Vascular endothelial growth factor (VEGF) production by the monkey corpus luteum during the menstrual cycle: Isoform-selective messenger RNA expression in vivo and hypoxia-regulated protein secretion in vitro

Experiments were designed to investigate the expression and regulation of vascular endothelial growth factor (VEGF) in the primate corpus luteum (CL) throughout the luteal life span in the natural menstrual cycle. Corpora lutea were collected during the early (ECL; Days 3-5 post-LH surge), mid (MCL; Day 6-8 post-LH surge), mid-late (MLCL; Days 10-12 post-LH surge), late (LCL; Days 14-16 post-LH surge), and very late (Days 17-18 post-LH surge) luteal phase. Specific primers were designed to amplify mRNAs encoding VEGF isoforms 206, 189, 183, 165, 145, and 121. Only two cDNA products were obtained by reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends; cloning and sequencing confirmed their 98% homology to the corresponding human VEGF 165 and 121 sequences. Semiquantitative RT-PCR assays indicated that VEGF 165 mRNA levels increased (P < 0.05) from ECL to MLCL but then declined (P < 0.05) by LCL. Although VEGF 121 mRNA levels were limited in ECL, they increased significantly in MCL (P < 0.05). Levels of VEGF protein, as measured by Western blot analysis, were two- to fourfold higher for VEGF 165 versus VEGF 121. Also, VEGF 165 levels were higher (P < 0.05) in ECL and MCL compared to those at later stages. During 2-day culture, preparations of dispersed luteal cells secreted VEGF into the media; the highest levels were observed in ECL and declined (P < 0.05) by LCL. Regardless of luteal stage, hypoxic conditions increased (P < 0.05) VEGF levels, whereas LH exposure increased (P < 0.05) progesterone, but not VEGF, in the media. These results are consistent with a dynamic, local regulation of VEGF production during the life span of the primate CL that is not directly controlled by LH.