Steroid control of growth factor gene expression in the rat uterus: The role of vascular endothelial growth/permeability factor in the regulation of estrogen-induced increases in uterine vascular permeability and growth

Abstract

In the uterus, estrogen from the ovary stimulates microvascular permeability and edema, followed by proliferation of both epithelial cells and cells of the richly vascular stroma. These responses can be mimicked in an ovariectomized (ovx) animal by administering 17{dollar}\beta{dollar}-estradiol (E{dollar}\sb2{dollar}). Uterine hypertrophy and hyperplasia may be the result of an E{dollar}\sb2{dollar}-induced increase in locally produced growth factors. This dissertation investigates the expression of several growth factors in the uterus by E{dollar}\sb2{dollar}, and correlates expression patterns of these growth factors with the E{dollar}\sb2{dollar}-induced uterotropic responses. Using the specific and sensitive method of reverse transcription-polymerase chain reaction (RT-PCR), we have shown that E{dollar}\sb2{dollar} administered to immature, ovx animals regulates the expression of several growth factors in a time dependent manner. mRNA for acidic fibroblast growth factor (aFGF), basic FGF (bFGF), keratinocyte GF (KGF) and transforming GF-beta{dollar}\sb2{dollar} (TGF-{dollar}\beta\sb2{dollar}) are all expressed in the rat uterus and their expression is enhanced by E{dollar}\sb2{dollar} treatment (6 h). Also, E{dollar}\sb2{dollar} regulation of mRNA levels for vascular endothelial growth/permeability factor (VEG/PF) was investigated. As early as 30 minutes after E{dollar}\sb2{dollar} treatment, mRNA levels for VEG/PF begin to increase and reach maximal levels at 2 h (8-fold higher than control levels). Preliminary studies show that following E{dollar}\sb2{dollar}-treatment, VEG/PF mRNA levels are highest in uterine epithelial cells. Metabolic labelling and immunoprecipitation have shown that E{dollar}\sb2{dollar} stimulates a corresponding increase in uterine VEG/PF protein production. The increase in VEG/PF levels immediately precedes the known increase in E{dollar}\sb2{dollar}-induced uterine water imbibition, and suggests that VEG/PF, a potent stimulator of vessel permeability, might play a role in this uterotropic response. The interaction of E{dollar}\sb2{dollar} and progesterone (P{dollar}\sb4{dollar}) on the regulation of VEG/PF and bFGF expression in the immature, ovx animal was also investigated. Initial studies showed that treatment of immature, ovx rats with P{dollar}\sb4{dollar} alone stimulated the expression of VEG/PF similar to the effect of E{dollar}\sb2{dollar}. However, when P{dollar}\sb4{dollar} and E{dollar}\sb2{dollar} were administered together, after 48 h of E{dollar}\sb2{dollar}-priming, P{dollar}\sb4{dollar} suppressed the E{dollar}\sb2{dollar}-induced increase in VEG/PF mRNA but had no effect on the E{dollar}\sb2{dollar}-induced increase in bFGF mRNA. Finally, the ability of recombinant human VEG/PF to mimic the effect of E{dollar}\sb2{dollar} in increasing uterine vessel permeability by direct injection into the uterine lumen was investigated. Similarly we attempted to inhibit the effects of E{dollar}\sb2{dollar} by treating the animals, intraluminally, with antisense VEG/PF and anti-VEG/PF antiserum. These studies were not successful. The E{dollar}\sb2{dollar}-induced uterine proliferative response most likely involves a complex interaction of a variety of growth factors. The data have shown that E{dollar}\sb2{dollar} stimulates expression of several growth factors in the rat uterus. The rapid E{dollar}\sb2{dollar}-induced increase in VEG/PF mRNA (2 h), suggests that VEG/PF expression may be a prerequisite for the subsequent expression or action of other growth factors present in the uterus.