Is serum-soluble vascular endothelial growth factor receptor-1 of importance in unexplained infertility?

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.

Case-control study.

University Central Hospital, a tertiary referral center.

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.

Enzyme-linked immunosorbent assay was used for this study.

Concentrations of VEGF and sVEGFR-1 in the natural cycles and of sVEGFR-1 during a subsequent IVF cycle.

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.

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.