Vascular Endothelial Growth Factor and Kinase Domain Region Receptor Are Involved in Both Seminiferous Cord Formation and Vascular Development During Testis Morphogenesis in the Rat

Morphological male sex determination is dependent on migration of endothelial and preperitubular cells from the adjacent mesonephros into the developing testis. Our hypothesis is that VEGFA and its receptor KDR are necessary for both testicular cord formation and neovascularization. The Vegfa gene has 8 exons with many splice variants. Vegfa120, Vegfa164, and Vegfa188 mRNA isoforms were detected on Embryonic Day (E) 13.5 (plug date = E0) in the rat. Vegfa120, Vegfa144, Vegfa164, Vegfa188, and Vegfa205 mRNA were detected at E18 and Postnatal Day 3 (P3). Kdr mRNA was present on E13.5, whereas Fms-like tyrosine kinase 1 receptor (Flt1) mRNA was not detected until E18. VEGFA protein was localized to Sertoli cells at cord formation and KDR to germ and interstitial cells. The VEGFA signaling inhibitors SU1498 (40 μM) and VEGFR-TKI (8 μM) inhibited cord formation in E13 testis cultures with 90% reduced vascular density (P \u3c 0.01) in VEGFR-TKI-treated organs. Furthermore, Je-11 (10 μM), an antagonist to VEGFA, also perturbed cord formation and inhibited vascular density by more than 50% (P \u3c 0.01). To determine signal transduction pathways involved in VEGFA’s regulation of testis morphogenesis, E13 testis were treated with LY 294002 (15 μM), a phosphoinositide 3-kinase (PI3K) pathway inhibitor, resulting in inhibition of both vascular density (46%) and cord formation. Thus, we support our hypothesis and conclude that VEGFA, secreted by the Sertoli cell, is involved in both neovascularization and cord formation and potentially acts through the PI3K pathway during testis morphogenesis to elicit its effects

Vascular Endothelial Growth Factor and Kinase Domain Region Receptor Are Involved in Both Seminiferous Cord Formation and Vascular Development During Testis Morphogenesis in the Rat

Morphological male sex determination is dependent on migration of endothelial and preperitubular cells from the adjacent mesonephros into the developing testis. Our hypothesis is that VEGFA and its receptor KDR are necessary for both testicular cord formation and neovascularization. The Vegfa gene has 8 exons with many splice variants. Vegfa120, Vegfa164, and Vegfa188 mRNA isoforms were detected on Embryonic Day (E) 13.5 (plug date = E0) in the rat. Vegfa120, Vegfa144, Vegfa164, Vegfa188, and Vegfa205 mRNA were detected at E18 and Postnatal Day 3 (P3). Kdr mRNA was present on E13.5, whereas Fms-like tyrosine kinase 1 receptor (Flt1) mRNA was not detected until E18. VEGFA protein was localized to Sertoli cells at cord formation and KDR to germ and interstitial cells. The VEGFA signaling inhibitors SU1498 (40 μM) and VEGFR-TKI (8 μM) inhibited cord formation in E13 testis cultures with 90% reduced vascular density (P \u3c 0.01) in VEGFR-TKI-treated organs. Furthermore, Je-11 (10 μM), an antagonist to VEGFA, also perturbed cord formation and inhibited vascular density by more than 50% (P \u3c 0.01). To determine signal transduction pathways involved in VEGFA’s regulation of testis morphogenesis, E13 testis were treated with LY 294002 (15 μM), a phosphoinositide 3-kinase (PI3K) pathway inhibitor, resulting in inhibition of both vascular density (46%) and cord formation. Thus, we support our hypothesis and conclude that VEGFA, secreted by the Sertoli cell, is involved in both neovascularization and cord formation and potentially acts through the PI3K pathway during testis morphogenesis to elicit its effects

Inhibition of Vascular Endothelial Growth Factor Manipulates Follicles in Beef Females

Vascular Endothelial Growth Factor (VEGF) is produced by cells surrounding the egg in the follicle. If VEGF is inhibited, ovulation does not occur. Understanding how VEGF regulates follicle development may allow for manipulation of estrous cycles. In previous studies in our laboratory, blocking the actions of VEGF decreased activation of early stage follicles in neonatal rat ovary cultures. Therefore, we hypothesized inhibition of VEGF actions would also inhibit follicle activation in bovine ovarian cortical cultures. Inhibition of VEGF did inhibit follicle progression, thus regulation of VEGF may be a way to manipulate follicle development and more accurately time ovulation

Inhibition of Vascular Endothelial Growth Factor Manipulates Follicles in Beef Females

Vascular Endothelial Growth Factor (VEGF) is produced by cells surrounding the egg in the follicle. If VEGF is inhibited, ovulation does not occur. Understanding how VEGF regulates follicle development may allow for manipulation of estrous cycles. In previous studies in our laboratory, blocking the actions of VEGF decreased activation of early stage follicles in neonatal rat ovary cultures. Therefore, we hypothesized inhibition of VEGF actions would also inhibit follicle activation in bovine ovarian cortical cultures. Inhibition of VEGF did inhibit follicle progression, thus regulation of VEGF may be a way to manipulate follicle development and more accurately time ovulation

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

Reproductive Aging Influences Ovarian Function in Beef Cows

Anti-Müllerian Hormone (AMH) has been associated with follicle number and age of the ovary. Therefore, our hypothesiswas that AMH was a biomarker for both follicle number and ovarian function in the beef cow. Ovaries were collected by flank laparotomy. The number of follicles increased as cows aged from 1.5 to 6 years and began to decrease thereafter; however, the size of the ovary continued to increase with advanced age. Expression of the AMH gene increased with increasing follicle number in 2-year-old beef cows. These results suggest that heifers with larger ovaries will have greater numbers of follicles and greater productivity, allowing them to stay in the production herd longer. AMH could be used to identify heifers of high reproductive potential at a very young age

A Proposed Role for VEGF Isoforms in Sex-Specific Vasculature Development in the Gonad

Many scientists have expended efforts to determine what regulates development of an indifferent gonad into either a testis or ovary. Expression of Sry and upregulation of Sox9 are factors that initiate formation of the testis-specific pathway to allow for both sex-specific vasculature and seminiferous cord formation. Migration of mesonephric precursors of peritubular myoid cells and endothelial cells into the differentiating testis is a critical step in formation of both of these structures. Furthermore, these events appear to be initiated downstream from Sry expression. Sertoli cell secretion of growth factors acts to attract these mesonephric cells. One hypothesis is that a growth factor specific for these cell linages act in concert to coordinate migration of both peritubular and endothelial cells. A second hypothesis is that several growth factors stimulate migration and differentiation of mesonephric “stemlike” cells to result in migration and differentiation into several different cell lineages. While the specific mechanism is unclear, several growth factors have been implicated in the initiation of mesonephric cell migration. This review will focus on the proposed mechanisms of a growth factor, Vascular Endothelial Growth Factor, and how different angiogenic and inhibitory isoforms from this single gene may aid in development of testis-specific vascular development

Effects of Luteinizing Hormone Releasing Hormone Antagonist On The Bovine Corpus Luteum

The size and function of the corpus luteum were examined after administration of luteinizing hormone releasing hormone antagonist. Luteinizing hormone releasing hormone antagonist was administered to three animal groups starting: 1) 2 days before the preovulatory luteinizing hormone surge inducing ovulation; 2) at initiation of the preovulatory surge; and 3) 2 days after the preovulatory surge. Although size and function of the corpus luteum were suppressed in all treated groups, the greatest developmental suppression occurred when luteinizing hormone release was blocked 2 days before the preovulatory surge of LH inducing ovulation. Therefore, optimal pregnancy rates in cattle may depend on pulsatile release of LH during the follicular phase of the estrous cycle in addition to that secreted during and after ovulation

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