Fertilization and early embryology: Effect of different co-culture systems in early human embryo development

The objective of this study was to examine the effects of differentculture systems on the development of early human embryos invitro. A total of 460 fertilized oocytes from 82 cycles of patientswere transferred into one of four systems: (1) into dropletsof Ham's F10 medium+12% normal human serum (NHS); (2) co-culturedon a human granulosa monolayer; (3) co-cultured with bovineoviductal epithelial cells (BOEC); or (4) co-cultured with bovineuterine epithelial cells (BUEC). The percentage of deavage andthe morphological appearance of embryos were recorded dailyfor 72 h in each system using an inverted phase-contrast microscope.The results showed that the proportions of the fertilized oocyteswhich developed to the four-cell stage 48 h after retrievalwere, by culture system: (1) 70% (84/120); (2) 74% (85/115);(3) 78% (91/117); and (4) 76% (82/108). At 72 h after retrieval,the proportions of the eight-cell stage were, by culture system:(1) 45% (38/84); (2) 62% (53/85); (3) 75% (68/91); and (4) 70%(57/82). We conduded that a higher proportion of fertilizedoocytes developed to embryos at the eight-cell stage in systems2, 3 and 4 than in system 1. This indicates the beneficial effectof co-culture of human embryos with granulosa cell, BOEC andBUEC monolayers, which may be due to various factors.