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This work was supported by The Oncofertility Consortium (NIH U54 RR024347-HD058294, PL1-EB008542), NIH U54-HD18185 (Eunice Kennedy Shriver Specialized Cooperative Centers Program in Reproduction and Infertility Research), NIH ORWH/NICHD 2K12HD043488 (BIRCWH), Oregon National Primate Research Center 8P51OD011092. There are no conflicts of interest.

The role of endothelial cell-specific growth factors in the vascularization of the primate peri-ovulatory follicle was examined. Experiments were designed firstly to detect expression of vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) in granulosa cells and secondly, to determine whether gonadotrophins and/or steroids regulate their expression during the peri-ovulatory interval. Granulosa cells and follicular fluid were collected from rhesus macaques undergoing ovarian stimulation before (0 h), 12, or 36 h after a bolus of ovulatory human chorionic gonadotrophin (HCG), with or without steroid ablation and progestin replacement. VEGF, Ang-1 and Ang-2 mRNA were all detected prior to the ovulatory stimulus. Whereas follicular fluid VEGF concentrations increased 6-fold (P < 0.05) between 0 and 12 h, VEGF mRNA values were unchanged and were unaffected by steroid ablation. Ang-1 mRNA decreased from 0 to 12 h (P < 0.05), followed by a 30-fold increase (P < 0.05) at 36 h, while Ang-2 mRNA values were unchanged between 0, 12 and 36 h. Steroid ablation decreased (P < 0.05) Ang-1 mRNA at 36 h, and Ang-2 mRNA at 12 h, while only Ang-1 was restored by progestin replacement. These data suggest a dynamic expression of vascular-specific growth factors in a gonadotrophin-dependent, steroid-independent (VEGF) or steroid-dependent (Ang-1) manner in granulosa cells of peri-ovulatory follicles of primates.

The midcycle gonadotropin surge promotes vascular endothelial growth factor-A (VEGF-A) production by granulosa cells in the ovulatory follicle, but it is unclear whether primary regulators of VEGF secretion in other tissues, including hypoxia and growth factors, are also important in the ovary. To address these issues, granulosa cells were collected from rhesus monkeys during controlled ovarian stimulation either before (i.e., nonluteinized granulosa cells, NLGCs) or 27 hours after (i.e., luteinized granulosa cells, LGCs) administration of an ovulatory bolus of hCG, and cultured in fibronectin-coated wells containing a chemically defined media. When NLGCs were transferred to various O2 environments (20%, 5%, or 0% O2) or media containing 100 mM CoCl2, LH (100 ng/ml)-stimulated progesterone (P4) levels were markedly (P < 0.05) suppressed by 0% O2 or CoCl2. VEGF concentrations also declined (P < 0.05) in control, CoCl2, and CoCl2 + LH groups in 0% O2, although CoCl2 modestly increased (75% above control; P < 0.05) VEGF levels in 20% and 5% O2. When NLGCs were cultured in the presence of recombinant human insulin-like growth factor (IGF)-1, IGF-2, or insulin, there was a dose-dependent increase (P < 0.05) in VEGF levels on Day 1 of culture. Whereas optimal doses of IGF-1 or IGF-2 (50 ng/ml), hCG (100 ng/ml), and IGF plus hCG stimulated VEGF levels on Day 1, only the combination of IGF-1 or IGF-2 plus hCG increased VEGF above controls and sustained levels through Day 3 of culture. The synergistic effects of IGF and hCG were also evident in P4 levels, and were not due to changes in DNA content between treatment groups. LGCs produced much higher levels of P4 and VEGF, but the responses to different O2 concentrations and insulin-related factors were qualitatively similar to those of NLGCs. These results suggest that hypoxia is not a primary regulator of VEGF production in primate granulosa cells. However, IGFs may act in concert with the gonadotropin surge to promote VEGF secretion in the ovulatory, luteinizing follicle.