Comparison of different in vitro differentiation conditions for murine female germline stem cells

Effects of trigonelline, diosgenin, and Cistanche deserticola polysaccharide on the culture of female germline stem cells in vitro

Female germline stem cells (FGSCs) are renewable sources of oocytes that play an indispensable role in re-establishing mammal fertility. Here, we have established FGSCs from neonatal mice, which exhibit characteristics of germline stem cells. We show that compared with monomeric trigonelline and diosgenin, macromolecular compounds Cistanche deserticola polysaccharides (CDPs) in Chinese herbal medicine can enhance the ability of FGSCs to differentiate into oocytes at appropriate concentrations while maintaining self-renewal in vitro. In contrast, trigonelline and diosgenin inhibited the expression of germ cell-specific genes while reducing cell proliferation activity. In summary, CDPs could induce the differentiation and self-renewal of FGSCs in vitro. The comparison of the effects of the active components of different types of Chinese medicine will provide a reference for the development of clinical drugs in the future, and help to elucidate the development process of FGSCs.

Application of Matrigel in the 3-dimension culture of female germline stem cells

Female germline stem cells (FGSCs) are a group of rare undifferentiated cells found in ovarian cortex, which have the unique ability to self-renew and differentiate. Stable maintenance and proliferation of FGSCs in culture are pivotal for clinic research. However, conventional 2-D (dimension) culture systems are limited in their ability to mimic the ovarian microenvironment during in vitro studies. To establish a suitable in vitro microenvironment for FGSCs, we conducted experiments using a Matrigel-based 3-D culture system. This involves testing different dilution ratios, medium compositions, and co-culture cells to find the optimal conditions for FGSCs maintenance and proliferation. Our results demonstrated the feasibility of using Matrigel as a FGSCs 3-D culture media. Moreover, co-culturing FGSCs with some types of cells in the Matrigel-based 3-D culture system had the potential to form ovarian organoids. Meanwhile, the safety of Matrigel was confirmed in vivo through transplantation experiment, which suggests the potential for clinic research.

Engineering Female Germline Stem Cells with Exocytotic Polymer Dots

Germline stem cells (GSCs) are the only cell population capable of passing genetic information to offspring, making them attractive targets in reproductive biology and fertility research. However, it is generally more difficult to introduce exogenous biomolecules into GSCs than other cell types, impeding the exploration and manipulation of these cells for biomedical purposes. Herein, semiconductor polymer dots (Pdots)-based nanocomplex Pdot-siRNA is developed and achieves effective knockdown of target genes in female germline stem cells (FGSCs). Advantage of high fluorescence brightness of Pdots is taken for comprehensive investigation of their cellular uptake, intracellular trafficking, and exocytosis in FGSCs. Importantly, Pdots show excellent biocompatibility and minimally disturb the differentiation of FGSCs. Intracellular Pdots escape from the lysosomes and undergo active exocytosis, which makes them ideal nanocarriers for bioactive cargos. Moreover, Pdot-siRNA can penetrate into 3D ovarian organoids derived from FGSCs and down-regulate the expression levels of target genes. This study investigates the interface between a type of theranostic nanoparticles and FGSCs for the first time and sheds light on the manipulation and medical application of FGSCs.

Inhibition of EED activity enhances cell survival of female germline stem cell and improves the oocytes production during oogenesis in vitro

Ovarian organoids, based on female germline stem cells (FGSCs), are nowadays widely applied for reproductive medicine screening and exploring the potential mechanisms during mammalian oogenesis. However, there are still key issues that urgently need to be resolved in ovarian organoid technology, one of which is to establish a culture system that effectively expands FGSCs in vitro, as well as maintaining the unipotentcy of FGSCs to differentiate into oocytes. Here, FGSCs were EED226 treated and processed for examination of proliferation and differentiation in vitro. According to the results, EED226 specifically increased FGSC survival by decreasing the enrichment of H3K27me3 on Oct4 promoter and exon, as well as enhancing OCT4 expression and inhibiting P53 and P63 expression. Notably, we also found that FGSCs with EED226 treatment differentiated into more oocytes during oogenesis in vitro, and the resultant oocytes maintained a low level of P63 versus control at early stage development. These results demonstrated that inhibition of EED activity appeared to promote the survival of FGSCs and markedly inhibited their apoptosis during in vitro differentiation. As a result of our study, we propose an effective culture strategy to culture FGSCs and obtain oocytes in vitro, which provides a new vision for oogenesis in vitro.

2cChIP-seq and 2cMeDIP-seq: The Carrier-Assisted Methods for Epigenomic Profiling of Small Cell Numbers or Single Cells

Chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq) can profile genome-wide epigenetic marks associated with regulatory genomic elements. However, conventional ChIP-seq is challenging when examining limited numbers of cells. Here, we developed a new technique by supplementing carrier materials of both chemically modified mimics with epigenetic marks and dUTP-containing DNA fragments during conventional ChIP procedures (hereafter referred to as 2cChIP-seq), thus dramatically improving immunoprecipitation efficiency and reducing DNA loss of low-input ChIP-seq samples. Using this strategy, we generated high-quality epigenomic profiles of histone modifications or DNA methylation in 10-1000 cells. By introducing Tn5 transposase-assisted fragmentation, 2cChIP-seq reliably captured genomic regions with histone modification at the single-cell level in about 100 cells. Moreover, we characterized the methylome of 100 differentiated female germline stem cells (FGSCs) and observed a particular DNA methylation signature potentially involved in the differentiation of mouse germline stem cells. Hence, we provided a reliable and robust epigenomic profiling approach for small cell numbers and single cells.

Cistanche deserticola polysaccharides extracted from Cistanche deserticola Y.C. Ma promote the differentiation of mouse female germline stem cells in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese herbal medicine Cistanche deserticola Y.C. Ma has been recorded and treatment for infertility and impotence since ancient times, which is widely distributed in northwest China, and is mainly composed of phenylethanol glycosides, iridoids, lignans, polysaccharides, alkaloids, etc. C. deserticola polysaccharides (CDPs) is one of its main active ingredients, studies of its effect on germline stem cells are limited so far.

AIM OF THE STUDY

The aim of this study was to clarify that CDPs promoted the differentiation of FGSCs in vitro, and to initially clarify its possible cell signaling pathways.

MATERIAL AND METHODS

The cells were randomly divided into two groups. Normal FGSCs culture medium and the optimal concentration of CDPs (0.5 μg/mL) were added for culture, which was the selected treatment concentration that could promote cell differentiation on the basis of maintaining cell viability. After treatment for different time periods (12 h, 24 h, 36 h, 48 h), the cell proliferation and differentiation were evaluated by CCK-8, real-time PCR (qPCR), cell immunofluorescence and Western blot. Subsequently, RNA-Seq and data analysis were used to preliminarily analyze and verify the different genes and possible signal pathways.

RESULTS

Under the treatment of CDPs, cell viability was relatively better, and the expression of meiotic markers stimulated by retinoic acid gene 8 protein (Stra8) and synaptonemal complex protein 3 (Sycp3) significantly increased. In addition, their cell morphology was more similar to oocytes. Comparison of gene expression in FGSCs identified key differential expression genes (DEGs) by RNA-Seq that consisted of 549 upregulated and 465 downregulated genes. The DEGs enriched in the functional categories of germline cell development and relevant signaling pathways, which jointly regulate self-renewal and differentiation of FGSCs. The transforming growth factor β (TGF-β) signaling pathway and bone morphogenetic protein (BMP) signaling pathway might be activated to synergistically influence cell differentiation during the CDPs treatment of FGSCs.

CONCLUSION

These findings indicated that CDPs could promote the differentiation of FGSCs in vitro and could be regulated by different DEGs and signal transduction. Preliminary mechanism studies have shown that CDPs can exert their biological activities by regulating the TGF-β and BMP signaling pathways.

Non-neutral clonal selection and its potential role in mammalian germline stem cell dysfunction with advancing age

The concept of natural selection, or "survival of the fittest", refers to an evolutionary process in nature whereby traits emerge in individuals of a population through random gene alterations that enable those individuals to better adapt to changing environmental conditions. This genetic variance allows certain members of the population to gain an advantage over others in the same population to survive and reproduce in greater numbers under new environmental pressures, with the perpetuation of those advantageous traits in future progeny. Here we present that the behavior of adult stem cells in a tissue over time can, in many respects, be viewed in the same manner as evolution, with each stem cell clone being representative of an individual within a population. As stem cells divide or are subjected to cumulative oxidative damage over the lifespan of the organism, random genetic alterations are introduced into each clone that create variance in the population. These changes may occur in parallel to, or in response to, aging-associated changes in microenvironmental cues perceived by the stem cell population. While many of these alterations will be neutral or silent in terms of affecting cell function, a small fraction of these changes will enable certain clones to respond differently to shifts in microenvironmental conditions that arise with advancing age. In some cases, the same advantageous genetic changes that support survival and expansion of certain clones over others in the population (viz. non-neutral competition) could be detrimental to the downstream function of the differentiated stem cell descendants. In the context of the germline, such a situation would be devastating to successful propagation of the species across generations. However, even within a single generation, the “evolution” of stem cell lineages in the body over time can manifest into aging-related organ dysfunction and failure, as well as lead to chronic inflammation, hyperplasia, and cancer. Increased research efforts to evaluate stem cells within a population as individual entities will improve our understanding of how organisms age and how certain diseases develop, which in turn may open new opportunities for clinical detection and management of diverse pathologies.

Retinoic acid induced meiosis initiation in female germline stem cells by remodelling three-dimensional chromatin structure

Objectives

This study aimed to clarify the regulation and mechanism of meiotic initiation in FGSC development.

Materials and Methods

FGSCs were induced to differentiate into meiosis in differentiation medium. RNA sequencing was performed to analysis the difference of transcription level. High‐through chromosome conformation capture sequencing (Hi‐C) was performed to analysis changes of three‐dimensional chromatin structure. Chromosome conformation capture further confirmed a spatial chromatin loop. ChIP‐qPCR and dual luciferase reporter were used to test the interaction between Stimulated by retinoic acid gene 8 (STRA8) protein and Trip13 promoter.

Results

Compared with FGSCs, the average diameter of STRA8‐positive germ cells increased from 13 μm to 16.8 μm. Furthermore, there were 4788 differentially expressed genes between the two cell stages; Meiosis and chromatin structure‐associated terms were significantly enriched. Additionally, Hi‐C results showed that FGSCs underwent A/B compartment switching (switch rate was 29.81%), the number of topologically associating domains (TADs) increasing, the average size of TADs decreasing, and chromatin loop changes at genome region of Trip13 from undifferentiated stage to meiosis‐initiation stage. Furthermore, we validated that Trip13 promoter contacted distal enhancer to form spatial chromatin loop and STRA8 could bind Trip13 promoter to promote gene expression.

Conclusion

FGSCs underwent chromatin structure remodelling from undifferentiated stage to meiosis‐initiation stage, which facilitated STRA8 binding to Trip13 promoter and promoting its expression.

Progress in germline stem cell transplantation in mammals and the potential usage

Germline stem cells (GSCs) are germ cells with the capacities of self-renewal and differentiation into functional gametes, and are able to migrate to their niche and reconstitute the fertility of recipients after transplantation. Therefore, GSCs transplantation is a promising technique for fertility recovery in the clinic, protection of rare animals and livestock breeding. Though this novel technique faces tremendous challenges, numerous achievements have been made after several decades' endeavor. This review summarizes the current knowledge of GSCs transplantation and its utilization in mammals, and discusses the application prospect in reproductive medicine and animal science.

Generation of offspring-producing 3D ovarian organoids derived from female germline stem cells and their application in toxicological detection

In vitro production of oocytes capable of producing offspring has exciting potential applications in reproductive medicine. Here, we generated and characterized an ovarian organoid model derived from female germline stem cells using a three-dimensional culture system. We show that this model generated normal offspring and detected drug toxicity. The ovarian organoids could produce oocytes and exhibited endocrine functions. Single-cell analysis of ovarian organoids identified six ovarian cell lineages, such as germ, granulosa and theca cells, and produced gene-expression signatures for each cell type. Investigation of the expression patterns of genes related to meiosis and gene ontogeny analysis for germ cell clusters showed that a germ cell population was maintained in the ovarian organoids. Moreover, flow cytometric analysis confirmed that the population of germ cells could be maintained on the organoids and showed that ascorbic acid treatment had a beneficial effect of germ cell population maintenance on the organoids. Furthermore, we demonstrated the successful production of offspring from oocytes derived from ovarian organoids. Finally, we showed the ovarian organoids had the potential to drug toxicological detection. For example, we found that salinomycin impaired the formation of ovarian organoids and germ cell population maintenance by inducing apoptosis. These results indicate that the female germline stem cell-derived ovarian organoids represent a valuable model system for generating oocytes that can yield offspring, and provide a novel model for drug screening and toxicological detection.

Serum- and Feeder-Free Culture of Juvenile Monkey Female Germline Stem Cells and Testosterone Regulation of their Self-Renewal

Female germline stem cells (FGSCs) have been found in mouse, rat, pig, sheep and human ovaries. However, there is no information on the isolation or long-term culture of FGSCs from non-human primates. Here, we identified the presence of FGSCs in the ovaries of juvenile (3-4-year-old) cynomolgus monkeys using DDX4 and Ki67 double immunofluorescence. Then, a long-term serum- and cell feeder-free culture system for these FGSCs was used to establish a cell line, and its biological characteristics were analyzed. We found that testosterone promoted self-renewal of the cells. This study confirmed for the first time the presence of FGSCs in the ovary of non-human primates. This culture system and cell line will be of great significance for research in medicine and reproductive biology.

Ubiquitin-Specific-Processing Protease 7 Regulates Female Germline Stem Cell Self-Renewal Through DNA Methylation

Ubiquitin-specific-processing protease 7 (Usp7) is a key deubiquitinase controlling epigenetic modification and regulating the self-renewal, proliferation, and differentiation of stem cells. However, the functions and mechanisms of action of Usp7 on female germline stem cells (FGSCs) are unknown. Here, we demonstrated that Usp7 regulated FGSC self-renewal via DNA methylation. The results of Cell Counting Kit-8 and 5-ethynyl-20-deoxyuridine assays showed that the viability and proliferation of FGSCs were negatively regulated by Usp7. Moreover, Usp7 downregulated the expression of self-renewal genes, such as Oct4, Etv5, Foxo1, and Akt, but upregulated the expression of differentiation-related genes including Stra8 and Sycp3. Mechanistically, RNA-seq results showed that Usp7 negatively regulated FGSC self-renewal but positively modulated differentiation in FGSCs. Meanwhile, both overexpression and knockdown of Usp7 resulted in significant changes in DNA methylation and histone modification in FGSCs. Additionally, RNA-seq and MeDIP-seq analyses showed that Usp7 regulates the self-renewal and differentiation of FGSCs mainly through DNA methylation rather than histone modification, which was also confirmed by a rescue assay. Our study not only offers a novel method to research FGSC self-renewal and differentiation in view of epigenetic modifications, but also provides a deep understanding of FGSC development.

C28 induced autophagy of female germline stem cells in vitro with changes of H3K27 acetylation and transcriptomics

There are a few studies indicating that small molecular compounds affect the proliferation, differentiation, apoptosis, and autophagy of female germline stem cells (FGSCs). However, whether small molecular compound 28 (C28) affect development of FGSCs remains unknown. In this study, we found that C28 reduced the viability and proliferation of FGSCs, respectively. Additionally, western blotting showed that the expression of autophagy marker light chain 3 beta II (LC3B-II) was significantly increased and expression of sequestosome-1 (SQSTM1) was significantly reduced in C28-treated groups. Immunofluorescence showed that, in C28-treated groups, the number of LC3B-II-positive puncta was increased significantly. These results indicated that C28 induced autophagy of FGSCs in vitro. Furthermore, data from Chromatin Immunoprecipitation Sequencing for H3K27ac showed that autophagy-related biological processes such as regulation of mitochondrial membrane potential, Golgi vesicle transport, and cellular response to reactive oxygen species were different after C28-treated. In addition, RNA-Seq showed that the expression of genes (Trib3, DDIT3, and ATF4) related to endoplasmic reticulum (ER) stress was enhanced by C28. These results suggest that the changes of H3K27ac and ER stress might be associated with C28-induced FGSC autophagy.

Integrated Glycosylation Patterns of Glycoproteins and DNA Methylation Landscapes in Mammalian Oogenesis and Preimplantation Embryo Development

Glycosylation is one of the most fundamental post-translational modifications. However, the glycosylation patterns of glycoproteins have not been analyzed in mammalian preimplantation embryos, because of technical difficulties and scarcity of the required materials. Using high-throughput lectin microarrays of low-input cells and electrochemical techniques, an integration analysis of the DNA methylation and glycosylation landscapes of mammal oogenesis and preimplantation embryo development was performed. Highly noticeable changes occurred in the level of protein glycosylation during these events. Further analysis identified several stage-specific lectins including LEL, MNA-M, and MAL I. It was later confirmed that LEL was involved in mammalian oogenesis and preimplantation embryogenesis, and might be a marker of FGSC differentiation. Modified nanocomposite polyaniline/AuNPs were characterized by electron microscopy and modification on bare gold electrodes using layer-by-layer assembly technology. These nanoparticles were further subjected to accuracy measurements by analyzing the protein level of ten-eleven translocation protein (TET), which is an important enzyme in DNA demethylation that is regulated by O-glycosylation. Subsequent results showed that the variations in the glycosylation patterns of glycoproteins were opposite to those of the TET levels. Moreover, analysis of correlation between the changes in glyco-gene expression and female germline stem cell glycosylation profiles indicated that glycosylation was related to DNA methylation. Subsequent integration analysis showed that the trend in the variations of glycosylation patterns of glycoproteins was similar to that of DNA methylation and opposite to that of the TET protein levels during female germ cell and preimplantation embryo development. Our findings provide insight into the complex molecular mechanisms that regulate human embryo development, and a foundation for further elucidation of early embryonic development and informed reproductive medicine.

In Vitro Generation of Oocyte Like Cells and Their In Vivo Efficacy: How Far We have been Succeeded

In the last few decades, stem cell therapy has grown as a boon for many pathological complications including female reproductive disorders. In this review, a brief description of available strategies that are related to stem cell-based in vitro oocyte-like cell (OLC) development are given. We have tried to cover all the aspects and latest updates of the in vitro OLC developmental methodologies, marker profiling, available disease models, and in vivo efficacies, with a special focus on mesenchymal stem cells (MSCs), induced pluripotent stem cells (iPSCs), and embryonic stem cells (ESCs) usage. The differentiation abilities of both the ovarian and non-ovarian stem cell sources under various induction conditions have shown different effects on morphological alterations, proliferation- and size-associated developments, hormonal secretions under gonadotropic stimulations, and their neo-oogenesis or folliculogenesis abilities after in vivo transplantations. The attainment of characters like oocyte-like morphology, size expansion, and meiosis initiation have been found to be major obstacles during in vitro oogenesis. A number of reports have either lacked in vivo studies or have shown their functional incapability to produce viable and healthy offspring. Though researchers have gained many valuable insights regarding in vitro gametogenesis, still there are many things to do to make stem cell-derived OLCs fully functional.

Hedgehog pathway inhibition causes primary follicle atresia and decreases female germline stem cell proliferation capacity or stemness

Background

Follicle depletion is one of the causes of premature ovarian failure (POF) and primary ovarian insufficiency (POI). Hence, maintenance of a certain number of female germline stem cells (FGSCs) is optimal to produce oocytes and replenish the primordial follicle pool. The mechanism that regulates proliferation or stemness of FGSCs could contribute to restoring ovarian function, but it remains uncharacterized in postnatal mammalian ovaries. This study aims to investigate the mechanism by which inhibiting the activity of the hedgehog (Hh) signaling pathway regulates follicle development and FGSC proliferation.

Methods and results

To understand the role of the Hh pathway in ovarian aging, we measured Hh signaling activity at different reproductive ages and the correlation between them in physiological and pathological mice. Furthermore, we evaluated the follicle number and development and the changes in FGSC proliferation or stemness after blocking the Hh pathway in vitro and in vivo. In addition, we aimed to explain one of the mechanisms for the FGSC phenotype changes induced by treatment with the Hh pathway-specific inhibitor GANT61 via oxidative stress and apoptosis. The results show that the activity of Hh signaling is decreased in the ovaries in physiological aging and POF models, which is consistent with the trend of expression levels of the germline stem cell markers Mvh and Oct4. In vitro, blocking the Hh pathway causes follicular developmental disorders and depletes ovarian germ cells and FGSCs after treating ovaries with GANT61. The proliferation or stemness of cultured primary FGSCs is reduced when Hh activity is blocked. Our results show that the antioxidative enzyme level and the ratio of Bcl-2/Bax decrease, the expression level of caspase 3 increases, the mitochondrial membrane potential is abnormal, and ROS accumulate in this system.

Conclusions

We observed that the inhibition of the Hh signaling pathway with GANT61 could reduce primordial follicle number and decrease FGSC reproductive capacity or stemness through oxidative damage and apoptosis.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1299-5) contains supplementary material, which is available to authorized users.

GAS5/miR-21 Axis as a Potential Target to Rescue ZCL-082-Induced Autophagy of Female Germline Stem Cells In Vitro

Several studies have recently revealed the regulatory mechanisms underlying female germline stem cell (FGSC) differentiation, proliferation, and apoptosis, but other biological processes such as autophagy and its mechanism in FGSCs are largely unclear. The use of small chemical compounds may be a good approach to further investigate the process and mechanism of autophagy in FGSC development. In this study, we used ZCL-082, a derivative of benzoxaboroles, to treat FGSCs. Using a cell counting kit-8 (CCK8) and 5-ethynyl-2′-deoxyuridine (EdU) assays, we found that ZCL-082 could significantly reduce the viability, proliferation, and number of FGSCs in vitro. Moreover, western blotting revealed that the expression of light chain 3 beta 2 (LC3B-II) in FGSCs was significantly increased after treatment with ZCL-082 for 3 and 6 h. Meanwhile, the expression of sequestosome-1 (SQSTM1) was significantly decreased. These results suggested that ZCL-082 can induce autophagy of FGSCs in vitro. Regarding the molecular mechanism, ZCL-082 could significantly reduce the expression of growth arrest-specific 5 (GAS5) long non-coding RNA, which could directly bind to microRNA-21a (miR-21a) and negatively regulate each other in FGSCs. Knockdown of GAS5 induced the autophagy of FGSCs, while GAS5 overexpression inhibited the autophagy of FGSCs in vitro and rescued FGSC autophagy induced by ZCL-082. Additionally, overexpression of miR-21a significantly enhanced LC3B-II protein expression while significantly reducing the expression of programmed cell death protein 4 (PDCD4) and SQSTM1 protein in FGSCs compared with control cells. The inhibition of miR-21a significantly reduced the basal or ZCL-082-induced upregulated expression of LC3B-II, and it significantly enhanced the expression of PDCD4 while downregulating the basal or ZCL-082-induced expression of SQSTM1 in FGSCs. Furthermore, the overexpression of GAS5 enhanced the protein expression of PDCD4, but knockdown of GAS5 reduced the protein expression of PDCD4. Taken together, these results suggested that ZCL-082 induced autophagy through GAS5 functioning as a competing endogenous RNA (ceRNA) sponge for miR-21a in FGSCs. It also suggested that the GAS5/miR-21a axis may be a potential therapeutic target for premature ovarian failure in the clinic.

C89 Induces Autophagy of Female Germline Stem Cells via Inhibition of the PI3K-Akt Pathway In Vitro

Postnatal female germline stem cells (FGSCs) are a type of germline stem cell with self-renewal ability and the capacity of differentiation toward oocyte. The proliferation, differentiation, and apoptosis of FGSCs have been researched in recent years, but autophagy in FGSCs has not been explored. This study investigated the effects of the small-molecule compound 89 (C89) on FGSCs and the underlying molecular mechanism in vitro. Cytometry, Cell Counting Kit-8 (CCK8), and 5-ethynyl-2'-deoxyuridine (EdU) assay showed that the number, viability, and proliferation of FGSCs were significantly reduced in C89-treated groups (0.5, 1, and 2 µM) compared with controls. C89 had no impact on FGSC apoptosis or differentiation. However, C89 treatment induced the expression of light chain 3 beta II (LC3BII) and reduced the expression of sequestosome-1 (SQSTM1) in FGSCs, indicating that C89 induced FGSC autophagy. To investigate the mechanism of C89-induced FGSC autophagy, RNA-seq technology was used to compare the transcriptome differences between C89-treated FGSCs and controls. Bioinformatics analysis of the sequencing data indicated a potential involvement of the phosphatidylinositol 3 kinase and kinase Akt (PI3K-Akt) pathway in the effects of C89's induction of autophagy in FGSCs. Western blot confirmed that levels of p-PI3K and p-Akt were significantly reduced in the C89- or LY294002 (PI3K inhibitor)-treated groups compared with controls. Moreover, we found cooperative functions of C89 and LY294002 in inducing FGSC autophagy through suppressing the PI3K-Akt pathway. Taken together, this research demonstrates that C89 can reduce the number, viability, and proliferation of FGSCs by inducing autophagy. Furthermore, C89 induced FGSC autophagy by inhibiting the activity of PI3K and Akt. The PI3K-Akt pathway may be a target to regulate FGSC proliferation and death.

Comparison of different in vitro differentiation conditions for murine female germline stem cells

Objectives

In vitro differentiation of oocytes from female germline stem cells (FGSCs) has exciting potential applications for reproductive medicine. Some researchers have attempted to reveal the in vitro differentiation capacity of FGSCs. However, no systematic comparative study of in vitro differentiation conditions has been performed for murine FGSCs (mFGSCs).

Materials and Methods

mFGSCs line was cultured under five different conditions for in vitro differentiation. RT‐PCR was performed to detect the expression of Oct4, Fragilis, Blimp1, Mvh, Scp3 and Zp3. Immunofluorescence was carried out to test the expression of Mvh, Fragilis and Zp3. Two‐photon laser‐scanning microscope was used to analyze nucleus‐plasma ratio, and the proportion of chromatin of GV oocytes differentiated from mFGSCs in vitro (IVD‐GVO), GV oocytes from in vivo (GVO) and mFGSCs.

Results

RT‐PCR and immunofluorescence showed that mFGSC line expressed germ cell‐specific markers, but not a meiosis‐specific marker. By evaluating five different in vitro differentiation conditions, condition 5, which included a hanging drop procedure and co‐culture of mFGSCs with granulosa cells, was shown to be optimal. mFGSCs could be successfully differentiated into germinal vesicle (GV) ‐stage oocytes under this condition. 3D observation revealed that both the nucleus‐plasma ratio and proportion of chromatin were not significantly different between IVD‐GVO and GVO.

Conclusion

We evaluated five in vitro differentiation conditions for mFGSCs and successfully differentiate mFGSCs into GV‐stage oocytes using a three‐step differentiation process.