Development and morphogenesis of the Wolffian/epididymal duct, more twists and turns

Exploring Testicular Descent: Recent Findings and Future Prospects in Canine Cryptorchidism

BACKGROUND

Canine cryptorchidism, manifested by an abnormal testicular position, poses significant health risks and reproductive challenges in affected males. Despite a high prevalence, estimated at up to 10% in the canine population, a comprehensive understanding of its pathogenesis remains elusive. Studies in human cryptorchids and knockout mice have identified key factors involved in testicular descent, including INSL3, RXFP2, and AR. To date, only three DNA variants, found in the RXFP2, HMGA2, and KAT6A genes, have been associated with canine cryptorchidism.

SUMMARY

This review briefly summarizes current knowledge on testicular descent and the factors that regulate this process, based on cryptorchidism in humans and mice. It also highlights recent findings related to canine cryptorchidism, focusing on the INSL3, HMGA2, and KAT6A genes. The most significant results are discussed, with an emphasis on the role of the epididymis in testicular descent. This report presents insights that may facilitate further research aiming to broaden our understanding of canine cryptorchidism pathogenesis.

KEY MESSAGES

DNA polymorphism in the KAT6A gene, associated with changes in global H3K9 acetylation, as well as the DNA methylation pattern in the INSL3 gene, suggest that further research should strongly focus on epigenetic modifications. In addition, the development of the epididymo-testicular junction and the link between cryptorchidism prevalence and dog size should be further investigated.

Biomechanical properties of the capsule and extracellular matrix play a major role during the Wolffian/epididymal duct development

BACKGROUND

The epididymis is important for sperm maturation and without its proper development, male infertility will result. Biomechanical properties of tissues/organs play key roles during their morphogenesis, including the Wolffian duct. It is hypothesized that structural/bulk stiffness of the capsule and mesenchyme/extracellular matrix that surround the duct is a major biomechanical property that regulates Wolffian duct morphogenesis. These data will provide key information as to the mechanisms that regulate the development of this important organ.

OBJECTIVES

To measure the structural/bulk stiffness in Pascals (force/area) of the capsule and the capsule and mesenchyme together that surrounds the Wolffian duct during the development. To examine the relative membrane tension of mesenchymal cells during the Wolffian duct development. Since Ptk7 was previously shown to regulate ECM integrity and Wolffian duct elongation and coiling, the hypothesis that Ptk7 regulates structural/bulk stiffness and mesenchymal cell membrane tension was tested.

MATERIALS AND METHODS

Atomic force microscopy and a microsquisher compression apparatus were used to measure the structural stiffness. Biomechanical properties within the membranes of cells within the capsule and mesenchyme were examined using a membrane-tension fluorescent probe.

RESULTS AND DISCUSSION

The structural stiffness (Pascals) of the capsule and underlying mesenchyme was relatively constant during development, with a significant increase in the capsule at the later stages. However, this increase may reflect the ECM and associated mesenchyme being close to the capsule because the coiling of the duct pushed or compressed them into that space. Keeping the capsule and mesenchyme/ECM at constant stiffness would ensure that the duct will continue to coil under similar biomechanical forces throughout the development. Cells within the capsule and mesenchyme at different Wolffian duct regions during the development had varying degrees of membrane lipid tension. It is hypothesized that the dynamic changes ensure the duct is kept at a constant stiffness regardless of any external forces. Loss of Ptk7 resulted in an increase in stiffness at E18.5, which was presumable due to the loss of integrity of the ECM within the mesenchyme.

CONCLUSION

Biomechanical properties of the capsule and the mesenchyme/extracellular matrix that surround the Wolffian duct play an important role toward Wolffian duct morphogenesis, thereby allowing for the proper development of the epididymis and subsequent male fertility.

Collective cell dynamics and luminal fluid flow in the epididymis: A mechanobiological perspective

BACKGROUND

The mammalian epididymis is a specialized duct system that serves a critical role in sperm maturation and storage. Its distinctive, highly coiled tissue morphology provides a unique opportunity to investigate the link between form and function in reproductive biology. Although recent genetic studies have identified key genes and signaling pathways involved in the development and physiological functions of the epididymis, there has been limited discussion about the underlying dynamic and mechanical processes that govern these phenomena.

AIMS

In this review, we aim to address this gap by examining two key aspects of the epididymis across its developmental and physiological phases.

RESULTS AND DISCUSSION

First, we discuss how the complex morphology of the Wolffian/epididymal duct emerges through collective cell dynamics, including duct elongation, cell proliferation, and arrangement during embryonic development. Second, we highlight dynamic aspects of luminal fluid flow in the epididymis, essential for regulating the microenvironment for sperm maturation and motility, and discuss how this phenomenon emerges and interplays with epididymal epithelial cells.

CONCLUSION

This review not only aims to summarize current knowledge but also to provide a starting point for further exploration of mechanobiological aspects related to the cellular and extracellular fluid dynamics in the epididymis.

Single-cell transcriptomic profiling of the neonatal oviduct and uterus reveals new insights into upper Müllerian duct regionalization

The upper Müllerian duct (MD) is patterned and specified into two morphologically and functionally distinct organs, the oviduct and uterus. It is known that this regionalization process is instructed by inductive signals from the adjacent mesenchyme. However, the interaction landscape between epithelium and mesenchyme during upper MD development remains largely unknown. Here, we performed single-cell transcriptomic profiling of mouse neonatal oviducts and uteri at the initiation of MD epithelial differentiation (postnatal day 3). We identified major cell types including epithelium, mesenchyme, pericytes, mesothelium, endothelium, and immune cells in both organs with established markers. Moreover, we uncovered region-specific epithelial and mesenchymal subpopulations and then deduced region-specific ligand-receptor pairs mediating mesenchymal-epithelial interactions along the craniocaudal axis. Unexpectedly, we discovered a mesenchymal subpopulation marked by neurofilaments with specific localizations at the mesometrial pole of both the neonatal oviduct and uterus. Lastly, we analyzed and revealed organ-specific signature genes of pericytes and mesothelial cells. Taken together, our study enriches our knowledge of upper MD development, and provides a manageable list of potential genes, pathways, and region-specific cell subtypes for future functional studies.

RUNX transcription factors are essential in maintaining epididymal epithelial differentiation

Apart from the androgen receptor, transcription factors (TFs) that are required for the development and formation of the different segments of the epididymis have remained unknown. We identified TF families expressed in the developing epididymides, of which many showed segment specificity. From these TFs, down-regulation of runt related transcription factors (RUNXs) 1 and 2 expression coincides with epithelial regression in Dicer1 cKO mice. Concomitant deletion of both Runx1 and Runx2 in a mouse epididymal epithelial cell line affected cell morphology, adhesion and mobility in vitro. Furthermore, lack of functional RUNXs severely disturbed the formation of 3D epididymal organoid-like structures. Transcriptomic analysis of the epididymal cell organoid-like structures indicated that RUNX1 and RUNX2 are involved in the regulation of MAPK signaling, NOTCH pathway activity, and EMT-related gene expression. This suggests that RUNXs are master regulators of several essential signaling pathways, and necessary for the maintenance of proper differentiation of the epididymal epithelium.

Characterization of the human fetal gonad and reproductive tract by single-cell transcriptomics

During human fetal development, sex differentiation occurs not only in the gonads but also in the adjacent developing reproductive tract. However, while the cellular composition of male and female human fetal gonads is well described, that of the adjacent developing reproductive tract remains poorly characterized. Here, we performed single-cell transcriptomics on male and female human fetal gonads together with the adjacent developing reproductive tract from first and second trimesters, highlighting the morphological and molecular changes during sex differentiation. We validated different cell populations of the developing reproductive tract and gonads and compared the molecular signatures between the first and second trimesters, as well as between sexes, to identify conserved and sex-specific features. Together, our study provides insights into human fetal sex-specific gonadogenesis and development of the reproductive tract beyond the gonads.

Steroidogenic activity and morphological characterization of prenatal testes and epididymis of guinea pig (Cavia porcellus)

The present study aims to establish the morphological, morphometric, and immunostaining patterns of the steroidogenic enzymes 17β-HSD and 5α-reductase and androgen receptors (AR) during the prenatal development of the male gonad and epididymis of Cavia porcellus. Fetuses at 22, 25, 30, 40, 45, 50, and 60 days of gestation (DG) were used. Specimens were dissected and subjected to macroscopic, histological, histomorphometric, and immunohistochemical analyses. Genital and scrotal protrusions were identified in 22 DG embryos. Gonocytes were identified at 25 DG and the formation of primary testicular cords was observed at 30 DG. Through anatomical evaluation, we observed differentiation of the epididymis into the head, body, and tail at 45 DG. During development, there is a progressive decrease in the diameters of the testicular cords and epididymal ducts. 17β-HSD enzyme immunostaining was observed in Leydig cells at all ages, while 5α-reductase was observed in Leydig cell cytoplasm and gonocytes at 40, 50, and 60 DG. AR shows gonocyte labeling at 30 DG. Thus, from the second trimester of pregnancy, it is possible to observe patterns of anatomical development, such as genital and scrotal prominence (22 DG), the appearance of gonocytes in the testicular cords at 25 DG, and the beginning of the organization of primary testicular cords at 30 DG, suggesting sexual differentiation. The 17β-HSD, 5α-reductase, and ARs play an essential role in sexual development and differentiation, presenting immunostaining at different reproductive process times.

Single-cell transcriptomic profiling of the neonatal oviduct and uterus reveals new insights into upper Müllerian duct regionalization

The upper Müllerian duct (MD) is patterned and specified into two morphologically and functionally distinct organs, the oviduct and uterus. It is known that this regionalization process is instructed by inductive signals from the adjacent mesenchyme. However, the interaction landscape between epithelium and mesenchyme during upper MD development remains largely unknown. Here, we performed single-cell transcriptomic profiling of mouse neonatal oviducts and uteri at the initiation of MD epithelial differentiation (postnatal day 3). We identified major cell types including epithelium, mesenchyme, pericytes, mesothelium, endothelium, and immune cells in both organs with established markers. Moreover, we uncovered region-specific epithelial and mesenchymal subpopulations and then deduced region-specific ligand-receptor pairs mediating mesenchymal-epithelial interactions along the craniocaudal axis. Unexpectedly, we discovered a mesenchymal subpopulation marked by neurofilaments with specific localizations at the mesometrial pole of both the neonatal oviduct and uterus. Lastly, we analyzed and revealed organ-specific signature genes of pericytes and mesothelial cells. Taken together, our study enriches our knowledge of upper Müllerian duct development, and provides a manageable list of potential genes, pathways, and region-specific cell subtypes for future functional studies.

Vasopressin V1a receptor and oxytocin receptor regulate murine sperm motility differently

Specific receptors for the neurohypophyseal hormones, arginine vasopressin (AVP) and oxytocin, are present in the male reproductive organs. However, their exact roles remain unknown. To elucidate the physiological functions of pituitary hormones in male reproduction, this study first focused on the distribution and function of one of the AVP receptors, V1a. In situ hybridization analysis revealed high expression of the Avpr1a in Leydig cells of the testes and narrow/clear cells in the epididymis, with the expression pattern differing from that of the oxytocin receptor (OTR). Notably, persistent motility and highly proportional hyperactivation were observed in spermatozoa from V1a receptor-deficient mice. In contrast, OTR blocking by antagonist atosiban decreased hyperactivation rate. Furthermore, AVP stimulation could alter the extracellular pH mediated by the V1a receptor. The results highlight the crucial role of neurohypophyseal hormones in male reproductive physiology, with potential contradicting roles of V1a and OTR in sperm maturation. Our findings suggest that V1a receptor antagonists are potential therapeutic drugs for male infertility.

Transcriptomic profile comparison reveals conservation of ionocytes across multiple organs

Single-cell RNA sequencing has recently led to the identification of a flurry of rare, new cell types, such as the CFTR-high ionocytes in the airway epithelium. Ionocytes appear to be specifically responsible for fluid osmolarity and pH regulation. Similar cells exist in multiple other organs and have received various names, including intercalated cell in the kidney, mitochondria-rich cell in the inner ear, clear cell in the epididymis, and ionocyte in the salivary gland. Here, we compare the previously published transcriptomic profile of cells expressing FOXI1, the signature transcription factor expressed in airway ionocytes. Such FOXI1+ cells were found in datasets representing human and/or murine kidney, airway, epididymis, thymus, skin, inner ear, salivary gland, and prostate. This allowed us to assess the similarities between these cells and identify the core transcriptomic signature of this ionocyte 'family'. Our results demonstrate that, across all these organs, ionocytes maintain the expression of a characteristic set of genes, including FOXI1, KRT7, and ATP6V1B1. We conclude that the ionocyte signature defines a class of closely related cell types across multiple mammalian organs.

Hedgehog signaling regulates Wolffian duct development through the primary cilium†

Primary cilia play pivotal roles in embryonic patterning and organogenesis through transduction of the Hedgehog signaling pathway (Hh). Although mutations in Hh morphogens impair the development of the gonads and trigger male infertility, the contribution of Hh and primary cilia in the development of male reproductive ductules, including the epididymis, remains unknown. From a Pax2Cre; IFT88fl/fl knock-out mouse model, we found that primary cilia deletion is associated with imbalanced Hh signaling and morphometric changes in the Wolffian duct (WD), the embryonic precursor of the epididymis. Similar effects were observed following pharmacological blockade of primary cilia formation and Hh modulation on WD organotypic cultures. The expression of genes involved in extracellular matrix, mesenchymal-epithelial transition, canonical Hh and WD development was significantly altered after treatments. Altogether, we identified the primary cilia-dependent Hh signaling as a master regulator of genes involved in WD development. This provides new insights regarding the etiology of sexual differentiation and male infertility issues.

Emerging organoid models to study the epididymis in male reproductive toxicology

The importance of the epididymis on sperm maturation and consequently male fertility has been well documented. The pseudostratified epithelium of the epididymis is comprised of multiple cell types, including principal cells, which are the most abundant, and basal cells. The role of basal cells has been unclear and has been a source of discussion in the literature. However, the recent demonstration that these cells are multipotent or adult stem cells has opened new areas of research in epididymal biology. One such avenue is to understand the regulation of these stem cells, and to exploit their properties to develop tools for toxicological studies to elucidate the effects of chemicals on cell differentiation and epididymal function in vitro. Studies in both rat and mouse have shown that purified single epididymal basal cells cultured under 3D conditions can proliferate and differentiate to form organoids, or mini organs. Furthermore, these epididymal basal stem cells can self-renew and differentiate into other epididymal cell types. It is known that during epididymal development, basal cells are derived from undifferentiated columnar cells, which have been reported to share common properties to stem cells. Like basal cells, these undifferentiated columnar cells can also form organoids under 3D culture conditions and can differentiate into basal, principal and clear cells. Organoids derived from either basal cells or columnar cells offer unique models for toxicology studies and represent an exciting and emerging approach to understand the epididymis.

[Inguinal and Scrotal Diseases in Children and Adolescents]

In children and adolescents, inguinal and scrotal diseases are relatively common, and imaging is very useful for the diagnosis and differential diagnosis of these diseases. Therefore, it is important to understand the imaging findings of these diseases. In this article, we classify these diseases into small testes, cryptorchidism, patent processus vaginalis, acute scrotum pain, trauma, testicular tumors, and others and describe their characteristic findings.

Crucial Convolution: Genetic and Molecular Mechanisms of Coiling during Epididymis Formation and Development in Embryogenesis

As embryonic development proceeds, numerous organs need to coil, bend or fold in order to establish their final shape. Generally, this occurs so as to maximise the surface area for absorption or secretory functions (e.g., in the small and large intestines, kidney or epididymis); however, mechanisms of bending and shaping also occur in other structures, notably the midbrain–hindbrain boundary in some teleost fish models such as zebrafish. In this review, we will examine known genetic and molecular factors that operate to pattern complex, coiled structures, with a primary focus on the epididymis as an excellent model organ to examine coiling. We will also discuss genetic mechanisms involving coiling in the seminiferous tubules and intestine to establish the final form and function of these coiled structures in the mature organism.

Testicular, Epididymal and Vasal Anomalies in Pediatric Patients with Cryptorchid Testes and Testes with Communicating Hydrocele

The goal of this study was to determine the prevalence of the testicular, epididymal, and vasal anomalies (TEVA) in cryptorchid and communicating hydrocele pediatric patients. Six hundred and ninety-one prepubertal boys underwent inguinal exploration for 741 undescended (UDT) or hydrocele testes. Two hundred and fifty-five TEVA were detected in 154 UDT boys, compared to 32 defects in 24 hydrocele patients (p < 0.001). The TEVA were more frequent in bilateral UDT (p = 0.009). Multiple defects were observed more frequently in the intra-abdominal testicles (p = 0.028). A correlation was found between the testicular atrophy index (TAI) and the incidence and number of TEVA in the UDT boys (p < 0.001). The smaller the testis (higher TAI), the more the defects that appeared in it and the higher the frequency of their appearance. Another correlation was established between testis position and the incidence and number of TEVA (p < 0.001). The higher the testis position, the more the defects that appeared in it and the higher the frequency of their appearance. A correlation was established between the position and the volume of the affected testis (p < 0.001). The higher the gonad position, the more severe the atrophy observed in it. The TEVA were more frequent in the UDT boys than in the hydrocele patients. We revealed that the risk of abnormal fusion between the testis, epididymis, and vas deferens is connected with the testis position (intra-abdominal testes) and bilateral non-descent.

Mechanical Feedback Control for Multicellular Tissue Size Maintenance: A Minireview

All living tissues and organs have their respective sizes, critical to various biological functions, such as development, growth, and homeostasis. As tissues and organs generally converge to a certain size, intrinsic regulatory mechanisms may be involved in the maintenance of size regulation. In recent years, important findings regarding size regulation have been obtained from diverse disciplines at the molecular and cellular levels. Here, I briefly review the size regulation of biological tissues from the perspective of control systems. This minireview focuses on how feedback systems engage in tissue size maintenance through the mechanical interactions of constituent cell collectives through intracellular signaling. I introduce a general framework of a feedback control system for tissue size regulation, followed by two examples: maintenance of epithelial tissue volume and epithelial tube diameter. The examples deliver the idea of how cellular mechano-response works for maintaining tissue size.

Ex vivo development of the entire mouse fetal reproductive tract by using microdissection and membrane-based organ culture techniques

Ex vivo explant culture is an appealing alternative to in vivo studies on fetal reproductive organ development. There is extensive literature on ex vivo methods of growing the fetal gonad. However, a method for culturing the whole fetal reproductive tract that has a different shape and size has not been documented. Here, with careful dissection and proper tissue orientation, we successfully cultured the entire bicornuate reproductive tracts from mouse embryos of both sexes on the Transwell insert membrane. The cultured reproductive tract system undergoes sexually dimorphic establishment and region-specific morphogenesis comparable to in vivo development of their counterparts. To test this culture method's applications, we used chemical treatment (dihydrotestosterone and BMS 564929) and genetic cellular ablation mouse model (Gli1-CreER; Rosa-DTA) to investigate the roles of androgen signaling and Gli1⁺ mesenchyme in Wolffian duct development. Dihydrotestosterone and BMS 564929 promoted the ectopic maintenance of Wolffian ducts in cultured XX tissues. The efficient and specific elimination of Gli1⁺ mesenchyme was successfully achieved in the cultured tissues, resulting in defective coiling of Wolffian ducts. These results demonstrate the amenability of this organ culture method for chemical and genetic manipulations that are otherwise difficult to study in vivo. Taken together, the establishment of this organ culture method provides a valuable tool complementary to in vivo studies for understanding fetal reproductive tract development in mice.

The Rete Testis: Development and Role in Testis Function

Abstract

The rete testis connects seminiferous tubules in which germ cells develop to the efferent ducts and the epididymis, where gametes mature and gain mobility. Several recent studies have thoroughly explored the morphogenesis of this structure in mice during embryonic and postnatal periods. A part of the rete testis has been shown to derive from the precursors of gonad somatic cells before sex determination. The other part forms from embryonal Sertoli cells of testis cords adjacent to the mesonephros. The transformation of Sertoli cells into rete testis cells is apparently not limited to the embryonic stage of development and continues during postnatal testis development. Recently, it was found that the rete testis participates in the formation and maintenance of specialized Sertoli cells in terminal segments of seminiferous tubules, transitional zones. Current views suggest that the transitional zones of the seminiferous tubules may represent a niche for spermatogonial stem cells, the site of the prolonged proliferation of Sertoli cells in the pubertal and postpubertal periods of testis development, and also could be a generator of spermatogenic waves. To sum up, the rete testis transports gametes from the testis to the epididymis, maintains pressure within seminiferous tubules, regulates the composition of the testicular fluid, and impacts the spermatogenic process itself.

Development of a putative adverse outcome pathway network for male rat reproductive tract abnormalities with specific considerations for the androgen sensitive window of development

Structured approaches like the adverse outcome pathway (AOP) framework offer great potential for depicting complex toxicological processes in a manner that can facilitate informed integration of mechanistic information in regulatory decisions. While this concept provides a structure for organizing evidence and facilitates consistency in evidence integration; the process, inputs, and manner in which AOPs and AOP networks are developed is still evolving. Following the OECD guiding principles of AOP development, we propose three AOPs for male reproductive tract abnormalities and derive a putative AOP network. The AOPs were developed using a fundamental understanding of the developmental biology of the organs of interest, paying close attention to the gestational timing of key events (KEs) to very specifically inform the domain of life stage applicability for the key event relationships (KERs). Chemical stressor data primarily from studies on low molecular weight phthalates (LMWPs) served to 'bound' the pathways of focus in this dynamic period of development and were integrated with the developmental biology data through an iterative process to define KEs and conclude on the extent of evidence in support of the KERs. The AOPs developed describe the linkage between 1) a decrease in Insl3 gene expression and cryptorchidism, 2) the sustained expression of Coup-tfII and hypospadias and 3) the sustained expression of Coup-tfII and altered Wolffian duct development/ epididymal agenesis. A putative AOP network linking AOP2 and AOP3 through decreased steroidogenic biosynthetic protein expression and converging of all AOPS at the population level impaired fertility adverse outcome is proposed. The network depiction specifies and displays the KEs aligned with their occurrence in gestational time. The pathways and network described herein are intended to catalyze collaborative initiatives for expansion into a larger network to enable effective data collection and inform alternative approaches for identifying stressors impacting this sensitive period of male reproductive tract development.

Cholesterol Contributes to Male Sex Differentiation Through Its Developmental Role in Androgen Synthesis and Hedgehog Signaling

Two specialized functions of cholesterol during fetal development include serving as a precursor to androgen synthesis and supporting hedgehog (HH) signaling activity. Androgens are produced by the testes to facilitate masculinization of the fetus. Recent evidence shows that intricate interactions between the HH and androgen signaling pathways are required for optimal male sex differentiation and defects of either can cause birth anomalies indicative of 46,XY male variations of sex development (VSD). Further, perturbations in cholesterol synthesis can cause developmental defects, including VSD, that phenocopy those caused by disrupted androgen or HH signaling, highlighting the functional role of cholesterol in promoting male sex differentiation. In this review, we focus on the role of cholesterol in systemic androgen and local HH signaling events during fetal masculinization and their collective contributions to pediatric VSD.

Anatomy, Endocrine Regulation, and Embryonic Development of the Rete Testis

Reproduction in males requires the transfer of spermatozoa from testis tubules via the rete system to the efferent ductules, epididymis, and vas deferens. The rete therefore forms an essential bridging system between the testis and excurrent ducts. Yet the embryonic origin and molecular regulation of rete testis development is poorly understood. This review examines the anatomy, endocrine control, and development of the mammalian rete testis, focusing on recent findings on its molecular regulation, identifying gaps in our knowledge, and identifying areas for future research. The rete testis develops in close association with Sertoli cells of the seminiferous cords, although unique molecular markers are sparce. Most recently, modern molecular approaches such as global RNA-seq have revealed the transcriptional signature of rete cell precursors, pointing to at least a partial common origin with Sertoli cells. In the mouse, genes involved in Sertoli cell development or maintenance, such as Sox9, Wt1, Sf1, and Dmrt1, are also expressed in cells of the rete system. Rete progenitor cells also express unique markers, such as Pax8, E-cadherin, and keratin 8. These must directly or indirectly regulate the physical joining of testis tubules to the efferent duct system and confer other physiological functions of the rete. The application of technologies such as single-cell RNA-seq will clarify the origin and developmental trajectory of this essential component of the male reproductive tract.

A coordinated progression of progenitor cell states initiates urinary tract development

The kidney and upper urinary tract develop through reciprocal interactions between the ureteric bud and the surrounding mesenchyme. Ureteric bud branching forms the arborized collecting duct system of the kidney, while ureteric tips promote nephron formation from dedicated progenitor cells. While nephron progenitor cells are relatively well characterized, the origin of ureteric bud progenitors has received little attention so far. It is well established that the ureteric bud is induced from the nephric duct, an epithelial duct derived from the intermediate mesoderm of the embryo. However, the cell state transitions underlying the progression from intermediate mesoderm to nephric duct and ureteric bud remain unknown. Here we show that nephric duct morphogenesis results from the coordinated organization of four major progenitor cell populations. Using single cell RNA-seq and Cluster RNA-seq, we show that these progenitors emerge in time and space according to a stereotypical pattern. We identify the transcription factors Tfap2a/b and Gata3 as critical coordinators of this progenitor cell progression. This study provides a better understanding of the cellular origin of the renal collecting duct system and associated urinary tract developmental diseases, which may inform guided differentiation of functional kidney tissue.

Zika virus disrupts the barrier structure and Absorption/Secretion functions of the epididymis in mice

Several studies have demonstrated that Zika virus (ZIKV) damages testis and leads to infertility in mice; however, the infection in the epididymis, another important organ of male reproductive health, has gained less attention. Previously, we detected lesions in the epididymis in interferon type I and II receptor knockout male mice during ZIKV infection. Herein, the pathogenesis of ZIKV in the epididymis was further assessed in the infected mice after footpad inoculation. ZIKV efficiently replicated in the epididymis, and principal cells were susceptible to ZIKV. ZIKV infection disrupted the histomorphology of the epididymis, and the effects were characterized by a decrease in the thickness of the epithelial layer and an increase in the luminal diameter, especially at the proximal end. Significant inflammatory cell infiltration was observed in the epididymis accompanied by an increase in the levels of interleukin (IL)-6 and IL-28. The expression of tight junction proteins was downregulated and associated with disordered arrangement of the junctions. Importantly, the expression levels of aquaporin 1 and lipocalin 8, indicators of the absorption and secretion functions of the epididymis, were markedly reduced, and the proteins were redistributed. These events synergistically altered the microenvironment for sperm maturation, disturbed sperm transport downstream, and may impact male reproductive health. Overall, these results provide new insights into the pathogenesis of the male reproductive damage caused by ZIKV infection and the possible contribution of epididymal injury into this process. Therefore, male fertility of the population in areas of ZIKV epidemic requires additional attention.

Unlike other mosquito-transmitted flaviviruses, ZIKV can persistently replicate in the male reproductive system and is sexually transmitted. ZIKV infection was reported to damage testis. However, ZIKV-induced epididymal injury was not investigated in detail. Clinically, epididymitis is closely associated with male infertility. In this study, a mouse model was used to demonstrate that ZIKV causes histomorphological and functional changes in the epididymis, which may alter the microenvironment of sperm maturation and movement and finally lead to male infertility. Therefore, long-term investigation of male reproductive health may be needed in the areas of ZIKV epidemic.

Estrogens and development of the rete testis, efferent ductules, epididymis and vas deferens

Estrogen has always been considered the female hormone and testosterone the male hormone. However, estrogen's presence in the testis and deleterious effects of estrogen treatment during development have been known for nearly 90 years, long before estrogen receptors (ESRs) were discovered. Eventually it was learned that testes actually synthesize high levels of estradiol (E2) and sequester high concentrations in the reproductive tract lumen, which seems contradictory to the overwhelming number of studies showing reproductive pathology following exogenous estrogen exposures. For too long, the developmental pathology of estrogen has dominated our thinking, even resulting in the "estrogen hypothesis" as related to the testicular dysgenesis syndrome. However, these early studies and the development of an Esr1 knockout mouse led to a deluge of research into estrogen's potential role in and disruption of development and function of the male reproductive system. What is new is that estrogen action in the male cannot be divorced from that of androgen. This paper presents what is known about components of the estrogen pathway, including its synthesis and target receptors, and the need to achieve a balance between androgen- and estrogen-action in male reproductive tract differentiation and adult functions. The review focuses on what is known regarding development of the male reproductive tract, from the rete testis to the vas deferens, and examines the expression of estrogen receptors and presence of aromatase in the male reproductive system, traces the evidence provided by estrogen-associated knockout and transgenic animal models and discusses the effects of fetal and postnatal exposures to estrogens. Hopefully, there will be enough here to stimulate discussions and new investigations of the androgen:estrogen balance that seems to be essential for development of the male reproductive tract.

How do we counsel men with obstructive azoospermia due to CF mutations?-a review of treatment options and outcomes

Obstructive azoospermia (OA) is a rare cause of male infertility, with Congenital Bilateral Absence of The Vas Deferens (CBAVD) being a major cause. A wealth of literature has established an irrefutable link between CFTR mutations and CBAVD, with CBAVD affecting almost all men with cystic fibrosis (CF) disease and a significant portion of men that are CFTR mutation carriers. In the past two decades, assisted reproductive technologies have made the prospect of fathering children a viable possibility in this subset of men, using a combination of sperm extraction techniques and intracystoplasmic sperm injection (ICSI). In order to assess techniques for sperm retrieval, as well as reproductive outcomes, a systemic search of the MEDLINE database was conducted for all articles pertaining to management options for CBAVD, and also all reports describing outcomes of these procedures in the CBAVD population. Both epididymal and testicular sperm extraction (TESE) are viable options for men with CBAVD, and though rigorous data are lacking, live birth rates range from 8% to 50% in most small retrospective series and subset analyses. In addition, there does not appear to be significant differences in the rate of live birth or complications and miscarriages between the various techniques, though further investigation into other factors that limit reproductive potential of men with CFTR mutations and CBAVD is warranted.

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.

Epididymal contribution to male infertility: An overlooked problem

The diagnosis and treatment of male infertility, excluding assisted conception, are limited because of, but not limited to, poor understanding of sperm post-testicular development and storage. Many may think that sperm dysfunction is only self-contained in the sperm cell itself as a result of defective spermatogenesis. However, it can also be a consequence of inadequate epididymal maturation following disorders of the epididymis. Improper epididymal functions can disturb semen parameters and sperm DNA integrity, result in high leucocyte concentrations and high numbers of immature germ cells and debris or even cause idiopathic infertility. To date, the data are limited regarding critical markers of sperm maturation and studies that can identify such markers for diagnosis and managing epididymal dysfunction are scarce. Therefore, this article aims to draw attention to recognise a disturbed epididymal environment as a potential cause of male infertility.

Postnatal differentiation and regional histological variations in the ductus epididymidis of the Congjiang Xiang pig

The Congjiang Xiang pig is a rare Chinese miniature breed whose epididymal histologic features through the postnatal development are poorly understood. To clarify the histomorphological differences between each region of epididymis during postnatal development, 24 male Congjiang Xiang pigs aged from neonatal (15 d), peri-puberty (30 d), puberty (60 d) to adult (180 d) stages, were examined. Postnatal differentiation of the different regions (I-V) of the epididymis started from birth and continued until maturity that showed regional variations. Developmental progression was disto-proximal. At the neonatal stage, Wolffian duct differentiation starts in the distal region, then ascends to the middle region which forms regions V, IV and III, respectively. A simple lined cuboidal in the epidydimal epithelial, which gradually differentiated into a pseudostratified columnar with stereocilia from neonatal to post-pubertal. After puberty cell rearrangement occurred in the epithelium, differentiation accelerated, and spermatozoon seen in the lumen, especially the lumen of region II. In region III, both halo and apical cells were frequently observed. At the post-pubertal stage, clear cells were frequently observed in Region IV-V, and the epididymal duct was markedly increased in size and fully packed with spermatozoa. The information presented in this study will be helpful for future evaluations of Congjiang Xiang pig fertility. After puberty cell rearrangement occurred in the epithelium, differentiation accelerated, and spermatozoon seen in the lumen, especially the lumen of region II. In region III, both halo and apical cells were frequently observed. At the post-pubertal stage, clear cells were frequently observed in Region IV-V, and the epididymal duct was markedly increased in size and fully packed with spermatozoa. The information presented in this study will be helpful for future evaluations of Congjiang Xiang pig fertility.

Polarized cellular mechano-response system for maintaining radial size in developing epithelial tubes

Size control in biological tissues involves multicellular communication via mechanical forces during development. Although fundamental cellular behaviours in response to mechanical stimuli underlie size maintenance during morphogenetic processes, the mechanisms underpinning the cellular mechano-response system that maintains size along an axis of a polarized tissue remain elusive. Here, we show how the diameter of an epithelial tube is maintained during murine epididymal development by combining quantitative imaging, mechanical perturbation and mathematical modelling. We found that epithelial cells counteract compressive forces caused by cell division exclusively along the circumferential axis of the tube to produce polarized contractile forces, eventually leading to an oriented cell rearrangement. Moreover, a mathematical model that includes the polarized mechano-responsive regime explains how the diameter of proliferating tubes is maintained. Our findings pave the way for an improved understanding of the cellular response to mechanical forces that involves collective multicellular behaviours for organizing diverse tissue morphologies.

Summary: Polarized cellular constriction responding to mechanical stress controls the diameter of a developing epithelial tube during murine epididymal development.

Convergent extension in mammalian morphogenesis

Convergent extension is a fundamental morphogenetic process that underlies not only the generation of the elongated vertebrate body plan from the initially radially symmetrical embryo, but also the specific shape changes characteristic of many individual tissues. These tissue shape changes are the result of specific cell behaviors, coordinated in time and space, and affected by the physical properties of the tissue. While mediolateral cell intercalation is the classic cellular mechanism for producing tissue convergence and extension, other cell behaviors can also provide similar tissue-scale distortions or can modulate the effects of mediolateral cell intercalation to sculpt a specific shape. Regulation of regional tissue morphogenesis through planar polarization of the variety of underlying cell behaviors is well-recognized, but as yet is not well understood at the molecular level. Here, we review recent advances in understanding the cellular basis for convergence and extension and its regulation.

Maternal Protein Restriction Modulates Angiogenesis and AQP9 Expression Leading to a Delay in Postnatal Epididymal Development in Rat

The maternal nutritional status is essential to the health and well-being of the fetus. Maternal protein restriction during the perinatal stage causes sperm alterations in the offspring that are associated with epididymal dysfunctions. Vascular endothelial growth factor (VEGF) and its receptor, VEGFr-2, as well as aquaporins (AQPs) are important regulators of angiogenesis and the epididymal microenvironment and are associated with male fertility. We investigated the effects of maternal protein restriction on epididymal angiogenesis and AQP expression in the early stages of postnatal epididymal development. Pregnant rats were divided into two experimental groups that received either a normoprotein (17% protein) or low-protein diet (6% protein) during gestation and lactation. At postnatal day (PND)7 and PND14, male offspring were euthanized, the epididymides were subjected to morphometric and microvascular density analyses and to VEGF-A, VEGF-r2, AQP1 and AQP9 expression analyses. The maternal low-protein diet decreased AQP9 and VEGFr-2 expression, decreased epididymal microvascularity and altered the morphometric features of the epididymal epithelium; no changes in AQP1 expression were observed at the beginning of postnatal epididymal development. Maternal protein restriction alters microvascularization and affects molecules involved in the epidydimal microenvironment, resulting in morphometric alterations related to a delay in the beginning of epididymis postnatal development.

Deficiency of the transcription factor PLAG1 results in aberrant coiling and morphology of the epididymis

Mice deficient in the transcription factor pleomorphic adenoma gene 1 (PLAG1) exhibit reproductive issues that are characterized, in part, by decreased progressive sperm motility in the male. However, the underlying cause of this impairment is unknown. As epididymal transit is critical for sperm maturation and motility, the morphology of the epididymis of Plag1-deficient mice was investigated and the spatial expression patterns of PLAG1 protein and mRNA were identified. Using X-gal staining and in situ hybridization, PLAG1 was shown to be widely expressed in both the epithelium and stroma in all regions of the mouse epididymis. Interestingly, the X-gal staining pattern was markedly different in the cauda, where it could be suggestive of PLAG1 secretion into the epididymal lumen. At all ages investigated, the morphology of epididymides from Plag1 knockout (KO) mice was aberrant; the tubule failed to elongate and coil, particularly in the corpus and cauda, and the cauda was malformed, lacking its usual bulbous shape. Moreover, the epididymides from Plag1 KO mice were significantly reduced in size relative to body weight. In 20% of Plag1-deficient mice, the left testicle and epididymis were lacking. The impaired morphogenesis of the epididymal tubule is likely to be a major contributing factor to the fertility problems observed in male Plag1-deficient mice. These results also establish PLAG1 as an important regulator of male reproduction, not only through its involvement in testicular sperm production, but also via its role in the development and function of the epididymis.

Independent erosion of conserved transcription factor binding sites points to shared hindlimb, vision and external testes loss in different mammals

Genetic variation in cis-regulatory elements is thought to be a major driving force in morphological and physiological changes. However, identifying transcription factor binding events that code for complex traits remains a challenge, motivating novel means of detecting putatively important binding events. Using a curated set of 1154 high-quality transcription factor motifs, we demonstrate that independently eroded binding sites are enriched for independently lost traits in three distinct pairs of placental mammals. We show that these independently eroded events pinpoint the loss of hindlimbs in dolphin and manatee, degradation of vision in naked mole-rat and star-nosed mole, and the loss of external testes in white rhinoceros and Weddell seal. We additionally show that our method may also be utilized with more than two species. Our study exhibits a novel methodology to detect cis-regulatory mutations which help explain a portion of the molecular mechanism underlying complex trait formation and loss.

Three-dimensional structure of efferent and epididymal ducts in mice

The aim of the present study was to clarify the detailed morphology of efferent and epididymal ducts in adult mice using three-dimensional (3D) analysis. We reconstructed efferent and epididymal ducts in three adult mice using serial paraffin sections and high-performance 3D reconstruction software to draw the core lines of all ducts. By comparing the 3D core lines with the histological features in serial sections, we obtained detailed information on the gross characteristics of the ducts and identified the duct divisions accurately. The intra-testicular rete testis penetrated the tunica albuginea at one place and turned into the extra-testicular rete testis, which branched once or twice to give rise to four efferent ducts within 0.5 mm from the tunica albuginea. As these ducts approached the epididymis, they converged into one again and changed abruptly into the initial segment (IS) of the epididymis. The average length from the tunica albuginea to the IS was 19.7 ± 3.1 mm. In one mouse, we found four additional efferent ducts diverging from the common region with blind ends. The epididymal duct was a single highly convoluted duct with no branch and an average length of 767 ± 26 mm. By dividing the epididymal duct into five regions based on its cytological features and periodic acid-Schiff stainability, we calculated the length and diameter of individual regions accurately. Furthermore, we clearly showed locations of the connective tissue septa that divide the head epididymis into several segments. The epididymal duct followed a complicated, winding path within each segment while drawing a large spiral overall along the circumference of the epididymis. Sometimes the direction of this spiral reversed between adjacent segments. The present study revealed the detailed 3D structures of efferent and epididymal ducts in adult mice.

Matrix metalloproteinase-dependent regulation of extracellular matrix shapes the structure of sexually differentiating mouse gonads

The extracellular matrix (ECM) proteins play an important role in the establishment of the sex-dependent structure of developing gonads. The matrix metalloproteinases (MMPs) are the major players in the regulation of ECM. Our hypothesis was that the MMPs-dependent regulation of EMC is crucial for the establishment of the correct, either testis or ovary, structure of developing gonad. We cultured developing mouse gonads in vitro in the presence of the MMPs inhibitors (α-2-macroglobulin, leupeptin, phosphoramidon) or the MMPs activator, APMA (4-aminophenylmercuric acetate). These inhibitors and activator inhibit/activate, to a different degree, matrix metalloproteinases, but the exact mechanism of inhibition/activation remains unknown. We found that the MMP inhibitors increased accumulation of ECM in the developing gonads. The α-2-macroglobulin had the weakest, and the phosphoramidon the strongest effect on the ECM and the structure of the gonads. The α-2-macroglobulin caused a slight increase of ECM and did not disrupt the gonad structure. Leupeptin led to the strong accumulation of ECM, resulted in the formation of the structures resembling testis cords in both testes and ovaries, and caused increase of apoptosis and complete loss of germ cells. Phosphoramidon caused the strongest accumulation of ECM, which separated individual cells and completely prevented intercellular adhesion both in the testes and in the ovaries. As a result of aberrant morphology, the sex of the phosphoramidon-treated gonads was morphologically unrecognizable. The APMA - the activator of MMP caused ECM loss, which led to the loss of cell adhesion, cell dispersion and an aberrant morphology of the gonads. These results indicate that the ECM accumulation is MMPs-dependent and that the correct amount and distribution of ECM during gonad development plays a key role in the formation of the gonad structure.

Seasonal variation of cell proliferation and apoptosis in the efferent ductules and epididymis of the Neotropical bat Artibeus lituratus (Chiroptera, Phyllostomidae)

The balance between cell proliferation and apoptosis is important for maintenance of male fertility, being influenced by a variety of stimuli including androgens and estrogens. However, studies concerning regulation of these processes along the male reproductive tract under physiological conditions are scarce. Therefore, in this study, we investigated the profile of cell proliferation and apoptosis in the efferent ductules and epididymis of the Neotropical bat Artibeus lituratus, a seasonal breeder that presents natural variation in components of the androgen and estrogen responsive systems along the circannual cycle. Low rates of cell proliferation and apoptosis were found in the efferent ductules and epididymis of A. lituratus during the reproductive period, as few epithelial cells were positive for MCM7 (proliferation marker) and cleaved caspase-3 or TUNEL (apoptosis markers). In contrast, during the regressive period, the rate of both proliferating and apoptotic cells was significantly higher in the epithelium lining the efferent ductules as well as throughout the epididymis. The increased proliferative activity at this phase was positively correlated with the expression of estrogen receptor alpha (ERα), whereas the variation in apoptosis appears to be unrelated to the local expression of androgen and estrogen receptors. Together, these data suggest that cell proliferation and apoptosis are differentially modulated in the efferent ductules and epididymis of A. lituratus during the annual reproductive cycle, and support the hypothesis that ERα may be important in preparing the male reproductive tract for sexual recrudescence.

Non-obstructive vas deferens and epididymis loss in cystic fibrosis rats

This study utilizes morphological and mechanistic endpoints to characterize the onset of bilateral atresia of the vas deferens in a recently derived cystic fibrosis (CF) rat model. Embryonic reproductive structures, including Wolffian (mesonephric) duct, Mullerian (paramesonephric) duct, mesonephric tubules, and gonad, were shown to mature normally through late embryogenesis, with involution of the vas deferens and/or epididymis typically occurring between birth and postnatal day 4 (P4), although timing and degree of atresia varied. No evidence of mucus obstruction, which is associated with pathology in other CF-affected tissues, was observed at any embryological or postnatal time point. Reduced epididymal coiling was noted post-partum and appeared to coincide with, or predate, loss of more distal vas deferens structure. Remarkably, α smooth muscle actin expression in cells surrounding duct epithelia was markedly diminished in CF animals by P2.5 when compared to wild type counterparts, indicating reduced muscle development. RNA-seq and immunohistochemical analysis of affected tissues showed disruption of developmental signaling by Wnt and related pathways. The findings have relevance to vas deferens loss in humans with CF, where timing of ductular damage is not well characterized and underlying mechanisms are not understood. If vas deferens atresia in humans begins in late gestation and continues through early postnatal life, emerging modulator therapies given perinatally might preserve and enhance integrity of the reproductive tract, which is otherwise absent or deficient in 97% of males with cystic fibrosis.

Presence of aberrant epididymal tubules revealing undifferentiated epithelial cells and absence of spermatozoa in a combined neuraminidase-3 and -4 deficient adult mouse model

Mammalian neuraminidases are responsible for the removal of sialic acids from glycoproteins and glycolipids and function in a variety of biological phenomena such as lysosomal catabolism and control of cell differentiation and growth. Disruption of Neu3 and Neu4 genes has led to the generation of a mouse model revealing severe neurological disorders. In this study a morphological analysis was performed on the epididymis of 3 month-old neu3^-/-neu4^-/- mice as compared with wild type animals. In neu3^-/-neu4^-/- mice the majority of tubules of the main epididymal duct were large and lined by differentiated epithelial cells, but revealing lysosomal abnormalities in principal and basally located cells. Of particular note was the presence of aberrant epididymal tubules (ATs) juxtaposed next to the main tubules. ATs were small and of different shapes. Layers of myoid cells encased ATs, which they shared with those of the main tubules, but no interstitial space existed between the two. While some ATs were a dense mass of cells, others revealed a distinct lumen devoid of spermatozoa. The latter revealed an undifferentiated epithelium consisting of cuboidal cells and basal cells, with junctional complexes evident at the luminal front. The absence of spermatozoa from the lumen of the ATs suggests that they were not in contact with the main duct, as also implied by the undifferentiated appearance of the epithelium suggesting lack of lumicrine factors. Despite the presence of ATs, the main duct contained ample spermatozoa, as the neu3^-/-neu4^-/- mice were fertile. Taken together the data suggest that absence of Neu3 and Neu4 leads to defects in cell adhesion and differentiation of epithelial cells resulting in aberrant tubular offshoots that fail to remain connected with the main duct. Hence Neu3 and Neu 4 play an essential role in the guidance of epithelial cells during early embryonic formation.

Turning mesoderm into kidney

The intermediate mesoderm is located between the somites and the lateral plate mesoderm and gives rise to renal progenitors that contribute to the three mammalian kidney types (pronephros, mesonephros and metanephros). In this review, focusing largely on murine kidney development, we examine how the intermediate mesoderm forms during gastrulation/axis elongation and how it progressively gives rise to distinct renal progenitors along the rostro-caudal axis. We highlight some of the potential signalling cues and core transcription factor circuits that direct these processes, up to the point of early metanephric kidney formation.

Protein tyrosine kinase 7 regulates extracellular matrix integrity and mesenchymal intracellular RAC1 and myosin II activities during Wolffian duct morphogenesis

Wolffian duct morphogenesis must be highly coordinated with its specialized function of providing an optimal microenvironment for sperm maturation. Without normal Wolffian duct morphogenesis, male infertility will result. Our previous study showed that mediolateral and radial intercalation of epithelial and mesenchymal cells respectively, were major drivers of ductal elongation and were regulated by protein tyrosine kinase 7 (PTK7), a member of the planar cell polarity (PCP) non-canonical Wnt pathway. To understand the mechanism by which PTK7 regulates cell rearrangement/intercalation, we investigated the integrity of the extracellular matrix (ECM) and the activity of intracellular cytoskeleton mediators following loss of Ptk7. Abnormal assembly of nephronectin, laminin, and collagen IV at the basement membrane and fibrosis-like deposition of fibrilla collagen in the interstitium were observed in Ptk7 knockout Wolffian ducts. Further, the activity levels of RAC1 and myosin II, two cytoskeleton mediators, decreased in the Ptk7 knockout mesenchyme compared to controls. In addition, in-vitro experiments suggested that alterations of ECM and cytoskeleton mediators resulted in changes in Wolffian duct morphogenesis. When in-vitro-cultured Wolffian ducts were treated with collagenase IV, the degree of cross-linked fibrilla collagen was reduced, Wolffian duct elongation and coiling were significantly reduced, and an expanded cyst-like duct was observed. When Wolffian ducts were treated with RAC1 inhibitor NSC23766, mesenchymal fibrilla collagen was disassembled, and Wolffian duct elongation was significantly reduced. Our findings provide evidence that PTK7 regulates ECM integrity and the activity levels of RAC1 and myosin II, which in turn regulates Wolffian duct morphogenesis and therefore, epididymal function.

CRISPR/Cas9-induced disruption of wt1a and wt1b reveals their different roles in kidney and gonad development in Nile tilapia

Wilms tumor 1 (Wt1) is an essential factor for urogenital system development. Teleosts have two wt1s, named as wt1a and wt1b. In this study, the expression pattern of wt1a and wt1b and their functions on the urogenital system were analyzed by in situ hybridization and CRISPR/Cas9. wt1a was found to be expressed in the glomerulus at 3 dah (days after hatching), earlier than wt1b. wt1a and wt1b were simultaneously expressed in the somatic cells of gonads at 3 dah, while their cell locations were similar, but not identical in adult fish gonads. The wt1a^-/- fish displayed pericardial edema and yolk sac edema at 3 dah and subsequently expanded as general body edema at 6 dah, failed to develop glomerulus and died during 6-10 dah, whereas the wt1b^-/- fish were phenotypically normal. Immunohistochemical analyses revealed that the germ cell marker Vasa was expressed, while somatic cell genes Cyp19a1a, Amh, Gsdf and Dmrt1 were not expressed in the wt1a^-/- gonads at 6 dah. The sex phenotypes of XX and XY in the wt1b^-/- fish were not affected. Real-time PCR revealed that the ovarian cyp19a1a expression was up-regulated in XX wt1b^-/- fish, compared with XX control at 90 dah. Serum estradiol-17β level was also up-regulated in XX wt1b^-/- fish at 90 and 180 dah. The XY wt1b^-/- fish had normal serum estradiol-17β and 11-ketotestosterone levels and remained fertile. These results suggest that Wt1a and Wt1b have different functions in the kidneys and gonads of tilapia.

Organ Culture and Whole Mount Immunofluorescence Staining of Mouse Wolffian Ducts

Tubal morphogenesis is a fundamental requirement for the development of most mammalian organs, including the male reproductive system. The epididymis, an integral part of the male reproductive tract, is responsible for sperm storage, maturation, and transport. The adult epididymis is a highly coiled tube that develops from a simple and straight embryonic precursor known as Wolffian duct (WD). Proper coiling of the epididymis is essential for male fertility, as sperm in the testis are unable to fertilize an oocyte. However, the mechanism responsible for epididymal development and coiling remains unclear, partially due to the lack of whole organ culture and imaging methods. In this study, we describe an in vitro culture system and whole mount immunofluorescence protocol to better visualize the process of WD coiling and development, which may also be applied to study other tubular organs.

Regulation of epithelial function, differentiation, and remodeling in the epididymis

The epididymis is a single convoluted tubule lined by a pseudostratified epithelium. Specialized epididymal epithelial cells, the so-called principal, basal, narrow, and clear cells, establish a unique luminal environment for the maturation and storage of spermatozoa. The epididymis is functionally and structurally divided into several segments and sub-segments that create regionally distinct luminal environments. This organ is immature at birth, and epithelial cells acquire their fully differentiated phenotype during an extended postnatal period, but the factors involved in this complex process remain incompletely characterized. In the adult epididymis, the establishment of an acidic luminal pH and low bicarbonate concentration in the epididymis contributes to preventing premature activation of spermatozoa during their maturation and storage. Clear cells are proton-secreting cells throughout the epididymis, but principal cells have distinct acid/base transport properties, depending on their localization within the epididymis. Basal cells are located in all epididymal segments, but they have a distinct morphology depending on the segment and species examined. How this structural plasticity of basal cells is regulated is discussed here. Also, the role of luminal factors and androgens in the regulation of epithelial cells is reviewed in relation to their respective localization in the proximal versus distal regions of the epididymis. Finally, we describe a novel role for CFTR in tubulogenesis and epithelial cell differentiation.

Epididymis of Viscacha (Lagostomus maximus maximus): A Morphological Comparative Study in Relation to Sexual Maturity

The morphological variations and the androgen receptor (AR) expression were studied in viscacha epididymis in relation to sexual maturity. The animals were divided into immature, pre-pubertal and adult, according to their corporal weight and testicular histology. The epididymides were studied by light microscopy, immunohistochemistry for AR and morphometric analysis. In pre-pubertal and adult animals, four well-differentiated segments (initial, caput, corpus and cauda) were observed, while in immature animals, three segments were identified (initial-caput segment, corpus and cauda). In each segment, the structural parameters and the relative cell distribution were different between the groups. The serum testosterone levels of pre-pubertal and adults showed a very significant increase related to sexual maturity. The AR expression in epithelial and fibromuscular stromal cells was different between the groups. In conclusion, the present work demonstrates that the morphological characteristics of the viscacha epididymis vary while sexual maturity is reached, the development of initial and caput is subsequent to corpus and cauda development and the androgens might play an important role during this process.

Mathematical study on robust tissue pattern formation in growing epididymal tubule

Tissue pattern formation during development is a reproducible morphogenetic process organized by a series of kinetic cellular activities, leading to the building of functional and stable organs. Recent studies focusing on mechanical aspects have revealed physical mechanisms on how the cellular activities contribute to the formation of reproducible tissue patterns; however, the understanding for what factors achieve the reproducibility of such patterning and how it occurs is far from complete. Here, I focus on a tube pattern formation during murine epididymal development, and show that two factors influencing physical design for the patterning, the proliferative zone within the tubule and the viscosity of tissues surrounding to the tubule, control the reproducibility of epididymal tubule pattern, using a mathematical model based on experimental data. Extensive numerical simulation of the simple mathematical model revealed that a spatially localized proliferative zone within the tubule, observed in experiments, results in more reproducible tubule pattern. Moreover, I found that the viscosity of tissues surrounding to the tubule imposes a trade-off regarding pattern reproducibility and spatial accuracy relating to the region where the tubule pattern is formed. This indicates an existence of optimality in material properties of tissues for the robust patterning of epididymal tubule. The results obtained by numerical analysis based on experimental observations provide a general insight on how physical design realizes robust tissue pattern formation.

Is the Epididymis a Series of Organs Placed Side By Side?

The mammalian epididymis is more than a highly convoluted tube divided into four regions: initial segment, caput, corpus and cauda. It is a highly segmented structure with each segment expressing its own and overlapping genes, proteins, and signal transduction pathways. Therefore, the epididymis may be viewed as a series of organs placed side by side. In this review we discuss the contributions of septa that divide the epididymis into segments and present hypotheses as to the mechanism by which septa form. The mechanisms of Wolffian duct segmentation are likened to the mechanisms of segmentation of the renal nephron and somites. The renal nephron may provide valuable clues as to how the Wolffian duct is patterned during development, whereas somitogenesis may provide clues as to the timing of the development of each segment. Emphasis is also placed upon how segments are differentially regulated, in support of the idea that the epididymis can be considered a series of multiple organs placed side by side. One region in particular, the initial segment, which consists of 2 or 4 segments in mice and rats, respectively, is unique with respect to its regulation and vascularity compared to other segments; loss of development of these segments leads to male infertility. Different ways of thinking about how the epididymis functions may provide new directions and ideas as to how sperm maturation takes place.

The impact of dasatinib on pregnancy outcomes

Prolonged survival in patients with chronic myeloid leukemia treated with BCR-ABL1-targeted tyrosine kinase inhibitors allows consideration of parenthood for patients on chronic therapy, but there are limited data about the effects of dasatinib on pregnancy. Pregnancy-related outcomes in dasatinib-treated patients or their partners reported to Bristol-Myers Squibb from clinical trials or healthcare providers through December 2013 were reviewed. Outcomes were available in 46/78 dasatinib-treated women (59%) and 33/69 partners of dasatinib-treated men (48%). Fifteen women (33%) delivered a normal infant; 18 (39%) and 8 (17%) had an elective or spontaneous abortion; and 5 (11%) had an abnormal pregnancy. There were 7 reports of fetal/infant abnormalities (encephalocele, renal tract abnormalities, and hydrops fetalis). Thirty of 33 (91%) infants fathered by dasatinib-treated men were reported normal at birth. Also, animal studies evaluated the impact of dasatinib on fertility, embryo-fetal toxicity, and development, suggesting that dasatinib may be a selective developmental toxicant. The outcomes of most pregnancies conceived by men treated with dasatinib were normal, but due to the small number of cases, further monitoring is required. Significant effects on pregnancy outcomes in women treated with dasatinib were found, supporting current recommendations that women avoid becoming pregnant during dasatinib treatment and be informed of fetal risks.