Effect of fibronectin on early embryo development in cows.

Two-cell bovine embryos produced in vitro were cultured in serum-free medium containing the soluble glycoprotein fibronectin (50 micrograms ml-1) to study the function of the extracellular matrix in early development. Some of the embryos (48/164, 29.3%), developed beyond the 16-cell stage compared with none of the 179 controls. Fibronectin at lower (5 micrograms ml-1) or higher (300 micrograms ml-1) concentrations did not promote embryo development (0/89 and 0/82, respectively). Indirect immunofluorescence demonstrated the presence of both fibronectin and its receptor on the surface of eight-cell embryo blastomeres, and biotinylated fibronectin demonstrated that exogenous fibronectin could cross the zona pellucida. These results, demonstrating the successful culture of bovine embryos in serum-free medium, support the hypothesis that the extracellular matrix, specifically fibronectin, plays a role in early development of bovine embryos.