Zona Pellucida Birefringence Research Articles

Zona pellucida birefringence and meiotic spindle visualization as predictors of ICSI outcomes. Preliminary results

OBJECTIVE: This study aimed to evaluate whether zona pellucida (ZP) birefringence and meiotic spindle (MS) presence may predict intracytoplasmic sperm injection (ICSI) outcomes in cycles of oocyte donation. DESIGN: Retrospective cohort study of 43 oocyte donation cycles. MATERIALS AND METHODS: ZP birefringence and presence of MS were assessed by OCTAX PolarAide® software in 471 mature oocytes. A first analysis evaluated fertilization rate and embryo quality. Mature oocytes were divided in 4 groups regarding its ZP score (ZPs) and presence or not of MS: Group 1: positive ZPs and presence of MS (N=120); Group 2: positive ZPs and absence of MS (N=137); Group 3: negative ZPs and presence of MS (N=84); Group 4: negative ZPs and absence of MS (N=130). Regarding pregnancy, implantation and miscarriage rates, a second approach was assessed splitting cycles with embryo replacement (N=42) into 3 groups based on the ZP birefringence of transferred embryos (TE): Group A: all TE derived only from positive ZPs oocytes (N=18); Group B: all TE derived from positive and negative ZPs oocytes (N= 12); Group C: all TE derived only from negative ZPs oocytes (N=12). One-way ANOVA test was used to analyze results. RESULTS: Neither fertilization rate (Group 1: 81,70%, Group 2: 75,90%, Group 3: 66,70%, Group 4: 73,10%) nor percentage of good-quality embryos (Group 1: 65,30%, Group 2: 64,40%, Group 3: 67,30%, Group 4: 65,30%) varied among 4 groups. No statistical differences were found in pregnancy (Group A: 66,60%, Group B: 53,80%, Group C: 43,43%), implantation (Group A: 47,22%, Group B: 45,83. Group C: 43,43%), and miscarriage rates (Group A: 8,30% Group B: 0,00%, Group C: 0,00%). CONCLUSION: Data from this study show that evaluation of oocytes based on ZP imaging and MS observation, do not predict ICSI outcomes in oocyte donation cycles in our center. Further studies in oocytes coming from patients with infertility indications will be conducted in order to establish if this non-invasive technique is useful in this group of patients.

Zona pellucida birefringence in in vivo and in vitro matured oocytes

To evaluate zona pellucida birefringence (ZPB) in immature and mature oocytes collected after controlled ovarian stimulation and to assess the influence of ZPB on oocyte development. Prospective study. Private assisted reproduction centre. Thirty patients undergoing intracytoplasmic sperm injection. The ZPB of mature and immature oocytes was evaluated using a polarization imaging software module, and the oocytes were classified as high birefringence (HB) or low birefringence. The ZPB of in vivo and in vitro matured oocytes and its influence on spontaneous nuclear maturation in vitro, fertilization, and embryo quality. The percentage of HB oocytes was higher in immature than in mature oocytes (40.1 vs. 23.6%). Among immature oocytes, an increased percentage of HB in prophase-I stage oocytes compared to metaphase I stage oocytes was also observed (50.7 vs. 25.0%). However, the percentage of HB oocytes did not change when comparing oocytes before and after in vitro maturation for both prophase I and metaphase I oocytes. No influence of ZPB was observed on the spontaneous in vitro maturation potential. Exclusively for metaphase II retrieved oocytes, a positive influence of ZPB on fertilization (odds ratio [OR], 1.78; 95% confidence interval [CI], 1.27-2.49) and embryo quality (OR, 2.28; 95% CI, 1.04-4.99) was noted. ZPB may be a useful tool to predict embryo quality for metaphase-II oocytes. Moreover, the completion of nuclear changes in the production of metaphase-II oocytes in vitro may not reflect their molecular maturity.

Quantitative analysis of the intensity of zona pellucida birefringence of oocytes during IVF cycles

To determine whether the age of the female patient, oocyte maturation stage, pronuclei, embryonic quality and/or cycle outcome are related to the intensity of the zona pellucida birefringence (ZPB) in oocytes during IVF procedures, a retrospective study was conducted on 214 IVF cycles using a polarisation imaging system. A negative correlation was found between ZPB intensity and the age of female patients (r = -0.44; P < 0.0001). For oocytes at different maturation stages, the ZPB score was higher at the germinal vesicle stage (20.77 ± 1.88) than at MI (10.99 ± 1.35; P < 0.001), and higher at MI than at MII (7.91 ± 0.65; P < 0.05). For the pronuclei (PN) of fertilised oocytes, the ZPB score of oocytes with 3PN was significantly higher than that of oocytes with 1PN or 0PN (7.94 ± 0.78 v. 5.57 ± 1.51 and 4.45 ± 0.85, respectively; P < 0.001). However, there were no differences in ZPB scores between oocytes with 2PN and 3PN. Neither embryo quality on day 3 nor the clinical results could be predicted on the basis of the ZPB score (P > 0.05).

A comparative analysis of the zona pellucida birefringence of fresh and frozen–thawed human embryos

The cryopreservation of human embryos is thought to induce alteration in the glycoprotein matrix and lead to zona change. However, this assumption has been full of controversies till now. The objective of this study was to evaluate the effect of cryopreservation on zona pellucida of human embryos. Fresh (n=106, from 40 patients) and frozen-thawed embryos (n=123, from 40 patients) were obtained from consenting patients who received conventional IVF and ICSI treatment. The birefringence of zona pellucida in human fresh and frozen-thawed embryos was imaged and quantitatively analyzed using polarized light microscopy before embryo transfer. There was no significant difference in retardance and thickness of the zona pellucida multilaminar structure between the two groups. Pregnancy and implantation rates of transferred fresh and frozen-thawed embryos were also compared. No significant difference was found in the rates of clinical pregnancy (47.5 vs 37.5%) and implantation (24.5 vs 23.2%) between the two groups. This study suggests that there is no significant change in the zona pellucida birefringence of human embryos before and after cryopreservation.

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

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.

The zona pellucida birefringence in immature and mature oocytes collected after controlled ovarian stimulation: preliminary results

The zona pellucida birefringence in immature and mature oocytes collected after controlled ovarian stimulation: preliminary results

The prognostic value of automatic scoring of zona pellucida birefringence in correlation with embryo morphology at day 5

OBJECTIVE: The birefringence of inner layer of Zona Pellucida (ZP) was described to be the new prognostic marker to identify the oocyte with the highest developmental potential. The automatic scoring system was developed to evaluate the intensity and homogeneity of ZP birefringence objectively. This non-invasive method was described to correlate with the embryo morphology at day 3 in vitro. Our study assesses the correlation between the ZP score and the embryo morphology at day 5.