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Vitrification negatively affects the Ca2+-releasing and activation potential of mouse oocytes, but vitrified oocytes are potentially useful for diagnostic purposes

Journal Contribution - Journal Article

Research question: To what extent does vitrification affect the Ca2+-releasing and activation potential of mouse oocytes, which are commonly used to determine the oocyte activation potential of human spermatozoa? Design: The effect of mouse oocyte vitrification on Ca2+ dynamics and developmental competence after oocyte activation was assessed and compared with fresh mouse oocytes. Moreover, the Ca2+ store content of the endoplasmic reticulum was determined at different time points during the vitrification–warming procedure. Finally, the Ca2+ pattern induced by cryoprotectant exposure was determined. Results: After human sperm injection into mouse oocytes, Ca2+ dynamics but not fertilization rates were significantly altered by vitrification warming (P < 0.05). Ca2+ dynamics in response to SrCl2 or ionomycin were also altered by oocyte vitrification. In contrast, activation and blastocyst rates after SrCl2 exposure were not affected (P > 0.05), whereas activation rates after ionomycin exposure were significantly lower in vitrified–warmed oocytes (P < 0.05); blastocyst rates were not affected (P > 0.05). Cryoprotectant exposure was associated with a strong drop in endoplasmic reticulum Ca2+ store content. Oocytes rapidly recovered during warming and recovery in Ca2+-containing media; a threshold area under the curve of Ca2+ dynamics to obtain activation rates above 90% was determined. Conclusions: Vitrified–warmed mouse oocytes display reduced Ca2+-releasing potential upon oocyte activation, caused by cryoprotectant exposure. With adapted classification criteria, these oocytes could be used for diagnosing oocyte activation deficiencies in patients. Evaluating the Ca2+-signalling machinery in vitrified–warmed human oocytes is required.
Journal: REPRODUCTIVE BIOMEDICINE ONLINE
ISSN: 1472-6491
Issue: 1
Volume: 40
Pages: 13 - 25
Publication year:2020
Accessibility:Closed