Morphology of mouse seminiferous tubules

Consequences of Exposure to Hypobaric Hypoxia Associated with High Altitude on Spermatogenesis and Seminal Parameters: A Literature Review

Preclinical research has provided compelling evidence indicating that exposure to hypobaric hypoxia (HH) results in a deterioration of spermatogenesis. This adverse effect extends to the underlying molecular mechanisms, progressively leading to impairments in the seminiferous epithelium and germ cells and alterations in semen parameters. Indeed, several studies have demonstrated that animals exposed to HH, whether in natural high-altitude environments or under simulated hypoxic conditions, exhibit damage to the self-renewal and differentiation of spermatogenesis, an increase in germline cell apoptosis, and structural alterations in the seminiferous tubules. One of the primary mechanisms associated with the inhibition of differentiation and an increase in apoptosis among germ cells is an elevated level of oxidative stress, which has been closely associated with HH exposure. Human studies have shown that individuals exposed to HH, such as mountaineers and alpinists, exhibit decreased sperm count, reduced motility, diminished viability, and increased sperm with abnormal morphology in their semen. This evidence strongly suggests that exposure to HH may be considered a significant risk factor that could elevate the prevalence of male infertility. This literature review aims to provide a comprehensive description and propose potential mechanisms that could elucidate the infertility processes induced by HH. By doing so, it contributes to expanding our understanding of the challenges posed by extreme environments on human physiology, opening new avenues for research in this field.

Expression of the umami taste receptor T1R1/T1R3 in porcine testis of: Function in regulating testosterone synthesis and autophagy in Leydig cells

Testosterone is a vital male hormone responsible for male sexual characteristics. The taste receptor family 1 subunit 3 (T1R3) regulates testosterone synthesis and autophagy in non-taste cells, and the links with the taste receptor family 1 subunit 1 (T1R1) for umami perception. However, little is known about these mechanisms. Thus, we aimed to determine the relationship between the umami taste receptor (T1R1/T1R3) and testosterone synthesis or autophagy in testicular Leydig cells of the Xiang pig. There was a certain proportion of spermatogenic tubular dysplasia in the Xiang pig at puberty, in which autophagy was enhanced, and the testosterone level was increased with a weak expression of T1R3. Silenced T1R3 decreased testosterone level and intracellular cyclic adenosine monophosphate (cAMP) content and inhibited the messenger RNA (mRNA) expression levels of testosterone synthesis enzyme genes [steroidogenic acute regulatory protein (StAR), hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 1 (3β-HSD1), cytochrome P450 family 17 subfamily A member 1 (CYP17A1) and hydroxysteroid 17-beta dehydrogenase 3 (17β-HSD3)]. In addition, T1R3 increased the number of acidic autophagy bubbles and upregulated the expression levels of autophagy markers [Microtubule-associated protein 1 A/1B-light chain 3 (LC3) and Beclin-1] in testicular Leydig cells of the Xiang pig. Using an umami tasting agonist (10 mM L-glutamate for 6 h), the activation of T1R1/T1R3 enhanced the testosterone synthesis ability by increasing the intracellular cAMP level and upregulated the expression levels of StAR, 3β-HSD1, CYP17A1 and 17β-HSD3 in Leydig cells. Furthermore, the number of acidic autophagy bubbles decreased in the T1R1/T1R3-activated group with the downregulation of the expression levels of the autophagy markers, including LC3 and Beclin-1. These data suggest that the function of T1R1/T1R3 expressed in testicular Leydig cells of the Xiang pig is related to testosterone synthesis and autophagy.

Three-dimensional analysis of junctions between efferent and epididymal ducts in the human caput epididymis

BACKGROUND

Due to the scarcity of studies using human tissues, the limited information is currently available on the gross structure of the caput epididymis in humans, at which efferent ducts connect to the epididymal duct.

OBJECTIVE

The present study investigated the three-dimensional structures of efferent and caput epididymal ducts in humans, with a focus on junctions between the former and the latter.

MATERIALS AND METHODS

We examined three sets of human efferent and caput epididymal ducts in specimens obtained from prostatic carcinoma patients. They were reconstructed from serial paraffin sections using a segmentation model created by a deep learning protocol and high-performance three-dimensional reconstruction software.

RESULTS

Serial sections and three-dimensional images of human efferent and caput epididymal ducts were combined to obtain the detailed anatomical information. When a single efferent duct was defined as a duct connecting to both the extra-testicular rete testis and epididymal duct, there were 14.7 efferent ducts with a total length of 3.0 m per specimen on average. The cranial portion of the efferent ducts joined to a single duct and terminated at the end of the epididymal duct, whereas other efferent ducts terminated independently on the side of the epididymal duct. These two types of junctions between the efferent and epididymal ducts differed in the patterns of the epithelial-type switch. The epididymal duct consisted of multiple segments, which were separated by a minimal amount of connective tissue septa or even without them. Efferent ducts occupied most of the volume of the caput epididymis.

DISCUSSION AND CONCLUSIONS

By utilizing deep learning, we reconstructed human efferent and caput epididymal ducts and revealed their precise three-dimensional structures, which differed from those of rodents in several aspects. The present results may be useful for analyzing anatomical abnormalities related to some types of male infertility.

Three-dimensional morphometry of the testis in dog using design-unbiased stereology

Testis is considered the main organ of the male reproductive system. Dogs are used as a suitable experimental model of testicular diseases in humans. From the veterinary aspect, several disorders have been reported to affect the testis in dogs. Thus, the objective of the present study was to investigate the morphometrical features of the dog testis using design-based stereology. The testes of six male dogs were used. Isotropic, uniform random sections were obtained and processed for light microscopy. Testicular total volume and the fractional volume of the seminiferous tubules, interstitial tissue and germinal epithelium were measured using the Cavalieri's estimator and the point counting system. Germinal epithelial surface area was estimated using test lines, and total length of seminiferous tubules was analysed using the counting frames. The total volume of testis was calculated 13.64 ± 1.94 cm3 . The relative volume fractions of the seminiferous tubules, interstitial tissue and germinal layer expressed as a percentage of total testicular volume were found to be 75.87 ± 6.11%, 23.68 ± 5.15% and 64.15 ± 4.82%, respectively. The surface area of the germinal layer was 915.25 ± 150.48 cm2 . The thickness of germinal layer was estimated to be 96.18 ± 10.72 μm. The total length of seminiferous tubules measured 290.8 ± 35.86 m. No statistical difference in investigated parameters was found between the left and right testes (p > 0.05). Our data might contribute to the male reproductive knowledge, help develop experimental studies in this field and possibly lead to advancement in the diagnosis and treatment of testicular diseases in the dog.

Expression of Phospholipase D Family Member 6 in Bovine Testes and Its Molecular Characteristics

Spermatogonial stem cells (SSCs) are the only primitive spermatogonial cells in males that can naturally transmit genetic information to their offspring and replicate throughout their lives. Phospholipase D family member 6 (PLD6) has recently been found to be a surface marker for SSCs in mice and boars; however, it has not been validated in cattle. The results of reversed transcription-polymerase chain reaction (RT-PCR) and quantitative real-time PCR (qRT-PCR) found that the relative expression of the PLD6 gene in the testicular tissues of two-year-old Simmental calves was significantly higher than that of six-month-old calves. Immunofluorescent staining further verified the expression of PLD6 protein in bovine spermatogenic cells like germ cell marker DEAD box helicase 4 (DDX4, also known as VASA). Based on multiple bioinformatic databases, PLD6 is a conservative protein which has high homology with mouse Q5SWZ9 protein. It is closely involved in the normal functioning of the reproductive system. Molecular dynamics simulation analyzed the binding of PLD6 as a phospholipase to cardiolipin (CL), and the PLD6-CL complex showed high stability. The protein interaction network analysis showed that there is a significant relationship between PLD6 and piwi-interacting RNA (piRNA) binding protein. PLD6 acts as an endonuclease and participates in piRNA production. In addition, PLD6 in bovine and mouse testes has a similar expression pattern with the spermatogonium-related genes VASA and piwi like RNA-mediated gene silencing 2 (PIWIL2). In conclusion, these analyses imply that PLD6 has a relatively high expression in bovine testes and could be used as a biomarker for spermatogenic cells including SSCs.

Sevoflurane inhibited reproductive function in male mice by reducing oxidative phosphorylation through inducing iron deficiency

Sevoflurane (Sev) is one of the commonly used inhalation anesthetic chemicals in clinics. It has great impact on spermatogenesis and fertilization in male animals. The underlying mechanism remains largely unexplored. Based on our previous research, we hypothesized that Sev induced iron metabolism disturbance in the testis and epididymis and inhibited the spermatogenesis. In this study, two-month-old C57BL/6 male mice were treated with 3% Sev for 6 h, and their fertility (including sperm concentration, sperm mobility, and the number of offspring) was evaluated. Mice testis, epididymis, and sperm were harvested and subjected to Western blot analysis and immunofluorescence analysis. Iron levels were reflected by the gene expression of iron metabolism-related proteins (including ferritin, TfR1, and FpN1) and ICP-MS and Perl's iron staining. Electron transport and oxidative phosphorylation levels were measured by Oxygraph-2k and ATP contents. The activity of ribonucleotide reductase was evaluated by assay kit. DNA synthesis status in testis and/or epididymis was marked with BrdU. Cell proliferation was evaluated by double immunofluorescence staining of specific protein marker expression. Our results revealed that the mice exposed to Sev showed damaged testicular and epididymis structure and significantly reduced the sperm concentration, sperm motility, and fertility. Sev decreases the iron levels through down-regulating the expression of H-ferritin, L-ferritin, and FpN1, and up-regulating the expression of TfR1 in the testis and epididymis. Iron levels also significantly reduced in germ cells which decrease the number of germ cells, including sperm, Sertoli cells, and primary spermatocyte. Iron deficiency not only decreases electron transport, oxidative phosphorylation level, and ATP production but also suppresses the activity of ribonucleotide reductase and the expression of Ki67, DDX4, GATA1, and SCP3, indicating that Sev affects the spermatogenesis and development. Meanwhile, Sev impaired the blood-testis barrier by decreasing the ZO1 expression in the testis and epididymis. The damage effect induced by Sev can be significantly ameliorated by iron supplementation. In conclusion, our study illustrates a new mechanism by which Sev inhibits spermatogenesis and fertility through an oxidative phosphorylation pathway due to iron deficiency of epididymis and testis or sperm. Furthermore, the damaging effects could be ameliorated by iron supplementation.

Protective effects of human amniotic membrane derived mesenchymal stem cells (hAMSCs) secreted factors on mouse spermatogenesis and sperm chromatin condensation following unilateral testicular torsion

Testicular torsion is considered a urological disorder that requires immediate detorsion surgery. Ischemia/reperfusion (I/R) injury after testicular torsion detorsion causes of drastic impairment of spermatogenesis and infertility. Cell-free-based approaches seem to be a promising strategy to prevent I/R injury, they have more stable biological properties, and they contain paracrine factors of mesenchymal stem cells. The purpose of this study was to evaluate the protective effects of human amniotic membrane derived mesenchymal stem cells (hAMSCs) secreted factors on mouse sperm chromatin condensation and spermatogenesis improvement after I/R injury. hAMSCs were isolated and characterized by RT- PCR and flow cytometry, preparation of hAMSCs secreted factors was performed. Forty male mice were randomly divided into 4 groups: sham-operated, torsion detorsion, torsion detorsion+ intratesticular injection of DMEM/F-12, and torsion detorsion+ intratesticular injection of hAMSCs secreted factors. After one cycle of spermatogenesis, the mean number of germ cells, Sertoli, Leydig, myoid as well as tubular parameters, Johnson score, and spermatogenesis indexes were evaluated by H& E and PAS stainings. Sperm chromatin condensation and relative expression of c-kit and prm 1 genes were assessed by aniline blue staining and real-time PCR, respectively. The mean number of spermatogenic cells, Leydig, Myoid, Sertoli, spermatogenesis parameters, Johnson score, as well as germinal epithelial height and diameters of seminiferous tubules decreased significantly after I/R injury. The thickness of basement membrane and percentage of sperm with excessive histone significantly increased, while the relative expression of c-kit and prm 1 significantly decreased in torsion detorsion group (p<0.001). hAMSCs secreted factors remarkably restored normal sperm chromatin condensation, spermatogenesis parameters and histomorphometric organization of seminiferous tubules via intratesticular injection (p<0.001). Thus, hAMSCs secreted factors may potentially salvage torsion-detorsion-induced infertility.

SATINN: an automated neural network-based classification of testicular sections allows for high-throughput histopathology of mouse mutants

MOTIVATION

The mammalian testis is a complex organ with a cellular composition that changes smoothly and cyclically in normal adults. While testis histology is already an invaluable tool for identifying and describing developmental differences in evolution and disease, methods for standardized, digital image analysis of testis are needed to expand the utility of this approach.

RESULTS

We developed SATINN (Software for Analysis of Testis Images with Neural Networks), a multi-level framework for automated analysis of multiplexed immunofluorescence images from mouse testis. This approach uses residual learning to train convolutional neural networks (CNNs) to classify nuclei from seminiferous tubules into seven distinct cell types with an accuracy of 81.7%. These cell classifications are then used in a second-level tubule CNN, which places seminiferous tubules into one of 12 distinct tubule stages with 57.3% direct accuracy and 94.9% within ±1 stage. We further describe numerous cell- and tubule-level statistics that can be derived from wild-type testis. Finally, we demonstrate how the classifiers and derived statistics can be used to rapidly and precisely describe pathology by applying our methods to image data from two mutant mouse lines. Our results demonstrate the feasibility and potential of using computer-assisted analysis for testis histology, an area poised to evolve rapidly on the back of emerging, spatially resolved genomic and proteomic technologies.

AVAILABILITY AND IMPLEMENTATION

The source code to reproduce the results described here and a SATINN standalone application with graphic-user interface are available from http://github.com/conradlab/SATINN.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

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.

NANOS3 suppresses premature spermatogonial differentiation to expand progenitors and fine-tunes spermatogenesis in mice

In the mouse testis, sperm originate from spermatogonial stem cells (SSCs). SSCs give rise to spermatogonial progenitors, which expand their population until entering the differentiation process that is precisely regulated by a fixed time-scaled program called the seminiferous cycle. Although this expansion process of progenitors is highly important, its regulatory mechanisms remain unclear. NANOS3 is an RNA-binding protein expressed in the progenitor population. We demonstrated that the conditional deletion of Nanos3 at a later embryonic stage results in the reduction of spermatogonial progenitors in the postnatal testis. This reduction was associated with the premature differentiation of progenitors. Furthermore, this premature differentiation caused seminiferous stage disagreement between adjacent spermatogenic cells, which influenced spermatogenic epithelial cycles, leading to disruption of the later differentiation pathway. Our study suggests that NANOS3 plays an important role in timing progenitor expansion to adjust to the proper differentiation timing by blocking the retinoic acid (RA) signaling pathway.

High fat diet-induced obesity prolongs critical stages of the spermatogenic cycle in a Ldlr-/-.Leiden mouse model

Obesity can disturb spermatogenesis and subsequently affect male fertility and reproduction. In our study, we aim to elucidate at which cellular level of adult spermatogenesis the detrimental effects of obesity manifest. We induced high fat diet (HFD) obesity in low-density lipoprotein receptor knock-out Leiden (Ldlr^−/−.Leiden) mice, and studied the morphological structure of the testes and histologically examined the proportion of Sertoli cells, spermatocytes and spermatids in the seminiferous tubules. We examined sperm DNA damage and chromatin condensation and measured plasma levels of leptin, testosterone, cholesterol and triglycerides. HFD-induced obesity caused high plasma leptin and abnormal testosterone levels and induced an aberrant intra-tubular organisation (ITO) which is associated with an altered spermatids/spermatocytes ratio (2:1 instead of 3:1). Mice fed a HFD had a higher level of tubules in stages VII + VIII in the spermatogenic cycle. The stages VII + VII indicate crucial processes in spermatogenic development like initiation of meiosis, initiation of spermatid elongation, and release of fully matured spermatids. In conclusion, HFD-induced obese Ldlr^−/−.Leiden mice develop an aberrant ITO and alterations in the spermatogenic cycle in crucial stages (stages VII and VII). Thereby, our findings stress the importance of lifestyle guidelines in infertility treatments.

Three-dimensional morphological analysis of spermatogenesis in aged mouse testes

Spermatogenesis, which is a continuous process from undifferentiated spermatogonia to spermatozoa in the seminiferous tubules, declines with age. To investigate changes in spermatogenesis with aging, we reconstructed the seminiferous tubules of 12 mice aged 12 to 30 months from serial sections and examined age-related and region-specific alterations in the seminiferous epithelium and spermatogenic waves in three dimensions. The basic structure of the seminiferous tubules, including the numbers of tubules, terminating points, branching points, and total tubule length, did not change with age. Age-related alterations in spermatogenesis, primarily assessed by the formation of vacuoles in Sertoli cells, were detected in the seminiferous tubules at 12 months. The proportion of altered tubule segments with impaired spermatogenesis further increased by 24 months, but remained unchanged thereafter. Altered tubule segments were preferentially distributed in tubule areas close to the rete testis and those in the center of the testis. Spermatogenic waves became shorter in length with age. These results provide a basis for examining the decline of spermatogenesis not only with aging, but also in male infertility.

Three-dimensional reconstruction of testis cords/seminiferous tubules

BACKGROUND

Due to the development of novel equipment for the acquisition of two-dimensional serial images and software capable of displaying three-dimensional (3D) images from serial images, the accurate 3D reconstruction of organs and tissues has become possible.

METHODS

Based on published studies, this review summarizes techniques for the 3D reconstruction of the testis cords/seminiferous tubules, with special reference to our method using serial paraffin sections and 3D visualization software.

MAIN FINDINGS

The testes of mice, rats, and hamsters of various ages were 3D reconstructed and species and age differences in the structures of the testis cords/seminiferous tubules were analyzed. Our method is advantageous because conventional paraffin-embedded normal and pathological specimens may be utilized for the 3D analysis without the need for complicated and expensive equipment.

CONCLUSION

By further decreasing the time and labor required for the procedure and adding information on molecular localization, the technique for 3D reconstruction will contribute to the elucidation of not only the structures, but also the functions of various organs, including the testis.

Role of laminin and collagen chains in human spermatogenesis - Insights from studies in rodents and scRNA-Seq transcriptome profiling

Studies have demonstrated that biologically active fragments are generated from the basement membrane and the Sertoli cell-spermatid adhesion site known as apical ectoplasmic specialization (apical ES, a testis-specific actin-based anchoring junction) in the rat testis. These bioactive fragments or peptides are produced locally across the seminiferous epithelium through proteolytic cleavage of constituent proteins at the basement membrane and the apical ES. Studies have shown that they are being used to modulate and coordinate cellular functions across the seminiferous epithelium during different stages of the epithelial cycle of spermatogenesis. In this review, we briefly summarize recent findings based on studies using rat testes as a study model regarding the role of these bioactive peptides that serve as a local regulatory network to support spermatogenesis. We also used scRNA-Seq transcriptome datasets in the public domain for OA (obstructive azoospermia) and NAO (non-obstructive azoospermia) human testes versus testes from normal men for analysis in this review. It was shown that there are differential expression of different collagen chains and laminin chains in these testes, suggesting the possibility of a similar local regulatory network in the human testis to support spermatogenesis, and the possible disruption of such network in men is associated with OA and/or NOA.

Three-dimensional structure of testis cords in mice and rats

BACKGROUND

Testis cord elongation and coiling, which occur in the final stage of testis formation, have been attributed to Sertoli cell proliferation; however, the underlying mechanisms remain unclear.

OBJECTIVE

The aim of the present study was to clarify the precise three-dimensional structure of testis cords in the final stage of testis formation in mice and rats.

MATERIALS AND METHODS

We reconstructed whole testis cords in the final stage of testis formation in mice (on embryonic days 15.5 and 18.5) and rats (on embryonic days 16.5 and 19.5) using serial paraffin sections and high-performance three-dimensional reconstruction software.

RESULTS

Detailed morphometric parameters were calculated for three-dimensionally reconstructed testis cords in six mouse and rat testes each. The mean numbers of testis cords in mice and rats were 12.7 and 27.8, respectively. The mean number of branching points per testis cord was 1.52 in mice, whereas it was only 0.30 in rats. In contrast, the mean ratio of the inner cords, that is, cords not in contact with the tunica albuginea, was 23.0% in rats, whereas it was only 6.5% in mice. In both species, the cords on the cranial side coiled more strongly than those on the caudal side, consistent with the greater expansion of the testis volume on the caudal side. All cords formed right-handed helices from the rete testis side.

DISCUSSION AND CONCLUSIONS

The present results suggest that testis cords undergo anastomosis at a higher frequency in mice than in rats and that the coiling of testis cords proceeds from the cranial to caudal side of the testis in both species.

Step by Step about Germ Cells Development in Canine

Simple Summary

The progression of germ cells is a remarkable event that allows biological discovery in the differ-entiation process during in vivo and in vitro development. This is crucial for understanding one toward making oogenesis and spermatogenesis. Companion animals, such as canine, could offer new animal models for experimental and clinical testing for translation to human models. In this review, we describe the latest and more relevant findings on germ cell development. In addition, we showed the methods available for obtaining germ cells in vitro and the characterization of pri-mordial germ cells and spermatogonial stem cells. However, it is necessary to further conduct basic research in canine to clarify the beginning of germ cell development.

Abstract

Primordial germ cells (PGCs) have been described as precursors of gametes and provide a connection within generations, passing on the genome to the next generation. Failures in the formation of gametes/germ cells can compromise the maintenance and conservation of species. Most of the studies with PGCs have been carried out in mice, but this species is not always the best study model when transposing this knowledge to humans. Domestic animals, such as canines (canine), have become a valuable translational research model for stem cells and therapy. Furthermore, the study of canine germ cells opens new avenues for veterinary reproduction. In this review, the objective is to provide a comprehensive overview of the current knowledge on canine germ cells. The aspects of canine development and germ cells have been discussed since the origin, specifications, and development of spermatogonial canine were first discussed. Additionally, we discussed and explored some in vitro aspects of canine reproduction with germ cells, such as embryonic germ cells and spermatogonial stem cells.

Three-dimensional structure of seminiferous tubules in the Syrian hamster

The hamster is useful for the study of male reproductive biology. However, unlike in the mouse and rat, the gross structure of seminiferous tubules in the hamster is largely unknown. The aim of the present study was to clarify the precise 3-dimensional (3D) structure of seminiferous tubules in hamsters. We reconstructed all seminiferous tubules in 3 and 1 testes from 0-day (P0) and 10-week (adult) Syrian hamsters, respectively, using serial paraffin sections and high-performance 3D reconstruction software. In P0 hamsters, the average numbers of seminiferous tubules, terminating points, branching points, and blind ends per testis were 9.0, 89.7, 93.0, and 0.7, respectively. There were two types of tubules: shorter and dominant ones. The dominant tubules, 2-4 in number per testis and accounting for 86% of the total tubule length, had many terminating and branching points and appeared to be derived from the anastomosis of many shorter tubules. In an adult hamster, there were 11 seminiferous tubules with a total length of 22 m, 98 terminating points, 88 branching points, and 2 blind ends per testis. Three of the 11 tubules were dominant ones, accounting for 83% of the total length, and occupied the testis from the surface over the circumference to the center, while the others were short and occupied only one side of the testis. The amplitude and direction of the curves of tubules were random, and there were no funnel-shaped networks of tubules present, in contrast to the mouse testis. The present study revealed the 3D structure of seminiferous tubules in developing and adult Syrian hamsters, which is different from that in mice and rats.

Three-Dimensional Analysis of Busulfan-Induced Spermatogenesis Disorder in Mice

We examined if the distribution of impaired or normal spermatogenesis differs along the length of seminiferous tubules in disorders of spermatogenesis. For this purpose, three-dimensional (3D) reconstruction of seminiferous tubules was performed in mice with experimental spermatogenesis disorder induced by intraperitoneal injection of busulfan, and the areas of impaired and normal spermatogenesis were analyzed microscopically. The volume of the testis and length of seminiferous tubules decreased, and the proportion of tubule areas with impaired spermatogenesis increased depending on the dose of busulfan. With the highest dose of busulfan, although the proportion of impaired spermatogenesis was similar among individual seminiferous tubules, it was slightly but significantly higher in shorter tubules and in tubule areas near branching points. The tubule areas with impaired and normal spermatogenesis consisted of many segments of varying lengths. With increasing doses of busulfan, the markedly impaired segments increased in length without changing in number, whereas normal segments, although reduced in number and length, remained even with the highest dose of busulfan. Individual remaining normal segments consisted of several different stages, among which stage I and XII were found at higher frequencies, and stage VI at a lower frequency than expected in normal seminiferous tubules. We also examined if the distribution of impaired or normal spermatogenesis differs among different 3D positions in the testis without considering the course of seminiferous tubules. Although the proportions of impaired spermatogenesis with the minimum dose of busulfan and normal spermatogenesis with the highest dose of busulfan greatly varied by location within a single testis, there were no 3D positions with these specific proportions common to different testes, suggesting that the factors influencing the severity of busulfan-induced spermatogenesis disorder are not fixed in location among individual mice.

Widespread loss of the silencing epigenetic mark H3K9me3 in astrocytes and neurons along with hippocampal-dependent cognitive impairment in C9orf72 BAC transgenic mice

Background

Hexanucleotide repeat expansions of the G₄C₂ motif in a non-coding region of the C9ORF72 gene are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Tissues from C9ALS/FTD patients and from mouse models of ALS show RNA foci, dipeptide-repeat proteins, and notably, widespread alterations in the transcriptome. Epigenetic processes regulate gene expression without changing DNA sequences and therefore could account for the altered transcriptome profiles in C9ALS/FTD; here, we explore whether the critical repressive marks H3K9me2 and H3K9me3 are altered in a recently developed C9ALS/FTD BAC mouse model (C9BAC).

Results

Chromocenters that constitute pericentric constitutive heterochromatin were visualized as DAPI- or Nucblue-dense foci in nuclei. Cultured C9BAC astrocytes exhibited a reduced staining signal for H3K9me3 (but not for H3K9me2) at chromocenters that was accompanied by a marked decline in the global nuclear level of this mark. Similar depletion of H3K9me3 at chromocenters was detected in astrocytes and neurons of the spinal cord, motor cortex, and hippocampus of C9BAC mice. The alterations of H3K9me3 in the hippocampus of C9BAC mice led us to identify previously undetected neuronal loss in CA1, CA3, and dentate gyrus, as well as hippocampal-dependent cognitive deficits.

Conclusions

Our data indicate that a loss of the repressive mark H3K9me3 in astrocytes and neurons in the central nervous system of C9BAC mice represents a signature during neurodegeneration and memory deficit of C9ALS/FTD.

Cycles, waves, and pulses: Retinoic acid and the organization of spermatogenesis

Background

Spermatogenesis in mammals is organized in a manner that maximizes sperm production. The central aspect of this organization is the cycle of the seminiferous epithelium that is characterized by an asynchronous repeating series of germ cell associations. These cell associations are the result of a fixed point of entry into the cycle at regular short time intervals and the longer time required for cells to fully differentiate and exit the cycle.

Objective

This review will examine the current information on the action and metabolism of retinoic acid in the testis, the interaction of retinoic acid (RA) with the cycle and the spermatogenic wave, and the mechanisms that can lead to synchronous spermatogenesis. Finally, the unique applications of synchronous spermatogenesis to the study of the cycle and the mass isolation of specific germ cell populations are described.

Materials and methods

Retinoic acid metabolism and spermatogonial differentiation have been examined by gene deletions, immunocytochemistry, chemical inhibitors, and mass spectrometry.

Results, discussion, and conclusion

Both the Sertoli cells and the germ cells have the capacity to synthesize retinoic acid from retinol and in the mouse the entry into the cycle of the seminiferous epithelium, and the subsequent conversion of undifferentiated spermatogonia into differentiating spermatogonia is governed by a peak of RA synthesis occurring at stages VIII‐IX of the cycle. Normal asynchronous spermatogenesis can be modified by altering RA levels, and as a result the entire testis will consist of a few closely related stages of the cycle.

Crosstalk between Sertoli and Germ Cells in Male Fertility

Spermatogenesis is supported by intricate crosstalk between Sertoli cells and germ cells including spermatogonia, spermatocytes, haploid spermatids, and spermatozoa, which takes place in the epithelium of seminiferous tubules. Sertoli cells, also known as 'mother' or 'nurse' cells, provide nutrients, paracrine factors, cytokines, and other biomolecules to support germ cell development. Sertoli cells facilitate the generation of several biologically active peptides, which include F5-, noncollagenous 1 (NC1)-, and laminin globular (LG)3/4/5-peptide, to modulate cellular events across the epithelium. Here, we critically evaluate the involvement of these peptides in facilitating crosstalk between Sertoli and germ cells to support spermatogenesis and thus fertility. Modulating or mimicking the activity of F5-, NC1-, and LG3/4/5-peptide could be used to enhance the transport across the blood-testis barrier (BTB) of contraceptive drugs or to treat male infertility.

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.