Effects of culture medium and maturation time on in-vitro development of bovine oocytes into blastocysts

Abstract

The central role of the oviduct, as the site of zona pellucida (ZP) maturation, fertilization and early embryogenesis, has been recognized. The objective of this study was to investigate whether ampullary and isthmic derived epithelial cells have different effects on in vitro ZP hardening, in vitro fertilization (IVF) and in vitro culture (IVC) of the resulting embryos. Cumulus oocyte complexes (COCs) were matured in a coculture system with ampullary/isthmic epithelial cells, TCM199 supplemented with insulin-like growth factor I (IGF-I) and epithelial derived growth factor (EGF) (GF treated group), conditioned media produced using ampullary (ACM), isthmic (ICM), COCs + ampullary, and COCs + isthmic epithelial cells, contactless culture system, oviductal fluid, GF + ACM/ICM, and drops of TCM199 (control), for 24 h. The matured oocytes were randomly divided into two groups: Group I was subjected to ZP digestion; Group II underwent IVF. The duration of the ZP digestion, in a coculture system with ampullary epithelial cells (AE) was significantly increased (p < 0.05), compared with other groups. Penetrated oocytes and monospermic fertilization were significantly increased (p < 0.05) in the AE group. The mean number of spermatozoa per penetrated oocyte was reduced dramatically for the AE group (p < 0.05). A significant increase (p < 0.05) in the embryo development was observed in all treated groups, compared to the control. Results revealed that epithelial cells harvested from the ampullary segment of the oviduct had in vitro specialized role in ZP hardening and have subsequent IVF and IVC outcomes.