Human Reproduction Unit, General University Hospital, Albacete, Spain.
Indian J Med Res. 2013 Feb;137(2):331-8.
BACKGROUND & OBJECTIVES: The major cause of fertilisation failure after ICSI is failure of the oocyte to initiate the biochemical processes necessary for activation. This inability could be ascribed to cytoplasmic immaturity of those gametes even if they had reached nuclear maturity. The activation of a mature oocyte is characterised by release from metaphase II (MII) arrest and extrusion of the second polar body, followed by pro-nuclear formation. The aim of this study was to evaluate the fate of in vitro matured (IVM) metaphase I (MI) oocytes subjected to intracytoplasmic sperm injection (ICSI) at different time intervals after extrusion of the first polar body (1PB) in in vitro fertilization (IVF) cycles.
A total of 8030 oocytes were collected from 1400 ICSI cycles, 5504 MII at the time of cumulus retrieval. Four hundred eight metaphase II (MII) (27.1%) matured to MII after in vitro culture for 2-26 h and 5389 sibling MII in the moment of oocyte denudation were injected. On the other hand, 49 ICSI cycles containing only MI oocytes at retrieval were injected at three different time intervals after reaching the MII. The intervals were as follows: 2-6 h (n=10), 8-11 h (n=4) and 23-26 h (n=10). Fertilization and development potential were evaluated in both studies.
Fertilization, embryo cleavage and quality were significantly lower in IVM MI compared to MII at time of denudation. Pregnancy rate was higher in group MII. Pregnancy was achieved in three embryo transfers when ICSI was performed within 2-6 h (group I) and 8-11 h (group II) after PB extrusion. One pregnancy was obtained in group I and a healthy neonate was born.
INTERPRETATION & CONCLUSIONS: Immature oocytes from women whose ovaries have been stimulated could be matured, fertilized by ICSI, cleaved in vitro and to give rise to a live birth. However, the developmental competence of embryos derived from immature oocytes is reduced, compared with sibling in vivo matured oocytes. Further, human IVM oocytes need between 2-6h after the 1PB extrusion to complete its maturation.
卵母细胞受精失败的主要原因是卵母细胞无法启动受精所必需的生化过程。这种无能可能归因于这些配子的细胞质不成熟，即使它们已经达到核成熟。成熟卵母细胞的激活特征是从中期 II（MII）阻滞中释放出来，并排出第二极体，随后形成原核。本研究旨在评估在体外受精（IVF）周期中，第一极体（1PB）排出后不同时间点进行胞质内精子注射（ICSI）对体外成熟（IVM）中期 I（MI）卵母细胞的命运的影响。
从 1400 个 ICSI 周期中收集了 8030 个卵母细胞，其中 5504 个在卵丘取回时处于 MII 期。408 个 MII（27.1%）在体外培养 2-26 小时后成熟为 MII，同时对 5389 个同胞 MII 进行了注射。另一方面，在取回时仅含有 MI 卵母细胞的 49 个 ICSI 周期在达到 MII 后分三个不同时间间隔进行了注射。间隔如下：2-6 小时（n=10）、8-11 小时（n=4）和 23-26 小时（n=10）。在这两项研究中都评估了受精和发育潜能。
与卵丘剥脱时的 MII 相比，IVM MI 的受精率、胚胎分裂和质量明显较低。MII 组的妊娠率较高。在 PB 排出后 2-6 小时（I 组）和 8-11 小时（II 组）进行 ICSI 时，妊娠率分别为 3 次胚胎移植。I 组获得一次妊娠，并分娩了一名健康新生儿。
来自卵巢刺激女性的不成熟卵母细胞可以通过 ICSI 成熟、受精、体外分裂并产生活产。然而，与体内成熟的同胞卵母细胞相比，来源于不成熟卵母细胞的胚胎发育能力降低。此外，人 IVM 卵母细胞在 1PB 排出后需要 2-6 小时才能完成成熟。
