Embryonic development kinetics after autologous bone marrow mesenchymal stem cell- derived mitochondria transfer into compromised oocytes：a prospective self-controlled study

We aimed to explore whether autologous bone marrow mesenchymal stem cell(BMSC)-derived mitochondria transfer into compromised oocytes change their embryonic development kinetics and improve outcomes in women with multiple in vitro fertilization (IVF)/ Intracytoplasmic sperm injection (ICSI) failures due to low oocyte quality A prospective self-controlled study This prospective self-controlled study was conducted at the Department of Assisted Reproduction of the sixth affiliated hospital of Sun-Yet san university from January 2018 to June 2018. Patients were voluntarily enrolled meeting the following criteria: [1] undergoing ICSI program, [2]<42 years of age, [3] body mass index <30 kg/m2, [4]at least one previous failed IVF with Low embryo quality. Low embryo quality was understood as 1) no fertilized MIIs; 2) deficient-quality embryos according to morphologic criteria ; 3) arrested embryos. Patients with abnormal chromosome were excluded. BMSCs were isolated from 20ml bone marrow and cultured. Three days before oocyte retrieval, mitochondria were isolated by differential centrifugation from BMSCs. The retrieved oocytes were randomly and averagely divided into two groups i.e. Mitochondria transfer (MT) groups and control group. In MT group, 4000-5000 copies mitochondria DNA were injected into each oocyte during intracytoplasmic sperm injection. By means of a time-lapse system (EmbryoScope; Unisense FertiliTech, Aarhus, Denmark), this study determined the timing of a number of developmental parameters including cleavage timing from a zygote to a 8-cell embryo (t2, t3, t4, t5, t6, t7, t8) and assessed fragmentation at each stage. The intervals between two consecutive cleavages were also analyzed. Duration of the second cell cycle (cc2 =t 3 – t2) is the time from the division into a two-blastomere embryo until the time to the division into a three-blastomere embryo, and second synchrony (s2 =t 4 – t3) is the time from this division into a four-blastomere embryo. A total of 25 patients were included and we got 231 oocytes in total. Their average age was 33.00 years old. The average antimullerian hormone level and antral follicles was 3.86 ng/ml and 14.68 respectively. Most of patients was primary infertility(72.22%) and the major cause of infertility was tubar factor(64.00%). We observed that the timings of all embryo cleavage stages (from t2to t8) together with fragmentation values showed no significant differences between embryos deriving from oocytes with MT or without MT. It was noteworthy that s2 was shorter in MT group, although difference didn’t reach statistical significance ( 4.20 vs. 5.90). in addition, Oocytes of MT groups had little higher fertilization rate (89.06% vs.88.35%, P= 0.865). This study demonstrated that BMSC-derived autologous mitochondria transfer didn’t alter embryonic development kinetics. It might help to improve embryo development synchrony and fertilization.