The Association of Mitochondrial Potential and Copy Number with Pig Oocyte Maturation and Developmental Potential

Abstract

ATP is critical for oocyte maturation, fertilization, and subsequent embryo development. Both mitochondrial membrane potential and copy number expand during oocyte maturation. In order to differentiate the roles of mitochondrial metabolic activity and mtDNA copy number during oocyte maturation, we used two inhibitors, FCCP (carbonyl cyanide p-(tri-fluromethoxy)phenyl-hydrazone) and ddC (2’3-dideoxycytidine), to deplete the mitochondrial membrane potential (Δφm) and mitochondrial copy number, respectively. FCCP (2000 nM) reduced ATP production by affecting mitochondrial Δφm, decreased the mRNA expression of Bmp15 (bone morphogenetic protein 15), and shortened the poly(A) tails of Bmp15, Gdf9 (growth differentiation factor 9), and Cyclin B1 transcripts. FCCP (200 and 2000 nM) also affected p34cdc2 kinase activity. By contrast, ddC did not alter ATP production. Instead, ddC significantly decreased mtDNA copy number (P < 0.05). FCCP (200 and 2000 nM) also decreased extrusion of the first polar body, whereas ddC at all concentrations did not affect the ability of immature oocytes to reach metaphase II. Both FCCP (200 and 2000 nM) and ddC (200 and 2000 µM) reduced parthenogenetic blastocyst formation compared with untreated oocytes. However, these inhibitors did not affect total cell number and apoptosis. These findings suggest that mitochondrial metabolic activity is critical for oocyte maturation and that both mitochondrial metabolic activity and replication contribute to the developmental competence of porcine oocytes.

Changes in mitochondrial function in porcine vitrified MII-stage oocytes and their impacts on apoptosis and developmental ability

“…This study showed that porcine vitrified MII-stage oocytes had an obvious increased apoptotic rate and decreased survival rate and parthenogenetic cleavage rate. Mitochondria play an important role in the development of oocytes and embryos, and their damage is closely related to apoptosis [16]. In the present study, not only the ultrastructure and distribution of mitochondria, DWm, ATP concentration, ROS level after vitrification decreased greatly, but also the gene expression (SOD1, Mfn2 and Dnm1) of vitrified oocytes could reflect the injury of mitochondrial function.…”

Mitochondrial biogenesis and degradation are induced by CCCP treatment of porcine oocytes

“…The results indicate that some aspects of mitochondrial damage are restored during oocyte maturation or that either partial or moderate disruption of mitochondrial function does not severely affect oocyte parthenogenetic development. Lee et al (2014) reported that when porcine oocytes were treated with FCCP, a mitochondrial uncoupler, throughout the maturation period, the FCCP treatment resulted in a reduction of the mitochondrial number and in the developmental ability of oocytes. These contrasting results are likely due to overly long periods of FCCP treatment.…”

The Role of Glucose Metabolism on Porcine Oocyte Cytoplasmic Maturation and Its Possible Mechanisms

“…Total RNA extraction and cDNA synthesis were performed as described previously [22]. Briefly, 50 MII-stage oocytes or 20 blastocysts were used to extract mRNA using the Ambion Dynabeads mRNA Direct Kit (Thermo Fisher Scientific).…”