Presence of neuroendocrine cells during postnatal development in rat prostate: Immunohistochemical, molecular, and quantitative study

Sustained density of neuroendocrine cells with aging precedes development of prostatic hyperplasia in spontaneously hypertensive rats

BACKGROUND

Neuroendocrine (NE) cells may have an impact on the development and initial growth of benign prostatic hyperplasia (BPH) according to previous human studies.

METHODS

To explore the relationship of NE cells and BPH development, we compared the density of NE cells and also prostatic weight in spontaneously hypertensive rats (SHR), which develop by aging, and Wistar-Kyoto rats (WKY) as control. The total weights of the epithelium and stroma in the ventral lobes of 8-, 12, 16-, 28- and 56-week-old SHR and WKY were calculated using Image J software. NE cells in the ventral prostatic ducts (VPd) were quantified using immunohistochemical staining for serotonin.

RESULTS

Although there was no significant difference in the estimated total weight of the epithelium and stroma in the ventral lobes adjusted by body weight (ES weight) between the two groups at 8, 12 and 16 weeks of age, ES weight was significantly greater in the SHR group than in the WKT group at 28 and 56 weeks. The density of NE cells in the VPd decreased with aging in the WKY group, whereas it was sustained until 16 weeks and then decreased with aging in the SHR group. The difference in the density between the two groups was most marked at 16 weeks of age.

CONCLUSION

In the natural history of BPH, NE cells may play an important role in the initial development of BPH because sustained density of NE cells in the VPd precedes the development of prostatic hyperplasia.

Ovariectomy increases the phenotypic plasticity of the female prostate epithelium in the Mongolian gerbil (Meriones unguiculatus)

The female prostate is a reproductive gland that typically presents a morphology similar to that of the male gland and is highly developed in female Mongolian gerbils. Two main cell populations compose the epithelium gland: basal and secretory luminal cells. However, during postnatal development, diverse secretory cell phenotypes are distributed among the typical ones. Prostate homeostasis is under the control of sexual hormones, such as oestrogen and progesterone. After hormonal deprivation the female gland undergoes several morphophysiological changes. The objective of this study was to identify and characterise, structurally and ultrastructurally, the cellular heterogeneity of the female prostate epithelium in normal conditions and after ovariectomy. Histological routine stains, such as haematoxylin-eosin, periodic acid-Schiff and silver impregnation, as well as immunocytochemical techniques were used to enable identification of the different cell types. Some secretory cells types were identified and characterised as mucinous, basophil, clear, ciliated, droplet, spumous and neuroendocrine cells. Population tally data showed that the hormonal suppression caused by ovariectomy resulted in a decrease in the proportions of basophil and clear cells and an increase in spumous cells. Thus, the secretory epithelial cells of the female gerbil prostate are not morphologically and functionally uniform, presenting a phenotypical plasticity according to the hormonal environment in which they operate.

Distribution of Neuroendocrine Cells in the Transition Zone of the Prostate

Objectives. To evaluate the distribution of neuroendocrine (NE) cells which may influence the development of benign prostatic hyperplasia (BPH) in the transition zone (TZ). Methods. We reviewed specimens from 80 patients who underwent radical prostatectomy in our institution and evaluated the density of NE cells in the TZ. They were histologically classified into 3 groups: those with no adenomatous nodule in the TZ (group A), those with small nodules with normal epithelium and stroma around them in the TZ (group B), and those with large nodules occupying the TZ (group C). In the patients of group B, intra-adenoma (adenomatous nodules) and extra-adenoma (normal tissue) NE cells in the TZ were separately counted. Results. There were 22, 23, and 35 patients in groups A, B, and C, respectively. The median density of NE cells in the TZ of group B patients, 2.80/mm², was significantly higher than that of NE cells in group A, 1.43/mm², and group C, 0.61/mm² (p < 0.001). In group B, the median density of extra-adenoma NE cells was significantly higher than that of intra-adenoma. Conclusions. Many NE cells exist around small adenoma in the TZ. NE cells may influence the initial growth of BPH in a paracrine fashion. Trial Registration. This study approved by our institutional review board was retrospectively registered (#272-14).

Stereological Quantification of Nerve Fibers Immunoreactive to PGP 9.5, NPY, and VIP in Rat Prostate During Postnatal Development

This work was undertaken to study prostate innervation during the postnatal development of rats. It deals with the quantification of nervous fibers throughout all the regions of the rat prostate during the postnatal development using a general marker for nervous tissue, protein gene product 9.5, and 2 neuropeptides (NPY and VIP). Forty male Wistar rats (prepubertals, pubertals, young, and aged adults) were studied for immunohistochemistry of protein gene product (PGP 9.5), neuropeptide Y (NPY), and vasoactive intestinal polypeptide (VIP). They were also evaluated for length density of nerve fibers (L(V) PGP 9.5, L(V) NPY, L(V) VIP). Nerve fibers immunoreactive to the 3 antigens studied were detected in all the groups and in all the prostate zones. Periductal L(V) NPY evidenced a significant increase in the pubertal group, maintained throughout adult life. Periductal L(V) VIP showed a significant increase in young adults. The length densities of VIP and NPY fibers were significantly higher in periductal and ampular locations in comparison with dorsal and ventral sites. It can be concluded that the relative amount of nerve fibers in rat prostate, detected by PGP 9.5, does not change during postnatal development. There were significant changes in NPY and VIP fibers, showing an increase in periurethral ducts at puberty. The abundance of peptidergic innervation around the excretory ducts is related to their contractility. The development of innervation of periurethral ducts is regulated by androgens.

Regional distribution of neuroendocrine cells in the urogenital duct system of the male rat

BACKGROUND

Neuroendocrine (NE) cells are frequently present in the human prostate and urethra, whereas they are lacking in the other urogenital organs. This study was undertaken as there are only few detailed studies available on the distribution, form and function of NE cells and the structure of excretory ducts of the accessory sex organs in the male rat.

METHODS

Systematic gross anatomical dissections were combined with immunohistochemical and electron microscopic studies of the excretory ducts of the urogenital glands in male rats, with particular focus on the distribution and ultrastructure of the NE cells.

RESULTS

The topography and structure of the excretory ducts of the different glands were characterized in detail and analyzed for the distribution of NE cells. These are present (in falling frequencies) in the ducts of seminal vesicles and ventral and lateral prostate and are rare in ducts of coagulating gland, dorsal prostate, urethral epithelium, and excretory ducts of the (bulbo) urethral glands. They are absent in the respective glands proper, the deferent duct and ejaculatory ampulla. Approximately 40% of the NE cells of the ventral prostate ducts are of the "open" type, whereas these are less frequent (14%) in the seminal vesicle ducts, where the "closed" type prevails.

CONCLUSIONS

NE cells are present in unequal quantities in the excretory ducts of the accessory sex glands, but they are absent in the glands proper and the deferent ducts. This distribution pattern points to a strictly localized function and differentiation potency of NE precursor cells.

Localization of immunoreactive HIF-1alpha and HIF-2alpha in neuroendocrine cells of both benign and malignant prostate glands

BACKGROUND

Hypoxia induces increased tumor growth by promoting angiogenic and glycolytic pathways. Tumors expressing hypoxia-inducible factor-1alpha (HIF-1alpha), an important transcriptional activator of oxygen-regulated genes, are resistant to chemotherapy and radiotherapy. The major challenge in prostate cancer therapy today is to gain a better understanding of the development of hormone-refractory tumors, which is often characterized by neuroendocrine differentiation. Here we studied the expression of HIF-1alpha and HIF-2alpha in neuroendocrine cells of the benign prostate and in prostate cancer.

METHODS

Tissue sections from 30 patients who underwent radical prostatectomy and from 21 patients operated by transurethral resection of the prostate were selected for immunohistochemical analysis for expression of HIF-1alpha, HIF-2alpha, androgen receptor (AR), neuroendocrine markers (chromogranin A, synaptophysin), and two gene products downstream of HIF-1alpha: VEGF and GAPDH.

RESULTS

Immunoreactive HIF-1alpha was detected in a subpopulation of AR-negative neuroendocrine cells in benign and malignant prostate tissue. Analysis of serial sections showed that the levels of expression of GAPDH and VEGF proteins are increased in AR-negative malignant neuroendocrine cells expressing HIF-1alpha. In situ-hybridization indicated that HIF-1alpha mRNA levels are not higher in neuroendocrine prostate cancer cells relative to corresponding non-neuroendocrine tumor cells. We also demonstrated induced stabilization of nuclear HIF-1alpha in LNCaP cells by hypoxia and long-term stimulation with interleukin-6. Focal HIF-2 expression was detected in benign neuroendocrine-like cells and in malignant prostatic cells.

CONCLUSIONS

The expression of HIF-1alpha and HIF-2alpha in prostate cancer has been confirmed, but we also identified immunoreactive HIF-1alpha and downstream gene products in benign and malignant prostate neuroendocrine cells.

Comprehensive expression analysis of l-dopa decarboxylase and established neuroendocrine markers in neoadjuvant hormone-treated versus varying Gleason grade prostate tumors

Current hormone withdrawal therapies used for treatment of advanced prostate cancer lead to androgen-independent tumor growth. Increased prostatic neuroendocrine (NE) cell density has been implicated in promoting progression of prostate cancer, but the process by which this occurs remains unclear. The aim of this study was to determine whether there is an association of increased NE differentiation with neoadjuvant hormone therapy and Gleason grade. Using adjacently sectioned tissue microarrays, the expression profile of novel and known NE markers were monitored. L-Dopa decarboxylase (DDC), a catecholamine synthesis enzyme and androgen receptor (AR) coregulator protein, was identified as an additional NE marker of prostate cancer. Immunohistochemical analysis of DDC with the established NE markers, chromogranin A and bombesin, revealed a significant increase in NE differentiation after 6 months of hormone therapy and after progression to androgen independence but no apparent correlation with Gleason grade. In addition, dual immunofluorescence analysis revealed that approximately 55% of the mixed population of DDC- and chromogranin A-expressing NE cells continue to express AR. Taken together, these results suggest that the increase of NE differentiation in prostate cancers depends specifically on duration of hormone therapy. This increase may be due to the transdifferentiation of AR-expressing epithelial-derived adenocarcinoma cells into an NE cell phenotype.

Effect of Prolactin and Bromocriptine on the Population of Prostate Neuroendocrine Cells from Intact and Cyproterone Acetate-Treated Rats: Stereological and Immunohistochemical Study

This work deals with the quantification of serotonin-immunoreactive prostate neuroendocrine cells (NECs) in rats exposed to prolactin in normal, cyproterone acetate-exposed, and bromocriptine-exposed animals to establish the possible influence of prolactin with or without androgenic blockade on this cell population. Thirty male peripubertal Sprague-Dawley rats were grouped as controls (CT) and those treated with cyproterone acetate (CA), cyproterone acetate plus prolactin, cyproterone acetate plus bromocriptine, prolactin (PL), and bromocriptine (BC). The volume of ductal epithelium (Vep) and total number (NSER) of the NECs serotonin-immunoreactive were measured. NECs were detected in the periurethral ducts. Compared to CT, Vep was increased in PL and BC and NSER was decreased in CA and increased in the prolactin or bromocriptine groups. The androgenic blockade decreases NSER in rat prostate; PL induces in normal and cyproterone acetate-treated rats the increase of NSER; and BC exerts a local effect over the prostate similar to that described for PL.

Gene expression in the LNCaP human prostate cancer progression model: progression associated expression in vitro corresponds to expression changes associated with prostate cancer progression in vivo

Identification of the genes involved in prostate cancer (PCa) progression to a virulent and androgen-independent (AI) form is a major focus in the field. cDNA microarray was used to compare the gene expression profile of the indolent, androgen sensitive (AS) LNCaP PCa cell line to the aggressively metastatic, AI C4-2. Thirty-eight unique sequences from a 6388 cDNA array were found differentially expressed (> or =2-fold, 95% CI). The expression of 14 genes was lower in C4-2 than in LNCaP cells, while the reverse was true for 24 genes. Twelve genes were validated using Q-PCR, Western blotting and immunohistochemistry (IHC) of LNCaP and C4-2 xenograft. Q-PCR showed that 10 of 12 (83.3%) genes had similar patterns of expression to the array (LNCaP>C4-2: TMEFF2, ATP1B1, IL-8, BTG1, BChE, NKX3.1; LNCaP<C4-2: BNIP3, TM4SF1, AMACR, UCH-L1). By Western blot, 4/5 genes examined: TMEFF2, NKX3.1, AMACR, and UCH-L1, not IL-8, were consistent with RNA profiling. Protein expression levels were confirmed in human tumor xenografts using IHC. A large proportion of the markers found in this expression profile is consistent with those recently identified in human PCa tissues along with several novel genes that remain to be examined. These data further demonstrate the utility of the LNCaP human PCa progression model as a tool to investigate the phenotypic changes required for the progression to AI and metastasis.

Effects of castration on the expression of brain-derived neurotrophic factor (BDNF) in the vas deferens and male accessory genital glands of the rat

Brain-derived neurotrophic factor (BDNF) is a growth factor belonging to the family of neurotrophins. Although neurotrophins in the male genital organs have been well documented, their role in the biology of these organs is far from clear. In particular, little is known about the influence of sex hormones on neurotrophin expression. In the present study, using immunohistochemistry and enzyme-linked immunosorbent assay (ELISA), we investigated the distribution and tissue concentration of BDNF in the vas deferens and accessory male genital glands in normal and castrated rats. The expression of BDNF mRNA was also investigated. In normal rats, BDNF immunoreactivity was localized in the musculature of the vas deferens and vesicular gland and in the fibromuscular stromal cells of the prostate. In the ventral prostatic lobes, BDNF immunoreactivity was localized in basal, secretory and neuroendocrine epithelial cells. Innervating ganglia and nerves were immunoreactive in all the examined tracts. After castration, BDNF immunoreactivity increased in the musculature of the vesicular gland and in the fibromuscular stromal cells of both dorsal and ventral prostatic lobes. BDNF immunoreactivity also increased in the nerves. ELISA and reverse transcription/real-time polymerase chain reaction confirmed the findings of the immunohistochemical study. In the accessory glands, castration induced an increase of both BDNF tissue concentration and mRNA expression. These results suggest that BDNF is expressed in the internal male genital organs of the rat and that its expression is downregulated by androgen hormones. We hypothesize that the observed BDNF increases are related to the castration-induced regression of the sympathetic nerves.

Expression of Foxa transcription factors in the developing and adult murine prostate

BACKGROUND

The Foxa family (a1, a2, and a3) of proteins are transcription factors that are central to endodermal development. Recently, Foxa1 has been shown to regulate the transcription of several murine and human prostate specific genes involved in differentiated function by interacting with DNA promoter sequences and androgen receptors. Currently, the developmental expression pattern of Foxa proteins in the murine prostate is unknown.

METHODS

Male CD-1 mice (embryonic, prepubertal, pubertal, and adult) were used for immunohistochemical analysis of Foxa1, a2, and a3. Immunofluorescence was also performed for androgen receptor and cytokeratin 14 expression. Prostate tissue from pre-pubertal, pubertal, and adult mice were analyzed by Western blot and RT-PCR analysis for Foxa1, a2, and a3 expression.

RESULTS

Strong Foxa1 immunoreactivity was observed in epithelial cells throughout prostate development, growth, and adult differentiation. Prominent Foxa2 protein expression was only observed in the early stages of prostate development and was exclusively localized to epithelial cells of the forming buds. RT-PCR analysis identified low Foxa2 mRNA expression levels in the ventral and dorsolateral lobes of the adult prostate, with Foxa2 epithelial cell expression being localized to periurethral regions of the murine adult prostatic complex. Foxa3 expression was not observed in the murine prostate.

CONCLUSIONS

Foxa proteins represent epithelial cell markers in the murine prostate gland. The early expression of Foxa1 and a2 proteins in prostate formation suggests that these proteins play an important role in normal prostate development, in addition to differentiated secretory function.

Purinergic receptors coupled to intracellular Ca2+ signals and exocytosis in rat prostate neuroendocrine cells

Rat prostate neuroendocrine cells (RPNECs) display a variety of ion channels and exhibit alpha-adrenergic regulation of cytosolic Ca(2+) concentration ([Ca(2+)])(c). In this study, purinergic regulation of [Ca(2+)](c) and exocytosis was investigated in freshly isolated single RPNECs showing chromogranin A immunoreactivity. The presence of P2X and P2Y receptors in RPNECs was verified by the transient activation of Ca(2+)-permeable cationic channels and the release of Ca(2+) from intracellular stores by extracellular ATP, respectively. The transient inward cationic current was effectively activated by alpha,beta-methyleneadenosine 5'-triphosphate (alpha,beta-MeATP) and blocked by 2',3'-O-(2,4,6-trinitrophenyl)adenosine 5'-triphosphate, suggesting the presence of a P2X(1) or P2X(3) subtype. For the release of stored Ca(2+), ATP and UTP were equally potent, indicating the functional expression of the P2Y(2) or P2Y(4) subtype. The mRNAs for P2X(1) and P2Y(2) were confirmed from reverse transcription-PCR analysis of RPNECs. The application of alpha,beta-MeATP induced large and transient increases in [Ca(2+)](c), which were not attenuated by the blockers of voltage-activated Ca(2+) channels or by depleting intracellular Ca(2+) stores, but were abolished by omitting extracellular Ca(2+). The application of UTP increased [Ca(2+)](c) to 55% of the peak Delta[Ca(2+)](c) induced by alpha,beta-MeATP. The application of alpha,beta-MeATP induced exocytotic responses of RPNECs as monitored by carbon fiber amperometry and capacitance measurements. To our interest, the application of UTP did not induce amperometric currents, but reduced the membrane capacitance, indicating a net endocytosis. From these results, we postulate that a sharp rise in [Ca(2+)](c) by the P2X-mediated Ca(2+) influx is required for exocytosis, whereas the relatively slow release of stored Ca(2+) induces endocytosis in RPNECs.