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Updated: Dec 24, 2025
Single Cell Collection of Trophoblast Cells in Peri-implantation Stage Human Embryos
Published on: June 12, 2020
Removing the zona pellucida can decrease cytoplasmic fragmentations in human embryos: a pilot study using 3PN embryos
Keitaro Yumoto1, Toko Shimura1, Yasuyuki Mio2
1Reproductive Centre, Mio Fertility Clinic, 2-1-1, Kuzumo-Minami, Yonago, Tottori, 683-0008, Japan.
Purpose:
The aim of this study was to establish a new method of decreasing cytoplasmic fragmentation in early-stage human embryos.
Methods:
The zona pellucida (ZP) of abnormally-fertilized oocytes (zygotes with three pronuclei (3PN)), which were donated by patients, was removed at the pronuclear stage. ZP-free embryos were observed in a time-lapse imaging and culturing system in order to examine developmental morphology and embryonic quality.
Results:
Based on a modification of Veeck's criteria, 47 of 69 ZP-free 3PN embryos (68.1%) showed fragmentation of less than 20% of the total volume of cytoplasm at the first cleavage (grades 1 and 2), 17 (24.6%) showed 20-40% cytoplasmic fragments (grade 3), and only 5 (7.2%) showed more than 40% fragments (grade 4). These results suggest that the rate of fragmentation is decreased by ZP removal before the first cleavage, compared with normal (ZP-intact) 3PN and 2-pronuclear/2-polar body embryos.
Conclusions:
This study revealed that the ZP is not always necessary for normal development after the pronuclear stage because the ZP-free embryos studied herein developed normally, maintained their cell adhesion well, and showed a decreased rate of fragmentation. This innovative culture system might provide the major breakthrough needed for patients who have difficulty obtaining good-quality embryos.
