Objective: To analyze the role of vascular endothelial growth factor (VEGF) and its naturally occurring circulating antagonist, soluble VEGF receptor-1 (sVEGFR-1), in infertility. VEGF is a key angiogenic factor in the endometrial and ovarian cyclic processes that are crucial for fertility and sVEGFR-1 impairs its function and fertility in animals - less is known as regards human fertility.
Design: Case-control study.
Setting: University Central Hospital, a tertiary referral center.
Population: Women with unexplained infertility (n=15) and fertile controls (n=10) had serial blood samples collected during their natural cycles, and the infertile women during a subsequent in vitro fertilization (IVF) cycle.
Methods: Enzyme-linked immunosorbent assay was used for this study.
Main outcome measures: Concentrations of VEGF and sVEGFR-1 in the natural cycles and of sVEGFR-1 during a subsequent IVF cycle.
Results: Plasma VEGF concentrations showed no cyclicity in fertile women, but were higher in the infertile group at the midluteal phase. Serum sVEGFR-1 concentrations were similar between the groups and between natural and IVF cycles. However, in infertile women, concentrations of sVEGFR-1 increased from the follicular phase to the luteal phase. In the follicular phase infertile women had a high ratio of VEGF/sVEGFR-1, which was decreased in the luteal phase. Both findings were associated with failure to achieve pregnancy in subsequent IVF cycles.
Conclusions: One cause of unexplained infertility may be unbalanced secretion of sVEGFR-1 with concomitant changes in free VEGF during the transition from the follicular to the luteal phase. This aberration may be related to impaired implantation.