Division of Developmental Biology, The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Roslin BioCentre, Roslin, Midlothian EH25 9PS, Scotland, UK.
Domest Anim Endocrinol. 2010 Apr;38(3):127-37. doi: 10.1016/j.domaniend.2009.08.008. Epub 2009 Sep 30.
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.
卵泡选择与颗粒细胞中血管内皮生长因子 (VEGF) 及其受体表达增加有关，然而，VEGF 在调节这些或卵巢中其他非内皮细胞功能中的作用尚未在详细探索。本研究使用牛细胞培养物来研究 VEGF 在调节卵泡发育过程中颗粒细胞功能中的潜在作用。从形态上健康的 4 至 8 毫米或 9 至 14 毫米直径的卵泡（分别对应于牛卵泡波中优势建立之前和之后的直径）中获得颗粒细胞，并暴露于一系列 VEGF 浓度（1 至 100ng/ml），包含牛优势卵泡中天然存在的浓度。1ng/ml 的 VEGF 浓度诱导 4-8mm 卵泡颗粒细胞的显著增殖（P=0.024），并增加了这些细胞对卵泡刺激素（FSH）的增殖反应（P=0.045）；而较高剂量的 VEGF 对增殖没有影响（P=0.9）。VEGF 处理诱导总体 ERK1/2 磷酸化增加（P=0.02）。相比之下，VEGF 单独或与 FSH 联合使用对 4-8mm 卵泡颗粒细胞中类固醇生成酶 CYP11A1 的表达没有影响（P=0.9）。9-14mm 卵泡的颗粒细胞对 1ng/ml 的 VEGF 反应是增加排卵相关基因 PTGS2 的表达（P=0.003），但较高剂量的 VEGF 没有影响（P=0.9）。1ng/ml VEGF 对 PTGS2 的反应与黄体生成素（LH）诱导的反应相似。有趣的是，LH 对 9-14mm 卵泡颗粒细胞 ERK1/2 磷酸化（P=0.003）和 PTGS2 表达（P<0.01）的刺激作用被 VEGFR2 特异性化学抑制（P=0.2）所消除。这些结果表明 VEGF 和其受体 VEGFR2 在介导和/或增强促性腺激素在颗粒细胞中的作用方面具有新的和重要的作用。
