Evaluation of zona pellucida birefringence intensity during in vitro maturation of oocytes from stimulated cycles

Abstract

BackgroundThis study evaluated whether there is a relationship between the zona pellucida birefringence (ZP-BF) intensity and the nuclear (NM) and cytoplasmic (CM) in vitro maturation of human oocytes from stimulated cycles.ResultsThe ZP-BF was evaluated under an inverted microscope with a polarizing optical system and was scored as high/positive (when the ZP image presented a uniform and intense birefringence) or low/negative (when the image presented moderate and heterogeneous birefringence). CM was analyzed by evaluating the distribution of cortical granules (CGs) throughout the ooplasm by immunofluorescence staining. CM was classified as: complete, when CG was localized in the periphery; incomplete, when oocytes presented a cluster of CGs in the center; or in transition, when oocytes had both in clusters throughout cytoplasm and distributed in a layer in the cytoplasm periphery Nuclear maturation: From a total of 83 germinal vesicle (GV) stage oocytes, 58 of oocytes (69.9%) reached NM at the metaphase II stage. From these 58 oocytes matured in vitro, the high/positively scoring ZP-BF was presented in 82.7% of oocytes at the GV stage, in 75.8% of oocytes when at the metaphase I, and in 82.7% when oocytes reached MII. No relationship was observed between NM and ZP-BF positive/negative scores (P = 0.55). These variables had a low Pearson's correlation coefficient (r = 0.081). Cytoplasmic maturation: A total of 85 in vitro-matured MII oocytes were fixed for CM evaluation. Forty-nine oocytes of them (57.6%) showed the complete CM, 30 (61.2%) presented a high/positively scoring ZP-BF and 19 (38.8%) had a low/negatively scoring ZP-BF. From 36 oocytes (42.3%) with incomplete CM, 18 (50%) presented a high/positively scoring ZPBF and 18 (50%) had a low/negatively scoring ZP-BF. No relationship was observed between CM and ZP-BF positive/negative scores (P = 0.42). These variables had a low Pearson's correlation coefficient (r = 0.11).ConclusionsThe current study demonstrated an absence of relationship between ZP-BF high/positive or low/negative score and nuclear and cytoplasmic in vitro maturation of oocytes from stimulation cycles.

Oocyte Selection for In Vitro Embryo Production in Bovine Species: Noninvasive Approaches for New Challenges of Oocyte Competence

“…In addition, PLM has been used for the evaluation of the ZPB, which in humans has been associated with oocyte quality [116][117][118], although this is still under debate [119,120]. The few studies in cattle showed that a lower ZPB is related to high-quality oocytes and improved blastocyst development [121,122], whereas two studies in horses reported conflicting results, indicating beneficial effects of both low ZPB [123] and high ZPB [124].…”

Analysis of meiotic spindle and zona pellucida birefringenceof IVM oocytes in PCOS patients

“…The ZP is a multilaminar glycoprotein coat that forms during oogenesis (34,35). At the molecular level, the ZP is composed of three layers that are composed of 4 protein filaments, ZP1, ZP2, ZP3, and ZP4 (12). However, the inner layer exhibits maximum birefringence with application of the PolScope (36).…”

“…We hypothesized that the zona with high-order structured fibers might reflect the healthiness of an oocyte and its full oocyte maturation (nuclear and cytoplasmic) (12). In addition, in that study we observed that the percentage of a HB-ZP was significantly higher in the IVM oocytes than in vivo-matured ones, similar to findings reported by Omidi et al According to Braga et al and Petersen et al (12,37), the ZP birefringence is unaffected during IVM, and these findings confirm our results. We also observed that the fertilization rate after sperm injection (62.5%) in IVM oocytes was similar to those reported by earlier authors (39,40).…”

“…The ZP is a unique extracellular coat composed of filaments that are organized in a three-dimensional network structure surrounding maturing oocytes during ovulation and fertilization, up to embryonic development. Currently, software programs are available that automatically analyze the inner layer of ZP birefringence scores, relying on intensity and distribution of the birefringence (5,12). Therefore, the objective of the present study was to compare the MS and ZP birefringences of both in vivo-and in vitro-matured oocytes from PCOS patients undergoing an ICSI program.…”

Oocyte Selection for <em>in vitro</em> embryo Production in Bovine Species: Non-Invasive Approaches for the New Challenges of Oocyte Competence

“…However, the selection of cattle oocytes by the presence of a PLM signal does not seem to offer improvement in IVP outcomes yet. In addition, PLM has been used for the evaluation of the ZPB, which in humans has been associated to oocyte quality [116][117][118], although it is still under debate [119,120]. The few studies in cattle have shown that a lower ZPB is related to high quality oocytes and improved blastocyst development [121,122], whereas two studies in horses have reported conflicting results, indicating beneficial effects of both low ZPB [123] and high ZPB [124].…”