Improvement of Human Early Embryo Development in Vitro by Coculture on Monolayers of Vero Cells1

TLDR

Vero epithelial cells, derived from kidney and genital tract embryology, were chosen as a safe, controlled support for embryo culture. Spare embryos deemed unsuitable for freezing were cocultured for five days on a Vero cell monolayer, whereas controls were cultured in medium alone (B2 + 15 % serum). Coculture increased blastocyst formation to 61 % versus 3 % in controls, with many embryos expanding and hatching, indicating that the system rescues early‑degenerating embryos and could extend IVF culture time and improve blastocyst‑stage freezing.

Abstract

Human "spare" embryos, judged unsuitable for freezing because of their poor quality, were cocultured for 5 days on a "Vero" cell layer. These epithelial cells were selected because kidney and genital tract have a common embryologic origin and "Vero" cells are a safe and highly controlled cellular support used for vaccine production. In the control group, the embryos were cultured in culture medium alone (B2 + 15% serum). At the end of the culture, the number of blastocysts was significantly higher in the coculture group: 61% vs. 3%. Moreover, at least half of the blastocysts were expanding and hatching (13/25), with a chronologically normal development. These observations suggest that (1) the coculture system improves human embryonic development; (2) it can rescue early degenerating embryos; (3) beneficial effects of coculture are not strictly genital-tract specific, but rather epithelium dependent. This coculture system could be used for in vitro fertilization to prolong in vitro culture and thus make it possible to transfer embryos at a more appropriate time, to eliminate early-blocked eggs, and to freeze embryos at the blastocyst stage, when freezing procedures are most successful.