NORMAL OFFSPRING PRODUCED AFTER TRANSFER OF HAMSTER EMBRYOS GROWN FROM 2-CELLS TO 8-CELLS IN A CHEMICALLY-DEFINED CULTURE-MEDIUM

Following identification of the causes of the "two-cell block" to in vitro development, phosphate and glucose, two-cell hamster embryos can now be grown in vitro through at least two cleavage divisions (1). The purpose of this study was to determine whether such embryos are capable of developing into normal offspring. Two-cell hamster embryos (34 to 35 h post egg activation) collected from superovulated females were cultured in 100 μl drops of HECM-1 (1). Following 28 to 31 h culture, eight-cell to morula stage embryos were transferred to recipient females that had been mated to vasectomized males 2 d previously. Each uterine horn received 15 to 20 embryos that were morphologically normal in appearance. Of the 10 transfers attempted, five resulted in pregnancies. Forty-two pups were born from the 178 embryos transferred to these five females (24%), not significantly different from the number born from five successful control transfers ( 35 178, 20%). This result demonstrates that the culture of preimplantation hamster embryos in chemically-defined medium devoid of phosphate and glucose (HECM-1) not only eliminates the two-cell block but also allows the production of normal, viable offspring. This result may have implications for the culture of embryos of other species that show in vitro developmental blocks. © 1990.