Assessment of aneuploidy formation in human blastocysts resulting from cryopreserved donor eggs

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Abstract

Background

Increased embryo implantation rates were reported after transfer of euploid embryos selected by preimplantation genetic screening (PGS). Egg cryopreservation by vitrification has become one of the most important assisted human reproduction technologies. Although reports indicate that development and implantation of human embryos derived from frozen donor eggs are comparative to fresh eggs, it is still unknown whether egg vitrification increases chromosomal abnormalities in eggs, which in turn causes formation of embryonic aneuploidy. Therefore, in this study, we evaluated the aneuploidy formation in the blastocysts derived from frozen donor eggs and also evaluated the efficiency of egg vitrification as an advanced technology for egg cryopreservation.

Results

In this study, donated human eggs from young women were cryopreserved by vitrification and PGS was performed in the resulted blastocysts by DNA microarray. A total of 764 frozen eggs from 75 egg thawing cycles were warmed and 38 blastocysts were biopsied for PGS before embryo transfer. A 97.1% of egg survival rate was obtained and 59.1% of embryos developed to blastocyst stage. After biopsy and PGS, it was found that 84.2% of blastocysts were euploid and 15.8% were aneuploid. Aneuploidy rates varied among donors. Transfers of blastocysts without PGS resulted in higher clinical pregnancy and implantation rates as compared with transfer of blastocysts with PGS.

Conclusions

Although the overall aneuploidy rate was low in the blastocysts derived from frozen donor eggs, high aneuploidy rates were observed in the embryos resulting from some donated eggs. Clinical pregnancy rate was not improved by PGS of embryos resulting from donor eggs, indicating that PGS may not be necessary for embryos derived from donor eggs in most cases.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-015-0117-8) contains supplementary material, which is available to authorized users.

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Most cited references 40

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Milder ovarian stimulation for in-vitro fertilization reduces aneuploidy in the human preimplantation embryo: a randomized controlled trial.

Elena Martini, Arie Verhoeff, Nicholas S Macklon … (2007)

To test whether ovarian stimulation for in-vitro fertilization (IVF) affects oocyte quality and thus chromosome segregation behaviour during meiosis and early embryo development, preimplantation genetic screening of embryos was employed in a prospective, randomized controlled trial, comparing two ovarian stimulation regimens. Infertile patients under 38 years of age were randomly assigned to undergo a mild stimulation regimen using gonadotrophin-releasing hormone (GnRH) antagonist co-treatment (67 patients), which does not disrupt secondary follicle recruitment, or a conventional high-dose exogenous gonadotrophin regimen and GnRH agonist co-treatment (44 patients). Following IVF, embryos were biopsied at the eight-cell stage and the copy number of 10 chromosomes was analysed in 1 or 2 blastomeres. The study was terminated prematurely, after an unplanned interim analysis (which included 61% of the planned number of patients) found a lower embryo aneuploidy rate following mild stimulation. Compared with conventional stimulation, significantly fewer oocytes and embryos were obtained following mild stimulation (P < 0.01 and < 0.05, respectively). Consequently, both regimens generated on average a similar number (1.8) of chromosomally normal embryos. Differences in rates of mosaic embryos suggest an effect of ovarian stimulation on mitotic segregation errors. Future ovarian stimulation strategies should avoid maximizing oocyte yield, but aim at generating a sufficient number of chromosomally normal embryos by reduced interference with ovarian physiology.

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Embryo development of fresh ‘versus’ vitrified metaphase II oocytes after ICSI: a prospective randomized sibling-oocyte study

Laura Rienzi, Stefania Romano, Laura Albricci … (2009)

BACKGROUND A successful oocyte cryopreservation programme is of utmost importance where a limited number of oocytes can be inseminated per cycle, to overcome legal and ethical issues related to embryo storage, for oocyte donation programmes and for fertility preservation (especially for cancer patients). Vitrification has been recently proposed as an effective procedure for this purpose. METHODS In order to validate the effectiveness of oocyte vitrification a non-inferiority trial was started on sibling metaphase II (MII) oocytes. To demonstrate the non-inferiority based on an absolute difference of 17% in the fertilization rate per sibling oocyte, a minimum of 222 oocytes were required. After oocyte denudation, MII oocytes with normal morphology were randomly allocated to fresh ICSI insemination or to vitrification procedure. If pregnancy was not obtained a subsequent ICSI cycle was performed with warmed oocytes of the same cohort. In both groups, three oocytes were inseminated per cycle by ICSI procedure. Primary end-points were fertilization rates calculated per warmed and per injected oocytes. Secondary end-points were zygote and embryo morphology. RESULTS A total of 244 oocytes were involved in this study. Of the 120 fresh sibling oocytes inseminated, 100 were fertilized (83.3%). Survival rate of sibling vitrified oocytes was 96.8% (120/124 oocytes). Fertilization rate after ICSI was 76.6% (95/124) per warmed oocyte and 79.2% (95/120) per survived/inseminated oocyte. No statistical difference in fertilization rates was observed between the two groups when calculated per sibling oocytes (absolute difference −6.73%; OR: 0.65; 95% CI = 0.33–1.29; P = 0.20) and per inseminated oocyte (absolute difference −4.17%; OR: 0.76; 95% CI = 0.37–1.53; P = 0.50). Embryo development was also similar in both treatment groups up till Day 2. The percentage of excellent quality embryos was 52.0% (52/100) in the fresh group and 51.6% (49/95) in the vitrification group (absolute difference −0.43%; OR: 0.98; 95% CI = 0.53–1.79; P = 0.9). The mean age of the 40 patients included in this study was 35.5 ± 4.8 years (range 26–42). Fifteen clinical pregnancies were obtained in the vitrification cycles of 39 embryo transfers performed (37.5% per cycle, 38.5% per embryo transfer), with an implantation rate of 20.2% (19/94). Three spontaneous miscarriages occurred (20%). Twelve pregnancies are ongoing (30.0% per cycle, 30.8% per embryo transfer) beyond 12 weeks of gestation. CONCLUSIONS Our results indicate that oocyte vitrification procedure followed by ICSI is not inferior to fresh insemination procedure, with regard to fertilization and embryo developmental rates. Moreover, ongoing clinical pregnancy is compatible with this procedure, even with a restricted number of oocytes available for insemination. The promising clinical results obtained, in a population of infertile patients, need to be confirmed on a larger scale. Clinical Trials Registration number: iSRCTN60158641.

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Comparison of concomitant outcome achieved with fresh and cryopreserved donor oocytes vitrified by the Cryotop method.

Ana Maria Cobo, Masashigue Kuwayama, Sonia Pérez … (2008)

To evaluate the outcome of oocyte vitrification using the Cryotop method, observed in an egg donation program by simultaneously evaluating embryos derived from vitrified and fresh oocytes coming from the same stimulated cycle. Cohort prospective randomized study. Instituto Valenciano de Infertilidad (IVI) Valencia, Spain. Thirty oocyte donors and 30 recipients with informed consents. Vitrification by the Cryotop method. Warming 1 hour after vitrification. Microinjection of surviving MII and fresh oocytes, evaluation of fertilization, embryo development, and clinical results. Survival, fertilization, and cleavage rate. Embryo quality, pregnancy rate (PR), and implantation rate. Survival rate observed was 96.7%. There was no difference in fertilization rates (76.3% and 82.2%), day 2 cleavage (94.2% and 97.8%), day 3 cleavage (80.8% and 80.5%), and blastocyst formation (48.7% and 47.5%) for vitrified and fresh oocytes, respectively. Embryo quality on day 3 and on day 5-6 were similar for vitrification and fresh oocyte group (80.8% vs. 80.5% and 81.1% vs. 70%, respectively). A total of 23 embryo transfers were carried out in the vitrification group. Pregnancy rates, implantation rates, miscarriage rates, and ongoing PR were 65.2%, 40.8%, 20%, and 47.8%, respectively. The Cryotop method preserves the potential of vitrified oocytes to fertilize and further develop, which is similar, when evaluated simultaneously, to fresh counterparts. Excellent clinical outcome indicates the possible use of this technology for egg donation programs, as well as a high potential for establishing oocyte banking.

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Author and article information

Contributors

Aimin Deng: Dengaimind@126.com

Wei-Hua Wang: wangweihua11@yahoo.com

Journal

Journal ID (nlm-ta): Mol Cytogenet

Journal ID (iso-abbrev): Mol Cytogenet

Title: Molecular Cytogenetics

Publisher: BioMed Central (London )

ISSN (Electronic): 1755-8166

Publication date (Electronic): 15 February 2015

Publication date PMC-release: 15 February 2015

Publication date Collection: 2015

Volume: 8

Electronic Location Identifier: 12

Affiliations

[ ]Center for Reproductive Medicine, Changsha Hospital for Maternal and Child Health Care, No. 416, Chengnan East Road, Changsha City, Hunan China

[ ]Houston Fertility Laboratory, Vivere Health, Houston, TX USA

[ ]Houston Fertility Institute, 2500 Fondren Road, Suite 350, Houston, TX 77063 USA

Article

Publisher ID: 117

DOI: 10.1186/s13039-015-0117-8

PMC ID: 4339107

SO-VID: 30c6662e-0044-47e3-94c4-b138eb2ead2a

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

History

Date received : 13 January 2015

Date accepted : 5 February 2015

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ScienceOpen disciplines: Genetics

Keywords: aneuploidy,egg freezing,donor eggs,implantation

Data availability:

ScienceOpen disciplines: Genetics

Keywords: aneuploidy, egg freezing, donor eggs, implantation

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Assessment of aneuploidy formation in human blastocysts resulting from cryopreserved donor eggs

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Most cited references 40

Milder ovarian stimulation for in-vitro fertilization reduces aneuploidy in the human preimplantation embryo: a randomized controlled trial.

Embryo development of fresh ‘versus’ vitrified metaphase II oocytes after ICSI: a prospective randomized sibling-oocyte study

Comparison of concomitant outcome achieved with fresh and cryopreserved donor oocytes vitrified by the Cryotop method.

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