Age is associated with reduced urethral pressure and afferent activity in rat.

Age-related changes in the lower urinary tract (LUT) can affect the coordination of reflexes and increase the incidence of bladder disorders in elderly. This study examines the age-related loss of urethral signaling capability by measuring the afferent activity directly. We find that less urethral pressure develops in response to fluid flow in old rats compared to young rats and that pressure and flow evoke less urethral afferent activation. These findings are consistent with our previous study demonstrating that the urethra-to-bladder reflex, which is required for efficient voiding, becomes weaker with age. We measured the pudendal afferent response in young (4-7 months) and old (18-24 months) rats to fluid flow in the urethra across a range of flow rates. We used paraffin embedding and hematoxylin and eosin staining to quantify age-related changes in the sensory branch of the pudendal nerve. Urethral afferent signaling in response to the same urethral flow rates was weaker in older animals. That is, the sensitivity of urethra afferents to flow decreased with age, and higher flow rates were required in older animals to recruit urethra afferents. There was also a reduction in the myelin thickness of pudendal afferents in old rats, which is a possible contributing factor to the sensory activity. Furthermore, the same flow rates evoked less pressure in the urethras of old animals, indicating there is an age-related change of the urethral tissue that reduces the pressure stimulus to which these afferents respond. These results help characterize the underlying changes in LUT system with age.

The role of androgens in clitorophallus development and possible applications to transgender patients.

BACKGROUND: The clitorophallus, or glans, is a critical structure in sexual development and plays an important role in how gender is conceptualized across the life span. This can be seen in both the evaluation and treatment of intersex individuals and the use of gender-affirming masculinizing therapies to help those born with a clitoris (small clitorophallus with separate urethra) enlarge or alter the function of that structure. OBJECTIVES: To review the role of testosterone in clitorophallus development from embryo to adulthood, including how exogenous testosterone is used to stimulate clitorophallus enlargement in masculinizing gender-affirming therapy. MATERIALS AND METHODS: Relevant English-language literature was identified and evaluated for data regarding clitorophallus development in endosex and intersex individuals and the utilization of hormonal and surgical masculinizing therapies on the clitorophallus. Studies included evaluated the spectrum of terms regarding the clitorophallus (genital tubercle, clitoris, micropenis, penis). RESULTS: Endogenous testosterone, and its more active metabolite dihydrotestosterone, plays an important role in the development of the genital tubercle into the clitorophallus, primarily during the prenatal and early postnatal periods and then again during puberty. Androgens contribute to not only growth but also the inclusion of a urethra on the ventral aspect. Exogenous testosterone can be used to enlarge the small clitorophallus (clitoris or micropenis) as part of both intersex and gender-affirming care (in transmasculine patients, up to 2 cm of additional growth). Where testosterone is insufficient to provide the degree of masculinization desired, surgical options including phalloplasty and metoidioplasty are available. DISCUSSION AND CONCLUSION: Endogenous testosterone plays an important role in clitorophallus development, and there are circumstances where exogenous testosterone may be useful for masculinization. Surgical options may also help some patients reach their personal goals. As masculinizing gender-affirming care advances, the options available for clitorophallus modifications will likely continue to expand and improve.

Changes in urethral smooth muscle and external urethral sphincter function with age in rats.

To confirm changes in urethral activity with age, both intravesical pressure and urethral perfusion pressure (UPP) were recorded and external urethral sphincter electromyography (EUS-EMG) was performed. A total of 33 female Sprague Dawley rats aged 3 months (young rats), 12 months (middle-aged rats), and 24 months (aged rats) were used. Bladder activity was evaluated using continuous cystometry. Urethral activity was evaluated by simultaneously recording intravesical pressure and UPP in isovolumetric conditions under urethane anesthesia in each group. Additionally, EUS-EMG activity was monitored under the same conditions. In continuous cystometry, the amplitude of bladder contractions was not different among the three groups; nevertheless, residual urine volume was significantly increased in middle-aged and aged rats, as compared in young rats. With respect to UPP, the change in UPP was significantly smaller in aged rats (60%) and middle-aged rats (64%) than in young rats. Furthermore, the mean amplitude of high-frequency oscillations of the EUS was significantly lower in aged (61%) and middle-aged rats (70%) than in young rats. EUS-EMG revealed EUS bursting activity during voiding with clear active and silent phases in young rats but unclear active and silent phases in aged rats. Masson's trichrome staining of the urethra showed EUS atrophy in aged rats compared to young and middle-aged rats. The results indicate that aging induces two urethral dysfunctions in the urethral smooth muscle and EUS, which may lead to dyscoordination between the urinary bladder and urethra.

A comparison of prostatic development in xenografts of human fetal prostate and human female fetal proximal urethra grown in dihydrotestosterone-treated hosts.

The goal of this paper is to explore the ability of the human female urogenital sinus immediately below the bladder (proximal urethra) to undergo prostatic development in response to dihydrotestosterone (DHT). To establish this idea, xenografts of human fetal female proximal urethra were grown in castrated nude mouse hosts receiving a subcutaneous DHT pellet. To verify the prostatic nature of the resultant glands, DHT-treated human fetal female urethral xenografts were compared with human fetal prostatic xenografts (derived from male specimens) grown in untreated and DHT-treated castrated mouse hosts and human fetal female proximal urethral xenografts grown in untreated castrated hosts. The resultant glands observed in DHT-treated human fetal female proximal urethral xenografts expressed 3 prostate-specific markers, NKX3.1, prostate specific antigen and prostatic acid phosphatase as well as the androgen receptor. Glands induced by DHT exhibited a protein expression profile of additional immunohistochemical markers (seven keratins, RUNX1, ESR2, TP63 and FOXA1) consistent with the unique spatial pattern of these proteins in prostatic ducts. Xenografts of human fetal female proximal urethra grown in DHT-treated hosts also expressed one of the salient features of prostatic development, namely androgen responsiveness. The experimental induction of prostatic differentiation from human fetal female proximal urethra makes possible future in-depth analysis of the molecular pathways directly involved in initiation of human prostatic development and subsequent epithelial differentiation, and more important whether the molecular pathways involved in human prostatic development are similar/identical versus different from that in murine prostatic development.

Data integration, analysis, and interpretation of eight academic CLARITY-BPA studies.

"Consortium Linking Academic and Regulatory Insights on BPA Toxicity" (CLARITY-BPA) was a comprehensive "industry-standard" Good Laboratory Practice (GLP)-compliant 2-year chronic exposure study of bisphenol A (BPA) toxicity that was supplemented by hypothesis-driven independent investigator-initiated studies. The investigator-initiated studies were focused on integrating disease-associated, molecular, and physiological endpoints previously found by academic scientists into an industry standard guideline-compliant toxicity study. Thus, the goal of this collaboration was to provide a more comprehensive dataset upon which to base safety standards and to determine whether industry-standard tests are as sensitive and predictive as molecular and disease-associated endpoints. The goal of this report is to integrate the findings from the investigator-initiated studies into a comprehensive overview of the observed impacts of BPA across the multiple organs and systems analyzed. For each organ system, we provide the rationale for the study, an overview of methodology, and summarize major findings. We then compare the results of the CLARITY-BPA studies across organ systems with the results of previous peer-reviewed studies from independent labs. Finally, we discuss potential influences that contributed to differences between studies. Developmental exposure to BPA can lead to adverse effects in multiple organs systems, including the brain, prostate gland, urinary tract, ovary, mammary gland, and heart. As published previously, many effects were at the lowest dose tested, 2.5µg/kg /day, and many of the responses were non-monotonic. Because the low dose of BPA affected endpoints in the same animals across organs evaluated in different labs, we conclude that these are biologically - and toxicologically - relevant.

Development of the human prepuce and its innervation.

Development of the human prepuce was studied over the course of 9-17 weeks of gestation in 30 specimens. Scanning electron microscopy revealed subtle surface features that were associated with preputial development, namely the appearance of epidermal aggregates that appeared to be associated with formation of the preputial fold. Transverse and sagittal sections revealed that the epidermis of the glans is considerably thicker than that of the penile shaft. We described a novel morphogenetic mechanism of formation of the preputial lamina, namely the splitting of the thick epidermis of the glans into the preputial lamina and the epidermis via the intrusion of mesenchyme containing red blood cells and CD31-positive blood vessels. This process begins at 10-11 weeks of gestation in the proximal aspect of the glans and extends distally. The process is likely to be androgen-dependent and mediated via androgen receptors strategically localized to the morphogenetic process, but signaling through estrogen receptor may play a role. Estrogen receptor alpha (ESR1) has a very limited expression in the developing human glans and prepuce, while estrogen receptor beta (ESR2) is expressed more broadly in the developing preputial lamina, epidermis and urethra. Examination of the ontogeny of innervation of the glans penis and prepuce reveals the presence of the dorsal nerve of the penis as early as 9 weeks of gestation. Nerve fibers enter the glans penis proximally and extend distally over several weeks to eventually reach the distal aspect of the glans and prepuce by 14-16 weeks of gestation.

Hot spots in fetal human penile and clitoral development.

To better understand how the human fetal penis and clitoris grows and remodels, we undertook an investigation to define active areas of cellular proliferation and programmed cell death spatially and temporally during development of human fetal external genitalia from the indifferent stage (8 weeks) to 18 weeks of gestation. Fifty normal human fetal penile and clitoral specimens were examined using macroscopic imaging, scanning electron microscopy and immunohistochemical localization for the cellular proliferation and apoptotic markers, Ki67 and Caspase-3, respectively. A number of hot spots of cellular proliferation characterized by Ki67 localization are present in the penis and clitoris especially early in development, most notably in the corporal body, glans, remodeling glanular urethra, the urethral plate, the roof of the urethral groove and the fully formed penile urethra. The 12-fold increase in penile length over 10 weeks of growth from 8 to 18 weeks of gestation based on Ki67 labelling appears to be driven by cellular proliferation in the corporal body and glans. Throughout all ages in both the developing penis and clitoris Ki67 labeling was consistently elevated in the ventral epidermis and ventral mesenchyme relative to the dorsal counterparts. This finding is consistent with the intense morphogenetic activity/remodeling in the ventral half of the genital tubercle in both sexes involving formation of the urethral/vestibular plates, canalization of the urethral/vestibular plates and fusion of the urethral folds to form the penile urethra. Areas of reduced or absent Ki67 staining include the urethral fold epithelium that fuses to form the penile tubular urethra. In contrast, the urethral fold mesenchyme is positive for Ki67. Apoptosis was rarely noted in the developing penis and clitoris; the only area of minimal Caspase-3 localization was in the epithelium of the ventral epithelial glanular channel remodeling.

Development of the urinary system in guinea pig females (Cavia porcellus) / Desenvolvimento do sistema urinário em fêmeas de porquinhos-da-índia (Cavia porcellus)

Guinea pigs are animal models widely used in research related to developmental biology. The objective of this work was to demonstrate the process of formation and differentiation of urinary organs in females of the species in the prenatal period. Four females were used at 25, 30, 45 and >65 DG (days of gestation). The animals were dissected, and then macroscopic and microscopic descriptions of the urinary organs were performed. At 25 DG metanephros were present in the urogenital crest into the abdominal cavity. Collecting ducts and glomerular precursor cells could be visualized. After this period, metanephros underwent microstructural modifications to form the kidneys at the end of the prenatal period. After 30 DG, the renal parenchyma already had a cortex, where the glomerulus and proximal convoluted tubules were present; and the medulla, where distal convoluted tubules, collecting ducts, and pelvis were present. The pelvis of each kidney was drained by the ureters. The ureters also underwent tissue differentiation to be differentiated (mucosa with transitional epithelium and lamina propria of connective tissue, muscular, and adventitia) at the end of the prenatal period. The urinary vesicle also underwent tissue changes to form the tunics similar to those found in the ureters, with emphasis on the greater volume of the muscular tunica and the lamina propria that constituted the submucosa in this organ. The pelvic urethra was evidenced by a mucosa lined by transitional epithelium, submucosa, muscular and adventitia. Finally, a partial clitoral urethra and a urethral meatus in the prepuce of the clitoris were also evidenced. The urethral channel began to form with the emergence of the urethral plate and the urethral groove at 30 DG and thereafter with the fusion of the urethral folds to form a partially channeled urethra in the clitoris. A urethral meatus was observed in the most distal portion of the clitoral tissue, formed by the fusion of the prepuce. It is concluded that the urinary organs of guinea pig have similar development to that described in domestic animals, except for the partial clitoral urethra and evident urethral meatus.(AU)

Os porquinhos-da-índia são modelos animais amplamente utilizados em pesquisas relacionadas a biologia do desenvolvimento. O objetivo deste trabalho foi demonstrar o processo de formação e diferenciação dos órgãos urinários em fêmeas da espécie no período pré-natal. Foram utilizadas quatro fêmeas aos 25, 30, 45 e >65 DG (dias de gestação). Os animais foram dissecados e então, realizaram-se descrições macroscópicas e microscópicas dos órgãos urinários. Aos 25 DG os metanefros estavam presentes na crista urogenital da cavidade abdominal. Podiam ser visualizados ductos coletores e células precursoras glomerulares. Após este período, os metanefros sofreram modificações microestruturais para formar os rins ao final do período pré-natal. Após os 30 DG, o parênquima renal já apresentava um córtex, onde estavam presentes os glomérulos e túbulos convolutos proximais, e a medula onde estavam presentes túbulos convolutos distais, ductos coletores e a pelve. A pelve de cada rim era drenada pelos ureteres. Os ureteres também sofreram diferenciação tecidual para estarem com suas túnicas diferenciadas (mucosa com epitélio de transição e lâmina própria de tecido conjuntivo; muscular; e, adventícia) ao final do período pré-natal. A vesícula urinária também passou por modificações teciduais para formar as túnicas semelhantes as dos ureteres, com destaque para o maior volume da túnica muscular e a lâmina própria que constituiu a submucosa neste órgão. Uma uretra pélvica foi evidenciada por uma mucosa revestida por epitélio de transição, submucosa, muscular e adventícia. Por último, uma uretra parcialmente clitoriana e um meato uretral no prepúcio do clitóris também foi evidenciado. O canal uretral começou a se formar com o aparecimento da placa uretral e do sulco uretral aos 30 DG e posteriormente com a fusão das pregas uretrais para formar uma uretra parcialmente canalizada no clitóris. Observou-se um meato uretral na porção mais distal do tecido clitoriano, formado pela fusão do prepúcio. Conclui-se que os órgãos urinários do porquinho-da-índia possuem desenvolvimento semelhante ao descrito em animais domésticos, com exceção da uretra parcialmente clitoriana e do meato uretral evidente.(AU)

Single Nucleotide Polymorphisms of HAAO and IRX6 Genes as Risk Factors for Hypospadias.

PURPOSE: We evaluated the association of hypospadias and 17 susceptibility loci previously identified by a European genome-wide association study in a cohort of Japanese patients. We also examined the expression of candidate genes in male mouse embryos to determine the possible underlying mechanisms of this disease. MATERIALS AND METHODS: We enrolled 169 Japanese patients (mean age at surgery 3.7 years) who underwent repair of hypospadias. Genotyping of 17 single nucleotide polymorphisms was performed using a multiplex polymerase chain reaction invader assay. We also performed in situ hybridization to determine whether candidate genes were expressed in the male genital tubercle during embryonic development of the external genitalia in mice. RESULTS: Single nucleotide polymorphism rs3816183 of HAAO was significantly associated with susceptibility to hypospadias in general (p = 0.0019) and to anterior/middle hypospadias (p = 0.0283) and posterior hypospadias (p = 0.0226), while single nucleotide polymorphism rs6499755 of IRX6 showed an association with susceptibility to anterior/middle hypospadias (p = 0.0472). In mouse embryos there was no significant upregulation of Haao expression in the developing male external genitalia. Irx3 and Irx5, which are linked to Irx6 within the IrxB cluster, were expressed in the mesenchyme remote from the urethral plate epithelium during the critical embryonic period for masculinization. Irx6 was expressed in the ectodermal epithelium, demonstrating prominent dorsal ectodermal expression without expression in the ventral ectoderm adjacent to the urethral plate during the same period. CONCLUSIONS: Genetic variations of HAAO and IRX6 influence susceptibility to hypospadias in the Japanese population. Further research is needed to clarify the mechanism by which variations in these genes contribute to the pathogenesis of hypospadias.

Immunohistochemical expression analysis of the human fetal lower urogenital tract.

We have studied the ontogeny of the developing human male and female urogenital tracts from 9 weeks (indifferent stage) to 16 weeks (advanced sex differentiation) of gestation by immunohistochemistry on mid-sagittal sections. Sixteen human fetal pelvises were serial sectioned in the sagittal plane and stained with antibodies to epithelial, muscle, nerve, proliferation and hormone receptor markers. Key findings are: (1) The corpus cavernosum in males and females extends into the glans penis and clitoris, respectively, during the ambisexual stage (9 weeks) and thus appears to be an androgen-independent event. (2) The entire human male (and female) urethra is endodermal in origin based on the presence of FOXA1, KRT 7, uroplakin, and the absence of KRT10 staining. The endoderm of the urethra interfaces with ectodermal epidermis at the site of the urethral meatus. (3) The surface epithelium of the verumontanum is endodermal in origin (FOXA1-positive) with a possible contribution of Pax2-positive epithelial cells implying additional input from the Wolffian duct epithelium. (4) Prostatic ducts arise from the endodermal (FOXA1-positive) urogenital sinus epithelium near the verumontanum. (5) Immunohistochemical staining of mid-sagittal and para-sagittal sections revealed the external anal sphincter, levator ani, bulbospongiosus muscle and the anatomic relationships between these developing skeletal muscles and organs of the male and female reproductive tracts. Future studies of normal human developmental anatomy will lay the foundation for understanding congenital anomalies of the lower urogenital tract.

Development of the human prostate.

This paper provides a detailed compilation of human prostatic development that includes human fetal prostatic gross anatomy, histology, and ontogeny of selected epithelial and mesenchymal differentiation markers and signaling molecules throughout the stages of human prostatic development: (a) pre-bud urogenital sinus (UGS), (b) emergence of solid prostatic epithelial buds from urogenital sinus epithelium (UGE), (c) bud elongation and branching, (d) canalization of the solid epithelial cords, (e) differentiation of luminal and basal epithelial cells, and (f) secretory cytodifferentiation. Additionally, we describe the use of xenografts to assess the actions of androgens and estrogens on human fetal prostatic development. In this regard, we report a new model of de novo DHT-induction of prostatic development from xenografts of human fetal female urethras, which emphasizes the utility of the xenograft approach for investigation of initiation of human prostatic development. These studies raise the possibility of molecular mechanistic studies on human prostatic development through the use of tissue recombinants composed of mutant mouse UGM combined with human fetal prostatic epithelium. Our compilation of human prostatic developmental processes is likely to advance our understanding of the pathogenesis of benign prostatic hyperplasia and prostate cancer as the neoformation of ductal-acinar architecture during normal development is shared during the pathogenesis of benign prostatic hyperplasia and prostate cancer.

miR-21 modification enhances the performance of adipose tissue-derived mesenchymal stem cells for counteracting urethral stricture formation.

The treatment of complicated long segment strictures remains to a challenge, and the substitution urethroplasty treatment is often accompanied by subsequent tissue fibrosis and secondary stricture formation. In situ injection of human adipose tissue-derived stem cells (hADSC) could potential be applied for prevention of urethral fibrosis, but the cells transplantation alone may be insufficient because of the complicated histopathological micro-environmental changes in the injury site. This study investigated whether miR-21 modification can improve the therapeutic efficacy of ADSCs against urethral fibrosis to limit urethral stricture recurrence. MiR-21-modified ADSCs (miR-21) were constructed via lentivirus-mediated transfer of pre-miR-21 and GFP reporter gene. In vitro results suggested that miR-21 modification can increase the angiogenesis genes expression of ADSCs and enhance its anti-oxidative effects against reactive oxygen species (ROS) damage. In vivo results showed that miR-21 modification contributes to increased urodynamic parameters and better formation of the epithelium and the muscle layer as compared to ADSCs transplantation alone groups. The results demonstrated that miR-21 modification in ADSCs could improve urethral wound healing microenvironment, enhance stem cell survival through ROS scavenging and promote the neovascularization via regulating angiogenic genes expression, which eventually increase the ADSCs' therapeutic potential for urethral wound healing.

Human glans and preputial development.

The urethra within the human penile shaft develops via (1) an "Opening Zipper" that facilitates distal canalization of the solid urethral plate to form a wide urethral groove and (2) a "Closing Zipper" that facilitates fusion of the epithelial surfaces of the urethral folds. Herein, we extend our knowledge by describing formation of the human urethra within the glans penis as well as development of the prepuce. Forty-eight normal human fetal penile specimens were examined using scanning electron microscopy and optical projection tomography. Serial histologic sections were evaluated for morphology and immunohistochemical localization for epithelial differentiation markers: Cytokeratins 6, 7, 10, FoxA1, uroplakin and the androgen receptor. As the closing zipper completes fusion of the urethral folds within the penile shaft to form a tubular urethra (~ 13 weeks), canalization of the urethral plate continues in proximal to distal fashion into the glans penis to directly form the urethra within the glans without forming an open urethral groove. Initially, the urethral plate is attached ventrally to the epidermis via an epithelial seam, which is remodeled and eliminated, thus establishing mesenchymal confluence ventral to the glanular urethra. The morphogenetic remodeling involves the strategic expression of cytokeratin 7, FoxA1 and uroplakin in endodermal epithelial cells as the tubular glanular urethra forms. The most ventral epithelial cells of the urethral plate are pinched off from the glanular urethra and are reabsorbed into the epidermis ultimately losing expression of their markers, a process undoubtedly regulated by androgens. The prepuce initially forms on the dorsal aspect of the glans at approximately 12 weeks of gestation. After sequential proximal to distal remodeling of the ventral urethral plate along the ventral aspect of glans, the prepuce of epidermal origin fuses in the ventral midline.

Development of the human penis and clitoris.

The human penis and clitoris develop from the ambisexual genital tubercle. To compare and contrast the development of human penis and clitoris, we used macroscopic photography, optical projection tomography, light sheet microscopy, scanning electron microscopy, histology and immunohistochemistry. The human genital tubercle differentiates into a penis under the influence of androgens forming a tubular urethra that develops by canalization of the urethral plate to form a wide diamond-shaped urethral groove (opening zipper) whose edges (urethral folds) fuse in the midline (closing zipper). In contrast, in females, without the influence of androgens, the vestibular plate (homologue of the urethral plate) undergoes canalization to form a wide vestibular groove whose edges (vestibular folds) remain unfused, ultimately forming the labia minora defining the vaginal vestibule. The neurovascular anatomy is similar in both the developing human penis and clitoris and is the key to successful surgical reconstructions.

Hormone-responsive genes in the SHH and WNT/ß-catenin signaling pathways influence urethral closure and phallus growth.

Environmental endocrine disruptors (EEDs) that affect androgen or estrogen activity may disrupt gene regulation during phallus development to cause hypospadias or a masculinized clitoris. We treated developing male tammar wallabies with estrogen and females with androgen from day 20-40 postpartum (pp) during the androgen imprinting window of sensitivity. Estrogen inhibited phallus elongation but had no effect on urethral closure and did not significantly depress testicular androgen synthesis. Androgen treatment in females did not promote phallus elongation but initiated urethral closure. Phalluses were collected for transcriptome sequencing at day 50 pp when they first become sexually dimorphic to examine changes in two signaling pathways, sonic hedgehog (SHH) and wingless-type MMTV integration site family (WNT)/ß-catenin. SHH mRNA and ß-catenin were predominantly expressed in the urethral epithelium in the tammar phallus, as in eutherian mammals. Estrogen treatment and castration of males induced an upregulation of SHH, while androgen treatment downregulated SHH. These effects appear to be direct since we detected putative estrogen receptor α (ERα) and androgen receptor (AR) binding sites near SHH. WNT5A, like SHH, was downregulated by androgen, while WNT4 was upregulated in female phalluses after androgen treatment. After estrogen treatment, WIF1 and WNT7A were both downregulated in male phalluses. After castration, WNT9A was upregulated. These results suggest that SHH and WNT pathways are regulated by both estrogen and androgen to direct the proliferation and elongation of the phallus during differentiation. Their response to exogenous hormones makes these genes potential targets of EEDs in the etiology of abnormal phallus development including hypospadias.

Development of urogenital system in the Spix cavy: A model for studies on sexual differentiation.

This study documented, for the first time, the morphological patterns of differentiation of male and female genital organs of Spix cavy (Galea spixii) using histological and ultrastructural analyses, with immuno-localization of steroidogenic enzymes, cytochromes P450 aromatase (P450arom) and 17α-hydroxylase/17, 20-lyase (P450c17), involved in the synthesis of estrogens and androgens respectively throughout fetal sexual development. Undifferentiated gonads of Spix cavy develop into ovaries in females after 25 days of gestation (DG), exhibiting P450arom immunoreactivity. After 25 DG, paramesonephric ducts develop and form oviducts, uterine horns and cranial portion of the vagina. The caudal portion of the vagina originates from the urogenital sinus, and a vaginal closure membrane is present at the end of gestation. Partial channeling of the urethra into the clitoris occurs after 40 DG, but complete channeling never occurs. A preputial meatus emerges near the tip of organ. In males, undifferentiated gonads develop into testes at 25 DG and develop immunoreactivity for P450c17, which is required for androgens synthesis and likely maintenance of mesonephric ducts. Mesonephric ducts develop subsequently, forming the epididymis and ductus deferens. The pelvic urethra develops after 25 DG with channeling into the penis occurring around 30 DG. This is the first morphological study describing the process of sexual differentiation during gestation in a hystricomorph rodent and one of the most comprehensive analyses conducted in any mammal. Male genital organ development follows the general pattern described in other domestic mammals, but does not include formation of the baculum as occurs in mice and rats. In females, clitoral development includes partial canalization by the urethra and development of a preputial meatus. Further studies are required to clarify the mechanisms involved in the differentiative processes described.

A Longitudinal Study of Estrogen-Responsive Tissues and Hormone Concentrations in Infants Fed Soy Formula.

Purpose: Chemicals with hormonelike activity, such as estrogenic isoflavones, may perturb human development. Infants exclusively fed soy-based formula are highly exposed to isoflavones, but their physiologic responses remain uncharacterized. Estrogen-responsive postnatal development was compared in infants exclusively fed soy formula, cow-milk formula, and breast milk. Methods: We enrolled 410 infants born in Philadelphia-area hospitals between 2010 and 2014; 283 were exclusively fed soy formula (n = 102), cow-milk formula (n = 111), or breast milk (n = 70) throughout the study (birth to 28 or 36 weeks for boys and girls, respectively). We repeatedly measured maturation index (MI) in vaginal and urethral epithelial cells using standard cytological methods, uterine volume and breast-bud diameter using ultrasound, and serum estradiol and follicle-stimulating hormone levels. We estimated MI, organ-growth, and hormone trajectories by diet using mixed-effects regression splines. Results: Maternal demographics did not differ between cow-milk-fed and soy-fed infants but did differ between formula-fed and breastfed infants. Vaginal-cell MI trended higher (P = 0.01) and uterine volume decreased more slowly (P = 0.01) in soy-fed girls compared with cow-milk-fed girls; however, their trajectories of breast-bud diameter and hormone concentrations did not differ. We observed no significant differences between boys fed cow-milk vs soy formula; estradiol was not detectable. Breastfed infants differed from soy-formula-fed infants in vaginal-cell MI, uterine volume, and girls' estradiol and boys' breast-bud diameter trajectories. Conclusions: Relative to girls fed cow-milk formula, those fed soy formula demonstrated tissue- and organ-level developmental trajectories consistent with response to exogenous estrogen exposure. Studies are needed to further evaluate the effects of soy on child development.

External Genital Development, Urethra Formation, and Hypospadias Induction in Guinea Pig: A Double Zipper Model for Human Urethral Development.

OBJECTIVE: To determine whether the guinea pig phallus would be an appropriate model of human penile development, we characterized the embryology and sexual differentiation of guinea pig external genitalia and attended to induce hypospadias in males and tubular urethra formation in females pharmacologically. MATERIALS AND METHODS: The external genitalia of guinea pig were collected from genital swelling initiation to newborn stages, and scanning electronic microscopy and histology were performed to visualize the morphology and structure. Immunohistochemistry was used to determine the androgen receptor localization. Bicalutamide and methyltestosterone were given to pregnant dams to reveal the role and timing of androgen in guinea pig penile masculinization. RESULTS: Canalization and dorsal-to-ventral movement of the urethral canal develops the urethral groove in both sexes, and then the males perform distal-opening-proximal-closing to form tubular urethra. More nuclear-localized androgen receptor is found in proximal genital tubercles of males than in females at (E) 29. Antiandrogen treatment at E26-E30 can cause hypospadias, and methyltestosterone administration at E27-E31 can induce tubular urethra formation in females. CONCLUSION: Fetal development of the guinea pig phallus is homologous to that of humans. Although guinea pig has structures similar to mouse, the urethral groove and the tubular urethra formation are more similar to humans. Antiandrogen treatment causes hypospadias in males and additional androgen induces tubular urethra formation in females. Thus, guinea pig is an appropriate model for further study of cellular and molecular mechanisms involved in distal-opening-proximal-closing in tubular urethra formation and the evaluation of the pathophysiological processes of hypospadias.

Tissue Engineering of the Urethra: A Systematic Review and Meta-analysis of Preclinical and Clinical Studies.

CONTEXT: Urethra repair by tissue engineering has been extensively studied in laboratory animals and patients, but is not routinely used in clinical practice. OBJECTIVE: To systematically investigate preclinical and clinical evidence of the efficacy of tissue engineering for urethra repair in order to stimulate translation of preclinical studies to the clinic. EVIDENCE ACQUISITION: A systematic search strategy was applied in PubMed and EMBASE. Studies were independently screened for relevance by two reviewers, resulting in 80 preclinical and 23 clinical studies of which 63 and 13 were selected for meta-analysis to assess side effects, functionality, and study completion. Analyses for preclinical and clinical studies were performed separately. Full circumferential and inlay procedures were assessed independently. Evaluated parameters included seeding of cells and type of biomaterial. EVIDENCE SYNTHESIS: Meta-analysis revealed that cell seeding significantly reduced the probability of encountering side effects in preclinical studies. Remarkably though, cells were only sparsely used in the clinic (4/23 studies) and showed no significant reduction of side effects. ln 21 out of 23 clinical studies, decellularized templates were used, while in preclinical studies other biomaterials showed promising outcomes as well. No direct comparison to current clinical practice could be made due to the limited number of randomized controlled studies. CONCLUSIONS: Due to a lack of controlled (pre)clinical studies, the efficacy of tissue engineering for urethra repair could not be determined. Meta-analysis outcome measures were similar to current treatment options described in literature. Surprisingly, it appeared that favorable preclinical results, that is inclusion of cells, were not translated to the clinic. Improved (pre)clinical study designs may enhance clinical translation. PATIENT SUMMARY: We reviewed all available literature on urethral tissue engineering to assess the efficacy in preclinical and clinical studies. We show that improvements to (pre)clinical study design is required to improve clinical translation of tissue engineering technologies.