Abstract
A retrospective case control study was undertaken at the molecular biology department of a private center for reproductive medicine in order to determine whether any correlation exists between mitochondrial DNA (mtDNA) content of cleavage-stage preimplantation embryos and their developmental potential. A total of 69 couples underwent IVF treatment (averaged women age: 36.5, SD 4.9) and produced a total of 314 embryos. A single blastomere was biopsied from each embryo at the cleavage stage (day-3 post-fertilization) subjected to low-pass next generation sequencing (NGS), for the purpose of detecting aneuploidy. For each sample, the number of mtDNA reads obtained after analysis using NGS was divided by the number of reads attributable to the nuclear genome. The mtDNA copy number amount was found to be higher in aneuploid embryos than in those that were euploid (mean mtDNA ratio ± SD: 6.3 ± 7.5 versus 7.1 ± 5.8, p < 0.004; U Mann–Whitney test), whereas no statistically significant differences in mtDNA content were seen in relation to embryo morphology (6.6 ± 4.8 vs. 8.5 ± 13.6, p 0.09), sex (6.6 ± 4.1 vs. 6.2 ± 6.8, p 0.16), maternal age (6.9 ± 7.8 vs. 6.7 ± 4.5, p 0.14) or its ability to implant (7.4 ± 6.6 vs. 5.1 ± 4.6, p 0.18). The mtDNA content cannot serve as a useful biomarker at this point in development. However, further studies investigating both quantitative and qualitative aspects of mtDNA are still required to fully evaluate the relationship between mitochondrial DNA and human reproduction.
Highlights
As most of published studies concerning mitochondrial DNA (mtDNA) copy number in human embryos were conducted using blastocysts from frozen in vitro fertilization (IVF) cycles [7,8,9,10,11,12,13,36], we decided to evaluate the end point parameters by assessing blastomeres biopsied at the cleavage stage that were transferred on day 5 of the same cycle
We have used an approach that allowed for a fresh embryo transfer as the current literature demonstrates mitochondria disfunction and oxidative stress can be caused by cryopreservation [37]
This study confirms that next generation sequencing (NGS) can be used for the simultaneous detection of aneuploidy and measurement of mtDNA content in cells biopsied from human preimplantation embryos
Summary
The success of assisted reproductive treatment (ART) is affected by endometrial receptivity, embryo quality and embryo transfer efficiency [3]. The importance of identification and development of strategies for increasing implantation and pregnancy rates has led to the development of multiple protocols for the analysis of the embryos generated using IVF, with the aim of improving treatment success rates by revealing the embryo(s) most likely to yield a viable pregnancy. Such embryos can be given priority for transfer to the uterus. There is a significant percentage of morphologically and chromosomally normal embryos failing to implant which suggests the existence of other factors affecting embryo viability [4,5]
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