates showed no significant difference between any of the morula substages. However, embryos scored as grade 3, which represented good quality, had significantly higher post-thaw survival and transferable rates than grade 2 and 1 embryos. Patients who received at least one grade 3 embryo had significantly higher pregnancy rates, implantation rates, and ongoing/live birth rates than other groups.

CONCLUSION(S)

An acceptable survival rate can be achieved after cryopreservation of human morula embryos, and morphological alterations that occur during and shortly after an embryo thaw can be a feasible index for determining viable embryos.

The neglected morula/compact stage embryo transfer

BACKGROUND

This retrospective study analysed the outcomes of 339 embryo transfers on either day 3 (n = 97) or day 4 (n = 242), and proposed a grading system for morula/compact embryos.

METHODS

The morula/compact embryo grading was based on: (i) the proportion of blastomeres undergoing the compaction process; (ii) the morphology of the compacted multicellular mass; (iii) the embryo quality on day 2 and 3; and (iv) the amount of fragmentation. Embryo transfers were classified into groups as follows: group I: transferred with zero 'good' embryos; group II: one 'good' embryo; group III: two or more 'good' embryos.

RESULTS

Patients on day 4 were transferred with significantly fewer embryos in groups II and III (2.58 +/- 0.9 and 2.35 +/- 0.6 respectively) when compared with the correspondent day 3 transfers (3.81 +/- 1.4 and 4.07 +/- 0.9 respectively) (P < 0.05), but had the same or higher implantation and pregnancy rates. Analysing the patients who had transfers with all 'good' embryos, day 4 transfer achieved a significantly higher implantation rate compared with day 3 transfer (46.4 versus 21.4%, P < 0.01), but the number of embryos transferred on day 4 was significantly lower than day 3 (2.1 +/- 0.5 versus 3.5 +/- 0.9, P < 0.01).

CONCLUSIONS

The morula/compact embryos had great value for embryo selection, which significantly reduced the number of embryos needed for transfer.