Hydatidiform mole following in-vitro fertilization. Case report

Genome stability of bovine in vivo-conceived cleavage-stage embryos is higher compared to in vitro-produced embryos

STUDY QUESTION

Is the rate and nature of chromosome instability (CIN) similar between bovine in vivo-derived and in vitro-cultured cleavage-stage embryos?

SUMMARY ANSWER

There is a major difference regarding chromosome stability of in vivo-derived and in vitro-cultured embryos, as CIN is significantly lower in in vivo-derived cleavage-stage embryos compared to in vitro-cultured embryos.

WHAT IS KNOWN ALREADY

CIN is common during in vitro embryogenesis and is associated with early embryonic loss in humans, but the stability of in vivo-conceived cleavage-stage embryos remains largely unknown.

STUDY DESIGN, SIZE, DURATION

Because human in vivo preimplantation embryos are not accessible, bovine (Bos taurus) embryos were used to study CIN in vivo. Five young, healthy, cycling Holstein Friesian heifers were used to analyze single blastomeres of in vivo embryos, in vitro embryos produced by ovum pick up with ovarian stimulation (OPU-IVF), and in vitro embryos produced from in vitro matured oocytes retrieved without ovarian stimulation (IVM-IVF).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Single blastomeres were isolated from embryos, whole-genome amplified and hybridized on Illumina BovineHD BeadChip arrays together with the bulk DNA from the donor cows (mothers) and the bull (father). DNA was also obtained from the parents of the bull and from the parents of the cows (paternal and maternal grandparents, respectively). Subsequently, genome-wide haplotyping and copy-number profiling was applied to investigate the genomic architecture of 171 single bovine blastomeres of 16 in vivo, 13 OPU-IVF and 13 IVM-IVF embryos.

MAIN RESULTS AND THE ROLE OF CHANCE

The genomic stability of single blastomeres in both of the in vitro-cultured embryo cohorts was severely compromised (P < 0.0001), and the frequency of whole chromosome or segmental aberrations was higher in embryos produced in vitro than in embryos derived in vivo. Only 18.8% of in vivo-derived embryos contained at least one blastomere with chromosomal anomalies, compared to 69.2% of OPU-IVF embryos (P < 0.01) and 84.6% of IVM-IVF embryos (P < 0.001).

LARGE SCALE DATA

Genotyping data obtained in this study has been submitted to NCBI Gene Expression Omnibus (GEO; accession number GSE95358).

LIMITATIONS REASONS FOR CAUTION

There were two main limitations of the study. First, animal models may not always reflect the nature of human embryogenesis, although the use of an animal model to investigate CIN was unavoidable in our study. Second, a limited number of embryos were obtained, therefore more studies are warranted to corroborate the findings.

WIDER IMPLICATIONS OF THE FINDINGS

Although CIN is also present in in vivo-developed embryos, in vitro procedures exacerbate chromosomal abnormalities during early embryo development. Hence, the present study highlights that IVF treatment compromises embryo viability and should be applied with care. Additionally, our results encourage to refine and improve in vitro culture conditions and assisted reproduction technologies.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the Agency for Innovation by Science and Technology (IWT) (TBM-090878 to J.R.V. and T.V.), the Research Foundation Flanders (FWO; G.A093.11 N to T.V. and J.R.V. and G.0392.14 N to A.V.S. and J.R.V.), the European Union's FP7 Marie Curie Industry-Academia Partnerships and Pathways (IAPP, SARM, EU324509 to J.R.V., T.V., O.T, A.D., A.S. and A.K.) and Horizon 2020 innovation programme (WIDENLIFE, 692065 to J.R.V., O.T., T.V., A.K. and A.S.). M.Z.E., J.R.V. and T.V. are co-inventors on a patent application ZL913096-PCT/EP2014/068315-WO/2015/028576 ('Haplotyping and copy-number typing using polymorphic variant allelic frequencies'), licensed to Cartagenia (Agilent Technologies).

Case report: Partial hydatidiform mole following the transfer of single frozen–thawed embryo subsequent to ICSI

Hydatiform mole is a gestational trophoblastic disease characterized by the dominance of dispermic fertilization. Micromanipulation techniques in assisted reproduction technologies have enabled direct evaluation of the zygotes and the formation of pronuclei in the zygote. Intracytoplasmic sperm injection (ICSI) of oocytes ensures that only a single spermatozoon enters the ooplasma. This study reports a case of partial hydatiform mole following the transfer of day 3 frozen-thawed embryo. ICSI was used as the assisted fertilization method because there was male factor infertility due to severe oligoasthenoteratozoospermia. Possible predisposing factors for partial hydatidiform mole after ICSI are also discussed.

Molecular genetic analysis of complete hydatidiform moles

Complete hydatidiform moles (CHM) are the most common form of gestational trophoblastic disease and a frequent antecedent to choriocarcinoma. Cytogenetic investigations into the origin of these tumors have shown that they can arise by virtue of unusual fertilization events. In this study we used molecular genetic "fingerprinting" methods to examine the genome of 22 consecutive CHM in order to determine their derivation. We found that 60% contained alleles consistent with a completely homozygous androgenic origin. The remaining 40% were heterozygous for marker alleles; half of these were completely androgenic in origin. The other half of these heterozygous CHM contained alleles from the maternal genome, indicating a biparental contribution. These findings suggest that the pathogenesis of CHM is more heterogenous than previously suspected, and can arise from biparental fertilization events. In addition, we found that mutations occur frequently at many loci in these tumors, which may reflect a generalized genetic instability perhaps related to subsequent malignant change. Thus, molecular genetic analysis of CHM provides new insights into the genesis of CHM and will be a powerful method for understanding their clinical biology.