Estrogen receptor-β is the predominant estrogen receptor subtype in human oral epithelium and salivary glands

Many studies have shown that the oral mucosa and salivary glands are sensitive to estrogen action. However, the expression of estrogen receptors (ERs) within these tissues is an area of controversy. ERs exist as two subtypes (ERα and ERβ), and we hypothesized that the incongruity between ER expression and estrogen sensitivity may result from differential expression of ER subtypes in oral tissues. To test this hypothesis, we analyzed oral mucosal and salivary gland samples for ERα and ERβ protein expression by immunohistochemistry from a cross-section of patients attending hospital for surgical problems of the head and neck. ERα was not detected in oral buccal and gingival epithelium or in salivary glands. In contrast, ERβ was widely expressed at high levels in all oral tissues studied. Within these tissues, ERβ was observed primarily in keratinocytes and salivary gland acinar and ductal cells. Our results demonstrating the expression of only the ERβ subtype within oral tissues may explain the contradictory results from previous studies investigating ER expression in these tissues. Importantly, these results suggest that estrogens may act via ERβ in oral tissues and explain the effect of hormonal changes on the oral mucosa as well as on saliva secretion and composition.