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 38.5o 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.