A Time-Lapse Sibling Oocyte Study: Does Embryo Culture Medium Have an Impact on Morphokinetic Parameters?

To evaluate the effects of different culture media on embryonic development and morphokinetic parameters in the same culture condition by sibling oocyte study. Retrospective analysis: randomized, sibling oocyte study in a private assisted reproductive technology clinic. This study was approved by the Ladies Clinic Kyono Ethics Committee. The subjects were 450 fertilized zygotes from 66 cycles from which at least six oocytes were retrieved at our clinic, from Oct. 2017 to Feb. 2018. Following IVF/ICSI, normally fertilized zygotes were divided into two groups and cultured in an EmbryoSlide+TM with two kinds of culture media, global®total® LP (GL) and SAGE 1-StepTM (SA). Both media contain 5mg/ml human serum albumin. Embryos were monitored by EmbryoScope+TM with 6% CO2 and 5% O2. We analyzed embryonic development and the appearance of multinucleation (MN) between the two media. Furthermore, in the 155 blastocysts, morphological events (cell division and interval of cell cleavage) evaluations were performed by tPNf (syngamy), t2 (time to 2 cell), t3, t4, t5, t6, t7, t8, tM (fully compacted morula), tSB (start of blastulation), tB (time of blastulation), cc2 (t3-t2) and s2 (t4-t3). We also compared the appearance of multinucleation (MN), direct cleavage (DC) and cell fusion (CF: a reduction in the number of cells of an embryo during its development). Fisher's exact test and Mann-Whitney U tests were used for statistical analysis. P<0.05 was considered statistically significant. In embryonic development - good-quality day-3 embryo rate , blastocyst formation rate and good-quality blastocyst rate - there were no significant differences between the two media. GL showed a significantly higher appearance of MN at 2 or 3-cell stage than SA in both insemination methods (ICSI: GL, 31.1% (38/122) vs SA, 19.2% (19/99); c-IVF: GL, 25.0% (17/68) vs SA, 8.6% (5/58); P<0.05). In the morphokinetic analysis, there were no differences in time points of cell division (tPNf to tB) or appearance of DC and CF. However, there were significant differences in interval of second embryo cell cycle (cc2) (cc2: GL, 11.3±1.7h vs. SA, 10.0±2.8h; P=0.0019) derived from ICSI embryos. There was no difference in embryonic development between the two culture media, but a significant difference was found in the presence of MN at two-cell stage. Although there was no difference in the presence of MN in the embryos that reached the blastocyst stage, since a significant difference was observed in the interval of cell cleavage (cc 2), it was suggested that culture medium may affect the time of DNA replication of early cleavage stage embryos.