Effects of human serum supplementation on fertilization and development of mouse embryos

Serum is generally used as a protein supplement in culture media for human in vitro fertilization (IVF). To determine the effects of serum supplementation on the development of preimplantation embryos, one-cell and two-cell mouse embryos fertilized in vitro and in vivo were cultured in BWW medium supplemented with preovulatory patient serum (PS), human fetal cord serum (HCS), or bovine serum albumin (BSA). The rates of fertilization and development of embryos fertilized in vitro and in vivo were suppressed when the embryos were cultured with PS or HCS as compared with BSA. In the medium supplemented with HCS, growth of in vitro fertilized embryos was retarded at an earlier embryonic stage than was the case with embryos fertilized in vivo. These results suggest that the in vitro fertilized embryo culture model is more sensitive to culture conditions than is the in vivo fertilized embryo culture model. Incorporations of [3H]uridine and [3H]leucine were measured using embryos that developed to the blastocyst stage in a medium supplemented with HCS or BSA. Blastocysts cultured with HCS showed significantly higher incorporations of [3H]uridine and [3H]leucine than those cultured with BSA. While serum supplementation in culture media has adverse effects on embryo cleavage, it augments synthesis of RNA and protein.