Expression and localization of estrogen receptor-beta in murine and human bone

Estrogens have profound effects on bone metabolism. Cellular responses to e strogens are mediated by estrogen receptors (ERs) which belong to the nucle ar receptor superfamily. Two estrogen receptors, ER alpha and ER beta, have been cloned. Previously expression of ER alpha has been shown in osteoblas ts. Here we demonstrate that the transcript for ER beta can be detected in the human osteosarcoma cell lines (MG-63 and SaOS-2) and in cultured human osteoblast-like cells. We also show that ER beta protein is present in nucl ear extracts from these cells. Furthermore, ER beta immunoreactivity is fou nd in sections of murine and human bone. Murine and human osteoblast and os teocyte nuclei are immunoreactive for ER beta. Osteoclasts are also ER beta immunoreactive but the staining is mainly cytoplasmic. The present study d emonstrates that ER beta is present in all the cellular compartments involv ed in bone formation and bone resorption, both in human and in murine bone tissue.