# AQP7 Protects Vitrified Sheep GV-Stage Oocyte Maturation via Mitochondrial Activity

## TL;DR

AQP7 helps protect sheep oocytes during freezing by maintaining mitochondrial function and preventing damage.

## Contribution

AQP7 is shown to be essential for protecting vitrified sheep oocytes through mitochondrial redox homeostasis.

## Key findings

- AQP7 inhibition increases oocyte damage and reduces embryo formation rates.
- AQP7 knockdown lowers maturation rates, while overexpression partially restores them.
- Mitochondrial antioxidant MitoQ partially rescues oocyte maturation after AQP7 inhibition.

## Abstract

Oocyte vitrification is crucial for improving farm animal reproduction and preserving rare breeds, but it can cause internal damage that reduces their quality. We investigated whether a protein called aquaporin-7 (AQP7) helps protect oocytes during freezing. Our study on sheep oocytes revealed that inhibiting AQP7 significantly increased their susceptibility to damage. This damage was characterized by dysfunction of mitochondria, the cell’s power plants. Consequently, the oocytes matured poorly and had a drastically reduced potential to form embryos. Crucially, adding an antioxidant designed to protect mitochondria could partially reverse these detrimental effects. These findings identify AQP7 as a promising target for refining vitrification protocols, with the goal of enhancing breeding efficiency and safeguarding genetic diversity in sheep.

Oocyte vitrification imposes oxidative stress that compromises maturation competence. Aquaporin-7 (AQP7) has been implicated in cellular redox regulation, but its specific role in cryopreserved oocytes remains unclear. Here, germinal vesicle (GV) stage oocytes were vitrified and warmed with AQP7 inhibitor Z433927330 (0.5, 5, 50 μM). AQP7 inhibition disrupted redox balance, compromised mitochondrial function. Consequently, it severely compromised developmental competence, leading to significantly reduced cleavage (39.90% ± 6.17 vs. 52.93% ± 3.37) and blastocyst formation rates (1.67% ± 2.89 vs. 5.17% ± 2.49) in vitro. To confirm, we performed microinjection-mediated AQP7 knockdown and overexpression and assessed their effects on maturation. AQP7 knockdown further reduced the maturation rate of vitrified oocytes (20.22% ± 3.14 vs. 36.31% ± 2.10), whereas overexpression partially restored it (43.98% ± 4.71 vs. 33.74% ± 2.21). The mitochondrial-targeted antioxidant MitoQ partially rescued the maturation rate (53.13% ± 2.75 vs. 43.52% ± 2.71). Thus, AQP7 is essential for the maturation of vitrified sheep oocytes by safeguarding intracellular redox homeostasis, thereby preventing mitochondrial dysfunction and cytoskeletal damage, and loss of embryonic developmental potential.