Mitochondrial function of human embryo: Decline in their quality with maternal aging

BACKGROUND: Female fertility declines with age, due to increased chromosomal aneuploidy and possible reduced mitochondrial function in the embryo. METHODS: This review outlines how mitochondrial function in human embryos, as predicted from oxygen consumption rate (OCR) measurements, changes in preimplantation stage, and what factors, particularly maternal age, affect mitochondrial function in embryos. MAIN FINDINGS: The structure of the mitochondrial inner membrane and its respiratory function developed with embryo development, while the copy number of mitochondrial DNA per specimen was transiently reduced compared with that of the oocyte. The undifferentiated state of the inner cell mass cells appears to be associated with a low OCR. In contrast, the copy number of mitochondrial DNA increased in trophoblast cells and mitochondrial aerobic metabolism increased. The OCRs at morulae stage decreased with maternal age, but there was no relationship between maternal age and the copy number of mitochondrial DNA at any stages. The higher oxygen spent at the morula stage; the shorter time was needed for development to the mid‐stage blastocyst. CONCLUSIONS: The mitochondrial respiratory function of human embryos developed along with embryonic growth. Mitochondrial function at morula stage declined with their maternal age and reduced mitochondrial function decreased the rate of development from morula to blastocyst.