Effects of multi-gradient equilibration during vitrification on oocyte survival and embryo development in mice

Vitrification has been widely used for oocyte cryopreservation, but there is still a need for optimization to improve clinical outcomes. In this study, we compared the routine droplet merge protocol with modified multi-gradient equilibration vitrification for cryopreservation of mouse oocytes at met...

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Bibliographic Details
Published in:Zygote (Cambridge) 2023-12, Vol.31 (6), p.612-619
Main Authors: Zhu, Yan, Zhang, Zhen, Zhang, Guang-Li, Jiang, Man-Xi
Format: Article
Language:English
Subjects:
Balancing
Cryopreservation
Droplets
Embryogenesis
Embryonic growth stage
Embryos
Fertilization
Gametocytes
Immunofluorescence
Laboratory animals
Metaphase
Morphology
Nitrogen
Oocytes
Survival
Vitrification
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Summary:Vitrification has been widely used for oocyte cryopreservation, but there is still a need for optimization to improve clinical outcomes. In this study, we compared the routine droplet merge protocol with modified multi-gradient equilibration vitrification for cryopreservation of mouse oocytes at metaphase II. Subsequently, the oocytes were thawed and subjected to intracytoplasmic sperm injection (ICSI). Oocyte survival and spindle status were evaluated by morphology and immunofluorescence staining. Moreover, the fertilization rates and blastocyst development were examined in vitro. The results showed that multi-gradient equilibration vitrification outperformed droplet merge vitrification in terms of oocyte survival, spindle morphology, blastocyst formation, and embryo quality. In contrast, droplet merge vitrification exhibited decreasing survival rates, a reduced proportion of oocytes with normal spindle morphology, and lower blastocyst rates as the number of loaded oocytes increased. Notably, when more than six oocytes were loaded, reduced oocyte survival rates, abnormal oocyte spindle morphology, and poor embryo quality were observed. These findings highlight that the vitrification of mouse metaphase II oocytes by the modified multi-gradient equilibration vitrification has the advantage of maintaining oocyte survival, spindle morphology, and subsequent embryonic development.
ISSN:0967-1994
1469-8730
DOI:10.1017/S0967199423000540