Differential Effect of Follicle-Stimulating Hormone and Estradiol on Expressions of Vascular Endothelial Growth Factor (VEGF) 120, VEGF164 and Their Receptors in Bovine Granulosa Cells

Abstract

Abstract. Vascular endothelial growth factor (VEGF) isoforms (VEGF 120 and VEGF 164) secreted by granulosa cells are involved in thecal angiogenesis during follicular development in the bovine ovary. However, whether the transcript of the VEGF120 and VEGF164 isoforms differs during follicular development in the ovary is still unknown. We first examined the gene expression of VEGF120, VEGF164, fms-like tyrosine kinase (Flt-1), and fetal liver kinase (Flk-1) in the granulosa cells (GCs) and theca cells (TCs) of pre-selection and post-selection follicles (PRF and POF respectively) from the bovine ovary. Then we examined the effects of FSH and estradiol (E2) on these factors in cultured bovine GCs. Messenger RNA (mRNA) expression was quantified using real-time PCR methods. The concentrations of E2 and P4 in the follicular fluid (FF) of the PRF and POF were estimated using an enzyme immunoassay (EIA). The concentrations of E2 and P4 in the FF were significantly higher in the POF than in the PRF. The ratio of E2/P4 in PRF and POF was 0.37 and 3.8, respectively. The expression levels of the VEGF120, VEGF164, and Flk-1 mRNAs in the GCs of POF with high E2 concentration were higher than those of PRF. The levels of the Flt-1 and Flk-1 mRNAs in the TCs were not different between PRF and POF. Since E2 in the FF of the POF used in the present study was high compared with the PRF, we examined the effects of E2 and FSH on the expression of the above genes using cultured GCs. Expression of VEGF120 mRNA was induced by a low concentration (1 ng/ml) of E2, whereas the levels of VEGF164 and Flk-1 mRNAs were not affected by E2. FSH stimulated the expression of the VEGF isoforms and Flk-1 genes. Moreover, the expression of those genes was enhanced when low E2 (1 ng/ml) was added to FSH. In conclusion, our data indicates that the VEGF isoforms have a follicle stage-dependent expression pattern. Thus, our results suggest that the expression of VEGF isoforms may be associated with characterization of the preovulatory phenotype during follicle development in the bovine ovary.

Expression of vascular endothelial growth factor and hypoxia-inducible factor-1 alpha during the periovulatory period in goats

“…Exogenous hCG injection in this study might have upregulated VEGF mRNA expression. These data agree with similar observations by several investigators (22)(23)(24) that gonadotropins during the periovulatory period and CL formation regulate VEGF expression. Although other studies have shown VEGF expression by both theca and granulosa layers, we found significant increase only in the thecal layers.…”

“…Goats were randomly assigned for ovarian tissue collection at 0, 4,8,12,24, and 48 h after hormone injections. Ovaries were placed in ice-cold buffered saline solution and transported to the laboratory less than 30 min after collection.…”

Importance of Methionine Metabolism in Morula-to-blastocyst Transition in Bovine Preimplantation Embryos

“…The primers for TEAD4 were the same as those described by Fujii et al [21]. The β-actin (ACTB) transcript was used as an internal control, and the primer sequences were those described by Shimizu et al [22]. All the primer pairs span exon-exon boundaries.…”

Role of Vascular Endothelial Growth Factor on Ovarian Function in Bovine

“…Follicles with high expression of VEGFR-2 exhibit low incidences of apoptosis while, the blockage of receptor inhibits the ability of cells to respond to VEGF endogenously or exogenously present and reduces protection against apoptosis (Greenaway et al, 2004). (Shimizu and Miyamoto, 2007) and is capable of inducing angiogenesis (Schnaper et al, 1996). Estrogen binds with specific estrogen response element present in VEGF gene and thus upregulates VEGF expression (Hyder et al, 2000) in bovine granulosa cells (Garrido et al, 1993).…”

“…However, VEGF isoforms are differently expressed by the hormone. Estrogen causes upregulation of VEGF 164 expression while downregulates VEGF 120 expression in bovine granulosa cells (Shimizu & Miyamoto 2007). …”