Mitochondrial DNA content decreases during in vitro human embryo development: insights into mitochondrial DNA variation in preimplantation embryos donated for research

OBJECTIVE

To assess the mitochondrial DNA (mtDNA) load and variation in human oocytes and during preimplantation embryo development using specimens donated for research.

DESIGN

Prospective cohort study.

SETTING

Not applicable.

PATIENTS

A total of 50 in vitro fertilization patients and 11 oocyte donors whose specimens were obtained between July 2017 and July 2018.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

All specimens were separately collected. Quantitative polymerase chain reaction was performed with SurePlex DNA Amplification System (Illumina). Primers for the adenosine triphosphate 8 mitochondrial gene and the β-actin were used. Data were statistically analyzed by analysis of variance with the Scheffé multiple pairwise comparison for categorical variables and by linear regression for numerical variables.

RESULTS

Human metaphase II (MII) oocytes had significantly more total mtDNA copy number than day 3 embryos, and day 3 embryos had more total and per-cell mtDNA copy number than aneuploid blastocysts. There was a significant decrease in mtDNA content associated with failed-fertilized oocytes compared to noninseminated metaphase II oocytes.

CONCLUSIONS

During preimplantation development, before implantation, human embryos undergo a significant decrease in total mtDNA content and no increase in mtDNA content at the blastocyst stage. Oocytes need to carry a correct threshold of mitochondrial load in the oocyte in order to successfully fertilize. An active degradation of mtDNA before implantation occurs after fertilization takes place. These findings could be used to improve knowledge about the best embryo culture conditions and would serve as a basis for further studies addressing again the use of mtDNA content as an embryo viability marker.

Mitochondria as a tool for oocyte rejuvenation

Ovarian aging leads to a decrease in the quantity and quality of oocytes. Aged oocytes have significantly reduced amounts of mitochondria, the energy factories of cells, leading to lower fertilization rates and poor embryonic development. Various techniques have tried to use heterologous or autologous sources of mitochondria to reestablish oocyte health by providing more energy. However, heterologous sources are no longer used owing to the known risk of heteroplasmy. Although autologous methods have recently been tested in humans, they have not shown a clear improvement in embryo quality. In this review, we describe the techniques that have been tested in recent years to provide a state of the art on oocyte rejuvenation through extra injection of mitochondria.

Autologous mitochondrial transfer as a complementary technique to intracytoplasmic sperm injection to improve embryo quality in patients undergoing in vitro fertilization-a randomized pilot study

OBJECTIVE

To study if autologous mitochondrial transfer (AUGMENT) improves outcome in patients with previously failed in vitro fertilization (IVF).

DESIGN

Randomized, controlled, triple-blind, experimental study.

SETTING

Private infertility center, Valencian Institute of Infertility (IVI-RMA), Valencia, Spain.

PATIENT(S)

Infertile women ≤42 years of age, body mass index <30 kg/m², antimüllerian hormone ≥4 pmol/L, >5 million/mL motile sperm, at least one previous IVF with at least five metaphase oocytes (MIIs) collected, and low embryo quality.

INTERVENTIONS(S)

An ovarian cortex biopsy was performed to isolate egg precursor cells to obtain their mitochondria. Sibling MIIs were randomly allocated to AUGMENT (experimental) or intracytoplasmic sperm injection (Control). In AUGMENT, mitochondrial suspension was injected along with the sperm. Viable blastocysts from both groups were biopsied for preimplantation genetic testing for aneuploidy.

MAIN OUTCOME MEASURE(S)

Pregnancy, embryo quality.

RESULT(S)

An interim analysis was conducted. The patients' mean age was 36.3 ± 3.6 years, and they had an average of 2.5 ± 1.5 previous IVF cycles. Two of the 59 enrolled patients spontaneously conceived (one miscarried). Fifty-seven patients had ovarian biopsies and underwent stimulation. Oocyte retrieval was performed in 56 patients (premature ovulation; n = 1). A total of 253 MIIs were inseminated in AUGMENT and 250 in Control; fertilization rates were 62.7 ± 30.0% and 68.7 ± 29.1%, respectively. Statistical differences were observed in day 5 blastocyst formation rates (23.3 ± 32.0% vs. 41.1 ± 36.9%). Neither the euploid rate per biopsied blastocyst (43.8 ± 41.7% vs. 63.8 ± 44.1%) nor the euploid rate per MII (9.8 ± 20.5% vs. 11.9 ± 16.1%) between AUGMENT and Control achieved statistical significance. Moreover, no differences were seen regarding mitochondrial DNA content and relevant morphokinetic variables. Thirty patients were able to undergo embryo transfer. Cumulative live birth rates per transferred embryo were 41.6% in AUGMENT and 41.2% in Control.

CONCLUSION(S)

AUGMENT does not seem to improve prognosis in this population. Therefore, the study has been discontinued.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02586298.

Conventional versus minimal ovarian stimulation: an intra-patient comparison of ovarian response in poor-responder women according to Bologna Criteria

RESEARCH QUESTION

Is minimal ovarian stimulation (MOS) as effective as conventional ovarian stimulation (COS) in ovarian response and embryo quality in the same 46 poor-responder patients according to the Bologna criteria?

DESIGN

An intra-patient comparison of patients undergoing both protocols. Ovaries were stimulated with either a gonadotrophin-releasing hormone antagonist protocol and a combination of recombinant FSH and highly purified human menotrophin (HP-HMG) daily (COS), or with the use of clomiphene citrate 50 mg daily and 150 IU of HP-HMG or recombinant FSH every other day from simulation day 4 (MOS).

RESULTS

After MOS, significantly more good-quality embryos (1.0 ± 1.2 versus 0.3 ± 0.6) (P = 0.002), oocytes (3.2 ± 1.9 versus 2.0 ± 1.8) (P = 0.002), and mature (metaphase II) oocytes (2.6 ± 1.7 versus 1.6 ± 1.7) (P = 0.001) were obtained. In COS cycles, a significantly higher total gonadotrophin dose was needed per good-quality embryo (+2194 IU; 95% CI 618 to 3170).

CONCLUSIONS

In poor responder patients, MOS is a good alternative when COS has failed, or even as a first-line treatment. It offered a significantly greater number of good-quality embryos as well as a higher number of oocytes, using significantly lower doses of gonadotrophins per oocyte and embryo obtained.

Reproductive outcomes after hysteroscopic metroplasty for women with dysmorphic uterus and recurrent implantation failure

BACKGROUND

The aim of this study was to assess the reproductive outcomes of women with recurrent implantation failure (RIF) after hysteroscopic metroplasty for dysmorphic uteri.

METHODS

This retrospective observational study included 190 women with a diagnosis of RIF. These patients were eligible for hysteroscopic metroplasty for dysmorphic uteri, including T-shaped uteri, between January 2008 and September 2015 at the Instituto Valenciano de Infertilidad (IVI) in Valencia, Spain.

RESULTS

The total clinical pregnancy rate, the live birth rate, and the abortion rate were 80.0% (152/190), 77.9% (147/190) and 8.9%, respectively. At 12 months, the clinical pregnancy rate was 76.3% (145/190) and at 6 months 50.5% (96/190). After the metroplasty, approximately 76% of all gravidities, were achieved during the first 12 months of follow-up. Within the first IVF cycle, pregnancy and live birth rates were 77.8% and 86.1%, respectively. The mean time to pregnancy was 6.5 months.

CONCLUSION

This study demonstrates that hysteroscopic metroplasty improves pregnancy and live birth rates for women with a history of recurrent implantation failure and dysmorphic uterus. However, conclusions must be taken carefully as this is an observational study. A prospective, randomized and controlled study is necessary to support these results.

Regimen of ovarian stimulation affects oocyte and therefore embryo quality

Without any doubt the regimen used to mature multiple capable oocytes for IVF impacts IVF outcomes. Studies have indicated that the inclusion of LH activity, adjuvant agents such as growth hormone (GH), and regimens providing for simultaneous action of both LH and FSH during final oocyte maturation may have beneficial effects on IVF outcomes. Because of the difficulty in improving IVF outcomes in poor responders, the studies on GH are of particular interest. As pointed out in this review, the apparent beneficial effects of GH on oocyte competence may also apply to older women or to normal responders with reduced embryo quality. A much more difficult question is whether and how much ovarian stimulation impacts on oocyte competence. Paradoxically it seems that there are not demonstrated differences between the stimulated and the natural unstimulated cycle, whereas studies in laboratory animals and IVF patients have shown deleterious effects of higher compared with lower doses of gonadotropins. Recent studies suggest that the use of high doses of gonadotropins as an independent factor correlates negatively with the probability of live birth, whereas a high ovarian response per se is associated with better cumulative pregnancy rates, owing to the availability of more euploid and good-quality embryos. Although adjunctive use of androgens has not been discussed here, it is briefly covered in the first review of this series.

Preimplantation genetic screening using fluorescence in situ hybridization in patients with repetitive implantation failure and advanced maternal age: two randomized trials

OBJECTIVE

To evaluate the usefulness of preimplantation genetic screening (PGS) using fluorescence in situ hybridization (FISH) for two different indications: repetitive implantation failure (RIF) and advanced maternal age (AMA).

DESIGN

Two prospective, randomized controlled trials with patients allocated in two arms: blastocyst transfer on day 5 (group A) or PGS with transfer on day 5 (group B).

SETTING

University-affiliated private clinics.

PATIENT(S)

The RIF study included women <40 years with three or more failed IVF cycles without other known causal factors (91 patients). The AMA study included intracytoplasmic sperm injection patients aged between 41 and 44 (183 patients).

INTERVENTION(S)

In the PGS group, single-cell day 3 biopsy was performed with aneuploidy screening for chromosomes 13, 15, 16, 17, 18, 21, 22, X, and Y. In both the blastocyst transfer group and the PGS group, ET was performed on day 5.

MAIN OUTCOME MEASURE(S)

Live-birth rate per patient and per started cycle.

RESULT(S)

A significant increase in live-birth rates per patient was found in the PGS group compared with the blastocyst group for the AMA study (30/93 patients [32.3%] vs. 14/90 patients [15.5%]; odds ratio, 2.585; confidence interval, [1.262-5.295]). In the RIF study no significant differences were observed (23/48 patients [47.9%] vs. 12/43 patients [27.9%]).

CONCLUSION(S)

PGS with FISH was shown to be beneficial for the AMA group.

Moderate ovarian stimulation does not increase the incidence of human embryo chromosomal abnormalities in in vitro fertilization cycles

CONTEXT

A high chromosomal abnormalities rate has been observed in human embryos derived from in vitro fertilization (IVF) treatments. The real incidence in natural cycles has been poorly studied, so whether this frequency may be induced by external factors, such as use of gonadotropins for ovarian stimulation, remains unknown.

DESIGN

We conducted a prospective cohort study in a University-affiliated private infertility clinic with a comparison between unstimulated and stimulated ovarian cycles in the same women. Preimplantation genetic screening by fluorescence in situ hybridization was performed in all viable d 3 embryos.

OBJECTIVE

The primary objective was to compare the incidence of embryo chromosomal abnormalities in an unstimulated cycle and in an ulterior moderate ovarian stimulated cycle. Secondary outcome measures were embryo quality, blastocyst rate of biopsied embryos, number of normal blastocysts per donor, type of chromosomal abnormalities, and clinical outcome.

RESULTS

One hundred eighty-five oocyte donors were initially recruited for the unstimulated cycle, and preimplantation genetic screening could be performed in 51 of them, showing 35.3% of embryo chromosomal abnormalities. Forty-six of them later completed a stimulated cycle. The sperm donor sample was the same for both cycles. The proportion of embryos displaying abnormalities in the unstimulated cycle was 34.8% (16 of 46), whereas it was 40.6% (123 of 303) in the stimulated cycle with risk difference=5.8 [95% confidence interval (CI)=-20.6-9.0], and relative risk=1.17 (95% CI=0.77-1.77) (P=0.45). When an intrasubject comparison was made, the abnormalities rate was 34.8% (95% CI=20.5-49.1) in the unstimulated cycle and 38.2% (95% CI=30.5-45.8) in the stimulated cycle [risk difference=3.4 (95% CI=-17.9-11.2); P=0.64]. No differences were observed for embryo quality and type of chromosomal abnormalities.

CONCLUSIONS

Moderate ovarian stimulation in young normo-ovulatory women does not significantly increase the embryo aneuploidies rate in in vitro fertilization-derived human embryos as compared with an unstimulated cycle. Whether these results can be extrapolated to infertile patients is still unknown.