Multiple rearrangements of mitochondrial DNA in unfertilized human oocytes

Objective: To determine the rearrangement of mitochondrial DNA (mtDNA) in unfertilized human oocytes and compromised embryos to evaluate the fertilization capacity of oocytes. Design: Prospective laboratory research. Setting: IVF laboratory in a university hospital. Patient(s): One hundred twenty-four unfertilized oocytes, 98 arrested embryos. and 45 tripronucleate (3PN) embryos from 65 female patients undergoing in vitro fertilization (IVF). Interventions(s): Unfertilized oocytes and poor quality embryos were collected 48 hours after IVF. Main Outcome Measure(s): Comparison of the frequency of mtDNA deletions and fertilization rates of oocytes. Result(s): Multiple deletions of mtDNA were found in unfertilized oocytes and arrested embryos obtained from IVF patients. A 4977-bp deletion was the most frequent deletion in human oocytes and embryos. About 66.1% of the unfertilized oocytes, 34.8% of the arrested or fragmented embryos, and 21.1% of the 3PN embryos harbored the 4977-bp deletion of mtDNA. There was a significant increase in the proportion of deleted mtDNA in unfertilized oocytes. Conclusion(s): Accumulation of mtDNA deletions may contribute to mitochondrial dysfunction and impaired ATP production. We conclude that the accumulation of rear-ranged mtDNA may interfere with fertilization of human oocytes and further embryonic development. (Fertil Steril(R) 2002 77:1012-7. (C) 2002 by American Society for Reproductive Medicine).