Submission Number: UKA-4-4-33

Abstract Number: 417

IN SITU LOCALIZATION OF VEGF mRNA DURING LUTEAL FORMATION AND REGRESSION IN THE PIG.

U Boonyaprakob ¹, Zhaoping Ge* ², Vickie S Hedgpeth ², P Routh ¹, John Gadsby* ² and G Almond* ¹

Department of Farm Animal Health and Resource Management, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA. ¹
Department of Anatomy, Physiological Sciences and Radiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA. ²

Abstract:
Vascular endothelial growth factor (VEGF), a specific mitogen of endothelial cells, has been identified as the major regulator of angiogenesis in the corpus luteum (CL). Studies in several species suggest that VEGF production in luteinized granulosa cells and/or pericytes may play a major role in the migration and development of microvasculature in the forming CL. To examine this phenomenon in the pig, in situ hybridization was used to investigate the localization of the mRNA for VEGF in the porcine CL at different stages of the estrous cycle. Gilts (n = 5/day) were ovariectomized on day 4, 7, 10, 13 and 15 (Day 0 = first day of estrus). One to two CLs were collected from each animal, embedded in OCT media and frozen at -80C. The remaining CLs were enzyme-dissociated, and mixed luteal cells were prepared by cytospin to obtain 20,000 large cells per slide, and stored at -80C. In order to identify the localization of VEGF mRNA, sections (8m) of the frozen CL and cytospin slides were hybridized with riboprobes specific for porcine VEGF. In situ hybridization indicated VEGF mRNA expression localized in both small (unidentified) and large (granulosa-lutein) cells, with the most intensive binding observed in the small cell population. In the early luteal phase (day 4), localization of the VEGF mRNA was found at high levels in luteinized granulosa cells and the expression was concentrated encircling the lumen of the ruptured follicle. Although the production of VEGF mRNA was found throughout the estrous cycle, its expression on day 10 and 13 was of relatively lower intensity compared with earlier stages, but appeared to increase intensity again on day 15. Collectively, these results provide compelling evidence for VEGF gene expression by porcine luteal cells in vivo. We conclude that several luteal cell sub-populations express VEGF mRNA, suggesting a role for this growth factor in luteal angiogenesis.

Keywords: VEGF, CL, porcine, angiogenesis

This abstract is being presented at: 3:00 PM in session:
SESSION 14: CORPUS LUTEUM II