Does blastomere removal alter the expression level of miR-Let7a and its target genes following mouse embryo biopsy?

Hypothesis: human trophectoderm biopsy downregulates the expression of the placental growth factor gene

Preeclampsia (PE) and intrauterine growth retardation (IUGR) are the results of defective placentation associated with the downregulation of different genes in the human trophoblast including the Placental Growth Factor (PGF). TrophEctoderm (TE) biopsy is increasingly performed for Pre-implantation Genetic Testing of Aneuploidies and it involves the traumatical removal of an unpredictable number of mural TE cells from the human blastocyst. We observed strikingly similar obstetrical and neonatal complications in pregnancies where the placenta bears PGF downmodulation or a TE biopsy has been done. In both groups, the risk of PE, IUGR, congenital cardiac ventricular septal defects, caesarean section, sex ratio in favour of males and preterm birth is significantly increased compared to controls. Given the high degree of correlation, the observation may not be a casual one. We postulate herein that the TE biopsy may induce persistent dysregulation of different genes in the placenta including PGF. The mechanism proposed is the disruption of tight junctions caused by the TE biopsy.

Modification of late human embryo development after blastomere removal on day 3 for preimplantation genetic testing

The purpose of our study was to use a time-lapse monitoring (TLM) system to determine if day 3 blastomere biopsy for preimplantation genetic testing (PGT) had an impact on subsequent morphokinetic parameters at the morula and blastocyst stages. In this retrospective monocentric study conducted between May 2013 and August 2017, we compared late morphokinetic parameters in embryos undergoing day 3 blastomere biopsy for PGT and in control non-biopsied embryos obtained in intracytoplasmic sperm injection (ICSI) cycles for male infertility. All embryos in both groups were cultured in a TLM system. The biopsy group was composed of 1691 embryos (386 PGT cycles). The control group was composed of 2578 embryos (786 ICSI cycles). Early morphokinetic parameters up to day 3 were similar in both groups. Concerning late morphokinetic parameters, the onset of compaction (tSC), fully-compacted morula stage (tM), onset of cavitation/early blastulation (tSB), and blastocyst stages (tB and tEB) appeared significantly earlier in the biopsy group than in the control group. We found that late morphokinetic events at the morula and the blastocyst stages occurred significantly earlier in biopsied embryos than in control non-biopsied-embryos. The mechanisms underlying these modifications of embryo development after biopsy should be investigated in order to determine precisely, and this phenomenon could be associated with embryo, fetal, and offspring development.Abbreviations: TLM: time-lapse monitoring; PGT: preimplantation genetic testing; ICSI: intracytoplasmic sperm injection; tSC: the onset of compaction; tM: fully-compacted morula stage; tSB: onset of cavitation/early blastulation; tB and tEB: blastocyst stages; OHSS: ovarian hyperstimulation syndrome.

Expression of miR-Let-7a, miR-15a, miR-16-1, and their target genes in fresh and vitrified embryos and its surrounding culture media for noninvasive embryo assessment

microRNAs (miRNAs) play a critical role in implantation and development of mouse embryos. In this study, we aim to evaluate the possibility of miRNAs as potential biomarkers in the blastocyst culture to assess embryo quality. We also intend to investigate whether improved clinical outcomes of vitrified embryos agree with altered miRNA expressions. Mouse embryos from in vitro fertilization were vitrified at the two-cell stage. After thawing, the embryos were individually cultured and developed to the blastocyst stage. We used quantitative real-time polymerase chain reaction to evaluate miRNA expression levels in both vitrified and fresh groups, and culture medium (CM). The fibronectin binding assay was performed to examine for blastocyst attachment. The findings showed reduced expressions of miR-16-1 (0.2 ± 0.06) and miR-Let-7a (0.65 ± 0.1) after vitrification compared to fresh embryos. We observed significant upregulation of the target genes Vav3 (4.33 ± 0.25), integrin β-3 (Itg β3; 4.73 ± 0.2), and Bcl2 (2.29 ± 0.16) in the vitrified embryos compared to the fresh groups. Evaluation of blastocyst CM showed upregulation of miR-Let-7a (15.68 ± 0.89), miR-16-1 (16.18 ± 0.75), and miR-15a (13.36 ± 0.73) in the vitrified group in comparison to the fresh blastocysts (P < .05). The expression levels of miR-16-1 (3.28 ± 0.63), miR-15a (5.91 ± 0.38), and miR-Let-7a (9.07 ± 0.6) in CM of the vitrified blastocysts conducted on fibronectin were significantly higher than the fresh group (P < .05).This study showed that vitrification of embryos changes implantation and proliferation biomarkers. In addition, upregulated miRNAs in CM could be potentially used for noninvasive early assessment of embryo quality.