Estrogen receptor-α and -β expression in microvascular endothelial cells and smooth muscle cells of myometrium and leiomyoma

Abstract

The two estrogen receptors, ERα and ERβ, are likely to have roles in the pathophysiology of fibroid development. They have been detected in myometrial and leiomyoma (fibroid) tissue, but the cell types expressing ERα and ERβ have not been determined. ERs have also been detected in human endothelial cells. The aims of the present study were to determine whether pure populations of myometrial microvascular endothelial cells (MEC) express ERα and ERβ, to compare MEC ERα/ERβ expression with that of pure populations of myometrial smooth muscle cells (SMC) and to determine if ERα/ERβ are differentially expressed in MEC and SMC of myometrium and fibroids from nine paired samples. Using RT-PCR (for ERα and ERβ) and Western blotting (for ERα only), we demonstrated that all cultures of early passage myometrial and fibroid SMC (>99% pure) expressed ERα but not ERβ, while myometrial and fibroid MEC (>99% CD31+) constitutively expressed ERβ. However, both myometrial and fibroid MEC showed variable expression of ERα, with ∼60% of MEC samples expressing ERα. While the majority (6/9) of MEC from myometrial and fibroid pairs demonstrated the same pattern of ERα expression, 3/9 pairs showed discordant ERα expression. These results show that ERα and ERβ are differentially expressed in SMC and MEC of human myometrium and fibroids. Since ERα and ERβ mediate opposing transcriptional activities, any effect of estrogen on the growth and development of fibroids is likely to be complex and may involve both SMC and MEC.