The etiology of benign prostatic hypertrophy

Benign prostatic hypertrophy (BPH) is a hyperplasia and not a hypertrophy. No cogent total explanation for the etiology of this ubiquitous disease has ever been given. There is such a vast cascade of incongruities in respect of hormonal influences, on the one hand, and the degree, variation, timing and rate of development of the condition, on the other hand, that a 'missing link' has constantly been envisaged in its etiology. In the search for this, two simple facts stand out: (a) BPH starts at some time after involution commences; (b) it is the transitional zone that is affected in the major extent. This hypothesis proposes that, owing to dynamic embryological differences between the transitional and the other zones, its secretions are differently affected by involution, resulting in stimulatory factors affecting known hormonal influences upon prostatic growth, further resulting in the development of BPH. These stimulatory factors are considered to be the 'missing link' in the etiology of BPH. It is further suggested that one of these stimulatory factors may be E. coli endotoxin, repeatedly released within a contained prostatic environment. This is considered secondary to intermittent colonization of the transitional zone acini and/or ducts by E. coli, followed by the destruction of these E. coli. This colonization is considered mandatory, if the known 95% occurrence of invasive infection of BPH is to be explained.

Epidermal growth factor receptor in mice and men--any applications to clinical practice?

The epidermal growth factor receptor (EGF-R) is perhaps the best studied member of tyrosine kinase receptors. Its inactivation by homologous recombination results in three different phenotypes ranging from peri-implantation lethality to postnatal lethality. The mildest form of EGF-R inactivation leads to epithelial immaturity and postnatal death due to respiratory failure and necrotizing enterocolitis-like lesions in the intestine. The defects seen in this 'postnatal lethality phenotype' manifest in the classical EGF-responsive organs (skin, intestine) and organs undergoing branching morphogenesis during development (lung, kidney, mammary gland, pancreas and prostate), and thus accord with the concept of EGF family members being important epithelial mitogens. The respiratory failure of the EGF-R (-/-) mice results from impaired branching of the alveolar tree and leads to decreased surface for gas exchange. Overall, the lung phenotype bears similarity to respiratory distress syndrome and bronchopulmonary dysplasia--the most common complications of prematurity in humans. Intestinal changes seen in the EGF-R (-/-) mice vary in severity, the end-point being severe mucosal lesions and necroses. These findings resemble those seen in necrotizing enterocolitis of premature babies, a serious intestinal problem in the neonate. Although deficient EGF-R function is not the reason for these prematurity-associated diseases it may nevertheless exacerbate them. Potential usage of EGF transforming growth factor-alpha in clinical work is discussed.

Hyaluronan is a prerequisite for ductal branching morphogenesis

Hyaluronan, a macromolecular carbohydrate polymer of the extracellular matrix is prominent early in embryogenesis, coinciding with rapid tissue growth. CD44, the predominant receptor for hyaluronan on vertebrate cells, is a variably expressed transmembrane glycoprotein. Mouse anterior prostate glands obtained at various postnatal time points were examined for the expression of hyaluronan and CD44. Reverse transcriptase polymerase chain reaction analysis was used to map the temporal regulation of specific CD44 variant isoforms. In each age group, hyaluronan was localized exclusively in the stromal matrix. Hyaluronan was greatly reduced in the later ages and was entirely absent around the developmentally quiescent proximal regions of the ducts. Early in prostate development, CD44 was prominent in the mesenchyme. However, in the later phases, CD44 expression became associated with membranes of epithelial cells. The role of hyaluronan-CD44 interactions in ductal branching morphogenesis was studied by serum-free organ culture of mouse anterior prostate. In the presence of optimal levels of testosterone, the organs underwent ductal branching morphogenesis. Treatment with either neutralizing anti-CD44 antibodies, hyaluronan hexasaccharides or the enzyme hyaluronidase inhibited androgen-stimulated ductal branching morphogenesis. These results are suggestive of the significant role played by hyaluronan-CD44 interactions in mediating androgen-induced prostatic growth and morphogenesis.

Inhibition of prostate ductal morphogenesis by retinoic acid

PURPOSE

To examine the effect of retinoic acid on prostate ductal morphogenesis.

MATERIALS AND METHODS

Newborn male Balb/C mice were injected with 25 mg./kg. all-trans retinoic acid or vehicle alone. Animals were sacrificed at 60 days of age and prostate ductal morphology was quantitatively assessed by microdissection. Total prostate DNA was quantitated by DPA assay.

RESULTS

The greatest effect was seen in the ventral prostate. Retinoic acid treated animals showed a 20% decrease in mean number of branch-points (p = 0.0006) with a corresponding 13% decrease in duct tips (p = 0.026). The combined ventral and dorsal prostate showed an effect with a 12% decrease in ductal branchpoints (p = 0.048). There was no effect on animal or organ weight and no effect on DNA content within the prostate. There was no difference in the prostate histology of treated and control animals.

CONCLUSION

Retinoic acid administration in the newborn period inhibits mouse prostate ductal morphogenesis. This effect appears independent of an inhibition of overall growth.

Abnormal prostate development in C3(1)-bcl-2 transgenic mice

BACKGROUND

Recent hypotheses to explain the etiology of abnormal growth associated with prostate disease have invoked perturbations in the rate of apoptosis as an important contributor to the onset and progression of these diseases. For this reason, the apoptosis suppressing oncoprotein bcl-2 has come under scrutiny with regards to its role in prostate diseases. In order to evaluate the role of bcl-2 in human prostate disease and to develop an animal model to test anti-bcl-2 therapies, we generated transgenic mice in which bcl-2 expression is targeted to the mouse prostate gland.

METHODS

Mouse embryos were microinjected with recombinant DNA constructed by fusing a modified rat C3(1) promotor element to cDNA encoding human bcl-2. Presence of the C3(1)-bcl-2 transgene in progeny was identified by Southern blot and polymerase chain reaction (PCR) analysis. RNase protection assays were used to analyze RNA from 15 organs of these mice. Western blot assays and immunohistochemical staining were used to confirm the tissue-specific protein expression of human bcl-2 and its cellular localization.

RESULTS

Three lines of C3(1)-bcl-2 transgenic mice were established. Founder mice carried 2-20 copies of the transgene. Expression of human bcl-2 from the transgene was limited to the prostate gland and testis of males as well as the uterus of females. In the prostate gland, human bcl-2 protein was found only in prostatic epithelial cells. Microscopic analysis of prostate glands from individual males (three lines) showed that these glands were often abnormal, with increased accumulation of cells in the prostatic stroma as well as the epithelium.

CONCLUSIONS

These transgenic mice appear to provide a novel animal model for studying neoplastic development of the prostate, with particular emphasis on the bcl-2 protein and the role of apoptosis regulation in such development.

Morphological analogies of fetal prostate stroma and stromal nodules in BPH

BACKGROUND

A "reawakening" of ontogenetic processes in the development of BPH is still in debate. Therefore, morphological analogies of fetal prostate stroma and nodular stromal proliferates in BPH were investigated.

METHODS

Fetal prostates (n = 30; weeks 12-40 of gestation) and stromal nodules of benign prostatic hyperplasia (n = 375 from autopsies, n = 100 from biopsies) were investigated by histo- and immunohistochemistry with special regard to cytoskeletal (alpha-actin, desmin, myosin, and vimentin), neuronal (S-100 protein), neuroendocrine (neuron-specific enolase), leukocytic (CD3, CD20, and CD68) and vascular (CD34, BMA-120, and factor VIII) antigens.

RESULTS

The developing fetal prostate stroma consists of immature mesenchymal cells up to week 17 of gestation, followed by fibroblastic and fibromuscular stromal cells up to week 25 of gestation and predominantly smooth-muscular cells until the end of gestation. Stromal nodules occur as immature mesenchymal, fibroblastic, fibromuscular, and smooth-muscular, suggestive of a maturational process. The fetal prostate stroma and the stromal nodules present, with an increasing degree of maturation, a similar vascular pattern and a similar occurrence of CD3 (T-lymphocytes), CD20 (B-lymphocytes), CD68 (macrophages), S-100, and neuron-specific enolase-positive cells.

CONCLUSIONS

The data suggest that ontogenetic processes are recapitulated in the development of stromal nodules in benign prostatic hyperplasia, supporting the idea of a "re-awakening" of fetal processes in BPH.

Immunohistochemistry of a prostate membrane specific protein during development and maturation of the human prostate

An antiserum against secretory vesicles from human seminal fluid (prostasomes) was used to study the localisation and distribution of the respective antigen(s) during prenatal development and pubertal maturation of the human prostate. The crude antiserum stained both secretory and membrane proteins in the adult prostate and other glands, such as pancreas and parotid gland. An immunoaffinity purified fraction from the antiserum selectively reacted with the apical plasma membrane of prostatic epithelium adluminal cells, recognizing a 100 kDa antigen (PMS). Even in the earliest stages of embryonic prostate specimens studied, the adluminal plasma membrane of the epithelial cells from developing glandular anlagen reacted strongly. The occurrence of PMS immunoreactivity in prostatic anlagen was directly correlated with lumen formation. As the antigen is an androgen-independently synthesised membrane protein of the prostate, it may possibly be used as a marker of cell polarity in the normal and pathologically altered prostate.

Male accessory sex organ morphogenesis is altered by loss of function of Hoxd-13

The role of the Hox gene Hoxd-13 in postnatal morphogenesis of the male accessory sex organs was examined by correlating the distribution and temporal regulation of expression in the accessory sex organs of postnatal mice with morphologic abnormalities of Hoxd-13-deficient transgenic mice. Previous studies of Hoxd-13 expression in the perinatal period have shown a broad domain of expression in the lower genitourinary tract, with expression in both mesenchyme and epithelium; focal expression was also noted in the epithelium of the nascent ducts of the developing prostate. Quantitative RT-PCR studies of Hoxd-13 expression in the 5 day mouse confirm widespread expression in the accessory sex organs developing from both the Wolffian duct and the urogenital sinus. Expression is down-regulated with age, and a detailed time course of expression in the developing prostate shows that the level of Hoxd-13 expression correlates with morphogenetic activity in the development of the prostate ductal system. Transgenic Hoxd-13-deficient mice display multiple abnormalities in the male accessory sex organs. The most severe abnormalities were observed in organs exhibiting ductal branching during postnatal development and included diminished mesenchymal folding in the seminal vesicles, decreased size and diminished ductal branching in the ventral and dorsal prostate, and agenesis of the bulbourethral gland. We conclude that Hoxd-13 expression in the postnatal period correlates with a period of intense morphogenetic activity in accessory sex organ development and that the function of Hoxd-13 is evidenced by morphologic abnormalities in accessory sex organs of the Hoxd-13-deficient mutant.

Prostate enlargement in mice due to fetal exposure to low doses of estradiol or diethylstilbestrol and opposite effects at high doses

On the basis of results of studies using high doses of estrogens, exposure to estrogen during fetal life is known to inhibit prostate development. However, it is recognized in endocrinology that low concentrations of a hormone can stimulate a tissue, while high concentrations can have the opposite effect. We report here that a 50% increase in free-serum estradiol in male mouse fetuses (released by a maternal Silastic estradiol implant) induced a 40% increase in the number of developing prostatic glands during fetal life; subsequently, in adulthood, the number of prostatic androgen receptors per cell was permanently increased by 2-fold, and the prostate was enlarged by 30% (due to hyperplasia) relative to untreated males. However, as the free serum estradiol concentration in male fetuses was increased from 2- to 8-fold, adult prostate weight decreased relative to males exposed to the 50% increase in estradiol. As a model for fetal exposure to man-made estrogens, pregnant mice were fed diethylstilbestrol (DES) from gestation days 11 to 17. Relative to controls, DES doses of 0.02, 0.2, and 2.0 ng per g of body weight per day increased adult prostate weight, whereas a 200-ng-per-g dose decreased adult prostate weight in male offspring. Our findings suggest that a small increase in estrogen may modulate the action of androgen in regulating prostate differentiation, resulting in a permanent increase in prostatic androgen receptors and prostate size. For both estradiol and DES, prostate weight first increased then decreased with dose, resulting in an inverted-U dose-response relationship.

The influence of the anti-androgen flutamide on early sexual differentiation of the marsupial male

The development of the prostate and the normal descent of the testes in the tammar wallaby (Macropus eugenii) were influenced by treatment with the non-steroidal anti-androgen flutamide. Male pouch young were treated daily from day 9 to day 45, or from day 20 to day 45, of pouch life. Prostate development was inhibited in both treatment groups to a similar extent. Since prostatic buds do not form until day 25 of pouch life, these results suggest that there is a window of androgen sensitivity operating between day 20 and day 25 of pouch life. The number of prostatic buds was significantly lower, but despite the duration of treatment there was never complete abolition of prostate development. Although testes had descended to the same position in treated and control pouch young, inguinal hernias developed in three of four animals treated with flutamide from day 9. These data demonstrate that virilization of the male reproductive tract in this marsupial is dependent on a relatively brief exposure to androgens. Blocking androgen receptor action interferes with normal development of the inguinal canal, which suggests that it is this aspect of inguinoscrotal testicular descent that is androgen dependent.

[Prostatic bud induction by brief treatment with growth factors]

Effects of brief treatment of growth factors on the urogenital sinus of embryonic rats were investigated and it was found that 8 hour-treatment in the beginning of 5-day cultivation with the epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) can provoke prostatic bud formation, in the medium deprived of androgens.

Von Hippel-Lindau tumour suppressor gene. Localization of expression by in situ hybridization

Inactivation of the von Hippel-Lindau (VHL) tumour suppressor gene is responsible not only for VHL disease, but also for sporadic renal cell carcinoma and cerebellar haemangioblastoma. The distribution of VHL gene expression in the mouse embryo was recently studied by in situ hybridization, along with human VHL in 14-week-old fetal kidney: there was widely distributed expression in the former and expression in the tubules and blastema in the latter. Adult human tissue and other fetal organs were not examined. The present paper describes an in situ hybridization study to assess the function of the VHL gene in adult human tissues and in tissues of human fetus at 28 weeks of gestation. The expression of the VHL gene was limited to the adult and fetal brain and kidney, and the adult prostate. Nerve cells in adult and fetal brain were positive, including the cerebellar Purkinje cells. In adult and fetal kidney, the proximal tubular epithelium, the putative origin of the common type of renal cell carcinoma, showed intense signal, whereas the distal nephron, glomeruli, and nephrogenic blastema showed no significant signal. The prostate showed significant signal in the basal epithelium. The adrenal, pancreas, and epidydimis showed no significant signal, in spite of the frequent occurrence at these sites of neoplastic or hamartomatous lesions in VHL disease.

Effect of prostatic growth factor, basic fibroblast growth factor, epidermal growth factor, and steroids on the proliferation of human fetal prostatic fibroblasts

To study the relationship between androgen metabolism and the pathogenesis of benign prostatic hypertrophy, we purified a growth factor from benign hyperplastic tissue of human prostates and assayed the proliferative responses of human fetal prostatic fibroblasts to the purified growth factor (hPGF), basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), dihydrotestosterone (DHT), and estradiol (E2). Prostatic tissue extracts were fractionated using heparin-Sepharose chromatography. The fraction that eluted with 1.3-1.7 M NaCl contained the majority of mitogenic activity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS/PAGE) of the lyophilyzed active fraction showed a band at 17,000 daltons. Human prostatic fibroblasts were isolated from fetal prostate and tested for their proliferative responses to hPGF, bFGF, EGF, DHT, and E2. hPGF, as well as bFGF and EGF, did increase tritiated thymidine incorporation into the cultured fibroblasts. DHT(10(-7) M) had a significant stimulatory effect on cell growth in serum-free media after 6 days of culture. E2(10-7 M) had no effect on cell proliferation. The combination of DHT and E2 showed no synergistic effect. We conclude that our purified hPGF, bFGF, and EGF promote cell growth directly, DHT indirectly, while E2 does not. The effect of DHT appears to be mediated via the increased production and/or secretion of growth factor(s). Possibly, the bFGF-like hPGF purified from human benign hyperplastic prostatic tissue is such a mediator.

Androgen regulation of the rat keratinocyte growth factor (KGF/FGF7) promoter

Keratinocyte Growth Factor (KGF/FGF7) is a candidate andromedin in normal embryonic development of male accessory sex glands, such as the prostate and seminal vesicles. The expression of KGF mRNA and protein is androgen-responsive. To elucidate the regulation of expression of the KGF gene, we isolated the first two exons of the KGF gene and approximately 15 kb upstream sequences. The major transcription start site was mapped. It is preceded by a CAAT-box and a TATA-box. Transient transfections in LNCaP cells revealed that, upon treatment with the synthetic androgen R1881, KGF promoter activity is upregulated 6 to 11 fold, indicating androgen regulation of the KGF promoter in the region from position - 900 to -1200. The longest construct (BH-pLuc: -4700 to +901) has a much higher basal activity than the shorter constructs, indicating that in the region -4700 to -2700 additional activating sequences are present.

Expression of the homeotic gene Hox-d13 in the developing and adult mouse prostate

PURPOSE

To examine expression of the homeotic gene Hox-d13 in the developing mouse prostate.

MATERIALS AND METHODS

Expression was assayed by Northern analysis, reverse-transcriptase polymerase chain reaction and in situ hybridization.

RESULTS

Expression is present in the urogenital sinus in late gestation and is localized postnatally in the urethral epithelium and prostatic ducts. Expression continues throughout development and persists in the adult prostate.

CONCLUSION

A restricted domain of Hox-d13 expression in the developing urogenital tract is consistent with the role of the Hox genes in specifying regional identity during development. Expression in the prostate postnatally suggests additional roles in prostate ductal morphogenesis and/or cell differentiation.

Epithelial development in the rat ventral prostate, anterior prostate and seminal vesicle

The prostate and seminal vesicle (SV) are androgen-dependent secretory glands of the male genital tract. The epithelial cells of these glands produce the bulk of the seminal secretions. The objective of the present study was to examine the ontogeny of cytokeratin and androgen receptor (AR) expression in the rat SV, anterior prostate (AP) and ventral prostate (VP). The study utilized organ culture to examine the effects of androgens on the development of these markers and castration of adult rats to examine androgenic effects on their maintenance. Tissues were examined from 14 days of gestation to adulthood. The SV was a tubular organ from its inception while the prostate formed from solid epithelial cords. These prostatic buds canalized in a proximal to distal manner starting at day 1 postnatal in the VP and day 5 in the AP. The expression of cytokeratins and AR was visualized by immunocytochemistry. In all three glands keratins 5, 7, 8, 14, 18 and 19 were initially uniformly expressed in all epithelial cells. In the SV, segregation of cytokeratins between the luminal and basal cell types started at 4 days postnatally with keratin 7 localizing to basal cells. Five days after birth, keratins 5 and 14 were also localized to the basal epithelium, while keratins 8 and 18 were only expressed by luminal cells, Keratin 19 was expressed in all epithelial cells throughout development and into adulthood. In the VP and AP the same pattern of cytokeratin segregation occurred as in the SV. Epithelial differentiation occurred in a proximal to distal fashion in the prostate. In the proximal VP ducts keratins 7 and 14 were basally localized by 2 days postnatally, while keratin 5 did not clearly segregate to basal cells until day 9 after birth. In the AP keratin 14 was basally localized by 1 day postnatal but keratin 5 and 7 did not colocalize to the basal cells until days 9 and 12, respectively. AR were expressed in the epithelium of the urogenital sinus from 19 days of gestation. At 19 and 20 days of embryonic development AR-negative prostatic buds were seen emerging from the AR-positive urogenital sinus epithelium. By birth AR were detectable in the epithelium of both prostatic lobes and the SV. The role of androgens in the development of the prostatic and SV epithelium was investigated in a serum-free organ culture system. These experiments showed that differentiation of prostatic and SV luminal and basal epithelial cell types was accelerated as compared to the in vivo situation in the presence of androgens, and did not occur in their absence. Following castration of adult animals the prostate and SV regressed with preferential loss of luminal epithelium. The relative numbers of basal cells was increased, though some flattened cells expressing a luminal cell pattern of cytokeratins were still observed. AR were detected in the prostatic and SV epithelium of long-term castrated animals. In summary, the rat prostate was found to be derived from undifferentiated solid epithelial cords. Canalization occurred concurrent with the differentiation of clear epithelial subtypes. Epithelial AR were expressed from around the time of birth and expression levels increased with age. The SV was canalized from its inception but likewise was derived from an undifferentiated epithelial precursor.

Smooth muscle-epithelial interactions in normal and neoplastic prostatic development

A hypothesis is proposed that unifies prostatic developmental biology and carcinogenesis. The foundation of this hypothesis is the reciprocal interaction of epithelium and mesenchyme during prostatic development followed thereafter by a reciprocal homeostatic interaction of epithelium and smooth muscle in adulthood. This smooth muscle-epithelial cell interaction is perturbed during prostatic carcinogenesis with adverse sequelae for both epithelium and smooth muscle. The following sequence of events is proposed to occur: (1) Under the influence of androgens, urogenital sinus mesenchyme (UGM) induces urogenital sinus epithelium to undergo prostatic ductal morphogenesis and differentiation. (2) As prostatic epithelium differentiates, it in turn signals the UGM to differentiate into smooth muscle cells that closely surround the epithelial ducts. Differentiation of prostatic smooth muscle requires both an inductive signal from epithelium and androgens. (3) Once formed, prostatic smooth muscle participates in reciprocal homeostatic interactions. We propose that prostatic smooth muscle under the influence of androgens signals to prostatic epithelium to maintain epithelial differentiation and to repress epithelial proliferation, while prostatic epithelium signals to prostatic smooth muscle to maintain smooth muscle differentiation. In adulthood, homeostasis is maintained through reciprocal interactions between smooth muscle and epithelial cells with minimal proliferation of either cell type. Prostatic carcinogenesis, which is initiated following genetic damage to prostatic epithelium, is surmised to involve a sequential disruption in these reciprocal homeostatic interactions with ensuing dedifferentiation of both the emerging prostatic carcinoma cells and smooth muscle. Thus, following genetic insult to prostatic epithelium the epithelium fails to signal appropriately to the smooth muscle, which then begins to dedifferentiate. As smooth muscle differentiation begins to deviate, signaling from prostatic smooth muscle to prostatic epithelium becomes anomalous resulting in progressive loss of control over epithelial differentiation and proliferation. During progression of prostatic carcinogenesis a vicious cycle is established in which both prostatic epithelium and smooth muscle dedifferentiate. This hypothesis is based on the ontogeny of prostatic smooth muscle differentiation during development and by the fact that the amount of smooth muscle progressively diminishes in human prostatic adenocarcinomas during progression from low- to high-grade cancers. Finally, in experimental tissue recombinants in which various normal or neoplastic prostatic epithelia were grown in combination with embryonic rat UGM, only normal (non-neoplastic) epithelia were capable of inducing differentiation of prostatic smooth muscle in UGM. Based on several lines of evidence, it is now apparent that smooth muscle-epithelial interactions are the operative cell-cell interaction in the postnatal prostate which plays a key role in regulating epithelial differentiation, proliferation and carcinogenesis.

Distinct transcripts are recognized by sense and antisense riboprobes for a member of the murine HSP70 gene family, HSP70.2, in various reproductive tissues

The expression of hsp70.2, an hsp70 gene family member, originally characterized by its high levels of expression in germ cells in the adult mouse testis, was detected in several other reproductive tissues, including epididymis, prostate, and seminal vesicles, as well as in extraembryonic tissues of mid-gestation fetuses. In addition, hybridization with RNA probes transcribed in the sense orientation surprisingly indicated the presence of slightly larger "antisense" transcripts in several tissues. The levels of antisense transcripts varied among the tissues, with the highest signal detected in the prostate and no signal being detectable in the testis. Consistent with these results, in situ hybridization analysis clearly localized the sense-orientation transcripts to pachytene spermatocytes, while no antisense-orientation transcripts were observed in adjacent sections of the same tubules. Our findings have thus shown that although hsp70.2 was expressed abundantly and in a highly stage-specific manner in the male germ line, it was also expressed in other murine tissues. Furthermore, we have made the surprising observation of antisense transcription of the hsp70.2 gene in several mouse tissues, revealing another level of complexity in the regulation and function of heat shock proteins.

The 5 alpha-reductase system and its inhibitors. Recent development and its perspective in treating androgen-dependent skin disorders

5 alpha-Reductase, the enzyme system that metabolizes testosterone into dihydrotestosterone, occurs in two isoforms. The type 1 isozyme is composed of 259 amino acids, has an optimal pH of 6-9 and represents the 'cutaneous type'; it is located mainly in sebocytes but also in epidermal and follicular keratinocytes, dermal papilla cells and sweat glands as well as in fibroblasts from genital and non-genital skin. The type 2 isozyme is composed of 254 amino acids, has an optimal pH of about 5.5 and is located mainly in the epididymis, seminal vesicles, prostate and fetal genital skin as well as in the inner root sheath of the hair follicle and in fibroblasts from normal adult genital skin. The genes encoding type 1 and type 2 isozymes are found in chromosomes 5p and 2p, respectively, and each consists of 5 exons and 4 introns. During the last decade, several steroid analogues and non-steroid agents have been developed to interfere with 5 alpha-reductase activity. Finasteride, which has a higher affinity for the type 2 isozyme, is the first 5 alpha-reductase antagonist clinically introduced for treatment of benign prostate hyperplasia. The clinical evaluation of finasteride or other 5 alpha-reductase inhibitors in the field of dermatology has been very limited; in particular, those that selectively bind to type 1 isozyme (e.g. MK-386, LY191704) may be regarded as candidates for treatment of androgen-dependent skin disorders such as seborrhoea, acne, hirsutism and/or androgenetic alopecia.

Stromal development in the ventral prostate, anterior prostate and seminal vesicle of the rat

The prostate and seminal vesicle (SV) are androgen-dependent secretory glands of the male genital tract. They produce the bulk of the seminal secretions. The object of the present study was to examine and document the ontogeny of stromal maturation in the rat anterior and ventral prostate and SV. These organs have a loosely organized cellular mesenchyme during fetal development. During prostatic development the mesenchyme condensed to form smooth muscle sheaths immediately surrounding the epithelium, with looser connective tissue between individual ducts. In the SV, a loose connective tissue layer called the lamina propria lies between the epithelium and developing muscle. Smooth muscle alpha-actin, myosin, desmin, laminin, vinculin, vimentin and androgen receptor (AR) expression were examined by immunocytochemical methods during the pre- and postnatal developmental periods. The first marker to be detected was vimentin, which was initially found throughout the mesenchyme. During development vimentin became mostly restricted to the interductal tissue of the prostate and the lamina propria of the SV. Smooth muscle markers were expressed in an orderly sequence in a proximal to distal manner along prostatic ducts, from the urethra towards the tips. Expression of alpha-actin was followed by vinculin, myosin, desmin, and laminin. These markers became localized to the developing smooth muscle sheaths and were not expressed in the interductal tissue of the prostate or the lamina propria of the SV. Organ culture experiments demonstrated that androgens were required for the differentiation of smooth muscle sheaths. Castration of adult rats demonstrated that androgens were required to maintain smooth muscle differentiation. In castrates, the stroma was relatively thicker but less dense than in intact animals. Following castration, expression of the smooth muscle markers was lost sequentially in the reverse order of their expression during development. In long-term castrates alpha-actin, vimentin and a small amount of vinculin were detected. AR were first detected in the urogenital sinus mesenchyme immediately surrounding the epithelium at 16 days of gestation. As development progressed expression of AR became more widespread, and postnatally was found throughout the mesenchyme. As maturation of smooth muscle occurred, stromal expression of AR became localized to the muscular sheath immediately surrounding the epithelium. In the prostate the interductal connective tissue displayed very low levels of AR expression. In the SV, AR were also observed in the lamina propria. In summary, stromal differentiation and dedifferentiation in the rat prostate and SV were found to be androgen-dependent processes with ordered sequential ontogenic expression of specific markers.

Development of nerves containing nitric oxide synthase in the human male urogenital organs

OBJECTIVE

To determine the spatial and temporal distribution of nitric oxide synthase (NOS) in the urogenital organs of a series of human male fetuses, using an immunohistochemical technique.

MATERIAL AND METHODS

Thirteen pre-natal specimens ranging in gestational age from 13 to 30 weeks were acquired following abortion or miscarriage. The distribution of NOS, which catalyses the production of nitric oxide (NO), was revealed using an indirect immunolabelling technique and compared with the overall innervation of each specimen visualized using the general nerve-marker protein gene product 9.5 (PGP).

RESULTS

At 13 weeks of gestation the majority of nerves supplying the developing prostate gland expressed NOS while similar nerves formed a very minor proportion of the total innervation to the urinary bladder and intramural ureters. With increasing gestational age, NOS-containing nerves became more numerous in the lower urinary tract, the majority occurring at the bladder neck and around the prostatic urethra. In contrast, NOS-containing nerves were not detected in the muscle coat of the vas deferens and seminal vesicle until 23 weeks of gestation and at 30 weeks still only formed a small proportion of the intramuscular nerves. From 23 weeks onwards NOS-containing nerves were present occasionally in the dense subepithelial nerve plexuses which developed in the bladder, prostate, vas deferens and seminal vesicle. Also from 23 weeks onwards, many of the epithelial cells lining the vas deferens, seminal vesicle and ejaculatory ducts showed immunoreactivity to NOS but no immunoreactivity was observed in the epithelial lining of the urinary bladder and the intramural ureters.

CONCLUSION

Based on the comparative density of NOS-containing nerves and the difference in their temporal development among the various urogenital organs it is apparent that NO plays an increasingly important role in the autonomic control of the lower urinary tract during fetal development but that its involvement in the functional control of the vas deferens and seminal vesicle is relatively minor before birth.

Expression of the type 1 and 2 steroid 5 alpha-reductases in human fetal tissues

Androgens play a key role in human fetal development. Therefore, it is important to understand the distribution of the isozymes of 5 alpha-reductase, the enzyme that converts testosterone to the more potent androgen, dihydrotestosterone. The expression of the two isozymes of 5 alpha-reductase was studied in human fetal skin and fetal prostate by measuring the in vitro enzyme activity in crude preparations. Low levels of the type 1 5 alpha-reductase were found in fetal scalp and back skin. Studies with fetal prostate samples confirmed that the type 2 enzyme is expressed in levels similar to those found in adult tissues. These results provide the first evidence that both isozymes of 5 alpha-reductase are expressed during human fetal development.

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

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.

Development of peptide-containing nerves in the human fetal prostate gland

Immunohistochemical methods were used to study the developing peptidergic innervation of the human fetal prostate gland in a series of specimens ranging in gestational age from 13 to 30 wk. The overall innervation of each specimen was visualised using protein gene product 9.5 (PGP), a general nerve marker. The onset and development of specific neuropeptide-containing subpopulations were investigated using antisera to neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), bombesin (BOM), somatostatin (SOM), leu-enkephalin (l-ENK) and met-enkephalin (m-ENK). In addition the occurrence and distribution of presumptive noradrenergic nerves was studied using antisera to dopamine-beta-hydroxylase (D beta H) and tyrosine hydroxylase (TH). At 13 wk numerous branching PGP-immunoreactive (-IR) nerves were observed in the capsule of the developing prostate gland and surrounding the preprostatic urethra but the remainder of the gland was devoid of nerves. The majority of nerves in the capsule contained D beta H and TH and were presumed to be noradrenergic in type while other nerves (in decreasing numbers) contained NPY, l-ENK, SP and CGRP. Nerves associated with the preprostatic urethra did not contain any of the neuropeptides under investigation. At 17 wk the density of nerves in the capsule had increased and occasional m-ENK-, VIP- and BOM-IR nerve fibres were also observed. In addition PGP, D beta H-, TH-, NPY- and l-ENK-IR nerves occurred in association with smooth muscle bundles which at 17 wk were present in the outer part of the gland. Occasional PGP-IR nerves were also present at the base of the epithelium forming some of the prostatic glands. At 23 wk some of the subepithelial nerves showed immunoreactivity for NPY, VIP or l-ENK. At 26 wk smooth muscle bundles occurred throughout the gland and were richly innervated by PGP, D beta H and TH-IR nerves while a less dense plexus was formed by NPY- and l-ENK-IR nerves together with a few m-ENK-IR nerves. Occasional smooth muscle-associated varicose nerve fibres showed immunoreactivity for SP, CGRP, VIP or BOM although the majority of these types of nerve formed perivascular plexuses. Also at 26 wk numerous varicose nerve fibres were observed in association with the prostatic acini, the majority of such nerves containing NPY with a few showing immunoreactivity to VIP, l-ENK, SP or CGRP.(ABSTRACT TRUNCATED AT 400 WORDS)