Aberrant fetal growth and development after in vitro culture of sheep zygotes

The effects of in vitro culture systems for sheep zygotes on subsequent fet al growth and development to day 61 and day 125 of gestation were studied. Zygotes recovered from superovulated Scottish Blackface ewes approximately 36 h after intrauterine insemination using semen from a single Suffolk sire were cultured for 5 days in (a) a granulosa cell co-culture system (co-cul ture); Cb) synthetic oviductal fluid medium without serum (SOF-); and (c) s ynthetic oviductal fluid medium supplemented with human serum (SOF+). Contr ol embryos were recovered from superovulated donor ewes at day 6 after oest rus. Embryos were transferred at day 6 to synchronous Scottish Blackface re cipient ewes. In total, 146 gravid uteri were recovered, comprising 97 at d ay 61 (20 co-culture, 27 SOF-, 25 SOF+ and 25 control) and 49 at day 125 (1 3 co-culture, 8 SOF-, 6 SOF+ and 22 control) of gestation. Fetuses derived from co-cultured embryos were 14% heavier (P < 0.01) by day 61 of gestation than those derived from control embryos. Growth coefficients derived from the linear allometric equation log(e)y = log(e)a + b log(e)x (where y = org an mass; x = fetal mass) were significantly greater (P < 0.05) for liver, h eart, kidneys and plantaris muscle in fetuses derived from co-cultured embr yos, and for liver in fetuses derived from SOF+ embryos than those for cont rol fetuses. Fetuses derived from co-cultured embryos were 34% heavier (P < 0.001) and fetuses derived from SOF+ embryos were 18% heavier (P < 0.01) b y day 125 of gestation than those derived from control embryos. Growth coef ficients for liver and heart for fetuses derived from co-culture and SOF+ e mbryos were also significantly greater (P < 0.05) at this stage of gestatio n than those for control group fetuses. Ln contrast, allometric coefficient s for these organs in fetuses derived from embryos cultured in SOF without serum supplementation were not different from those for controls. Excessive volumes of amniotic fluid (polyhydramnios) were observed in 23% of concept uses derived from co-cultured embryos. In vitro embryo culture can signific antly influence fetal growth and this study provides quantitative evidence of major shifts in the patterns of organ and tissue development.