Cellular localization of estrogen receptor beta messenger ribonucleic acid in cynomolgus monkey reproductive organs.

There is now evidence that the recently identified estrogen receptor (ER) beta is more widely distributed in the body than is ER-alpha. In order to gain more information about the role of ER-beta in reproduction, we have investigated by in situ hybridization the localization of mRNA expression of this ER subtype in adult monkey reproductive organs. In the pituitary gland of animals of both sexes, in both the anterior and intermediate lobes, a large number of cells were positive. No specific signal was observed in the posterior lobe. In the ovary, granulosa cells in primary and growing follicles highly expressed ER-beta mRNA. The theca interna cells were also strongly labeled. In some corpora lutea, the luteal cells were strongly labeled, while in other ones, the signal was weak. A hybridization signal was also detected in the ovarian surface epithelium. In the uterus, ER-beta mRNA was found in high concentration in glandular epithelial cells and stromal cells of the endometrium, while weaker labeling was consistently observed in smooth muscle cells. In the mammary gland, labeling was detected in the epithelial cells of acini and interlobular ducts as well as stromal cells. In the testis, specific labeling was detected in the seminiferous epithelium whereas the interstitial Leydig cells were unlabeled. Although it was not possible to clearly identify all the positive cell types, it appears that Sertoli cells as well as the vast majority of germinal cells express ER-beta mRNA. In the prostate, the secretory epithelial cells exhibited a specific autoradiographic reaction while the stromal cells did not show mRNA expression. The epithelial cells of the prostatic urethra showed a strong labeling. No hybridization signal was detected in the seminal vesicles. It then appears quite clear that ER-beta is expressed in a cell-specific manner in all the monkey reproductive organs studied. In the female, the wide distribution of these receptors in the ovary and uterus suggests that ER-beta may play an important role in the mediation of the known effects of estrogen in reproduction functions. In the male testis and prostate, ER-beta has been found in cells that contain very little or no ER-alpha. The role of circulating or locally produced estrogens in the male reproductive system remains to be clarified.