Effect of Vero cell coculture on the development of frozen-thawed two-cellmouse embryos

Purpose: Our purpose was to evaluate the beneficial effects of long-term co culture of Vera cells on the development of frozen-thawed two-cell mouse em bryos. Methods: Two-cell mouse embryos were frozen slowly with 1,2-propandiol and sucrose as cryoprotectants and thawed rapidly, followed by stepwise dilutio n. Vero cells were cultured in drops of RPMI 1640 to establish monolayers. Frozen-thawed embryos were cultured alone (control) or cocultured with Vero cells. The rate of development in bath groups was compared. Results: After 4 days of culture, significantly more embryos in coculture w ere developed to expanded blastocysts (61 vs 37% for controls; P less than or equal to 0.0001). In addition, on the fifth day of cultivation, more emb ryos in coculture showed the potential of hatching from the zona pellucida (26 vs 7% in controls; P I 0.0001). The rate of degeneration in coculture w as also much lower than in controls (6 and 15. respectively). Conclusions: Coculture of cryopreserved preimplantation-stage embryos with Vero cells seems to be a useful cool to eliminate the postthaw deleterious effect of freezing and also to obtain better-quality embryos appropriate fo r transfer.