Department of Obstetrics and Gynaecology, McGill University, Montreal, Quebec, Canada.
Biol Reprod. 2013 Apr 25;88(4):104. doi: 10.1095/biolreprod.112.107433. Print 2013 Apr.
Oocyte cryopreservation is important for assisted reproductive technologies (ART). Although cryopreservation of metaphase II (MII) oocytes has been successfully used, MII oocytes are vulnerable to the damage inflicted by the freezing procedure. Cryopreservation of germinal vesicle stage oocytes (GV-oocytes) is an alternative choice; however, blastocyst development from GV-oocytes is limited largely due to the need for in vitro maturation (IVM). Herein, we evaluated the effects of l-carnitine (LC) supplementation during vitrification and thawing of mouse GV-oocytes, IVM, and embryo culture on preimplantation development after in vitro fertilization (IVF). We first compared the rate of embryonic development from the oocytes that had been collected at the GV stage from three mouse strains, (B6.DBA)F1, (B6.C3H)F1, and B6, and processed for IVM and IVF, as well as that from the oocytes matured in vivo, i.e. ovulated (IVO). Our results demonstrated that the rate of blastocyst development was the highest in the (B6.DBA)F1 strain and the lowest in the B6 strain. We then supplemented the IVM medium with 0.6 mg/ml LC. The rate of blastocyst development improved in the B6 but not in the (B6.DBA)F1 strain. Vitrification of GV-oocytes in the basic medium alone reduced the rate of blastocyst development in both of those mouse strains. LC supplementation to the IVM medium alone did not change the percentage of blastocyst development. However, LC supplementation to both vitrification and IVM media significantly improved blastocyst development to the levels comparable with those obtained from vitrified/thawed IVO oocytes in both of the (B6.DBA)F1 and B6 strains. We conclude that LC supplementation during vitrification is particularly efficient in improving the preimplantation development from the GV-oocytes that otherwise have lower developmental competence in culture.
卵母细胞冷冻保存对于辅助生殖技术（ART）非常重要。尽管中期 II （MII）卵母细胞的冷冻保存已成功应用，但 MII 卵母细胞易受到冷冻程序造成的损伤。生发泡期卵母细胞（GV 卵母细胞）的冷冻保存是另一种选择；然而，GV 卵母细胞的囊胚发育受到限制，主要是因为需要体外成熟（IVM）。在此，我们评估了在玻璃化和解冻过程中补充左旋肉碱（LC）对小鼠 GV 卵母细胞的体外成熟、胚胎培养以及体外受精（IVF）后胚胎植入前发育的影响。我们首先比较了从三种小鼠品系（B6.DBA）F1、（B6.C3H）F1 和 B6 的 GV 期收集的卵母细胞在进行 IVM 和 IVF 后胚胎发育的比率，以及体内成熟（即排卵）的卵母细胞（IVO）。结果表明，（B6.DBA）F1 品系的囊胚发育率最高，B6 品系的囊胚发育率最低。然后，我们在 IVM 培养基中补充 0.6mg/ml 的 LC。B6 中的囊胚发育率提高，但（B6.DBA）F1 品系则没有。单独用基础培养基玻璃化 GV 卵母细胞降低了这两种品系的囊胚发育率。单独在 IVM 培养基中补充 LC 并没有改变囊胚发育的百分比。然而，LC 同时补充到玻璃化和 IVM 培养基中显著提高了囊胚发育率，使其达到与（B6.DBA）F1 和 B6 品系的玻璃化/解冻 IVO 卵母细胞相当的水平。我们得出结论，在玻璃化过程中补充 LC 特别有效地提高了培养中发育能力较低的 GV 卵母细胞的植入前发育。
