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Time-dependent O2 consumption patterns determined optimal time ranges for selecting viable human embryos

OBJECTIVE To evaluate correlations between metabolic activity and implantation potential of transferred embryos in a study based on oxygen (O(2)) consumption (OC) measurements, because O(2) uptake is directly related to the capacity of an embryo to produce energy via adenosine triphosphate. DESIGN Retrospective cohort study. SETTING Infertility institute. PATIENT(S) Five hundred seventy-five injected oocytes in 56 first oocyte donation cycles with embryo transfer on day 3. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) We analyzed embryo destination viability and implantation depending on the embryo OC rate obtained from 47,741 measurements (up to 85 measurements per embryo, 2-3 measurements per hour). OC patterns were analyzed in relation to the time elapsed from sperm microinjection, to the final destination of the embryos (transferred, frozen, or discarded), to ongoing pregnancy, and by successful implantation. RESULT(S) OC was found to decrease during embryonic development. OC patterns from 52 hours onward showed the strongest correlation with implantation success. Regarding embryo destination, the same patterns were observed. CONCLUSION(S) OC from individual embryos revealed significant differences, mainly close to the time of transfer, when OC pattern was associated with successful implantation. Therefore, measuring the OC pattern of human embryos culture up to 72 hours could be used to select the embryo with best developmental potential.

The follicular hormonal profile in low-responder patients undergoing unstimulated cycles: is it hypoandrogenic?

STUDY QUESTION What is the final hormonal milieu of pre-ovulatory follicles of low-responder (LR) patients undergoing unstimulated cycles? SUMMARY ANSWER Neither androgen secretion nor LH was impaired in pre-ovulatory follicles of LR women. WHAT IS KNOWN ALREADY Therapies currently used to improve ovarian response in LR women have an impact on the final hormonal follicular milieu, and these changes are believed to be partially responsible for determining the success rate in these women. Surprisingly, as far as we know, there is no report of the final hormonal profile of LR women undergoing unstimulated cycles or evidence that follicular androgen secretion in LR women is impaired. STUDY DESIGN, SIZE AND DURATION A prospective case-control study including 94 women, 36 normal controls and 58 LR patients (19 Young ≤ 35 years LR and 39 Aged >35 years LR) from 2009 to 2011. PARTICIPANTS/MATERIALS, SETTING AND METHODS Fifty-eight LR women were divided into two groups: Young LR (age ≤ 35; n = 19) and Aged LR (ALR; age >35; n = 39). The control group (group C) comprised 36 egg donors undergoing an unstimulated cycle in our IVF unit. Serum and follicular fluid hormonal concentrations for estradiol (E₂), progesterone, testosterone and androstendione were measured. The spindle parameters of metaphase II oocytes generated from these groups were also analysed. MAIN RESULTS AND THE ROLE OF CHANCE Pre-ovulatory follicles from LR patients had similar androgenic and LH concentrations to those observed in the control group. However, higher intrafollicular concentrations of FSH and progesterone were observed in ALR. Moreover, no differences were found for the spindle evaluation of oocytes between groups by the Oosight technology. LIMITATIONS, REASONS FOR CAUTION The controls were younger and had a lower BMI than the LR women. The sample size available restricted statistical power. WIDER IMPLICATIONS OF THE FINDINGS This study suggests that the problem with LR women is not the final pre-ovulatory follicular androgen concentration since this is similar to normal responders, but in the ability to respond to controlled ovarian stimulation protocols. Therefore, efforts should be focused on long-interval androgen priming to potentially increase the recruitment of small antral follicles rather than increasing the intraovarian androgen levels within the current cycle. STUDY FUNDING/COMPETING INTEREST The present project has been supported by the R+D programme from the Generalitat Valenciana (Regional Valencian Government) IMPIVA MIDTF/2010/95. The authors have no conflict of interest to declare.

Reduced oxygen tension improves embryo quality but not clinical pregnancy rates: a randomized clinical study into ovum donation cycles.

OBJECTIVE To investigate the effect of low O2 tension during in vitro culture in terms of ongoing pregnancy rates in ovum donation cycles. DESIGN Randomized trial. SETTING Private university-affiliated IVF center, university-based hospital. PATIENT(S) A total of 1,125 cycles of ovum donation. INTERVENTION(S) Embryo culture in an atmosphere of 5.5% CO2, 6% O2, and 88.5% N2 versus a dual-gas system of 5.5% CO2 in air. MAIN OUTCOME MEASURE(S) Ongoing clinical pregnancy rates per intention-to-treat (ITT) patients. RESULT(S) The use of low O2 tension achieved a 41.3% ongoing pregnancy rate per ITT compared with a 40.8% rate obtained for 5% CO2 in air. The mean number of blastomeres and the percentage of top-quality embryos were significantly higher after lower O2 concentration during in vitro culture (7.1 ± 3.6 and 28.6% vs. 7.3 ± 8.4 and 32.1%, respectively). CONCLUSION(S) In the ovum donation cycles undergoing day-3 embryo transfers, the use of low O2 tension did not improve ongoing pregnancy rates per cycle and per transfer. However, it benefited embryo quality, demonstrating the potential negative impact of high O2 tension on the in vitro embryo development.

The Metabolomic Profile of Spent Culture Media from Day-3 Human Embryos Cultured under Low Oxygen Tension

Despite efforts made to improve the in vitro embryo culture conditions used during assisted reproduction procedures, human embryos must adapt to different in vitro oxygen concentrations and the new metabolic milieu provided by the diverse culture media used for such protocols. It has been shown that the embryo culture environment can affect not only cellular metabolism, but also gene expression in different species of mammalian embryos. Therefore we wanted to compare the metabolic footprint left by human cleavage-stage embryos under two types of oxygen atmospheric culture conditions (6% and 20% O2). The spent culture media from 39 transferred and implanted embryos from a total of 22 patients undergoing egg donation treatment was analyzed; 23 embryos came from 13 patients in the 6% oxygen concentration group, and 16 embryos from 9 patients were used in the 20% oxygen concentration group. The multivariate statistics we used in our analysis showed that human cleavage-stage embryos grown under both types of oxygen concentration left a similar metabolic fingerprint. We failed to observe any change in the net depletion or release of relevant analytes, such as glucose and especially fatty acids, by human cleavage-stage embryos under either type of culture condition. Therefore it seems that low oxygen tension during embryo culture does not alter the global metabolism of human cleavage-stage embryos.