Mitochondrial Transfer into Human Oocytes Improved Embryo Quality and Clinical Outcomes in Recurrent Pregnancy Failure Cases.

One of the most critical issues to be solved in reproductive medicine is the treatment of patients with multiple failures of assisted reproductive treatment caused by low-quality embryos. This study investigated whether mitochondrial transfer to human oocytes improves embryo quality and provides subsequent acceptable clinical results and normality to children born due to the use of this technology. We transferred autologous mitochondria extracted from oogonia stem cells to mature oocytes with sperm at the time of intracytoplasmic sperm injection in 52 patients with recurrent failures (average 5.3 times). We assessed embryo quality using the following three methods: good-quality embryo rates, transferable embryo rates, and a novel embryo-scoring system (embryo quality score; EQS) in 33 patients who meet the preset inclusion criteria for analysis. We also evaluated the clinical outcomes of the in vitro fertilization and development of children born using this technology and compared the mtDNA sequences of the children and their mothers. The good-quality embryo rates, transferable embryo rates, and EQS significantly increased after mitochondrial transfer and resulted in 13 babies born in normal conditions. The mtDNA sequences were almost identical to the respective maternal sequences at the 83 major sites examined. Mitochondrial transfer into human oocytes is an effective clinical option to enhance embryo quality in recurrent in vitro fertilization-failure cases.

Treatment with Laevo (L)-carnitine reverses the mitochondrial function of human embryos.

PURPOSE: Laevo (l)-carnitine plays important roles in reducing the cytotoxic effects of free fatty acids by forming acyl-carnitine and promoting beta-oxidation, leading to alleviation of cell damage. Recently, the mitochondrial functions in morula has been shown to decrease with the maternal age. Here, we assessed the effect of l-carnitine on mitochondrial function in human embryos and embryo development. METHODS: To examine the effect of L-carnitine on mitochondrial function in morulae, 38 vitrified-thawed embryos at the 6-11-cell stage on day 3 after ICSI were donated from 19 couples. Each couple donated two embryos. Two siblings from each couple were divided randomly into two groups and were cultured in medium with or without 1 mM L-carnitine. The oxygen consumption rates (OCRs) were measured at morula stage. The development of 1029 zygotes cultured in medium with or without L-carnitine was prospectively analyzed. RESULTS: Addition of L-carnitine to the culture medium significantly increased the OCRs of morulae and improved the morphologically-good blastocyst formation rate per zygote compared with sibling embryos. Twenty healthy babies were born from embryos cultured in L-carnitine-supplemented medium after single embryo transfers. CONCLUSION(S): L-carnitine is a promising culture medium supplement that might be able to counteract the decreased mitochondrial function in human morula stage embryos.

Mitochondrial oxygen consumption rate of human embryos declines with maternal age.

PURPOSE: The fertility of women decreases with age because of factors such as an increased incidence of aneuploidies and-possibly-decreased mitochondrial activity in oocytes. However, the relationship between maternal aging and mitochondrial function of their embryos remains unknown. Here, we assessed the relationship between maternal age and mitochondrial functions in their oocytes and embryos METHODS: The relationships between maternal age and oxygen consumption rates (OCRs), mitochondrial DNA (mtDNA) copy numbers, or blastocyst development was investigated using 81 embryos donated from 63 infertility couples. The developmental rates from morulae to blastocysts were retrospectively analyzed using data of 105 patients. RESULTS: The OCRs of morulae decreased with maternal age (r2 = 0.48, P < 0.05) although there were no relationships between maternal age and mtDNA copy number in any stages. The more oxygen consumed at the morula stage, the shorter time was required for embryo development to the mid-stage blastocyst (r2 = 0.236, P < 0.05). According to the clinical data analysis, the developmental rate from morulae to blastocysts decreased with maternal age (P < 0.05, < 37 years, 81.1%, vs. ≥ 37 years, 64.1%). CONCLUSIONS: The data of the present study revealed that mitochondrial function at the morula stage of human embryos decreased with their maternal age and a decrease of mitochondrial function led to slow-paced development and impaired developmental rate from morulae to blastocysts.

Quantitative and qualitative changes of mitochondria in human preimplantation embryos.

PURPOSE: The oxygen consumption rates (OCRs) in mice and cattle have been reported to change during preimplantation embryogenesis. On the other hand, mitochondrial DNA (mtDNA) copy number has been shown to be unchanged in mice and changed in cattle and pigs. The interactions between mitochondrial functions and mtDNA copy numbers in human embryos during preimplantation development remain obscure. METHODS: Sixteen oocytes and 100 embryos were used to assess mtDNA copy numbers and OCR. Three oocytes and 12 embryos were used to determine cytochrome c oxidase activity. All specimens were obtained between July 2004 and November 2014, and donated from couples after they had given informed consent. Mature oocytes and embryos at 2-14-cell, morula, and blastocyst stages were used to assess their OCR in the presence or absence of mitotoxins. The mtDNA copy number was determined using the samples after analysis of OCR. The relationships between developmental stages and OCR, and developmental stages and mtDNA copy number were analyzed. Furthermore, cytochrome c oxidase activity was determined in oocytes and 4-cell to blastocyst stage embryos. RESULTS: The structure of inner mitochondrial membranes and their respiratory function developed with embryonic growth and the mtDNA copy numbers decreased transiently compared with those of oocytes. The undifferentiated state of inner cell mass cells appears to be associated with a low OCR. On the other hand, the mtDNA copy numbers increased and aerobic metabolism of mitochondria increased in trophectoderm cells. CONCLUSIONS: The mitochondrial respiratory function of human embryos developed along with embryonic growth although the copy numbers of mtDNA decreased transiently before blastulation. OCRs increased toward the morula stage ahead of an increase of mtDNA at the time of blastulation. Data regarding changes in mitochondrial function and mtDNA copy number during preimplantation development of human embryos will be useful for the development of ideal culture media.