Cyp11a2 Is Essential for Oocyte Development and Spermatogonial Stem Cell Differentiation in Zebrafish

Cytochrome P45011A1, encoded by Cyp11a1, converts cholesterol to pregnenolone (P5), the first and rate-limiting step in steroidogenesis. In zebrafish, cyp11a1 is maternally expressed and cyp11a2 is considered the ortholog of Cyp11a1 in mammals. A recent study has shown that depletion of cyp11a2 resulted in steroidogenic deficiencies and the mutants developed into males with feminized secondary sexual characteristics. Here, we independently generated cyp11a2 mutants in zebrafish and showed that the mutants can develop into males and females in the juvenile stage, but finally into infertile males with defective mating behavior in the adult stage. In the developing ovaries, the cyp11a2 mutation led to stage I oocyte apoptosis and final sex reversal, which could be partially rescued by treatment with P5 but not estradiol. In the developing testes, depletion of cyp11a2 resulted in dysfunction of Sertoli cells and lack of functional Leydig cells. Spermatogonial stem cells (SSCs) in the mutant testes underwent active self-renewal but no differentiation, resulting in a high abundance of SSCs in the testis, as revealed by immunofluorescence staining with Nanos2 antibody. The high abundance and differentiation competence of SSCs in the mutant testes were verified by a novel testicular cell transplantation method developed in this study, by transplanting mutant testicular cells into germline-depleted wild-type (WT) fish. The transplanted mutant SSCs efficiently differentiated into functional spermatids in WT hosts. Overall, our study demonstrates the functional importance of cyp11a2 in early oogenesis and differentiation of SSCs.

chinmo-mutant spermatogonial stem cells cause mitotic drive by evicting non-mutant neighbors from the niche

Niches maintain a finite pool of stem cells via restricted space and short-range signals. Stem cells compete for limited niche resources, but the mechanisms regulating competition are poorly understood. Using the Drosophila testis model, we show that germline stem cells (GSCs) lacking the transcription factor Chinmo gain a competitive advantage for niche access. Surprisingly, chinmo-/- GSCs rely on a new mechanism of competition in which they secrete the extracellular matrix protein Perlecan to selectively evict non-mutant GSCs and then upregulate Perlecan-binding proteins to remain in the altered niche. Over time, the GSC pool can be entirely replaced with chinmo-/- cells. As a consequence, the mutant chinmo allele acts as a gene drive element; the majority of offspring inherit the allele despite the heterozygous genotype of the parent. Our results suggest that the influence of GSC competition may extend beyond individual stem cell niche dynamics to population-level allelic drift and evolution.

miR-301a-5p Regulates TGFB2 during Chicken Spermatogenesis

The process of spermatogenesis is complex and systemic, requiring the cooperation of many regulators. However, little is known about how micro RNAs (miRNAs) regulate spermatogenesis in poultry. In this study, we investigated key miRNAs and their target genes that are involved in spermatogenesis in chickens. Next-generation sequencing was conducted to determine miRNA expression profiles in five cell types: primordial germ cells (PGCs), spermatogonial stem cells (SSCs), spermatogonia (Spa), and chicken sperm. Next, we analyzed and identified several key miRNAs that regulate spermatogenesis in the four germline cell miRNA profiles. Among the enriched miRNAs, miRNA-301a-5p was the key miRNA in PGCs, SSCs, and Spa. Through reverse transcription quantitative PCR (RT-qPCR), dual-luciferase, and miRNA salience, we confirmed that miR-301a-5p binds to transforming growth factor-beta 2 (TGFβ2) and is involved in the transforming growth factor-beta (TGF-β) signaling pathway and germ cell development. To the best of our knowledge, this is the first demonstration of miR-301a-5p involvement in spermatogenesis by direct binding to TGFβ2, a key gene in the TGF-β signaling pathway. This finding contributes to the insights into the molecular mechanism through which miRNAs regulate germline cell differentiation and spermatogenesis in chickens.

A multistate stem cell dynamics maintains homeostasis in mouse spermatogenesis

In mouse testis, a heterogeneous population of undifferentiated spermatogonia (Aundiff) harbors spermatogenic stem cell (SSC) potential. Although GFRα1+ Aundiff maintains the self-renewing pool in homeostasis, the functional basis of heterogeneity and the implications for their dynamics remain unresolved. Here, through quantitative lineage tracing of SSC subpopulations, we show that an ensemble of heterogeneous states of SSCs supports homeostatic, persistent spermatogenesis. Such heterogeneity is maintained robustly through stochastic interconversion of SSCs between a renewal-biased Plvap+/GFRα1+ state and a differentiation-primed Sox3+/GFRα1+ state. In this framework, stem cell commitment occurs not directly but gradually through entry into licensed but uncommitted states. Further, Plvap+/GFRα1+ cells divide slowly, in synchrony with the seminiferous epithelial cycle, while Sox3+/GFRα1+ cells divide much faster. Such differential cell-cycle dynamics reduces mitotic load, and thereby the potential to acquire harmful de novo mutations of the self-renewing pool, while keeping the SSC density high over the testicular open niche.

Transcriptomic and epigenomic profiling of young and aged spermatogonial stem cells reveals molecular targets regulating differentiation

Spermatogonial stem cells (SSC), the foundation of spermatogenesis and male fertility, possess lifelong self-renewal activity. Aging leads to the decline in stem cell function and increased risk of paternal age-related genetic diseases. In the present study, we performed a comparative genomic analysis of mouse SSC-enriched undifferentiated spermatogonia (Oct4-GFP+/KIT-) and differentiating progenitors (Oct4-GFP+/KIT+) isolated from young and aged testes. Our transcriptome data revealed enormous complexity of expressed coding and non-coding RNAs and alternative splicing regulation during SSC differentiation. Further comparison between young and aged undifferentiated spermatogonia suggested these differentiation programs were affected by aging. We identified aberrant expression of genes associated with meiosis and TGF-β signaling, alteration in alternative splicing regulation and differential expression of specific lncRNAs such as Fendrr. Epigenetic profiling revealed reduced H3K27me3 deposition at numerous pro-differentiation genes during SSC differentiation as well as aberrant H3K27me3 distribution at genes in Wnt and TGF-β signaling upon aging. Finally, aged undifferentiated spermatogonia exhibited gene body hypomethylation, which is accompanied by an elevated 5hmC level. We believe this in-depth molecular analysis will serve as a reference for future analysis of SSC aging.

MicroRNA-30a-5p promotes differentiation in neonatal mouse spermatogonial stem cells (SSCs)

BACKGROUND

The importance of spermatogonial stem cells (SSCs) in spermatogenesis is crucial and intrinsic factors and extrinsic signals mediate fate decisions of SSCs. Among endogenous regulators, microRNAs (miRNAs) play critical role in spermatogenesis. However, the mechanisms which individual miRNAs regulate self- renewal and differentiation of SSCs are unknown. The aim of this study was to investigate effects of miRNA-30a-5p inhibitor on fate determinations of SSCs.

METHODS

SSCs were isolated from testes of neonate mice (3-6 days old) and their purities were performed by flow cytometry with ID4 and Thy1 markers. Cultured cells were transfected with miRNA- 30a-5p inhibitor. Evaluation of the proliferation (GFRA1, PLZF and ID4) and differentiation (C-Kit & STRA8) markers of SSCs were accomplished by immunocytochemistry and western blot 48 h after transfection.

RESULTS

Based on the results of flow cytometry with ID4 and Thy1 markers, percentage of purity of SSCs was about 84.3 and 97.4 % respectively. It was found that expression of differentiation markers after transfection was significantly higher in miRNA-30a- 5p inhibitor group compared to other groups. The results of proliferation markers evaluation also showed decrease of GFRA1, PLZF and ID4 protein in SSCs transfected with miRNA-30a-5p inhibitor compared to the other groups.

CONCLUSIONS

It can be concluded that inhibition of miRNA-30a-5p by overexpression of differentiation markers promotes differentiation of Spermatogonial Stem Cells.

Optimization of decellularized human placental macroporous scaffolds for spermatogonial stem cells homing

Decellularized scaffolds have been found to be excellent platforms for tissue engineering applications. The attempts are still being made to optimize a decellularization protocol with successful removal of the cells with minimal damages to extracellular matrix components. We examined twelve decellularization procedures using different concentrations of Sodium dodecyl sulfate and Triton X-100 (alone or in combination), and incubation time points of 15 or 30 min. Then, the potential of the decellularized scaffold as a three-dimensional substrate for colony formation capacity of mouse spermatogonial stem cells was determined. The morphological, degradation, biocompatibility, and swelling properties of the samples were fully characterized. The 0.5%/30 SDS/Triton showed optimal decellularization with minimal negative effects on ECM (P ≤ 0.05). The swelling ratios increased with the increase of SDS and Triton concentration and incubation time. Only 0.5%/15 and 30 SDS showed a significant decrease in the SSCs viability compared with other groups (P < 0.05). The SSCs colony formation was clearly observed under SEM and H&E stained slides. The cells infiltrated into the subcutaneously implanted scaffold at days 7 and 30 post-implantation with no sign of graft rejection. Our data suggest the %0.5/30 SDS/Triton as an excellent platform for tissue engineering and reproductive biology applications.

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.

Effect of a Freezing Medium Containing Melatonin on Markers of Pre-meiotic and Post-meiotic Spermatogonial Stem Cells (SSCs) After Transplantation in an Azoospermia Mouse Model Due to Testicular Torsion

Spermatogonial stem cells (SSCs) are essential to the initiation of spermatogenesis. Cryopreservation, long-term maintenance, and auto-transplantation of SSCs could be a new treatment for infertility. The aim of this study was to add melatonin to the basic freezing medium and to evaluate its effect on the efficiency of the thawed SSCs after transplantation into the testicles of azoospermic mice. SSCs were isolated from newborn NMRI mice, and the cells were enriched to assess morphological features. The thawed SSCs were evaluated for survival, apoptosis, and ROS level before transplantation, and the proliferation (MVH and ID4) and differentiation (c-Kit, SCP3, TP1, TP2, and Prm1) markers of SSCs were examined using immunofluorescence, western blot, and quantitative real-time polymerase chain reaction (PCR) after transplantation. It was found that the survival rate of SSCs after thawing was significantly higher in the melatonin group compared with the cryopreservation group containing basic freezing medium, and the rate of apoptosis and level of ROS production also decreased significantly in the cryopreservation group with melatonin (p < 0.05). The expression of proliferation and differentiation markers after transplantation was significantly higher in the cryopreservation group with melatonin compared to the cryopreservation group (p < 0.05). The results suggest that adding melatonin to the basic freezing medium can effectively protect the SSCs by increasing the viability and reducing the ROS production and apoptosis and improve the transplantation efficiency of SSCs after cryopreservation, which will provide a significant suggestion for fertility protection in the clinic.

Self-limiting stem-cell niche signaling through degradation of a stem-cell receptor

Stem-cell niche signaling is short-range in nature, such that only stem cells but not their differentiating progeny receive self-renewing signals. At the apical tip of the Drosophila testis, 8 to 10 germline stem cells (GSCs) surround the hub, a cluster of somatic cells that organize the stem-cell niche. We have previously shown that GSCs form microtubule-based nanotubes (MT-nanotubes) that project into the hub cells, serving as the platform for niche signal reception; this spatial arrangement ensures the reception of the niche signal specifically by stem cells but not by differentiating cells. The receptor Thickveins (Tkv) is expressed by GSCs and localizes to the surface of MT-nanotubes, where it receives the hub-derived ligand Decapentaplegic (Dpp). The fate of Tkv receptor after engaging in signaling on the MT-nanotubes has been unclear. Here we demonstrate that the Tkv receptor is internalized into hub cells from the MT-nanotube surface and subsequently degraded in the hub cell lysosomes. Perturbation of MT-nanotube formation and Tkv internalization from MT-nanotubes into hub cells both resulted in an overabundance of Tkv protein in GSCs and hyperactivation of a downstream signal, suggesting that the MT-nanotubes also serve a second purpose to dampen the niche signaling. Together, our results demonstrate that MT-nanotubes play dual roles to ensure the short-range nature of niche signaling by (1) providing an exclusive interface for the niche ligand-receptor interaction; and (2) limiting the amount of stem cell receptors available for niche signal reception.

A stem cell niche is the specialized micro-environment that provides the signal to the resident stem cells to support their undifferentiated, self-renewing state. This study shows that the cells that compose the niche do not only provide the signal, but also take up the receptor of stem cells for subsequent lysosomal degradation; this mechanism is essential for restriction of niche signal range.

Dual roles of juvenile hormone signaling during early oogenesis in Drosophila

Juvenile hormone (JH) signaling plays crucial roles in insect metamorphosis and reproduction. Function of JH signaling in germline stem cells (GSCs) remains largely unknown. Here, we found that the number of GSCs significantly declined in the ovaries of Met, Gce and JHAMT mutants. Then we inhibited JH signaling in selected cell types of ovaries by expressing Met and Gce or Kr-h1 double-stranded RNAs (dsRNAs) using different Gal4 drivers. Blocking of JH signaling in muscle cells has no effect on GSC numbers. Blocking of JH signaling in cap cells reduced GSCs cells. Inductive expression of Met and Gce dsRNA but not Kr-h1 by Nos-Gal4 increased GSC cells. These results indicate that JH signaling plays an important role in GSC maintenance.

Molecular characterization of AwSox2 from bivalve Anodonta woodiana: Elucidating its player in the immune response

Sox2 is an embryonal stem cell Ag essential for early embryonic development, tissue homeostasis and immune regulation. In the current study, one complete Sox2 cDNA sequence was cloned from freshwater bivalve Anodonta woodiana and named AwSox2. Histological changes of testis derived from Bisphenol A (BPA) treatment were analyzed by hematoxylin and eosin staining. Expressions of AwSox2 derived from BPA, LPS and polyinosinic:polycytidylic (Poly I:C) challenge were measured by quantitative real-time PCR. The full-length cDNA of AwSox2 contained an open reading frame of 927 nucleotides bearing the typical structural features of Sox2 family. Obvious degeneration, irregular arrangement of spermatids, and clotted dead and intertwined spermatids were observed in BPA-treated groups. Administration of BPA could result in a dose-dependent up-regulation of AwSox2 expression in the male gonadal tissue of A. woodiana. In addition, expression of AwSox2 was significantly induced by LPS and Poly I:C treatment in the hepatopancreas, gill and hemocytes, compared with that of control group. These results indicated that up-regulations of AwSOx2 are closely related to apoptosis of spermatogonial stem cells derived from BPA treatment as well as enhancement of immune defense against LPS and Poly I:C challenge in A. woodiana.

AMPK regulates germline stem cell quiescence and integrity through an endogenous small RNA pathway

During suboptimal growth conditions, Caenorhabditis elegans larvae undergo a global developmental arrest called “dauer.” During this stage, the germline stem cells (GSCs) become quiescent in an AMP-activated Protein Kinase (AMPK)-dependent manner, and in the absence of AMPK, the GSCs overproliferate and lose their reproductive capacity, leading to sterility when mutant animals resume normal growth. These defects correlate with the altered abundance and distribution of a number of chromatin modifications, all of which can be corrected by disabling components of the endogenous small RNA pathway, suggesting that AMPK regulates germ cell integrity by targeting an RNA interference (RNAi)-like pathway during dauer. The expression of AMPK in somatic cells restores all the germline defects, potentially through the transmission of small RNAs. Our findings place AMPK at a pivotal position linking energy stress detected in the soma to a consequent endogenous small RNA–mediated adaptation in germline gene expression, thereby challenging the “permeability" of the Weismann barrier.

When energy stress triggers dauer formation in nematodes, the cellular energy sensor AMPK genetically interacts with a small RNA pathway to mediate appropriate chromatin modifications and gene expression to regulate germline stem cell quiescence and integrity.

Functional robustness of adult spermatogonial stem cells after induction of hyperactive Hras

Accumulating evidence indicates that paternal age correlates with disease risk in children. De novo gain-of-function mutations in the FGF-RAS-MAPK signaling pathway are known to cause a subset of genetic diseases associated with advanced paternal age, such as Apert syndrome, achondroplasia, Noonan syndrome, and Costello syndrome. It has been hypothesized that adult spermatogonial stem cells with pathogenic mutations are clonally expanded over time and propagate the mutations to offspring. However, no model system exists to interrogate mammalian germline stem cell competition in vivo. In this study, we created a lineage tracing system, which enabled undifferentiated spermatogonia with endogenous expression of Hras^G12V, a known pathogenic gain-of-function mutation in RAS-MAPK signaling, to compete with their wild-type counterparts in the mouse testis. Over a year of fate analysis, neither Hras^G12V-positive germ cells nor sperm exhibited a significant expansion compared to wild-type neighbors. Short-term stem cell capacity as measured by transplantation analysis was also comparable between wild-type and mutant groups. Furthermore, although constitutively active HRAS was detectable in the mutant cell lines, they did not exhibit a proliferative advantage or an enhanced response to agonist-evoked pERK signaling. These in vivo and in vitro results suggest that mouse spermatogonial stem cells are functionally resistant to a heterozygous Hras^G12V mutation in the endogenous locus and that mechanisms could exist to prevent such harmful mutations from being expanded and transmitted to the next generation.

Recent research has found that advanced paternal age is associated with increased risk in children to develop a subset of congenital anomalies, such as Apert syndrome, achondroplasia, Noonan syndrome, and Costello syndrome. The causative genetic errors (mutations) in these disorders have been identified to originate from the fathers’ testicles and their numbers increase with fathers’ age. It has been hypothesized that the germline stem cells that continuously self-renew and differentiate to supply sperm (referred as spermatogonial stem cells [SSCs]) carry these mutations and have the ability to expand preferentially as compared to normal SSCs with advancing age of the father, thereby increasing the likelihood of transmission of mutant sperm to the next generation. To test this hypothesis, we created a mouse model, in which a mutation known to enhance cell proliferation is induced in a subset of SSCs, and these cells compete with the neighboring normal (i.e., wild-type) stem cells. However, surprisingly, the germline cell population carrying the mutation in the testis was stable over a year of observation, suggesting that mechanisms could exist to prevent such harmful mutations from being expanded and transmitted to the next generation.

YAP/Yorkie in the germline modulates the age-related decline of germline stem cells and niche cells

The properties and behaviour of stem cells rely heavily on signaling from the local microenvironment. At the apical end of Drosophila testis, self-renewal and differentiation of germline stem cells (GSCs) are tightly controlled by distinct somatic cells that comprise a specialised stem cell niche known as the hub. The hub maintains GSC homeostasis through adhesion and cell signaling. The Salvador/Warts/Hippo (SWH) pathway, which suppresses the transcriptional co-activator YAP/Yki via a kinase cascade, is a known regulator of stem cell proliferation and differentiation. Here, we show that increasing YAP/Yki expression in the germline, as well as reducing Warts levels, blocks the decrease of GSC numbers observed in aging flies, with only a small increase on their proliferation. An increased expression of YAP/Yki in the germline or a reduction in Warts levels also stymies an age-related reduction in hub cell number, suggesting a bilateral relationship between GSCs and the hub. Conversely, RNAi-based knockdown of YAP/Yki in the germline leads to a significant drop in hub cell number, further suggesting the existence of such a SC-to-niche relationship. All together, our data implicate the SWH pathway in Drosophila GSC maintenance and raise questions about its role in stem cell homeostasis in aging organisms.

Dynamic transcriptome profiles within spermatogonial and spermatocyte populations during postnatal testis maturation revealed by single-cell sequencing

Spermatogenesis is the process by which male gametes are formed from a self-renewing population of spermatogonial stem cells (SSCs) residing in the testis. SSCs represent less than 1% of the total testicular cell population in adults, but must achieve a stable balance between self-renewal and differentiation. Once differentiation has occurred, the newly formed and highly proliferative spermatogonia must then enter the meiotic program in which DNA content is doubled, then halved twice to create haploid gametes. While much is known about the critical cellular processes that take place during the specialized cell division that is meiosis, much less is known about how the spermatocytes in the "first-wave" in juveniles compare to those that contribute to long-term, "steady-state" spermatogenesis in adults. Given the strictly-defined developmental process of spermatogenesis, this study explored the transcriptional profiles of developmental cell stages during testis maturation. Using a combination of comprehensive germ cell sampling with high-resolution, single-cell-mRNA-sequencing, we have generated a reference dataset of germ cell gene expression. We show that discrete developmental stages of spermatogenesis possess significant differences in the transcriptional profiles from neonates compared to juveniles and adults. Importantly, these gene expression dynamics are also reflected at the protein level in their respective cell types. We also show differential utilization of many biological pathways with age in both spermatogonia and spermatocytes, demonstrating significantly different underlying gene regulatory programs in these cell types over the course of testis development and spermatogenic waves. This dataset represents the first unbiased sampling of spermatogonia and spermatocytes during testis maturation, at high-resolution, single-cell depth. Not only does this analysis reveal previously unknown transcriptional dynamics of a highly transitional cell population, it has also begun to reveal critical differences in biological pathway utilization in developing spermatogonia and spermatocytes, including response to DNA damage and double-strand breaks.

Initial germ cell to somatic cell ratio impacts the efficiency of SSC expansion in vitro

Spermatogonial Stem Cell (SSC) expansion in vitro remains a major challenge in efforts to preserve fertility among pubertal cancer survivor boys. The current study focused on innovative approaches to optimize SSC expansion. Six- to eight-week-old CD-1 murine testicular samples were harvested by mechanical and enzymatic digestion. Cell suspensions were incubated for differential plating (DP). After DP, we established two experiments comparing single vs. repetitive DP (S-DP and R-DP, respectively) until passage 2 (P2) completion. Each experiment included a set of cultures consisting of 5 floating-to-attached cell ratios (5, 10, 15, 20, and 25) and control cultures containing floating cells only. We found similar cell and colony count drops during P0 in both S- and R-DP. During P2, counts increased in S-DP in middle ratios (10, 15, and especially 20) relative to low and high ratios (5 and 25, respectively). Counts dropped extensively in R-DP after passage 2. The superiority of intermediate ratios was demonstrated by enrichment of GFRα1 by qPCR. The optimal ratio of 20 in S-DP contained significantly increased proportions of GFRα1-positive cells (25.8±5.8%) as measured by flow cytometry compared to after DP (1.9±0.7%, p<0.0001), as well as positive immunostaining for GFRα1 and UTF1, with rare Sox9-positive cells. This is the first report of the impact of initial floating-to-attached cell ratios on SSC proliferation in vitro.

ABBREVIATIONS

SSC: spermatogonial stem cells; DP: differential plating; NOA: non-obstructive azoospermia; MACS: magnetic-activated cells sorting; FACS: fluorescence-activated cells sorting.

EvoRegen in animals: Time to uncover deep conservation or convergence of adult stem cell evolution and regenerative processes

How do animals regenerate specialised tissues or their entire body after a traumatic injury, how has this ability evolved and what are the genetic and cellular components underpinning this remarkable feat? While some progress has been made in understanding mechanisms, relatively little is known about the evolution of regenerative ability. Which elements of regeneration are due to lineage specific evolutionary novelties or have deeply conserved roots within the Metazoa remains an open question. The renaissance in regeneration research, fuelled by the development of modern functional and comparative genomics, now enable us to gain a detailed understanding of both the mechanisms and evolutionary forces underpinning regeneration in diverse animal phyla. Here we review existing and emerging model systems, with the focus on invertebrates, for studying regeneration. We summarize findings across these taxa that tell us something about the evolution of adult stem cell types that fuel regeneration and the growing evidence that many highly regenerative animals harbor adult stem cells with a gene expression profile that overlaps with germline stem cells. We propose a framework in which regenerative ability broadly evolves through changes in the extent to which stem cells generated through embryogenesis are maintained into the adult life history.

Polycomb Group Gene E(z) Is Required for Spermatogonial Dedifferentiation in Drosophila Adult Testis

Dedifferentiation is an important process to replenish lost stem cells during aging or regeneration after injury to maintain tissue homeostasis. Here, we report that Enhancer of Zeste [E(z)], a component of the Polycomb repression complex 2 (PRC2), is required to maintain a stable pool of germline stem cells (GSCs) within the niche microenvironment. During aging, germ cells with reduced E(z) activity cannot meet that requirement, but the defect arises from neither increased GSC death nor premature differentiation. Instead, we found evidence that the decrease of GSCs upon the inactivation of E(z) in the germline could be attributed to defective dedifferentiation. During recovery from genetically manipulated GSC depletion, E(z) knockdown germ cells also fail to replenish lost GSCs. Taken together, our data suggest that E(z) acts intrinsically in germ cells to activate dedifferentiation and thus replenish lost GSCs during both aging and tissue regeneration.

Optimal culture conditions are critical for efficient expansion of human testicular somatic and germ cells in vitro

OBJECTIVE

To optimize culture conditions for human testicular somatic cells (TSCs) and spermatogonial stem cells.

DESIGN

Basic science study.

SETTING

Urology clinic and stem cell research laboratory.

PATIENT(S)

Eight human testicular samples.

INTERVENTIONS(S)

Testicular tissues were processed by mechanical and enzymatic digestion. Cell suspensions were subjected to differential plating (DP) after which floating cells (representing germ cells) were removed and attached cells (representing TSCs) were cultured for 2 passages (P0-P1) in StemPro-34- or DMEM-F12-based medium. Germ cell cultures were established in both media for 12 days.

MAIN OUTCOME MEASURE(S)

TSC cultures: proliferation doubling time (PDT), fluorescence-activated cell sorting for CD90, next-generation sequencing for 89 RNA transcripts, immunocytochemistry for TSC and germ cell markers, and conditioned media analysis; germ cell cultures: number of aggregates.

RESULT(S)

TSCs had significantly prolonged PDT in DMEM-F12 versus StemPro-34 (319.6 ± 275.8 h and 110.5 ± 68.3 h, respectively). The proportion of CD90-positive cells increased after P1 in StemPro-34 and DMEM-F12 (90.1 ± 10.8% and 76.5 ± 17.4%, respectively) versus after DP (66.3 ± 7%). Samples from both media after P1 clustered closely in the principle components analysis map whereas those after DP did not. After P1 in either medium, CD90-positive cells expressed TSC markers only, and fibroblast growth factor 2 and bone morphogenetic protein 4 were detected in conditioned medium. A higher number of germ cell aggregates formed in DMEM-F12 (59 ± 39 vs. 28 ± 17, respectively).

CONCLUSION(S)

Use of DMEM-F12 reduces TSC proliferation while preserving their unique characteristics, leading to improved germ cell aggregates formation compared with StemPro-34, the standard basal medium used in the majority of previous reports.

Culture and Expansion of Primary Undifferentiated Spermatogonial Stem Cells

This protocol describes a culture method for supporting the maintenance and expansion of a primary mouse undifferentiated spermatogonial population containing spermatogonial stem cells (SSCs). The doubling time for SSCs in culture is relatively slow. Once established, SSC lines are split 1:2 to 1:4 every 7 d. Therefore, the time required to generate sufficient SSCs for experimentation can be considerable and requires careful planning.

Isolation of the Spermatogonial Stem Cell-Containing Fraction from Testes

A testis cell fraction enriched for spermatogonial stem cells (SSCs) compared with the unfractionated total testis cell population can be isolated from testes after birth and adult stages. This protocol involves dissociating the seminiferous tubules into a single-cell suspension, using enzymes and mechanical disruption. This is followed by the selection of the Thy1⁺ cell fraction that contains nearly the entire SSC population and is enriched for these cells compared with the total testis cell population. This isolated fraction can be used for molecular studies, transfer into culture to establish primary cultures, or transplantation into the testes of recipients for spermatogenesis. Typically, if the SSCs are destined for transplantation, a marker is included to visualize the clones of spermatogenesis (e.g., lacZ or green fluorescent protein [GFP] transgenes). It is important to note that the isolated Thy1⁺ cell fraction does not consist of pure SSCs and that most germ cells are non-stem-cell progenitors, and a smaller portion of the population is somatic cells.

Tissue Sources for Accurate Measurement of Germline DNA Genotypes in Prostate Cancer Patients Treated With Radical Prostatectomy

BACKGROUND

Benign tissue from a tumor-containing organ is commonly the only available source for obtaining a patient's unmutated genome for use in cancer research. While it is critical to identify histologically normal tissue that is independent of the tumor lineage, few additional considerations are applied to the choice of this material for such measurements.

METHODS

Normal formalin-fixed, paraffin-embedded seminal vesicle, and urethral tissues, in addition to whole blood, were collected from 31 prostate cancer patients having undergone radical prostatectomy. Genotype concordance was evaluated for DNA from each tissue source in relation to whole blood.

RESULTS

Overall, there was a greater genotype call rate for DNA derived from urethral tissue (97.0%) in comparison with patient-matched seminal vesicle tissues (95.9%, P = 0.0015). Furthermore, with reference to patient-matched whole blood, urethral samples exhibited higher genotype concordance (94.1%) than that of seminal vesicle samples (92.5%, P = 0.035).

CONCLUSIONS

These findings highlight the heterogeneity between diverse sources of DNA in genotype measurement and motivate the consideration of normal tissue biases in tumor-normal analyses. Prostate 77: 425-434, 2017. © 2016 Wiley Periodicals, Inc.