Effect of encapsulation on development of mouse pronuclear stage embryos in vitro

Pronuclear stage embryos with intact (ZI), slit (ZS) or completely removed (ZF) zona pellucida were encapsulated with an artificial zona pellucida (AZP) made of 1.5% sodium alginate. Embryos were cultured in KSOM medium with or without protein and their development in vitro to the blastocyst stage was recorded. AZP significantly (P < 0.05) improved the development of embryos to the blastocyst stage regardless of the presence of the natural zona pellucida. The encapsulated embryos developed at a higher rate (P < 0.05) in the absence of protein as compared with non-encapsulated embryos. Furthermore, the cell contacts at the 4-cell stage were significantly improved (P < 0.05) with encapsulation. AZP improved (P < 0.05) the development of pronuclear stage embryos with a slit zona pellucida to morula and blastocyst stages as compared with ZS embryos. It is concluded that AZP improves the in vitro development of pronuclear stage embryos with intact or completely removed zona pellucida as well as micromanipulated embryos to the blastocyst stage.