Volume 52 (3): 355-360, 2004 Copyright ©The Histochemical Society, Inc. Expression of Estrogen Receptors in Human Corpus Cavernosum and Male Urethra
Division of Gynecologic Endocrinology and Reproductive Medicine (WD,JCH), University of Vienna Medical School, Vienna, Austria; Department of Clinical Pathology (AH), University of Vienna Medical School, Vienna, Austria; and Department of Urology (WJR), Korneuburg Hospital, Korneuburg, Austria Correspondence to: Wolf Dietrich, MD, Div. of Gynecologic Endocrinology and Reproductive Medicine, Univ. of Vienna Medical School, Waehringer Guertel 1820, 1090 Vienna, Austria. E-mail: wolf.dietrich{at}akh-wien.ac.at
Estrogen, largely produced in testis and adrenal gland, may play important roles in male reproduction. Most of the effects of estrogens are mediated by binding of estrogen to one or both of the two estrogen receptor (ER) subtypes and ß. Recently, they have been described in testis, prostate, and efferent ducts, mostly in rodents. The goal of this study was to prove the evidence of ERs in human corpus cavernosum and male urethra, exploring the protein expression of these receptors by immunohistochemistry. Corpus cavernosum and corpus spongiosum smooth muscle was immunoreactive for the androgen receptor (AR), ER , and strongly for ERß. Endothelial cells were negative for AR, sporadically positive for ER , and positive for ERß. Urethral epithelium showed strong nuclear expression of AR, predominantly in the basal cell layer, and nuclear expression of ER in the intermediate cells. ERß was highly expressed in almost all urethral nuclei and, much more weakly, in cytoplasm. Progesterone receptor (PGR) was negative in all cases and all tissues. These results represent the first report that ER and particularly ERß are regularly expressed in human penile tissue. (J Histochem Cytochem 52:355360, 2004)
Key Words: estrogen receptor-
THE ROLE of estrogen and estrogen receptors (ERs) in male reproduction has been repeatedly elucidated since estrogen was found to be produced in male genitourinary organs by Staffieri et al. (1965) -isoform (ER ) and the more recently discovered ß-isoform (ERß) contain very similar DNA-binding domains, the overall degree of homology is low and they show different binding affinity for several natural and synthetic ligands (Kuiper et al. 1997 and ERß differ. ER is found mainly in classic estrogen target tissues, such as breast and ovary, whereas ERß has been described in kidney, lung, bone, and endothelial cells (Makela et al. 1999
Estrogens are known to stimulate growth, blood flow, and water retention in sexual organs (Jenner et al. 1972
Tissue Samples Specimens (n=23) were obtained from patients who underwent partial penectomy in Vienna University hospital because of squamous cell carcinoma of the penis. All cases, within 8 years from 1994 to 2001, for which representative material was available were enrolled in this study. Concerning other clinical diagnosis, probably affecting the vasculature, patients had at time of surgery eight arterial hypertension, five coronary heart disease, three non-insulin-dependent diabetes mellitus, one chronic veinous insufficiency and one adipositas. The ages of the patients at surgery were 2187 years (mean 65.6, SD 17.5). Tissue was fixed in formalin and routinely processed in paraffin.
Immunohistochemistry
Antibodies against AR, ER
A staining procedure was carried out for all slides using the ChemMate Detection Kit (DAKO) in which diaminobenzidine is the chromogen. After a 5-min reaction, staining was interrupted by washing in PBS followed by counterstaining with Gill's hematoxylin (Merck; Darmstadt, Germany). Positive controls for ER , ERß, PGR, and AR included previously tested and, respectively, positive breast and prostatic cancers. In the negative controls primary antibody was replaced with the respective isotype immunoglobulin (mouse IgG1 for AR441, 1D5, and PgR636; mouse IgG2a for 14C8) in the same concentration (Coulter Clone; Miami, FL). IHC was performed semiquantitatively on three sections per sample and antibody.
The intensity of nuclear staining and the number of stained cells were examined independently by two investigators (WD and AH). No significant staining was scored as 0, scattered or weak immunostaining as +, and intense immunostaining in approximately 50% or more of respective cells as ++ (Fan et al. 2002
Corpus Cavernosum (CC) Corpus cavernosum tissue was immunoreactive for AR in all cases, where nuclei of smooth muscle cells showed expression ranging from weak to strong. Endothelial cells were negative for AR in all slides (Tables 1 and 2; Figure 1) . ER protein could be detected in the nuclei of smooth muscle cells and, sporadically, in endothelial cells in seven cases. Immunostaining ranged from moderate to very weak, and the differentiation from negative results was difficult. There was no staining of cytoplasm in any slide (Tables 1 and 2; Figure 1). However, we found moderate to strong staining of ERß in >80% of the smooth muscle cells in all CCs examined. In addition, weak immunostaining of the cytoplasm could be detected in about one third of cells, which were randomly scattered between smooth muscle cells with cytoplasm not reactive for ERß. Almost all endothelial cells expressed ERß in their nuclei but not in the cytoplasm (Tables 1 and 2; Figure 1). PGR was negative in all cases and all tissues examined, even in the positive control.
Corpus Spongiosum (CS) In corpus spongiosum, a more "venous" lacunary tissue, results were nearly comparable to those in CC. ER could be detected in smooth muscle cells and some endothelia in the same seven cases where CC was immunoreactive for ER . In all 23 CS, smooth muscle showed strong ERß immmunoreactivity in the majority of cells, but there were more negative nuclei than in CC. All endothelia showed strong ERß staining. The only unequivocal difference from CC was found in five cases in which the AR could not be detected in any cells. Generally, in the periurethral stroma layer, which passes into the CS, nuclear immunostaining of all expressed steroid receptors was more impressive than in the surrounding vessels. We could not find any significant influence of age, hypertension, or coronary heart disease on CC or CS receptor status.
Urethra
In this study we investigated the distribution of AR, ER , ERß, and PGR protein in human adult penile tissues including corpus cavernosum, corpus spongiosum, and urethra. AR was expressed in smooth muscle cells of all explored CC and 18 of 23 CS tissues, whereas AR was absent in endothelial cells of all vessels. These findings of AR distribution are in accordance with earlier reports of the expression of AR in developing human fetal penis, e.g., Kim et al. (2002) , known as "the" estrogen receptor until the ß-isoform was cloned, in penile tissue is diminished. In the interesting study of Kalloo et al. (1993) could not be found in developing human penis, whereas ER mRNA and protein were detected in rat penis very recently by Jesmin et al. (2002) protein in CC and CS in 7/23 cases. Differentiation from negative results was difficult, so it can be assumed that some of the samples counted as negative actually do express ER protein in such low amounts that they cannot be detected with the antigen retrieval methods known today. On the other hand, variation in the ER status of human vasculature has been shown previously (e.g., Rogers et al. 1996 can mediate the short-term effects of estrogen on eNOS activity and may assist vasodilatation by releasing NO. Concerning possible interactions between AR and ER , as in ER -knockout male mice, in which lower expression of AR immunoreactivity was found in some areas of the brain by McAbee and DonCarlos (1999) positivity and the amount of AR protein expression in human penile tissue. Beyond that, there was no significant influence of age or disease, such as hypertension or coronary artery disease, in remodeling the vasculature or on CC or CS receptor status. We must admit that the numbers of samples in this study were too low to provide statistically relevant statements. We showed that ERß is the predominant ER subtype in human penile cavernous tissue. ERß is abundantly expressed in both smooth muscle cells and endothelium of the CC and the CS, the urethral epithelium, and the urethral glands. Although this is the first evidence of ERs in human adult penile tissue, it matches one earlier report of ER and ERß in developing rat penis by Jesmin et al. (2002) only sporadically. A comparable result was described first in vascular endothelium of rat uterus by Wang et al. (1999) to be important in the functioning and growth of endothelium both in vitro and in vivo, e.g., Brouchet et al. (2001) rather than ERß. Therefore, estrogen incubation increased VEGFR-2 expression and VEGF binding only in ER -positive myometrial microvascular endothelial cells, but expression of ER was low and variable among subjects (13 of 21 samples). In that study, the VEGFR system was not associated with ERß expression, but ERß mRNA and protein could be demonstrated at a higher level than ER in every sample. Beyond this, ERß has been demonstrated not only in the vasculature of the uterus but also in great vessels (Taylor and Al-Azzawi 2000 -deficient mice (Iafrati et al. 1997
The relevance of androgens and other sex hormones, particularly estrogen, in the modulation of the structure and function of the urothelium and the distal urethra is not yet understood. Although two reports also described strong reactivity of AR in developing human and adult rat urethra by IHC (Salmi et al. 2001
In view of the observation that ERß is expressed in human penile vasculature and urothelium in excess to the other sex steroid receptors, we propose that estrogen could play a significant role in penile blood vessel regulation and epithelial function, operating preferably on the ERß-isoform. It can be suggested that estrogen's action supports resistance to increased mechanical and hemodynamic stress, according to Lindner et al. (1998)
Received for publication June 20, 2003; accepted October 16, 2003
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