A detailed protocol for a rapid analysis of testicular cell populations using flow cytometry

Environmentally relevant DEHP exposure during gestational and lactational period inhibits filamin a testicular expression

Toxicological studies have revealed that DEHP exposure during pregnancy may induce developmental disorders, especially in male offspring, leading to morphological and functional alterations in the reproductive system by mechanisms that should be investigated. Thus, the aim of this work was to analyze the testicular toxicity induced by an environmentally relevant DEHP dose during development and its impact on FLNA, a protein that participates in the blood-testis barrier assembly. We used male Wistar rats exposed to DEHP during pregnancy and lactation. The results showed that DEHP exposure during development and lactation increased body weight, decreased gonadal weight and shortened anogenital distance. This phthalate induced morphological changes in the testis, suggestive of hypospermatogenesis. DEHP exposure decreased the number of FLNA positive cells and the expression of FLNA and claudin-1 in prepubertal testes. Furthermore, DEHP inhibited FLNA and claudin-1 protein expression in adult male rats. These results indicated that exposure to DEHP during gestation and lactation perturbed testis development and suggested that FLNA is a target protein of DEHP, possibly contributing to the phthalate-induced damage on BTB.

Generation of rat offspring using spermatids produced through in vitro spermatogenesis

An in vitro spermatogenesis method using mouse testicular tissue to produce fertile sperm was established more than a decade ago. Although this culture method has generally not been effective in other animal species, we recently succeeded in improving the culture condition to induce spermatogenesis of rats up to the round spermatid stage. In the present study, we introduced acrosin-EGFP transgenic rats in order to clearly monitor the production of haploid cells during spermatogenesis in vitro. In addition, a metabolomic analysis of the culture media during cultivation revealed the metabolic dynamics of the testis tissue. By modifying the culture media based on these results, we were able to induce rat spermatogenesis repeatedly up to haploid cell production, including the formation of elongating spermatids, which was confirmed histologically and immunohistochemically. Finally, we performed a microinsemination experiment with in vitro produced spermatids, which resulted in the production of healthy and fertile offspring. This is the first demonstration of the in vitro production of functional haploid cells that yielded offspring in animals other than mice. These results are expected to provide a basis for the development of an in vitro spermatogenesis system applicable to many other mammals.

Sirt3 deficiency accelerates ovarian senescence without affecting spermatogenesis in aging mice

Sirtuin-3 (SIRT3), the main deacetylase in the mitochondria, maintains cellular energy metabolism and redox balance by deacetylating mitochondrial proteins in a NAD⁺-dependent manner. Growing evidence indicates that decreased Sirt3 expression is involved in various age-related maladies. However, the role of Sirt3 in ovarian and testicular senescence remains unclear. In this study, we observed that sirt3 expression showed age-dependent decreases in the ovary but not the testis. We generated Sirt3 null mice via CRISPR/Cas9-mediated genome editing. We observed that Sirt3 deletion accelerated ovarian aging, as shown by a decrease in offspring sizes, the follicle reserve and oocytes markers (Bmp15 and Gdf9) as well as increased expression of aging and inflammation-related genes (p16, p21, Il-1α, and Il-1β). Sirt3 deficiency led to an accumulation of superoxide and disruption of spindle assembly accompanied by mitochondrial dysfunction (uneven mitochondria distribution, decreased mitochondrial potential as well as reduced mitochondrial DNA content) in aging oocytes. Meanwhile, in ovaries of Sirt3 null mice, the impaired mitochondrial functions were shown by decreases in mitochondrial respiratory complexes, along with lower levels of mitochondrial fusion (OPA1, MFN2) and fission (DRP1, FIS1) proteins. er levels of mitochondrial fusion (OPA1, MFN2) and fission (DRP1, FIS1) proteins. Interestingly, Sirt3^-/- male mice exhibited no changes on the testicular histology, serum testosterone levels, germ-cell proliferation, and differentiation of spermatogonia. Meiotic prophase I spermatocytes were also normal. Levels of superoxide, mitochondrial potential as well as expression of mitochondrially-encoded genes were unaltered in Sirt3^-/- testes. Collectively, the results indicated that SIRT3 plays a critical role in maintaining the ovarian follicle reserve and oocyte quality in aging mice, suggesting its important role in controlling ovarian senescence.

Long-term effects of early postnatal stress on Sertoli cells

Sertoli cells are somatic cells in testis essential for spermatogenesis, that support the development, maturation, and differentiation of germ cells. Sertoli cells are metabolically highly active and physiologically regulated by external signals, particularly factors in the blood stream. In disease conditions, circulating pathological signals may affect Sertoli cells and consequentially, alter germ cells and fertility. While the effects of stress on reproductive cells have been well studied, how Sertoli cells respond to stress remains poorly characterized. We used a mouse model of early postnatal stress to assess the effects of stress on Sertoli cells. We developed an improved strategy based on intracellular stainings and obtained enriched preparations of Sertoli cells from exposed males. We show that adult Sertoli cells have impaired electron transport chain (ETC) pathways and that several components of ETC complexes particularly complex I, III, and IV are persistently affected. We identify serum as potential mediator of the effects of stress on Sertoli cells by showing that it can recapitulate ETC alterations in primary cells. These results highlight Sertoli cells as cellular targets of stress in early life that can keep a trace of exposure until adulthood.

Human-specific gene CT47 blocks PRMT5 degradation to lead to meiosis arrest

Exploring the functions of human-specific genes (HSGs) is challenging due to the lack of a tractable genetic model system. Testosterone is essential for maintaining human spermatogenesis and fertility, but the underlying mechanism is unclear. Here, we identified Cancer/Testis Antigen gene family 47 (CT47) as an essential regulator of human-specific spermatogenesis by stabilizing arginine methyltransferase 5 (PRMT5). A humanized mouse model revealed that CT47 functions to arrest spermatogenesis by interacting with and regulating CT47/PRMT5 accumulation in the nucleus during the leptotene/zygotene-to-pachytene transition of meiosis. We demonstrate that testosterone induces nuclear depletion of CT47/PRMT5 and rescues leptotene-arrested spermatocyte progression in humanized testes. Loss of CT47 in human embryonic stem cells (hESCs) by CRISPR/Cas9 led to an increase in haploid cells but blocked the testosterone-induced increase in haploid cells when hESCs were differentiated into haploid spermatogenic cells. Moreover, CT47 levels were decreased in nonobstructive azoospermia. Together, these results established CT47 as a crucial regulator of human spermatogenesis by preventing meiosis initiation before the testosterone surge.

Loss of Profilin3 Impairs Spermiogenesis by Affecting Acrosome Biogenesis, Autophagy, Manchette Development and Mitochondrial Organization

Profilins (PFNs) are key regulatory proteins for the actin polymerization in cells and are encoded in mouse and humans by four Pfn genes. PFNs are involved in cell mobility, cell growth, neurogenesis, and metastasis of tumor cells. The testes-specific PFN3 is localized in the acroplaxome-manchette complex of developing spermatozoa. We demonstrate that PFN3 further localizes in the Golgi complex and proacrosomal vesicles during spermiogenesis, suggesting a role in vesicle transport for acrosome formation. Using CRISPR/Cas9 genome editing, we generated mice deficient for Pfn3. Pfn3-/- males are subfertile, displaying a type II globozoospermia. We revealed that Pfn3-/- sperm display abnormal manchette development leading to an amorphous sperm head shape. Additionally, Pfn3-/- sperm showed reduced sperm motility resulting from flagellum deformities. We show that acrosome biogenesis is impaired starting from the Golgi phase, and mature sperm seems to suffer from a cytoplasm removal defect. An RNA-seq analysis revealed an upregulation of Trim27 and downregulation of Atg2a. As a consequence, mTOR was activated and AMPK was suppressed, resulting in the inhibition of autophagy. This dysregulation of AMPK/mTOR affected the autophagic flux, which is hallmarked by LC3B accumulation and increased SQSTM1 protein levels. Autophagy is involved in proacrosomal vesicle fusion and transport to form the acrosome. We conclude that this disruption leads to the observed malformation of the acrosome. TRIM27 is associated with PFN3 as determined by co-immunoprecipitation from testis extracts. Further, actin-related protein ARPM1 was absent in the nuclear fraction of Pfn3-/- testes and sperm. This suggests that lack of PFN3 leads to destabilization of the PFN3-ARPM1 complex, resulting in the degradation of ARPM1. Interestingly, in the Pfn3-/- testes, we detected increased protein levels of essential actin regulatory proteins, cofilin-1 (CFL1), cofilin-2 (CFL2), and actin depolymerizing factor (ADF). Taken together, our results reveal the importance for PFN3 in male fertility and implicate this protein as a candidate for male factor infertility in humans.

Disruption of anchoring junctions in the testes of experimental varicocele rats

Varicocele is a common disease of the male reproductive system and is the main cause of male infertility; however, the pathological mechanisms of varicocele remain unclear. The anchoring junctions (AJs) in the testies are located between Sertoli cells, or between Sertoli cells and germ cells. Intact and functional AJs are crucial for spermatogenesis. In the present study, the histomorphology, ultrastructure of AJ, cell cycle, expression of AJ structural proteins, and the level of AJ-associated signaling molecules were investigated in the left testes of experimental varicocele rats at 8 and 12 weeks after surgery. The results revealed that varicocele induced the loss of premature germ cells from the seminiferous epithelium. Furthermore, the results of the present study also revealed damage to the AJ ultrastructure, disorientation of the spermatid head, deregulation of the cell cycle, downregulation of AJ structural proteins, enhanced phosphorylation of focal adhesion kinase (FAK) at Tyr³⁹⁷ and its downstream adapter Src at Tyr⁴¹⁶, and activation of the extracellular signal-regulated protein kinase 1 (ERK1) signaling pathway. Thus, the present study demonstrated that varicocele disrupted the structure and function of AJs in the left testes of rats, and that enhancement of FAK phosphorylation may contribute to AJ damage by activating ERK1 signaling, disrupting actin-based filament networks, and altering the balance of the apical ectoplasmic specialization-blood testis barrier functional axis. These findings provide important insights into the pathological mechanisms through which varicocele contributes to male infertility and could help to identify new therapeutic targets for varicocele.

Transgenerational effects of BDE-209 on male reproduction in F3 offspring rats

Decabromodiphenyl ether (BDE-209), a congener of polybrominated diphenyl ethers, is a commonly used brominated flame retardant and a known endocrine disrupting chemical (EDC). Knowledge about the effects of prenatal BDE-209 exposure on male reproduction and whether transgenerational effects occur in subsequent generations are scant. Therefore, in this study, we tested the hypothesis that prenatal exposure to BDE-209 disrupted sperm function in the F1, F2, and F3 generations of male rats. Pregnant Sprague-Dawley rats were treated by gavage from gestation day 0 to birth with 5 mg BDE-209/kg/day. This treatment was based on the lowest-observed-adverse-effect level for DNA damage to sperm in male offspring. On postnatal day 84 for all generations, epididymal sperm counts, motility, morphology, reactive oxygen species generation, sperm chromatin DNA structure integrity, testicular DNA content in spermatogenesis, and serum testosterone levels were assessed. DNA methyltransferase (Dnmts) mRNA expression and methyl-CpG binding domain sequencing were also examined to analyze DNA methylation status in the F3 generation. In the F1 generation, prenatal exposure to BDE-209 disrupted body weight, decreased anogenital distance (AGD), sperm count, and motility; and increased bent tail rates of sperm. In the F2 generation, exposure to BDE-209 decreased AGD, sperm count, normal morphology rates, Dnmt1 expression, and increased Dnmt3a expression. In the F3 generation, BDE-209 exposure decreased AGD and normal sperm morphology, disrupted testicular elongated spermatid and round spermatid rates, reduced serum testosterone levels, and inhibited the mRNA expression of Dnmt1 and Dnmt3b. Compared with the control group, there existed 215 differentially hyper-methylated and 83 hypo-methylated genes in the BDE-209 group. BDE-209 is an EDC to disrupt the male reproduction from F1 to F3. BDE-209-induced changes in sperm function and hyper- or hypo-DNA methylation in the F3 generation might therefore explain the possible mechanism underlying BDE-209-mediated epigenetic transgenerational effects on the male reproductive system.

Survivable potential of germ cells after trehalose cryopreservation of bovine testicular tissues

Germplasm preservation of livestock or endangered animals and expansion of germline stem cells are important. The purpose of this study is to investigate whether supplementation of trehalose to the freezing medium (FM) reduces tissular damage and improves the quality of testicular cells in the cryopreserved bovine testicular tissues. We herein established an optimized protocol for the cryopreservation of bovine testicular tissues, and the isolation as well as culture of bovine germ cells containing spermatogonial stem cells (SSCs) from these tissues. The results showed that FM containing 10% dimethyl sulfoxide (Me₂SO/DMSO), 10% knockout serum replacement (KSR) and 20% trehalose (FM5) combined with the uncontrolled slow freezing (USF) procedures has the optimized cryoprotective effect on bovine testicular tissues. The FM5 + USF protocol reduced the cell apoptosis, maintained high cell viability, supported the structural integrity and seminiferous epithelial cohesion similar to that in the fresh tissues. Viable germ cells containing SSCs were effectively isolated from these tissues and they maintained germline marker expressions in the co-testicular cells and co-mouse embryonic fibroblasts (MEF) feeder culture systems respectively, during the short-term culture. Additionally, upregulated transcriptions of spermatogenic differentiation marker C-KIT and meiotic marker SYCP3 were detected in these cells after retinoic acid-induced differentiation. Together, FM5 + USF is suitable for the cryopreservation of bovine testicular tissues, with benefits of reducing the apoptosis, maintaining the cell viability, supporting the testicular structure integrity, and sustaining the survival and differentiation potential of bovine germ cells containing SSCs.

Cellular Expression and Subcellular Localization of Wwox Protein During Testicular Development and Spermatogenesis in Rats

A well-known putative tumor suppressor WW domain-containing oxidoreductase (Wwox) is highly expressed in hormonally regulated tissues and is considered important for the normal development and function of reproductive organs. In this study, we investigated the cellular and subcellular localization of Wwox in normal testes during postnatal days 0-70 using Western blotting and immunohistochemistry. Wwox is expressed in testes at all ages. Immunohistochemistry showed that fetal-type and adult-type Leydig cells, immature and mature Sertoli cells, and germ cells (from gonocytes to step 17 spermatids) expressed Wwox except peritubular myoid cells, step 18-19 spermatids, and mature sperm. Wwox localized diffusely in the cytoplasm with focal intense signals in all testicular cells. These signals gradually condensed in germ cells with their differentiation and colocalized with giantin for cis-Golgi marker and partially with golgin-97 for trans-Golgi marker. Biochemically, Wwox was detected in isolated Golgi-enriched fractions. But Wwox was undetectable in the nucleus. This subcellular localization pattern of Wwox was also confirmed in single-cell suspension. These findings indicate that Wwox is functional in most cell types of testis and might locate into Golgi apparatus via interaction with Golgi proteins. These unique localizations might be related to the function of Wwox in testicular development and spermatogenesis.

S100A4+ macrophages facilitate zika virus invasion and persistence in the seminiferous tubules via interferon-gamma mediation

Testicular invasion and persistence are features of Zika virus (ZIKV), but their mechanisms are still unknown. Here, we showed that S100A4+ macrophages, a myeloid macrophage subpopulation with susceptibility to ZIKV infection, facilitated ZIKV invasion and persistence in the seminiferous tubules. In ZIKV-infected mice, S100A4+ macrophages were specifically recruited into the interstitial space of testes and differentiated into interferon-γ-expressing M1 macrophages. With interferon-γ mediation, S100A4+ macrophages down-regulated Claudin-1 expression and induced its redistribution from the cytosol to nucleus, thus increasing the permeability of the blood-testis barrier which facilitated S100A4+ macrophages invasion into the seminiferous tubules. Intraluminal S100A4+ macrophages were segregated from CD8+ T cells and consequently helped ZIKV evade cellular immunity. As a result, ZIKV continued to replicate in intraluminal S100A4+ macrophages even when the spermatogenic cells disappeared. Deficiencies in S100A4 or interferon-γ signaling both reduced ZIKV infection in the seminiferous tubules. These results demonstrated crucial roles of S100A4+ macrophages in ZIKV infection in testes.

Characterization of rodent Sertoli cell primary cultures

Sertoli cells play a vital role in spermatogenesis by offering physical and nutritional support to the differentiating male germ cells. They form the blood-testis barrier and secrete growth factors essential for germ cell differentiation. Sertoli cell primary cultures are critical for understanding the regulation of spermatogenesis; however, obtaining pure cultures has been a challenge. Rodent Sertoli cell isolation protocols do not rule out contamination by the interstitial or connective tissue cells. Sertoli cell-specific markers could be helpful, but there is no consensus. Vimentin, the most commonly used marker, is not specific for Sertoli cells since its expression has been reported in peritubular myoid cells, mesenchymal stem cells, fibroblasts, macrophages, and endothelial cells, which contaminate Sertoli cell preparations. Markers based on transcription and growth factors also have limitations. Thus, the impediment to obtaining pure Sertoli cell cultures pertains to both the method of isolation and marker usage. The aim of this review is to discuss improvements to current methods of rodent Sertoli cell primary cultures, assess the properties of prepubertal versus mature Sertoli cell cultures, and propose steps to improve cellular characterization. Potential benefits of using contemporary approaches, including lineage tracing, specific cell ablation, and RNA-seq for obtaining Sertoli-specific transcript markers are discussed. Evaluating the specificity and applicability of these markers at the protein level to characterize Sertoli cells in culture would be critical. This review is expected to positively impact future work using primary cultures of rodent Sertoli cells.

Mouse Sertoli cells isolation by lineage tracing and sorting

Sertoli cells play a key role in spermatogenesis by supporting the germ cells throughout differentiation. The isolation of Sertoli cells is essential to study their functions. However, the close contact of Sertoli cells with other testicular cell types and the high proliferation of contaminating cells are obstacles to obtain pure primary cultures. Current rodent Sertoli cell isolation protocols result in enriched, rather than pure Sertoli cells. Therefore, novel approaches are necessary to improve the purity of Sertoli cell primary cultures. The goal of this study is to obtain pure mouse Sertoli cells using lineage tracing and fluorescence-activated cell sorting (FACS). We bred the Amh-Cre mouse line with tdTomato line to generate mice constitutively expressing red fluorescence specifically in Sertoli cells. Primary cultures of Sertoli cells isolated from prepubertal mice showed that 79% of cells expressed tdTomato, as evaluated by fluorescence microscopy and flow cytometry; however, nearly all adherent cells were positive for vimentin. Most of the tomato-negative cells expressed α-smooth muscle actin (α-SMA), a peritubular myoid cell marker, but double-negative populations were also present. These findings suggest that vimentin lacks Sertoli cell-specificity and that α-SMA is not adequate to identify all of the contaminating cells. Upon FACS sorting; however, virtually 100% of the cells were tdTomato positive, expressed vimentin, but not α-SMA. Prepubertal mice yielded a higher number of Sertoli cells compared to adults, but both could be adequately sorted. In conclusion, our study shows that lineage tracing and sorting is an efficient strategy for acquiring pure populations of murine Sertoli cells.

The effects of perfluorooctanoic acid (PFOA) on fetal and adult rat testis

Perfluorooctanoic acid (PFOA) is a widely dispersed synthetic chemical, which accumulates in living organisms and has been connected with male reproductive disorders. To monitor the effects of PFOA, fetal rat testes or seminiferous tubule segments (stage VII-VIII) of adult rats were cultured in 0-100 μg/ml PFOA for 24 h. Afterwards, cAMP, progesterone, testosterone and StAR protein levels were measured from the fetal testes culture. Measurements were combined with immunohistochemistry, immunofluorescence, TUNEL and flow cytometric analysis to monitor cell death in somatic and germ cells. This study shows that the levels of cAMP, progesterone, testosterone and expression of StAR decreased significantly in PFOA 50 and 100 μg/ml. PFOA affected cell populations significantly by decreasing the amount of diploid, proliferating, meiotic I and G2/M-phase cells in adult rat testis. However, PFOA did not affect fetal, proliferating or adult rat Sertoli cells but an increased tendency of apoptosis in fetal Leydig cells was observed.

Retinoblastoma protein represses E2F3 to maintain Sertoli cell quiescence in mouse testis

Maintenance of the differentiated state and cell cycle exit in adult Sertoli cells depends on tumor suppressor retinoblastoma protein (RB, also known as RB1). We have previously shown that RB interacts with transcription factor E2F3 in the mouse testis. Here, we investigated how E2f3 contributes to adult Sertoli cell proliferation in a mouse model of Sertoli cell-specific knockout of Rb by crossing these mice with an E2f3 knockout mouse line. In the presence of intact RB, E2f3 was redundant in Sertoli cells. However, in the absence of RB, E2f3 is a key driver for cell cycle re-entry and loss of function in adult Sertoli cells. Knockout of E2f3 in Sertoli cells rescued the breakdown of Sertoli cell function associated with Rb loss, prevented proliferation of adult Sertoli cells and restored fertility of the mice. In summary, our results show that RB-mediated repression of E2F3 is critical for the maintenance of cell cycle exit and terminal differentiation in adult mouse Sertoli cells.

Genotypic and Phenotypic Variables Affect Meiotic Cell Cycle Progression, Tumor Ploidy, and Cancer-Associated Mortality in a brca2-Mutant Zebrafish Model

Successful cell replication requires both cell cycle completion and accurate chromosomal segregation. The tumor suppressor BRCA2 is positioned to influence both of these outcomes, and thereby influence genomic integrity, during meiotic and mitotic cell cycles. Accordingly, mutations in BRCA2 induce chromosomal abnormalities and disrupt cell cycle progression in both germ cells and somatic cells. Despite these findings, aneuploidy is not more prevalent in BRCA2-associated versus non-BRCA2-associated human cancers. More puzzlingly, diploidy in BRCA2-associated cancers is a negative prognostic factor, unlike non-BRCA2-associated cancers and many other human cancers. We used a brca2-mutant/tp53-mutant cancer-prone zebrafish model to explore the impact of BRCA2 mutation on cell cycle progression, ploidy, and cancer-associated mortality by performing DNA content/cell cycle analysis on zebrafish germ cells, somatic cells, and cancer cells. First, we determined that combined brca2/tp53 mutations uniquely disrupt meiotic progression. Second, we determined that sex significantly influences ploidy outcome in zebrafish cancers. Third, we determined that brca2 mutation and female sex each significantly reduce survival time in cancer-bearing zebrafish. Finally, we provide evidence to support a link between BRCA2 mutation, tumor diploidy, and poor survival outcome. These outcomes underscore the utility of this model for studying BRCA2-associated genomic aberrations in normal and cancer cells.

The intramembrane protease SPPL2c promotes male germ cell development by cleaving phospholamban

Signal peptide peptidase (SPP) and the four homologous SPP-like (SPPL) proteases constitute a family of intramembrane aspartyl proteases with selectivity for type II-oriented transmembrane segments. Here, we analyse the physiological function of the orphan protease SPPL2c, previously considered to represent a non-expressed pseudogene. We demonstrate proteolytic activity of SPPL2c towards selected tail-anchored proteins. Despite shared ER localisation, SPPL2c and SPP exhibit distinct, though partially overlapping substrate spectra and inhibitory profiles, and are organised in different high molecular weight complexes. Interestingly, SPPL2c is specifically expressed in murine and human testis where it is primarily localised in spermatids. In mice, SPPL2c deficiency leads to a partial loss of elongated spermatids and reduced motility of mature spermatozoa, but preserved fertility. However, matings of male and female SPPL2c ^-/- mice exhibit reduced litter sizes. Using proteomics we identify the sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA2)-regulating protein phospholamban (PLN) as a physiological SPPL2c substrate. Accumulation of PLN correlates with a decrease in intracellular Ca²⁺ levels in elongated spermatids that likely contribute to the compromised male germ cell differentiation and function of SPPL2c ^-/- mice.

Single-cell RNA sequencing of adult mouse testes

Spermatogenesis is an efficient and complex system of continuous cell differentiation. Previous studies investigating the transcriptomes of different cell populations in the testis relied either on sorting cells, cell depletion, or juvenile animals where not all stages of spermatogenesis have been completed. We present single-cell RNA sequencing (scRNA-Seq) data of 2,500 cells from the testes of two 8-week-old C57Bl/6J mice. Our dataset includes all spermatogenic stages from preleptotene to condensing spermatids as well as individual spermatogonia, Sertoli and Leydig cells. The data capture the full continuity of the meiotic and postmeiotic stages of spermatogenesis, and is thus ideally suited for marker discovery, network inference and similar analyses for which temporal ordering of differentiation processes can be exploited. Furthermore, it can serve as a reference for future studies involving single-cell RNA-Seq in mice where spermatogenesis is perturbed.

Characterization of germ cell differentiation in the male mouse through single-cell RNA sequencing

Spermatogenesis in the mouse has been extensively studied for decades. Previous methods, such as histological staining or bulk transcriptome analysis, either lacked resolution at the single-cell level or were focused on a very narrowly defined set of factors. Here, we present the first comprehensive, unbiased single-cell transcriptomic view of mouse spermatogenesis. Our single-cell RNA-seq (scRNA-seq) data on over 2,500 cells from the mouse testis improves upon stage marker detection and validation, capturing the continuity of differentiation rather than artificially chosen stages. scRNA-seq also enables the analysis of rare cell populations masked in bulk sequencing data and reveals new insights into the regulation of sex chromosomes during spermatogenesis. Our data provide the basis for further studies in the field, for the first time providing a high-resolution reference of transcriptional processes during mouse spermatogenesis.

Hydroxysteroid (17β) dehydrogenase 1 expressed by Sertoli cells contributes to steroid synthesis and is required for male fertility

The pituitary gonadotrophins and testosterone are the main hormonal regulators of spermatogenesis, but estradiol is also known to play a role in the process. The hormonal responses in the testis are partially mediated by somatic Sertoli cells that provide nutritional and physical support for differentiating male germ cells. Hydroxysteroid (17β) dehydrogenase 1 (HSD17B1) is a steroidogenic enzyme that especially catalyzes the conversion of low potent 17keto-steroids to highly potent 17β-hydroxysteroids. In this study, we show that Hsd17b1 is highly expressed in Sertoli cells of fetal and newborn mice, and HSD17B1 knockout males present with disrupted spermatogenesis with major defects, particularly in the head shape of elongating spermatids. The cell-cell junctions between Sertoli cells and germ cells were disrupted in the HSD17B1 knockout mice. This resulted in complications in the orientation of elongating spermatids in the seminiferous epithelium, reduced sperm production, and morphologically abnormal spermatozoa. We also showed that the Sertoli cell-expressed HSD17B1 participates in testicular steroid synthesis, evidenced by a compensatory up-regulation of HSD17B3 in Leydig cells. These results revealed a novel role for HSD17B1 in the control of spermatogenesis and male fertility, and that Sertoli cells significantly contribute to steroid synthesis in the testis.-Hakkarainen, J., Zhang, F.-P., Jokela, H., Mayerhofer, A., Behr, R., Cisneros-Montalvo, S., Nurmio, M., Toppari, J., Ohlsson, C., Kotaja, N., Sipilä, P., Poutanen, M. Hydroxysteroid (17β) dehydrogenase 1 expressed by Sertoli cells contributes to steroid synthesis and is required for male fertility.

Fertility preservation issues in pediatric hematopoietic stem cell transplantation: practical approaches from the consensus of the Pediatric Diseases Working Party of the EBMT and the International BFM Study Group

Fertility preservation is an urgent challenge in the transplant setting. A panel of transplanters and fertility specialists within the Pediatric Diseases Working Party of the European Society for Blood and Marrow Transplantation (EBMT) and the International BFM Study Group provides specific guidelines. Patients and families should be informed of possible gender- and age-specific cryopreservation strategies that should be tailored according to the underlying disease, clinical condition and previous exposure to chemotherapy. Semen collection should be routinely offered to all postpubertal boys at the diagnosis of any disease requiring therapy that could potentially impair fertility. Testicular tissue collection might be offered to postpubertal boys; nevertheless, its use has been unsuccessful to date. Oocyte collection after hormonal hyperstimulation should be offered to postpubertal girls facing gonadotoxic therapies that could be delayed for the 2 weeks required for the procedure. Ovarian tissue collection could be offered to pre-/post-pubertal girls. Pregnancies have been reported after postpubertal ovarian tissue reimplantation; however, to date, no pregnancy has been reported after the reimplantation of prepubertal ovarian tissue or in vitro maturation of pre-/post-pubertal ovarian tissue. Possible future advances in reproductive medicine could change this scenario. Health authorities should prioritize fertility preservation projects in pediatric transplantation to improve patient care and quality of life.

Knock-Out Serum Replacement and Melatonin Effects on Germ Cell Differentiation in Murine Testicular Explant Cultures

Finding robust culture conditions for in vitro maturation (IVM) of male germ cells is still a challenge. Recently, a testis organ culture method, using Knockout Serum Replacement (KSR), was suggested as a promising approach. However, the efficiency of that model is still not optimal. Hence, we have tried to establish the culture conditions in two laboratories, and to improve the reliability of the culture system to generate mature germ cells. Male mice at three days of age were sacrificed. Testes were cut into small pieces which were cultured atop agarose stands, using Minimum Essential Medium alpha supplemented with different supplements; melatonin, Glutamax, and different concentrations of KSR. The results showed that the duration of culture beyond 18 days had an impact on the number of differentiated germ cells. Supplementation with melatonin and Glutamax revealed a positive influence on the efficiency of male germ cell differentiation in vitro. Furthermore, the results confirmed that KSR had a positive effect on germ cell maturation and testosterone production, with a concentration of at least 10%. In conclusion, this study emphasizes the beneficial role of at least 10% KSR in the IVM of germ cells.

E2F1 controls germ cell apoptosis during the first wave of spermatogenesis

Cell cycle control during spermatogenesis is a highly complex process owing to the control of the mitotic expansion of the spermatogonial cell population and following meiosis, induction of DNA breaks during meiosis and the high levels of physiological germ-cell apoptosis. We set out to study how E2F1, a key controller of cell cycle, apoptosis, and DNA damage responses, functions in the developing and adult testis. We first analyzed the expression pattern of E2f1 during post-natal testis development using RNA in situ hybridization, which showed a differential expression pattern of E2f1 in the adult and juvenile mouse testes. To study the function of E2f1, we took advantage of the E2F1(-/-) mouse line, which was back-crossed to C57Bl/6J genetic background. E2f1 loss led to a severe progressive testicular atrophy beginning at the age of 20 days. Spermatogonial apoptosis during the first wave of spermatogenesis was decreased. However, already in the first wave of spermatogenesis an extensive apoptosis of spermatocytes was observed. In the adult E2F1(-/-) testes, the atrophy due to loss of spermatocytes was further exacerbated by loss of spermatogonial stem cells. Surprisingly, only subtle changes in global gene expression array profiling were observed in E2F1(-/-) testis at PND20. To dissect the changes in each testicular cell type, an additional comparative analysis of the array data was performed making use of previously published data on transcriptomes of the individual testicular cell types. Taken together, our data indicate that E2F1 has a differential role during first wave of spermatogenesis and in the adult testis, which emphasizes the complex nature of cell cycle control in the developing testis.