[Effects of controlled ovarian hyperstimulation on mitochondria copy number and functions in murine oocytes]

To investigate the effect of whether controlled ovarian hyperstimulation (COH) on mitochondrial DNA (mtDNA) copy number, mitochondrial function, distribution, the level of reactive oxygen species (ROS) in oocytes and the mechanism of oocyte loss in COH.

Matured murine oocytes were classified into COH group and natural cycles (NC) group. The copies of mtDNA, the magnitude of mitochondrial membrane potential (Δφm) and oocyte adenosine triphosphate (ATP) content, pattern of mitochondrial distribution, and ROS levels were evaluated by realtime PCR, immunofluorescence and fluorescence-luciferase mensuration.

The copies of mtDNA, the levels of Δφm, and ATP content in oocytes between COH and NC groups showed statistical difference [(1.15 ± 0.01)×10(5), 0.34 ± 0.03 and (241 ± 20) fmol/oocyte (COH)] versus [(2.15 ± 0.19)×10(5), 0.82 ± 0.07 and (325 ± 11) fmol/oocyte (NC)], respectively(P < 0.05). However, there were no significant differences in the rate of evenly distributed mitochondria and the level of ROS in oocytes from COH and NC [(76.5% (78/102) in COH versus 82.1% (69/84)]; 1.07 ± 0.07 in COH versus 0.93 ± 0.08 in NC (P > 0.05).

It was indicated that non-physiological COH treatments inhibit mtDNA replication, alter mitochondrial function, which might partly be involved in the low development potential of COH oocyte.