2-Aminoethyl diphenylborinate mitigates damage from the endoplasmic reticulum of vitrified bovine oocyte

Abstract

Intracellular calcium (Ca²⁺) homeostasis is primarily maintained by the endoplasmic reticulum (ER). Fluctuations in intracellular Ca²⁺ concentrations can induce ER stress, ultimately causing cellular apoptosis. Vitrification can increase Ca²⁺ concentrations and reduce oocyte vitality. However, 2-Aminoethyl Diphenylborinate (2-APB), a Ca²⁺ release regulator, can maintain ER calcium homeostasis. In this study, after in vitro maturation, MII oocytes were randomly allocated into 4 group in a 4 groups in a 2 x 2 factorial study (fresh or vitrified and with or without exposure to 2-APB before vitrification). There were fewer ER clusters in the cortical region of oocytes after vitrification in the Control group, but they were protected by pre-treated with 2-APB. In addition, 2-APB significantly increased survival and cleavage of vitrified-warmed parthenogenetically activated blastocysts. Expression of the ER stress proteins GRP78 and CHOP, and the apoptotic proteins caspase-9, caspase-3, and cytochrome c (cytC) were all significantly increased in vitrified oocytes. However, with 2-APB pretreatment, expression of those proteins were not significant different from the Control group. In conclusion, 2-APB effectively alleviated ER stress by maintaining Ca²⁺ homeostasis to mitigate damage in vitrified-warmed bovine oocytes.