Subcellular Characterization of Porcine Oocytes with Different Glucose-6-phosphate Dehydrogenase Activities.

Bo Fu,Bo Fu,Xiu-Qin Yang,Di Liu,Yun-Yun Guo,Dong-Jie Zhang,Meng Zhu,Tie-Zhu An,Tie-Zhu An,Zhen-Hua Guo,Jing Bai,Liang Ren,Hong Ma,Jian-Zhang Ma

doi:10.5713/ajas.15.0051

Abstract

The in vitro maturation (IVM) efficiency of porcine embryos is still low because of poor oocyte quality. Although brilliant cresyl blue positive (BCB+) oocytes with low glucose-6-phosphate dehydrogenase (G6PDH) activity have shown superior quality than BCB negative (−) oocytes with high G6PDH activity, the use of a BCB staining test before IVM is still controversial. This study aimed to shed more light on the subcellular characteristics of porcine oocytes after selection using BCB staining. We assessed germinal vesicle chromatin configuration, cortical granule (CG) migration, mitochondrial distribution, the levels of acetylated lysine 9 of histone H3 (AcH3K9) and nuclear apoptosis features to investigate the correlation between G6PDH activity and these developmentally related features. A pattern of chromatin surrounding the nucleoli was seen in 53.0% of BCB+ oocytes and 77.6% of BCB+ oocytes showed peripherally distributed CGs. After IVM, 48.7% of BCB+ oocytes had a diffused mitochondrial distribution pattern. However, there were no significant differences in the levels of AcH3K9 in the nuclei of blastocysts derived from BCB+ and BCB− oocytes; at the same time, we observed a similar incidence of apoptosis in the BCB+ and control groups. Although this study indicated that G6PDH activity in porcine oocytes was correlated with several subcellular characteristics such as germinal vesicle chromatin configuration, CG migration and mitochondrial distribution, other features such as AcH3K9 level and nuclear apoptotic features were not associated with G6PDH activity and did not validate the BCB staining test. In using this test for selecting porcine oocytes, subcellular characteristics such as the AcH3K9 level and apoptotic nuclear features should also be considered. Adding histone deacetylase inhibitors or apoptosis inhibitors into the culture medium used might improve the efficiency of IVM of BCB+ oocytes.

Highlights

Glucose-6-phosphate dehydrogenase (G6PDH) activity decreases with oocyte maturation (Alm et al, 2005; Submitted Jan. 18, 2015; Revised Apr. 11, 2015; Accepted May 8, 2015Bhojwani et al, 2007)
While most of the brilliant cresyl blue (BCB)– oocytes had an non-surrounded nucleoli (NSN) configuration, more BCB+ oocytes were of the SN pattern (Figure 2)
This result suggests that chromatin configuration patterns were associated with G6PDH activity in oocytes

Summary

Introduction

Glucose-6-phosphate dehydrogenase (G6PDH) activity decreases with oocyte maturation (Alm et al, 2005; Submitted Jan. 18, 2015; Revised Apr. 11, 2015; Accepted May 8, 2015Bhojwani et al, 2007). After being selected with BCB staining, COCs with an significance of these features among BCB+, BCB–, and evenly distributed cytoplasm and at least three compact control oocytes should be clarified. PA embryos derived from BCB+, BCB−, and control oocytes were examined for cleavage at 48 h after activation.

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Results

Conclusion