Micromanipulation of cryopreserved embryos and cryopreservation of micromanipulated embryos in PGD

Short-term storage of tripronucleated human embryos

PURPOSE

To determine the survival and subsequent in vitro development of human cleavage stage embryos and hatched blastocysts following varying periods of short-term storage at 4 °C, using tripronucleated human embryos (TPN) as a model.

METHODS

TPN cleavage embryos and hatched blastocysts short-term stored at 4 °C for 0 h (control), 24 h and 48 h. The main outcome measures were: survival rates (SR) and in vitro developmental ability (blastocyst rate and blastocyst-re-expansion rate) in each of the groups after storage.

RESULTS

Cleavage-stage TPN survived at comparable rates to controls, regardless of storage time (average: 97.3 %). The in vitro development of cleavage-stage TPN stored for 24 h was comparable to that of controls (average 64.7 %), but was significantly impaired when storage lasted 48-h (20.8 %). After artificial shrinkage, SR was comparable in 24-h-stored and non-stored hatched blastocysts (85.7 %; p > 0.05), but was significantly impaired in the 48-h-stored group (20.0 %). Following 24-h storage, the re-expansion rate of hatched blastocysts was similar to that of controls (average: 57.1 %; p > 0.05), but was higher than that of the 48-h-stored group (15.0 %; p < 0.05).

CONCLUSIONS

TPN human cleavage embryos and blastocysts can be successfully stored short-term for up to 24 h at 4 °C without using cryoprotectants without any significant negative impact on survival or subsequent in vitro development.

Reliable preimplantation genetic diagnosis in thawed human embryos vitrified at cleavage stages without biopsy

PURPOSE

To evaluate preimplantation genetic diagnosis (PGD) efficiency in thawed human embryos vitrified without biopsy.

METHODS

In this retrospective clinical study, 21 PGD cycles were carried out using fresh and vitrified-thawed embryos collected from 21 patients.

RESULTS

One hundred and ninety-nine embryos from patients with aneuploidy, single gene defects, or chromosomal translocations were vitrified at the cleavage stages; 93.5% of the embryos survived the vitrification procedure. Conclusive FISH results were obtained in 98.4% of the fresh and 99% of the frozen-thawed embryos screened for aneuploidy or chromosomal translocations. Conclusive PCR test results were obtained in 100% of the fresh and 93.9% of the frozen-thawed embryos screened for single gene defects. The overall clinical pregnancy rate per cycle was 57.1%. To date, 13 healthy children have been born.

CONCLUSION

Reliable genetic diagnosis can be performed in thawed human embryos vitrified without biopsy. However, further research is required to support this conclusion.

PGD for fragile X syndrome: ovarian function is the main determinant of success

BACKGROUND

PGD for fragile X syndrome (FRAX) is inefficient, probably owing to fewer oocytes, poor embryo quality and difficulties in genetic analysis. We investigated IVF-PGD in FRAX mutation carriers compared with controls, looking at the effects of oocyte and embryo number/quality on live birth outcome.

METHODS

We performed IVF-PGD in 27 patients with the FRAX mutation and 33 controls with other genetic diseases. Genetic testing was by multiplex PCR.

RESULTS

Seventy-nine and 108 IVF-PGD cycles were started in FRAX mutation carriers and controls, respectively. Twenty-two patients had a premutation (CGG repeat number 60-200) and five had a full mutation (300-2000 CGG repeats). FRAX patients required higher doses of gonadotrophins (6788 ± 2379 versus 4360 ± 2330, P< 0.001) but had lower peak serum estradiol levels (8166 ± 5880 versus 10 211 ± 4673, P = 0.03) and fewer oocytes retrieved (9.8 ± 6 versus 14 ± 8, P = 0.01). The cancellation rate (unsatisfactory ovarian response) was higher in the FRAX group than in the control group (13 versus 1%, P < 0.001). When embryos were transferred, ongoing pregnancy/live birth rates per transfer were similar (29 versus 36%, P = 0.54).

CONCLUSIONS

Ovarian dysfunction in FRAX carriers is more prevalent and profound than previously appreciated, with a high cancelation rate and reduced efficiency of PGD. The main determinant for successful PGD for FRAX is ovarian dysfunction. When embryo transfer is possible, the results are comparable to PGD for other monogenic diseases.

New options in assisted reproduction technology: the Cryotop method of oocyte vitrification

The Cryotop vitrification method has been shown to be a very useful tool for oocyte cryopreservation, giving excellent results regarding survival and clinical outcome. There are several clinical situations in which oocyte cryopreservation provides solutions that have not been available to date. This report describes three of these situations: (i) a low-responder patient who needed a single gene diagnosis due to the presence of a genetic disease; (ii) a patient undergoing endometrial bleeding on the day of oocyte retrieval who was also affected by a genetic disorder; and (iii) a patient who failed to become pregnant after the donation of vitrified oocytes and subsequently had the re-vitrified surplus embryos transferred. The resolution of these cases provides evidence of the enormous potential of the Cryotop method as a tool within assisted reproduction technology.

A live birth after transfer of a day 2 embryo derived from frozen-thawed zygotes that had undergone polar body biopsy: a case report

OBJECTIVE

To present a live birth after freezing and thawing of biopsied oocytes.

DESIGN

Case report.

SETTING

Artificial reproduction unit of a university hospital.

PATIENT(S)

A primary infertile couple with asthenoteratozoospermia and repeated failures of intracytoplasmic sperm injection (ICSI).

INTERVENTION(S)

Screening of aneuploidy during the fourth ICSI cycle with polar body biopsy (PB) for repeated failures of artificial reproductive techniques and a transfer of a cryopreserved day 2 embryo derived from cryopreserved zygotes with slow-rate freezing after PB.

MAIN OUTCOMES MEASURE(S)

Live birth, viability, and survival.

RESULT(S)

A successful pregnancy and a live birth were presented after a transfer of day 2 embryos derived from oocytes that underwent PB and subsequent cryopreservation.

CONCLUSION(S)

Pregnancy can be obtained subsequent to cryopreservation and thawing after PB.

Vitrification of preimplantation genetically diagnosed human blastocysts and its contribution to the cumulative ongoing pregnancy rate per cycle by using a closed device

OBJECTIVE

To evaluate the survival rate and clinical results of our vitrification procedure on preimplantation genetic diagnosis (PGD) blastocysts and to calculate its actual contribution to the reproductive outcome per cycle.

DESIGN

Retrospective clinical study.

SETTING

University Institute IVI, Valencia, Spain.

PATIENT(S)

Patients who requested cryotransfer of surplus PGD blastocysts after failed fresh elective transfer.

INTERVENTION(S)

Retrospectively collected data during 2 years of experience with blastocyst vitrification.

MAIN OUTCOME MEASURE(S)

Primary outcome measures were the following: blastocyst recovery and survival; cryotransfer cancellation; and the implantation, pregnancy (PR), and ongoing-pregnancy rates. The secondary outcome measure was cumulative ongoing PR (COPR).

RESULT(S)

Cocultured vitrified PGD blastocysts were recovered and progressed in development after overnight culture (survival rate) at rates comparable to those of non-PGD blastocysts (49% and 42%, respectively). After transfer to 64% of patients, no statistical differences were found between PGD and non-PGD blastocyst groups concerning the following: PR (44% vs. 37%), implantation rate (40% vs. 27%), and ongoing-pregnancy rate (32% vs. 37%). Moreover, blastocyst vitrification significantly increased the COPR in both PGD and non-PGD cycles, from 47% (62/133) to 53% (70/133) and from 45% (24/53) to 53% (28/53), respectively.

CONCLUSION(S)

A preimplantation genetic diagnosis blastocyst vitrification procedure showed survival rates and improvements on the COPR that were comparable to those in non-PGD blastocyst cycles. Moreover, vitrification of biopsied and diagnosed embryos at the more advanced stages instead of at earlier cleavage stages is presented as an attractive strategy to consider in PGD programs.

Ultrastructure of preimplantation genetic diagnosis-derived human blastocysts grown in a coculture system after vitrification

OBJECTIVE

To evaluate ultrastructural features of preimplantation genetic diagnosis (PGD) blastocysts before and after vitrification.

DESIGN

Descriptive study of both vitrified and fresh hatching blastocysts.

SETTING

PGD program at the Instituto Universitario, Instituto Valenciano de Infertilidad.

PATIENT(S)

Patients undergoing PGD donated their abnormal embryos for research (n = 26).

INTERVENTION(S)

Biopsied embryos were cultured in the presence of human endometrial cells until day 6. Sixteen blastocysts were vitrified. A total of 11 high-scored hatching blastocysts, 6 warmed and 5 fresh, were fixed for ultrastructure.

MAIN OUTCOME MEASURE(S)

The cytoskeleton structure, type of intercellular junctions, and basic intracellular organelles in trophoectoderm cells and the inner cell mass were analyzed.

RESULT(S)

Ten of 16 blastocysts (62%) survived the warming process. Six of these showed no signs of cell degeneration and light microscopy revealed similar ultrastructural characteristics to those of controls. However, in trophoectoderm cells from both fresh and cryopreserved blastocysts, a reduced number of tight junctions and the presence of degradation bodies were detected.

CONCLUSION(S)

The particular ultrastructural features observed in PGD-derived blastocysts could be related to embryo manipulation and culture conditions. Vitrification does not seem to alter blastocysts, as those that survive hatching do not display detectable cellular alterations when observed through electron microscopy.

Preimplantation genetic diagnosis of skin fragility-ectodermal dysplasia syndrome

Skin fragility-ectodermal dysplasia syndrome is an autosomal recessive disorder caused by loss-of-function mutations in the desmosomal protein, plakophilin 1. Clinically, there may be considerable morbidity from extensive skin erosions and painful fissures on the palms and soles. In the absence of any specific treatment, prenatal diagnosis is an option for couples at reproductive risk of recurrence. In 2000, we developed and applied a single cell nested polymerase chain reaction protocol to test one couple for compound heterozygous plakophilin 1 gene mutations by preimplantation genetic diagnosis (PGD). Although pregnancy was established, an unrelated trisomy 22 led to a spontaneous abortion. However, eight embryos of known genetic status were cryopreserved at that stage, and we planned to undertake subsequent frozen embryo replacement cycles that might lead to the birth of an unaffected child in this family. Embryo cryopreservation was carried out in June 2000 using standard protocols in a three-step freezing procedure. Four embryos were thawed in March 2003, one of which was viable and was used in a frozen embryo replacement cycle, but pregnancy did not occur. The remaining four embryos were thawed in February 2004, two of which were viable (both carriers of the paternal mutation) and these were used in a second frozen embryo replacement cycle, and a singleton pregnancy was established. The child's plakophilin 1 genotype was assessed by direct nucleotide sequencing across the site of both potential mutations. Following two frozen embryo replacement cycles, and almost 4 years after the initial embryo biopsy and mutation analysis, a pregnancy was achieved that progressed to term with the birth of a healthy baby girl. Nucleotide sequencing of cord blood DNA, taken immediately after delivery, showed that the child was a heterozygous carrier of the paternal mutation but not of the maternal mutation. This case demonstrates the value of embryo cryopreservation, which can increase the number of embryo replacement procedures and hence the cumulative pregnancy rate per retrieval cycle. Moreover, this is the first report of successful full-term pregnancy and birth of a healthy baby following exclusion of a severe genodermatosis by PGD. The successful outcome of PGD in this case illustrates what is technically possible for couples at risk of recurrence of a severe inherited skin disease.

Embryo aneuploidy screening for repeated implantation failure and unexplained recurrent miscarriage

Among other factors, chromosomal abnormalities that originate from gametogenesis and preimplantation embryonic development are thought to be one of the major contributing factors for early embryonic death and failure of pregnancy. However, so far, no non-invasive technique exists that allows the detection of the chromosomal complement of an oocyte or a developing embryo as a whole. Rather, by removing polar bodies/blastomeres, recent developments on preimplantation genetic diagnosis for aneuploidy screening (PGD-AS) have paved the way to detect and possibly eliminate the majority of chromosomally abnormal embryos, thereby increasing the chance of a healthy pregnancy. This article summarizes the origin and impact of chromosomal abnormalities on human reproduction in cases with repeated implantation failure (RIF) and unexplained recurrent miscarriage. It also discusses recent advances regarding the possible benefits of PGD-AS in such cases.

Comparison of the survival of human biopsied embryos after cryopreservation with four different methods using non-transferable embryos

BACKGROUND

The standard embryo cryopreservation method is still less than optimal for biopsied embryos. The aim of this study was to compare the survival of biopsied embryos cryopreserved with four different methods using non-transferable embryos.

METHODS

Abnormal embryos from one or three pronuclei and spare embryos of grade 3 and 4 were used for this study. Non-biopsied embryos were cryopreserved using the standard method as control. Biopsied embryos were cryopreserved using four methods as follows: standard method, modified freezing method, modified thawing method and vitrification. Blastomere survival and blastulation of frozen-thawed embryos were compared between the different methods.

RESULTS

The proportion of embryos with > or = 50% blastomere survival and total blastomere survival rate of biopsied embryos were significantly higher with vitrification than the other three methods. Both the modified freezing and modified thawing methods had significantly higher embryo survival and total blastomere survival rates than standard methods. However, there was no significant difference in blastulation of surviving embryos in all the five groups.

CONCLUSIONS

Non-transferable embryos derived from clinical IVF/ICSI are useful for evaluation of the optimal freezing procedures for biopsied embryos. Vitrification increases the survival rate of human biopsied embryos above standard and modified cryopreservation methods.

Cryopreservation of biopsied cleavage stage human embryos

The aim was to develop a method to optimize cryopreservation of biopsied multi-celled human embryos. Human day 3 embryos that were donated to research, along with those found to be chromosomally abnormal after blastomere biopsy and fluorescence in-situ hyridization (FISH), were cryopreserved using a slow-freezing protocol in either standard embryo cryopreservation solution [embryo transfer freezing medium (ETFM), a conventional sodium-based medium] or CJ3 (a choline-based, sodium-free medium). After thawing, the number of intact cells was recorded and the previously biopsied embryos were re-analysed using FISH. Biopsied embryos had a lower proportion of intact blastomeres after cryopreservation as compared with intact embryos. However, a significantly (P < 0.05) higher proportion of blastomeres from intact and biopsied embryos cryopreserved in CJ3 (84.1 and 80.1% respectively) survived after thaw than those in ETFM (73.6 and 50.5% respectively). The proportion of aneuploid and mosaic embryos was not statistically different between the two groups. In addition, the frequency of lost cells by aneuploid and mosaic embryos was similar. This study describes a new method that improves the survival of cryopreserved biopsied embryos, and shows that it may also be beneficial for the storage of intact human multi-celled embryos.

ESHRE PGD Consortium ‘Best practice guidelines for clinical preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS)’

Among the many educational materials produced by the European Society of Human Reproduction and Embryology (ESHRE) are guidelines. ESHRE guidelines may be developed for many reasons but their intent is always to promote best quality practices in reproductive medicine. In an era in which preimplantation genetic diagnosis (PGD) has become a reality, we must strive to maintain its efficacy and credibility by offering the safest and most effective treatment available. The dominant motivators for the development of current comprehensive guidelines for best PGD practice were (i) the absence of guidelines and/or regulation for PGD in many countries and (ii) the observation that no consensus exists on many of the clinical and technical aspects of PGD. As a consequence, the ESHRE PGD Consortium undertook to draw up guidelines aimed at giving information, support and guidance to potential, fledgling and established PGD centres. The success of a PGD treatment cycle is the result of great attention to detail. We have strived to provide a similar level of detail in this document and hope that it will assist staff in achieving the best clinical outcome for their patients.

Preimplantation genetic diagnosis and chromosome analysis of blastomeres using comparative genomic hybridization

Numerical chromosome errors are known to be common in early human embryos and probably make a significant contribution to early pregnancy loss and implantation failure in IVF patients. Over recent years fluorescent in situ hybridization (FISH) has been used to document embryonic aneuploidies. Many IVF laboratories perform preimplantation genetic diagnosis (PGD) with FISH to select embryos that are free from some aneuploidies in an attempt to improve implantation, pregnancy and live birth rates in particular categories of IVF patients. The usefulness of FISH is limited because only a few chromosomes can be detected simultaneously in a single biopsied cell. Complete karyotyping at the single cell level can now be achieved by comparative genomic hybridization (CGH). CGH enables not only enumeration of all chromosomes but gives a more complete picture of the entire length of each chromosome and has demonstrated that chromosomal breakages and partial aneuploidies exist in embryos. CGH has provided invaluable information about the extent of mosaicism and aneuploidy of all chromosomes in early human conceptuses. CGH has been applied to clinical PGD and has resulted in the birth of healthy babies from embryos whose full karyotype was determined in the preimplantation phase.

First clinical application of comparative genomic hybridization and polar body testing for preimplantation genetic diagnosis of aneuploidy

OBJECTIVE

To develop a preimplantation genetic diagnosis (PGD) protocol that allows any form of chromosome imbalance to be detected.

DESIGN

Case report employing a method based on whole-genome amplification and comparative genomic hybridization (CGH).

SETTING

Clinical IVF laboratory.

PATIENT(S)

A 40-year-old IVF patient.

INTERVENTION(S)

Polar body and blastomere biopsy.

MAIN OUTCOME MEASURE(S)

Detection of aneuploidy.

RESULT(S)

Chromosome imbalance was detected in 9 of 10 polar bodies. A variety of chromosomes were aneuploid, but chromosomal size was found to be an important predisposing factor. In three cases, the resulting embryos could be tested using fluorescence in situ hybridization, and in each case the CGH diagnosis was confirmed. A single embryo could be recommended for transfer on the basis of the CGH data, but no pregnancy ensued.

CONCLUSION(S)

Evidence suggests that preferential transfer of chromosomally normal embryos can improve IVF outcomes. However, current PGD protocols do not allow analysis of every chromosome, and therefore a proportion of abnormal embryos remains undetected. We describe a method that allows every chromosome to be assessed in polar bodies and oocytes. The technique was accurate and allowed identification of aneuploid embryos that would have been diagnosed as normal by standard PGD techniques. As well as comprehensive cytogenetic analysis, this protocol permits simultaneous testing for multiple single-gene disorders.