The use of recombinant growth factors to promote human embryo development in serum-free medium.

Research into human implantation requires embryo culture systems that yield high numbers of good quality blastocysts. One approach is to use co-culture but the presence of feeder cells and serum may confound analysis of paracrine or autocrine factors involving blastocyst implantation. An alternative approach is to produce a defined serum-free culture medium supplemented with growth factors. We have shown that the addition of Leukaemia Inhibitory Factor increased blastocyst formation from 18.4-43.6% but none of these embryos developed beyond day 7 or hatched, suggesting that additional factors are required. Development to the blastocyst stage was significantly increased to 71.0% in the presence of 100 nM heparin-binding epidermal growth factor (HB-EGF) and 81.0% of these embryos went on to hatch. No difference in blastocyst quality between the control and HB-EGF-treated embryos was found. These experiments clearly demonstrate the potential of this system to generate blastocysts in vitro. Further investigation of the normality of these blastocysts must be carried out before they are used clinically, since it has been demonstrated in other species that apparent improvements in culture conditions may be detrimental to pregnancy outcome.