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Mitochondria are the most abundant organelles in mammalian oocytes and early embryos. Previous data have shown that mitochondrial DNA (mtDNA) deletions are present both in human oocytes and in embryos from in vitro fertilization (IVF) patients and suggest that accumulation of these deletions may contribute to mitochondrial dysfunction and impaired ATP production. In addition, high levels of mitochondrial mutations are present in skeletal muscle fibers from aged rhesus macaques. The specific aims of this study were to determine whether the mitochondrial common deletion is present in non-human primate oocytes and embryos generated by IVF and to determine whether mtDNA mutations are already present in immature oocytes from rhesus ovaries. Using a nested primer polymerase chain reaction (PCR) strategy, we determined the frequency of the rhesus common deletion in immature oocytes compared with stimulated oocytes and embryos. There was a low incidence (21%) of the rhesus common deletion present in immature, unstimulated oocytes derived from necropsied ovaries of 2 to 10-yr-old rhesus macaques. However, there was >3-fold increase (71.4%) in the frequency of deleted mtDNA in stimulated oocytes and IVF embryos from age-matched fertile monkeys. We postulated that, in addition to skeletal muscle, a similar time-dependent accumulation of mtDNA deletions occurs in fertile rhesus macaque oocytes and embryos. We are now investigating the effects of culture and passage number on mtDNA deletions in primate adult and embryonic stem cells. We propose the rhesus monkey to be an excellent model to assess the quality of gametes and embryos, as well as stem cells, and their developmental competence in human and non-human primates.<fn_group><fn>This study was supported by National Institutes of Health grants RR15395 and HD045966.</fn></fn_group> |
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