The effect of protein on preimplantation mouse embryo development in vitro

The effects of supplementing culture medium with protein for the culture of mouse embryos from two cells to blastocysts were examined in vitro. The proportion of embryos developing was affected by the type of protein and concentration. The highest rates were obtained in protein-free medium, fetal calf serum, and A Grade bovine serum albumin at all concentrations tested (2-16 mg/ml). Reduced rates of embryo development were observed in proteins of human origin, particularly at the highest concentrations tested. Purification of human and bovine serum albumin resulted in a marked reduction of embryo development. Significantly more normal fetuses were found in pregnant mice receiving transferred embryos grown in protein free-medium than in medium containing fetal calf serum. It is concluded that protein supplementation of culture medium may adversely affect embryo development and viability. These observations could have important implications for human in vitro fertilization.