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. 2002 Aug;201(2):173–183. doi: 10.1046/j.1469-7580.2002.00079.x

Transforming growth factor-beta 2 heterozygous mutant mice exhibit Cowper's gland hyperplasia and cystic dilations of the gland ducts (Cowper's syringoceles)

Nicole Dünker 1, Gerhard Aumüller 2
PMCID: PMC1570906  PMID: 12220125

Abstract

Analyses of mutant mice with a deletion for the transforming growth factor beta 2 (Tgfβ2) gene revealed cysts in the perineal/scrotal region of male mice. We present evidence from in situ, light and electron microscopy that the cysts observed in Tgfβ2+/− heterozygous mice males derive from Cowper's glandtissue. The Cowper's glands of Tgfβ2+/− heterozygous mutant mice display all steps of glandular hyperplasiaand cystic dilation. TGF-β isoforms and TGF-β receptor (TβR-II) were localized immunocytochemicallyin sections of Cowper's glands. TGF-ββ2 and TGF-β3 were located predominantly inmyoepithelial cells of the Cowper's gland whereas the TβRII was found in the plasma membrane of the acinar cells. TUNEL-assays revealed that apoptotic cell death is significantly reduced in Cowper's glands of Tgfβ2+/− heterozygous mutant mice. The fact that Tgfβ2+/− heterozygous mutant mice exhibit hyperplasia of Cowper's gland epithelium and Cowper's gland cysts suggests a disturbance of epithelial–stromal interaction mostlikely due to reduced TGF-β2 level, accompanied by a significant decrease in apoptosis.

Keywords: apoptosis, development, proliferation, reproductive tract, TGF-β

Introduction

Seminal plasma is a complex fluid originating from several sex accessory organs as the seminal vesicles, prostate, urethral, and bulbourethral (Cowper's) gland. In humans, emission is initiated by the bulbourethral or Cowper's glands that discharge their secretions into the so-called ‘presperm fraction’ of the ejaculate (Sirigu et al. 1993). Bulbourethral or Cowper's glands,which are present in the majority of mammals, usually appear as a single pair of multilobular tubular or tuboalveoloar glands. They are situated in the urogenital diaphragm deep to the bulb of the penis between the ischiocavernosus and the bulbocavernosus (bulbospongiosus) muscles, embedded within the deep transverse perineal muscle, and form part of the pelvic floor. The ducts of the Cowper's glands join and enter the posterior urethra (pars spongiosa; Rauther, 1904; Franks, 1967). In rodents the bulbourethral gland produces a mucous secretion thought to play a role during formation of the copulatory plug.

Bulbourethral glands are first identifiable in mice at embryonic (E) day E17.5 and epithelial branching normally starts at postnatal (P) day P1 (Cook et al. 1987). During development, bulbourethral glands arise as epithelial outgrowths of the endodermal urogenital sinus invading the condensed mesenchyme flanking the primitive urethra. During subsequent development the epithelium branches extensively, filling the mesenchymal capsule and giving rise to the highly arborized ductal system of the mature organ.

In adults, the bulbourethral glands consist of numerous acini of tall columnar epithelial cells which nearly fill the lumen. Glandular lobules are divided by connective tissue septa and the whole gland is surrounded by a connective tissue capsule and embedded in a thick layer of striated skeletal muscle. The acini of the mucinproducing Cowper's glands consist of mucous-like epithelial cells with basal nuclei, whereas the ducts are lined with a single layer of cuboidal cells (Rauther, 1904; Frank, 1967; Sirigu et al. 1993). Small amounts of stromal and smooth muscle cells surround the periphery of each acinus. A striking feature of bulbourethral glands of hamsters and rats is the large number of secretory vacuoles showing filamentous or reticular texture (Flickinger, 1974; Parr et al. 1993) and prominent Golgi complexes (Parr et al. 1993).

Only a few studies report the ultrastructural features of the human bulbourethral glands (Riva et al. 1988, 1990). These showed that the parenchyma of the Cowper's glands consists of (a) secretory tubules and alveoli lined by typical mucoid cells at different stages of secretory cycle, and (b) an excretory duct system. Secretory elements were also observed in the ducts, marked by the presence of secretory small dark granules in the cytoplasm (Riva et al. 1988).

Stromal–epithelial interactions play a critical role in the developmental regulation of the prostate (Blanchère et al. 2001) and probably also in Cowper's gland development. The expression of transforming growth factors beta TGF-βs starts early in development. Marked TGF-β expression is generally observed in areas undergoing morphogenetic events, for instance those involving epithelial-mesenchymal interactions or differentiation (Heine et al. 1987). Gene ablation studies revealed that TGF-β seems to be actively involved in these interactions (Dünker & Krieglstein, 2000).

TGF-βs exist in three highly homologous isoforms, TGF-β1, -β2 and -β3, which elicit their cellular responses by signalling via specific type I and type II receptors (TβR-I, TβR-II; Roberts & Sporn, 1990; Massague & Chen, 2000). TGF-βs exert a wide range of biological responses on a variety of cells belonging to different organ types. They are involved in the regulation of proliferation, differentiation, development of many tissues and extracellular matrix formation (Dünker & Krieglstein, 2000). In vivo evidence confirming TGF-β's role in endogenous regulation of cell proliferation comes from a study in chick embryos (Combs et al. 2000). As discovered most recently, TGF-β also mediates apoptosis (Krieglstein et al. 2000; Dünker et al. 2001, 2002).

A transgenic TGF-β mouse model was used to investigate phenotypic changes of the Cowper's gland in Tgfβ2+/− heterozygous mice in which cystic dilatations of the gland ducts were observed.

Materials and methods

Animals

Tgfβ2+/– heterozygous mice were offspring from breeding pairs kindly provided by T. Doetschman, University of Cincinnati (OH, USA). The generation of these strains is described elsewhere (Sanford et al. 1997). Heterozygous Tgfβ2+/– mutant mice were analysed because homozygous Tgfβ2–/– mice die at or around birth when the accessory sex organs are not yet fully developed. For morphological comparison in each case Tgfβ2+/+littermates of the respective mutants were used as wild-type controls.

Morphological studies

Cowper's glands and cysts were collected from animals at different ages, fixed in Bouin's fixative (75% picric acid, 25% formaldehyde, and 5% glacial acetic acid) for several hours, dehydrated in a graded series of ethanol concentrations and embedded in paraffin wax. The morphology of the bulbourethral gland and the cysts were studied in haematoxylin and eosin (HE)-stained histological paraffin sections (10 µm) of transgenic and wild-type mice.

Immunocytochemistry

Sections were deparaffinized and heated for 5 min in citrate buffer (pH 6) in a microwave oven at 600 W to improve antigen retrieval. Sections were pre-incubated with 10% normal goat serum (NGS) in phosphate-buffered saline (PBS; pH 7.4) containing 0.3% Triton-X 100 for 1 h. Immunostaining was performed using isoform-specific anti-TGF-β, or anti-TGF-β receptor (TβR) antibodies (TGF-β2, sc-90; TGF-β3, sc-82; TβR-II, sc-400; Santa Cruz) at dilutions of 1: 100 to 1: 200. Sections were incubated with the primary antibodies overnight at room temperature. The reaction was visualized using a Cy3-conjugated goat antirabbit IgG secondary antibody (MoBiTec, 1: 1000 in 10% NGS/PBS/Triton-X 100).

As controls, in all cases PBS was substituted for the primary antisera in order to test for non-specific labelling. No specific cellular staining was observed when the primary antiserum was omitted. Additionally, the specificity of the primary antibodies was tested and confirmed by Western blots (data not shown).

TUNEL staining

Cell death was detected by TUNEL staining. Paraffin sections (10 µm) were deparaffinized and stained with in situ cell-death detection kit (Roche; cat. no.: 1684795). In brief, sections were treated with the TUNEL reaction mixture (including fluorescein-dUTP) and incubated in the dark for 1.5 h at 37 °C, followed by washes in PBS. Incorporated fluorescein was detected by a sheep antifluorescein antibody, conjugated with horseradish peroxidase (POD). The substrate reaction was visualized with nickel-intensified DAB. Apoptosis was quantified by counting TUNEL-positive cells in five random visual fields at 40× magnification.

Electron microscopy

For electron microscopy transcardiac perfusion fixation was performed via the left ventricle after flushing the blood with physiological sodium chloride solution containing heparin (0.1% heparin, 25 000 units) and procain hydrochloride (0.1%). Animals were perfused with fixative consisting of 0.1% glutaraldehyde, 5.0% p-formaldehyde and 1.0% CaCl2 diluted in 0.1 M sodium cacodylate buffer (pH 7.3).

Tissue samples were stored at 4 °C in the respective fixative for an additional 12 h. Half of the samples were then treated with reduced osmium solution for 1 h, and the rest remained untreated. Samples were dehydrated in graded ethanol concentrations and immersed in a mixture of propylene oxide and Epon 812. The final polymerization was performed at 60 °C for 12 h in pure Epon.

For morphological studies, 1-µm-thick semithin sections were cut, mounted on glass slides and stained with alkaline toluidine blue-pyronin solution or methylene blue-fuchsin solution (Böck, 1984). Ultrathin sections were collected on uncoated nickel grids and stained with ethanolic uranyl acetate solution.

Results

Cysts in situ

In contrast to Tgfβ2−/– homozygous mutant mice dying perinatally and exhibiting multiple developmental defects (Sanford et al. 1997), Tgfβ2+/– heterozygous mutants are viable and fertile. Some Tgfβ2+/– heterozygous males develop cysts palpable in the perineal/scrotal region. Nine cysts were found in a total of 21 TGFβ2+/– heterozygous males investigated. In animals at all stages studied 1–2 cysts were found in each animal. The youngest male was 1 month old and carried a small perineal nodule-like structure which did not look like a cyst. Following upon the development of the cysts we found small, externally non-visible cysts in 2- and 4-month-old heterozygous males. Most of the fully developed cysts were found in older males (7- to 12-month-old and older), where they are big, filled with liquid and clearly visible externally. The cysts are located deep to the pelvic floor, dorso-laterally of the ischiocavernosus and bulbocavernosus muscle (Fig. 1a,b) and, depending on their respective size, extending into a thin thread-like duct. The duct of the cyst could be followed disappearing between these two muscles (Fig. 1c). In a 5-month-old buck a clear connection of the duct to the Cowper's gland was observed in situ (Fig. 1d).

Fig. 1.

Fig. 1

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Localization of the Cowpers gland cysts in situ. (a) Schematic drawing showing the topography of mice male genital organs in situ in a ventral view (top is cranial). The red arrowhead indicates the location of the Cowpers gland in relation to other male accessory sex organs. The green arrow indicates the position of Cowpers gland cysts in Tgfβ2+/− heterozygous male mutant mice. The box demarcates the region shown in the same orientation at higher magnification in c and d. (b) The Cowpers gland cysts found in Tgfβ2+/− heterozygous male mutant mice are located deep to the pelvic floor, dorso-laterally of the ischiocavernosus and bulbocavernosus muscles. (c) The duct of the cyst could be followed disappearing between the ischiocavernosus and bulbocavernosus muscles. (d) A connection of the cysts duct to the Cowpers gland was clearly demonstrated by dissection. a, anus; c, cyst; cd, cystic duct; cg, Cowpers gland (glandula bulbourethralis); mb, musculus bulbocavernosus; mi, musculus ischiocavernosus; p, penis; pg, preputial gland; pl, prostatic lobe; r, rectum; t, testis; ub, urinary bladder, vs, seminal vesicle/vesicula seminalis; scale bar in c: 5 mm (also applies for b and d).

In addition to the glandular hyperplasia of Cowper's gland and the formation of Cowper's cysts, multiple alterations of the male genitalia are observed in heterozygous transgenic animals,particularly a depressed yield of spermatogenesis with malformation of spermatozoa and a strong hyperplasia of the coagulating gland (not shown).

Histological comparison of normal Cowper's gland, heterozygous hyperplastic Cowper's gland and Cowper's gland cyst

Histological analysis revealed marked differences between Cowper's glands of the wild-type (Tgfβ2+/+) and transgenic (Tgfβ2+/–) mice. In the wild-type animal (Fig. 2a), the glands consist of small lobules of glandular cells densely filled with secretion granules, inserted into thick strands of smooth and striated muscle, separated by thinner layers of connective tissue (Fig. 2b,c), whereas the glands of the Tgfβ2+/– heterozygous mutants (Fig. 2d) show all steps of glandular hyperplasia, local atrophy, ductal transformation and cystic dilation. The hyperplastic glandular cells often nearly fill the lumen, appear foamy and their outline is often blurred (Fig. 2e,f). In heterozygous Tgfβ2+/– mutants the nuclei of the acinar cells are not strictly arranged in a basal position, as in the wild-type bulbourethral glands (compare Fig. 2b and c), but usually occupy the centre of the cells (Fig. 2e,f). Furthermore, the nuclei of Tgfβ2+/+ wild-type Cowper's glandular cells are usually round to egg-shaped, whereas in the hyperplastic cells nuclei have a more irregular form and are slightly indented or appear compressed (Fig. 2f).

Fig. 2.

Fig. 2

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Histological comparison of normal Cowper's gland of Tgfβ2+/+ mice (a,b,c) and hyperplastic Cowper's gland of Tgfβ2+/− heterozygous mutant mice (d,e,f) as shown in paraffin (a,d) and semithin sections (b,c,e,f). (a) In 12-month-old Tgfβ2+/+ mice the tubuloalveolar Cowper's gland consists of numerous acini separated by connective tissue septa and is surrounded by a layer of striated muscle. (b) In Tgfβ2+/− heterozygous mutants of comparable age, the muscular capsule surrounding the Cowper's gland has considerably thickened and the glandular cells show a marked hyperplasia. Scale bar in d: 100 μm (also applies for a). The glandular epithelium of Tgfβ2+/− wild-type Cowper's gland forms typical acini and contains numerous large secretory granules (b,c). The hyperplastic glandular epithelium in Tgfβ2+/− heterozygous mutant littermates appears multilayered and contains large foamy or vacuolated cells with irregular nuclear structure and position (e,f). Scale bar in e: 25 μm (also applies for b); scale bar in f: 10 μm (also applies for c).

The glandular cells of Cowper's gland cysts appear foamy, contain shrunken nuclei and resemble the hyperplastic glandular cells typical of the heterozygous Cowper's glands Tgfβ2+/– heterozygous mutants (Fig. 3). The cyst wall proper displays a marked heterogeneity of its epithelial lining (Fig. 3a,b). The collapsed cyst wall is thin, consisting of a meandering, multilayered or wrinkled myofibrous sheath covered by low squamous epithelium (Fig. 3a), which alternates with stretches of multilayered squamous, cuboidal to columnar epithelium (Fig. 3b). At higher magnification, the coexistence of flat squamous and glandular epithelium on either side of the intracystic papillary foldings becomes obvious (Fig. 3b).

Fig. 3.

Fig. 3

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Structure of the Cowper's gland cyst wall of Tgfβ2+/− heterozygous mutants. In semithin sections the cellular lining of the cyst wall displays a marked heterogeneity of the epithelial lining ranging from single layered squamous epithelium to multilayered glandular structures covering papillary folds. Scale bars: 75 μm in a; 25 μm in b.

Electron microscopy of Cowper's gland and cysts in transgenic mice

Cowper's glands of heterozygous Tgfβ2+/– mutants display an abundance of electron-translucent secretory granules, sometimes containing a clear centre or an eccentric clear halo (Fig. 4a), surrounded by densely packed layers of rough endoplasmic reticulum. In slightly hyperplastic glandular cells, the secretory granules display a considerable heterogeneity in size, internal structure and electron density, respectively (Fig. 4b).

Fig. 4.

Fig. 4

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Ultrastructural comparison of hyperplastic Cowper's gland (a,b) with Cowper's gland cyst (c–f) of Tgfβ2+/− heterozygous mutant mice. (a) Survey electron micrograph of hyperplastic glandular cells from Cowper's gland of a Tgfβ2+/− heterozygous animal. Note the dense number and slight heterogeneity of secretory granules. (b) At higher magnification, the structural heterogeneity of the secretory granules in hyperplastic glandular cells becomes more obvious. (c) Strongly hyperplastic cells from the cyst wall with extreme overload of polymorphic secretory material. (d) Stratified epithelium from the cyst wall devoid of any signs of secretion. (e) Dual epithelial lining of a papillary infolding of the cyst wall with secretory and non-secretory cells. (f ) Condensed connective tissue from the cyst wall covered by vacuolated epithelial cells. ct, connective tissue; ep, epithelium; h, halo; l, lumen; n, nucleus; org, cytoplasmic organelles; sg, secretory granule; sm, secretory material; str, stroma; Magnification 4000× (a, c–f); 8500× (b).

Hyperplastic acini from the Cowper's gland cyst consist of extremely densely packed large glandular cells, containing a plethora of heterogeneously structured secretory material, sometimes compressing the basally located pycnotic nucleus (Fig. 4c) and slightly bulging the apical plasma membrane into the lumen. Interspersed between these hyperplastic portions are found areas consisting of a multilayered epithelium, completely devoid of any secretion granules and containing only few cytoplasmic organelles (Fig. 4d). In some areas, thin elongate papillary strands of connective tissue are covered with secretory cells gradually decreasing in height and containing lower amounts of secretory material (Fig. 4e). In atrophic areas, the thin layers of connective tissue and muscle cells are covered with a very low squamous epithelium, mostly devoid of secretory material and containing only very few cytoplasmic organelles. The basement membrane of the cells is massively thickened with the cells appearing to rest on a thick layer of acellular material (Fig. 4f). The contents of the cysts is clear and electron-translucent and consists of the secretion of the ductally transformed glandular cells.

Immunocytochemical localization of TGF-β isoforms and TβR in the Cowper's gland

TGF-β isoforms and TβR-II were detected immunocytochmically in paraffin sections of adult male Cowper's glands. TGF-β2 and TGF-β3 are located predominantly in myoepithelial cells (Fig. 5b,c). Staining was, however, also observed in round structures within the glandular cells strongly resembling secretory granules and/or Golgi vesicles (arrowheads in Fig. 5b,c). The TβR-II was found in the plasma membrane of the acinus cells (small arrowheads in Fig. 5a).

Fig. 5.

Fig. 5

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Immunocytochemical detection of TGF-β isoforms and TβR-II in paraffin sections of adult male Cowper's glands. (a) The TβR-II was found in the plasma membrane of the acinus cells (small arrowheads). (b,c) TGF-β2 and TGF-β3 were located predominantly in myoepithelial cells (small arrows). Staining was, however, also observed in round structures within the glandular cells strongly resembling secretory granules and/or golgi vesicles (arrowheads). Scale bar: 25 μm (also applies to b,c).

Detection of cell death

Apoptotic cells were labelled by TUNEL staining of histological cross-sections of normal and hyperplastic Cowper's glands. Significantly more TUNEL-positive cells were found in normal Cowper's glands of Tgfβ2+/+ mice (Fig. 6a) as compared to Cowper's glands of Tgfβ2+/– heterozygous mutant mice (Fig. 6b). Cell counts of TUNEL-positive cells revealed a reduction of about 80% in the number of apoptotic nuclei in hyperplastic Cowper's gland tissue of Tgfβ2+/– heterozygous mutant mice (Fig. 6c).

Fig. 6.

Fig. 6

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Detection of cell death in normal and hyperplastic Cowper's glands by TUNEL stain. Significantly more TUNEL-positive cells were found in normal Cowper's glands of Tgfβ2+/+ mice (a) as compared to Cowper's glands of Tgfβ2+/− heterozygous mutant mice (b). Cell counts of TUNEL-positive cells revealed a reduction of about 80% in the number of apoptotic nuclei in hyperplastic Cowper's gland tissue of Tgfβ2+/− heterozygous mutant mice (c). Values are means ± SEM. ***P < 0.001; unpaired Student's t-test. Scale bar in b: 25 μm (also applies for a).

Discussion

In this report we present evidence from in situ, light and electron microscopy that the cysts observed in Tgfβ2+/– heterozygous mice males derive from Cowper's gland tissue.

In humans syringoceles, a lesion of the Cowper's gland or uncommon cystic dilatation of the gland ducts are described (van Brie et al. 1990; Richter et al. 1998) Cystic dilations of Cowper's gland ducts (Cowper's syringoceles) are retention cysts of the Cowper's gland, first described by Fenwick (1896) and rediscovered by Maizel et al. (1983), who established a useful classification of dilated Cowper's gland ducts. The cysts we found in Tgfβ2+/– heterozygous mice resemble retention cysts probably resulting from an outflow obstruction in the bulbourethral ducts. It might be speculated that one of the Cowper's gland duct branches obturates and if this sealed side branch still contains secretory active cells, it might expand and form a cyst.

The fact that the Cowper's gland of Tgfβ2+/– mice mutants exhibit cystic dilations of the gland ducts suggests a disturbance of epithelial–stromal interactions. Stromal–epithelial interactions play a critical role in prostatic development and TGF-β has been suggested to be a potential mediator of these interactions (Blanchère et al. 2001). Gene ablation studies revealed that TGF-β seems to be involved in epithelial–mesenchymal interactions in general (Heine et al. 1987). These interactions are significantly impaired if the endogenous level of TGF-β is reduced. As Western blot analysis confirmed that in Tgfβ2+/– heterozygous mutants mice, exhibiting Cowper's gland cysts, TGF-β2 levels are reduced by 50% (Sanford et al. 1997; Dünker et al. 2002), TGF-β is a good candidate for playing a key function in regulating the duct branching during morphogenesis of bulbourethral gland.

We are the first to investigate the expression and localization of TGF-β isoforms andTβRs in the bulbourethral gland of mice. TGF-β2 and TGF-β3 as well as the TβR-II were expressed in the Cowper's gland of adult mice. Immunolabelling for TGF-β isoforms and TβR was found in both the epithelium, or more precisely in smooth muscle cells of the Cowper's gland and in the ducts. It has been shown that, in the rat prostate, smooth muscle cells surrounding the ducts of the proximal region secrete TGF-β1. The paracrine effect of TGF-β1 secreted by these smooth muscle cells was implicated in the inhibition of epithelial cell proliferation and promotion of epithelial cell apoptosis (Kyprianou & Isaac, 1989; Martikainen & Isaac, 1990; Nemeth et al. 1997; Itoh et al. 1998; Lee et al. 1999; Wikström et al. 2001). These findings are consonant with the observation that the expression of TβR-II is highest in the epithelium of the adult rat prostate (Kim et al. 1996). Expression of TGF-βs has also been demonstrated in mesenchyme surrounding ducts in fetal and neonatal mouse prostates, suggesting a role for TGF-βs in ductal branching morphogenesis during prostatic development (Timme et al. 1995). Alvarez & Bass (1999) investigated the consequences of elevated exposure to TGF-β on pancreatic duct epithelium in vitro and found that proliferation was inhibited and apoptosis induced. Kundu et al. (2000) showed the absence of proximal duct apoptosis in the ventral prostate of transgenic mice carrying a dominant negative TβR-II receptor. Tanji et al. (2000) investigated the effect of TGF-β1 on the development of bulbourethral glands of neonatal mice in vitro and showed that addition of TGF-β1 to the 5-alpha-dihydrotestosterone (DHT)-containing culture medium inhibited the increase in overall size of the Cowper's gland, androgen-induced epithelial and mesenchymal growth, epithelial morphogenesis and ductal branching in a dose-dependent manner.

The results of the present study revealing a highly significant, 80% decrease in the number of TUNEL-positive, apoptotic cells in hyperplastic Cowper's glands of Tgfβ2+/– heterozygous mutants mice correspond with these findings and strongly suggest a pro-apoptotic role of TGF-β not only in the prostate but also in Cowper's gland development. Previous studies by our group confirmed the role of TGF-β2 and TGF-β3 in mediating proliferation and apoptosis in different tissues (Combs et al. 2000; Krieglstein et al. 2000; Dünker et al. 2001, 2002). We demonstrated that programmed cell death (PCD) of chick ciliary, dorsal root and spinal motor neurones is largely prevented by application of a neutralizing antibody that recognizes all three TGF-β isoforms (Krieglstein et al. 2000). The pro-apoptotic role of endogenous TGF-β was confirmed most recently by showing TGF-β's capacity to induce cell death in the developing chick retina (Dünker et al. 2001) as well as in the murine small intestine (Dünker et al. 2002).

Conclusions

In the present study we present evidence that a reduction in endogenous TGF-β2 level leads to a significant reduction in cell death in bulbourethral glands which in turn results in Cowper's gland hyperplasia and generation of cysts in Tgfβ2+/–mice mutants.

Acknowledgments

We are grateful to T. Doetschman for generously providing Tgfβ2+/− breeding pairs. We also thank Mr K. Schmitt, Ms S. Brundaler, Ms I. Dammshäuser and Ms G. Kühnreich for excellent technical assistance. This work was supported by grants from the Deutsche Forschungsgemeinschaft.

References

  1. Alvarez C, Bass BL. Role of transforming growth factor-beta in growth and injury response of pancreatic duct epithelium in vitro. J. Gastrointest. Surg. 1999;3:178–184. doi: 10.1016/s1091-255x(99)80030-4. [DOI] [PubMed] [Google Scholar]
  2. Blanchère M, Mestayer C, Saunier E, Broshuis M, Mowszowicz I. Transforming growth factor β in the human prostate: its role in stromal–epithelial interactions in non-cancerous cell culture. Prostate. 2001;46:311–318. doi: 10.1002/1097-0045(20010301)46:4<311::aid-pros1038>3.0.co;2-2. [DOI] [PubMed] [Google Scholar]
  3. Böck P. Der Semidünnschnitt. München: Bergmann; 1984. pp. 54–64. [Google Scholar]
  4. van Brien P, Mattelaer J, Billiet I. Syringocele, a rare lesion of Cowper's gland. Acta Urol. Belg. 1990;58:145–151. [PubMed] [Google Scholar]
  5. Combs SE, Krieglstein K, Unsicker K. Reduction of endogenous TGF-beta increases proliferation of developing adrenal chromaffin cells in vivo. J. Neurosci. Res. 2000;59:379–383. doi: 10.1002/(SICI)1097-4547(20000201)59:3<379::AID-JNR12>3.0.CO;2-5. [DOI] [PubMed] [Google Scholar]
  6. Cook PS, Young PF, Cunha GR. Androgen dependence of grwoth and epithelial morphogenesis in neonatal mouse bulbourethral glands. Endocrinology. 1987;121:2153–2160. doi: 10.1210/endo-121-6-2153. [DOI] [PubMed] [Google Scholar]
  7. Dünker N, Krieglstein K. Targeted mutations of transforming growth factor-beta genes reveal important roles in mouse development and adult homeostasis. Eur. J. Biochem. 2000;267:6982–6988. doi: 10.1046/j.1432-1327.2000.01825.x. [DOI] [PubMed] [Google Scholar]
  8. Dünker N, Schuster N, Krieglstein K. TGF-β modulates programmed cell death in the retina of the developing chick embryo. Development. 2001;128:1933–1942. doi: 10.1242/dev.128.11.1933. [DOI] [PubMed] [Google Scholar]
  9. Dünker N, Schmitt K, Schuster N, Krieglstein K. The role of Transforming growth factor beta 2 and 3 in mediating apoptosis in the murine intestinal mucosa. Gastroenterology. 2002;122:1364–1375. doi: 10.1053/gast.2002.32991. [DOI] [PubMed] [Google Scholar]
  10. Fenwick EH. Retention cysts of Cowper's glands as a cause of chronic gleet, spasmodic stricture, organic stricture extravasation of urine. Br. Med. J. 1896;1:4. doi: 10.1136/bmj.1.1827.4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Flickinger CJ. Fine structural aspects of cytodifferentiation. In: Brandes D, editor. Male Acessory Sex Organs. New York: Academic Press; 1974. pp. 115–130. [Google Scholar]
  12. Franks LM. Normal and pathological anatomy and histology of the genital tract of rats and mice. In: Cotchin E, Roe F, editors. Pathology of Laboratory Rats and Mice. Oxford: Blackwell Scientific Publications; 1967. pp. 469–479. [Google Scholar]
  13. Heine U, Munoz EF, Flanders KC, Ellingsworth LR, Lam HY, Thompson NL, Roberts AB, Sporn MB. Role of transforming growth facto-beta in the development of the mouse embryo. J. Cell Biol. 1987;105:2861–2876. doi: 10.1083/jcb.105.6.2861. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Itoh N, Patel U, Cupp AS, Skinner MK. Development and hormonal regulation of transforming growth factor-beta1 (TGFbeta1)-2 and -3 gene expression in isolated prostatic epithelial and stromal cells: epidermal growth factor and TGFbeta interactions. Endocrinology. 1998;139:1378–1388. doi: 10.1210/endo.139.3.5787. [DOI] [PubMed] [Google Scholar]
  15. Kim IY, Ahn HJ, Zelner DJ, Park L, Sensibar JA, Lee C. Expression and localization of transforming growth factor-beta receptors type I and type II in the rat ventral prostate during regression. Mol. Endocrinol. 1996;10:107–115. doi: 10.1210/mend.10.1.8838150. [DOI] [PubMed] [Google Scholar]
  16. Krieglstein K, Richter S, Farkas L, Schuster N, Dünker N, Oppenheim RW, et al. Reduction of endogenous TGF-β prevents ontogenetic neuron death. Nat. Neurosci. 2000;3:1085–1090. doi: 10.1038/80598. [DOI] [PubMed] [Google Scholar]
  17. Kundu SD, Kim IY, Yang T, Doglio L, Lang S, Zhang X, et al. Absence of proximal duct apoptosis in the ventral prostate of transgenic mice carrying the C3 (I) -TGF-β type II dominant negative receptor. Prostate. 2000;43:118–124. doi: 10.1002/(sici)1097-0045(20000501)43:2<118::aid-pros6>3.0.co;2-v. [DOI] [PubMed] [Google Scholar]
  18. Kyprianou N, Isaac JT. Expression of transforming growth factors-beta in the rat ventral prostate during castration-induced programmed cell death. Mol. Endocrinol. 1989;3:1515–1522. doi: 10.1210/mend-3-10-1515. [DOI] [PubMed] [Google Scholar]
  19. Lee C, Sintich SM, Mathews EP, Shah AH, Kundu SD, Perry KT. Transforming growth factor-beta in benign and malignant prostate. Prostate. 1999;39:285–290. doi: 10.1002/(sici)1097-0045(19990601)39:4<285::aid-pros9>3.0.co;2-7. [DOI] [PubMed] [Google Scholar]
  20. Maizel M, Stephens FS, King LR, Firlit CF. Cowper's syringocele: a classification of dilation of Cowper's gland duct based upon clinical characteristics of 8 boys. J. Urol. 1983;129:1–114. doi: 10.1016/s0022-5347(17)51946-1. [DOI] [PubMed] [Google Scholar]
  21. Martikainen P, Isaacs JT. An organ culture system for the study of programmed cell death in the rat ventral prostate. Endocrinology. 1990;127:1268–1277. doi: 10.1210/endo-127-3-1268. [DOI] [PubMed] [Google Scholar]
  22. Massague J, Chen YG. Controlling TGF-beta signaling. Genes Dev. 2000;14:627–644. [PubMed] [Google Scholar]
  23. Nemeth JA, Sensibar JA, White RR, Zelner DJ, Kim IY, Lee C. Prostatic ductal system in rats: tissue-specific expression and regional variation in stromal distribution of transforming growth factor-beta1. Prostate. 1997;33:64–71. doi: 10.1002/(sici)1097-0045(19970915)33:1<64::aid-pros11>3.0.co;2-j. [DOI] [PubMed] [Google Scholar]
  24. Parr MB, Ren HP, Kepple L, Parr EL, Russell LD. Ultrastructure and morphometry of the urethral glands in normal, castrated, and testosterone-treated castrated male mice. Anat. Rec. 1993;236:449–458. doi: 10.1002/ar.1092360305. [DOI] [PubMed] [Google Scholar]
  25. Rauther M. Ueber den Genitalapparat einiger Nager und Insektivoren, insbesondere die akzesso rischen Genitaldrüsen derselben. Jenaische Ztschr. Naturwiss. 1904;38:377–472. [Google Scholar]
  26. Richter S, Shalev M, Nissenkorn I. Late appearance of Cowper's syringocele. J. Urol. 1998;160:128–129. [PubMed] [Google Scholar]
  27. Riva A, Usai E, Cossu M, Scarpa R, Testa-Riva F. The human bulbo-urethral glands. A transmission electron microscopy and scanning electron microscopy study. J. Androl. 1988;9:133–141. doi: 10.1002/j.1939-4640.1988.tb01025.x. [DOI] [PubMed] [Google Scholar]
  28. Riva A, Usai E, Cossu M, Lantini MS, Scarpa R, Testa-Riva F. Ultrastructure of human bulbourethral glands and of their main excretory ducts. Arch. Androl. 1990;24:177–184. doi: 10.3109/01485019008986877. [DOI] [PubMed] [Google Scholar]
  29. Roberts AB, Sporn MB. The transforming growth factors-βs. In: Sporn MB, Roberts AB, editors. Handbook of Experimental Pharmacology. Heidelberg: Springer Verlag; 1990. pp. 419–472. [Google Scholar]
  30. Sanford LP, Ormsby I, Gittenberger-de Groot A, Sariola H, Friedman R, Boivin GP, et al. TGFβ2 knockout mice have multiple developmental defects that are non-overlapping with other TGFβ knockout phenotypes. Development. 1997;127:2659–2670. doi: 10.1242/dev.124.13.2659. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Sirigu P, Turno F, Perra MT. Histochemical study of the human bulborethral (Cowper’s) glands. Andrologia. 1993;25:293–299. doi: 10.1111/j.1439-0272.1993.tb02728.x. [DOI] [PubMed] [Google Scholar]
  32. Tanji N, Rahman SA, Terada N, Yokoama M, Cunha GR. Effects of transforming growth factor β-1 and all-trans-retinoic acid on androgen-induced development of neonatal mouse bulbourethral glands in vitro. Int. J. Androl. 2000;23:58–64. doi: 10.1046/j.1365-2605.2000.00209.x. [DOI] [PubMed] [Google Scholar]
  33. Timme TL, Truong LD, Slawin KM, Kadmon D, Park SH, Thompson TC. Mesenchymal–epithelial interactions and transforming growth factor-beta 1 expression during normal and abnormal prostatic growth. Microsc. Res. Techn. 1995;30:333–341. doi: 10.1002/jemt.1070300408. [DOI] [PubMed] [Google Scholar]
  34. Wikström P, Damber JE, Bergh A. Role of transforming growth factor-β1 in prostate cancer. Microsc. Res. Techn. 2001;52:411–419. doi: 10.1002/1097-0029(20010215)52:4<411::AID-JEMT1026>3.0.CO;2-8. [DOI] [PubMed] [Google Scholar]

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