P–233 The spatial arrangement of blastomeres and time of cavitation forming as predictors of blastocyst quality

Study question

Does the spatial arrangement of blastomeres and the start of blastulation affect blastocyst quality?

Summary answer

Better blastocyst quality is associated with the spatial arrangement of the embryo and the shorter time frame of blastulation (cavitation).

What is known already

The ability to select the human embryo with the highest implantation potential remains one of the greatest challenges in the management of In Vitro Fertilization patients. Several publications have proposed that additional morphological evaluations of blastomere arrangement and the dynamics of late-stage embryonic divisions might be a useful non-invasive way for embryo selection. In the last decade, the introduction of time-lapse technology enables continuous monitoring of embryo development, which leads to better outcomes than a selection based on the traditional morphology assessment.

Study design, size, duration

The spatial arrangement was defined as tetrahedrally if the cleavage planes were perpendicularly orientated, while embryos with rather parallelly orientated cleavage axes were considered as non-tetrahedral embryos. The injection time of ICSI was designated as “time zero” (t0), and EmbryoViewer software was used to calculate the time duration between injection and start of blastulation (cavitation). Obtained results were later correlated with the embryo’s capability to form a blastocyst as well as with blastocyst quality.

Participants/materials, setting, methods

A total of 195 oocytes from 40 patients undergoing the antagonist cycle for ICSI treatment were evaluated. All blastocysts were cultured in Embryoscope™ according to the manufacturer’s specifications (Vitrolife, Sweden). The Gardner and Schoolcraft scoring system was used to describe blastocyst quality. Statistical analyses were performed using IBM SPSS version 24. Data were reported as median and range. Differences between groups were tested using the Mann-Whitney U test. Statistical significance was defined as p < 0.05.

Main results and the role of chance

Obtained data showed that 83.6% (61/73) of embryos with tetrahedral arrangement formed blastocysts compared to 42.4% (50/116) of embryos with the non-tetrahedral arrangement (p < 0,001). Moreover, tetrahedral embryos more frequently formed good quality blastocyst compare to the non-tetrahedral [59% (36/61) vs 18 (9/50)% respectively; p < 0,001]. In addition, we found that good quality blastocyst had a significantly shorter time frame between injection and blastulation start, compared with blastocysts which did not reach good quality [95.00h (84–118) vs 102h (77–121) respectively; p = 0,006].

Limitations, reasons for caution

The limitation of the present study was that due to the double-embryo transfer correlation between those morphokinetic parameters and pregnancy rate can not be calculated. Further research should link these morphokinetic parameters with pregnancy rate and live birth rate as well.

Wider implications of the findings: The potential of our findings is considerable, especially for countries with strict Embryo Law Regulation. Obtained results might be highly useful for selecting embryos with high implantation potential. In addition, the present work illustrates the possibility of additional information that can potentially be incorporated into an embryo classification model.

Trial registration number

Not applicable

P–140 Zygote morphokinetics as a predictor of blastocyst quality

Study question

Does the total cytoplasmic volume (TCV) of the zygote and time of pronuclei disappearance (tPNf) affect blastocyst development potential and blastocyst quality?

Summary answer

The total cytoplasmic volume of zygote and the time of pronuclei disappearance strongly affect blastocyst development as well as blastocyst quality.

What is known already

Extended embryo culture with blastocyst transfer is considered a useful method for selecting embryos with a high implantation potential. One of the main concerns in the German Embryo Protection Act is that the choice of embryos that have a high potential for successful implantation must be made at the pronucleus stage. The introduction of time-lapse technology enabled comprehensive information regarding the morphology and kinetics of the embryo. Although for the past years, strong correlations between embryo morphokinetics and positive outcomes have been demonstrated, some disagreement concerning the wide application of these parameters into an early-stage embryo selection is still present.

Study design, size, duration

The injection time of ICSI was designated as “time zero”, and computer software was used to calculate the time frame between the injection and the moment of pronuclei disappearance (tPNf). The total cytoplasmic volume was calculated 16–18 h after injection based on manually drawn diameters of the zygotes, by the computer. Obtained measurements were later associated with the blastocyst formation potential as well as with blastocyst quality.

Participants/materials, setting, methods

A total of 187 oocytes from 34 patients undergoing the antagonist cycle for ICSI treatment were evaluated. All blastocysts were cultured in Embryoscope™ according to the manufacturer’s specifications (Vitrolife, Sweden). The Gardner and Schoolcraft scoring system was used to describe blastocyst quality. Statistical analyses were performed using IBM SPSS version 24. Data were reported as median and range. Differences between groups were tested using the Mann-Whitney U test. Statistical significance was defined as p < 0.05.

Main results and the role of chance

Obtained data showed that the total cytoplasmic volume values were significantly higher in zygotes that reached the blastocyst stage compared with those that did not [708376,268µm³ (560564,412µm³ - 838602,605µm³) vs 674349,917 (415749,353- 823640,638) respectively; p < 0.0001]. Furthermore, this parameter as well significantly affect blastocyst quality where zygotes which formed better blastocyst quality had smaller cytoplasmic volume [685568,079 µm³ (560564,412- 790112,397µm³) vs 745514,662 µm³ (616581,339- 838602,605) respectively; p < 0.0001]. Time of pronuclei disappearance (tPNf) was significantly different (p < 0.0001) in successfully formed blastocysts [22.00h (17–29 h)] versus arrested or non-blastulating embryos [23.00h (17–56 h)]. Zygotes who had a shorter time frame between injection and pronuclei disappearance showed better blastocyst quality values compared with those who had longer time frame [21.00h (17–28h) vs 23.00h (18–29h) respectively; p < 0.01].

Limitations, reasons for caution

The limitation of the presented study was that due to the double-embryo transfer correlation between morphokinetic parameters and pregnancy rate was not possible to be calculated. Further research should link these morphokinetic parameters with pregnancy rate and live birth rate as well.

Wider implications of the findings: The potential of the present findings is considerable, especially for countries with strict Embryo Law Regulation. Obtained results might be highly useful for selecting embryos with high implantation potential. In addition, the present work illustrates the possibility of additional information that can potentially be incorporated into an embryo classification model.

Trial registration number

Not applicable

Hyaluronic acid substantially increases the retention of motility in cryopreserved/thawed human spermatozoa

We have demonstrated previously that hyaluronic acid (HA) improves the velocity and the retention of motility in freshly ejaculated human spermatozoa. In the present work, we examined the effect of HA on cryopreserved/ thawed spermatozoa in four paradigms: (i) effect of HA on sperm motility and velocity in semen; (ii) stabilizing effect of HA after 4 h of incubation when the decline of sperm motility is already detectable; (iii) the duration of improved motility after the separation of spermatozoa from HA by Percoll gradient centrifugation; and (iv) motility of sperm cryopreserved in the presence of HA. HA improved the retention of sperm motility in thawed spermatozoa. Indeed, the motility values after 30 h were approximately 100% higher in the HA compared with the control samples. This effect of HA was also evident in the stabilization of spermatozoa with already declining motility. After removal of the HA from the incubation medium, significantly increased motility in the HA-exposed spermatozoa was still detectable for at least 4 h. Cryopreservation of spermatozoa in the presence of HA did not improve the recovery of motility. The data indicate that HA improves the retention of motility of cryopreserved/thawed spermatozoa, even after the removal of HA from the incubation medium. The utilization of HA will probably prove beneficial in assisted reproduction: in intrauterine insemination and in in-vitro fertilization (IVF), the extended sperm motility and velocity will enhance the fertilizing efficiency; in intracytoplasmic sperm injection (ICSI), the improved motility will facilitate the identification of viable spermatozoa. Because HA is a physiological component of the cumulus and of the female and male reproductive tracts, administration of HA should not cause ethical concerns.

Biochemical markers of early and late spermatogenesis: relationship between the lactate dehydrogenase-X and creatine kinase-M isoform concentrations in human spermatozoa

As part of our research program on biochemical markers of sperm maturity, we have studied sperm creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations and the isoform ratios of the CK-M [% CK-M/(CK-M + CK-B)] and LDH-X [% LDH-X/(LDH-X + LDH-a)] in 50 oligospermic and 95 normospermic men [corrected]. Because the synthesis of LDH-X is initiated in early spermatogenesis, and that of CK-M commences in late spermiogenesis simultaneously with cytoplasmic extrusion, we proposed two working hypotheses:(1) LDH and CK concentrations reflect the retained cytoplasm in sperm, thus the activities of both enzymes will be related and will be higher in oligospermic specimens, which have a higher incidence of immature spermatozoa; and (2) because in normally developed sperm both LDH-X and CK-M are present, there will be a correlation between LDH-X and CK-M ratios in the mature sperm populations. However, among men with immature sperm samples with late spermiogenetic defect and diminished CK-M ratios, there will be two groups: one which completed spermatogenesis prior to spermiogenetic failure (normal LDH-X and diminished CK-M ratios), and another group with defects in both spermatogenesis and spermiogenesis (low LDH-X and diminished CK-M ratios). Because of this heterogeneity, LDH-X ratios will be a poor predictor of sperm maturity. The data support the hypotheses: (1) LDH and CK concentrations were higher in oligospermic vs. normospermic men (P < 0.001). (2) The LDH and CK concentrations were related (r = 0.65, P < 0.001, N = 145), and there were inverse correlations between CK, LDH, LDH-X, or CK-M ratios vs. sperm concentrations (P < 0.001 in all four). (3) The CK-M and LDH-X ratios were different between the oligospermic and normospermic groups (P < 0.001), although the means of the LDH-X ratios were narrower (LDH-X:1:1.3; CK-M:1:1.9). (4) Dividing the 145 samples by the cut-off value of mean minus 1 SD of the CK-M and LDH-X ratios (11% and 32%, respectively) demonstrated that the CK-M ratios discriminated better than LDH-X ratios between the samples with mature and immature sperm. These data on the biochemical markers of early and late spermatogenesis support the studies in which CK better reflected sperm quality than LDH or LDH-X (Orlando et al., 1994: Int J Androl 17:13-18) and the > 10% sperm CK-M ratio predicted with a rate of 30.4% per cycle in the occurrence of pregnancies in a blinded study of 84 IVF couples (Huszar et al., 1992: Fertil Steril 57:882-888).

Sperm function and choice of preparation media: comparison of Percoll and Accudenz discontinuous density gradients

We compared the sperm populations prepared by Accudenz (35-65%) and Percoll (40-80%) density gradients in 21 normospermic specimens (concentration, 53.6 +/- 3.8 x 10(6) sperm/ml; motility, 44.5 +/- 3.5%). Accudenz facilitated a higher recovery of sperm and motile sperm (68.4 +/- 6.6% vs. 49.3 +/- 4.9%, P < 0.001, and 87.8 +/- 4.1% vs. 77.8 +/- 3.7%, P < 0.01, respectively). Sperm motility was lower in the Accudenz compared to the Percoll pellets; thus the values of total motile sperm recovered were not different (17.1 +/- 2.4 vs. 15 + /- 1 2.2 x 10(6) sperm/ml). The long term retention of sperm motility was substantially improved in Accudenz (at 24 hours, 34.9 +/- 2.8% vs. 26.3 +/- 1.5%; 60% vs. 40% of the initial motility, P < 0.001), and the Accudenz vs. Percoll samples also exhibited a higher retention of total motile sperm (at 24 hours, 9.8 +/-.2 vs. 6.1 = 0.5 x 10(6) motile sperm/ml, P < 0.05). The sperm motility index, a multiple of velocity and motility in the sample that reflects the efficiency of the sperm population in sperm-oocyte interaction, was 75% higher in the Accudenz samples at 24 hours (3.6 +/- 0.4 vs. 2.1 +/- 0.2, mu m/second, P < 0.01). Sperm cellular maturity by the creatine phosphokinase (CK) activity and CK-M to CK-B isoform ratio parameters (in the original samples 0.14 +/- 0.02 lU CK/100 x 10(6) sperm and 57.9 +/- 3.7%, respectively) were improved in both the Accudenz and Percoll pellets (P < 0.001), with no difference between the two sperm fractions. Sperm activation status monitored by chlortetracycline fluorescence indicated that after 4 hours of incubation the incidence of fully acrosome-reacted spermatozoa in the Accudenz versus Percoll pellets was 6.2 +/- 0.3% versus 13.1 +/- 1.0% (P < 0.001), a 100% increase in Percoll. We can conclude that Accudenz yields a higher concentration of motile spermatozoa, with improved retention of motility, velocity, and acrosomal integrity and without an increase of sperm with diminished cellular maturity. Thus, in sperm preparation for intrauterine insemination, in which the timing of ovulation and insemination frequently do not correspond, Accudenz-prepared sperm, with a better retention of motility/velocity and acrosomal integrity and with a consequential higher resistance to activation by the female reproductive tract, are expected to be more effective.