VEGF modulates the effects of gonadotropins in granulosa cells

• Published in: Domestic animal endocrinology 2010-04, Vol.38 (3), p.127-137
• Main Authors: Doyle, L.K., Walker, C.A., Donadeu, F.X.
• Format: Article
• Language: English
• Subjects: Animals; Cattle; Cell Proliferation; Cells, Cultured; Cholesterol Side-Chain Cleavage Enzyme - genetics; Cyclooxygenase 2 - genetics; dose response; ERK1/2; extracellular signal-regulated kinase 1/2; Female; follicle diameter; Follicle Stimulating Hormone - metabolism; Follicle Stimulating Hormone - pharmacology; follicle-stimulating hormone; follicular development; gene expression regulation; Gene Expression Regulation - drug effects; gonadotropins; Granulosa; granulosa cells; Granulosa Cells - cytology; Granulosa Cells - drug effects; Granulosa Cells - metabolism; hormonal regulation; luteinizing hormone; Luteinizing Hormone - metabolism; Luteinizing Hormone - pharmacology; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - metabolism; ovarian follicles; Phosphorylation; protein kinases; protein phosphorylation; PTGS2; PTGS2 gene; receptors; Vascular Endothelial Growth Factor A - pharmacology; Vascular Endothelial Growth Factor Receptor-2 - metabolism; vascular endothelial growth factor receptors; vascular endothelial growth factors; VEGF
• ISSN: 0739-7240; 1879-0054
• DOI: 10.1016/j.domaniend.2009.08.008

Follicle selection is associated with an increase in the expression of vascular endothelial growth factor (VEGF) and its receptors in granulosa cells, however, the roles of VEGF in regulating the function of these or other non-endothelial cells in the ovary have not been explored in detail. The current study used bovine cell cultures to investigate potential roles of VEGF in the regulation of granulosa cell function during follicle development. Granulosa cells were obtained from morphologically healthy follicles 4 to 8 mm or 9 to 14 mm in diameter (corresponding to diameters before and after the establishment of dominance, respectively, during a bovine follicular wave) and exposed to a range of VEGF concentrations (1 to 100 ng/mL) encompassing concentrations found naturally in bovine dominant follicles. A concentration of VEGF of 1 ng/mL induced significant proliferation of granulosa cells from 4- to 8-mm follicles ( P = 0.024) and increased the proliferative response of these cells to follicle-stimulating hormone (FSH; P = 0.045); whereas higher doses of VEGF had no effect on proliferation ( P = 0.9). Treatment with VEGF induced an overall increase in mean extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation ( P = 0.02). In contrast, VEGF, alone or in combination with FSH, had no effect on expression of the steroidogenic enzyme, CYP11A1, by cells from 4- to 8-mm follicles ( P = 0.9). Granulosa cells from 9- to 14-mm follicles responded to 1 ng/mL VEGF with an increase in expression of the ovulation-associated gene, PTGS2 ( P = 0.003) but higher VEGF doses had no effect ( P = 0.9). The PTGS2 response to 1 ng/mL VEGF was similar to that induced by treatment with luteinizing hormone (LH). Interestingly, the stimulatory effects of LH on ERK1/2 phosphorylation ( P = 0.003) and PTGS2 expression ( P < 0.01) in granulosa cells from 9- to 14-mm follicles were abolished ( P = 0.2) by specific chemical inhibition of VEGF receptor 2 (VEGFR2). These results suggest novel and important roles of VEGF and its receptor, VEGFR2, in mediating and/or enhancing the effects of gonadotropins in granulosa cells.