Vascular endothelial growth factor messenger ribonucleic acid expression in the primate ovary

Abstract

We studied the distribution of messenger RNA (mRNA) that encodes for vascular endothelial growth factor (VEGF) within the primate ovary by in situ hybridization and Northern analysis to determine if the presence of mRNA for this angiogenic factor is associated with structures within the ovary in which angiogenesis is thought to play a role in development and/or function. In situ hybridization to sections of cynomolgus ovaries with a 35S-labeled antisense RNA probe revealed specific tissue localization within the follicle as well as the corpus luteum, but not stromal tissue. Intense expression of mRNA for VEGF during the late follicular phase was confined to the maturing follicle which, we presume, was destined for ovulation. Hybridization within the corpus luteum exhibited a punctate pattern suggesting that there may be specific cells within the corpus luteum that express mRNA for VEGF. The expression of mRNA for VEGF during the early and late luteal phase of the menstrual cycle was studied by Northern analysis. Messenger RNAs were detectable at approximately 3.7 and 5.0 kb positions in corpora lutea collected during the early luteal phase of the menstrual cycle (days 3-5 postovulation). No hybridization signals were observed with RNA prepared from regressing corpora lutea (1-2 days following the onset of menses). The gonadotropic regulation of the expression of mRNA for VEGF in the corpus luteum was studied by treating monkeys with a potent GnRH antagonist during the midluteal phase of the menstrual cycle. Administration of the antagonist for 1 or 2 days did not alter the expression of mRNA for VEGF in comparison to corresponding controls. However, a 3-day treatment regimen brought about a significant reduction in the levels of mRNA for VEGF (P less than 0.01). These studies demonstrate a development-related expression of mRNA for VEGF in the ovary during the menstrual cycle and are consistent with the hypothesis that VEGF may play important roles in follicle selection and corpus luteum function in primates.