Morphological study of human embryos co-culturing in a time-lapse incubator

Abstract

In the present study, a co-culturing method is proposed, which consists in culturing two embryos in the same plate. The aim of this study was to analyze the impact of embryo coculturing on the development and quality of human embryos, with the final goal to perform the Intra- cytoplasmic sperm injection procedure. An improvement of the embryo development and implantation rates was expected to achieve in those co-cultured embryos. In order to analyze the co-culturing impact in the embryo features, morphological factors are evaluated in several embryo developmental stages. Monitoring these changing morphological events is currently feasible thanks to advanced strategies such as the timelapse incubator. After the ovarian treatment, which included superovulation, ovarian puncture and removal of cumulus-corona, and the sperm selection, the injection procedure was carried out in a total of 297 oocytes from 21 patients. Then, morphological changes of the embryos were supervised and analyzed before proceeding to cryopreserve them. In this way, the transference of the best quality embryo could be performed and so, enhance the gestation and birth rates. During the embryo development, a zygot scoring was applied to select those fertilized eggs with 2 pronuclei (2PN) and to discard the non-fertilized and degenerated oocytes, as well as those with abnormal fertilization. The fertilization rate of co-cultured embryos was higher than non-co-cultured embryos but non-statistically significant (85.05% and 78.64% respectively, P>0.05). No significant differences were shown neither at day 3 morphological evaluation nor embryo compaction at day 4 (P>0.05). Significantly (P<0.05) higher proportions of blastocysts at day 5 were obtained in the co-cultured embryos group, whereas at day 6 and day 7 blastocysts rates weren’t statistically different (P>0.05). For implantation rate, the hCG blood test and the analysis of the evolutive implantation weren’t significantly different (P>0.05), however the clinical implantation had significant differences (P<0.05) among cocultured and non-co- cultured embryos group. It may be concluded that the co-culturing influenced beneficially the blastocyst percentages at day 5, as well as an improvement in the implantation rate. Hence, this new method might become a potential tool to improve the overall embryo development and so, benefit further assisted reproductive techniques