Improvement in blastocyst hatching of mouse embryos cocultured with human placental cells.

PURPOSE

Although the hatching of embryos is an important phenomenon, the mechanism of hatching remains controversial. Therefore, we attempted to develop a new coculture system with human placental cells to investigate the hatching of mouse embryos.

RESULTS

In our new system there was no difference in development from the two-cell stage to blastocysts between embryos cultured with a T6 medium and embryos cocultured with human placental cells at 1 x 10(5), 5 x 10(5), and 1 x 10(6) cells/ml. However, the hatching-rate cell number increased significantly in embryos cocultured with placental cells compared to embryos cultured without placental cells. [3H]Thymidine uptake did not show any significant difference from the beginning of in vitro culture to the hatching stage between the coculture group and the control group. Nevertheless, the [3H]uridine uptake was significantly different in the two groups, measuring 2167 +/- 532 cpm/10 embryos in the coculture group and 804 +/- 86 cpm/10 embryos in the control group at 114 hr after human chorionic gonadotropin injection (P < 0.01).

CONCLUSION

These results therefore seem to indicate that the hatching of blastocysts depends on the protein synthesis of the embryos and not on DNA duplications.