Cryoprotectants up regulate the expression of mouse oocyte AQP7 which facilitates water diffusion during cryopreservation

Capsule:
Dimethylsulfoxide may up-regulate AQP7 expression in mouse oocytes by both osmolarity-dependent and osmolarity-independent pathways, and up-regulation of AQP7 facilitates water diffusion in mouse oocytes.

Authors:
Ya-Jing Tan, M.Sci., Yun Xiong, B.Sci., Guo-Lian Ding, Ph.D., M.D., Dan Zhang, Ph.D., M.D., Ye Meng, M.D., He-Feng Huang, M.D., Jian-Zhong Sheng, Ph.D., M.D.

Volume 99, Issue 5, Pages 1428-1435, April 2013

Abstract:

Objective:
To investigate the effects of cryoprotectants on the expression of AQP7 in oocytes.

Design:
Experimental animal study.

Setting:
University-based research laboratory.

Animal(s):
Adult C57BL/6J mice.

Intervention(s):
In metaphase II (MII) oocytes obtained from adult female C57BL/6J mice and from donations by fertile women, the mouse oocytes were treated with human tubal fluid medium containing 8% ethylene glycol (EG), 9.5% dimethylsulfoxide (DMSO), and 0.5 M sucrose, respectively; 293T cells transfected with GFP-hAQP7 expression vector were treated with the same solutions.

Main outcome measures:
AQP7 expression in oocytes examined by reverse-transcriptase-nested polymerase chain reaction and immunofluorescence, changes in the volume of mouse oocytes treated with different solutions calculated to determine their permeability to water, and survival rates of vitrified oocytes.

Results:
AQP7 is expressed in human and mouse oocytes. Cryoprotectants, including EG, DMSO, and sucrose, up-regulated AQP7 expression in mouse oocytes and 293T cells transfected with GFP-hAQP7 expression vector. Compared with other cryoprotectants, DMSO stimulated higher expression of AQP7, and this was associated with faster cell volume recovery and lower survival rates of vitrified oocytes.

Conclusion:
DMSO up-regulates AQP7 expression in mouse oocytes more than EG. This may facilitate water diffusion and reduce the time for oocytes to reach osmotic balance with cryoprotectant solution during cryopreservation.

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