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

Abstract

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.