Abstract
With the nucleus as an exception, mitochondria are the only animal cell organelles containing their own genetic information, called mitochondrial DNA (mtDNA). During oocyte maturation, the mtDNA copy number dramatically increases and the distribution of mitochondria changes significantly. As oocyte maturation requires a large amount of ATP for continuous transcription and translation, the availability of the right number of functional mitochondria is crucial. There is a correlation between the quality of oocytes and both the amount of mtDNA and the amount of ATP. Suboptimal conditions of in vitro maturation (IVM) might lead to changes in the mitochondrial morphology as well as alternations in the expression of genes encoding proteins associated with mitochondrial function. Dysfunctional mitochondria have a lower ability to counteract reactive oxygen species (ROS) production which leads to oxidative stress. The mitochondrial function might be improved with the application of antioxidants and significant expectations are laid on the development of new IVM systems supplemented with mitochondria-targeted reagents. Different types of antioxidants have been tested already on animal models and human rescue IVM oocytes, showing promising results. This review focuses on the recent observations on oocytes’ intracellular mitochondrial distribution and on mitochondrial genomes during their maturation, both in vivo and in vitro. Recent mitochondrial supplementation studies, aiming to improve oocyte developmental potential, are summarized.
Highlights
Published: 19 September 2021In vitro maturation (IVM) technology is one of the most promising artificial reproductive technologies, as it allows fertility specialists to obtain oocytes without any or minimal hormonal stimulation on any day of the menstrual cycle [1]
It is possible that mitochondrial contact site (MICOS) may have a role in anchoring mitochondrial DNA (mtDNA) on the inner mitochondrial membrane (IMM) surface in order to prevent their free diffusion around the separating mitochondria
Mitochondria are found in high numbers in oocytes as they provide energy for its maturation
Summary
In vitro maturation (IVM) technology is one of the most promising artificial reproductive technologies, as it allows fertility specialists to obtain oocytes without any or minimal hormonal stimulation on any day of the menstrual cycle [1] It is mostly suitable for patients with polycystic ovarian morphology, oncological patients, or women with resistant ovary syndrome. At the same time, the oocyte loses gap junctions with the cumulus cells and, supplementation with nutrients and signaling molecules stops, which leaves the cytoplasm immature This means that the oocyte’s organelles have a structure and localization typical for the germinal vesicle (GV). The oocyte within the follicle undergoes major structural and biochemical transformations and has to complete two meiotic divisions Along with this energy-demanding process, the quantity and quality of mitochondria as well as their distribution pattern in an oocyte change [9].
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