Intracellular glutathione content, developmental competence and expression of apoptosis-related genes associated with G6PDH-activity in goat oocyte

Abstract

Purpose: To associate glucose-6-phosphate dehydrogenase (G6PDH) activity in goat oocytes with intracellular glutathione (GSH) content, meiotic competence, developmental potential, and relative abundance of Bax and Bcl-2 genes transcripts.

Methods: Goat oocytes were exposed to brilliant cresyl blue (BCB) staining test and categorized into BCB(+) (blue-cytoplasm), and BCB(-) (colorless-cytoplasm) groups. A group of oocytes were not exposed to BCB test and was considered as a control group. After maturation in vitro, a group of oocytes were used for determination of nuclear status and intracellular GSH content while another group was subjected to parthenogenetic activation followed by in vitro embryo culture.

Results: We found that BCB(+) oocytes not only yielded higher rate of maturation, but also showed an increased level of intracellular GSH content than BCB(-) and control oocytes. Furthermore, BCB(+) oocytes produced more blastocysts than BCB(-) and control oocytes. Our data revealed that the expression of anti-apoptotic (Bcl-2) and pro-apoptotic (Bax) genes were interacted with G6PDH-activity in mature oocyte, their surrounding cumulus cells, and blastocyst-stage embryos.

Conclusions: The results of this study demonstrate that selection of goat oocytes based on G6PDH-activity through the BCB test improves their developmental competence, increases intracellular GSH content, and affects the expression of the apoptosis-related genes.

Fig. 1

Goat oocytes stained with Hoechst 33258 and evaluated under epifluorescence microscope, demonstrating oocytes in GV (a), GVBD (b), MI (c), and MII (d) stages

Fig. 2

Effect of glucose-6-phosphate dehydrogenase (G6PDH) activity in goat oocytes on interacellular GSH level after in vitro maturation (IVM). BCB brilliant cresyl blue. ^a,b Bars with different letters represent groups that are significantly different (P < 0.05)

Fig. 3

Relative mRNA expression of Bax and Bcl-2 genes for mature oocytes selected on their glucose-6-phosphate dehydrogenase (G6PDH) activity. BCB brilliant cresyl blue. ^* Asterisk shows significant difference between the groups (P < 0.05)

Fig. 4

Relative mRNA expression of Bax and Bcl-2 genes for cumulus cells of mature oocytes selected on their glucose-6-phosphate dehydrogenase (G6PDH) activity. BCB brilliant cresyl blue. ^* Asterisk shows significant difference between the groups (P < 0.05)

Fig. 5

Relative mRNA expression of Bax and Bcl-2 genes for blastocysts derived from oocytes that were selected on their glucose-6-phosphate dehydrogenase (G6PDH) activity. BCB brilliant cresyl blue. ^* Asterisk shows significant difference between the groups (P < 0.05)