Vascular endothelial growth factor level changes during human embryo development in culture medium

Objective. Implantation is a complex phenomenon consisting of the first strong contact between embryo and endometrium. Recent studies have demonstrated that this process is dependent not only on the 'readiness' of the endometrium, but also on complex interactions between endometrial and embryonic tissues that cross-talk by means of different molecules (growth factors, cytokines, vasoactive factors). Investigations performed on human blastocysts indicate a role for vascular endothelial growth factor (VEGF) in these processes. The aim of the present study was to investigate VEGF levels at different stages in human embryo culture medium. Study design. We selected 20 women among patients undergoing assisted reproduction with the in vitro fertilization-blastocyst transfer protocol. The oocytes were inseminated by intracytoplasmic sperm injection. For each patient, approximately two cultures of four microinjected oocytes (and then of four embryos) were performed. Each culture of four oocytes embryos was placed in one dish to increase the probability to detect small VEGF concentrations. Results. Results showed significantly higher VEGF levels in the medium at blastocyst stage (12.16 ± 2.80 pg ml) compared with embryos at pronuclear stage (13.58 ± 2.32 pg ml) and microinjected oocytes (12.80 ± 3.45 pg ml). Conclusions. An important VEGF synthesis by blastocysts occurs during human embryo development.