Vascular Endothelial Growth Factor mRNA Isoforms 120 and 164 are Differentially Regulated Prior to Ovulation

Vascular Endothelial Growth Factor (VEGF) is produced by cells surrounding the egg in the follicle prior to ovulation. If VEGF is inhibited, ovulation does not occur. The VEGF gene can be spliced to produce different protein isoforms which have specific functions. Our objective was to determine if VEGF 120 and 164 mRNA isoforms are differentially regulated in the preovulatory follicle. From our studies, VEGF isoforms are differentially regulated during both CL regression and after a simulated LH surge. Differences observed in VEGF isoform regulation may allow for manipulation of ovulation in the beef cow

Vascular Endothelial Growth Factor mRNA Isoforms 120 and 164 are Differentially Regulated Prior to Ovulation

Vascular Endothelial Growth Factor (VEGF) is produced by cells surrounding the egg in the follicle prior to ovulation. If VEGF is inhibited, ovulation does not occur. The VEGF gene can be spliced to produce different protein isoforms which have specific functions. Our objective was to determine if VEGF 120 and 164 mRNA isoforms are differentially regulated in the preovulatory follicle. From our studies, VEGF isoforms are differentially regulated during both CL regression and after a simulated LH surge. Differences observed in VEGF isoform regulation may allow for manipulation of ovulation in the beef cow

Vascular Endothelial Growth Factor (VEGF) Isoforms may Regulate Sex-Specific Vascular Development, Cord Formation and Follicle Progression in Developing Gonads

The ratio of VEGF angiogenic to anti-angiogenic isoforms appears to determine different biological functions in reproduction. Reduced amounts of angiogenic VEGF isoforms inhibit testis sex-specific vasculature and normal cord formation in organ cultures while reduction of inhibitory isoforms increased vasculature and perturbed cords. In the female, using peri-natal ovarian cultures, inhibition of angiogenic VEGFisoforms reduced vascular development and inhibited follicle progression while conversely reductions in inhibitory isoforms or increases in angiogenic isoforms enhanced follicle development. Thus, regulation of the Vegfa gene to produce angiogenic or anti-angiogenic isoforms may be a mechanism to alter sex-specific vascular development, formation of seminiferous cords, and/or follicle progression within mammalian gonads

Vascular Endothelial Growth Factor Inhibitory Isoform Is Regulated Prior to Ovulation

VEGF normally acts to stimulate vascular development (angiogenesis) and is necessary for ovulation of the dominant follicle. The inhibitory isoform blocks the actions of VEGF angiogenic isoforms; therefore, the objectives of the experiments were to identify the bovine inhibitory isoform, VEGF164b and to determine its expression prior to and after the LH surge. VEGF164b mRNA was upregulated prior to but did not change after the LH surge. Therefore, VEGF164b may be necessary for preparation of the dominant follicle prior to ovulation

Progestin Concentrations Alter Follicle Characteristics and May Affect Quality of Oocytes (Eggs)

Cows were treated with two progestin concentrations to develop ovulatory follicles exposed to different hormone environments. Cows were assigned to Control Group receiving a CIDR for 7 days (4-6 ng/ml of progestin), or to MGA-14 Group receiving 5mg/head/day of MGA for 14 days (\u3c 1 ng of progestin). Our hypothesis was that the MGA-14 treatment would develop larger, persistent follicles with less granulosa cells per follicle volume and may have altered gene expression profiles in oocytes and granulosa cells. Cows in the MGA-14 treatment had larger follicles and less granulosa cells per volume than controls, suggesting that their development mimicked persistent follicles and may be of poorer quality