Infertility results in the inability of a female to become pregnant or the female's loss of a pregnancy due to miscarriage. Infertility may be caused by a defective corpus luteum (CL), which can be attributed, in part, to incomplete vascularization (angiogenesis) of the CL, causing a decrease in progesterone production. The angiogenic process is regulated by proangiogenic factors including vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1), and fibroblast growth factor 2 (FGF-2) that are expressed at different times during the luteal phase. Leptin, a potent satiety hormone that influences the gene expression of some of these angiogenic hormones in non-ovarian tissue has been identified in the porcine CL. Therefore, it is hypothesized that leptin will regulate the production of VEGF, Ang-1, and FGF-2 in developing luteal tissue. The objectives of the study were to 1.) characterize the relationship between leptin and angiogenic factors in developing CL tissue and 2.) the effect of leptin on VEGF, Ang-1, and FGF-2 gene expression in dispersed luteal tissue. Thirty mature crossbred, porcine females of similar age were randomly allocated to one of five days of CL development (day 3, 4, 5, 6, or 7; n=6/CL day assignment) for luteal tissue collection. Females were checked twice daily for classical, behavioral estrus using an intact male. Day and time of first standing estrus was considered to be day 0 and time 0. On the day of CL tissue collection, blood samples were collected via, jugular venipuncture, for analysis of serum progesterone. Harvested luteal tissue was divided and either snap frozen in liquid nitrogen and analyzed for VEGF, Ang-1, FGF-2, and leptin expression, or enzymatically digested and dispersed for cell culture. Cells were cultured with leptin (10^-12, 10^-11, 10^-10, 10^-9, 10^-8 and 0M; n=3 wells/dose/female) for 24 hours at 37°C in an atmosphere of 5% CO₂ in air with 95% humidity. Upon termination of culture, cells were analyzed for VEGF, Ang-1, and FGF-2 mRNA using real-time RT-PCR. Values obtained from culture treatments are expressed as a percentage of 0M (0M = 100%). Effect of CL day on VEGF, Ang-1, FGF-2 and leptin in tissue was analyzed using the MIXED procedure of SAS. The effect of leptin on angiogenic factor production in cell culture was analyzed using the MIXED procedure of SAS. The ESTIMATE procedure of SAS was used to determine the differences between culture dose means. Leptin expression in tissue tended to increase (P=0.1) as the CL developed. Leptin treatment dose dependently decreased (P=0.02) VEGF in day 5 cells. In day 6 and 7 cell cultures, leptin decreased (P≤0.02) VEGF, Ang-1 and FGF-2 by 10, 16.8, and 17%, respectively. Therefore, leptin is likely involved in the angiogenic process in a developing porcine CL.

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