Neurovascular anatomy of the developing human fetal penis and clitoris.

The human penile and clitoral development begins from a morphologically indifferent genital tubercle. Under the influence of androgen, the genital tubercle forms the penis by forming a tubular urethra within the penile shaft. Without the effect of the androgen, the genital tubercle differentiates into the clitoris, and a lack of formation of the urethra within the clitoris is observed. Even though there are similarities during the development of the glans penis and glans clitoris, the complex canalization occurring along the penile shaft eventually leads to a morphological difference between the penis and clitoris. Based on the morphological differences, the main goal of this study was to define the vascular and neuronal anatomy of the developing penis and clitoris between 8 and 12 weeks of gestation using laser scanning confocal microscopy. Our results demonstrated there is a co-expression of CD31, which is an endothelial cell marker, and PGP9.5, which is a neuronal marker in the penis where the fusion is actively occurring at the ventral shaft. We also identified a unique anatomical structure for the first time, the clitoral ridge, which is a fetal structure running along the clitoral shaft in the vestibular groove. Contrary to previous anatomical findings which indicate that the neurovascular distribution in the developing penis and clitoris is similar, in this study, laser scanning confocal microscopy enabled us to demonstrate finer differences in the neurovascular anatomy between the penis and clitoris.

Ovotesticular cords and ovotesticular follicles: New histologic markers for human ovotesticular syndrome.

INTRODUCTION: The presence of an ovotestis is a rare difference of sex development. The diagnosis can be difficult with the gold standard being the presence of both testicular cords and ovarian follicles within the same gonad. OBJECTIVE: Herein we describe two new markers of ovotesticular syndrome: ovotesticular cords and ovotesticular follicles. STUDY DESIGN: Twenty human gonads with a previous diagnosis of ovotestis were re-stained with markers for testicular cords (SOX9, TSPY, SALL4, DDX4, cP450, AR, α-actin) and ovarian tissue (FOXL2, SALL4, DDX4). Ovotesticular cords were defined as structures expressing both testicular Sertoli cell marker (SOX9) and an ovarian follicular cell marker (FOXL2), and in Y chromosome positive specimens, TSPY-positive testicular germ cells. Ovotesticular follicles were defined as a hybrid ovarian follicle containing FOXL2-positive granulosa cells and a central oocyte, but also containing cells expressing the testicular Sertoli cell marker, SOX9, intermingled within FOXL2-positive granulosa cells and male and female germ cells. RESULTS: Six of twenty ovotestis did not meet our criterion for the diagnosis of ovotestis lacking the histologic evidence of both testicular and ovarian tissue. The remaining 13 patients in which 14 separate specimens were evaluated, contained ovotestis defined by the presence of testicular cords and ovarian follicles. Eleven of the 14 ovotestis specimens (79 %) contained ovotesticular cords. Four of 11 ovotestis specimens (36 %) contained ovotesticular follicles. DISCUSSION: We recommend using eight immunohistochemical markers to diagnose an ovotestis: 1) SOX9, TSPY, SALL4, DDX4, cytochrome P450, AR, smooth muscle α-actin for the testicular component and FOXL2 and SALL4, DDX4 for the ovarian component. SOX9 and TSPY (useful only in the presence of a Y karyotype) are specific testicular markers and FOXL2 the only specific ovarian marker. We found ovotesticular cords and ovotesticular follicles in both human bipolar and mixed ovotestis specimens both with and without the presence of the Y chromosome. The clinical significance of ovotesticular cords and follicles remains unknown. We did not observe any obvious abnormalities in cellular architecture with the juxtaposition of testicular cells and ovarian cells. CONCLUSION: We have identified two new structures in humans with ovotestis, ovotesticular cords and ovotesticular follicles (Figure), which appears to be additional markers to facilitate the diagnosis of ovotesticular gonads.

Spatial transcriptomics identifies candidate stromal drivers of benign prostatic hyperplasia.

Benign prostatic hyperplasia (BPH) is the nodular proliferation of the prostate transition zone in older men, leading to urinary storage and voiding problems that can be recalcitrant to therapy. Decades ago, John McNeal proposed that BPH originates with the "reawakening" of embryonic inductive activity by adult prostate stroma, which spurs new ductal proliferation and branching morphogenesis. Here, by laser microdissection and transcriptional profiling of the BPH stroma adjacent to hyperplastic branching ducts, we identified secreted factors likely mediating stromal induction of prostate glandular epithelium and coinciding processes. The top stromal factors were insulin-like growth factor 1 (IGF1) and CXC chemokine ligand 13 (CXCL13), which we verified by RNA in situ hybridization to be coexpressed in BPH fibroblasts, along with their cognate receptors (IGF1R and CXCR5) on adjacent epithelium. In contrast, IGF1 but not CXCL13 was expressed in human embryonic prostate stroma. Finally, we demonstrated that IGF1 is necessary for the generation of BPH-1 cell spheroids and patient-derived BPH cell organoids in 3D culture. Our findings partially support historic speculations on the etiology of BPH and provide what we believe to be new molecular targets for rational therapies directed against the underlying processes driving BPH.

Androgenic induction of penile features in postnatal female mouse external genitalia from birth to adulthood: Is the female sexual phenotype ever irreversibly determined?

Female mice were treated for 35 days from birth to 60 days postnatal (P0, [birth], P5, P10, P20 and adult [∼P60]) with dihydrotestosterone (DHT). Such treatment elicited profound masculinization the female external genitalia and development of penile features (penile spines, male urogenital mating protuberance (MUMP) cartilage, corpus cavernosum glandis, corporal body, MUMP-corpora cavernosa, a large preputial space, internal preputial space, os penis). Time course studies demonstrated that DHT elicited canalization of the U-shaped clitoral lamina to create a U-shaped preputial space, preputial lining epithelium and penile epithelium adorned with spines. The effect of DHT was likely due to signaling through androgen receptors normally present postnatally in the clitoral lamina and associated mesenchyme. This study highlights a remarkable male/female difference in specification and determination of urogenital organ identity. Urogenital organ identity in male mice is irreversibly specified and determined prenatally (prostate, penis, and seminal vesicle), whereas many aspects of the female urogenital organogenesis are not irreversibly determined at birth and in the case of external genitalia are not irreversibly determined even into adulthood, the exception being positioning of the female urethra, which is determined prenatally.

Development of the human ovary: Fetal through pubertal ovarian morphology, folliculogenesis and expression of cellular differentiation markers.

A definition of normal human fetal and early postnatal ovarian development is critical to the ability to accurately diagnose the presence or absence of functional ovarian tissue in clinical specimens. Through assembling an extensive histologic and immunohistochemical developmental ontogeny of human ovarian specimens from 8 weeks of gestation through 16 years of postnatal, we present a comprehensive immunohistochemical mapping of normal protein expression patterns in the early fetal through post-pubertal human ovary and detail a specific expression-based definition of the early stages of follicular development. Normal fetal and postnatal ovarian tissue is defined by the presence of follicular structures and characteristic immunohistochemical staining patterns, including granulosa cells expressing Forkhead Box Protein L2 (FOXL2). However, the current standard array of immunohistochemical markers poorly defines ovarian stromal tissue, and additional work is needed to identify new markers to advance our ability to accurately identify ovarian stromal components in gonadal specimens from patients with disorders of sexual differentiation.

Mouse-human species differences in early testicular development and its implications.

The mouse has been used as a model of human organogenesis with the tacit assumption that morphogenetic and molecular mechanisms in mice are translatable to human organogenesis. While many morphogenetic and molecular mechanisms are shared in mice and humans, many anatomic, morphogenetic, and molecular differences have been noted. Two critical gaps in our knowledge prevent meaningful comparisons of mouse versus human testicular development: (a) human testicular development is profoundly under-represented in the literature, and (b) an absence of a detailed day-by-day ontogeny of mouse testicular development from E11.5 to E16.5 encompassing the ambisexual stage to seminiferous cord formation. To address these deficiencies, histologic and immunohistochemical studies were pursued in comparable stages of mouse and human testicular development with a particular emphasis on Leydig, Sertoli and myoid cells through review of the literature and new observations. For example, an androgen-receptor-positive testicular medulla is present in the developing human testis but not in the developing mouse testis. The human testicular medulla and associated mesonephros were historically described as the source of Sertoli cells in seminiferous cords. Consistent with this idea, the profoundly androgen receptor (AR)-positive human testicular medulla was shown to be a zone of mesenchymal to epithelial transition and a zone from which AR-positive cells appear to migrate into the human testicular cortex. While mouse Sertoli and Leydig cells have been proposed to arise from coelomic epithelium, Sertoli (SOX9) or Leydig (HSD3B1) cell markers are absent from the immediate coelomic zone of the developing human testis, perhaps because Leydig and Sertoli cell precursors are undifferentiated when they egress from the coelomic epithelium. The origin of mouse and human myoid cells remains unclear. This study provides a detailed comparison of the early stages of testicular development in human and mouse emphasizing differences in developmental processes.

A model to study human ovotesticular syndrome.

Ovotesticular syndrome is a rare disorder of sex development characterized by the presence of testicular and ovarian tissue. The histologic characteristics of human testicular tissue are well defined by the presence of seminiferous cords or tubules containing TSPY-positive germ cells and Sox9-positive Sertoli cells surrounded by interstitial tissue containing cytochrome P450-positive Leydig cells and smooth muscle α-actin-positive peritubular myoid cells. The histological characteristics of the ovary can be defined by germ cell nests and the development of follicles. In contrast to the testis, the ovary has a paucity of defined specific protein markers, with the granulosa cell marker FOXL2 being the most widely used. In practice, defining the ovarian component of the ovotestis can be quite difficult. We developed a model of human ovotesticular syndrome by combining fetal human testis and ovary in a xenograft model. Ovotesticular xenografts were grown under the renal capsules of gonadectomized athymic nude mice for 6-32 weeks along with age matched control grafts of fetal testis and ovary. Forty ovotesticular xenografts and their controls were analyzed by histology, immunohistochemistry, and fluorescent in situ hybridization to determine the protein expression and karyotype of the cells within the grafts. The ovotesticular xenografts exhibited recognizable testicular and ovarian tissue based on testis-specific and ovary-specific markers defined above. The xenografts simulated a bipolar ovotestis in which the testicular and ovarian elements retain their separate histological characteristics and are separated by a well-defined border. This contrasts with the compartmentalized ovotestis previously described in the literature where the testicular tissue is surrounded by ovarian tissue or a mixed histology where testicular and ovarian tissues are interspersed throughout the gonad. In conclusion, we have characterized a human model of ovotestis which will allow a deeper understanding of ovotestis development in humans and facilitate a more accurate diagnosis of the ovotesticular syndrome.

Ontogeny of mouse Sertoli, Leydig and peritubular myoid cells from embryonic day 10 to adulthood.

We present a comprehensive description of the differentiating somatic cell types (Sertoli, Leydig, and peritubular myoid cells) of the mouse testis from embryonic day 10.5 (E10.5) to adulthood, postnatal day 60 (P60). Immunohistochemistry was used to analyze expression of: Sox9 (a Sertoli cell marker), 3ßHSD-1 (a fetal Leydig cell marker), 3ßHSD-6 (an adult Leydig cell marker), α-actin (a peritubular myoid cell marker), and androgen receptor (a marker of all three somatic cell types). The temporal-spatial expression of these markers was used to interrogate findings of earlier experimental studies on the origin of Sertoli, Leydig and peritubular myoid cells, as well as extend previous descriptive studies across a broader developmental period (E10.5-P60). Such comparisons demonstrate inconsistencies that require further examination and raise questions regarding conservation of developmental mechanisms across higher vertebrate species.

Role of mesonephric contribution to mouse testicular development revisited.

The role of the mesonephros in testicular development was re-evaluated by growing embryonic day 11.5 (E11.5) mouse testes devoid of mesonephros for 8-21 days in vivo under the renal capsule of castrated male athymic nude mice. This method provides improved growth conditions relative to previous studies based upon short-term (4-7 days) organ culture. Meticulous controls involved wholemount examination of dissected E11.5 mouse testes as well as serial sections of dissected E11.5 mouse testes which were indeed shown to be devoid of mesonephros. As expected, grafts of E11.5 mouse testes with mesonephros attached formed seminiferous tubules and also contained mesonephric derivatives. Grafts of E11.5 mouse testes without associated mesonephros also formed seminiferous tubules and never contained mesonephric derivatives. The consistent absence of mesonephric derivatives in grafts of E11.5 mouse testes grafted alone is further proof of the complete removal of the mesonephros from the E11.5 mouse testes. The testicular tissues that developed in grafts of E11.5 mouse testes alone contained canalized seminiferous tubules composed of Sox9-positive Sertoli cells as well as GENA-positive germ cells. The seminiferous tubules were surrounded by α-actin-positive myoid cells, and the interstitial space contained 3ßHSD-1-positive Leydig cells. Grafts of E11.5 GFP mouse testes into wild-type hosts developed GFP-positive vasculature indicating that E11.5 mouse testes contain vascular precursors. These results indicate that the E11.5 mouse testis contains precursor cells for Sertoli cells, Leydig cells, myoid cells and vasculature whose development and differentiation are independent of cells migrating from the E11.5 mesonephros.

Development of the human fetal testis: Morphology and expression of cellular differentiation markers.

A comprehensive immunohistochemical ontogeny of the developing human fetal testis has remained incomplete in the literature to date. We collected human fetal testes from 8 to 21 weeks of fetal age, as well as postnatal human testes at minipuberty, pre-pubertal, and pubertal stages. Immunohistochemistry was performed with a comprehensive panel of antigens targeting gonadocytes, Sertoli cells, fetal Leydig cells, peritubular myoid cells, and other hormonal and developmental targets. Testicular cords, precursor structures to seminiferous tubules, developed from 8 to 14 weeks of fetal age, separating the testis into the interstitial and intracordal compartments. Fetal gonadocytes were localized within the testicular cords and evaluated for Testis-Specific Protein Y, Octamer-binding transcription factor 4, Sal-like protein 4, and placental alkaline phosphatase expression. Fetal Sertoli cells were also localized in the testicular cords and evaluated for SRY-box Transcription Factor 9, inhibin, and anti-Mullerian hormone expression. Fetal Leydig cells were present in the interstitium and stained for cytochrome p450c17 and calretinin, while interstitial peritubular myoid cells were examined using smooth muscle α-actin staining. Androgen receptor expression was localized close to the testicular medulla at 8 weeks and then around the testicular cords in the interstitium as they matured in structure. Postnatal staining showed that Testis-Specific Protein Y remained positive of male gonadocytes throughout adulthood. Anti-Mullerian hormone, SRY-box Transcription Factor 9, and Steroidogenic factor 1 are expressed by the postnatal Sertoli cells at all ages examined. Leydig cell markers cytochrome p450c17 and calretinin are expressed during mini-puberty and puberty, but not expressed during the pre-pubertal period. Smooth muscle α-actin and androgen receptor were not expressed during mini-puberty or pre-puberty, but again expressed during the pubertal period. The ontogenic map of the human fetal and postnatal testicular structure and expression patterns described here will serve as a reference for future investigations into normal and abnormal testicular development.

Early development of the human embryonic testis.

Human gonadal development culminating in testicular differentiation is described through analysis of histologic sections derived from 33-day to 20-week human embryos/fetuses, focusing on early development (4-8 weeks of gestation). Our study updates the comprehensive studies of Felix (1912), van Wagenen and Simpson (1965), and Juric-Lekic et al. (2013), which were published in books and thus are unsearchable via PubMed. Human gonads develop from the germinal ridge, a thickening of coelomic epithelium on the medial side of the urogenital ridge. The bilateral urogenital ridges contain elements of the mesonephric kidney, namely the mesonephric duct, mesonephric tubules, and mesonephric glomeruli. The germinal ridge, into which primordial germ cells migrate, is initially recognized as a thickening of coelomic epithelium on the urogenital ridge late in the 4th week of gestation. Subsequently, in the 5th week of gestation, a dense mesenchyme develops sub-adjacent to the epithelium of the germinal ridge, and together these elements bulge into the coelomic cavity forming bilateral longitudinal ridges attached to the urogenital ridges. During development, primordial cells migrate into the germinal ridge and subsequently into testicular cords that form within the featureless dense mesenchyme of the germinal ridge at 6-8 weeks of gestation. The initial low density of testicular cords seen at 8 weeks remodels into a dense array of testicular cords surrounded by α-actin-positive myoid cells during the second trimester. Human testicular development shares many features with that of mice being derived from 4 elements: coelomic epithelium, sub-adjacent mesenchyme, primordial germ cells, and the mesonephros.

Human urogenital sinus mesenchyme is an inducer of prostatic epithelial development.

OBJECTIVE: To determine whether human fetal urogenital sinus mesenchyme (UGM) can induce prostatic development in a responsive mouse epithelium. METHOD: Male and female human fetal UGM was combined with mouse urinary bladder epithelium (BLE), and the resultant human UGM + mouse BLE tissue recombinants were grown under renal capsules of male athymic mice. Human male and female UGM was derived from reproductive tracts 9 and 14 weeks of gestation obtained following elective termination of pregnancy. At these ages prostatic ducts had already emerged from the urogenital sinus epithelium, and the human UGM remained contaminated with human prostatic epithelium. This unavoidable problem was tolerated because the induced mouse prostatic epithelium could be distinguished from contaminating human prostatic epithelium. RESULTS: The simple columnar epithelium induced from mouse bladder epithelium by human male and female UGM resembled mouse prostatic epithelium by: (a) histology, (b) the pattern of basal cell distribution, (c) Hoechst dye nuclear staining, (d) expression of NKX3.1, (e) the pattern of androgen receptor expression and (f) the expression of probasin, a mouse prostatic secretory protein. Summary/Interpretation: These findings provide validation for mouse as a model of human prostatic development as the molecular dialogue involved in mesenchymal-epithelial interactions are sufficiently conserved that human UGM can induce mouse bladder epithelium to undergo prostatic development.

Stromal androgen and hedgehog signaling regulates stem cell niches in pubertal prostate development.

Stromal androgen-receptor (AR) action is essential for prostate development, morphogenesis and regeneration. However, mechanisms underlying how stromal AR maintains the cell niche in support of pubertal prostatic epithelial growth are unknown. Here, using advanced mouse genetic tools, we demonstrate that selective deletion of stromal AR expression in prepubescent Shh-responsive Gli1-expressing cells significantly impedes pubertal prostate epithelial growth and development. Single-cell transcriptomic analyses showed that AR loss in these prepubescent Gli1-expressing cells dysregulates androgen signaling-initiated stromal-epithelial paracrine interactions, leading to growth retardation of pubertal prostate epithelia and significant development defects. Specifically, AR loss elevates Shh-signaling activation in both prostatic stromal and adjacent epithelial cells, directly inhibiting prostatic epithelial growth. Single-cell trajectory analyses further identified aberrant differentiation fates of prostatic epithelial cells directly altered by stromal AR deletion. In vivo recombination of AR-deficient stromal Gli1-lineage cells with wild-type prostatic epithelial cells failed to develop normal prostatic epithelia. These data demonstrate previously unidentified mechanisms underlying how stromal AR-signaling facilitates Shh-mediated cell niches in pubertal prostatic epithelial growth and development.

Cornification and classical versus nonclassical androgen receptor signaling in mouse penile/preputial development.

Mouse penile development is androgen-dependent. During development of male and female external genitalia, an internal ectodermal epithelial structure forms called the preputial lamina. At puberty the male preputial lamina canalizes to create the preputial space, effectively splitting into two layers: (a) the epithelial lining of the prepuce and (b) the surface epithelium of the penis. The female preputial lamina does not canalize, and instead remodels into the inverted U-shaped clitoral lamina of the adult female mouse. Androgen-dependent penile development was studied in transgenic mice with pathway-selective AR mutant transgenes through which AR signaling was activated either via the classical (AR-C) or the nonclassical pathway (AR-NC). Penile development and canalization of the preputial lamina was observed in AR-C and wild-type male mice naturally having both AR-C and AR-NC pathways. Conversely, clitoral development occurred in AR null (lacking both AR-C and AR-NC pathways) and AR-NC mice. The process of canalization of the preputial lamina seen in wild-type, AR-C and AR-C/AR-NC male mice involved cornification of the preputial lamina which involved up-regulation of keratin 10 and loricrin. Such up-regulation of these epidermal proteins was absent in the developing and adult clitoral lamina seen in wild-type female mice and AR-NC and AR null male (XY) mice. Thus, signaling through AR-C is sufficient to initiate and promote penile development and canalization of the preputial lamina, a process involving epithelial cornification.

Estrogens and development of the mouse and human external genitalia.

The Jost hypothesis states that androgens are necessary for normal development of the male external genitalia. In this review, we explore the complementary hypothesis that estrogens can elicit abnormal development of male external genitalia. Herein, we review available data in both humans and mice on the deleterious effects of estrogen on external genitalia development, especially during the "window of susceptibility" to exogenous estrogens. The male and female developing external genitalia in both the human and mouse express ESR1 and ESR2, along with the androgen receptor (AR). Human clinical data suggests that exogenous estrogens can adversely affect normal penile and urethral development, resulting in hypospadias. Experimental mouse data also strongly supports the idea that exogenous estrogens cause penile and urethral defects. Despite key differences, estrogen-induced hypospadias in the mouse displays certain morphogenetic homologies to human hypospadias, including disruption of urethral fusion and preputial abnormalities. Timing of estrogenic exposure, or the "window of susceptibility," is an important consideration when examining malformations of the external genitalia in both humans and mice. In addition to a review of normal human and mouse external genital development, this article aims to review the present data on the role of estrogens in normal and abnormal development of the mouse and human internal and external genitalia. Based on the current literature for both species, we conclude that estrogen-dependent processes may play a role in abnormal genital development.

Ontogeny of estrogen receptors in human male and female fetal reproductive tracts.

This paper reviews and provides new observations on the ontogeny of estrogen receptor alpha (ESR1) and estrogen receptor beta (ESR2) in developing human male and female internal and external genitalia. Included in this study are observations on the human fetal uterine tube, the uterotubal junction, uterus, cervix, vagina, penis and clitoris. We also summarize and report on the ontogeny of estrogen receptors in the human fetal prostate, prostatic urethra and epididymis. The ontogeny of ESR1 and ESR2, which spans from 8 to 21 weeks correlates well with the known "window of susceptibility" (7-15 weeks) for diethylstilbestrol (DES)-induced malformations of the human female reproductive tract as determined through examination of DES daughters exposed in utero to this potent estrogen. Our fairly complete mapping of the ontogeny of ESR1 and ESR2 in developing human male and female internal and external genitalia provides a mechanistic framework for further investigation of the role of estrogen in normal development and of abnormalities elicited by exogenous estrogens.