Structural and morphologic differences in human oocytes after in vitro maturation compared with standard in vitro fertilization

Abstract

Objectives: To study whether the size and texture of oocytes/zygotes differ between in vitro maturation (IVM) and traditional IVF and to determine whether these affect the rate of fertilization and blastocyst development.

Design: Prospective case-control study.

Setting: Fertility clinic.

Patient(s): The study involved 83 participants/cycles of IVF with intracytoplasmic sperm injection (ICSI) or IVM treatment.

Intervention(s): Participants were allocated to the following groups: patients with and without polycystic ovary syndrome (PCOS) undergoing ICSI (PCOS-ICSI and Control-ICSI), and patients with PCOS undergoing IVM (PCOS-IVM). All oocytes were cultured in an Embryoscope incubator.

Main outcome measure(s): Oocyte/zygote sizes were recorded and texture parameters of the ooplasm were analyzed using ImageJ and maZda software. Measurements were recorded at five developmental stages: sperm injection, second polar body extrusion, the first pronuclei appearance, pronuclei disappearance, and immediately before cytokinesis.

Result(s): Normally fertilized PCOS-IVM oocytes were significantly larger at the sperm injection and second polar body extrusion stages, compared with both the PCOS-ICSI and Control-ICSI groups. The PCOS-IVM oocytes were significantly larger at the pronuclei disappearance stage compared with the Control-ICSI group. Oocyte texture parameters were significantly different from both other treatment groups in the early developmental stages, although these were predominantly seen when compared with the Control-ICSI group. There were no significant differences in size or texture by the final stage of immediately before cytokinesis between any of the treatment groups.

Conclusion(s): This study suggests that oocyte size and texture differ in the early stages of the first cell cycle.

Keywords: ICSI; IVM; PCOS; oocyte; texture.