Related Experiment Video
Updated: Jul 1, 2025
Morphometric Protocol for the Objective Assessment of Blastocyst Behavior During Vitrification and Warming Steps
Published on: February 28, 2019
External bending of cryodevice during vitrification leads to cryoprotectant cracks and damage to embryo blastomeres
Rongxiang Wang1, Danjun Li2, Leiwen Zhao2
1Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, 639 Zhizaoju Rd, Shanghai 200011, China.; Center for Reproductive Medicine, Shanghai East Hospital, Tongji University School of Medicine, 1800 Yuntai Rd, Shanghai 200120, China.; School of Life Sciences and Technology, Tongji University, 1239 Siping Rd, Shanghai 200092, China.
Research Question:
Embryo blastomeres and the zona pellucida are occasionally damaged during vitrification; is this a result of crack-induced mechanical damage in the glass state, caused by external bending of the device?
Design:
A stereomicroscope was used to observe external bending-induced cracks in a cryoprotectant. Thereafter, 309 human cleavage-stage embryos derived from abnormally fertilized eggs were used to assess embryo damage under two external bending conditions: forward bending and backward bending, with three bending degrees applied. Three distinct embryo positions were used to examine the correlation between bending and embryo damage. Damage was assessed by looking at blastomere lysis rates, and overall rates of damaged and surviving embryos.
Results:
A series of parallel cracks were identified in the cryoprotectant used for external bending, which led to damage to the embryo blastomeres. Compared with forward bending and control, the embryos were found to be more easily damaged by backward bending, indicated by significantly higher blastomere lysis and embryo damage rates, and lower embryo survival rate of backward bending than forward bending (P < 0.001). The degree of embryo damage also increased as the degree of external forces increased. Embryo position correlated with degree of embryo damage.
Conclusions:
Cryoprotectant crack-induced damage was identified as the cause of embryo damage. Mechanical damage to the glass state occurs because of improper external bending of the cryodevice strip in liquid nitrogen during vitrification. To prevent damage, bending of the strip should be avoided and the embryos should be placed near the tip of the strip.
