Mitochondrial Activity and Transcript Abundance of Quality Marker Genes during In vitro Maturation of Bovine and Buffalo’s Oocytes

Abstract

In vitro embryo production is a well-known biotechnology tool to improve and sustain animal productivity. Therefore, optimization of this technique would enhance both animal productivity and farm profitability. The aim of the present study was to compare the mitochondrial activity and patterns of expression of genes that contribute to its regulation during the in vitro maturation of buffalo (Bubalus bubalis) and bovine (Bos indicus) oocytes. Ovaries were collected from local Egyptian abattoirs and cumulus-oocytes complexes (COCs)were aspirated from 2-8mm follicles diameter and were divided into four categories according to oocyte morphology. The grade A and grade B were cultured in TCM medium (supplemented with all required chemicals and hormones) for 22 hours at 38.5 o C and collected after their in vitro maturation (IVM). The total RNA of the oocytes was then extracted and target mitochondrial transcripts (TFAM and CPT2) were analyzed by real-time PCR. The results of this work revealed the intensity of mitochondria and lipids was reduced in good than bad matured bovine oocytes. However, there was no change of mitochondrial and lipid fluorescent intensities of bad quality oocytes before and after in vitro maturation. The expression profile of CPT2 gene was higher in immature compared to matured oocytes of bovine while, buffalo oocytes did not shown differences in the expression of this gene. Furthermore, the expression profile of CPT2 gene was lower in immature and matured buffalo oocytes than those of bovine. The transcript abundance of TFAM did not indicate any differences among in vitro maturation of both species. It was concluded that the patterns of the gene expression of CPT2 vary during in vitro maturation of bovine oocytes in reflecting their maturation competence than that of buffalo. Increased metabolic activity of oocytes during IVM is in line with CPT2 expression that is involved in lipid oxidation required for this process.

Gonadotropin supplementation improved in vitro developmental capacity of Egyptian goat oocytes by modulating mitochondrial distribution and utilization

“…Indeed, peripheral localization is more common in meiotically incompetent oocytes, which showed no sign of cumulus expansion and a clustered mitochondrial distribution pattern (Kirillova, et al, 2021). Therefore, it seems that increased fluorescent mitochondrial intensity in oocytes matured in vitro in medium supplemented with high hCG enhanced maturation rate by providing metabolic requirements (Ghanem et al, 2021a;Ghanem et al, 2021b;Torner et al, 2008).…”

“…The in vitro-matured goat oocytes were fixed with 4% paraformaldehyde in a PVP-PBS solution. The fluorescent staining of intracellular goat oocyte mitochondria was performed using Mito-Tracker green® dye (Invirogen-M7514, USA) dissolved in DMSO (125 nm) and incubated for 5 minutes in the dark at room temperature according to Ghanem et al (2021a). This was followed by three times washing in PVP-PBS solution for 15 minutes each.…”

“…The findings suggest that the addition of hCG to the fertilization culture medium may be advantageous for stimulation cycles that contain a large percentage of immature oocytes. In vitromatured good-quality bovine and buffalo oocytes had higher fluorescent mitochondrial intensity than bad-quality oocytes (Ghanem et al, 2021a). Therefore, it seems that increased fluorescent mitochondrial intensity in oocytes matured in vitro in a medium supplemented with high hCG enhanced the maturation rate by providing metabolic requirements (Ghanem et al, 2021a;Ghanem et al, 2021b;Torner et al, 2008).…”

“…In this regard, cytoplasmic maturation is one of the key changes that are essential for the maturation process. The mitochondrial distribution and metabolic activity (mitochondrial intensity) impact oocyte cytoplasmic and nuclear maturation (Czernik et al, 2022;Ghanem et al, 2021a;Ghanem et al, 2021b;Torner et al, 2008). At the cellular level, it is known that the distribution of active mitochondria within the oocyte is indicative of energy and ion requirements necessary for various key events during oocyte maturation and fertilization (Reader et al, 2017).…”