Effect of estrogen on vascular endothelial growth/permeability factor expression by glandular epithelial and stromal cells in the baboon endometrium.

Abstract

The ovarian steroid hormones, estrogen and progesterone, have important roles in establishing the new vascular bed within the endometrium during each menstrual cycle; however, little is known about the mechanisms underlying this process. We recently showed that mRNA and protein levels for the angiogenic factor vascular endothelial growth/permeability factor (VEG/PF) in endometrial glandular epithelial and stromal cells of baboons were decreased to very low levels by ovariectomy, and we proposed that the levels of estrogen and progesterone exhibited during the menstrual cycle regulate endometrial VEG/PF expression in the primate. To test this hypothesis, VEG/PF mRNA levels were determined by reverse transcription-polymerase chain reaction in glandular epithelial and stromal cells isolated by laser-capture microdissection from, and VEG/PF protein was determined by immunocytochemistry in the endometrium of baboons after ovariectomy and chronic administration of estradiol and progesterone in levels designed to replicate the hormonal profiles that are characteristic of the proliferative and secretory phases of the menstrual cycle. Administration of estradiol to ovariectomized baboons in levels that replicated the late-proliferative phase of the menstrual cycle (209 +/- 40 pg/ml serum) increased/restored VEG/PF mRNA to levels in the glands (5.57 +/- 1.53 amol/fmol 18S rRNA, P < 0.01) and stroma (2.61 +/- 1.57 amol/fmol 18S rRNA, P < 0.02) that were approximately 10-fold greater than those observed after ovariectomy alone (0.52 +/- 0.21 and 0.22 +/- 0.11 amol/fmol 18S rRNA, respectively) and were similar to those previously shown in intact baboons. Concomitant administration of estradiol and progesterone to ovariectomized baboons in levels that replicated the midsecretory phase of the menstrual cycle (44 +/- 15 pg/ml serum and 9.8 +/- 2.2 ng/ml serum, respectively) resulted in glandular epithelial (3.65 +/- 1.42 amol/fmol 18S rRNA) and stromal (1.25 +/- 0.77 amol/fmol 18S rRNA) VEG/PF mRNA levels that were not significantly different from those exhibited after ovariectomy or ovariectomy and estradiol treatment. Comparable results were obtained for VEG/PF mRNA expression in whole-endometrial tissue, although the relative 2-fold increase (P < 0.03) in VEG/PF mRNA levels induced by estrogen in mixed endometrial cells of ovariectomized baboons appeared to be less marked than that in isolated glandular epithelial and stromal cells. After ovariectomy, endometrial width (0.98 +/- 0.09 mm) was approximately one-third of that in intact baboons (3.58 +/- 0.32 mm), and endometrial VEG/PF protein expression was low. Estradiol restored endometrial width (3.00 +/- 0.12 mm, P < 0.01) and VEG/PF protein expression to normal. In summary, estrogen has a significant role in regulating and maintaining VEG/PF expression by glandular epithelial and stromal cells of the endometrium during the menstrual cycle.