Fertilization rate would be improved after vitrification of immature mouse oocytes

Yasaman Abbasi,1 Rouhollah fathi,2,* Farzaneh baniasadi,3 Samira hajiaghalou,4

1. Department of Cellular and Molecular Biology, University of Science and Culture, ACECR, Tehran, Iran.
2. Department of Embryology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR
3. Department of Embryology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR
4. Department of Embryology, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR

Abstract

Introduction

Vitrification of oocyte is a promising technique to preserve fertility in different species, but it has deleterious effect on oocyte quality and causes the production of low-quality embryos. as a result, it is essential to optimize vitrification protocols to increase developmental rate of embryo.

Methods

This study was conducted in vitrification and control groups using immature oocytes, derived from 6-8 weeks-old nmri mice. immature oocytes were vitrified by two-step vitrification protocol. first oocytes were exposed to equilibration medium (7.5%eg plus 7.5%dmso (v/v) in base medium) for 5 minutes, then they were washed in vitrification solution (15%dmso, 15%eg, 0.5 mol/l sucrose in base medium) for less than 1 minute and quickly loaded on cryotop and plunged directly into liquid nitrogen and stored at - 1960 c trough 3-5 days. warming was carried out by three-step procedure: samples were warmed in w1 (1.0 mol/l sucrose in base medium) for 1 min at 370c, w2 (0.5 mol/l sucrose in base medium) for 3 mins and w3 (0.25 mol/l sucrose in base medium) for 3 mins at room temperature separately. subsequent ivm of immature oocytes (gv) and ivf of obtained mature oocytes were done after warming in order to achieve 2pn embryos. viability and maturation were respectively measured by trypan blue and hoechst staining in control and vitrification groups.

Results

The viability rate of vitrified immature oocytes did not have a significant fluctuation (average= 77.40%). after warming, there was a significant difference in ivm rate of obtained mature oocytes (mii) from vitrification (85.60%) and control (83.80%) groups. in addition, the rate of in vitro fertilization increased interestingly after vitrification (62.91% vs. 76.67%; p<0.05).

Conclusion

An appropriate vitrification protocol doesn’t disrupt the maturation of mouse immature oocytes and may improve the fertilization rate.

Keywords

Mouse oocyte, vitrification, in vitro maturation, fertilization.