13. THE CHROMOSOMAL SET ANALYSIS OF BLASTOCYSTS OBTAINED FROM MODIFIED DONOR OOCYTES BY THE PATIENT'S 1ST POLAR BODY TRANSFER

Abstract

Introduction Transfer of the patient's 1st polar body (PB) to donor oocyte cytoplasm has proven to be an effective method to help patients with low ovarian reserve and poor response. This technique allows doubling the number of oocytes suitable for fertilization, while maintaining the biological relationship of patient with the future child. The use of transfer in our practice has shown the ability of modified oocytes to form high morphological quality blastocysts and their euploidy have been evaluated in this study. Materials and Methods The study was performed in the Medical Center IGR from March 2017 to December 2018 and involved 330 cells: 168 oocytes (group A) obtained from 39 patients (mean age 40.7±5.3 years) and 162 oocytes (group B) that were received from 28 donors (mean age 28.2±2.4). Donor oocytes have been pre-enucleated and modified by the transfer of patients’ 1stPB with further fertilization. The procedure was made using Nikon Ti Eclipse (Japan) inverted microscope, Saturn 3 laser console (UK). Preimplantation genetic testing for aneuploidy (PGT-A) was performed using trophectoderm (TE) biopsy on the post-fertilization hours 120 or 144. Samples were diagnosed using Ion S5 by Thermo Fisher Scientific(USA). The samples’ ploidy was verified by the FISH. We evaluated the number of euploid and aneuploid blastocysts from maternal and modified oocytes by the 1st PB transfer. Statistical analysis was carried out using Shapiro-Wilk test for normality and Chi-square test. Results In the group A there were 50 blastocysts (29.8%) that formed from 168 original patients’ oocytes and 29 blastocysts (17.9%) developed from 162 modified oocytes (group B). 45 blastocysts from group A and 27 blastocysts from group B were biopsied for PGT-A. The number of euploid embryos was 11 (24.4%) and 6 (22.2%) in the group A and group B, respectively, without statistically significant difference (SSD). Among the aneuploidies, single (only one chromosome was involved in nondisjunction) and complex (several chromosomes involved in nondisjunction) chromosomal anomalies were encountered. In the group A 13 (38.2%) samples carried single chromosomal disorder and 21 (61.8%) samples had complex quantitative abnormalities, in the group B these numbers reached 9 (47.4%).and 10 (52.6%) samples, respectively. Among the aneuploid embryos 79 chromosome abnormalities were found in A group samples and 38 numerical aberration in B group samples.. The following types of chromosomal abnormalities were detected in groups: autosome trisomy (50/63.3% vs. 25/65.8% samples), autosome monosomy (23/29.1% vs.6/15.8% samples), numerical violation of sex chromosomes (6/7.6% vs. 4/10.5% samples), polyploidy (0 vs. 2/5.3% samples), mosaicism (1/1.3% vs. 0 samples) in the group A and the group B, respectively. No SSD was found between the groups (p>0.05). Conclusions The results of our study demonstrated that the 1st PB transfer does not affect the chromosomal set of embryos obtained from modified oocytes in comparison with the original oocytes. This technique is useful to increase the number of female germ cells and avoid the full oocytes donation especially for patients with low ovarian reserve and for poor responders.