Insulin-like growth factors-1 and -2, but not hypoxia, synergize with gonadotropin hormone to promote vascular endothelial growth factor-A secretion by monkey granulosa cells from preovulatory follicles

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.