ERbeta Immunoreactivity Research Articles

Estrogen receptors alpha and beta are differentially expressed in developing human bone.

Estrogen plays an essential role in the development and maintenance of the skeleton; its effects are mediated via interactions with two estrogen receptor (ER) subtypes, alpha and beta. The aim of this study was to establish the cellular distribution of ERalpha and ERbeta in neonatal human rib bone. ERalpha and ERbeta immunoreactivity was seen in proliferative and prehypertrophic chondrocytes in the growth plate, with lower levels of expression in the late hypertrophic zone. Different patterns of expression of the two ERs were seen in bone. In cortical bone, intense staining for ERalpha was observed in osteoblasts and osteocytes adjacent to the periosteal-forming surface and in osteoclasts on the opposing resorbing surface. In cancellous bone, ERbeta was strongly expressed in both osteoblasts and osteocytes, whereas only low expression of ERalpha was seen in these areas. Nuclear and cytoplasmic staining for ERbeta was apparent in osteoclasts. These observations demonstrate distinct patterns of expression for the two ER subtypes in developing human bone and indicate functions in both the growth plate and mineralized bone. In the latter, ERalpha is predominantly expressed in cortical bone, whereas ERbeta shows higher levels of expression in cancellous bone.

Oestrogen receptor alpha and beta in rat prostate and epididymis.

The cellular localization of two oestrogen receptor (ER) subtypes, ER alpha and ER beta, was investigated in neonatal, postnatal, immature and adult male rats to determine whether these receptor subtypes are differentially expressed in prostate and epididymis. A monoclonal antibody against ER alpha and two polyclonal ER beta antibodies were used. Paraffin sections revealed a specific nuclear immunoreaction product in certain cells but not in others. In the epididymis, nuclear ER alpha immunoreactivity (IR) was detected in epithelial cells of efferent ductules and initial segments as well as in connective tissue surrounding the tubules in caput, corpus and cauda. No IR was observed in rete testis. Epithelial cells of the prostate lacked ER alpha IR, but connective tissue cells surrounding prostatic buds in the early neonatal period revealed IR. In prostate, ER beta IR was expressed in epithelial cells of the ventral and dorsolateral lobes, but the IR intensity was higher in the ventral lobe. In neonatal rats, ER beta was expressed in the epididymis but not in the prostate gland. Weak ER beta expression was found in the prostates of 5-day-old rats, and the reaction increased in intensity thereafter. In the epididymis, a similar developmental expression pattern of ER beta was observed. ER beta expression in prostate and epididymis was similar to expression of androgen receptors reported previously for these organs. The results support that both ER alpha and ER beta may be involved in oestrogen modulation of prostate and epididymal functions.

Immunolocalisation of oestrogen receptor beta in human tissues.

Oestrogens exert their actions via specific nuclear protein receptors that are members of the steroid/thyroid receptor superfamily of transcription factors. Recently, a second oestrogen receptor (ERbeta) has been cloned, and using reverse transcription-PCR and immunohistochemistry it has been shown to have a wide tissue distribution in the rat that is distinct from the classical oestrogen receptor, ERalpha. Using commercial polyclonal antisera against peptides specific to human ERbeta, we have determined the sites of ERbeta expression in archival and formalin-fixed human tissue and compared its expression with that of ERalpha. ERbeta was localised to the cell nuclei of a wide range of normal adult human tissues including ovary, Fallopian tube, uterus, lung, kidney, brain, heart, prostate and testis. In the ovary, ERbeta was present in multiple cell types including granulosa cells in small, medium and large follicles, theca and corpora lutea, whereas ERalpha was weakly expressed in the nuclei of granulosa cells, but not in the theca nor in the copora lutea. In the endometrium, both ERalpha and ERbeta were observed in luminal epithelial cells and in the nuclei of stromal cells but, significantly, ERbeta was weak or absent from endometrial glandular epithelia. Epithelial cells in most male tissues including the prostate, the urothelium and muscle layers of the bladder, and Sertoli cells in the testis, were also immunopositive for ERbeta. Significant ERbeta immunoreactivity was detected in most areas of the brain, with the exception of the hippocampus - a tissue that stained positively for ERalpha. In conclusion, the almost ubiquitous immunohistochemical localisation of ERbeta indicates that ERbeta may play a major role in the mediation of oestrogen action. The differential expression of ERalpha and ERbeta in some of these tissues suggests a more complex control mechanism in oestrogenic potential than originally envisioned.

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

Estrogens have profound effects on bone metabolism. Cellular responses to estrogens are mediated by estrogen receptors (ERs) which belong to the nuclear receptor superfamily. Two estrogen receptors, ERalpha and ERbeta, have been cloned. Previously expression of ERalpha has been shown in osteoblasts. Here we demonstrate that the transcript for ERbeta 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 ERbeta protein is present in nuclear extracts from these cells. Furthermore, ERbeta immunoreactivity is found in sections of murine and human bone. Murine and human osteoblast and osteocyte nuclei are immunoreactive for ERbeta. Osteoclasts are also ERbeta immunoreactive but the staining is mainly cytoplasmic. The present study demonstrates that ERbeta is present in all the cellular compartments involved in bone formation and bone resorption, both in human and in murine bone tissue.

Ontogeny of estrogen receptor-beta expression in rat testis.

The recently discovered estrogen receptor-beta (ERbeta) is expressed in rodent and human testes. To obtain insight in the physiological role of ERbeta we have investigated the cell type-specific expression pattern of ERbeta messenger RNA (mRNA) and protein in the testis of rats of various ages by in situ hybridization and immunohistochemistry. In fetal testes of rats 16 days postcoitum and testes of 4-day-old animals, fetal germ cells (gonocytes) reveal the ERbeta mRNA in their cytoplasm and the ERbeta protein in their nucleus. In testes of 11- and 15-day-old rats, ERbeta mRNA and protein were detected in Sertoli cells and type A spermatogonia. No signal was found in other types of germ cells. In the adult testes, expression of ERbeta mRNA as well as ERbeta protein was found in pachytene spermatocytes from epithelial stages VII-XIV and in round spermatids from stages I-VIII. Low ERbeta expression was observed in all type A spermatogonia, including undifferentiated A spermatogonia, whereas no expression was found in In and type B spermatogonia and early spermatocytes. At all ages, Sertoli cells showed a weak hybridization signal as well as weak immunoreactivity for ERbeta. In adult testes, no ERbeta mRNA or protein was detected in the interstitial tissue, indicating that Leydig cells and peritubular myoid cells do not express ERbeta. The expression of ERbeta in fetal and late male germ cells as well as in Sertoli cells suggests that estrogens directly affect germ cells during testicular development and spermatogenesis.

Differential expression of estrogen receptor alpha and beta immunoreactivity by oxytocin neurons of rat paraventricular nucleus.

An understanding of the functional significance of the newly identified estrogen receptor (ER beta) in the brain will require definition of its expression pattern and relationship to ER alpha. Using an antibody generated against the C-terminus of rat ER beta, we report the presence of ER beta immunoreactivity in the lateral septum, medial amygdala, hippocampus and paraventricular nucleus (PVN) of ovariectomized rats. Double labelling studies in the PVN revealed that approximately 35% of oxytocin neurons located principally in the medial and lateral parvocellular divisions of the caudal PVN were immunoreactive for ER beta while vasopressin, somatostatin and magnocellular oxytocin neurons exhibited no ER beta staining with this antibody. No ER alpha immunoreactive cells were identified in the caudal PVN. These observations provide direct evidence for the differential expression of ER sub-types within neurons and indicate that ER beta may be of physiological significance in the regulation of hypothalamic parvocellular oxytocin neurons by estrogen.