Natural history of human prostate gland: Morphometric and histopathological analysis of Japanese men

Prostatic peripheral zone thickness: what is normal on magnetic resonance imaging?

PURPOSE

To report the precision of a technique of measuring the PZ thickness on T2-weighted MRI and report normal parameters in patients with normal-sized prostates. We also wanted to establish the mean and second standard deviations (2SD) above and below the mean as criteria for abnormally narrow or expanded PZ thickness.

METHODS

Of the initial 1566 consecutive cohort referred for evaluation for carcinoma based on elevated PSA (prostate specific antibody) or DRE (digital rectal examination), 132 separate subjects with normal-sized prostates were selected for this study. Mean age was 58.2 years (15-82). Median serum PSA was 6.2 ng/mL (range 0.3-145). Most were asymptomatic for lower urinary tract symptoms (LUTS). Inclusion criteria in this study required technically adequate T2-weighted MRI and total prostatic volume (TPV) ≤ 25 cc. Exclusion criteria included post-prostatic surgical and radiation patients, patients having had medical management or minimally invasive therapy for BPH, those being treated for prostatitis. Patients with suspected tumor expanding or obscuring measurement boundaries were also not considered. Transition zone (TZ) and peripheral zone (PZ) volumes were determined using the prolate ellipsoid model. Posterolateral measurement of the PZ was obtained at the axial level of maximal transverse diameter of the prostate on a line drawn from the outer boundary of the TZ to the inner boundary of the external prostatic capsule (EPC). The data were normally distributed. Therefore, it was analyzed using the 2-sided student t-test and Pearson product correlation statistic.

RESULTS

Mean pooled (composite) measurement for the posterolateral PZ (PLPZ) was 10 mm (CI 9.5-10.5 mm) with SD of 2.87 mm. Means were statistically the same for the 2 observers (p = 0.75). Pearson correlation between the two observers was 0.63.

CONCLUSIONS

In a prostate ≤ 25 cc volume , the posterolateral PZ should be no thicker than 15.8 mm and averages 10.0 mm when measured in the maximal axial plane on MRI. These norms were independent of age or use of endorectal coil. The technique measurement demonstrated clinically useful precision.

Role of Stromal Paracrine Signals in Proliferative Diseases of the Aging Human Prostate

Androgens are essential for the development, differentiation, growth, and function of the prostate through epithelial–stromal interactions. However, androgen concentrations in the hypertrophic human prostate decrease significantly with age, suggesting an inverse correlation between androgen levels and proliferative diseases of the aging prostate. In elderly males, age- and/or androgen-related stromal remodeling is spontaneously induced, i.e., increased fibroblast and myofibroblast numbers, but decreased smooth muscle cell numbers in the prostatic stroma. These fibroblasts produce not only growth factors, cytokines, and extracellular matrix proteins, but also microRNAs as stromal paracrine signals that stimulate prostate epithelial cell proliferation. Surgical or chemical castration is the standard systemic therapy for patients with advanced prostate cancer. Androgen deprivation therapy induces temporary remission, but the majority of patients eventually progress to castration-resistant prostate cancer, which is associated with a high mortality rate. Androgen deprivation therapy-induced stromal remodeling may be involved in the development and progression of castration-resistant prostate cancer. In the tumor microenvironment, activated fibroblasts stimulating prostate cancer cell proliferation are called carcinoma-associated fibroblasts. In this review, we summarize the role of stromal paracrine signals in proliferative diseases of the aging human prostate and discuss the potential clinical applications of carcinoma-associated fibroblast-derived exosomal microRNAs as promising biomarkers.

Histological and quantitative analyzes of the stromal and acinar components of normal human prostate zones

BACKGROUND

McNeal divided the human prostate into three major anatomical areas: the peripheral zone (PZ), the central zone (CZ), and the transition zone (TZ). Each of these areas is biologically and histologically distinct. The PZ and TZ have clinical significance and are associated with prostate cancer (PC) and benign prostatic hyperplasia (BPH), respectively. Therefore, the objective of the present study was to quantitatively and qualitatively analyze the parenchymal and stromal components that constitute the different prostate zones.

METHODS

We assessed 19 samples from each prostate zone. The samples were obtained from necropsies of young people between 18 and 32 years of age with intact urogenital tracts. The samples were fixed in 4% buffered formalin and processed for paraffin embedding. Sections with a thickness of five micrometres were obtained from each sample. The sections were stained using histochemical and immunohistochemical techniques to identify the acinar and stromal components of each zone. Photomicrographs were obtained for morphometric analysis using an algorithm based on color segmentation. Data were analyzed using one-way analysis of variance (ANOVA) with the Bonferroni post-test. Differences with P < 0.05 were regarded as statistically significant.

RESULTS

Collagen fibres were more numerous in the TZ (+40.26%; P = 0.0230) than in the PZ. Muscle fibres were also more numerous in the TZ (+47.05%; P = 0.0120) than in the PZ. Elastic system fibres in the TZ significantly differed from those in the PZ (+84.61%; P = 0.0012) and the CZ (+61.66%; P = 0.0074). Similarly, nerves in the PZ (-42.86%; P = 0.0107) significantly differed from nerves in the CZ. Epithelial height was lower in the TZ than in the PZ (-30.17%; P = 0.0034) and the CZ (-25.01%; P = 0.0330).

CONCLUSION

Our objective, quantitative data regarding the various elements that constitute the normal prostate stroma allowed us to reveal differences among prostate zones. This study established patterns for normal parameters and may be used for posterior comparisons in histopathological analysis.

Selective estrogen receptor modulators for BPH: new factors on the ground

As the current management of BPH/lower urinary tract symptoms by traditionally involved pharmacological agents such as 5alpha-reductase inhibitors and α1-adrenoceptor antagonists is suboptimal, there is definite need of new therapeutic strategies. There is ample evidence in literature that suggests the role of estrogens in BPH development and management through the different tissue and cell-specific receptors. This article reviews the beneficial actions of selective estrogen receptor modulator (SERM) and ERβ-selective ligands, which have been demonstrated through in vitro studies using human prostate cell lines and in vivo animal studies. SERMs have anti-proliferative, anti-inflammatory and pro-apoptotic mechanisms in BPH, and also act by inhibiting various growth factors, and thus represent a unique and novel approach in BPH management directed at estrogen receptors or estrogen metabolism.

An overview of prostate diseases and their characteristics specific to Asian men

In this paper, we reviewed the features of common prostate diseases, such as benign prostatic hyperplasia (BPH), prostate cancer (PCa) and chronic prostatitis (CP) that are specific to Asian men. Compared to the Westerners, Asians exhibit particular characteristics of prostate diseases. Through summarizing the epidemiology, symptomatology, diagnostics and therapeutics of these diseases, we find that Asians have a lower incidence of PCa than whites, but the incidences of BPH and CP are similar. Asian men with CP often suffer from fewer disease sites, but have a higher frequency of pain during urination rather than after sexual climax. Prostate-specific antigen (PSA) is a widely used marker for the diagnosis of PCa in both Asian and Western countries. Although the PSA level may be lower in Asians, the threshold used is based on whites. After reviewing the treatments available for these diseases, we did not find a fundamental difference between Asians and whites. Furthermore, the selection for the most appropriate treatment based on the individual needs of patients remains a challenge to urologists in Asia. After considering the traits of prostate diseases that are specific to Asian men, we hope to pave the way for the development of specific diagnostic and therapeutic strategies targeted specifically to Asian men.

Biomarkers for the diagnosis of prostatic inflammation in benign prostatic hyperplasia

BACKGROUND

Chronic prostatic inflammation could be a central mechanism in benign prostatic hyperplasia (BPH) progression. Currently, the histological examination of prostate biopsies remains the only way to diagnose prostatic inflammation. Our objective was to find new noninvasive biomarkers for the diagnosis of prostatic inflammation.

METHODS

Ninety BPH samples were investigated in two steps. First, a hypothesis was generated using a profiling procedure with a panel of 96 genes on an initial set of 30 samples. Then, the candidate biomarkers were validated on a large number of samples (n = 90). Gene expression was compared with the histological prostatic inflammation score based on the density and the confluence of lymphoid nodules. Finally, protein transcripts of the candidate biomarkers were investigated in urine samples and compared with clinical data.

RESULTS

Of the 96 genes, nine were significantly correlated with the inflammation score on the initial set of patients. Four of them were validated on the complete set of patients: CCR7, CD40LG, CTLA4, and ICOS. ICOS and CTLA4 protein levels were readily measured in urine samples using a conventional ELISA procedure. High-ICOS expression in urine was associated with a higher post-void residual and a lower maximum urinary flow rate.

CONCLUSIONS

Four genes were significantly upregulated at the mRNA level in the prostate tissue of patients with severe inflammation score. Two proteins were measured in urine samples, and were associated with maximum uroflowmetry and post-void residual. A prospective clinical study is needed to confirm their clinical relevance.

Structural changes in alpha1-adrenoceptor antagonist-treated human prostatic stroma

Alpha1-adrenoceptor antagonists (alpha1-blockers) are currently used as first-line drugs for the treatment of benign prostatic hyperplasia (BPH). However, cases of BPH are often encountered in which the efficacy of alpha1-blockers decreases and switching to surgical treatment is required. One factor responsible for this resistance includes structural changes in prostatic tissue architecture following repeated oral administration of alpha1-blockers. Forty patients suspected of having prostate cancer, but without evidence of malignancy on prostatic biopsy were divided into two groups: an untreated group (n = 17) and an oral alpha1-blocker-treated group (n = 23). Twenty-one patients exhibiting resistance to oral alpha1-blocker therapy who underwent surgery were assigned into the surgically treated group. Each tissue sample was subjected to Masson's trichrome staining to distinguish collagen fibers from smooth muscle constituting prostatic stroma. The mean collagen fiber share was 62.2 +/- 10.4% in the untreated group, 72.1 +/- 9.1% in the oral alpha1-blocker-treated group, and 72.2 +/- 15.7% in the surgically treated group. Focusing on cases exhibiting high-collagen fiber share (70% or more), the distribution in each of the two alpha1-blocker-treated groups (16 of the 23 cases from the oral alpha1-blocker-treated group and 10 of the 21 cases from the surgically treated group) differed significantly from that in the untreated group (2 of the 17 cases). Our findings suggest that the accumulation of collagen fibers in prostatic stroma could be one of the factors responsible for alpha1-blocker treatment.

Duct obstruction: the possible etiopathogenesis of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a common disease of the aged. And its etiopathogenesis is still uncertain after centuries' research. Ducts of prostate were often found obstructed and ectasy in pathological examinations. Recent studies suggest that pressure can facilitate the proliferation of prostatic cells. Therefore we hypothesize that ductal obstruction can induce augmentation of intraductal pressure and facilitate the proliferation of prostatic cells. Ductal obstruction might play a role in the etiopathogenesis of BPH. If our hypothesis can be further supported by future researches, it may change the present etiopathogenesis theory of BPH as well as the treatment strategies of it.

Naftopidil, a selective alpha-1 adrenoceptor antagonist, inhibits growth of human prostate cancer cells by G1 cell cycle arrest

Alpha-1 adrenoceptor antagonists are generally prescribed for benign prostate hyperplasia with lower urinary tract symptoms. Naftopidil, a selective alpha-1 adrenoceptor antagonist, is frequently used in Japan because it has fewer side effects. Here we demonstrate for the first time that naftopidil has growth inhibitory effect in androgen-sensitive and -insensitive human prostate cancer cell lines. The concentrations causing 50% inhibition (IC50) of cancer cell growth were 22.2 +/- 4.0 microM in androgen-sensitive LNCaP cells and 33.2 +/- 1.1 microM in androgen-insensitive PC-3 cells. FACS analysis revealed that cell growth inhibition by naftopidil was due to the arrest of the G1 cell cycle. Expressions of p27(kip1) and p21(cip1) were significantly increased in LNCaP cells treated with naftopidil. In PC-3 cells, naftopidil induced p21(cip1) but not p27(kip1). In vivo, oral administration of naftopidil to nude mice inhibited the growth of PC-3 tumors as compared to vehicle-treated controls. These results suggest that naftopidil may be useful in the chemoprevention of prostate cancer and the intervention of hormone refractory prostate cancer.

Obesity and Benign Prostatic Enlargement: A Large Observational Study in China

OBJECTIVES

To investigate the associations of prostate enlargement with obesity and hypertension in Chinese men.

METHODS

A total of 649 men from Zhejiang, China were invited to the Family Planning Station of Wenlin to undergo prostate volume measurement with transrectal ultrasonography. Benign prostatic enlargement (BPE) has been defined as a prostate volume larger than 20 cm3. The associations between BPE and prostate volume with body mass index (BMI) and blood pressure were evaluated by multivariate linear and logistic regression analyses.

RESULTS

Overweight (BMI of 25 or more but less than 28 kg/m2) and obese (BMI of 28 kg/m2 or more) men experienced a significantly increased age-adjusted risk of BPE compared with men with a lower BMI (odds ratio 1.63, 95% confidence interval 1.16 to 2.30, and odds ratio 2.26, 95% confidence interval 1.11 to 4.59, respectively). Each 0.37-kg/m2 increase (95% confidence interval 0.18 to 0.57, P <0.01) in the BMI was associated with a 1-cm3 increase in prostate volume. No associations were observed between hypertension and BPE.

CONCLUSIONS

This is the first study to provide evidence that the BMI is positively associated with prostate volume in the Chinese population. Obese Chinese men are at increased risk of an enlarged prostate compared with nonobese Chinese men.