Piezo-actuated zona-drilling improves the fertilisation of ops vitrified mouse oocytes

The present study was designed to investigate fertilisation of open pulled straw (OPS) vitrified mouse oocytes drilled with piezo-micromanipulation method and their subsequent in vitro and in vivo developmental capacity. Ovulated mouse oocytes were vitrified using the OPS method. After warming, the zona pellucida of a group of vitrified-warmed oocytes was drilled by piezo-micro-manipulation. Groups of (a) vitrified, (b) vitrified/drilled and (c) fresh control oocytes were fertilised in vitro . The fertilisation rate of vitrified-warmed oocytes was significantly lower than that of fresh oocytes (45.0 ± 12.6% vs. 85.2 ± 6.8%, P < 0.05), and was significantly improved by zona-drilling (85.4 ± 7.3%). However, blastocyst formation rates of the vitrified and vitrified/drilled groups were significantly lower than those of the fresh controls (65.7 ± 7.0% and 66.4 ± 2.5% vs. 86.6 ± 4.3%, respectively, P < 0.05). The cell number of blastocysts from the vitrified/drilled or the vitrified group was not different from...