The effect of serum fractions on single-cell mouse embryos in vitro

To examine the effect of various fractions of human fetal cord serum (HCS) on mouse embryos cultured in vitro, heat-inactivated HCS was separated by ultrafiltration into five distinct fractions: Fractions A, MW>30,000; B, MW 30,000–10,000; C, MW 10,000–5000; D, MW 5000–1000; and E, MW <1000. Seven hundred twentyeight single-cell embryos were cultured in TYH- 280 medium supplemented with 8 mg/ml bovine serum albumin (BSA) and a 20% concentration of Fraction A, B, C, D, or E, whole HCS, or BSA alone. Embryos cultured with Fraction A or E or whole HCS demonstrated a significantly reduced growth rate (P<0.01), while embryos cultured with Fraction D demonstrated a significantly increased growth rate (P<0.01). Additionally, 649 singlecell embryos were cultured in medium which was supplemented with 8 mg BSA/ml and a 0, 1,2, or 5% concentration of Fraction A or E. Fraction E displayed toxicity even at a 1% concentration (P< 0.07), while Fraction A demonstrated growth inhibition at a 5% concentration (P <0.05) but increased the hatching rate at a 1% concentration (P < 0.01). Finally, 635 single-cell embryos were cultured with four distinct fractions of HCS obtained from a Sephacryl S-200 column: Fractions I, MW 100,000; II, MW 70,000–100,000; III, MW 30,000–70,000; and IV, low molecular weight (<5000). Fraction I or III significantly reduced the embryo growth rate as seen with Fraction A (P<0.01) and Fraction II significantly increased only the hatching rate (P<0.01), while Fraction IV significantly increased the growth rate as seen with Fraction D. In conclusion, HCS contains embryo growth inhibitory properties in the high (>30,000) and low (<1000) molecular weight components, while growth promoting factors are found in the 1000–5000 MW fraction. It also seems that there are some factors in the 70,000–100,000 MW fraction which may promote the ability of the embryo to hatch.Presented in part at the American Fertility Society meeting, March 1985.