Embryonic behavior of two-cell mouse embryos frozen by the one- and two-step ultrarapid techniques

Strategies for the cryopreservation of microencapsulated cells

The major challenge in developing cryopreservation protocols for microencapsulated cells is that the relatively large size (300-400 microm) and the fragile semipermeable membrane of microcapsules makes them particularly prone to cryodamage. Rapid-cooling cryopreservation protocols with high DMSO concentrations (3.5M, 25% v/v) resulted in low post-thaw cell viability (<10%), which did not improve with higher concentrations (4.5M, 32% v/v) and longer exposure to DMSO, even though the majority of microcapsules (60-80%) remained intact. Subsequent investigations of slow cooling with a range of DMSO and EG concentrations resulted in a much higher post-thaw cell viability (80-85%), with the majority of the microcapsules remaining intact ( approximately 60%) when DMSO was used at a concentration of 2.8M (20% v/v) and EG at a concentration of 2.7M (15% v/v). The presence of 0.25M sucrose significantly improved post-thaw cell viability upon slow cooling with 2.8M (20% v/v) DMSO, although it had no effect on microcapsule integrity. Multistep exposure and removal of sucrose did not significantly improve either post-thaw cell viability or microcapsule integrity, compared to a single-step protocol. Ficoll 20% (w/v) also did not significantly improve post-thaw cell viability and microcapsule integrity. Hence, the optimal condition for microcapsule cryopreservation developed in this study is slow cooling with 2.8M (20% v/v) DMSO and 0.25M sucrose.

Clinical experience with ultrarapid cryopreservation of human embryos resulting from intracytoplasmic sperm injection: brief communication

A total of 41 patients requested thawing of supernumerary embryos in an intracytoplasmic sperm injection (ICSI) programme. Mean patient age was 30.8 +/- 3.8 years. Embryo freezing by the ultrarapid method was performed at room temperature in 3 mol/l DMSO and 0.25 mol/l sucrose. Total freezing time was 2.5 min including filling of the straw. In the thawing process, the embryos were removed from liquid N(2), left at room temperature for 30 s, immersed for 40 s at 30 degrees C, and then successively transferred at room temperature for 10 min to each of three sucrose solutions of decreasing concentration. The embryos were kept in culture and only those that presented cleavage after 24 h were transferred. Embryos from 42 cycles were thawed and a total of 24 transfers was performed. The mean number of thawed embryos was 5.0 +/- 3.2 per cycle and the mean number of transferred embryos was 2.83 +/- 1.3. The clinical pregnancy rate per cycle obtained after the thawing process was 16. 6%. The clinical pregnancy rate per transfer was 29.2% and the implantation rate was 13.2%. The abortion rate was 14.3%. Six deliveries have been performed, with the birth of seven infants.

Ultrarapid cryopreservation of human embryos: experience with 1,582 embryos

OBJECTIVES

To demonstrate the effectiveness of ultrarapid cryopreservation in human embryos.

DESIGN

Retrospective study.

SETTING

An IVF unit of a medical center.

PATIENT(S)

All cases received ultrarapid freezing (URF) of embryos and frozen embryo transfer.

INTERVENTION(S)

Embryos were placed in phosphate-buffered saline (PB1) + 20% maternal serum (MS) for 5 minutes. Embryos were loaded to the straws containing PB1 + MS + 0.25 M sucrose (SUC) + 3.5 M dimethyl sulfoxide for 3 minutes, and then were stored in a liquid nitrogen tank. Embryos were thawed in a 37 degrees C water for 6 seconds and then cultured in PB1 + MS + SUC for 10 minutes. Embryos were transferred into PB1 + MS for 5 minutes and were transferred into patients.

MAIN OUTCOME MEASURE(S)

The embryo grades before and after URF, the survival and transferred embryo numbers, and the pregnancy and abortion rates were analyzed.

RESULT(S)

A total of 1,582 embryos were thawed, of which 1,273 (80.5%) embryos were transferred and 1,032 (65.2%) embryos survived with > or = 50% intact blastomere. The embryo numbers with grade I or II before and after freezing and thawing were 1,110 (70.2%) and 790 (50.0%). The mean embryo numbers per transfer was 5.0. Twenty-eight pregnancies (11.4% per transfer) were established, which included 5 miscarriages, 1 ectopic pregnancy, 4 preterm and 18 term deliveries.

CONCLUSION(S)

Ultrarapid freezing is worthy of reconsideration for embryo cryopreservation.

Pregnancies after transfer of ultrarapidly frozen human embryos

PURPOSE

We report our experience of freezing human embryos using an ultrarapid freezing method.

METHODS

The patients were superovulated. Oocytes were inseminated and cultured in HTF + 10% serum. A maximum of three embryos was transferred and the rest of the embryos were frozen ultrarapidly after a 3-min equilibration period in PB1 + 3.5 M DMSO + 0.25 M sucrose. Embryos were thawed in a 37 degrees C water bath for 6 sec, then cultured in PB1 + 20% serum for 10 min. The surviving embryos were transferred into patients on the same day of thawing.

RESULTS

Sixty-three embryos were thawed, of which 52 embryos (83%) survived with at least one intact blastomere. Nineteen frozen-thawed embryo transfers were made. The mean embryos per transfer was 2.7. Three pregnancies (16%/transfer) were established. One miscarriage occurred in the eighth week of pregnancy. Two pregnancies went to term and three healthy infants were born.

CONCLUSIONS

The present data demonstrate that ultrarapid freezing is a method worth consideration in the area of human embryo freezing.