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Developmental potential of prepubertal mouse oocytes is compromised due mainly to their impaired synthesis of glutathione.

Jiao GZ, Cao XY, Cui W, Lian HY, Miao YL, Wu XF, Han D, Tan JH - PLoS ONE (2013)

Bottom Line: Although oocytes from prepubertal animals are found less competent than oocytes from adults, the underlying mechanisms are poorly understood.Whereas reactive oxygen species (ROS) levels increased, Ca(2+) storage decreased significantly in prepubertal oocytes.Maternal eCG priming improved all the parameters and eliminated the age difference.

View Article: PubMed Central - PubMed

Affiliation: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, People's Republic of China.

ABSTRACT
Although oocytes from prepubertal animals are found less competent than oocytes from adults, the underlying mechanisms are poorly understood. Using the mouse oocyte model, this paper has tested the hypothesis that the developmental potential of prepubertal oocytes is compromised due mainly to their impaired potential for glutathione synthesis. Oocytes from prepubertal and adult mice, primed with or without eCG, were matured in vitro and assessed for glutathione synthesis potential, oxidative stress, Ca(2+) reserves, fertilization and in vitro development potential. In unprimed mice, abilities for glutathione synthesis, activation, male pronuclear formation, blastocyst formation, cortical granule migration and polyspermic block were all compromised significantly in prepubertal compared to adult oocytes. Cysteamine and cystine supplementation to maturation medium significantly promoted oocyte glutathione synthesis and blastocyst development but difference due to maternal age remained. Whereas reactive oxygen species (ROS) levels increased, Ca(2+) storage decreased significantly in prepubertal oocytes. Levels of both catalytic and modifier subunits of the γ-glutamylcysteine ligase were significantly lower in prepubertal than in adult oocytes. Maternal eCG priming improved all the parameters and eliminated the age difference. Together, the results have confirmed our hypothesis by showing that prepubertal oocytes have a decreased ability to synthesize glutathione leading to an impaired potential to reduce ROS and to form male pronuclei and blastocysts. The resulting oxidative stress decreases the intracellular Ca(2+) store resulting in impaired activation at fertilization, and damages the microfilament network, which affects cortical granule redistribution leading to polyspermy.

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Intracellular GSX concentrations and GSH/GSSG ratio in mouse oocytes.The GSX in oocytes at the GV stage (the upper left panel) were measured immediately after oocyte recovery from unstimulated (eCG−) or eCG-primed (eCG+) prepubertal (Prepb) or adult mice. The GSX concentration (the right panel) and GSH/GSSG ratio (the lower left panel) in MII oocytes were observed after in vitro maturation with or without C (cysteamine, 200 µM)/C (cystine, 400 µM) supplementation. Each treatment was repeated 3 times with each replicate containing 35–40 oocytes. a–e: Values without a common letter above their bars differ (P<0.05) within panels.
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pone-0058018-g005: Intracellular GSX concentrations and GSH/GSSG ratio in mouse oocytes.The GSX in oocytes at the GV stage (the upper left panel) were measured immediately after oocyte recovery from unstimulated (eCG−) or eCG-primed (eCG+) prepubertal (Prepb) or adult mice. The GSX concentration (the right panel) and GSH/GSSG ratio (the lower left panel) in MII oocytes were observed after in vitro maturation with or without C (cysteamine, 200 µM)/C (cystine, 400 µM) supplementation. Each treatment was repeated 3 times with each replicate containing 35–40 oocytes. a–e: Values without a common letter above their bars differ (P<0.05) within panels.

Mentions: Some GV oocytes were assayed for intra-oocyte GSX immediately after collection, whereas others were matured with or without C/C supplementation before assay for GSX and the GSH/GSSG ratio. In unstimulated mice, intra-oocyte GSX was significantly higher in adult than in prepubertal oocytes at both the GV and MII stage (Fig. 5). When mice were primed with eCG, however, the GSX level of both prepubertal and adult oocytes increased significantly and to the same level. C/C supplementation increased GSX synthesis in both eCG-stimulated and unstimulated oocytes but it could not eliminate the age difference in unstimulated mice. The level of GSH was lower significantly in prepubertal than in adult oocytes (0.36±0.04 vs. 0.69±0.07, P<0.05) while the GSSG content was similar between the two age groups (1.97±0.02 vs. 1.96±0.03, P>0.05). As a result, the GSH/GSSG ratio was significantly higher in adult than prepubertal oocytes when mice were not primed with eCG (Fig. 5). However, eCG eliminated the age difference in the GSH/GSSG ratio.


Developmental potential of prepubertal mouse oocytes is compromised due mainly to their impaired synthesis of glutathione.

Jiao GZ, Cao XY, Cui W, Lian HY, Miao YL, Wu XF, Han D, Tan JH - PLoS ONE (2013)

Intracellular GSX concentrations and GSH/GSSG ratio in mouse oocytes.The GSX in oocytes at the GV stage (the upper left panel) were measured immediately after oocyte recovery from unstimulated (eCG−) or eCG-primed (eCG+) prepubertal (Prepb) or adult mice. The GSX concentration (the right panel) and GSH/GSSG ratio (the lower left panel) in MII oocytes were observed after in vitro maturation with or without C (cysteamine, 200 µM)/C (cystine, 400 µM) supplementation. Each treatment was repeated 3 times with each replicate containing 35–40 oocytes. a–e: Values without a common letter above their bars differ (P<0.05) within panels.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3585726&req=5

pone-0058018-g005: Intracellular GSX concentrations and GSH/GSSG ratio in mouse oocytes.The GSX in oocytes at the GV stage (the upper left panel) were measured immediately after oocyte recovery from unstimulated (eCG−) or eCG-primed (eCG+) prepubertal (Prepb) or adult mice. The GSX concentration (the right panel) and GSH/GSSG ratio (the lower left panel) in MII oocytes were observed after in vitro maturation with or without C (cysteamine, 200 µM)/C (cystine, 400 µM) supplementation. Each treatment was repeated 3 times with each replicate containing 35–40 oocytes. a–e: Values without a common letter above their bars differ (P<0.05) within panels.
Mentions: Some GV oocytes were assayed for intra-oocyte GSX immediately after collection, whereas others were matured with or without C/C supplementation before assay for GSX and the GSH/GSSG ratio. In unstimulated mice, intra-oocyte GSX was significantly higher in adult than in prepubertal oocytes at both the GV and MII stage (Fig. 5). When mice were primed with eCG, however, the GSX level of both prepubertal and adult oocytes increased significantly and to the same level. C/C supplementation increased GSX synthesis in both eCG-stimulated and unstimulated oocytes but it could not eliminate the age difference in unstimulated mice. The level of GSH was lower significantly in prepubertal than in adult oocytes (0.36±0.04 vs. 0.69±0.07, P<0.05) while the GSSG content was similar between the two age groups (1.97±0.02 vs. 1.96±0.03, P>0.05). As a result, the GSH/GSSG ratio was significantly higher in adult than prepubertal oocytes when mice were not primed with eCG (Fig. 5). However, eCG eliminated the age difference in the GSH/GSSG ratio.

Bottom Line: Although oocytes from prepubertal animals are found less competent than oocytes from adults, the underlying mechanisms are poorly understood.Whereas reactive oxygen species (ROS) levels increased, Ca(2+) storage decreased significantly in prepubertal oocytes.Maternal eCG priming improved all the parameters and eliminated the age difference.

View Article: PubMed Central - PubMed

Affiliation: College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai-an City, People's Republic of China.

ABSTRACT
Although oocytes from prepubertal animals are found less competent than oocytes from adults, the underlying mechanisms are poorly understood. Using the mouse oocyte model, this paper has tested the hypothesis that the developmental potential of prepubertal oocytes is compromised due mainly to their impaired potential for glutathione synthesis. Oocytes from prepubertal and adult mice, primed with or without eCG, were matured in vitro and assessed for glutathione synthesis potential, oxidative stress, Ca(2+) reserves, fertilization and in vitro development potential. In unprimed mice, abilities for glutathione synthesis, activation, male pronuclear formation, blastocyst formation, cortical granule migration and polyspermic block were all compromised significantly in prepubertal compared to adult oocytes. Cysteamine and cystine supplementation to maturation medium significantly promoted oocyte glutathione synthesis and blastocyst development but difference due to maternal age remained. Whereas reactive oxygen species (ROS) levels increased, Ca(2+) storage decreased significantly in prepubertal oocytes. Levels of both catalytic and modifier subunits of the γ-glutamylcysteine ligase were significantly lower in prepubertal than in adult oocytes. Maternal eCG priming improved all the parameters and eliminated the age difference. Together, the results have confirmed our hypothesis by showing that prepubertal oocytes have a decreased ability to synthesize glutathione leading to an impaired potential to reduce ROS and to form male pronuclei and blastocysts. The resulting oxidative stress decreases the intracellular Ca(2+) store resulting in impaired activation at fertilization, and damages the microfilament network, which affects cortical granule redistribution leading to polyspermy.

Show MeSH
Related in: MedlinePlus