Oocytes evaluation and in-vitro fertilization/intra cytoplasmic sperm injection outcomes

Panminerva Med. 2023 Jun;65(2):179-187. doi: 10.23736/S0031-0808.23.04838-3. Epub 2023 Apr 27.

Abstract

The identification of markers capable of evaluating oocyte quality, its maturation, function, and embryo progression and implantation potential has frequently initiated research interest. However, to date, univocal criteria of oocyte competence do not exist. A major cause of low oocyte quality is evidently advanced maternal age. However, other factors may influence oocyte competence. Among these are obesity, lifestyle factors, genetic and systematic pathologies, ovarian stimulation protocols, laboratory procedures, culture, and environmental conditions. The morphological and maturational evaluation of oocytes is probably the most widely used. Several morphological features, both cytoplasmic (cytoplasmic pattern and hue, presence of vacuoles, refractile bodies, granulation, and smooth endoplasmic reticulum clusters) and extra-cytoplasmic (perivitelline space, zona pellucida thickness, oocyte shape, and polar bodies), have been proposed to distinguish oocytes with the best reproductive potential among a cohort. No single abnormality seems to be sufficiently predictive of the developmental capacity of the oocyte. Some abnormalities such as cumulus cells dysmorphisms, central granulation, vacuoles, and smooth endoplasmic reticulum clusters, however, seem to be associated with poor developmental potential of the embryo, although oocyte dysmorphisms are very common and the data in the literature is limited and provide conflicting views. Other criteria involving gene expression of cumulus cells as well as the metabolomic analysis of spent culture media have been explored. Also, sophisticated technologies such as polar bodies biopsy, meiotic spindle visualization, mitochondrial activity, oxygen consumption, and measurement of glucose-6-phosphate dehydrogenase activity have been proposed. Many of these approaches, however, remain largely research-based and have not found widespread application in clinical service. Due to the lack of consistent data for the assessment of oocyte quality and competence, probably oocyte morphology and oocyte maturity remain important indicators to determine oocyte quality. The aim of this review was to provide spherical attributes and evidence on recent and present research on the topic by analyzing the current methods for evaluation of the oocyte quality, and the impact of oocyte quality on reproductive outcomes. Additionally, current limitations of oocyte quality evaluation are highlighted and insights on future research are provided to optimize the selection techniques of oocytes to improve ART outcomes.

Publication types

  • Review

MeSH terms

  • Animals
  • Fertilization
  • Fertilization in Vitro
  • Male
  • Oocytes* / metabolism
  • Semen*
  • Spermatozoa