The induction of new ductal growth in adult prostatic epithelium in response to an embryonic prostatic inductor

Tissue recombinants were prepared with a single epithelial ductal tip from adult prostate and mesenchyme from either the embryonic urogenital sinus or adult urinary bladder. Recombinants were grown in vivo beneath the renal capsule of male hosts. After 4 weeks of in vivo growth, extensive growth of arborizing ducts was apparent in recombinants composed of urogenital sinus mesenchyme and a single adult prostatic ductal tip. One-dimensional polyacrylamide gel electrophoresis indicated that these recombinants contained many of the proteins of the mature prostate. Heterospecific recombinants (rat urogenital sinus mesenchyme and mouse prostatic epithelium) showed the ductal tissue to be derived solely from the prostatic epithelium. In recombinants of a prostatic ductal tip with mesenchyme from the urinary bladder, ductal growth was absent, the ductal tip was maintained as a single, discrete, epithelial structure, and the protein composition of these recombinants more closely resembled that of the bladder. The results demonstrate that the epithelial cells of the adult prostate can participate in new ductal growth in response to an embryonic prostatic inductor. These data provide experimental evidence to support the hypothesis that human benign prostatic hyperplasia may result from the anomalous reactivation of embryonic growth potential in the adult prostate.     

Evidence of stem cells in the adult prostatic epithelium based upon responsiveness to mesenchymal inductors

Ductal tips approximately 300 μm in length from adult rat dorsal (DP), lateral type 1 (L1), and lateral type 2 (L2) prostates were combined with mesenchyme from the embryonic urogenital sinus (UGM), neonatal seminal vesicle (SVM), or neonatal bulbourethral gland (BUGM) and grafted underneath the renal capsule of syngeneic male hosts. Following 1 month of in vivo growth, all tissue recombinants formed large masses of prostatic ductal tissue, which represented massive growth of the original population of prostatic epithelial cells. Examination of secretory protein expression in these tissue recombinants indicated that each mesenchyme influenced secretory function in the adult prostatic epithelium in a characteristic way. SVM maintained expression of DP-1 and probasin in prostatic ducts of DP, L1, and L2, which normally express these proteins. BUGM induced expression of C3 in prostatic ducts of the DP, L1, and L2, which normally do not express C3. UGM induced the expression of DP-1, probasin, and C3 in prostatic ducts from all dorsal-lateral lobes. Mesenchymal induction of massive epithelial growth, new ductal branching morphogenesis, and change in prostatic lobe identity are indicative of the presence of stem cells in adult prostatic epithelium because high proliferative capacity, tissue regeneration, and pluripotency (change in functional differentiation) are hallmarks of stem cells. © 1996 Wiley-Liss, Inc.     

Prostatic ductal system in rats: Regional variation in stromal organization

The rat prostate is composed of a complex system of branching ducts which terminate proximally at the urethra. It has been recognized that epithelial cells lining the ducts respond differently to androgen in various regions of the ducts, with responses ranging from proliferation to apoptosis, but the cellular mechanisms underlying these effects are unclear. Interaction between prostatic stroma and epithelium is essential to normal prostate growth and development, and the prostatic stroma is thought to be the first site of androgen action. Therefore we have examined the organization and distribution of stromal cell types along the rat prostatic ductal system. Using immunohistochemical techniques, we observed abundant fibrous tissue surrounding the distal region of the ducts, with a sparse, discontinuous smooth muscle layer. The intermediate region was surrounded by a continuous layer of smooth muscle one to two cells thick, which increased to greater than four layers thick at the proximal region. Fibrous tissue was located in interductal spaces and occasionally interspersed within the muscle layers in both regions. These observations indicate that regional variations in the distribution of stromal cell types exist and suggest that their corresponding secretory products could be responsible for the various effects of androgen on the epithelium in the rat prostatic ductal system. © 1996 Wiley-Liss, Inc.     

Stromal-epithelial interactions: II. Regulation of prostatic growth by embryonic urogenital sinus mesenchyme

Embryonic urogenital sinus mesenchyme (UGM) has been demonstrated previously to be a potent inductor of prostatic morphogenesis and functional differentiation when associated with either embryonic urogenital sinus epithelium (UGE) or urothelium derived from adult urinary bladder (ABLE) and grown in male hosts. To determine the role of mesenchyme in prostatic acinar growth, homotypic tissue recombinants of 16-day-old embryonic mouse urogenital sinus mesenchyme and epithelium (UGM_mouse + UGE_mouse) were prepared in which the relative amounts of UGM to UGE were varied from approximately 0.1:1 to 100: 1. Recombinants were grown for 1 month in intact male hosts after which the amount of acinar growth was assessed by histological analysis and by determination of wet weight and DNA content. The latter criteria are valid measures of acinar content of histologically normal prostatic tissue because the rodent prostate is composed of greater than 80% ductalacinar tissue. From this analysis the amount of acinar growth was found to be determined by the amount of mesenchymal tissue and was independent of the amount of epithelium utilized to prepare the tissue recombinants. Similarly, the magnitude of growth in heterospecific rat-mouse tissue recombinants prepared with urogenital sinus epithelium or adult bladder epithelium (ABLE) and urogenital sinus mesenchyme (UGM_mouse + UGE_rat, UGM_mouse + ABLE_rat UGM_rat + UGE_mouse, or UGM_rat + ABLE_mouse) is determined by the source of UGM. Although the initial DNA content per UGM is comparable between mouse and rat, the overall acinar growth induced by UGM_rat is about 10-fold greater than that induced by UGM_mouse when recombined reciprocally with UGE_mouse and UGE_rat, respectively. These results suggest that UGM is of fundamental importance as a regulator of prostatic epithelial growth. The relevance of this finding to the development of human benign prostatic hyperplasia is discussed.     

Prostate gland growth during development is stimulated in both male and female rat fetuses by intrauterine proximity to female fetuses

In rodents, steroid hormones are transported between adjacent fetuses, and male or female fetuses that develop in utero between female fetuses (2F males or 2F females) have higher serum levels of estradiol and lower serum levels of testosterone relative to siblings of the same sex that develop between two male fetuses (2M males or 2M females). The present study was prompted by the prior unexpected finding that as adults, 2F male mice have an enlarged prostate, and increased numbers of prostatic androgen receptors relative to 2M males. We examined prostate development in both male and female rat fetuses from different intrauterine positions using computer-assisted, 3-dimensional reconstruction of the urogenital complex. In males, this included the prostate, seminal vesicles and utricle (a remnant of the Müllerian ducts), while in females it included development of prostatic glandular buds. The mean cross-sectional area of developing prostatic epithelial buds, utricle and seminal vesicles was significantly increased in 2F male relative to 2M male fetuses. In female fetuses, prostatic bud development was significantly more likely to occur in 2F (67%) than in 2M (29%) animals. These findings suggest that the transport of a small supplement of estrogen from adjacent female fetuses enhances androgen-dependent accessory organ development. We also found that mRNAs encoding receptors for both estrogen and androgen were located in the mesenchyme of the developing male prostate. The localization of estrogen and androgen receptor mRNA in this region further suggests that the mesenchymal induction of prostatic epithelial growth involves both hormones. The cranial dorsolateral prostatic buds exhibited the greatest enlargement in 2F males. This region of the developing prostate in rats is comparable (that is the embryonic homologue) to the region exhibiting benign prostatic hyperplasia (BPH) during aging in men. We propose that the potential for pathological regrowth of the prostate during aging is imprinted by estradiol during fetal development.     

Androgenic induction of DNA synthesis in prostatic glands induced in the urothelium of testicular feminized (Tfm/Y) mice

It has been shown previously that wild-type urogenital sinus mesenchyme can induce the formation of prostate-like glandular structures in urinary bladder epithelium derived from adult Tfm (testicular feminization) mice. Total DNA synthesis within these tissue recombinants has been shown biochemically to be androgen sensitive. To determine which tissue (epithelium or stroma) accounts for this androgen-dependent DNA synthesis, an autoradiographic study was performed with tissue recombinants composed of rat wild-type urogenital sinus mesenchyme (UGM) associated with bladder epithelium from either wild-type (BLE) or Tfm mice (Tfm BLE). Both types of recombinants were grown under the kidney capsule of male athymic nude mice for 4 weeks. The hosts were then castrated, and 2 weeks later were treated with either testosterone propionate (TP), TP plus cyproterone acetate (CA), or oil vehicle for 3 days. DNA synthetic activity was measured through analysis of labelling index (LI) after incorporation of 3[H]-thymidine in vivo. For both UGM + BLE and UGM + Tfm BLE recombinants thymidine incorporation in epithelial cells greatly exceeded that of the stromal cells. TP stimulated epithelial LI to a similar degree (about 50- to 200-fold greater than controls) in both UGM + BLE and UGM + Tfm BLE recombinants; CA antagonized the effect of TP. Nuclear 3H-DHT binding was observed autoradiographically within the epithelial cells of the induced epithelium of UGM + wild-type BLE recombinants, but not within epithelium of UGM + Tfm BLE recombinants. Wild-type mesenchymal cells in both tissue recombinants showed specific nuclear 3H-DHT uptake. Thus, the proliferative effect of androgens upon prostatic epithelium is not a direct effect mediated by intra-epithelial androgen receptors, but rather it appears to be elicited indirectly via regulatory influences from androgen-receptor-positive stromal cells.     

前列腺导管系统远近端的细胞凋亡、雄激素受体亚型与雄雌激素环境研究

目的研究前列腺导管系统远、近端组织的细胞凋亡率、雄激素受体(AR)亚型表达及其雄、雌激素环境,以探讨诸因素在前列腺增长和前列腺增生(BPH)发病中的作用。方法按照前列腺的解剖学特征,分别切取正常前列腺导管系统远、近端组织10例。应用DNA末端原位标记的方法,对正常前列腺导管系统的远近端组织以及20例BPH标本进行了细胞凋亡率的研究,应用聚丙烯酰胺凝胶等电聚焦电泳(IEF)技术分析了相应组织的AR亚型表达状态,并检测了相应组织的双氢睾酮(DHT)和雌二醇(E2)水平和表皮生长因子受体(EGFR)含量。结果 正常前列腺导管系统远近端组织的DHT和E2差异无显著性,BPH组织中的E2含量(平均6.61 ng/g蛋白)略高于正常前列腺导管系统近端组织的含量3.13 ng/g蛋白,差异无显著性(P>0.05),而雄激素受体亚型在正常前列腺导管系统远近端和BPH组织中有明显不同的表达特征,同时正常前列腺导管系统远端组织的细胞凋亡率(41.2±3.5)％显著高于导管系统近端组织(29.2±4.0)％(P<0.05),后者非常显著高于BPH组织(3.9±1.1)％(P<0.001)。正常与增生前列腺组织内的DHT及E2含量与细胞调亡率之间无明显相关性。细胞调亡率与其组织的DHT、E2无明显相关性。结论前列腺导管系统的远近端上皮细胞结构形态生物学特性不同,其周围的间质亦有     

Normal and abnormal development of the male urogenital tract. Role of androgens, mesenchymal-epithelial interactions, and growth factors.

Androgen-dependent male urogenital development occurs via mesenchymal-epithelial interactions in which mesenchyme induces epithelial morphogenesis, regulates epithelial proliferation, and evokes expression of tissue-specific secretory proteins. Mesenchymal-epithelial interactions continue to be important into adulthood. For example, mesenchyme of the urogenital sinus (UGM) and seminal vesicle (SVM) induce dramatic morphologic and functional changes in various adult epithelia. Since adult epithelial cells are unquestionably responsive to mesenchymes that can elicit expression of alternative morphologic and functional phenotypes, established carcinomas might also be influenced by their connective tissue environment. In this regard, Dunning prostatic tumor has been induced by UGM or SVM to differentiate into tall columnar secretory epithelial cells. This change in cytodifferentiation is associated with a reduction in growth rate and loss of tumorigenesis. The role of soluble growth factors in the mechanism of mesenchymal-epithelial interactions is discussed.     

Morphologic and biochemical alterations in rat prostatic tumors induced by fetal urogenital sinus mesenchyme

Because fetal urogenital sinus mesenchyme (UGM) has been found to be highly inductive when recombined with normal adult prostate tissues or normal and neoplastic bladder epithelium, we investigated whether fetal UGM also interacts with established hormone-responsive and unresponsive rat Dunning and Nb prostate tumors. Our results indicate that: 1) fetal UGM acts directly on selected rat prostatic tumors by inducing histomorphologic changes (e.g., inducing acinar ductal structures and secretory activity) in the tumors toward more differentiated forms resembling that of the adult prostate gland; 2) fetal UGM either increased the growth rate of or maintained the sizes of three of the four interacting rat prostatic tumors; and 3) fetal UGM markedly reduced the lactate dehydrogenase activity of Nb-autonomous tumor toward a level comparable to that of the normal rat prostate gland. Our data suggest that fetal UGM can directly affect the growth and differentiative functions of selected rat prostatic tumors.     

The Androgen Cascade in Ageing Men: Blessing or Curse?

Dihydrotestosterone (DHT) is a dominant force in the development of the adult prostate. The action of DHT is critical in modulating the interaction of epithelial cells in the urogenital sinus mesenchyme during the organogenesis of the prostate. During adolescence, DHT is required to complete the normal growth phase of the prostate. In older men, if the response to DHT is altered, the resulting population of cells may be dominated by the transient proliferation of intermediate cells that are very sensitive to DHT for their ‘amplifying’ potential. In benign prostatic hyperplasia, these mechanisms are disturbed and the usual control of final stromal and epithelial cell mass is ineffective. The importance of the two isozymes of 5α reductase in regulating the continuing stromal:epithelial cell balance might provide a good scientific basis for moderating both pathways in an attempt to alter the clinical consequences of abnormal prostate growth.     

Immunolocalization of estrogen receptor alpha and beta in human fetal prostate

PURPOSE: We examined the immunolocalization of estrogen receptor (ER)alpha and ERbeta in the human fetal prostate. MATERIALS AND METHODS: Tissue sections from human fetal prostates at 7 to 22 weeks of gestation were stained with antibodies to ERalpha, ERbeta, and cytokeratin 10 and 14. RESULTS: ERalpha expression was not detected until 15 weeks of gestation with sparse staining in the utricle. By 19 weeks increased ERalpha expression was seen in the luminal cells of the ventral urogenital epithelium (UGE), basal cells of the dorsal UGE, utricle, distal periurethral ducts, peripheral stroma and posterior prostatic duct. K14 was detected in basal cells of the UGE and in several posterior acini. At 22 weeks ERalpha expression was more intense in all of these areas. ERbeta was expressed throughout the UGE, ejaculatory ducts, müllerian ducts and entire stroma at 7 weeks. Intense ERbeta staining was observed in these areas and in the prostatic buds by 8 weeks with persistent intense staining through 22 weeks. CONCLUSIONS: To our knowledge we report the first immunolocalization of ERalpha in the human fetal prostate and the earliest demonstration of ERbeta expression in the prostate at 7 weeks of gestation. ERbeta expression is intense during ductal morphogenesis, suggesting a role in normal glandular growth and proliferation. The induction of squamous metaplasia in the UGE, distal periurethral ducts and utricle is associated with ERalpha expression in these areas, while the induction of squamous metaplasia in peripheral prostatic acini is associated with peripheral stromal ERalpha expression. This study suggests estrogen signaling pathways in the human fetal prostate via ERalpha that involve epithelial-epithelial and epithelial-stromal interactions.     

Unopposed c-MYC expression in benign prostatic epithelium causes a cancer phenotype

BACKGROUND: We have sought to develop a new in vivo model of prostate carcinogenesis using human prostatic epithelial cell cultures. Human prostate cancers frequently display DNA amplification in the 8q24 amplicon, which leads to an increase in the copy number of the c-MYC gene, a finding that suggests a role for c-MYC in human prostate carcinogenesis. In addition overexpression of c-MYC in transgenic mouse models results in prostatic carcinogenesis. METHODS: We took advantage of the ability of retroviruses to integrate foreign DNA into human prostatic epithelium (huPrE) to generate cell lines that overexpress the c-MYC protooncogene. These cells were recombined with inductive rat urogenital sinus mesenchyme and grafted beneath the renal capsule of immunocompromised rodent hosts. RESULTS: The resultant tissue displayed a phenotype consistent with a poorly differentiated human prostatic adenocarcinoma. The tumors were rapidly growing with a high proliferative index. The neoplastic cells in the tumor expressed both androgen receptors (AR) and prostate-specific antigen (PSA), both characteristic markers of human prostate cancers. Microarray analysis of human prostatic epithelial cells overexpression c-MYC identified a large number of differentially expressed genes some of which have been suggested to characterize a subset of human cancers that have myc overexpression. Specific examples were confirmed by Western blot analysis and include upregulation of c-Myb and decreased expression of PTEN. Control grafts using either uninfected huPrE or using huPrE cells infected using an empty vector expressing a green fluorescent protein tag gave rise to well differentiated benign prostatic glandular ducts. CONCLUSIONS: By using a retroviral infection strategy followed by tissue recombination we have created a model of human prostate cancer that demonstrates that the c-MYC gene is sufficient to induce carcinogenesis.     

Growth factors as mediators of androgen action during the development of the male urogenital tract

Summary Studies on the developing prostate and SV suggest that androgens act via mesenchymal AR to elicit synthesis and secretion of various autocrine and paracrine factors that regulate epithelial and stromal growth and differentiation. Clearly, the global regulation of epithelial growth and ductal branching morphogenesis is a complex multifactorial process involving the interplay of many diffusible factors (both positive and negative regulators), extracellular matrix molecules, cell-surface receptors for growth factors, receptors for extracellular matrix molecules, and matrix-degrading enzymes. Future progress will certainly be dependent upon the utilization of appropriate, biologically relevant models to examine the respective roles of various growth factors in the growth and development of androgen target organs.Supported by NIH grants DK 32157, CA 59831, DK47517, DK 45861, and CA64872.     

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.     

Apoptosis and hormonal milieu in ductal system of normal prostate and benign prostatic hyperplasia

Aim: To study the apoptotic rate (AR) and the androgen and estrogen milieu in the proximal and distal ductal sys-tems of prostate, in order to help exploring the effects of these factors on prostatic growth and the pathogenesis of be-nign prostatic hypertrophy (BPH). Methods: The proximal and distal ends of the ductal system were incised from20 normal prostate as well as the hypertrophic prostate tissue from 20 patients with BPH. The AR was determined bythe DNA end-labeling method and dihydrotestosterone (DHT) and estrodiol (E_2), by radioimmunoassay. Results:There was no significant difference in DHT and E_2 density between the proximal and distal ends of the ductal systems innormal prostate. E_2 appeared to be higher in BPH than in normal prostatic tissues, but the difference was statistically in-significant. In normal prostatic tissue, the AR was significantly higher in the distal than in the proximal ends of theductal system (P<0.05), while the AR of the proximal ends was significantly higher (P <0.     

Correlation of embryonic development and adult neoplastic changes of human prostate

We have studied embryonic and fetal differentiation of the human prostate in relation to androgen-producing Leydig cell differentiation. We have studied the differentiation of human prostatic glands and the synthesis of acid phosphatase in vivo and in vitro. These studies have shown that the mesenchyme at the level of the openings of the para- and mesonephric ducts to the urethra was the local initiator of prostatic differentiation. All prostatic acini developed by epithelial outgrowths from the urethral epithelium. None of them grew from para- or mesonephric ducts. However, the epithelium on the colliculus seminalis differed from the rest of the urethral epithelium morphologically and in acid phosphatase content. Androgens accelerated differentiation in vitro and acid phosphatase activity was shown to be present in prostatic urethral epithelium and prostatic acini both in vivo and in vitro. According to these studies embryonic differentiation gives no direct answer to the localisation of adult neoplastic changes in different parts of the prostate, although in the posterior part there might be a mixture of cells from ductal and urethral epithelium. Secretion of acid phosphatase seems to be a constitutional phenomenon of this part of epithelium and is partly regulated by androgens. Epitheliomesenchymal interaction is important in differentiation and the role of this interaction in adult diseases might be valuable to be studied.