Primate model of metaphase I oocyte in vitro maturation and the effects of a novel glutathione donor on maturation, fertilization, and blastocyst development

Abstract

Objective: To assess the effect of glutathione ethyl ester (GSH-OEt) on the development of macaque metaphase (MI) oocytes as a model for human MI oocyte in vitro maturation (IVM).

Design: Prospective cohort study.

Setting: Nonhuman primate assisted reproductive technology program.

Animal(s): Twenty-three Macaca fascicularis females aged 6.5-12.5 years.

Intervention(s): Ovarian stimulation and maturation of MI oocytes in [1] human tubal fluid (HTF), [2] mCMRL-1066, [3] mCMRL-1066+GSH-OEt 3 mM, or [4] mCMRL-1066+GSH-OEt 5 mM. Oocytes were assessed for maturation after 4-6 hours (early) and 18-20 hours (late) of culture. Mature oocytes were inseminated or subjected to glutathione (GSH) assay. Zygotes were cultured to the blastocyst stage for total differential cell counts.

Main outcome measure(s): Oocyte maturation rate, GSH content, pronuclear formation and blastocyst development, and cell number were compared between IVM treatment groups and sibling in vivo matured (IVO) MII oocytes.

Result(s): Compared with HTF, mCMRL-1066 supported higher rates of normal fertilization and blastocyst development in early but not late maturing MI-MII oocytes. Five micromoles of GSH-OEt significantly increased blastocyst total cell and inner cell mass cell number in early MI-MII oocytes compared with IVO and IVM controls. GSH-OEt significantly increased oocyte GSH content and fertilization in late maturing oocytes but not blastocyst development.

Conclusion(s): GSH-OEt positively affects the development of early and late maturing IVM oocytes.

Figure 1

Metaphase II (MII) oocyte intracellular glutathione content (GSH; pmol/oocyte) level of Macaca fascicularis MI oocytes in vitro matured for 18-20 h. Comparison of HTF (n=12), mCMRL-1066 (n=40) and mCMRL-1066 medium supplemented with 3 mM and 5mM glutathione ethyl ester (GSH-OEt; n=47 and 44 respectively). Data are expressed as mean ± s.e.m. for oocyte GSH content (5-12 replicates). IVO; GSH content of in vivo derived germinal vesicle stage (GV; n=32), metaphase I (MI; n=35) and metaphase II (MII; n=44) oocytes at time of collection (5-7 replicates). Bars with different letters are significantly different (p < 0.05). Data analyzed using ANOVA and post-hoc Tukey test.