Cryptorchidism and testicular cancer in the dog: unresolved questions and challenges in translating insights from human studies†

Cryptorchidism, the failure of one or both testes to descend into the scrotum, and testicular cancer show a strong correlation in both dogs and humans. Yet, long-standing medical debates persist about whether the location of undescended testes directly causes testicular cancer in humans or if both conditions stem from a common origin. Although testicular cancer is a prevalent disease in dogs, even less is known about its cause and correlation with testicular descent in this species. This review investigates the relation between these two disorders in dogs, drawing insights from human studies, and examines key biomarkers identified thus far. In addition, it explores potential causal links, including the impact of temperature on maturing testicular cells and a potential shared genetic origin. Notably, this literature review reveals significant differences between men and dogs in reproductive development, histological and molecular features of testicular tumors, and the prevalence of specific tumor types, such as Sertoli cell tumors in cryptorchid dogs and germ cell tumors in humans. These disparities caution against using dogs as models for human testicular cancer research and underscore the limitations when drawing comparisons between species. The paper concludes by suggesting specific research initiatives to enhance our understanding of the complex interplay between cryptorchidism and testicular cancer in dogs.

Fluorene-9-bisphenol impaired male fertility through disrupting the testicular function and local microenvironment

Past studies have observed that BHPF induces multi-organ toxicity, however, whether it induces damage to male reproductive system and the specific mechanism remains unclear. In the present study, male mice were given 0, 2, 10 or 50 mg/kg/day of BHPF by gavage for 35 days to observe its effect on reproductive organ and sperm quality. The results indicated that BHPF decreased sperm count and sperm motility in a dose-dependent manner. Besides, our results demonstrated that BHPF triggered the proliferation inhibition and cell death of germ cells in vivo and in vitro. Also, BHPF reduced the expression of function markers for germ cells, Sertoli cells, and Leydig cells, indicating its damage to function of testis cells. Simultaneously, testicular microenvironment was found to be altered by BHPF, as presented with declined testosterone level and decreased expression of local microenvironment regulators. Overall, our findings indicated the detrimental effects of BHPF on male reproductive function in mice, suggesting testicular function and local microenvironment disturbance as mechanism underlying testicular damage.

Differential roles of cyclooxygenase enzymes in the regulation of murine juvenile undifferentiated spermatogonia

BACKGROUND

Acetaminophen and ibuprofen are widely administered to babies due to their presumed safety as over-the-counter drugs. However, no reports exist on the effects of cyclooxygenase inhibitors on undifferentiated spermatogonia and spermatogonial stem cells. Infancy represents a critical period for spermatogonial stem cell formation and disrupting spermatogonial stem cells or their precursors may be associated with infertility and testicular cancer formation.

OBJECTIVES

The goal of this study was to examine the molecular and functional impact of cyclooxygenase inhibition and silencing on early steps of undifferentiated spermatogonia (u spg) and spermatogonial stem cell development, to assess the potential reproductive risk of pharmaceutical cyclooxygenase inhibitors.

METHODS

The effects of cyclooxygenase inhibition were assessed using the mouse C18-4 undifferentiated juvenile spermatogonial cell line model, previously shown to include cells with spermatogonial stem cell features, by measuring prostaglandins, cell proliferation, and differentiation, using cyclooxygenase 1- and cyclooxygenase 2-selective inhibitors NS398, celecoxib, and FR122047, acetaminophen, and ibuprofen. Cyclooxygenase 1 gene silencing was achieved using a stable short-hairpin RNA approach and clone selection, then assessing gene and protein expression in RNA sequencing, quantitative real-time polymerase chain reaction, and immunofluorescence studies.

RESULTS

Cyclooxygenase 2 inhibitors NS398 and celecoxib, as well as acetaminophen, but not ibuprofen, dose-dependently decreased retinoic acid-induced expression of the spg differentiation gene Stra8, while NS398 decreased the spg differentiation marker Kit, suggesting that cyclooxygenase 2 is positively associated with spg differentiation. In contrast, short-hairpin RNA-based cyclooxygenase 1 silencing in C18-4 cells altered cellular morphology and upregulated Stra8 and Kit, implying that cyclooxygenase 1 prevented spg differentiation. Furthermore, RNA sequencing analysis of cyclooxygenase 1 knockdown cells indicated the activation of several signaling pathways including the TGFb, Wnt, and Notch pathways, compared to control C18-4 cells. Notch pathway genes were upregulated by selective cyclooxygenase inhibitors, acetaminophen and ibuprofen.

CONCLUSION

We report that cyclooxygenase 1 and 2 differentially regulate undifferentiated spermatogonia/spermatogonial stem cell differentiation. Cyclooxygenases regulate Notch3 expression, with the Notch pathway targeted by PGD2. These data suggest an interaction between the eicosanoid and Notch signaling pathways that may be critical for the development of spermatogonial stem cells and subsequent spermatogenesis, cautioning about using cyclooxygenase inhibitors in infants.

hnRNPU is required for spermatogonial stem cell pool establishment in mice

The continuous regeneration of spermatogonial stem cells (SSCs) underpins spermatogenesis and lifelong male fertility, but the developmental origins of the SSC pool remain unclear. Here, we document that hnRNPU is essential for establishing the SSC pool. In male mice, conditional loss of hnRNPU in prospermatogonia (ProSG) arrests spermatogenesis and results in sterility. hnRNPU-deficient ProSG fails to differentiate and migrate to the basement membrane to establish SSC pool in infancy. Moreover, hnRNPU deletion leads to the accumulation of ProSG and disrupts the process of T1-ProSG to T2-ProSG transition. Single-cell transcriptional analyses reveal that germ cells are in a mitotically quiescent state and lose their unique identity upon hnRNPU depletion. We further show that hnRNPU could bind to Vrk1, Slx4, and Dazl transcripts that have been identified to suffer aberrant alternative splicing in hnRNPU-deficient testes. These observations offer important insights into SSC pool establishment and may have translational implications for male fertility.

Gene expression programs in mammalian spermatogenesis

Mammalian spermatogenesis, probably the most complex of all cellular developmental processes, is an ideal model both for studying the specific mechanism of gametogenesis and for understanding the basic rules governing all developmental processes, as it entails both cell type-specific and housekeeping molecular processes. Spermatogenesis can be viewed as a mission with many tasks to accomplish, and its success is genetically programmed and ensured by the collaboration of a large number of genes. Here, I present an overview of mammalian spermatogenesis and the mechanisms underlying each step in the process, covering the cellular and molecular activities that occur at each developmental stage and emphasizing their gene regulation in light of recent studies.

Disruption of gonocyte development following neonatal exposure to di (2-ethylhexyl) phthalate

Pre- and/or post-natal administrations of di(2-ethylhexyl) phthalate (DEHP) in experimental animals cause alterations in the spermatogenesis. However, the mechanism by which DEHP affects fertility is unknown and could be through alterations in the survival and differentiation of the gonocytes. The aim of the present study was to evaluate the effect of a single administration of DEHP in newborn mice on gonocytic proliferation, differentiation and survival and its long-term effects on seminiferous epithelium and sperm quality. BALB/c mice distributed into Control and DEHP groups were used. Each animal in the DEHP group was given a single dose of 500 mg/Kg at birth. The animals were analyzed at 1, 2, 4, 6, 8, 10 and 70 days postpartum (dpp). Testicular tissues were processed for morphological analysis to determine the different types of gonocytes, differentiation index, seminiferous epithelial alterations, and immunoreactivity to Stra8, Pcna and Vimentin proteins. Long-term evaluation of the seminiferous epithelium and sperm quality were carried out at 70 dpp. The DEHP animal group presented gonocytic degeneration with delayed differentiation, causing a reduction in the population of spermatogonia (Stra8 +) in the cellular proliferation (Pcna+) and disorganization of Vimentin filaments. These events had long-term repercussions on the quality of the seminiferous epithelium and semen. Our study demonstrates that at birth, there is a period that the testes are extremely sensitive to DEHP exposure, which leads to gonocytic degeneration and delay in their differentiation. This situation can have long-term repercussions or permanent effects on the quality of the seminiferous epithelium and sperm parameters.

Perturbation of IP3R-dependent endoplasmic reticulum calcium homeostasis by PPARδ-activated metabolic stress leads to mouse spermatocyte apoptosis: A direct mechanism for perfluorooctane sulfonic acid-induced spermatogenic disorders

Perfluorooctane sulfonic acid (PFOS) as an archetypal representative of per- and polyfluoroalkyl substances (PFAS) is ubiquitously distributed in the environment and extensively detected in human bodies. Although accumulating evidence is suggestive of the deleterious effects of PFOS on male reproduction, the direct toxicity of PFOS towards spermatogenic cells and the relevant mechanisms remain poorly understood. The aims of the present study were to explore the direct effects and underlying molecular mechanisms of PFOS on spermatogenesis. Through integrating animal study, transcriptome profiling, in silico toxicological approaches, and in vitro validation study, we identified the molecular initiating event and key events contributing to PFOS-induced spermatogenic impairments. The mouse experiments revealed that spermatocytes were involved in PFOS-induced spermatogenic disorders and the activation of peroxisome proliferator-activated receptor delta (PPARδ) was linked to spermatocyte loss in PFOS-administrated mice. GC-2spd(ts) cells were treated with an increased gradient of PFOS, which was relevant to environmental and occupational exposure levels of PFOS in populations. Following 72-h treatment, cells was harvested for RNA sequencing. The transcriptome profiling and benchmark dose (BMD) modeling identified endoplasmic reticulum (ER) stress as the key event for PFOS-mediated spermatocyte apoptosis and determined the point-of-departure (PoD) for perturbations of ER stress signaling. Based on the calculated PoD value, further bioinformatics analyses combined with in vitro and in vivo validations showed that PFOS caused metabolic stress by activating PPARδ in mouse spermatocytes, which was responsible for Beclin 1-involved inositol 1,4,5-trisphosphate receptor (IP3R) sensitization. The disruption of IP3R-mediated ER calcium homeostasis triggered ER calcium depletion, leading to ER stress and apoptosis in mouse spermatocytes exposed to PFOS. This study systematically investigated the direct impacts of PFOS on spermatogenesis and unveiled the relevant molecular mechanism of PFOS-induced spermatogenic disorders, providing novel insights and potential preventive/therapeutic targets for PFAS-associated male reproductive toxicity.

CTCF-mediated 3D chromatin predetermines the gene expression program in the male germline

Spermatogenesis is a unidirectional differentiation process that generates haploid sperm, but how the gene expression program that directs this process is established is largely unknown. Here we determine the high-resolution 3D chromatin architecture of male germ cells during spermatogenesis and show that CTCF-mediated 3D chromatin predetermines the gene expression program required for spermatogenesis. In undifferentiated spermatogonia, CTCF-mediated chromatin contacts on autosomes pre-establish meiosis-specific super-enhancers (SE). These meiotic SE recruit the master transcription factor A-MYB in meiotic spermatocytes, which strengthens their 3D contacts and instructs a burst of meiotic gene expression. We also find that at the mitosis-to-meiosis transition, the germline-specific Polycomb protein SCML2 resolves chromatin loops that are specific to mitotic spermatogonia. Moreover, SCML2 and A-MYB establish the unique 3D chromatin organization of sex chromosomes during meiotic sex chromosome inactivation. We propose that CTCF-mediated 3D chromatin organization enforces epigenetic priming that directs unidirectional differentiation, thereby determining the cellular identity of the male germline.

Dissociation, enrichment, and the in vitro formation of gonocyte colonies from cryopreserved neonatal bovine testicular tissues

Gonocytes play an important role in early development of spermatogonial stem cells and fertility preservation to acquire more high quality gonocytes in vitro for further germ cell-related research and applications, it is necessarily needed to enrich and in vitro propagate gonocytes from cryopreserved bovine testicular tissues. This study aimed to investigate the isolation, enrichment, and colony formation of gonocytes in vitro for germ cell expansion from cryopreserved neonatal bovine testicular tissues. The effects of several different in vitro culture conditions, including seeding density, temperature, serum replacement and extracellular matrices were investigated for the maintenance, proliferation and formation of gonocyte colonies in vitro. Frozen/thawed two-week-old neonatal bovine testicular tissues were digested and gonocytes were enriched using a Percoll density gradient. Cell viability was accessed by trypan blue staining and cell apoptosis was evaluated by TUNEL assays. Gonocytes were identified and confirmed by immunofluorescence with the PGP9.5 germ cell marker and the OCT4 pluripotency marker while Sertoli cells were stained with vimentin. We found that neonatal bovine gonocytes were efficiently enriched by a 30%-40% Percoll density gradient (p < 0.05). No significant differences were detected between neonatal bovine testicular cells cultured at 34 °C or 37 °C. The formation of gonocyte colonies was observed in culture medium supplemented with knockout serum replacement (KSR), but not fetal bovine serum (FBS), at a seeding density higher than 5.0 × 104 cells/well. A greater number of gonocyte colonies were observed in culture plates coated with laminin (38.00 ± 6.24/well) and Matrigel (38.67 ± 3.78/well) when compared to plates coated with collagen IV and fibronectin (p < 0.05). In conclusion, bovine neonatal gonocytes were able to be efficiently isolated, enriched and maintained in gonocyte colonies in vitro; the development of this protocol provides vital information for the clinical translation of this technology and the future restoration of human fertility.

Human granulosa cells of poor ovarian responder patients display telomeres shortening

OBJECTIVE

We aimed to compare the telomere length in granulosa cells of the young normal and poor ovarian responder patients and elderly patients undergoing ovarian stimulation for IVF.

METHODS

The main outcome measures granulosa cells telomere Length in the 3 study groups of patients undergoing IVF treatment in our center. 1) young normal responder patients (< 35 years); 2) young (< 35 years) poor ovarian responder patients; and 3) Elderly patients (40-45 years). Granulosa cells were obtained at the time of oocyte retrieval. Granulosa cells telomere length was assessed by absolute human telomere length quantification qPCR Assay.

RESULTS

The telomere length of the young normal responder was significantly longer as compared to young poor ovarian responder (15.5 vs 9.6 KB, p < 0.001) and the elderly patients (15.5 vs 10.66 KB, p < 0.002). No significant difference was observed in the telomere length between the young poor ovarian responder and the elderly patients.

CONCLUSIONS

Granulosa cells telomere length of the young normal responder was found to be significantly longer than young poor ovarian responder or elderly patients, highlighting the role of telomere length as a predictor, or contributor to poor oocyte yield following IVF treatment.

Study of spermatogenic and Sertoli cells in the Hu sheep testes at different developmental stages

Spermatogenesis is a highly organized process by which undifferentiated spermatogonia self-renew and differentiate into spermatocytes and spermatids. The entire developmental process from spermatogonia to sperm occurs within the seminiferous tubules. Spermatogenesis is supported by the close interaction of germ cells with Sertoli cells. In this study, testicular tissues were collected from Hu sheep at 8 timepoints after birth: 0, 30, 90, 180, 270, 360, 540, and 720 days. Immunofluorescence staining and histological analysis were used to explore the development of male germ cells and Sertoli cells in the Hu sheep testes at these timepoints. The changes in seminiferous tubule diameter and male germ cells in the Hu sheep testes at these different developmental stages were analyzed. Then, specific molecular markers were used to study the proliferation and differentiation of spermatogonia, the timepoint of spermatocyte appearance, and the maturation and proliferation of Sertoli cells in the seminiferous tubules. Finally, the formation of the blood-testes barrier was studied using antibodies against the main components of the blood-testes barrier, β-catenin, and ZO-1. These findings not only increased the understanding of the development of the Hu sheep testes, but also laid a solid theoretical foundation for Hu sheep breeding.

Multipotent fetal stem cells in reproductive biology research

Due to the limited accessibility of the in vivo situation, the scarcity of the human tissue, legal constraints, and ethical considerations, the underlying molecular mechanisms of disorders, such as preeclampsia, the pathological consequences of fetomaternal microchimerism, or infertility, are still not fully understood. And although substantial progress has already been made, the therapeutic strategies for reproductive system diseases are still facing limitations. In the recent years, it became more and more evident that stem cells are powerful tools for basic research in human reproduction and stem cell-based approaches moved into the center of endeavors to establish new clinical concepts. Multipotent fetal stem cells derived from the amniotic fluid, amniotic membrane, chorion leave, Wharton´s jelly, or placenta came to the fore because they are easy to acquire, are not associated with ethical concerns or covered by strict legal restrictions, and can be banked for autologous utilization later in life. Compared to adult stem cells, they exhibit a significantly higher differentiation potential and are much easier to propagate in vitro. Compared to pluripotent stem cells, they harbor less mutations, are not tumorigenic, and exhibit low immunogenicity. Studies on multipotent fetal stem cells can be invaluable to gain knowledge on the development of dysfunctional fetal cell types, to characterize the fetal stem cells migrating into the body of a pregnant woman in the context of fetomaternal microchimerism, and to obtain a more comprehensive picture of germ cell development in the course of in vitro differentiation experiments. The in vivo transplantation of fetal stem cells or their paracrine factors can mediate therapeutic effects in preeclampsia and can restore reproductive organ functions. Together with the use of fetal stem cell-derived gametes, such strategies could once help individuals, who do not develop functional gametes, to conceive genetically related children. Although there is still a long way to go, these developments regarding the usage of multipotent fetal stem cells in the clinic should continuously be accompanied by a wide and detailed ethical discussion.

Branched germline cysts and female-specific cyst fragmentation facilitate oocyte determination in mice

During mouse gametogenesis, germ cells derived from the same progenitor are connected via intercellular bridges forming germline cysts, within which asymmetrical or symmetrical cell fate occurs in female and male germ cells, respectively. Here, we have identified branched cyst structures in mice, and investigated their formation and function in oocyte determination. In fetal female cysts, 16.8% of the germ cells are connected by three or four bridges, namely branching germ cells. These germ cells are preferentially protected from cell death and cyst fragmentation and accumulate cytoplasm and organelles from sister germ cells to become primary oocytes. Changes in cyst structure and differential cell volumes among cyst germ cells suggest that cytoplasmic transport in germline cysts is conducted in a directional manner, in which cellular content is first transported locally between peripheral germ cells and further enriched in branching germ cells, a process causing selective germ cell loss in cysts. Cyst fragmentation occurs extensively in female cysts, but not in male cysts. Male cysts in fetal and adult testes have branched cyst structures, without differential cell fates between germ cells. During fetal cyst formation, E-cadherin (E-cad) junctions between germ cells position intercellular bridges to form branched cysts. Disrupted junction formation in E-cad-depleted cysts led to an altered ratio in branched cysts. Germ cell-specific E-cad knockout resulted in reductions in primary oocyte number and oocyte size. These findings shed light on how oocyte fate is determined within mouse germline cysts.

The single-cell chromatin accessibility landscape in mouse perinatal testis development

Spermatogenesis depends on an orchestrated series of developing events in germ cells and full maturation of the somatic microenvironment. To date, the majority of efforts to study cellular heterogeneity in testis has been focused on single-cell gene expression rather than the chromatin landscape shaping gene expression. To advance our understanding of the regulatory programs underlying testicular cell types, we analyzed single-cell chromatin accessibility profiles in more than 25,000 cells from mouse developing testis. We showed that single-cell sequencing assay for transposase-accessible chromatin (scATAC-Seq) allowed us to deconvolve distinct cell populations and identify cis-regulatory elements (CREs) underlying cell-type specification. We identified sets of transcription factors associated with cell type-specific accessibility, revealing novel regulators of cell fate specification and maintenance. Pseudotime reconstruction revealed detailed regulatory dynamics coordinating the sequential developmental progressions of germ cells and somatic cells. This high-resolution dataset also unveiled previously unreported subpopulations within both the Sertoli and Leydig cell groups. Further, we defined candidate target cell types and genes of several genome-wide association study (GWAS) signals, including those associated with testosterone levels and coronary artery disease. Collectively, our data provide a blueprint of the 'regulon' of the mouse male germline and supporting somatic cells.

Transcriptome Profiling of Developing Testes and First Wave of Spermatogenesis in the Rat

Spermatogenesis is a complicated course of several rigorous restrained steps that spermatogonial stem cells undergo to develop into highly specialized spermatozoa; however, specific genes and signal pathways, which regulate the amplification, differentiation and maturation of these cells, remain unclear. We performed bioinformatics analyses to investigate the dynamic changes of the gene expression patterns at three time points in the course of the first wave of rat spermatogenesis. Differently expressed genes (DEGs) were identified, and the features of DEGs were further analyzed with GO (Gene Ontology), KEGG (Kyoto Encyclopedia of Genes and Genomes) and Short Time-series Expression Miner (STEM). A total of 2954 differentially expressed genes were identified. By using STEM, the top 10 key genes were selected in the profile according to the enrichment results, and the distinguishable biological functions encoded by these DEGs were automatically divided into three parts. Genes from 6, 8 and 10 days were related to biosynthesis, immune response and cell junction, and genes from 14, 15 and 16 days were related to energy metabolic pathways. The results also suggest that genes from 29, 31 and 35 days may shift metabolic to sperm motility, sperm flagellum and cilium movement.

Stem Cell-Based Therapeutic Strategies for Premature Ovarian Insufficiency and Infertility: A Focus on Aging

Reproductive aging is on the rise globally and inseparable from the entire aging process. An extreme form of reproductive aging is premature ovarian insufficiency (POI), which to date has mostly been of idiopathic etiology, thus hampering further clinical applications and associated with enormous socioeconomic and personal costs. In the field of reproduction, the important functional role of inflammation-induced ovarian deterioration and therapeutic strategies to prevent ovarian aging and increase its function are current research hotspots. This review discusses the general pathophysiology and relative causes of POI and comprehensively describes the association between the aging features of POI and infertility. Next, various preclinical studies of stem cell therapies with potential for POI treatment and their molecular mechanisms are described, with particular emphasis on the use of human induced pluripotent stem cell (hiPSC) technology in the current scenario. Finally, the progress made in the development of hiPSC technology as a POI research tool for engineering more mature and functional organoids suitable as an alternative therapy to restore infertility provides new insights into therapeutic vulnerability, and perspectives on this exciting research on stem cells and the derived exosomes towards more effective POI diagnosis and treatment are also discussed.

Localization and characterization of SSCs from pre-pubertal bovine testes

Self renewal and proliferation ability of spermatogonial stem cells (SSCs) support spermatogenesis during adult life. Theoretically, these stem cells can be utilized for transmission of genetic information to descendants via testicular transplantation. However, lack of knowledge in methodologies for identification of SSCs limits the application of SSCs transplantation in domestic animals. Accumulated studies have shown that SSCs specific markers (DBA, UCHL1) and stem cell marker (Sox2, Oct4) are useful to screen SSCs that able to be used for transplantation. However, in cattle, less information is available on the expression status of these markers till date. Therefore, a study was carried out in 2019 at Tsukuba University, Japan where testes from 3, 5 and 7 months old calves were utilized to examine testicular localization and in vitro propogation of stem cell markers. SSCs were isolated by enzymatic digestion combined with centrifugal separation on discontinuous Percoll density gradient. Cell propagation and SSCs marker expression were determined at 5, 10 and 15 days post-culture. Immunostaining in conjunction with Western Blot analysis of cultured cells showed that stem cell markers (UCHL1, Oct4 and Sox2) were expressed in SSCs suggesting that differentiation of gonocyte started by 3 months and SSCs differentiation begins after 5 months of age. Taken together, these results demonstrated marker expression and localization of bull SSCs and showed that in vitro culturing of bull SSCs is implementable.

Cryptorchidism: The dog as a study model

Cryptorchidism (CO) or undescended testicle is an abnormality of male gonadal development that can generate long-term repercussions in men, such as infertility and germ cell neoplasia in situ (GCNIS). The origin of these alterations in humans is not completely clear, due to the absence of an animal model with similar testicular development as in humans with CO. This work intends to describe the testicular histological development of dogs with congenital CO, and determine whether the species could adequately serve as a study model for this pathology in humans. The study was carried out with 36 dogs, equally distributed in two groups: healthy control (CTRL) and CO groups. The contralateral testis to the undescended one in CO group of the animals was considered and analyzed. Each group was subdivided in three stages of development: (1) peripubertal stage (6–8 months), (2) young adult (9–48 months) and (3) senile (49–130 months). Histological development, the presence of cells with gonocyte morphology, cell proliferation, testicular lipoperoxidation and hormonal concentrations of testosterone, estradiol, FSH and LH were evaluated and described. In the cryptorchid testes, the first histological alterations appeared from the first stage of development and were maintained until the senile stage. A pronounced testicular lipoperoxidation occurred only in the second stage of development. The histological alterations due to CO were markedly evident in the young adult stage. Testosterone concentrations witnessed a decrease starting from in the second stage and kept on until the last stage. The contralateral testes of the CO animals showed alterations that positioned them between the control and CO testes. Testicular development of dogs with CO is similar to that of humans. The results of the study suggest that this species could serve as a suitable model for the study of CO in humans.

10−7 M genistein partially alleviates 10−7 M MEHP unfavorable effects in a new modified fetal rat testis culture system

Background: Recent studies revealed that some common endocrine-disrupting chemicals (EDCs) including phthalates and phytoestrogens may exhibit low-dose effects properties. However, how low dose of these EDCs and their mixture would affect fetal rat testis development still needs further investigation. Moreover, testis organ culture system also needs further modification to provide an effective tool for ex vivo EDCs study.

Methods: We firstly modified the agarose organ culture system, in which fetal rat testes were cultured for 4 days (d1 to d4) on agarose gels held by Millicell inserts. Then we used the modified agarose culture system to study the combined effects of multiple EDCs exposure. 15.5 dpc fetal rat testes were isolated and treated with vehicle, MEHP (0.1 μmol/L), GEN (0.1 μmol/L) or MEHP (0.1 μmol/L) + GEN (0.1 μmol/L). Parameters concerning testicular cell development and function were evaluated, trying to gain insight into the early molecular events after multiple EDCs exposure.

Results: The development of somatic, germ cells and seminiferous tubule in 15.5 dpc fetal rat testis was better sustained in the modified agarose culture system. Based on the modified system, we found that MEHP at 0.1 μmol/L induced alterations in gonocyte markers, antioxidative enzyme activity as well as transient reduction of testosterone production, accompanied by mitochondria swelling in gonocytes and Sertoli cells. No obvious morphological and histological alterations were observed in all treated groups. However, coadministration of genistein at 0.1 μmol/L partially alleviated MEHP-induced fetal testis damage ex vivo through enhancement of antioxidative action. MEHP at low dose still showed weak endocrine disrupting properties but did not exhibit typical low-dose effects.

Conclusion: Our findings indicated that the modified agarose culture system could better mimic testicular microenvironment without obvious hypoxic cell damage. Furthermore, low dose of MEHP induced mild disruption to fetal testis development, cotreatment of genistein at low dose attenuated MEHP induced fetal testis injuries in part by balancing redox state, indicating that low dose of genistein may partially protect fetal testis from phthalates induced injury.

Triphenyltin disrupts the testicular microenvironment and reduces sperm quality in adult male rats

Triphenyltin (TPT) is organotin that is widely used as an anti-fouling agent and has been determined to have male reproductive toxicity. The objective of this study was to investigate the effects of TPT on the testicular microenvironment and sperm quality in male rats. Adult male Sprague Dawley rats were daily gavaged with TPT (0, 0.5, 1, and 2 mg/kg body weight) for 28 days. The results showed that TPT dose-dependently decreased sperm count and sperm motility, interfered with sperm histone-protamine replacement process, and significantly increased sperm deformity rate, but did not affect sperm DNA integrity. TPT at 2 mg/kg significantly decreased the gene and protein expressions of testis PCNA and Ki67, and dose-dependently decreased the number of PCNA-positive cells and Ki67-positive cells. TPT at 1 mg/kg and/or 2 mg/kg down-regulated the expression of StAR, SF1, P450scc, FSHR, WT1, DDX4 and PLZF, and up-regulated SOX9 expression. Simultaneously, TPT reduced serum testosterone levels at each dose and dose-dependently decreased the expression of Leydig cells regulators (INSL3, IGF1, inhibin B) and Sertoli cells regulators (GDNF, FGF2, CXCL12, ETV5), altered testicular microenvironment. Further, in vitro, we treated TM3 (Leydig cells), TM4 (Sertoli cells) and GC-1 (spermatogonia) cells with 1-100 nM TPT for 24 h. 100 nM TPT significantly down-regulated the expression of the above indicators in TM3 and TM4 cells but did not directly affect the cell proliferation ability of GC-1. However, after co-culturing TPT-treated TM3 or TM4 cells with GC-1 cells, it was found that TPT-treated TM3 or TM4 cells dose-dependently reduced the gene and protein expression levels of PCNA and Ki67 and increased cytotoxicity in GC-1 cells. In conclusion, TPT impairs the proliferative ability of spermatogonia by disrupting the microenvironment of Leydig cells and Sertoli cells, which in turn leads to low sperm quality in adult male rats.

Toxicity Profiles and Protective Effects of Antifreeze Proteins From Insect in Mammalian Models

Antifreeze proteins (AFPs), found in many cold-adapted organisms, can protect them from cold and freezing damages and have thus been considered as additional protectants in current cold tissue preservation solutions that generally include electrolytes, osmotic agents, colloids and antioxidants, to reduce the loss of tissue viability associated with cold-preservation. Due to the lack of toxicity profile studies on AFPs, their inclusion in cold preservation solutions has been a trial-and-error process limiting the development of AFPs' application in cold preservation. To assess the feasibility of translating the technology of AFPs for mammalian cell cold or cryopreservation, we determined the toxicity profile of two highly active beetle AFPs, DAFP1 and TmAFP, from Dendroides canadensis and Tenebrio molitor in this study. Toxicity was examined on a panel of representative mammalian cell lines including testicular spermatogonial stem cells and Leydig cells, macrophages, and hepatocytes. Treatments with DAFP1 and TmAFP at up to 500μg/mL for 48 and 72hours were safe in three of the cell lines, except for a 20% decrease in spermatogonia treated with TmAFP. However, both AFPs at 500μg/mL or below reduced hepatocyte viability by 20 to 40% at 48 and 72h. At 1000μg/mL, DAFP1 and TmAFP reduced viability in most cell lines. While spermatogonia and Leydig cell functions were not affected by 1000μg/mL DAFP1, this treatment induced inflammatory responses in macrophages. Adding 1000μg/ml DAFP1 to rat kidneys stored at 4°C for 48hours protected the tissues from cold-related damage, based on tissue morphology and gene and protein expression of two markers of kidney function. However, DAFP1 and TmAFP did not prevent the adverse effects of cold on kidneys over 72hours. Overall, DAFP1 is less toxic at high dose than TmAFP, and has potential for use in tissue preservation at doses up to 500μg/mL. However, careful consideration must be taken due to the proinflammatory potential of DAFP1 on macrophages at higher doses and the heighten susceptibility of hepatocytes to both AFPs.

Asprosin modulates testicular functions during ageing in mice

Ageing is a gradual and multi-factorial process with a significant impact on fertility. The mechanism of declined testicular functions with age remains elusive. Asprosin is a novel fasting-induced gluconeogenic adipokine that regulates glucose homeostasis. However, the expression and potential role of asprosin in testicular functions with age are largely unexplored. So, the current study was aimed to examine the variation in asprosin expression in the mice testis and its correlation with OLFR734 receptor, insulin receptor (IR), GLUT-8 and various steroidogenic markers at different stages of postnatal development. The result demonstrated the highest expression of asprosin in reproductively active mice, which decreased significantly in aged mice testis. Asprosin expression declined simultaneously with declining testosterone production, testicular glucose and expression of OLFR734, IR, GLUT-8 and AR in aged mice testis. This suggests that declining asprosin expression with advancing age may be a causative factor for regressive changes in the testis. Further, the present study also evaluated the in vitro effect of asprosin on testicular functions of aged mice testis. The results showed that asprosin treatment improves testicular functions by stimulating the expression of OLFR734, StAR, 3β-HSD,17β-HSD, IR, GLUT-8, MCT-2&4, PCNA, Bcl2 proteins alongwith increased testosterone, insulin and lactate biosynthesis. Collectively, these findings indicate that a marked decline in asprosin and its receptor OLFR734 expression may result in decreased insulin sensitivity and glucose transport, leading to regressive changes in aged mice testis. Treatment of asprosin can possibly restore the testicular functions of aged mice by augmenting the testosterone, insulin and glucose levels.

Impact of in Utero Rat Exposure to 17Alpha-Ethinylestradiol or Genistein on Testicular Development and Germ Cell Gene Expression

Although the decline in male fertility is believed to partially result from environmental exposures to xenoestrogens during critical developmental windows, the underlying mechanisms are still poorly understood. Experimental in utero exposures in rodents have demonstrated the negative impact of xenoestrogens on reproductive development, long-term adult reproductive function and offspring health. In addition, transcriptomic studies have demonstrated immediate effects on gene expression in fetal reproductive tissues, However, the immediate molecular effects on the developing germ cells have been poorly investigated. Here, we took advantage of a transgenic rat expressing the green fluorescent protein specifically in germ cells allowing purification of perinatal GFP-positive germ cells. Timed-pregnant rats were exposed to ethinylestradiol (EE2, 2 μg/kg/d), genistein (GE, 10 mg/kg/d) or vehicle by gavage, from gestational days (GD) 13–19; testes were sampled at GD20 or post-natal (PND) 5 for histological analysis and sorting of GFP-positive cells. While EE2-exposed females gained less weight during treatment compared to controls, neither treatment affected the number of pups per litter, sex ratio, anogenital distance, or body and gonadal weights of the offspring. Although GE significantly decreased circulating testosterone at GD20, no change was observed in either testicular histology or germ cell and sertoli cell densities. Gene expression was assessed in GFP-positive cells using Affymetrix Rat Gene 2.0 ST microarrays. Analysis of differentially expressed genes (DEGs) (p < 0.05; fold change 1.5) identified expression changes of 149 and 128 transcripts by EE2 and GE respectively at GD20, and 287 and 207 transcripts at PND5, revealing an increased effect after the end of treatment. Only about 1% of DEGs were common to both stages for each treatment. Functional analysis of coding DEG revealed an overrepresentation of olfactory transduction in all groups. In parallel, many non-coding RNAs were affected by both treatments, the most represented being small nucleolar and small nuclear RNAs. Our data suggest that despite no immediate toxic effects, fetal exposure to xenoestrogens can induce subtle immediate changes in germ cell gene expression. Moreover, the increased number of DEGs between GD20 and PND5 suggests an effect of early exposures with latent impact on later germ cell differentiation.

Histone Chaperones as Cardinal Players in Development

Dynamicity and flexibility of the chromatin landscape are critical for most of the DNA-dependent processes to occur. This higher-order packaging of the eukaryotic genome into the chromatin is mediated by histones and associated non-histone proteins that determine the states of chromatin. Histone chaperones- “the guardian of genome stability and epigenetic information” controls the chromatin accessibility by escorting the nucleosomal and non-nucleosomal histones as well as their variants. This distinct group of molecules is involved in all facets of histone metabolism. The selectivity and specificity of histone chaperones to the histones determine the maintenance of the chromatin in an open or closed state. This review highlights the functional implication of the network of histone chaperones in shaping the chromatin function in the development of an organism. Seminal studies have reported embryonic lethality at different stages of embryogenesis upon perturbation of some of the chaperones, suggesting their essentiality in development. We hereby epitomize facts and functions that emphasize the relevance of histone chaperones in orchestrating different embryonic developmental stages starting from gametogenesis to organogenesis in multicellular organisms.

Sertoli cell and spermatogonial development in pigs

Background

Spermatogenesis is an intricate developmental process during which undifferentiated spermatogonia, containing spermatogonial stem cells (SSCs), undergo self-renewal and differentiation to generate eventually mature spermatozoa. Spermatogenesis occurs in seminiferous tubules within the testis, and the seminiferous tubules harbor Sertoli and germ cells. Sertoli cells are an essential somatic cell type within the microenvironment that support and steer male germ cell development, whereas spermatogonia are the primitive male germ cells at the onset of spermatogenesis. While the developmental progression of Sertoli cells and spermatogonia has been well established in mice, much less is known in other mammalian species including pigs.

Results

To acquire knowledge of Sertoli cell and spermatogonial development in pigs, here we collected as many as nine ages of Duroc porcine testes from the neonate to sexual maturity, i.e., testes from 7-, 30-, 50-, 70-, 90-, 110-, 130-, 150- and 210-day-old boars, and performed histological and immunohistochemical analyses on testis sections. We first examined the development of spermatogenic cells and seminiferous tubules in porcine testes. Then, by immunofluorescence staining for marker proteins (AMH, SOX9, DBA, UCHL1, VASA, KIT, Ki67 and/or PCNA), we delved into the proliferative activity and development of Sertoli cells and of spermatogonial subtypes (pro-, undifferentiated and differentiating spermatogonia). Besides, by immunostaining for β-catenin and ZO-1, we studied the establishment of the blood-testis barrier in porcine testes.

Conclusions

In this longitudinal study, we have systematically investigated the elaborate Sertoli cell and spermatogonial developmental patterns in pigs from the neonate to sexual maturity that have so far remained largely unknown. The findings not only extend the knowledge about spermatogenesis and testicular development in pigs, but also lay the theoretical groundwork for porcine breeding and rearing.

Eicosanoid Biosynthesis in Male Reproductive Development: Effects of Perinatal Exposure to NSAIDs and Analgesic Drugs

Increasing rates of infertility associated with declining sperm counts and quality, as well as increasing rates of testicular cancer are contemporary issues in the United States and abroad. These conditions are part of the Testicular Dysgenesis Syndrome, which includes a variety of male reproductive disorders hypothesized to share a common origin based on disrupted testicular development during fetal and neonatal stages of life. Male reproductive development is a highly regulated and complex process that relies on an intricate coordination between germ, Leydig, and Sertoli cells as well as other supporting cell types, to ensure proper spermatogenesis, testicular immune privilege, and endocrine function. The eicosanoid system has been reported to be involved in the regulation of fetal and neonatal germ cell development as well as overall testicular homeostasis. Moreover, non-steroidal anti-inflammatory drugs (NSAIDs) and analgesics with abilities to block eicosanoid synthesis by targeting either or both isoforms of cyclooxygenase enzymes, have been found to adversely affect male reproductive development. This review will explore the current body of knowledge on the involvement of the eicosanoid system in male reproductive development, as well as discuss adverse effects of NSAIDs and analgesic drugs administered perinatally, focusing on toxicities reported in the testis and on major testicular cell types. Rodent and epidemiological studies will be corroborated by findings in invertebrate models for a comprehensive report of the state of the field, and to add to our understanding of the potential long-term effects of NSAID and analgesic drug administration in infants.

Effects of endocrine disrupting chemicals on gonad development: Mechanistic insights from fish and mammals

Over the past century, evidence has emerged that endocrine disrupting chemicals (EDCs) have an impact on reproductive health. An increased frequency of reproductive disorders has been observed worldwide in both wildlife and humans that is correlated with accidental exposures to EDCs and their increased production. Epidemiological and experimental studies have highlighted the consequences of early exposures and the existence of key windows of sensitivity during development. Such early in life exposures can have an immediate impact on gonadal and reproductive tract development, as well as on long-term reproductive health in both males and females. Traditionally, EDCs were thought to exert their effects by modifying the endocrine pathways controlling reproduction. Advances in knowledge of the mechanisms regulating sex determination, differentiation and gonadal development in fish and rodents have led to a better understanding of the molecular mechanisms underlying the effects of early exposure to EDCs on reproduction. In this manuscript, we review the key developmental stages sensitive to EDCs and the state of knowledge on the mechanisms by which model EDCs affect these processes, based on the roadmap of gonad development specific to fish and mammals.

Alternative splicing and MicroRNA: epigenetic mystique in male reproduction

Infertility is rarely life threatening, however, it poses a serious global health issue posing far-reaching socio-economic impacts affecting 12–15% of couples worldwide where male factor accounts for 70%. Functional spermatogenesis which is the result of several concerted coordinated events to produce sperms is at the core of male fertility, Alternative splicing and microRNA (miRNA) mediated RNA silencing (RNAi) constitute two conserved post-transcriptional gene (re)programming machinery across species. The former by diversifying transcriptome signature and the latter by repressing target mRNA activity orchestrate a spectrum of testicular events, and their dysfunctions has several implications in male infertility. This review recapitulates the knowledge of these mechanistic events in regulation of spermatogenesis and testicular homoeostasis. In addition, miRNA payload in sperm, vulnerable to paternal inputs, including unhealthy diet, infection and trauma, creates epigenetic memory to initiate intergenerational phenotype. Naive zygote injection of sperm miRNAs from stressed father recapitulates phenotypes of offspring of stressed father. The epigenetic inheritance of paternal pathologies through miRNA could be a tantalizing avenue to better appreciate ‘Paternal Origins of Health and Disease’ and the power of tiny sperm.

Sertoli Cell-Germ Cell Interactions Within the Niche: Paracrine and Juxtacrine Molecular Communications

Male germ cell development depends on multiple biological events that combine epigenetic reprogramming, cell cycle regulation, and cell migration in a spatio-temporal manner. Sertoli cells are a crucial component of the spermatogonial stem cell niche and provide essential growth factors and chemokines to developing germ cells. This review focuses mainly on the activation of master regulators of the niche in Sertoli cells and their targets, as well as on novel molecular mechanisms underlying the regulation of growth and differentiation factors such as GDNF and retinoic acid by NOTCH signaling and other pathways.

Unraveling three-dimensional chromatin structural dynamics during spermatogonial differentiation

Spermatogonial stem cells (SSCs) are able to undergo both self-renewal and differentiation. Unlike self-renewal, which replenishes the SSC and progenitor pool, differentiation is an irreversible process committing cells to meiosis. Although the preparations for meiotic events in differentiating spermatogonia (Di-SG) are likely to be accompanied by alterations in chromatin structure, the three-dimensional chromatin architectural differences between SSCs and Di-SG, and the higher-order chromatin dynamics during spermatogonial differentiation, have not been systematically investigated. Here, we performed in situ high-throughput chromosome conformation capture, RNA-seq, and chromatin immunoprecipitation-sequencing analyses on porcine undifferentiated spermatogonia (which consist of SSCs and progenitors) and Di-SG. We identified that Di-SG exhibited less compact chromatin structural organization, weakened compartmentalization, and diminished topologically associating domains in comparison with undifferentiated spermatogonia, suggesting that diminished higher-order chromatin architecture in meiotic cells, as shown by recent reports, might be preprogrammed in Di-SG. Our data also revealed that A/B compartments, representing open or closed chromatin regions respectively, and topologically associating domains were related to dynamic gene expression during spermatogonial differentiation. Furthermore, we unraveled the contribution of promoter-enhancer interactions to premeiotic transcriptional regulation, which has not been accomplished in previous studies due to limited cell input and resolution. Together, our study uncovered the three-dimensional chromatin structure of SSCs/progenitors and Di-SG, as well as the interplay between higher-order chromatin architecture and dynamic gene expression during spermatogonial differentiation. These findings provide novel insights into the mechanisms for SSC self-renewal and differentiation and have implications for diagnosis and treatment of male sub-/infertility.

In vitro impact of genistein and mono(2-ethylhexyl) phthalate (MEHP) on the eicosanoid pathway in spermatogonial stem cells

Perinatal exposures to endocrine disrupting chemicals (EDCs) alter the male reproductive system. Infants are exposed to genistein (GEN) through soy-based formula, and to Mono(2-ethylhexyl) Phthalate (MEHP), metabolite of the plasticizer DEHP. Spermatogonial stem cells (SSCs) are formed in infancy and their integrity is essential for spermatogenesis. Thus, understanding the impact of EDCs on SSCs is critical. Prostaglandins (PGs) are inflammatory mediators synthesized via the eicosanoid pathway starting with cyclooxygenases (Coxs), that regulate physiological and pathological processes. Our goal was to study the eicosanoid pathway in SSCs and examine whether it was disrupted by GEN and MEHP, potentially contributing to their adverse effects. The mouse C18-4 cell line used as SSC model expressed high levels of Cox1 and Cox2 genes and proteins, and eicosanoid pathway genes similarly to levels measured in primary rat spermatogonia. Treatments with GEN and MEHP at 10 and 100 μM decreased Cox1 gene and protein expression, whereas Cox2, phospholipase A2, prostaglandin synthases transcripts, PGE2, PGF2a and PGD2 were upregulated. Simultaneously, the transcript levels of spermatogonia progenitor markers Foxo1 and Mcam and differentiated spermatogonial markers cKit and Stra8 were increased. Foxo1 was also increased by EDCs in primary rat spermatogonia. This study shows that the eicosanoid pathway is altered during SSC differentiation and that exposure to GEN and MEHP disrupts this process, mainly driven by GEN effects on Cox2 pathway, while MEHP acts through an alternative mechanism. Thus, understanding the role of Cox enzymes in SSCs and how GEN and MEHP exposures alter their differentiation warrants further studies.

Cell-fate transition and determination analysis of mouse male germ cells throughout development

Mammalian male germ cell development is a stepwise cell-fate transition process; however, the full-term developmental profile of male germ cells remains undefined. Here, by interrogating the high-precision transcriptome atlas of 11,598 cells covering 28 critical time-points, we demonstrate that cell-fate transition from mitotic to post-mitotic primordial germ cells is accompanied by transcriptome-scale reconfiguration and a transitional cell state. Notch signaling pathway is essential for initiating mitotic arrest and the maintenance of male germ cells' identities. Ablation of HELQ induces developmental arrest and abnormal transcriptome reprogramming of male germ cells, indicating the importance of cell cycle regulation for proper cell-fate transition. Finally, systematic human-mouse comparison reveals potential regulators whose deficiency contributed to human male infertility via mitotic arrest regulation. Collectively, our study provides an accurate and comprehensive transcriptome atlas of the male germline cycle and allows for an in-depth understanding of the cell-fate transition and determination underlying male germ cell development.

Mammalian in vitro gametogenesis

[Figure: see text].

Metal Oxide Nanoparticles: Evidence of Adverse Effects on the Male Reproductive System

Metal oxide nanoparticles (MONPs) are inorganic materials that have become a valuable tool for many industrial sectors, especially in healthcare, due to their versatility, unique intrinsic properties, and relatively inexpensive production cost. As a consequence of their wide applications, human exposure to MONPs has increased dramatically. More recently, their use has become somehow controversial. On one hand, MONPs can interact with cellular macromolecules, which makes them useful platforms for diagnostic and therapeutic interventions. On the other hand, research suggests that these MONPs can cross the blood–testis barrier and accumulate in the testis. Although it has been demonstrated that some MONPs have protective effects on male germ cells, contradictory reports suggest that these nanoparticles compromise male fertility by interfering with spermatogenesis. In fact, in vitro and in vivo studies indicate that exposure to MONPs could induce the overproduction of reactive oxygen species, resulting in oxidative stress, which is the main suggested molecular mechanism that leads to germ cells’ toxicity. The latter results in subsequent damage to proteins, cell membranes, and DNA, which ultimately may lead to the impairment of the male reproductive system. The present manuscript overviews the therapeutic potential of MONPs and their biomedical applications, followed by a critical view of their potential risks in mammalian male fertility, as suggested by recent scientific literature.

Unique metabolic phenotype and its transition during maturation of juvenile male germ cells

Human male reproductive development has a prolonged prepubertal period characterized by juvenile quiescence of germ cells with immature spermatogonial stem cell (SSC) precursors (gonocytes) present in the testis for an extended period of time. The metabolism of gonocytes is not defined. We demonstrate with mitochondrial ultrastructure studies via TEM and IHC and metabolic flux studies with UHPLC-MS that a distinct metabolic transition occurs during the maturation to SSCs. The mitochondrial ultrastructure of prepubertal human spermatogonia is shared with prepubertal pig spermatogonia. The metabolism of early prepubertal porcine spermatogonia (gonocytes) is characterized by the reliance on OXPHOS fuelled by oxidative decarboxylation of pyruvate. Interestingly, at the same time, a high amount of the consumed pyruvate is also reduced and excreted as lactate. With maturation, prepubertal spermatogonia show a metabolic shift with decreased OXHPOS and upregulation of the anaerobic metabolism-associated uncoupling protein 2 (UCP2). This shift is accompanied with stem cell specific promyelocytic leukemia zinc finger protein (PLZF) protein expression and glial cell-derived neurotropic factor (GDNF) pathway activation. Our results demonstrate that gonocytes differently from mature spermatogonia exhibit unique metabolic demands that must be attained to enable their maintenance and growth in vitro.

AKT3 and related molecules as potential biomarkers responsible for cryptorchidism and cryptorchidism-induced azoospermia

BACKGROUND

Cryptorchidism is a common congenital malformation strongly related to future oligospermia and male infertility. Normally functioning early-stage spermatogonia are vital to ensure fertility. The present study aimed to identify new differentially expressed genes (DEGs) associated with signaling pathways related to spermatogonial stem cell (SSC) maintenance during early spermatogenesis.

METHODS

GEO2R was used to screen for genes differentially regulated in cryptorchidism using mRNA expression profiling data in the GEO database. DAVID was used to perform GO and KEGG enrichment analysis of DEGs to analyze their functions. A protein-protein interaction (PPI) network of DEGs was constructed using the STRING database. The hub genes in the PPI networks were identified using Maximal Clique Centrality (MCC) in Cytohubba, and the top 50 genes were displayed as hub genes using Cytoscape software. Then, the miRNAs targeting hub genes were predicted using miRWalk and an mRNA-miRNA interaction network was constructed using Cytoscape. We took the intersection of these target miRNAs and the differentially expressed miRNAs identified from a non-coding RNA sequencing dataset, GSE149084. Furthermore, the intersected miRNAs and their predicted target genes were validated in the testicular tissue of rats with cryptorchidism.

RESULTS

A total of 474 DEGs were identified, most of which were annotated to the PI3K-AKT-mTOR signaling pathway. Hub genes related to the pathway were predicted to be targeted by 27 miRNAs. Further miRNA mining revealed that miRNA-7-5p and miRNA-519d-3p were both dysregulated in cryptorchidism patients. Further, we found that these two miRNAs were predicted with high confidence to share a common target gene, AKT3. In the testicular tissue of rats with cryptorchidism, miRNA-519d-3p was upregulated while miRNA-7-5p and AKT3 were downregulated. We also found that AKT3 plays an essential role in regulating SSC state through the PI3K-AKT-mTOR signaling pathway and that AKT3 is one of the key genes related to SSC self-renewal, proliferation, and differentiation.

CONCLUSIONS

The PI3K-AKT-mTOR signaling pathway functions in SSC maintenance, and alterations in this pathway may explain defects in spermatogenesis. AKT3-related miRNAs, including hsa-miR-7-5p and hsa-miR-519d-3p, might be responsible for cryptorchidism and cryptorchidism-induced azoospermia and serve as potential biomarkers.

Culture bovine prospermatogonia with 2i medium

Germplasm cryopreservation and expansion of gonocytes/prospermatogonia or spermatogonial stem cells (SSCs) are important; however, it's difficult in cattle. Since inhibitors of Mek1/2 and Gsk3β (2i) can enhance pluripotency maintenance, effects of 2i-based medium on the cultivation of bovine prospermatogonia from the cryopreserved tissues were examined. The testicular tissues of newborn bulls were well cryopreserved. High mRNA levels of prospermatogonium/SSC markers (PLZF, GFRα-1) and pluripotency markers (Oct4/Pouf5, Sox2, Nanog) were detected and the PLZF⁺ /GFRα-1⁺ prospermatogonia were consistently identified immunohistochemically in the seminiferous cords. Using differential plating and Percoll-based centrifugation, 41.59% prospermatogonia were enriched and they proliferated robustly in 2i medium. The 2i medium boosted mRNA abundances of Pouf5, Sox2, Nanog, GFRα-1, PLZF, anti-apoptosis gene Bcl2, LIF receptor gene LIFR and enhanced PLZF protein expression, but suppressed mRNA expressions of spermatogonial differentiation marker c-kit and pro-apoptotic gene Bax, in the cultured prospermatogonia. It also alleviated H₂ O₂ -induced apoptosis of the enriched cells and decreased histone H3 lysine (K9) trimethylation (H3K9me3) and its methylase Suv39h1/2 mRNA level in the cultured seminiferous cords. Overall, 2i medium improves the cultivation of bovine prospermatogonia isolated from the cryopreserved testes, by inhibiting Suv39h1/2-mediated H3K9me3 through Mek1/2 and Gsk3β signalling, evidencing successful cryopreservation and expansion of bovine germplasm.

Metabolic Requirements for Spermatogonial Stem Cell Establishment and Maintenance In Vivo and In Vitro

The spermatogonial stem cell (SSC) is a unique adult stem cell that requires tight physiological regulation during development and adulthood. As the foundation of spermatogenesis, SSCs are a potential tool for the treatment of infertility. Understanding the factors that are necessary for lifelong maintenance of a SSC pool in vivo is essential for successful in vitro expansion and safe downstream clinical usage. This review focused on the current knowledge of prepubertal testicular development and germ cell metabolism in different species, and implications for translational medicine. The significance of metabolism for cell biology, stem cell integrity, and fate decisions is discussed in general and in the context of SSC in vivo maintenance, differentiation, and in vitro expansion.

Fetal and Postnatal Nicotine Exposure Modifies Maturation of Gonocytes to Spermatogonia in Mice

Studies in laboratory animals have shown that male offspring from dams, exposed to nicotine during pregnancy and postnatal periods, show alterations in fertility, although the origin of this is still uncertain. In this study, we examined in a mouse model if the process of gonocyte maturation to spermatogonia was affected in male offspring from dams with nicotine administration during pregnancy and postnatal periods. BALB/C mice, with and without nicotine administrations in pregnancy and postnatal periods, were studied. The animals were euthanized at 3, 7, 10, 16, and 35 days postpartum (dpp). Testicular tissue samples were processed for histological, ultrastructural, and immunohistochemical studies; and testicular lipoperoxidation was determined. It was observed that in the nicotine-exposed animals, there was increased apoptosis and a reduction in the number of gonocytes that matured to spermatogonia. This gonocyte-spermatogonia maturation reduction was associated with a greater immunoreactivity to nicotinic acetylcholine receptors in the germ cells. Lipoperoxidation was similar in both groups until 16 dpp, with significant reduction at 35 dpp. Our findings suggest that nicotine intake during pregnancy and postnatal periods can affect the process of maturation of gonocytes to spermatogonia and the pool of available spermatogonia for spermatogenesis.

E4 Transcription Factor 1 (E4F1) Regulates Sertoli Cell Proliferation and Fertility in Mice

Simple Summary

Male fertility relies on the generation of functional sperm in seminiferous tubules of the testis. In mammals, Sertoli cells are the only somatic cells that directly interact with spermatogenic cells. Compelling evidences suggest that the number of Sertoli cells determines testis size and sperm output, however, molecular mechanisms regulating Sertoli cell proliferation and maturation are not well-understood. Using a Sertoli cell specific loss-of-function approach, here we showed that transcription factor E4F1 played an important role in murine Sertoli cell proliferation. Compared with their littermate control, E4f1 conditional knockout male mice sired a significantly low number of pups. E4f1 deletion resulted in reduced Sertoli cell number and testis size. Further analyses revealed that E4f1 deletion affected Sertoli cell proliferation in the neonatal testis and caused an increase in apoptosis of spermatogenic cells without affecting normal development of spermatogonia, meiotic and post-meiotic germ cells. These findings have shed new light on molecular controlling of spermatogenesis in mice and a similar mechanism likely exists in other animals.

Abstract

In the mammalian testes, Sertoli cells are the only somatic cells in the seminiferous tubules that provide structural, nutritional and regulatory support for developing spermatogenic cells. Sertoli cells only proliferate during the fetal and neonatal periods and enter a quiescent state after puberty. Functional evidences suggest that the size of Sertoli cell population determines sperm production and fertility. However, factors that direct Sertoli cell proliferation and maturation are not fully understood. Transcription factor E4F1 is a multifunctional protein that serves essential roles in cell fate decisions and because it interacts with pRB, a master regulator of Sertoli cell function, we hypothesized that E4F1 may have a functional role in Sertoli cells. E4f1 mRNA was present in murine testis and immunohistochemical staining confirmed that E4F1 was enriched in mature Sertoli cells. We generated a conditional knockout mouse model using Amh-cre and E4f1^flox/flox lines to study E4F1 fucntion in Sertoli cells and the results showed that E4f1 deletion caused a significant reduction in testis size and fertility. Further analyses revealed that meiosis progression and spermiogenesis were normal, however, Sertoli cell proliferation was impaired and germ cell apoptosis was elevated in the testis of E4f1 conditional knockout mice. On the basis of these findings, we concluded that E4F1 was expressed in murine Sertoli cells and served important functions in regulating Sertoli cell proliferation and fertility.

Function and transcriptomic dynamics of Sertoli cells during prospermatogonia development in mouse testis

In mammals, spermatogonial stem cells (SSCs) arise from a subpopulation of prospermatogonia during neonatal testis development. Currently, molecular mechanisms directing the prospermatogonia to spermatogonial transition are not well understood. In the study, we found that reducing Sertoli cells number by Amh-cre mediated expression of diphtheria toxin (AC;DTA) in murine fetal testis caused defects in prospermatogonia fate decisions. Histological and immunohistochemical analyses confirmed that Sertoli cells loss occurred at embryonic day (E) 14.5. Prospermatogonia maintained mitotic arrest at E16.5 in control animals, in contrast, 13.4% of germ cells in AC;DTA testis reentered cell cycle and expressed gH2A.X and Sycp3, indicating the commitment to meiosis. After birth, the number of prospermatogonia resuming mitosis was significantly affected by Sertoli cell loss in AC;DTA animals. Lastly, we isolated primary Sertoli cells using a Sertoli cell specific GFP reporter line and showed dynamics of Sertoli cell transcriptomes at E12.5, E13.5, E16.5 and P1. By further analysis, we revealed unique gene expression patterns and potential candidate genes regulating Sertoli cell development and likely mediating interactions between Sertoli cells, prospermatogonia and other testicular cells.

Does the apoptosis pathway play a critical role in gonocyte transformation?

PURPOSE

Undescended Testes (UDT) are prevalent in 2%-5% of male infants and cause malignancy and infertility. During germ cell development, abnormal gonocytes usually undergo apoptosis. This process is believed to involve BAX (Bcl-2 Associated X) protein in clearing abnormal gonocytes which may fail in UDT, resulting in persisting gonocytes causing seminomas later in life. We aim to investigate the role of BAX in gonocyte apoptosis.

MATERIALS AND METHODS

BAXKO (BAX-knockout) mice were back-crossed to OG2 mice (Oct4-promoter driving enhanced green fluorescent protein-eGFP) to produce BAXOG2 mice. Testes (wildtype-BAX^+/+, heterozygous-BAX^+/- and homozygous-BAX^-/- mice, n = 6/group) on postnatal days 1, 3, 6, 9 were fixed and embedded in OCT for frozen sectioning. Sections were labeled with Anti-Müllerian Hormone (Sertoli cell marker), Mouse Vasa Homolog (germ cell marker) and DAPI (nucleus marker) and imaged using confocal microscopy. Oct4-GFP+ve germ cells, germ cells on/off the basement membrane and Sertoli cells were counted using ImageJ followed by data analysis with GraphPad.

RESULTS

BAX^-/-OG2 mice had significantly higher number of germ cells/tubule comparing to BAX^+/+OG2 on day 9. There were Oct4-GFP+ve gonocyte-like germ cells that persisted in the center of the tubules in BAX^-/-OG2 even after the completion of gonocyte transformation. This suggests that abnormal gonocytes in BAX^-/-OG2 mice failed to undergo apoptosis and are allowed to persist.

CONCLUSION

This study demonstrated that apoptosis is important in regulating germ cell migration and differentiation during gonocyte transformation in neonatal mice. In addition, inhibition of apoptosis results in persisting neonatal gonocytes which might become seminomas in patients with UDT.

In-vitro differentiation of early pig spermatogenic cells to haploid germ cells

Spermatogonial stem cells (SSCs) self-renew and contribute genetic information to the next generation. Pig is wildly used as a model animal for understanding reproduction mechanisms of human being. Inducing directional differentiation of porcine SSCs may be an important strategy in exploring the mechanisms of spermatogenesis and developing better treatment methods for male infertility. Here, we established an in-vitro culture model for porcine small seminiferous tubule segments, to induce SSCs to differentiate into single-tail haploid spermatozoa. The culture model subsequently enabled spermatozoa to express the sperm-specific protein acrosin and oocytes to develop to blastocyst stage after round spermatid injection. The addition of retinoic acid (RA) to the differentiation media promoted the efficiency of haploid differentiation. RT-PCR analysis indicated that RA stimulated the expression of Stra8 but reduced the expression of NANOS2 in spermatogonia. Genes involved in post-meiotic development, transition protein 1 (Tnp1) and protamine 1 (Prm1) were upregulated in the presence of RA. The addition of an RA receptor (RAR) inhibitor, BMS439, showed that RA enhanced the expression of cAMP responsive-element binding protein through RAR and promoted the formation of round spermatids. We established an efficient culture system for in-vitro differentiation of pig SSCs. Our study represents a model for human testis disease and toxicology screening. Molecular regulators of SSC differentiation revealed in this study might provide a therapeutic strategy for male infertility.

In utero exposure to low doses of genistein and di-(2-ethylhexyl) phthalate (DEHP) alters innate immune cells in neonatal and adult rat testes

BACKGROUND

Although humans are exposed to mixtures of endocrine disruptor chemicals, few studies have examined their toxicity on male reproduction. We previously found that fetal exposure to a mixture of the phytoestrogen genistein (GEN) and the plasticizer di(2-ethylhexyl) phthalate (DEHP) altered gene expression in adult rat testes.

OBJECTIVES

Our goal was to investigate the effects of fetal exposure to GEN-DEHP mixtures at two doses relevant to humans on testicular function and transcriptome in neonatal and adult rats.

MATERIALS AND METHODS

Pregnant SD rats were gavaged with vehicle, GEN or DEHP, alone or mixed at 0.1 and 10 mg/kg/day, from gestation day 14 to birth. Fertility, steroid levels, and testis morphology were examined in neonatal and adult rats. Testicular transcriptomes were examined by gene array and functional pathway analyses. Cell-specific genes/proteins were determined by quantitative real-time PCR and immunohistochemistry.

RESULTS

GEN-DEHP mixtures increased the rates of infertility and abnormal testes in adult rats. Gene array analysis identified more genes exclusively altered by the mixtures than individual compounds. Altered top canonical pathways included urogenital/reproductive developmental and inflammatory processes. GEN-DEHP mixtures increased innate immune cells and macrophages markers at both doses and ages, more strongly and consistently than DEHP or GEN alone. Genes exclusively increased by the mixture in adult testis related to innate immune cells and macrophages included Kitlg, Rps6ka3 (Rsk2), Nr3c1, Nqo1, Lif, Fyn, Ptprj (Dep-1), Gpr116, Pfn2, and Ptgr1.

DISCUSSION AND CONCLUSION

These findings demonstrate that GEN-DEHP mixtures at doses relevant to human induce adverse testicular phenotypes, concurrent with age-dependent and non-monotonic changes in testicular transcriptomes. The involvement of innate immune cells such as macrophages suggests immediate and delayed inflammatory responses which may contribute to testicular dysfunction. Moreover, these effects are complex and likely involve multiple interactions between immune and non-immune testicular cell types that will entail further studies.

Cryptorchidism, gonocyte development, and the risks of germ cell malignancy and infertility: A systematic review

BACKGROUND/AIM

Cryptorchidism, or undescended testis (UDT) occurs in 1%-4% of newborn males and leads to a risk of infertility and testicular malignancy. Recent research suggests that infertility and malignancy in UDT may be caused by abnormal development of the neonatal germ cells, or gonocytes, which normally transform into spermatogonial stem cells (SSC) or undergo apoptosis during minipuberty at 2-6 months in humans (2-6 days in mice). We aimed to identify the current knowledge on how UDT is linked to infertility and malignancy.

METHODS

Here we review the literature from 1995 to the present to assess the possible causes of infertility and malignancy in UDT, from both human studies and animal models.

RESULTS

Both the morphological steps and many of the genes involved in germ cell development are now characterized, but the factors involved in gonocyte transformation and apoptosis in both normal and cryptorchid testes are not fully identified. During minipuberty there is evidence for the hypothalamic-pituitary axis stimulating gonocyte transformation, but without known direct control by LH and androgen, although FSH may have a role. An arrested gonocyte maybe the origin of later malignancy at least in syndromic cryptorchid testes in humans, which is consistent with the recent finding that gonocytes are normally absent in a rodent model of congenital cryptorchidism, where malignancy has not been reported.

CONCLUSION

The results of this review strengthen the view that malignancy and infertility in men with previous UDT may be caused by abnormalities in germ cell development during minipuberty.

TYPE OF STUDY

Systematic review (secondary, filtered) LEVEL OF EVIDENCE: Level I.

Low Dose of Genistein Alleviates Mono-(2-Ethylhexyl) Phthalate-Induced Fetal Testis Disorder Based on Organ Culture Model

Mono-(2-ethylhexyl) phthalate (MEHP) and genistein have been classified as endocrine-disrupting chemicals (EDCs) which interfere with the differentiation and development of the male reproductive system. However, how these two EDCs would affect fetal rat testis development at a low dose was rarely studied. In this study, we established the organ culture system and applied it to evaluate testicular effects following multiple EDC exposure at a low dose. 15.5 days postcoitum fetal rat testes were dissected, cultured, and exposed to vehicle (control), GEN (1 μmol/L, G), MEHP (1 μmol/L, M), or GEN (1 μmol/L)+MEHP (1 μmol/L, G+M). Testicular cell markers, testosterone concentration, redox state, testicular histology, and testicular ultrastructure were evaluated. Our results showed that a low dose of MEHP suppressed the development of Sertoli cells, Leydig cells, and gonocytes by triggering oxidative injuries, which was consistent with the ultrastructural findings. However, coadministration of genistein at a low dose could partially attenuate MEHP-induced fetal testis damage through antioxidative action. Cotreatment of genistein at a low dose may have a promising future on its protecting role for attenuating other EDC-induced reproductive disorders during early life. Based on the results, it can be speculated that dietary intake of isoflavones may make the fetal testis less susceptible to phthalate-induced injury.

Cyclin A2 is essential for mouse gonocyte maturation

In mammals, male gonocytes are derived from primordial germ cells during embryogenesis, enter a period of mitotic proliferation, and then become quiescent until birth. After birth, the gonocytes proliferate and migrate from the center of testicular cord toward the basement membrane to form the pool of spermatogonial stem cells (SSCs) and establish the SSC niche architecture. However, the molecular mechanisms underlying gonocyte proliferation, migration and differentiation are largely unknown. Cyclin A2 is a key component of the cell cycle and required for cell proliferation. Here, we show that cyclin A2 is required in mouse male gonocyte development and the establishment of spermatogenesis in the neonatal testis. Loss of cyclin A2 function in embryonic gonocytes by targeted gene disruption affected the regulation of the male gonocytes to SSC transition, resulting in the disruption of SSC pool formation, imbalance between SSC self-renewal and differentiation, and severely abnormal spermatogenesis in the adult testis.

Generation of human oogonia from induced pluripotent stem cells in culture

The human germ-cell lineage originates as human primordial germ cells (hPGCs). hPGCs undergo genome-wide epigenetic reprogramming and differentiate into oogonia or gonocytes, precursors for oocytes or spermatogonia, respectively. Here, we describe a protocol to differentiate human induced pluripotent stem cells (hiPSCs) into oogonia in vitro. hiPSCs are induced into incipient mesoderm-like cells (iMeLCs) using activin A and a WNT pathway agonist. iMeLCs, or, alternatively, hPSCs cultured with divergent signaling inhibitors, are induced into hPGC-like cells (hPGCLCs) in floating aggregates by cytokines including bone morphogenic protein 4. hPGCLCs are aggregated with mouse embryonic ovarian somatic cells to form xenogeneic reconstituted ovaries, which are cultured under an air-liquid interface condition for ~4 months for hPGCLCs to differentiate into oogonia and immediate precursory states for oocytes. To date, this is the only approach that generates oogonia from hPGCLCs. The protocol is suitable for investigating the mechanisms of hPGC specification and epigenetic reprogramming.

Monophosphoryl lipid A alleviated radiation-induced testicular injury through TLR4-dependent exosomes

Radiation protection on male testis is an important task for ionizing radiation-related workers or people who receive radiotherapy for tumours near the testicle. In recent years, Toll-like receptors (TLRs), especially TLR4, have been widely studied as a radiation protection target. In this study, we detected that a low-toxicity TLR4 agonist monophosphoryl lipid A (MPLA) produced obvious radiation protection effects on mice testis. We found that MPLA effectively alleviated testis structure damage and cell apoptosis induced by ionizing radiation (IR). However, as the expression abundance differs a lot in distinct cells and tissues, MPLA seemed not to directly activate TLR4 singling pathway in mice testis. Here, we demonstrated a brand new mechanism for MPLA producing radiation protection effects on testis. We observed a significant activation of TLR4 pathway in macrophages after MPLA stimulation and identified significant changes in macrophage-derived exosomes protein expression. We proved that after MPLA treatment, macrophage-derived exosomes played an important role in testis radiation protection, and specially, G-CSF and MIP-2 in exosomes are the core molecules in this protection effect.