The fetal rat gubernaculum contains higher levels of androgen receptor than does the postnatal gubernaculum

Morphologic alterations of the genital mesentery implicated in testis non-descent in rats prenatally exposed to flutamide

BACKGROUND

There is an endless debate on whether androgens mediate testis descent through developmental changes in the gubernacular or the cranial suspensory ligament.

OBJECTIVE

To investigate the relation of any possible morphologic changes in the genital mesentery, that is, the system of genital peritoneal folds including the gubernacular and cranial suspensory ligaments, with the event of testis non-descent in rats prenatally exposed to the antiandrogen flutamide.

MATERIALS AND METHODS

Time-pregnant Sprague Dawley rats received flutamide (100 mg/kg/d) or vehicle subcutaneously on gestational days 16-17. Flutamide-treated male offspring (n = 67), and vehicle-treated male (n = 34) and female (n = 28) offspring were surgically explored under microscope on postnatal day 50. Testicular position was examined bilaterally. Dimensions of genital mesentery parts were also assessed bilaterally. Association of flutamide-induced morphologic changes with descended (n = 61) and undescended (n = 50; 33 cryptorchid and 17 ectopic) testes was investigated with logistic regression analysis.

RESULTS

The male genital mesentery comprised a cranial and a caudal fold converging on the vas deferens. Flutamide resulted in enlarged cranial and reduced caudal folds. Of all flutamide-induced alterations, the increased length of the posterior fixation of the cranial fold and the decreased length of the gubernacular ligament of the caudal fold were found to independently increase the odds of testis non-descent. Testicular ectopy, unlike cryptorchidism, was associated with a short gubernacular ligament only. The female genital mesentery consisted of a cranial fold only.

CONCLUSION

Our findings showed a combined contribution of both cranial and caudal folds of the genital mesentery to testis non-descent, through an abnormally long mesentery root and an abnormally short gubernacular ligament, respectively. Inhibition of male-specific development of the genital mesentery with flutamide did not result in a feminized architecture.

Regional Variation in Androgen Receptor Expression and Biomechanical Properties May Contribute to Cryptorchidism Susceptibility in the LE/orl Rat

Background: The process of testicular descent requires androgen and insulin-like 3, hormones secreted by fetal Leydig cells. Knowledge concerning distinct and common functions of these hormones in regulating development of the fetal gubernaculum remains limited and/or conflicting. The current studies were designed to better define characteristics of androgen receptor (AR) expression, function and regulation, as well as the biomechanical properties of normal and cryptorchid gubernaculum during fetal development. Methods: We studied fetal gubernacula from Long Evans outbred (LE/wt) rats and an inbred (LE/orl) strain with an inherited form of cryptorchidism associated with an AR signaling defect. Gubernacular cells or whole organs obtained from LE/wt and LE/orl fetal gubernacula underwent AR immunostaining and quantitative image analysis. The effects of dihydrotestosterone (DHT) on AR expression, muscle fiber morphology, hyaluronan (HA) levels and glycosaminoglycan (GAG) content were measured in LE/wt gubernacula. Finally, the spatial mechanics of freshly harvested LE/wt and LE/orl fetal gubernacula were compared using micropipette aspiration. Results: AR is expressed in the nucleus of mesenchymal core, tip and cord cells of the embryonic (E) day 17 and 21 fetal gubernaculum, and is enhanced by DHT in primary cultures of gubernacular mesenchymal cells. Enhanced AR expression at the tip was observed in LE/wt but not LE/orl gubernacula. In in vitro studies of whole mount fetal gubernaculum, DHT did not alter muscle fiber morphology, HA content or GAG production. Progressive swelling with reduced cellular density of the LE/wt gubernaculum at E19-21 was associated with increased central stiffness in LE/wt but not in LE/orl fetuses. Conclusions: These data confirm nuclear AR expression in gubernacular mesenchyme with distal enhancement at the tip/cord region in LE/wt but not LE/orl rat fetuses. DHT enhanced cellular AR expression but had no major effects on muscle morphology or matrix composition in the rat fetal gubernaculum in vitro. Regional increased stiffness and decreased cell density between E19 and E21 were observed in LE/wt but not LE/orl fetal gubernacula. Developmental differences in cell-specific AR expression in LE/orl fetal gubernacula may contribute to the dysmorphism and aberrant function that underlies cryptorchidism susceptibility in this strain.

Perspective: A Neuro-Hormonal Systems Approach to Understanding the Complexity of Cryptorchidism Susceptibility

Nonsyndromic cryptorchidism is a common multifactorial, condition with long-term risks of subfertility and testicular cancer. Revealing the causes of cryptorchidism will likely improve prediction and prevention of adverse outcomes. Herein we provide our current perspective of cryptorchidism complexity in a synthesis of cumulative clinical and translational data generated by ourselves and others. From our recent comparison of genome-wide association study (GWAS) data of cryptorchidism with or without testicular germ cell tumor, we identified RBFOX family genes as candidate susceptibility loci. Notably, RBFOX proteins regulate production of calcitonin gene-related peptide (CGRP), a sensory neuropeptide linked to testicular descent in animal models. We also re-analyzed existing fetal testis transcriptome data from a rat model of inherited cryptorchidism (the LE/orl strain) for enrichment of Leydig cell progenitor genes. The majority are coordinately downregulated, consistent with known reduced testicular testosterone levels in the LE/orl fetus, and similarly suppressed in the gubernaculum. Using qRT-PCR, we found dysregulation of dorsal root ganglia (DRG) sensory transcripts ipsilateral to undescended testes. These data suggest that LE/orl cryptorchidism is associated with altered signaling in possibly related cell types in the testis and gubernaculum as well as DRG. Complementary rat and human studies thus lead us to propose a multi-level, integrated neuro-hormonal model of testicular descent. Variants in genes encoding RBFOX family proteins and/or their transcriptional targets combined with environmental exposures may disrupt this complex pathway to enhance cryptorchidism susceptibility. We believe that a systems approach is necessary to provide further insight into the causes and consequences of cryptorchidism.

EFFECT OF EPIDERMAL GROWTH FACTOR ON SPERMATOGENESIS IN THE CRYPTORCHID RAT

PURPOSE

Epidermal growth factor (EGF) is secreted mainly from the submandibular glands. Submandibular gland ablation causes a marked decrease in male fertility, which suggests that EGF influences spermatogenesis. We investigated the effect of EGF in combination with orchiopexy on cryptorchid rat testes in which tubular deterioration had become partially irreversible.

MATERIALS AND METHODS

Unilaterally cryptorchid rats were obtained by daily administration of 7.5 mg flutamide (Nihonkayaku, Tokyo, Japan), an androgen receptor antagonist, to pregnant rats. At age 10 weeks the unilaterally cryptorchid rats underwent orchiopexy with or without EGF administered into the cryptorchid testis. EGF solution (10 microg/ml) was delivered into the seminiferous tubules by retrograde perfusion through the rete testis. At 14 days testicular recovery was assessed based on the maturity of spermatogenesis using a modified Johnsen score and from the number of apoptotic germ cells per seminiferous tubule.

RESULTS

Mean Johnsen score +/- SEM was significantly higher in the orchiopexy with EGF than in the orchiopexy without EGF group (7.85 +/- 0.12 vs 7.12 +/- 0.13, p <0.001). The number of apoptotic germ cells tended to be smaller in the orchiopexy with EGF group than in the orchiopexy without EGF group (0.16 +/- 0.05 vs 0.28 +/- 0.08).

CONCLUSIONS

Although orchiopexy for cryptorchidism partly improved spermatogenesis, recovery was limited. EGF administered in combination with orchiopexy was more effective for spermatogenesis than orchiopexy alone. This may be applicable in patients with cryptorchidism.

Gubernacular fibroblasts express the androgen receptor during testis descent in cryptorchid rats treated with human chorionic gonadotrophin

Cryptorchidism was provoked in 3 day old rats treated with 17-beta-estradiol over 30 days to identify the cells that express the androgen receptor (AR) during experimental testis descent in the gubernaculum. In one group of animals, testis descent was induced with human chorionic gonadotrophin (hCG) applied daily for 5 or 10 days. A correlative study using a testosterone radioimmunoassay with electron microscopy and immunocytochemical detection of AR was performed in gubernacula of hCG treated and untreated control animals. The gubernaculum of rats undergoing testes descent showed a dramatic increase in the number of AR-positive cells. These were located in the connective tissue among smooth muscle cells in the gubernacular cord and between striated muscle fibers in the bulb. In both regions, the AR-positive cells were identified as fibroblasts. Several clusters of amorphous material appeared in the extracellular matrix of the connective tissue in hCG treated rats. Our results suggest that testosterone induces the expression of AR in gubernacular fibroblasts which seem to degrade the extracellular matrix during gubernacular involution.

Molecular and genetic regulation of testis descent and external genitalia development

Testicular descent as a prerequisite for the production of mature spermatozoa and normal external genitalia morphogenesis, and therefore facilitating copulation and internal fertilization, are essential developmental steps in reproduction of vertebrate species. Cryptorchidism, the failure of testis descent, and feminization of external genitalia in the male, usually in the form of hypospadias, in which the opening of the urethra occurs along the ventral aspect of the penis, are the most frequent pediatric complications. Thus, elucidating the molecular mechanisms involved in the regulation of testis descent and the formation of external genitalia merits a special focus. Natural and transgenic rodent models have demonstrated both morphogenic processes to be under the control of a plethora of genetic factors with complex time-, space-, and dose-restricted expression pattern. The review elucidates the molecular mechanisms involved in the regulation of testis descent and the formation of external genitalia and, wherever possible, assesses the differences between these rodent animal models and other mammalian species, including human.

Hormones in male sexual development

Classical embryology has provided a clear view of the timing and hormonal cues that govern sexual differentiation. Molecular biology has added important details to this picture. The cloning of SRY, MIS, and INSL3 provide insight into the molecular signals that provide important cues at the cellular level. Continued understanding of these pathways may provide the necessary information to one day reverse defects of sexual differentiation.

Hormonal control of gubernaculum development during testis descent: gubernaculum outgrowth in vitro requires both insulin-like factor and androgen

The gubernaculum connects the gonad to the inguinoscrotal region and is involved in testis descent. It rapidly develops in the male fetus, whereas development in the female fetus is lacking. Possible factors involved in gubernaculum development are androgens, anti-Müllerian hormone (AMH), and insulin-like factor (Insl3). Sexual dimorphism in gubernaculum development correlated with the mitotic activity of cells in the gubernacular bulbs from male and female fetuses. Androgen receptor expression was restricted to the mesenchymal core of the gubernacular bulb, whereas skeletal muscle was detected in its outer layer. In an organ culture system devised to further study gubernaculum development in vitro, morphology of gubernacular explants grown in the presence of testes was comparable with that of gubernacula developed in vivo. Testicular tissue or medium containing R1881, a synthetic androgen, had a growth stimulatory effect on gubernacular explants compared with ovarian tissue or basal medium only. Moreover, Amh-/-, Amh+/-, and Insl3+/- testes stimulated the growth of gubernacular explants to the same extent as control testes. Insl3-/- testes, however, did not produce such an activity. This study reveals an essential role for both androgen and Insl3 in the gubernaculum outgrowth during transabdominal testis descent.

Ovary in hernia sac: prolapsed or a descended gonad?

BACKGROUND/PURPOSE

The ligament that lies in the inguinal hernia sac of girls is known to be the round ligament and is described as homologous to the male gubernaculum. An ovary in a hernia sac might be assumed to mimic descent of the testis. The aim of this study is to determine whether this ligament has a role in final ovarian position.

METHODS

Samples of peritoneal tissues containing the ligament were obtained from 15 female infants and children who underwent inguinal hernia repair. Tissue specimens were evaluated through histopathologic and immunohistological analyses.

RESULTS

The ligament consists of striated and smooth muscle fibers, abundant nerves, and vessels. Estrogen receptors (ER) and progesterone receptors (PR) were identified in submesothelial stromal and smooth muscle cells. No androgen receptors (AR) were found.

CONCLUSIONS

Although its termination in the processus vaginalis is not found to be consistent with the classical description of the round ligament, localization of ERs and PRs prove that the ligament is a target organ influenced by hormones. Because the round ligament is supposed to be the female gubernaculum that has an altered anatomy and localization because of absence of androgen responsiveness, its modified presentation in a processus vaginalis raises the suspicion that the ovary in a hernia sac may not simply be prolapsed, but is a descended gonad.

Androgen receptor gene alterations are not associated with isolated cryptorchidism

PURPOSE

Multiple theories of testicular descent exist but there is no consensus. Cryptorchidism is a component of the androgen insensitivity syndrome, suggesting that testicular descent may be at least partially under the control of androgenic stimulation. To determine whether isolated cryptorchidism may be caused by androgen insensitivity, we screened a population of boys with isolated cryptorchidism for the presence of androgen receptor gene alterations.

MATERIALS AND METHODS

Deoxyribonucleic acid (DNA) was isolated from tissue collected from 21 patients with isolated cryptorchidism during orchiopexy. Patient selection was biased to maximize the likelihood of detection of a genetic etiology of cryptorchidism. The DNA was screened for androgen receptor gene alterations in exons 2 to 8 using single strand conformational polymorphism analysis.

RESULTS

No abnormalities in the androgen receptor gene were detected by single strand conformational polymorphism analysis in any patient.

CONCLUSIONS

Mutations of the androgen receptor gene in the hormone and DNA binding domains of the protein appear to be an unlikely cause of isolated cryptorchidism.

Androgen receptor gene alterations are not associated with isolated cryptorchidism

PURPOSE

Multiple theories of testicular descent exist but there is no consensus. Cryptorchidism is a component of the androgen insensitivity syndrome, suggesting that testicular descent may be at least partially under the control of androgenic stimulation. To determine whether isolated cryptorchidism may be caused by androgen insensitivity, we screened a population of boys with isolated cryptorchidism for the presence of androgen receptor gene alterations.

MATERIALS AND METHODS

Deoxyribonucleic acid (DNA) was isolated from tissue collected from 21 patients with isolated cryptorchidism during orchiopexy. Patient selection was biased to maximize the likelihood of detection of a genetic etiology of cryptorchidism. The DNA was screened for androgen receptor gene alterations in exons 2 to 8 using single strand conformational polymorphism analysis.

RESULTS

No abnormalities in the androgen receptor gene were detected by single strand conformational polymorphism analysis in any patient.

CONCLUSIONS

Mutations of the androgen receptor gene in the hormone and DNA binding domains of the protein appear to be an unlikely cause of isolated cryptorchidism.

Expression and degradation of rat androgen receptor following castration, testosterone replacement and antiandrogens administration: analysis by Western blot and immunohistochemistry

To elucidate the autoregulation of androgen receptor (AR) by androgen and antiandrogen, Western blot analysis and immunohistochemical study were performed. Castration reduced the immunodetected AR content, and nuclear staining was lost without cytoplasmic staining. Testosterone (T) supplement restored AR content. Quick response of AR content restoring following single administration of T was observed 48 hours after castration. The recovery of AR content detected by Western blot under each condition was accompanied by recovery of the reduced unclear staining intensities in the epithelia. Neither steroidal nor non-steroidal antiandrogens, chlormadinone acetate and flutamide, altered the AR content in normal rat ventral prostate 5, 12, 24 or 48 hours after single administration. Furthermore, neither of the drugs at various doses altered AR levels 12 hours after single administration. In summary, the rat AR is upregulated by androgen. Single administration of antiandrogens have no effect on immunodetected AR content.

Flutamide-induced cryptorchidism in the rat is associated with altered gubernacular morphology

OBJECTIVES

One of the major controversies regarding descent of the testes is whether androgenic regulation of the gubernaculum testes exists. To determine if antiandrogens can alter the development of the gubernaculum within the fetus, the following experiment was performed.

METHODS

Timed pregnant Sprague-Dawley rats were treated with either flutamide, dihydrotestosterone (DHT), or vehicle alone (controls) from gestational day (GD) 15 to 17. Fetal specimens were removed via cesarean section on GD 18 and 20. Serial coronal sections were obtained, and digital microscopy with computer-assisted reconstruction was used to ascertain the morphology of the three components of the gubernaculum, that is, the gubernacular cord and the mesenchymal and muscular components of the gubernacular bulb.

RESULTS

Flutamide significantly prevented and DHT significantly enhanced gubernacular cord regression compared with controls (P < 0.01). Flutamide also resulted in a significant inhibition of the gubernacular bulb outgrowth, with diminution of both the mesenchymal and muscular components of the gubernacular bulb.

CONCLUSIONS

These data suggest that androgens play an active role in gubernacular cord regression and gubernacular outgrowth within the fetal rodent.

Developmental pattern and regulation by androgens of androgen receptor expression in the urogenital tract of the rat

Distribution and regulation of androgen receptor expression during fetal and neonatal virilization of the rat fetus was assessed by immunohistochemistry. In mesonephric duct derivatives the androgen receptor expression became evident first in the efferent ductules and epididymis (on fetal day 14), subsequently in the vas deferens and finally in the seminal vesicle. Mesenchymal cells of the urogenital tubercle were positive for androgen receptors from fetal day 14 onwards. In the mesenchymal cells of the prostate anlagen, androgen receptor positive cells were found first on fetal day 16. Administration of 5alpha-dihydrotestosterone to pregnant rats from day 11 to day 20 of gestation caused a stabilization of the wolffian duct in female fetuses. The androgen receptor expression pattern became similar as found in mail fetuses, and showed an increase in density and in frequency of androgen receptor positive cells. Administration of the androgen antagonist flutamide during the same interval caused a reduction in density and frequency of androgen receptor positive cells in male fetuses. These findings indicate that androgens enhance the expression of androgen receptors in the developing rat genital tract by induction of androgen receptor positive cells, and by increasing the frequency. The developmental pattern of androgen receptor expression in the rat mesonephric duct system reflects the androgen-responsiveness of the ducts, and is consistent with induction of the androgen receptor along the ducts by testosterone reaching these structures in an exocrine fashion.