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Cellular and molecular alterations of buffalo oocytes cultured under two different levels of oxygen tension during in vitro maturation

Published online by Cambridge University Press:  24 February 2021

Nasser Ghanem Open the ORCID record for Nasser Ghanem [Opens in a new window] ,
Dalia Abd-El Rahman Ahmed ,
Sherif Mohamed Dessouki ,
Marwa Said Faheem ,
Ahmed Yehia Gad ,
Jaana Peippo  and
Ashraf Hesham Barkawi
Nasser Ghanem*
Affiliation:
Department of Animal Production, Faculty of Agriculture, Cairo University, Giza, Egypt Cairo University Research Park, Faculty of Agriculture, Cairo University, Giza, Egypt
Dalia Abd-El Rahman Ahmed
Affiliation:
Department of Animal Production, Faculty of Agriculture, Cairo University, Giza, Egypt
Sherif Mohamed Dessouki
Affiliation:
Department of Animal Production, Faculty of Agriculture, Cairo University, Giza, Egypt
Marwa Said Faheem
Affiliation:
Department of Animal Production, Faculty of Agriculture, Cairo University, Giza, Egypt
Ahmed Yehia Gad
Affiliation:
Department of Animal Production, Faculty of Agriculture, Cairo University, Giza, Egypt
Jaana Peippo
Affiliation:
Natural Resources Institute Finland (Luke), Myllytie 1, FI-31600Jokioinen, Finland
Ashraf Hesham Barkawi*
Affiliation:
Department of Animal Production, Faculty of Agriculture, Cairo University, Giza, Egypt
*
Authors for correspondence: Ashraf Hesham Barkawi. Cairo University, Faculty of Agriculture, Department of Animal Production, El-Gamaa Street, 12613 Giza, Egypt. E-mail: ashrafb53@yahoo.com; Nasser Ghanem. Cairo University, Faculty of Agriculture, Department of Animal Production, El-Gamaa street, 12613 Giza, Egypt. E-mail: nassergo@agr.cu.edu.eg
Authors for correspondence: Ashraf Hesham Barkawi. Cairo University, Faculty of Agriculture, Department of Animal Production, El-Gamaa Street, 12613 Giza, Egypt. E-mail: ashrafb53@yahoo.com; Nasser Ghanem. Cairo University, Faculty of Agriculture, Department of Animal Production, El-Gamaa street, 12613 Giza, Egypt. E-mail: nassergo@agr.cu.edu.eg
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Summary

This study was conducted to monitor the cellular and molecular changes of buffalo cumulus–oocytes complexes (COCs) cultured under high or low oxygen levels. Morphologically good quality COCs (n = 1627) were screened using brilliant cresyl blue (BCB) staining and placed into three groups (BCB+, BCB− and control). All groups of COCs were cultured under low (5%) or high (20%) oxygen tensions. Intracellular and molecular changes including oocyte ultrastructure, lipid contents, mitochondrial activity and transcript abundance of genes regulating different pathways were analyzed in the matured oocyte groups. The results revealed that oxygen tension did not affect cumulus expansion rates, however the BCB+ group had a higher (P ≤ 0.05) expansion rate compared with the BCB− group. BCB− oocytes recorded the lowest meiotic progression rate (P ≤ 0.05) under high oxygen levels that was linked with an increased level of reactive oxygen species (ROS) compared with the BCB+ oocytes. Ultrastructure examination indicated that BCB+ oocytes had a higher rate of cortical granules migration compared with BCB− under low oxygen tension. In parallel, our results indicated the upregulation of NFE2L2 in groups of oocytes cultured under high oxygen tension that was coupled with reduced mitochondrial activity. In contrast, the expression levels of MAPK14 and CPT2 genes were increased (P ≤ 0.05) in groups of oocytes cultured under low compared with high oxygen tension that was subsequently associated with increased mitochondrial activity. In conclusion, data from the present investigation indicated that low oxygen tension is a favourable condition for maintaining the mitochondrial activity required for nuclear maturation of buffalo oocytes. However, low-quality oocytes (BCB−) responded negatively to high oxygen tension by reducing the expression of gene-regulating metabolic activity (CPT2). This action was an attempt by BCB− oocytes to reduce the increased levels of endogenously produced ROS that was coupled with decreased expression of the gene controlling meiotic progression (MAPK14) in addition to nuclear maturation rate.

Keywords

BCB oocytesGene expressionOxidative stressUltrastructure
Type
Research Article
Information
Zygote , Volume 29 , Issue 4 , August 2021 , pp. 314 - 324
Copyright
© The Author(s), 2021. Published by Cambridge University Press

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