Immunohistochemistry and in situ hybridization of the androgen receptor in the developing human prostate

The prostate in women: an updated histological and immunohistochemical profile of the female periurethral glands and their relationship to an implanted midurethral sling

BACKGROUND

There is evidence of glandular tissue in the region of the anterior vaginal wall-female periurethral tissue (AVW-FPT) that has similar morphology and immunohistochemistry to the prostate in men. Surgical injury to this tissue has been suggested as a potential cause of sexual dysfunction following midurethral sling (MUS) procedures. However, the anatomy and embryology of these glands have not been fully resolved. This has led to difficulties in classifying this tissue as a prostate and defining its clinical significance related to MUS procedures.

AIM

To describe the histological and immunohistochemical characteristics of the female periurethral glands using markers of prostate tissue and innervation and to examine their anatomical relationships to an implanted MUS.

METHODS

Using gross and fine dissection, the AVW-FPT was dissected from 9 cadavers. Prior to dissection, 2 cadavers underwent simulation of the MUS procedure by a urogynecologist. Samples were paraffin embedded and serially sectioned. Immunohistochemistry was performed using markers of prostate tissue and innervation.

OUTCOMES

Redundant immunohistochemical localization of markers for prostatic tissue and innervation of the glandular tissue of the AVW-FPT, including the region of MUS implantation.

RESULTS

Female periurethral glands were immunoreactive for markers of male prostatic tissue, including prostate-specific antigen, androgen receptor, HOXB13, and NKX3.1. Markers of innervation (protein gene product 9.5, choline acetyl transferase, and vasoactive intestinal polypeptide) also localized to certain regions of the glandular tissue and associated blood supply. Surgical simulation of the MUS procedure demonstrated that some periurethral glands are located in close proximity to an implanted sling.

CLINICAL TRANSLATION

The AVW-FPT contains glandular tissue in the surgical field of MUS implantation. Iatrogenic damage to the female periurethral glands and the associated innervation during surgery could explain the negative impacts on sexual dysfunction reported following MUS procedures.

STRENGTHS AND LIMITATIONS

This is the first study to characterize the female periurethral glands using markers of prostatic tissue in concert with markers of general and autonomic innervation and characterize their anatomical relationships within the surgical field of MUS implantation. The small sample size is a limitation of this study.

CONCLUSION

We provide further evidence that the AVW-FPT contains innervated glands that are phenotypically similar to the male prostate and may share a common embryonic origin. The microscopic and immunohistochemical features of the periurethral glands may be indicative of their functional capacity in sexual responses. The location of these glands in the surgical field of MUS procedures underscores the clinical significance of this tissue.

Development of the human prostate

This paper provides a detailed compilation of human prostatic development that includes human fetal prostatic gross anatomy, histology, and ontogeny of selected epithelial and mesenchymal differentiation markers and signaling molecules throughout the stages of human prostatic development: (a) pre-bud urogenital sinus (UGS), (b) emergence of solid prostatic epithelial buds from urogenital sinus epithelium (UGE), (c) bud elongation and branching, (d) canalization of the solid epithelial cords, (e) differentiation of luminal and basal epithelial cells, and (f) secretory cytodifferentiation. Additionally, we describe the use of xenografts to assess the actions of androgens and estrogens on human fetal prostatic development. In this regard, we report a new model of de novo DHT-induction of prostatic development from xenografts of human fetal female urethras, which emphasizes the utility of the xenograft approach for investigation of initiation of human prostatic development. These studies raise the possibility of molecular mechanistic studies on human prostatic development through the use of tissue recombinants composed of mutant mouse UGM combined with human fetal prostatic epithelium. Our compilation of human prostatic developmental processes is likely to advance our understanding of the pathogenesis of benign prostatic hyperplasia and prostate cancer as the neoformation of ductal-acinar architecture during normal development is shared during the pathogenesis of benign prostatic hyperplasia and prostate cancer.

Maturation of the developing human fetal prostate in a rodent xenograft model

BACKGROUND

Prostate cancer is the most commonly diagnosed nonskin cancer in men. The etiology of prostate cancer is unknown, although both animal and epidemiologic data suggest that early life exposures to various toxicants, may impact DNA methylation status during development, playing an important role.

METHODS

We have developed a xenograft model to characterize the growth and differentiation of human fetal prostate implants (gestational age 12-24 weeks) that can provide new data on the potential role of early life stressors on prostate cancer. The expression of key immunohistochemical markers responsible for prostate maturation was evaluated, including p63, cytokeratin 18, α-smooth muscle actin, vimentin, caldesmon, Ki-67, prostate-specific antigen, estrogen receptor-α, and androgen receptor. Xenografts were separated into epithelial and stromal compartments using laser capture microdissection (LCM), and the DNA methylation status was assessed in >480,000 CpG sites throughout the genome.

RESULTS

Xenografts demonstrated growth and maturation throughout the 200 days of post-implantation evaluation. DNA methylation profiles of laser capture microdissected tissue demonstrated tissue-specific markers clustered by their location in either the epithelium or stroma of human prostate tissue. Differential methylated promoter region CpG-associated gene analysis revealed significantly more stromal than epithelial DNA methylation in the 30- and 90-day xenografts. Functional classification analysis identified CpG-related gene clusters in methylated epithelial and stromal human xenografts.

CONCLUSION

This study of human fetal prostate tissue establishes a xenograft model that demonstrates dynamic growth and maturation, allowing for future mechanistic studies of the developmental origins of later life proliferative prostate disease.

46,XY disorders of sex development--the undermasculinised male with disorders of androgen action

Insensitivity to the action of androgens is a common cause of undermasculinisation in 46,XY individuals. These disorders are a result of the failure of major androgens to act via the intracellular androgen receptor and, thus, the genomic effects of androgen signalling are disrupted. The phenotype of affected individuals can vary considerably, depending on the dysfunction of the receptor. In childhood, the diagnosis is often complicated due to the lack of sensitive biochemical determinants, whilst during adolescence and in adults, the diagnosis can be readily made because of the striking clinical feminisation and a conclusive laboratory analysis. A variety of mutations in the androgen receptor have been analysed, providing insight into the complex pathways of intracellular processing and signal transduction via the androgen receptor. Endocrine therapy in androgen-insensitivity syndrome is controversial, because till date the special hormonal profiles in androgen insensitivity have not been acknowledged in replacement strategies.

Transfection with steroid-responsive reporter constructs shows glucocorticoid rather than androgen responsiveness in cultured Sertoli cells

It remains unclear why it has proven so difficult to identify androgen target genes in cultured Sertoli cells. Given the lack of useful endogenous reporter genes, we studied the androgen and glucocorticoid responsiveness of these cells by transfection with three different steroid-responsive reporter constructs. The constructs were driven by the tyrosine aminotransferase steroid-responsive region (TAT-GRE4x-Luc), the mouse mammary tumor virus promoter (MMTV-Luc) and the Pem homeobox gene proximal promoter respectively (Pem-Luc). These constructs can be activated either by both the glucocorticoid receptor (GR) and the androgen receptor (AR) (TAT-GRE4x-Luc and MMTV-Luc) or selectively by the AR (Pem-Luc). Despite high transfection efficiency (30-40%) none of the constructs could be activated by treatment of the Sertoli cells with testosterone, 5alpha-dihydrotestosterone or synthetic androgens. Even pretreatment with follicle-stimulating hormone to raise AR levels (from 31 up to 82fmol/mg protein) did not result in androgen responsiveness. In contrast, treatment with dexamethasone markedly stimulated TAT-GRE4x-Luc and MMTV-Luc activity. GR levels reached a value of 172fmol/mg protein in the cultured cells and both AR and GR displayed homogeneous distribution by immunocytochemical evaluation. Androgen responsiveness was restored and glucocorticoid responsiveness was increased by cotransfection with AR or GR expression constructs. Under cotransfection conditions, 1nM of testosterone (a concentration that is some 100 times lower than that estimated to be present in the testis) was sufficient to stimulate the TAT-GRE4x-Luc maximally. Our data indicate that cultured Sertoli cells respond better to glucocorticoids than to androgens and that one of the factors limiting androgen responsiveness is the availability of AR. Other factors limiting the transactivation capacity of the (endogenous) AR, however, cannot be excluded.

Immunohistochemical localization of androgen receptors in the urogenital tracts of human embryos

The aim of this study was to investigate androgen receptor (AR) expression in the developing human urogenital tract. The distribution of AR was examined in paraffin-embedded tissue sections of the lower urogenital tract using 55 human embryos of 8-12 weeks of gestation. Immunohistochemistry was performed for AR detection and gender was determined by polymerized chain reaction. There were no differences in the distribution of AR in male and female embryos at any stage of gestation. AR was present only in the mesenchymal tissues of the urogenital sinus at 8 weeks whilst the epithelium was negative, but after 9 weeks the epithelium also showed progressively more positive staining. In the phallus, AR staining was prominent. There was far less staining in the epithelium of the urethral groove from 8 to 10 weeks, whilst the mesenchyme of the urethral folds showed positive staining. At 11 and 12 weeks, both the urethral groove and folds showed uniform staining. The genital tubercle, genital swelling and bulbourethral gland precusors were also positively stained, although paramesonephric ducts were negative. Staining was observed in the mesonephric duct from 9 weeks. There was an absence of staining in the rectum at all stages of gestation. The expression of AR in an epithelium may be dependent upon the mesenchyme. Mesenchymal-epithelial interactions played an important role in development, as has been described in experimental animals. AR expression could play a part in the growth of the genital organs.

Molecular profiling of human prostate tissues: insights into gene expression patterns of prostate development during puberty

Testosterone production surges during puberty and orchestrates massive growth and reorganization of the prostate gland, and this glandular architecture is maintained thereafter throughout adulthood. Benign prostatic hyperplasia (BPH) and prostate adenocarcinoma (PCA) are common diseases in adulthood that do not develop in the absence of androgens. Our objective was to gain insight into gene expression changes of the prostate gland at puberty, a crucial juncture in prostate development that is androgen dependent. Understanding the role played by androgens in normal prostate development may provide greater insight into androgen involvement in prostatic diseases. Benign prostate tissues obtained from pubertal and adult age group cadaveric organ donors were harvested and profiled using 20,000 element cDNA microarrays. Statistical analysis of the microarray data identified 375 genes that were differentially expressed in pubertal prostates relative to adult prostates including genes such as Nkx3.1, TMEPAI, TGFBR3, FASN, ANKH, TGFBR2, FAAH, S100P, HoxB13, fibronectin, and TSC2 among others. Comparisons of pubertal and BPH expression profiles revealed a subset of genes that shared the expression pattern between the two groups. In addition, we observed that several genes from this list were previously demonstrated to be regulated by androgen and hence could also be potential in vivo targets of androgen action in the pubertal human prostate. Promoter searches revealed the presence of androgen response elements in a cohort of genes including tumor necrosis factor-alpha induced adipose related protein, which was found to be induced by androgen. In summary, this is the first report that provides a comprehensive view of the molecular events that occur during puberty in the human prostate and provides a cohort of genes that could be potential in vivo targets of androgenic action during puberty.

Post-natal development of the rat testis: steroid hormone receptor distribution and extracellular matrix deposition

The control of testicular development and differentiation depends on hormones and a variety of cell-cell interactions mediated mainly by paracrine factors. In the second and third weeks of post-natal development important changes take place in the rat testis, e.g. the tubular lumen starts to open on post-natal day 10, the blood-testis barrier starts to form on day 15, and Sertoli cell proliferation ceases on day 15. In the present study the expression in different testicular compartments of the androgen receptor (AR), progesterone receptor (PR), and extracellular matrix proteins such as laminin, entactin-1 (nidogen-1) and fibronectin, during post-natal development was examined using immunohistochemistry and semiquantitative image analysis. An intratubular AR peak on days 14-17, an increase in intratubular PR expression on days 14-16, and an increase in peritubular entactin-1 expression during the second and third weeks post-partum are demonstrated. These results suggest that a variety of changes occur at the cellular level during this period when certain milestones of testicular development occur, substantiating the hypothesis of a particular role for paracrine interactions during the development of the rat testis.

Semiquantitative morphology of human prostatic development and regional distribution of prostatic neuroendocrine cells

BACKGROUND

The neuroendocrine cells of the human prostate have been related to proliferative disorders such as prostatic cancer. Their origin, distribution, and development have therefore been studied and discussed in terms of current stem cell concepts in the prostate.

METHODS

Prostatic tissue specimens (n = 20) from human fetuses (n = 8), prepubertal and pubertal children (n = 8) and mature men (n = 4) were studied immunohistochemically using antibodies directed against neuroendocrine, epithelial as well as secretory markers. Semiquantitative computer-assisted evaluation of different epithelial and stromal components based on stereological principles was performed on azan-stained sections representative of all developmental stages.

RESULTS

By the end of gestational Week 9, neuroendocrine (NE) cells appear in the epithelium of the urogenital sinus and are subsequently closely associated with the formation of urethral prostatic buds. The fetal and postnatal distribution pattern of NE cells within the gland is characterized by a relatively constant number of cells per gland similar to prostatic smooth muscle cells. Likewise, a density gradient exists with the highest density in the large collicular ducts and almost no NE cells in subcapsular peripheral acini. In peripheral ducts, the distribution is random. Maturation of the NE cells precedes that of the secretory cells by about 10-16 years.

CONCLUSIONS

A second prostatic stem cell lineage, different from the urogenital sinus (UGS)-lineage is hypothesized originating from immature neuroendocrine cells. Being morphologically indistinguishable from the UGS-derived prostatic secretory cell lineage, it gives rise to neuroendocrine cells. Their presence is apparently important for proliferation regulation of the UGS-derived lineage of the prostate.

FHL2, a novel tissue-specific coactivator of the androgen receptor

The control of target gene expression by nuclear receptors requires the recruitment of multiple cofactors. However, the exact mechanisms by which nuclear receptor-cofactor interactions result in tissue-specific gene regulation are unclear. Here we characterize a novel tissue-specific coactivator for the androgen receptor (AR), which is identical to a previously reported protein FHL2/DRAL with unknown function. In the adult, FHL2 is expressed in the myocardium of the heart and in the epithelial cells of the prostate, where it colocalizes with the AR in the nucleus. FHL2 contains a strong, autonomous transactivation function and binds specifically to the AR in vitro and in vivo. In an agonist- and AF-2-dependent manner FHL2 selectively increases the transcriptional activity of the AR, but not that of any other nuclear receptor. In addition, the transcription of the prostate-specific AR target gene probasin is coactivated by FHL2. Taken together, our data demonstrate that FHL2 is the first LIM-only coactivator of the AR with a unique tissue-specific expression pattern.

Neurogenic origin of human prostate endocrine cells

OBJECTIVES

To determine the histogenetic origin of prostate neuroendocrine cells in human embryos.

METHODS

Prostatic tissue in human fetuses, ranging in gestational age from early week 10 to term, and infantile and pubertal glands were studied immunohistochemically. The distribution of neuroendocrine cells within the developing gland was semiquantitatively determined. Antibodies against the neuroendocrine markers chromogranin A (CgA) and protein gene product 9.5 (PGP), along with markers of prostatic secretion (prostate-specific antigen [PSA], prostatic acid phosphatase [PAP]), were used. They were applied either individually or in double-labeling experiments, as well as in experiments combining CgA immunohistochemical analysis with in situ hybridization or in situ end-labeling.

RESULTS

In embryos of less than 65-mm crown-rump length (CRL) (ie, younger than 12 weeks of gestation), the epithelium of the urogenital sinus was free of endocrine cells. On either side of the future prostatic mesenchyme, paraganglia containing CgA-immunoreactive cells are present, which start to penetrate the urogenital mesenchyme. In the late 10th week, these CgA-immunoreactive cells are found dispersed in the urogenital mesenchyme. In embryos of 65-mm CRL, when prostatic anlagen start to sprout from the urogenital epithelium, very few (but typically shaped) neuroendocrine cells appear in the urogenital sinus epithelium. Later, after the 12th week, when solid prostatic ducts have started forming, CgA-immunoreactive neuroendocrine cells are also present in these buds. The number of neuroendocrine cells in the urethral epithelium is considerably increased, and with the continuous sprouting and lumen formation of prostatic anlagen, neuroendocrine cells are transported into the future gland. Neuroendocrine cells observed in stroma of prenatal and postnatal prostates may also contribute to the neuroendocrine cell population of the gland.

CONCLUSIONS

Our results provide the first evidence that human prostate neuroendocrine cells represent a cell lineage of their own, being of neurogenic origin and therefore distinct from the urogenital sinus-derived prostate secretory and basal cells.

Localization of type 5 17beta-hydroxysteroid dehydrogenase, 3beta-hydroxysteroid dehydrogenase, and androgen receptor in the human prostate by in situ hybridization and immunocytochemistry

An important source of androgens in the human prostate are those synthesized locally from the inactive adrenal precursor dehydroepiandrosterone (DHEA) and its sulfated derivative DHEA-S. Three beta-HSD (hydroxysteroid dehydrogenase) converts DHEA into androstenedione (4-dione), whereas type 5 17beta-HSD catalyzes the reduction of 4-dione into testosterone in the human prostate and other peripheral intracrine tissues. In the present study, we have used two complementary approaches, namely in situ hybridization and immunocytochemistry, to identify the cells that contain the type 5 17beta-HSD messenger RNA and enzyme in human benign prostatic hyperplasia (BPH). Localization of 3beta-HSD and of the androgen receptor (AR) was also investigated by immunostaining in the same tissue. To find out whether there are any differences between BPH and normal prostate tissue, the localization of type 5 17beta-HSD was reexamined by immunocytochemistry in the normal human prostate samples and also in normal prostate epithelial cell line (PrEC). The in situ hybridization results obtained with a tritiated uridine triphosphate (3H-UTP)-labeled type 5 17beta-HSD riboprobe are in agreement with the immunostaining data obtained with a specific antibody to the enzyme. The immunostaining results obtained from normal prostate tissue and BPH were found to be similar. Thus, in the glandular epithelium, basal cells highly express the messenger RNA and the enzyme, whereas luminal cells show a much lower and variable level of expression. In the stroma and walls of blood vessels, fibroblasts and the endothelial cells lining the blood vessels show positive staining. Similar results are observed when the cellular distribution of 3beta-HSD is investigated. AR immunoreactivity, however, shows a different distribution because, in the epithelium, most of the nuclei of basal cells are negative, whereas the majority of nuclei of the luminal cells show positive staining. A strong reaction for AR is also found in most stromal cell nuclei and in the nuclei of most endothelial cells, as well as in some other cells of the walls of blood vessels. In conclusion, human type 5 17beta-HSD, as well as 3beta-HSD, are highly expressed, not only in the basal epithelial cells and stromal fibroblasts but also in the endothelial cells and fibroblasts of the blood vessels. AR, on the other hand, is highly expressed in the luminal cells. The present data suggest that DHEA is transformed in the basal cells of the glandular epithelium into 4-dione by 3beta-HSD and then into testosterone by type 5 17beta-HSD, whereas dihydrotestosterone is synthesized in the luminal cells after diffusion of testosterone from the underlying layer of basal cells. The potential role of androgen formation and action in blood vessels is unknown and opens new avenues of investigation for a better understanding of the multiple roles of androgens.

Physiology and pathophysiology of androgen action

Knowledge of the physiology of male sexual differentiation and the clinical presentation of androgen insensitivity syndromes (AIS) has led to an increasing understanding of the mechanisms of androgen action. Androgens induce their specific response via the androgen receptor (AR), which in turn regulates the transcription of androgen-responsive target genes. The androgen-dependent development of male genital structures and the induction of the normal male phenotype depends on the presence of an intact AR. Structural alterations leading to malfunction of the AR are associated with variable inhibition of virilization despite normal or even supranormal serum levels of androgens. The mapping, cloning and sequencing of the AR gene have facilitated new insights into the study of androgen action. Functional investigation of the normal and the mutant AR in vivo as well as in vitro has led to the characterization of the distinct molecular steps involved in the normal androgen action pathways that are inhibited in the androgen insensitivity syndrome.