Zona pellucida birefringence score and meiotic spindle visualization in relation to embryo development and ICSI outcomes

Abstract

The meiotic spindle and the zona pellucida exhibit molecular order when imaged with polarized optics. This study aimed to investigate possible factors contributing to the zona pellucida birefringence score and meiotic spindle visualization, and to evaluate whether these structures may predict intracytoplasmic sperm injection outcomes. Oocytes were divided into groups according to zona pellucida birefringence and meiotic spindle visualization. In addition, the cycles were split into three groups based on the zona birefringence of transferred embryos. A positive correlation was observed between zona birefringence and meiotic spindle visualization. In addition, when the meiotic spindle was observed, the fertilization rate among oocytes with high or low zona pellucida birefringence was similar. Implantation and pregnancy rates were significantly higher when embryos derived from high birefringence oocytes were exclusively transferred (P = 0.041 and P = 0.004 respectively). Furthermore, the miscarriage rate was higher when embryos derived from low birefringence oocytes were exclusively transferred. On the other hand, the total dose of FSH negatively affected meiotic spindle visualization. Results show that selection of embryos based on zona pellucida and meiotic spindle imaging can significantly improve implantation and pregnancy rates. Moreover, the dose of FSH used for ovarian stimulation may affect the organization of the oocyte meiotic spindle.

Correlation of oocyte morphometry parameters with woman’s age

“…Birefringence of the spindle and the zona of the metaphase II oocyte, as evaluated by polarized light microscopy, have been recently proposed as criteria of quality in live human oocytes [13,23,24]. Several studies have reported a positive correlation between high birefringence of the zona pellucida (HZB) and that of the spindle (SP) in metaphase II oocytes, and the main reproductive indexes such as fertilization, embryo implantation and women's pregnancy rate [14,15].…”

“…New methodologies, including polar body diagnosis (PBD) [9], metabolomics [10], polarization light microscopy [11][12][13][14][15] and pattern recognition of processed images by special algorithms [16], have been proposed as methods to improve the objective selection of good quality oocytes. In particular, the PolScope was used in a semiquantitative mode to evaluate the birefringence of the ZP [17] and the meiotic spindle (SP) of metaphase II oocytes [12].…”

“…OCTAX PolarAIDE™) that automatically calculate the zona birefringence and display in real time objective and user-independent zona scores based on the intensity and distribution of the birefringence [18]. High zona pellucida birefringence (HZB) has been associated with a significantly higher rate of embryo implantation and development to term, as compared with low ZP birefringence (LZB) [14,15]. In addition, oocytes with high fertilization rate show in general a birefringent SP [12,15].…”

“…High zona pellucida birefringence (HZB) has been associated with a significantly higher rate of embryo implantation and development to term, as compared with low ZP birefringence (LZB) [14,15]. In addition, oocytes with high fertilization rate show in general a birefringent SP [12,15]. Thus, there is a broad agreement that the analysis of the birefringence of the oocyte ZP and SP represents a reliable, objective criterion for good quality oocyte selection.…”

The role of morphological evaluation of oocyte and embryo quality in ART programs (a review)

“…У некоторых ооцитов, имеющих первое полярное тельце, может не быть видимого в поляризационном микроскопе веретена деления. Поляризационная микроскопия дает возможность оценки веретена де-ления и позволяет прогнозировать течение процесса оплодотворения и последующего дробления развив-шегося в результате оплодотворения эмбриона [11,12].…”