Vascular endothelial growth factor (VEGF) and placental growth factor (PLGF) directly correlate with ovarian follicle size in women undergoing in vitro fertilization (IVF)

Abstract

To assess VEGF and PlGF concentrations in FF from women undergoing IVF, stratified according to follicle size, and to correlate these with VEGF and PlGF mRNA expression in corresponding luteinized granulosa cells (GC), as a follow-up of our previous demonstration that these genes are expressed in GC(1). Prospective sample collection for in vitro studies. 18 consenting subjects with normal ovarian function (IVF being undertaken due to male factor) were recruited prior to oocyte retrieval (mean age of the women = 31 years). Only blood-free FF obtained with the first puncture of each ovary was collected, without the use of flushing media to avoid dilution of the FF contents. All specimens were categorized and analyzed as FF derived from small follicles (8-14 mm diameter) or large follicles (>14 mm diameter). VEGF and PlGF concentrations in the FF were measured using validated commercial ELISAs (RayBio®). Levels of FF estradiol (E2) and progesterone (P4) were determined by RIA. VEGF and PlGF mRNA expression was evaluated by real time RT-PCR, using cultured GC derived from the small and large follicles as indicated above. We also evaluated the expression of other relevant ovarian genes. FF VEGF concentrations from large follicles were markedly higher (6788 ± 2863 pg/ml) compared to those in small follicles (1942 ± 879 pg/ml, p = 0.0003). PlGF concentrations in FF from large follicles also was higher (2004 ± 816 pg/ml) than in small follicles (1144 ± 898 pg/ml, p =0.002). By RT-PCR, the expression of VEGF mRNA was ∼2.5 fold greater in GC from large follicles than from small follicles. However, we observed no significant statistical differences in PlGF mRNA expression relative to follicle size. As expected, expression of mRNAs encoding steroidogenic acute regulatory protein (StAR), anti-mullerian hormone (AMH) and aromatase P450 (CYP19) were all increased in cells from large follicles as compared with those from small follicles. VEGF and PlGF protein concentrations in FF are correlated with follicle size; this relationship also applied to E2 concentration and StAR, AMH and CYP19 expression. Moreover, VEGF and PlGF levels were significantly higher in FF than in matched serum. Similar trends were noted for VEGF mRNA, but not PlGF mRNA expression from cultured GC. We conclude that local VEGF and PlGF gene expression are likely to mediate ovarian follicle angiogenesis and may contribute to oocyte development, maturation and selection of dominant follicle.