P-267 A continuous culture medium with a lower concentration of lactate has a pronounced effect on the percentage of usable blastocysts on day 5

Study question

Does Continuous Single Culture Medium NX, an embryo culture medium containing 1mM lactate, support increased blastocyst development over high lactate Vitrolife G1/G2 Series sequential culture?

Summary answer

There is a statistically significant increase in day 5 usable blastocysts in low lactate culture medium compared to the one with high lactate medium.

What is known already

Studies have shown that day 5 is the most desirable day to obtain blastocysts that are of an expansion, grade and quality to be utilized for transfer and/or vitrification procedures as those result in the highest success of clinical pregnancy,as compared to day 6/ 7 blastocysts, that do not meet criteria. Moreover, recent studies have indicated that there is an increase in chromosomal correctness of embryos cultured in a 1mM lactate environment as opposed to the higher 6-10mM lactate concentrations that have historically been believed necessary for successful blastocyst culture and resulting pregnancy.

Study design, size, duration

A prospective split sibling oocytes study was performed on 50 ICSI and IMSI cycles from October 2020 through April 2021. Oocytes were divided into the low lactate medium and high lactate gradient medium immediately following ICSI/IMSI and thereafter cultured in those medium until the final day of blastocyst culture. All patient ages were included in the sample population.

Participants/materials, setting, methods

This study was carried out in a private clinic. All patient stimulation protocol information and diagnosis’ were recorded; however, there was no restriction on participation. The endpoint was to analyse the resulting usable blastocyst rates on day 5 and day 6 in both arms of the study, using a denominator of normal 2PN fertilization. If a blastocyst was transferred or cryopreserved on day 5 or day 6, it was determined to be usable.

Main results and the role of chance

The resulting data was stratified not only by day 5 and day 6 usable blastocyst rates but also by patient age. It illustrates a statistically significant improvement in day 5 usable blastocysts for patients <35 in CSCM-NXC vs G1/G2 at 56% and 42%, respectively, a 14% increase (p < .05). The overall day 5 usable blastocyst rate was also statistically significant in CSCM-NXC (47%) as compared to G1/G2 (36%), (p < .05) with all ages considered. Additionally, on day 5, there was a higher percentage of usable blastocysts demonstrated in low lactate vs high in patients aged 35-37 (65% vs 42%, respectively) and 41-42 (41% vs 15%). Statistical significance was reversed in patients <35 on day 6, with G1/G2 having 24% usable blasts and CSCM-NXC 10% (p < .05). Interestingly, though not significant, G1/G2 had an increase in usable blastocyst percentage on day 5 in patients >42 (20% vs 11%), but overall, CSCM-NXC saw an increase in that same age group by 16%.

Limitations, reasons for caution

Though statistical significance was found in this study, a greater number will help to bolster the statistical power of the observations. Additionally, more studies are needed in order to ascertain if low lactate has an effect on the development prior to ICSI and resulting culture.

Wider implications of the findings

The mechanism of action that leads to the successful embryo development in low lactate embryo culture medium is vastly unknown, so further studies are required in order to understand the complexities and the impact of the observations provided.

Trial registration number

not applicable.

P–091 Magnetic Activated Cell Sorting (MACS) improves euploid blastocysts rate in pre-implantation genetic testing cycles with high levels of sperm DNA fragmentation and advanced paternal age

Study question

Can MACS increase euploid blastocyst rate in Pre-implantation Genetic Testing (PGT) cycles for AMA-APA (Advanced Maternal-Paternal Age) in patients with high sperm DNA fragmentation (SDF)?

Summary answer

A slight increase in euploid blastocyst rate was found using MACS in infertile patients with high SDF undergoing PGT cycles compared to the control group.

What is known already

Many authors have shown a close correlation between the presence of apoptotic markers on spermatozoa and the failure of assisted reproduction treatments. In normal physiological conditions, apoptotic spermatozoa with phosphatidylserine (PS) residues externalized on the plasma membrane, are eliminated along female genital tract, preventing oocyte fertilization. MACS eliminates apoptotic sperm whit PS residues using superparamagnetic microbeads conjugated with annexin V. This technique reduces the proportion of sperm with high rates of SDF and can be used to maximize ART procedures results. MACS application improves sperm quality, fertilization, cleavage and pregnancy rates reducing miscarriage rate.

Study design, size, duration

From June to November 2020, 10 couples in which MACS was applied to select non-apoptotic spermatozoa, were randomly enrolled in our study (MACS group) and 8 couples without MACS were considered as controls (No-MACS Group). All couples in both groups underwent a PGT cycle and had high sperm DNA Fragmentation (> 20%). A higher rate of euploid and diploid-euploid mosaic blastocysts were obtained in the MACS group compared to the control group.

Participants/materials, setting, methods

Patients with severe oligoastenoteratozoospermia were excluded. MACS protocol was performed as follows: semen sample was analyzed (WHO 2010) and washed with buffered medium; pellet was removed and a swim-up was performed. Retrieved spermatozoa were washed with a binding buffer (Miltenyi Biotec), centrifuged (400 g x 4 minutes) and supernatant discarded. Pellet was covered with Annexin-V and re-suspended. After 15 minutes incubation at room temperature, the sample was eluted through the column and collected for ICSI.

Main results and the role of chance

In MACS group, female and male mean age ± SD were 41.6 ± 2.1 and 43.5 ± 7.3, respectively. Female and male mean age ± SD were 41.7 ± 2.8 and 44.6 ± 8.1 in the No-MACS group, respectively. In MACS and No-MACS groups, injected oocytes were 44 and 35, fertilized oocytes were 32 (72.3%) and 27 (77.1%) (NS), blastocyst formation rates were 71.8% (23/32) and 48.1% (13/27) (NS), respectively. In No-MACS group, only 1 euploid and 1 diploid-euploid mosaic blastocysts were obtained (1/13 = 8%) (NS). In MACS group, 4 euploid blastocysts were formed (4/23 = 17.4%) whereas mosaic diploid-euploid blastocysts were 3/23 (13.0%) (NS). Aneuploid blastocysts were 16/23 (69.6%) in MACS group and 11/13 (84.6%) in No-MACS group (NS).

Limitations, reasons for caution

AMA and APA of couples enrolled should be considered as a limit of the study. A larger number of patients and biopsied blastocysts are needed to analyze clinical results and perform a robust statistical analysis establishing if MACS is useful to improve transferable blastocyst rate in patients with high SDF.

Wider implications of the findings: MACS is useful to select non apoptotic sperms; although fertilization, cleavage and blastocyst rates are not improved, aneuploid blastocysts rate slightly decreases using MACS. It I possible that, selecting spermatozoa free from PS residues, MACS allows to choose spermatozoa with a better DNA packaging, thus affecting the embryo ploidy.

Trial registration number

non applicable