IMPROVE NUTRIENT MANAGEMENT AND EFFICIENCY IN CATTLE
Location: Nutrition Research
Title: Anti-angiogenic VEGFA164B isoform mRNA is more abundant in E2-inactive, atretic follicles while expression of angiogenic VEGFA isoforms is greater in granulosa cells from developing bovine follicles prior to the LH surge
| Mcfee, Renee - |
| Artac, Robin - |
| Pohlmeier, William - |
| Kerl, Jill - |
| Brauer, Vanessa - |
| Cupp, Andrea - |
Submitted to: Biology of Reproduction Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 21, 2011
Publication Date: July 30, 2011
Citation: Mcfee, R., Artac, R., Pohlmeier, W., Kerl, J., Brauer, V., Cushman, R., Cupp, A. 2011. Anti-angiogenic VEGFA164B isoform mRNA is more abundant in E2-inactive, atretic follicles while expression of angiogenic VEGFA isoforms is greater in granulosa cells from developing bovine follicles prior to the LH surge [abstract]. Biology of Reproduction. 85 (1 Supplement):205 (Abstract # 668).
Vascular endothelial growth factor A (VEGFA) is expressed by granulosa cells of the follicle and if its actions are blocked, ovulation and antral follicle development is inhibited. However, the role of anti-angiogenic VEGFA isoforms in bovine dominant follicle development, especially prior to and after the LH surge, has not been determined. We amplified and sequenced the predominant anti-angiogenic isoform, VEGFA_164B, from bovine granulosa cells. The bovine VEGFA_164B mRNA sequence was 90% homologous to human VEGFA_165B. We then conducted 3 experiments to evaluate expression of VEGFA isoforms in granulosa cells from dominant follicles at different stages of the estrous cycle and different health statuses. In trial one, cows were given two injections of prostaglandin F2a (PG) 14 days apart, while in the second trial, cows were administered gonadotropin-releasing hormone (GnRH) 48 hours after the second PG injection to induce an LH surge. In both trials 1 and 2, aspirates were obtained from dominant follicles at different time points and follicular fluid was assayed for estrogen (E2) and progesterone to determine the estrogenic status of all follicles. Prior to the LH surge, mRNA levels for VEGFA_164B were lowest 48 h after the last PG injection (P < 0.009), while mRNA levels for anti-Müllerian hormone (AMH) increased between 24 h and 48 h post-PG (P < 0.05). After an induced LH surge, VEGFA_164B mRNA levels decreased from 0 h to 18 h post-GnRH (P < 0.02). The VEGFA_164:164B ratio and mRNA levels for the angiogenic VEGFA isoforms (VEGFA_120 and VEGFA_164) were greater (P < 0.02) in granulosa cells prior to the LH surge compared to granulosa cells after a surge in LH. However, there was no difference in mRNA levels for VEGFA_164B in granulosa cells prior to and after the LH surge. To further evaluate the role of VEGFA in follicular development, a third trial was conducted where cows were either synchronized with a modified Co-Synch protocol (CIDR) or treated with a synthetic progestin, melengesterol acetate (MGA), for 14 days with lysis of the corpus luteum, to develop persistent follicles. Dominant follicles were aspirated at 38 ± 3 h after the final PG injection. Analysis of the interaction between treatment group and E2 activity revealed that mRNA levels for VEGFA_164B and AMH in granulosa cells were greater (P < 0.04) in E2-inactive follicles from cows treated with MGA compared to CIDR E2-inactive follicles and E2-active follicles from both treatment groups. In addition, mRNA levels for AMH were more abundant (P < 0.04) in granulosa cells obtained from MGA-treated cows than CIDR cows. Messenger RNA levels for VEGFA_164B, AMH, and CART prepropeptide (CARTPT) were all more abundant in granulosa cells from E2-inactive follicles compared to E2-active follicles (P < 0.05). Furthermore, expression of VEGFA_164B mRNA was positively correlated with the expression of AMH, CARTPT, and BCL2 (P < 0.004). Therefore, expression of angiogenic VEGFA isoforms was more abundant in developing dominant follicles prior to the LH surge and expression of the anti-angiogenic VEGFA isoform, VEGFA_164B, was more abundant in E2-inactive follicles. Thus, expression of different VEGFA isoforms may indicate the developmental and health status of bovine follicles.
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