Generation of functional multipotent adult stem cells from GPR125+ germline progenitors

Epigenetic inheritance of acquired traits via stem cells dedifferentiation/differentiation or transdifferentiation cycles

Inheritance of acquired characteristics is the once widely accepted idea that multiple modifications acquired by an organism during its life, can be inherited by the offspring. This belief is at least as old as Hippocrates and became popular in early 19th century, leading Lamarck to suggest his theory of evolution. Charles Darwin, along with other thinkers of the time attempted to explain the mechanism of acquired traits' inheritance by proposing the theory of pangenesis. While later this and similar theories were rejected because of the lack of hard evidence, the studies aimed at revealing the mechanism by which somatic information can be passed to germ cells have continued up to the present. In this paper, we present a new theory and provide supporting literature to explain this phenomenon. We hypothesize existence of pluripotent adult stem cells that can serve as collectors and carriers of new epigenetic traits by entering different developmentally active organ/tissue compartments through blood circulation and acquiring new epigenetic marks though cycles of differentiation/dedifferentiation or transdifferentiation. During gametogenesis, these epigenetically modified cells are attracted by gonads, transdifferentiate into germ cells, and pass the acquired epigenetic modifications collected from the entire body's somatic cells to the offspring.

Stage-specific regulation of undifferentiated spermatogonia by AKT1S1-mediated AKT-mTORC1 signaling during mouse spermatogenesis

Undifferentiated spermatogonia are composed of a heterogeneous cell population including spermatogonial stem cells (SSCs). Molecular mechanisms underlying the regulation of various spermatogonial cohorts during their self-renewal and differentiation are largely unclear. Here we show that AKT1S1, an AKT substrate and inhibitor of mTORC1, regulates the homeostasis of undifferentiated spermatogonia. Although deletion of Akt1s1 in mouse appears not grossly affecting steady-state spermatogenesis and male mice are fertile, the subset of differentiation-primed OCT4+ spermatogonia decreased significantly, whereas self-renewing GFRα1+ and proliferating PLZF+ spermatogonia were sustained. Both neonatal prospermatogonia and the first wave spermatogenesis were greatly reduced in Akt1s1-/- mice. Further analyses suggest that OCT4+ spermatogonia in Akt1s1-/- mice possess altered PI3K/AKT-mTORC1 signaling, gene expression and carbohydrate metabolism, leading to their functionally compromised developmental potential. Collectively, these results revealed an important role of AKT1S1 in mediating the stage-specific signals that regulate the self-renewal and differentiation of spermatogonia during mouse spermatogenesis.

High incidence of imperforate vagina in ADGRA3-deficient mice

BACKGROUND

Ten percent of the female population suffers from congenital abnormalities of the vagina, uterus, or oviducts, with severe consequences for reproductive and psychological health. Yet, the underlying causes of most of these malformations remain largely unknown. ADGRA3 (GPR125) is involved in WNT signaling and planar cell polarity, mechanisms vital to female reproductive tract development. Although ADGRA3 is a well-established spermatogonial stem cell marker, its role within the female urogenital system remains unclear.

RESULTS

In this study, we found Adgra3 to be expressed throughout the murine female urogenital system, with higher expression pre-puberty than after sexual maturation. We generated a global Adgra3-/- mouse line and observed imperforate vagina in 44% of Adgra3-/- females, resulting in distension of the reproductive tract and infertility. Ovarian morphology, plasma estradiol, ovarian Cyp19a1, and vaginal estrogen receptor α (Esr1) expression were unaffected. However, compared to controls, a significantly lower bone mineral density was found in Adgra3-/- mice. Whereas vaginal opening in mice is an estrogen-dependent process, 17β-estradiol treatment failed to induce vaginal canalization in Adgra3-/- mice. Furthermore, a marked reduction in vaginal and ovarian progesterone receptor expression was observed concomitant with an upregulation of apoptotic regulators Bcl2, Bid, and Bmf in adult Adgra3-/- females with a closed vagina.

CONCLUSIONS

Our collective results shed new insights into the complex mechanisms by which the adhesion receptor ADGRA3 regulates distal vaginal tissue remodeling during vaginal canalization via altered sex hormone responsiveness and balance in apoptotic regulators. This highlights the potential of ADGRA3 as a target in diagnostic screening and/or therapy for obstructive vaginal malformations in humans.

Age-related decline in spermatogenic activity accompanied with endothelial cell senescence in male mice

Male fertility decreases with aging, with spermatogenic decline being one of its causes. Altered testis environment is suggested as a cause of the phenotype; however, the associated mechanisms remain unclear. Herein, we investigated the age-related changes in testicular somatic cells on spermatogenic activity. The number and proliferation of spermatogonia significantly reduced with aging in mice. Interestingly, senescence-associated β-galactosidase-positive cells appeared in testicular endothelial cell (EC) populations, but not in germ cell populations, with aging. Transcriptome analysis of ECs indicated that senescence occurred in the ECs of aged mice. Furthermore, the support capacity of ECs for spermatogonial proliferation significantly decreased with aging; however, the senolytic-induced removal of senescent cells from aged ECs restored their supporting capacity to a comparable level as that of young ECs. Our results suggest that the accumulation of senescent ECs in the testis is a potential factor contributing to the age-related decline in spermatogenic activity.

Spermatogonial stem-cell-derived neural-like cell transplantation enhances the functional recovery of a rat spinal cord injury model: characterization of evoked potentials

Severe spinal cord injuries (SCIs) usually result in the temporary or permanent impairment of strength, sensation or autonomic functions below the sites of injuries. To date, a large number of therapeutic approaches have been used to ameliorate SCIs, and subsequent stem cell transplantation appears to be a promising strategy. The aim of this study was to evaluate the therapeutic effect of stem cells by changes in the evoked potentials at different time points after a transplantation of spermatogonial stem cells (SSCs) to differentiate the source neurons in a rat model with SCIs, as well as through histopathology. A modified Plemel spinal cord lateral compression model was used. The experiment was divided into a blank, a control and a SSC transplantation group. Motor activity scores, sensory evoked potentials (SEPs) and motor evoked potentials (MEPs) were assessed through motor resuscitation as well as histologic evaluation on each experimental group to determine the improvement. Consistent with our results, motor scores and evoked potentials were significantly improved in the SSC transplantation group. In addition, a histologic assessment showed that the transplanted stem cells had a significant restorative effect on the reconstruction of tissue cells. 1 week after the stem cell transplantation, the SSC transplantation group showed improvement in spinal cord functions and spinal cord pathologic injuries. After 2 weeks and beyond, the SSC transplantation group showed significant improvement in spinal cord functions and spinal cord pathology compared to the control group, meanwhile the evoked potentials and motor function of the hind limbs of rats in the SSC transplantation group were significantly improved. Therefore, the therapeutic strategies for spermatogonial stem cells will be an effective program in the study on SCIs, and we suggest the somatosensory evoked potentials as a tool to assess the degree of recovery from SCIs after the transplantation of stem cells.

SPRY4-dependent ERK negative feedback demarcates functional adult stem cells in the male mouse germline†

Niche-derived growth factors support self-renewal of mouse spermatogonial stem and progenitor cells through ERK MAPK signaling and other pathways. At the same time, dysregulated growth factor-dependent signaling has been associated with loss of stem cell activity and aberrant differentiation. We hypothesized that growth factor signaling through the ERK MAPK pathway in spermatogonial stem cells is tightly regulated within a narrow range through distinct intracellular negative feedback regulators. Evaluation of candidate extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK)-responsive genes known to dampen downstream signaling revealed robust induction of specific negative feedback regulators, including Spry4, in cultured mouse spermatogonial stem cells in response to glial cell line-derived neurotrophic factor or fibroblast growth factor 2. Undifferentiated spermatogonia in vivo exhibited high levels of Spry4 mRNA. Quantitative single-cell analysis of ERK MAPK signaling in spermatogonial stem cell cultures revealed both dynamic signaling patterns in response to growth factors and disruption of such effects when Spry4 was ablated, due to dysregulation of ERK MAPK downstream of RAS. Whereas negative feedback regulator expression decreased during differentiation, loss of Spry4 shifted cell fate toward early differentiation with concomitant loss of stem cell activity. Finally, a mouse Spry4 reporter line revealed that the adult spermatogonial stem cell population in vivo is demarcated by strong Spry4 promoter activity. Collectively, our data suggest that negative feedback-dependent regulation of ERK MAPK is critical for preservation of spermatogonial stem cell fate within the mammalian testis.

OIP5 Interacts with NCK2 to Mediate Human Spermatogonial Stem Cell Self-Renewal and Apoptosis through Cell Cyclins and Cycle Progression and Its Abnormality Is Correlated with Male Infertility

Spermatogonial stem cells (SSCs) have important applications in both reproduction and regenerative medicine. Nevertheless, specific genes and signaling transduction pathways in mediating fate decisions of human SSCs remain elusive. Here, we have demonstrated for the first time that OIP5 (Opa interacting protein 5) controlled the self-renewal and apoptosis of human SSCs. RNA sequencing identified that NCK2 was a target for OIP5 in human SSCs, and interestingly, OIP5 could interact with NCK2 as shown by Co-IP (co-immunoprecipitation), IP-MS (mass spectrometry), and GST pulldown assays. NCK2 silencing decreased human SSC proliferation and DNA synthesis but enhanced their apoptosis. Notably, NCK2 knockdown reversed the influence of OIP5 overexpression on human SSCs. Moreover, OIP5 inhibition decreased the numbers of human SSCs at S and G2/M phases, while the levels of numerous cell cycle proteins, including cyclins A2, B1, D1, E1 and H, especially cyclin D1, were remarkably reduced. Significantly, whole-exome sequencing of 777 patients with nonobstructive azoospermia (NOA) revealed 54 single-nucleotide polymorphism mutations of the OIP5 gene (6.95%), while the level of OIP5 protein was obviously lower in testes of NOA patients compared to fertile men. Collectively, these results implicate that OIP5 interacts with NCK2 to modulate human SSC self-renewal and apoptosis via cell cyclins and cell cycle progression and that its mutation and/or lower expression is correlated with azoospermia. As such, this study offers novel insights into molecular mechanisms underlying the fate determinations of human SSCs and the pathogenesis of NOA, and it provides new targets for treating male infertility.

A 1-kb human CDCA8 promoter directs the spermatogonia-specific luciferase expression in adult testis

Cell division cycle associated 8 (CDCA8) is a component of the chromosomal passenger complex and plays an essential role in mitosis, meiosis, cancer growth, and undifferentiated state of embryonic stem cells. However, its expression and role in adult tissues remain largely uncharacterized. Here, we studied the CDCA8 transcription in adult tissues by generating a transgenic mouse model, in which the luciferase was driven by a 1-kb human CDCA8 promoter. Our previous study showed that this 1-kb promoter was active enough to dictate reporter expression faithfully reflecting endogenous CDCA8 expression. Two founder mice carrying the transgene were identified. In vivo imaging and luciferase assays in tissue lysates revealed that CDCA8 promoter was highly activated and drove robust luciferase expression in testes. Subsequently, immunohistochemical and immunofluorescent staining showed that in adult transgenic testes, the expression of luciferase was restricted to a subset of spermatogonia that were located along the basement membrane and positive for the expression of GFRA1, a consensus marker for early undifferentiated spermatogonia. These findings for the first time indicate that the CDCA8 was transcriptionally activated in testis and thus may play a role in adult spermatogenesis. Moreover, the 1-kb CDCA8 promoter could be used for spermatogonia-specific gene expression in vivo and the transgenic lines constructed here could also be used for recovery of spermatogonia from adult testes.

Loss of Adgra3 causes obstructive azoospermia with high penetrance in male mice

The adhesion receptor ADGRA3 (GPR125) is a known spermatogonial stem cell marker, but its impact on male reproduction and fertility has not been examined. Using a mouse model lacking Adgra3 (Adgra3-/- ), we show that 55% of the male mice are infertile from puberty despite having normal spermatogenesis and epididymal sperm count. Instead, male mice lacking Adgra3 exhibited decreased estrogen receptor alpha expression and transient dilation of the epididymis. Combined with an increased estradiol production, this indicates a post-pubertal hormonal imbalance and fluid retention. Dye injection revealed a blockage between the ejaculatory duct and the urethra, which is rare in mice suffering from infertility, thereby mimicking the etiologies of obstructive azoospermia found in human male infertility. To summarize, male reproductive tract development is dependent on ADGRA3 function that in concert with estrogen signaling may influence fluid handling during sperm maturation and storage.

Chromatin remodelers HELLS, WDHD1 and BAZ1A are dynamically expressed during mouse spermatogenesis

In brief

Proper regulation of heterochromatin is critical for spermatogenesis. This study reveals the dynamic localization patterns of distinct chromatin regulators during spermatogenesis and disrupted sex chromatin status in spermatocytes in the absence of DICER.

Abstract

Heterochromatin is dynamically formed and organized in differentiating male germ cells, and its proper regulation is a prerequisite for normal spermatogenesis. While heterochromatin is generally transcriptionally silent, we have previously shown that major satellite repeat (MSR) DNA in the pericentric heterochromatin (PCH) is transcribed during spermatogenesis. We have also shown that DICER associates with PCH and is involved in the regulation of MSR-derived transcripts. To shed light on the heterochromatin regulation in the male germline, we studied the expression, localization and heterochromatin association of selected testis-enriched chromatin regulators in the mouse testis. Our results show that HELLS, WDHD1 and BAZ1A are dynamically expressed during spermatogenesis. They display limited overlap in expression, suggesting involvement in distinct heterochromatin-associated processes at different steps of differentiation. We also show that HELLS and BAZ1A interact with DICER and MSR chromatin. Interestingly, deletion of Dicer1 affects the sex chromosome heterochromatin status in late pachytene spermatocytes, as demonstrated by mislocalization of Polycomb protein family member SCML1 to the sex body. These data substantiate the importance of dynamic heterochromatin regulation during spermatogenesis and emphasize the key role of DICER in the maintenance of chromatin status in meiotic male germ cells.

Single-cell RNA sequencing uncovers dynamic roadmap and cell-cell communication during buffalo spermatogenesis

Spermatogenesis carries the task of precise intergenerational transmission of genetic information from the paternal genome and involves complex developmental processes regulated by the testicular microenvironment. Studies performed mainly in mouse models have established the theoretical basis for spermatogenesis, yet the wide interspecies differences preclude direct translation of the findings, and farm animal studies are progressing slowly. More than 32,000 cells from prepubertal (3-month-old) and pubertal (24-month-old) buffalo testes were analyzed by using single-cell RNA sequencing (scRNA-seq), and dynamic gene expression roadmaps of germ and somatic cell development were generated. In addition to identifying the dynamic processes of sequential cell fate transitions, the global cell-cell communication essential to maintain regular spermatogenesis in the buffalo testicular microenvironment was uncovered. The findings provide the theoretical basis for establishing buffalo germline stem cells in vitro or culturing organoids and facilitating the expansion of superior livestock breeding.

The Role of Genetically Modified Human Feeder Cells in Maintaining the Integrity of Primary Cultured Human Deciduous Dental Pulp Cells

Tissue-specific stem cells exist in tissues and organs, such as skin and bone marrow. However, their pluripotency is limited compared to embryonic stem cells. Culturing primary cells on plastic tissue culture dishes can result in the loss of multipotency, because of the inability of tissue-specific stem cells to survive in feeder-less dishes. Recent findings suggest that culturing primary cells in medium containing feeder cells, particularly genetically modified feeder cells expressing growth factors, may be beneficial for their survival and proliferation. Therefore, the aim of this study was to elucidate the role of genetically modified human feeder cells expressing growth factors in maintaining the integrity of primary cultured human deciduous dental pulp cells. Feeder cells expressing leukemia inhibitory factor, bone morphogenetic protein 4, and basic fibroblast growth factor were successfully engineered, as evidenced by PCR. Co-culturing with mitomycin-C-treated feeder cells enhanced the proliferation of newly isolated human deciduous dental pulp cells, promoted their differentiation into adipocytes and neurons, and maintained their stemness properties. Our findings suggest that genetically modified human feeder cells may be used to maintain the integrity of primary cultured human deciduous dental pulp cells.

The function of Foxo1 in spermatogonia development is independent of PI3K/PTEN signaling

Spermatogenesis is a highly coordinated process that initiates shortly after birth and continues throughout the lifespan of male animals. Foxo1 is a transcription factor and is involved in many biological processes. It has been reported that the inactivation of Foxo1 in gonocytes during the embryonic stage causes the defects of spermatogenesis. In the present study, we found that the inactivation of Foxo1 in spermatogonia after birth also caused germ cell loss and male infertility. We found that the initiation of meiosis was not affected; however, the germ cell development was arrested after meiosis and lack of mature spermatozoa in the cauda epididymis. We also found that the proliferation of Foxo1-deficient spermatogonia stem cells was significantly reduced under in vitro conditions. Further study revealed that inactivation of Pten in postnatal spermatogonia using Stra8-Cre did not affect germ cell development and the subcellular location of FOXO1 in Pten-deficient spermatogonia. This study demonstrated that Foxo1 was involved in the development of spermatogonia after birth and the function of Foxo1 was probably not regulated by PI3K/PTEN signaling.

GPR125 (ADGRA3) is an autocleavable adhesion GPCR that traffics with Dlg1 to the basolateral membrane and regulates epithelial apico-basal polarity

The adhesion family of G protein–coupled receptors (GPCRs) is defined by an N-terminal large extracellular region that contains various adhesion-related domains and a highly-conserved GPCR-autoproteolysis-inducing (GAIN) domain, the latter of which is located immediately before a canonical seven-transmembrane domain. These receptors are expressed widely and involved in various functions including development, angiogenesis, synapse formation, and tumorigenesis. GPR125 (ADGRA3), an orphan adhesion GPCR, has been shown to modulate planar cell polarity in gastrulating zebrafish, but its biochemical properties and role in mammalian cells have remained largely unknown. Here, we show that human GPR125 likely undergoes cis-autoproteolysis when expressed in canine kidney epithelial MDCK cells and human embryonic kidney HEK293 cells. The cleavage appears to occur at an atypical GPCR proteolysis site within the GAIN domain during an early stage of receptor biosynthesis. The products, i.e., the N-terminal and C-terminal fragments, seem to remain associated after self-proteolysis, as observed in other adhesion GPCRs. Furthermore, in polarized MDCK cells, GPR125 is exclusively recruited to the basolateral domain of the plasma membrane. The recruitment likely requires the C-terminal PDZ-domain–binding motif of GPR125 and its interaction with the cell polarity protein Dlg1. Knockdown of GPR125 as well as that of Dlg1 results in formation of aberrant cysts with multiple lumens in Matrigel 3D culture of MDCK cells. Consistent with the multilumen phenotype, mitotic spindles are incorrectly oriented during cystogenesis in GPR125-KO MDCK cells. Thus, the basolateral protein GPR125, an autocleavable adhesion GPCR, appears to play a crucial role in apicobasal polarization in epithelial cells.

Histone methyltransferase DOT1L is essential for self-renewal of germline stem cells

Self-renewal of spermatogonial stem cells is vital to lifelong production of male gametes and thus fertility. However, the underlying mechanisms remain enigmatic. Here, we show that DOT1L, the sole H3K79 methyltransferase, is required for spermatogonial stem cell self-renewal. Mice lacking DOT1L fail to maintain spermatogonial stem cells, characterized by a sequential loss of germ cells from spermatogonia to spermatids and ultimately a Sertoli cell only syndrome. Inhibition of DOT1L reduces the stem cell activity after transplantation. DOT1L promotes expression of the fate-determining HoxC transcription factors in spermatogonial stem cells. Furthermore, H3K79me2 accumulates at HoxC9 and HoxC10 genes. Our findings identify an essential function for DOT1L in adult stem cells and provide an epigenetic paradigm for regulation of spermatogonial stem cells.

Xenotransplantation of Human Spermatogonia Into Various Mouse Recipient Models

Spermatogonial stem cells are the foundation of continuous spermatogenesis in adult mammals. Xenograft models have been established to define human SSCs, mostly using infertile and immune-deficient mice as the recipients for human germ cell transplantation. However, it is time-consuming to prepare such recipients using irradiation or chemotherapeutic agents, and this approach may also introduce confounding factors when residual endogenous germ cells recover in transplanted recipients. It remains to be determined whether immune-competent genetically infertile mice can be suitable recipients for xenotransplantation. In this study, we observed similar engraftment efficiencies when using spermatogonia from human biopsied testes across immune-deficient nude mice, immune-competent ICR mice, and genetically infertile Kit^w/w-v mice, suggesting minimal immunological rejection from immune-competent mouse recipients upon xenotransplantation of human germ cells. More importantly, we derived EpCAM negative and TNAP positive spermatogonia-like cells (SLCs) from human pluripotent stem cells (PSCs), which highly expressed spermatogonial markers including PLZF, INTERGRINα6, TKTL1, CD90, and DRMT3. We found that upon transplantation, these SLCs proliferated and colonized at the basal membrane of seminiferous tubules in testes of both immune-deficient nude mice and Kit^w/w-v mice, though complete spermatogenesis would likely require supporting human signaling factors and microenvironment. Taken together, our study functionally defined the cell identity of PSC-derived SLCs, and supported xenotransplantation using genetically infertile recipients as a convenient model for functionally evaluating spermatogonia derived from different species.

Gpr125 is a unifying hallmark of multiple mammary progenitors coupled to tumor latency

Gpr125 is an orphan G-protein coupled receptor, with homology to cell adhesion and axonal guidance factors, that is implicated in planar polarity and control of cell movements. By lineage tracing we demonstrate that Gpr125 is a highly specific marker of bipotent mammary stem cells in the embryo and of multiple long-lived unipotent basal mammary progenitors in perinatal and postnatal glands. Nipple-proximal Gpr125+ cells express a transcriptomic profile indicative of chemo-repulsion and cell movement, whereas Gpr125+ cells concentrated at invasive ductal tips display a hybrid epithelial-mesenchymal phenotype and are equipped to bind chemokine and growth factors and secrete a promigratory matrix. Gpr125 progenitors acquire bipotency in the context of transplantation and cancer and are greatly expanded and massed at the pushing margins of short latency MMTV-Wnt1 tumors. High Gpr125 expression identifies patients with particularly poor outcome within the basal breast cancer subtype highlighting its potential utility as a factor to stratify risk.

Gpr125 has emerged as a specific marker of mammary stem cells and basal progenitors. Here they show that Gpr125 cells congregate at ductal tips during morphogenesis and amass at tumor margins, and that high Gpr125 predicts early tumor onset and poor outcome in basal breast cancer.

Peptide-coating 2D and small chemical molecules prolong the passage of porcine spermatogonia stem cells

Porcine spermatogonia stem cells (pSSCs) are the only type of somatic stem cell that can pass genetic information to the successive generations. Little is known about pSSCs vitality in vitro, and due to their increasing importance in stem cell research, here, we optimized a protocol to culture pSSCs and explored their potential fate in vitro. Utilizing a feeder-free culture system with a 2D peptide-coating and small chemical molecules (including CHIR99021, Repsox, Vatamin C, Folic Acid, and CD Lipid Concentrate), we were able to prolong the culture time of pSSCs by at least three months compared to previous methods. Moreover, we found that pSSCs could proliferate and self-renew in the seminiferous tubules of infertile mice. However, they could not perform meiosis. Our study shows that this feeder-free culture system optimizes cell culture and may facilitate advanced research on SSC biology and genetic manipulation of germ cells.

Neonatal Porcine Germ Cells Dedifferentiate and Display Osteogenic and Pluripotency Properties

Gonocytes are progenitors of spermatogonial stem cells in the neonatal testis. We have previously shown that upon culturing, neonatal porcine gonocytes and their colonies express germ cell and pluripotency markers. The objectives of present study were to investigate in vitro trans-differentiation potential of porcine gonocytes and their colonies into cells from three germinal layers, and to assess pluripotency of cultured gonocytes/colonies in vivo. For osteogenic and tri-lineage differentiation, cells were incubated in regular culture media for 14 and 28 days, respectively. Cells were cultured for an additional 14 days for osteogenic differentiation or 7 days for differentiation into derivates of the three germinal layers. Osteogenic differentiation of cells and colonies was verified by Alizarin Red S staining and tri-lineage differentiation was confirmed using immunofluorescence and gene expression analyses. Furthermore, upon implantation into recipient mice, the cultured cells/colonies developed teratomas expressing markers of all three germinal layers. Successful osteogenic differentiation from porcine germ cells has important implications for bone regeneration and matrix formation studies. Hence, gonocytes emerge as a promising source of adult pluripotent stem cells due to the ability to differentiate into all germinal layers without typical biosafety risks associated with viral vectors or ethical implications.

Loss of tyrosine kinase receptor Ephb2 impairs proliferation and stem cell activity of spermatogonia in culture†

Germline stem and progenitor cells can be extracted from the adult mouse testis and maintained long-term in vitro. Yet, the optimal culture conditions for preserving stem cell activity are unknown. Recently, multiple members of the Eph receptor family were detected in murine spermatogonia, but their roles remain obscure. One such gene, Ephb2, is crucial for maintenance of somatic stem cells and was previously found enriched at the level of mRNA in murine spermatogonia. We detected Ephb2 mRNA and protein in primary adult spermatogonial cultures and hypothesized that Ephb2 plays a role in maintenance of stem cells in vitro. We employed CRISPR-Cas9 targeting and generated stable mutant SSC lines with complete loss of Ephb2. The characteristics of Ephb2-KO cells were interrogated using phenotypic and functional assays. Ephb2-KO SSCs exhibited reduced proliferation compared to wild-type cells, while apoptosis was unaffected. Therefore, we examined whether Ephb2 loss correlates with activity of canonical pathways involved in stem cell self-renewal and proliferation. Ephb2-KO cells had reduced ERK MAPK signaling. Using a lentiviral transgene, Ephb2 expression was rescued in Ephb2-KO cells, which partially restored signaling and proliferation. Transplantation analysis revealed that Ephb2-KO SSCs cultures formed significantly fewer colonies than WT, indicating a role for Ephb2 in preserving stem cell activity of cultured cells. Transcriptome analysis of wild-type and Ephb2-KO SSCs identified Dppa4 and Bnc1 as differentially expressed, Ephb2-dependent genes that are potentially involved in stem cell function. These data uncover for the first time a crucial role for Ephb2 signaling in cultured SSCs.

Gpr125 Marks Distinct Cochlear Cell Types and Is Dispensable for Cochlear Development and Hearing

The G protein-coupled receptor (GPR) family critically regulates development and homeostasis of multiple organs. As a member of the GPR adhesion family, Gpr125 (Adgra3) modulates Wnt/PCP signaling and convergent extension in developing zebrafish, but whether it is essential for cochlear development in mammals is unknown. Here, we examined the Gpr125 lacZ/+ knock-in mice and show that Gpr125 is dynamically expressed in the developing and mature cochleae. From embryonic day (E) 15.5 to postnatal day (P) 30, Gpr125-β-Gal is consistently expressed in the lesser epithelial ridge and its presumed progenies, the supporting cell subtypes Claudius cells and Hensen's cells. In contrast, Gpr125-β-Gal is expressed transiently in outer hair cells, epithelial cells in the lateral cochlear wall, interdental cells, and spiral ganglion neurons in the late embryonic and early postnatal cochlea. In situ hybridization for Gpr125 mRNA confirmed Gpr125 expression and validated loss of expression in Gpr125 lacZ/lacZ cochleae. Lastly, Gpr125 lacZ/+ and Gpr125 lacZ/ lacZ cochleae displayed no detectable loss or disorganization of either sensory or non-sensory cells in the embryonic and postnatal ages and exhibited normal auditory physiology. Together, our study reveals that Gpr125 is dynamically expressed in multiple cell types in the developing and mature cochlea and is dispensable for cochlear development and hearing.

Cellular Therapy via Spermatogonial Stem Cells for Treating Impaired Spermatogenesis, Non-Obstructive Azoospermia

Male infertility is a major health problem affecting about 8–12% of couples worldwide. Spermatogenesis starts in the early fetus and completes after puberty, passing through different stages. Male infertility can result from primary or congenital, acquired, or idiopathic causes. The absence of sperm in semen, or azoospermia, results from non-obstructive causes (pretesticular and testicular), and post-testicular obstructive causes. Several medications such as antihypertensive drugs, antidepressants, chemotherapy, and radiotherapy could lead to impaired spermatogenesis and lead to a non-obstructive azoospermia. Spermatogonial stem cells (SSCs) are the basis for spermatogenesis and fertility in men. SSCs are characterized by their capacity to maintain the self-renewal process and differentiation into spermatozoa throughout the male reproductive life and transmit genetic information to the next generation. SSCs originate from gonocytes in the postnatal testis, which originate from long-lived primordial germ cells during embryonic development. The treatment of infertility in males has a poor prognosis. However, SSCs are viewed as a promising alternative for the regeneration of the impaired or damaged spermatogenesis. SSC transplantation is a promising technique for male infertility treatment and restoration of spermatogenesis in the case of degenerative diseases such as cancer, radiotherapy, and chemotherapy. The process involves isolation of SSCs and cryopreservation from a testicular biopsy before starting cancer treatment, followed by intra-testicular stem cell transplantation. In general, treatment for male infertility, even with SSC transplantation, still has several obstacles. The efficiency of cryopreservation, exclusion of malignant cells contamination in cancer patients, and socio-cultural attitudes remain major challenges to the wider application of SSCs as alternatives. Furthermore, there are limitations in experience and knowledge regarding cryopreservation of SSCs. However, the level of infrastructure or availability of regulatory approval to process and preserve testicular tissue makes them tangible and accurate therapy options for male infertility caused by non-obstructive azoospermia, though in their infancy, at least to date.

Characterization, isolation, and culture of spermatogonial stem cells in Macaca fascicularis

Spermatogonial stem cells (SSCs) have great applications in both reproductive and regenerative medicine. Primates including monkeys are very similar to humans with regard to physiology and pathology. Nevertheless, little is known about the isolation, the characteristics, and the culture of primate SSCs. This study was designed to identify, isolate, and culture monkey SSCs. Immunocytochemistry was used to identify markers for monkey SSCs. Glial cell line-derived neurotrophic factor family receptor alpha-1 (GFRA1)-enriched spermatogonia were isolated from monkeys, namely Macaca fascicularis (M. fascicularis), by two-step enzymatic digestion and magnetic-activated cell sorting, and they were cultured on precoated plates in the conditioned medium. Reverse transcription-polymerase chain reaction (RT-PCR), immunocytochemistry, and RNA sequencing were used to compare phenotype and transcriptomes in GFRA1-enriched spermatogonia between 0 day and 14 days of culture, and xenotransplantation was performed to evaluate the function of GFRA1-enriched spermatogonia. SSCs shared some phenotypes with rodent and human SSCs. GFRA1-enriched spermatogonia with high purity and viability were isolated from M. fascicularis testes. The freshly isolated cells expressed numerous markers for rodent SSCs, and they were cultured for 14 days. The expression of numerous SSC markers was maintained during the cultivation of GFRA1-enriched spermatogonia. RNA sequencing reflected a 97.3% similarity in global gene profiles between 0 day and 14 days of culture. The xenotransplantation assay indicated that the GFRA1-enriched spermatogonia formed colonies and proliferated in vivo in the recipient c-KitW/W (W) mutant mice. Collectively, GFRA1-enriched spermatogonia are monkey SSCs phenotypically both in vitro and in vivo. This study suggests that monkey might provide an alternative to human SSCs for basic research and application in human diseases.

Step by Step about Germ Cells Development in Canine

Simple Summary

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

Abstract

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

Characterization of embryonic stem-like cells derived from mouse spermatogonial stem cells following low-intensity ultrasound treatment

OBJECTIVE

Spermatogonial stem cells (SSCs) are able to form embryonic stem-like cells (ES-like cells) and embryonic bodies (EBs). Low-intensity ultrasound stimulation (LIUS) has positive effects on the growth and differentiation of the different cells. In this study, we tried to investigate the effects of LIUS on SSC differentiation to ES-like cells.

MATERIALS AND METHODS

SSCs were isolated from neonatal mice and their identification was confirmed by tracking of PLZF, Oct-4, and C-Kit proteins. The SSCs and Sertoli cells were co-cultured in DMEM/F12 supplemented with 15% FBS and LIF. SSCs stimulated by LIUS with 200mW/CM² intensity. Characterization of obtained ES-like cells was confirmed with Sox2, Oct-4, and SSEA-1 immunofluorescence staining. Also, real-time PCR was performed to analyse the expression of c-Myc and Nanog genes in ES-Like Cells and Stra8, Piwil2 and Plzf genes in SSCs after 21 days of the in vitro culture.

RESULTS

Our results showed c-Kit, PLZF and Oct-4 proteins were expressed positively in SSCs and Sox2, Oct-4, SSEA-1 in the ES-like cells by immunocytochemistry. The results of flow cytometry showed a significant increase in expression of c-Myc and Nanog in ES-like cells compared to SSCs (p<.05), whereas the Stra8, Piwil2, and Plzf became down-regulated during 21 days of culture. ES-like markers cell SSEA-1, Sox2 and Oct-4 were increased in the LIUS group compared to the control group (p<.05).

CONCLUSION

The results indicated that ES-like cells with pluripotency characteristics were derived from SSCs.

Spermatogonial stem cells are a promising and pluripotent cell source for regenerative medicine

Regenerative medicine has been shown to hold enormous potential to treat traumatic and degenerative diseases, and substantial advancements have been made in the recent decades. In particular, different cell types were evaluated in basic research and preclinical studies on cell-based therapy applications. Despite the extraordinary achievements made in experimental studies and clinical practice, a considerable number of obstacles, such as the cellular source, ethical and safety issues, hinder further clinical applications. Spermatogonial stem cells (SSCs) are gradually becoming the research focus of cell-based regenerative medicine owing to their unique merits over other types of stem cells, particularly the lack of ethical concerns and lower immunogenicity. In addition, SSCs have been successfully induced to differentiate into other cell types under different appropriate conditions in compelling studies. Based on these properties, we systemically reviewed the development of SSCs as an attractive cell source for cell-based regenerative medicine.

Integrated Analyses of Mouse Stem Cell Transcriptomes Provide Clues for Stem Cell Maintenance and Transdifferentiation

In vivo cell fate reprogramming has emerged as a new method for understanding cell plasticity and as potential treatment for tissue regeneration. Highly efficient and precise reprogramming requires fully understanding of the transcriptomes which function within different cell types. Here, we adopt weighted gene co-expression network analysis (WGCNA) to explore the molecular mechanisms of self-renewal in several well-known stem cell types, including embryonic stem cells (ESC), primordial germ cells (PGC), spermatogonia stem cells (SSC), neural stem cells (NSC), mesenchymal stem cells (MSC), and hematopoietic stem cells (HSC). We identified 37 core genes that were up-regulated in all of the stem cell types examined, as well as stem cell correlated gene co-expression networks. The validation of the co-expression genes revealed a continued protein-protein interaction network that included 823 nodes and 3113 edges. Based on the topology, we identified six densely connected regions within the continued protein-protein interaction network. The SSC specific genes Itgam, Cxcr6, and Agtr2 bridged four densely connected regions that consisted primarily of HSC-, NSC-, and MSC-correlated genes. The expression levels of identified stem cell related transcription factors were confirmed consistent with bioinformatics prediction in ESCs and NSCs by qPCR. Exploring the mechanisms underlying adult stem cell self-renewal will aid in the understanding of stem cell pool maintenance and will promote more accurate and efficient strategies for tissue regeneration and repair.

Spermatogonial Stem Cell Culture in Oncofertility

Infertility caused by chemotherapy or radiation treatments negatively impacts patient-survivor quality of life. The only fertility preservation option available to prepubertal boys who are not making sperm is cryopreservation of testicular tissues that contain spermatogonial stem cells (SSCs) with potential to produce sperm and/or restore fertility. SSC transplantation to regenerate spermatogenesis in infertile adult survivors of childhood cancers is a mature technology. However, the number of SSCs obtained in a biopsy of a prepubertal testis may be small. Therefore, methods to expand SSC numbers in culture before transplantation are needed. Here we review progress with human SSC culture.

Spermatogonial Stem Cells for In Vitro Spermatogenesis and In Vivo Restoration of Fertility

Spermatogonial stem cells (SSCs) are the only adult stem cells capable of passing genes onto the next generation. SSCs also have the potential to provide important knowledge about stem cells in general and to offer critical in vitro and in vivo applications in assisted reproductive technologies. After century-long research, proof-of-principle culture systems have been introduced to support the in vitro differentiation of SSCs from rodent models into haploid male germ cells. Despite recent progress in organotypic testicular tissue culture and two-dimensional or three-dimensional cell culture systems, to achieve complete in vitro spermatogenesis (IVS) using non-rodent species remains challenging. Successful in vitro production of human haploid male germ cells will foster hopes of preserving the fertility potential of prepubertal cancer patients who frequently face infertility due to the gonadotoxic side-effects of cancer treatment. Moreover, the development of optimal systems for IVS would allow designing experiments that are otherwise difficult or impossible to be performed directly in vivo, such as genetic manipulation of germ cells or correction of genetic disorders. This review outlines the recent progress in the use of SSCs for IVS and potential in vivo applications for the restoration of fertility.

Mechanisms regulating mammalian spermatogenesis and fertility recovery following germ cell depletion

Mammalian spermatogenesis is a highly complex multi-step process sustained by a population of mitotic germ cells with self-renewal potential known as spermatogonial stem cells (SSCs). The maintenance and regulation of SSC function are strictly dependent on a supportive niche that is composed of multiple cell types. A detailed appreciation of the molecular mechanisms underpinning SSC activity and fate is of fundamental importance for spermatogenesis and male fertility. However, different models of SSC identity and spermatogonial hierarchy have been proposed and recent studies indicate that cell populations supporting steady-state germline maintenance and regeneration following damage are distinct. Importantly, dynamic changes in niche properties may underlie the fate plasticity of spermatogonia evident during testis regeneration. While formation of spermatogenic colonies in germ-cell-depleted testis upon transplantation is a standard assay for SSCs, differentiation-primed spermatogonial fractions have transplantation potential and this assay provides readout of regenerative rather than steady-state stem cell capacity. The characterisation of spermatogonial populations with regenerative capacity is essential for the development of clinical applications aimed at restoring fertility in individuals following germline depletion by genotoxic treatments. This review will discuss regulatory mechanisms of SSCs in homeostatic and regenerative testis and the conservation of these mechanisms between rodent models and man.

Germline DNA replication timing shapes mammalian genome composition

Mammalian DNA replication is a highly organized and regulated process. Large, Mb-sized regions are replicated at defined times along S-phase. Replication Timing (RT) is thought to play a role in shaping the mammalian genome by affecting mutation rates. Previous analyses relied on somatic RT profiles. However, only germline mutations are passed on to offspring and affect genomic composition. Therefore, germ cell RT information is necessary to evaluate the influences of RT on the mammalian genome. We adapted the RT mapping technique for limited amounts of cells, and measured RT from two stages in the mouse germline - primordial germ cells (PGCs) and spermatogonial stem cells (SSCs). RT in germline cells exhibited stronger correlations to both mutation rate and recombination hotspots density than those of RT in somatic tissues, emphasizing the importance of using correct tissues-of-origin for RT profiling. Germline RT maps exhibited stronger correlations to additional genetic features including GC-content, transposable elements (SINEs and LINEs), and gene density. GC content stratification and multiple regression analysis revealed independent contributions of RT to SINE, gene, mutation, and recombination hotspot densities. Together, our results establish a central role for RT in shaping multiple levels of mammalian genome composition.

miR-30 Family miRNAs Mediate the Effect of Chronic Social Defeat Stress on Hippocampal Neurogenesis in Mouse Depression Model

Depression is a debilitating psychiatric disorder with a high rate of relapse and a low rate of response to antidepressant treatment. There is a dearth of new antidepressants due to an incomplete understanding of the molecular mechanisms involved in its etiopathology. Chronic stress appears to be one of the foremost underlying causes of depression. Studies in animal models in the past decade have implicated epigenetic mechanisms in mediating the negative effects of chronic stressful events on the progression/manifestation of depression and other co-morbid neuropsychiatric disorders. However, non-coding RNAs, another layer of epigenetic regulation is relatively less studied in depression. Here, using the chronic social defeat stress (CSDS)-induced depression model, we hypothesized dysregulation in miRNA-mRNA networks in the neurogenic dentate gyrus (DG) region of male C57BL/6 mice. Among several dysregulated miRNAs identified via miRNA arrays, the most striking finding was the downregulation of miRNAs of the miR-30 family in stressed/defeated mice. To investigate miRNAs in the DG-resident neural stem/progenitor cells (NSCs/NPCs), we used the in vitro neurosphere culture, where proliferating NSCs/NPCs were subjected to differentiation. Among several differentially expressed miRNAs, we observed an upregulation of miR-30 family miRNAs upon differentiation. To search for the gene targets of these miRNAs, we performed gene arrays followed by bioinformatics analysis, miRNA manipulations and luciferase assays. Our results suggest that miR-30 family miRNAs mediate chronic stress-induced depression-like phenotype by altering hippocampal neurogenesis and neuroplasticity via controlling the epigenetic and transcription regulators such as Mll3 and Runx1; and cell signaling regulators like Socs3, Ppp3r1, Gpr125, and Nrp1.

Spermatogonial stem cells

Spermatogonial stem cells (SSCs) are the most primitive spermatogonia in the testis and have an essential role to maintain highly productive spermatogenesis by self-renewal and continuous generation of daughter spermatogonia that differentiate into spermatozoa, transmitting genetic information to the next generation. Since the 1950s, many experimental methods, including histology, immunostaining, whole-mount analyses, and pulse-chase labeling, had been used in attempts to identify SSCs, but without success. In 1994, a spermatogonial transplantation method was reported that established a quantitative functional assay to identify SSCs by evaluating their ability to both self-renew and differentiate to spermatozoa. The system was originally developed using mice and subsequently extended to nonrodents, including domestic animals and humans. Availability of the functional assay for SSCs has made it possible to develop culture systems for their ex vivo expansion, which dramatically advanced germ cell biology and allowed medical and agricultural applications. In coming years, SSCs will be increasingly used to understand their regulation, as well as in germline modification, including gene correction, enhancement of male fertility, and conversion of somatic cells to biologically competent male germline cells.

Pluripotency Potential of Embryonic Stem Cell-Like Cells Derived from Mouse Testis

Objective

During the cultivation of spermatogonial stem cells (SSCs) and their conversion into embryonic stem-like (ES-like) cells, transitional ES-like colonies and epiblast-like cells were observable. In the present experimental study, we aimed to analyze the efficiency of the multipotency or pluripotency potential of ES-like cells, transitional colonies and epiblast-like cells.

Materials and Methods

In this experimental study, SSCs were isolated from transgenic octamer-binding transcription factor 4 (Oct4)-green fluorescent protein (GFP)-reporter mice. During cell culture ES-like, transitional and epiblast- like colonies developed spontaneously. The mRNA and protein expression of pluripotency markers were analyzed by Fluidigm real-time polymerase chain reaction (RT-PCR) and immunocytochemistry, respectively. Efficiency to produce chimera mice was evaluated after injection of ES and ES-like cells into blastocysts.

Results

Microscopic analyses demonstrated that the expression of Oct4-GFP in ES-like cells was very strong, in epiblast-like cells was not detectable, and was only partial in transitional colonies. Fluidigm RT-PCR showed a higher expression of the germ cell markers Stra-8 and Gpr-125 in ES-like cells and the pluripotency genes Dppa5, Lin28, Klf4, Gdf3 and Tdgf1 in ES-like colonies and embryonic stem cells (ESCs) compared to the epiblast-like and transitional colonies. No significant expression of Oct-4, Nanog, Sox2 and c-Myc was observed in the different groups. We showed a high expression level of Nanog and Klf4 in ES-like, while only a partial expression was observed in transitional colonies. We generated chimeric mice after blastocystic injection from ES and ES-like cells, but not from transitional colonies. We observed that the efficiency to produce chimeric mice in ES cells was more efficient (59%) in comparison to ES-like cells (22%).

Conclusion

This new data provides more information on the pluripotency or multipotency potentials of testis-derived ES-like cells in comparison to transitional colonies and epiblast-like cells.

Differential Proliferation Effects after Short-Term Cultivation of Mouse Spermatogonial Stem Cells on Different Feeder Layers

Objective

Spermatogonial stem cells (SSCs) provide the cellular basis for sperm production transforming the male’s genetic information to the next generation. We aimed to examine the effect of different feeder layer on proliferation of SSCs.

Materials and Methods

In this experimental study, we compared the in vitro effects of the co-culture of mouse SSCs with mouse embryonic fibroblasts (MEFs), sandos inbred mice (SIM) embryo-derived thioguanine- and ouabain- resistant (STO) feeders, and neonate and adult testicular stroma cell (TSC) feeders on the efficiency of mouse SSC proliferation and colony formation. Cells were cultivated on top of MEFs, STO, and neonate and adult TSCs feeder layers for 30 days. The number and diameter of colonies and also the number of cells were evaluated during day 7, 15, 25, and 30 of culture. The mRNA expression of germ cells and somatic cells were analyzed.

Results

In our study, we observed a significant difference in the proliferation rates and colony size of SSCs among the groups, especially for MEFs (P<0.05). SSCs can proliferate on MEFS, but not on STO, neonate or adult TSCs. Using immunocytochemistry by KI67 the proliferative activities of SSC colonies on MEFs were confirmed. The results of Fluidigm real-time polymerase chain reaction (RT-PCR) showed a high expression of the germ cell genes the promyelocytic leukemia zinc finger protein (PLZF), deleted in azoospermia-like (DAZL), octamer-binding transcription factor 4 (OCT4), and DEAD (Asp-Glu-Ala-Asp) box polypeptide 4 (DDX4 or VASA) in SSCs, and a low expression of these genes in the feeder layers. Furthermore, we observed a higher expression of vimentin and integrin-B1 in feeder layers than in SSCs (P<0.05).

Conclusion

Based on the optimal effect of MEFs for better colonization of SSCs, these feeder cells seem to be appropriate candidates for SSC cultures prior to transplantation. Therefore, it is suggested using these feeder cells for SSC cultivation.

Lessons from human umbilical cord: gender differences in stem cells from Wharton's jelly

OBJECTIVE

To study the molecular features of mesenchymal stem cells from Wharton Jelly (WJ-MSCs) of umbilical cord to predict their differentiation capacity.

DESIGN

Comparison of gene expression from mesenchymal stem cells of male and female umbilical cord SETTING: University hospital PATIENT (S): umbilical cords (n = 12, 6 males and 6 females) retrieved from spontaneous full-term vaginal delivery of healthy women INTERVENTION: we analyzed the expression of the stemness related genes C-MYC, OCT4, SOX2 and NANOG and of the epigenetic modulating gene DNA-methyltransferase 1 (DNMT1).

MEAN OUTCOME MEASURE

WJ-MSCs were isolated by standard procedures and immunophenotypically characterized. Gene expression analysis of stemness related genes and the epigenetic modulating gene DNMT1 were performed by real-time PCR RESULTS: expression of the OCT4 and DNMT1 genes was significantly higher in WJ- MSCs isolated from male subjects, as compared to MSCs isolated from female-derived WJ. The resulting higher expression of OCT4 and DNMT1 in WJ-MSCs from males as compared with female WJ-MSCs for the first time identifies a specific relationship between stemness genes, an epigenetic modulator, and gender differences.

CONCLUSION

our findings disclose novel biomedical implications in WJ-MSCs related to the sex of the donor, thus providing additional cues to exploit their regenerative potential in allogenic transplantation.

Heterogeneity of Spermatogonial Stem Cells

Germ cells transfer genetic materials from one generation to the next, which ensures the continuation of the species. Spermatogenesis, the process of male germ cell production, is one of the most productive systems in adult tissues. This high productivity depends on the well-coordinated differentiation cascade in spermatogonia, occurring via their synchronized cell division and proliferation. Spermatogonial stem cells (SSCs) are responsible for maintaining the spermatogonial population via self-renewal and the continuous generation of committed progenitor cells that differentiate into spermatozoa. Like other stem cells in the body, SSCs are defined by their self-renewal and differentiation abilities. A functional transplantation assay, in which these biological properties of SSCs can be quantitatively evaluated, was developed using mice, and the cell surface characteristics and intracellular marker gene expression of murine SSCs were successfully determined. Another approach to elucidate SSC identity is a cell lineage-tracing experiment using transgenic mice, which can track the SSC behavior in the testes. Recent studies using both these experimental approaches have revealed that the SSC identity changed depending upon the developmental, homeostatic, and regenerative circumstances. In addition, single-cell transcriptomic analyses have further indicated the instability of marker gene expression in SSCs. More studies are needed to unify the results of the determination of SSC identity based on the functional properties and accumulating transcriptomic data of SSCs, to elucidate the functional interaction between SSC behavior and gene products and illustrate the conserved features of SSCs amidst their heterogeneity. Furthermore, the deterministic roles of distinct SSC niches under different physiological conditions in the SSC heterogeneity and its causal regulators must also be clarified in future studies.

Competition for Mitogens Regulates Spermatogenic Stem Cell Homeostasis in an Open Niche

In many tissues, homeostasis is maintained by physical contact between stem cells and an anatomically defined niche. However, how stem cell homeostasis is achieved in environments where cells are motile and dispersed among their progeny remains unknown. Using murine spermatogenesis as a model, we find that spermatogenic stem cell density is tightly regulated by the supply of fibroblast growth factors (FGFs) from lymphatic endothelial cells. We propose that stem cell homeostasis is achieved through competition for a limited supply of FGFs. We show that the quantitative dependence of stem cell density on FGF dosage, the biased localization of stem cells toward FGF sources, and stem cell dynamics during regeneration following injury can all be predicted and explained within the framework of a minimal theoretical model based on "mitogen competition." We propose that this model provides a generic and robust mechanism to support stem cell homeostasis in open, or facultative, niche environments.

Elevated G-Protein Receptor 125 (GPR125) Expression Predicts Good Outcomes in Colorectal Cancer and Inhibits Wnt/β-Catenin Signaling Pathway

Background

G-protein receptor 125 (GPR125), as a transmembrane signal transducer, is involved in regulating cancer development. Although GPR125 is related with several cancers, its role in colorectal cancer (CRC) and the underlying mechanism are still unknown. Here, we investigated the clinical significance of GPR125 in CRC.

Material/Methods

We assessed the expression level of GPR125 in CRC tissues by analyzing 3 datasets in the Gene Expression Omnibus (GEO) database and in human samples. The correlation between GPR125 expression and clinicopathological features was further analyzed. Survival analysis was performed to assess the association between GPR125 expression and recurrence-free survival (RFS). Cox logistic regression analysis was used to analyze the role of GPR125 expression in overall survival (OS). Moreover, we activated the Wnt pathway in HCT116 cells to investigate their potential mechanism.

Results

Analysis of the GEO database showed that the expression of GPR125 was down-regulated in CRC tissues, consistent with our human samples experiments, and patients with higher GPR125 expression had a longer RFS. Also, we found that high GPR125 expression was associated with better tumor outcomes in clinical stage, metastasis, and KRAS status. Cox logistic regression analysis demonstrated that GPR125 was an independent prognostic factor for favorable outcome. Mechanistically, GPR125 overexpression inhibited the β-catenin transcriptional activity, and down-regulated the expression levels of the Wnt downstream proteins-Axin2, c-Myc, cylinD1, and lef-1.

Conclusions

GPR125 may be a potential prognosis-related anti-oncogene and its effects on inactivating Wnt/β-catenin signaling pathway might be a key link to inhibiting CRC formation.

Characterization of Human Mesenchymal Stem Cells Isolated from the Testis

Mesenchymal stem cells hold great promise for regenerative medicine as they can be easily isolated from different sources such as adipose tissue, bone marrow, and umbilical cord blood. Spontaneously arising pluripotent stem cells can be obtained in culture from murine spermatogonial stem cells (SSCs), while the pluripotency of the human counterpart remains a matter of debate. Recent gene expression profiling studies have demonstrated that embryonic stem cell- (ESC-) like cells obtained from the human testis are indeed closer to mesenchymal stem cells (MSCs) than to pluripotent stem cells. Here, we confirm that colonies derived from human testicular cultures, with our isolation protocol, are of mesenchymal origin and do not arise from spermatogonial stem cells (SSCs). The testis, thus, provides an important and accessible source of MSCs (tMSCs) that can be potentially used for nephrotoxicity testing in vitro. We further demonstrate, for the first time, that tMSCs are able to secrete microvesicles that could possibly be applied to the treatment of various chronic diseases, such as those affecting the kidney.

MiR-663a Stimulates Proliferation and Suppresses Early Apoptosis of Human Spermatogonial Stem Cells by Targeting NFIX and Regulating Cell Cycle

Human spermatogonial stem cells (SSCs) could have significant applications in reproductive medicine and regenerative medicine because of their great plasticity. The fate determinations of human SSCs are mediated by epigenetic factors. However, nothing is known about the regulation of non-coding RNA on human SSCs. Here we have explored for the first time the expression, function, and target of miR-663a in human SSCs. MiR-663a was upregulated in human spermatogonia compared with pachytene spermatocytes, as indicated by microRNA microarray and real-time PCR. CCK-8 and 5-Ethynyl-2′-deoxyuridine (EDU) assays revealed that miR-663a stimulated cell proliferation and DNA synthesis of human SSCs. Annexin V and propidium iodide (PI) staining and flow cytometry demonstrated that miR-663a inhibited early and late apoptosis of human SSCs. Furthermore, NFIX was predicted and verified as a direct target of miR-663a. NFIX silencing led to an enhancement of cell proliferation and DNA synthesis and a reduction of the early apoptosis of human SSCs. NFIX silencing neutralized the influence of miR-663a inhibitor on the proliferation and apoptosis of human SSCs. Finally, both miR-663a mimics and NFIX silencing upregulated the levels of cell cycle regulators, including Cyclin A2, Cyclin B1, and Cyclin E1, whereas miR-663a inhibitor had an adverse effect. Knockdown of Cyclin A2, Cyclin B1, and Cyclin E1 led to the decrease in the proliferation of human SSCs. Collectively, miR-663a has been identified as the first microRNA that promotes the proliferation and DNA synthesis and suppresses the early apoptosis of human SSCs by targeting NFIX via cell cycle regulators Cyclin A2, Cyclin B1, and Cyclin E1. This study thus provides novel insights into the molecular mechanisms underlying human spermatogenesis, and it could offer novel targets for treating male infertility and other human diseases.

PAK1 Promotes the Proliferation and Inhibits Apoptosis of Human Spermatogonial Stem Cells via PDK1/KDR/ZNF367 and ERK1/2 and AKT Pathways

Spermatogonial stem cells (SSCs) have significant applications in reproductive and regenerative medicine. However, nothing is known about genes in mediating human SSCs. Here we have explored for the first time the function and mechanism of P21-activated kinase 1 (PAK1) in regulating the proliferation and apoptosis of the human SSC line. PAK1 level was upregulated by epidermal growth factor (EGF), but not glial cell line-derived neurotrophic factor (GDNF) or fibroblast growth factor 2 (FGF2). PAK1 promoted proliferation and DNA synthesis of the human SSC line, whereas PAK1 suppressed its apoptosis in vitro and in vivo. RNA sequencing identified that PDK1, ZNF367, and KDR levels were downregulated by PAK1 knockdown. Immunoprecipitation and Western blots demonstrated that PAK1 interacted with PDK1. PDK1 and KDR levels were decreased by ZNF367-small interfering RNAs (siRNAs). The proliferation of the human SSC line was reduced by PDK1-, KDR-, and ZNF367-siRNAs, whereas its apoptosis was enhanced by these siRNAs. The levels of phos-ERK1/2, phos-AKT, and cyclin A were decreased by PAK1-siRNAs. Tissue arrays showed that PAK1 level was low in non-obstructive azoospermia patients. Collectively, PAK1 was identified as the first molecule that controls proliferation and apoptosis of the human SSC line through PDK1/KDR/ZNF367 and the ERK1/2 and AKT pathways. This study provides data on novel gene regulation and networks underlying the fate of human SSCs, and it offers new molecular targets for human SSCs in translational medicine.

Male germ cells support long-term propagation of Zika virus

Evidence of male-to-female sexual transmission of Zika virus (ZIKV) and viral RNA in semen and sperm months after infection supports a potential role for testicular cells in ZIKV propagation. Here, we demonstrate that germ cells (GCs) are most susceptible to ZIKV. We found that only GCs infected by ZIKV, but not those infected by dengue virus and yellow fever virus, produce high levels of infectious virus. This observation coincides with decreased expression of interferon-stimulated gene Ifi44l in ZIKV-infected GCs, and overexpression of Ifi44l results in reduced ZIKV production. Using primary human testicular tissue, we demonstrate that human GCs are also permissive for ZIKV infection and production. Finally, we identified berberine chloride as a potent inhibitor of ZIKV infection in both murine and human testes. Together, these studies identify a potential cellular source for propagation of ZIKV in testes and a candidate drug for preventing sexual transmission of ZIKV.

Reprogramming p53-Deficient Germline Stem Cells Into Pluripotent State by Nanog

Cultured mouse spermatogonial stem cells (SSCs), also known as germline stem cells (GSCs), revert back to pluripotent state either spontaneously or upon being modified genetically. However, the reprogramming efficiencies are low, and the underlying mechanism remains poorly understood. In the present study, we conducted transcriptomic analysis and found that many transcription factors and epigenetic modifiers were differentially expressed between GSCs and embryonic stem cells. We failed in reprogramming GSCs to pluripotent state using the Yamanaka 4 Factors, but succeeded when Nanog and Tet1 were included. More importantly, reprogramming was also achieved with Nanog alone in a p53-deficient GSC line with an efficiency of 0.02‰. These GSC-derived-induced pluripotent stem cells possessed in vitro and in vivo differentiation abilities despite the low rate of chimera formation, which might be caused by abnormal methylation in certain paternally imprinted genes. Together, these results show that GSCs can be reprogrammed to pluripotent state via multiple avenues and contribute to our understanding of the mechanisms of GSC reprogramming.

In silico identification of molecular mimics involved in the pathogenesis of Clostridium botulinum ATCC 3502 strain

Bacterial pathogens invade and disrupt the host defense system by means of protein sequences structurally similar at global and local level both. The sharing of homologous sequences between the host and the pathogenic bacteria mediates the infection and defines the concept of molecular mimicry. In this study, various computational approaches were employed to elucidate the pathogenicity of Clostridium botulinum ATCC 3502 at genome-wide level. Genome-wide study revealed that the pathogen mimics the host (Homo sapiens) and unraveled the complex pathogenic pathway of causing infection. The comparative 'omics' approaches helped in selective screening of 'molecular mimicry' candidates followed by the qualitative assessment of the virulence potential and functional enrichment. Overall, this study provides a deep insight into the emergence and surveillance of multidrug resistant C. botulinum ATCC 3502 caused infections. This is the very first report identifying C. botulinum ATCC 3502 proteome enriched similarities to the human host proteins and resulted in the identification of 20 potential mimicry candidates, which were further characterized qualitatively by sub-cellular organization prediction and functional annotation. This study will provide a variety of avenues for future studies related to infectious agents, host-pathogen interactions and the evolution of pathogenesis process.

Cep55 overexpression causes male-specific sterility in mice by suppressing Foxo1 nuclear retention through sustained activation of PI3K/Akt signaling

Spermatogenesis is a dynamic process involving self-renewal and differentiation of spermatogonial stem cells, meiosis, and ultimately, the differentiation of haploid spermatids into sperm. Centrosomal protein 55 kDa (CEP55) is necessary for somatic cell abscission during cytokinesis. It facilitates equal segregation of cytoplasmic contents between daughter cells by recruiting endosomal sorting complex required for transport machinery (ESCRT) at the midbody. In germ cells, CEP55, in partnership with testes expressed-14 (TEX14) protein, has also been shown to be an integral component of intercellular bridge before meiosis. Various in vitro studies have demonstrated a role for CEP55 in multiple cancers and other diseases. However, its oncogenic potential in vivo remains elusive. To investigate, we generated ubiquitously overexpressing Cep55 transgenic ( Cep55^Tg/Tg) mice aiming to characterize its oncogenic role in cancer. Unexpectedly, we found that Cep55^Tg/Tg male mice were sterile and had severe and progressive defects in spermatogenesis related to spermatogenic arrest and lack of spermatids in the testes. In this study, we characterized this male-specific phenotype and showed that excessively high levels of Cep55 results in hyperactivation of PI3K/protein kinase B (Akt) signaling in testis. In line with this finding, we observed increased phosphorylation of forkhead box protein O1 (FoxO1), and suppression of its nuclear retention, along with the relative enrichment of promyelocytic leukemia zinc finger (PLZF) -positive cells. Independently, we observed that Cep55 amplification favored upregulation of ret ( Ret) proto-oncogene and glial-derived neurotrophic factor family receptor α-1 ( Gfra1). Consistent with these data, we observed selective down-regulation of genes associated with germ cell differentiation in Cep55-overexpressing testes at postnatal day 10, including early growth response-4 ( Egr4) and spermatogenesis and oogenesis specific basic helix-loop-helix-1 ( Sohlh1). Thus, Cep55 amplification leads to a shift toward the initial maintenance of undifferentiated spermatogonia and ultimately results in progressive germ cell loss. Collectively, our findings demonstrate that Cep55 overexpression causes change in germ cell proportions and manifests as a Sertoli cell only tubule phenotype, similar to that seen in many azoospermic men.-Sinha, D., Kalimutho, M., Bowles, J., Chan, A.-L., Merriner, D. J., Bain, A. L., Simmons, J. L., Freire, R., Lopez, J. A., Hobbs, R. M., O'Bryan, M. K., Khanna, K. K. Cep55 overexpression causes male-specific sterility in mice by suppressing Foxo1 nuclear retention through sustained activation of PI3K/Akt signaling.

Recent advances of in vitro culture systems for spermatogonial stem cells in mammals

BACKGROUND

Spermatogonial stem cells (SSCs) in the mammalian testis are unipotent stem cells for spermatozoa. They show unique cell characteristics as stem cells and germ cells after being isolated from the testis and cultured in vitro. This review introduces recent progress in the development of culture systems for the establishment of SSC lines in mammalian species, including humans.

METHODS

Based on the published reports, the isolation and purification of SSCs, identification and characteristics of SSCs, and culture system for mice, humans, and domestic animals have been summarized.

RESULTS

In mice, cell lines from SSCs are established and can be reprogrammed to show pluripotent stem cell potency that is similar to embryonic stem cells. However, it is difficult to establish cell lines for animals other than mice because of the dearth of understanding about species-specific requirements for growth factors and mechanisms supporting the self-renewal of cultured SSCs. Among the factors that are associated with the development of culture systems, the enrichment of SSCs that are isolated from the testis and the combination of growth factors are essential.

CONCLUSION

Providing an example of SSC culture in cattle, a rational consideration was made about how it can be possible to establish cell lines from neonatal and immature testes.