TRANSFORMING GROWTH-FACTOR-BETA AND BASIC FIBROBLAST GROWTH-FACTOR SYNERGISTICALLY PROMOTE EARLY BOVINE EMBRYO DEVELOPMENT DURING THE 4TH CELL-CYCLE

Developmentally competent bovine blastocysts were produced by adding transforming growth factor beta (TGFbeta) and basic fibroblast growth factor (bFGF) to serum-free cultures of in vitro produced, 2-cell bovine embryos. The effects of TGFbeta were evaluated because this growth factor signals synthesis and secretion of the extracellular matrix component fibronectin and its receptor. Previous investigations have demonstrated that fibronectin promotes early bovine embryo development in vitro. The effects of TGFbeta can be potentiated by bFGF; bFGF itself is an effector of protein synthesis and a potent mitogen. A positive interaction between the 2 growth factors resulted in 38.8% of fertilized oocytes maturing beyond the 16-cell stage; of these, 24.6% formed blastocysts. Transfer of early blastocysts produced using serum-free medium supplemented with growth factors resulted in pregnancy in 3 of 9 recipients. These results support the hypothesis that TGFbeta and bFGF act synergistically to promote development of bovine embryos beyond the "8-cell block" observed in vitro.