Effect of GSK-3 inhibitor on the proliferation of multipotent male germ line stem cells (mGSCs) derived from goat testis

Glycogen Synthase Kinase-3 Isoform Variants and Their Inhibitory Phosphorylation in Human Testes and Spermatozoa

PURPOSE

To clarify (phospho-) glycogen synthase kinase-3 (GSK3) isoform variants in the germline and soma of human testes and spermatozoa.

MATERIALS AND METHODS

GSK3 isoform variants in normospermatogenic and Sertoli cell-only (SCO) testicular biopsies and spermatozoa were examined.

RESULTS

In normospermatogenic testes, GSK3α and GSK3β variants 1 and 2 different in low complexity region (LCR) were expressed and their levels were decreased in SCO testes. GSK3β variant 3 was only expressed in SCO testes. GSK3β as well as GSK3α, the dominant isoforms in testes were decreased in SCO testes. In normospermatogenic testes, GSK3β were found in spermatogonia and markedly decreased in meiotic germ cells in which GSK3α was dominant. p-GSK3α/β were marginal in spermatogonia and early spermatocytes. In SCO testes, GSK3α/β immunoreactivity in seminiferous epithelia was weaker than those of normospermatogenic testes whereas p-GSK3α/β(Ser) immunoreactivity was visibly increased in Sertoli cells. GSK3α was dominant in ejaculated spermatozoa in which GSK3α and p-GSK3α(Ser) were found in the head, midpiece, and tail. In acrosome-reacted spermatozoa, GSK3α was found in the equatorial region of head, midpiece, and tail, and p-GSK3α(Ser) was only found in midpiece. During sperm capacitation, p-GSK3α(Ser) was significantly increased together with phosphotyrosine proteins and motility.

CONCLUSIONS

In human male germ cells, GSK3 isoforms different in LCRs switch from GSK3β to GSK3α during meiotic entry, suggesting the isoform-specific roles of GSK3α and GSK3β in meiosis and stemness or proliferation of spermatogonia, respectively. In dormant Sertoli cells of SCO testes kinase activity of GSK3 might be downregulated via inhibitory phosphorylation. In spermatozoa, inhibitory phosphorylation of GSK3α might be coupled with activation of motility during capacitation.

Dmrt1 regulates the immune response by repressing the TLR4 signaling pathway in goat male germline stem cells

Double sex and mab-3-related transcription factor 1 (Dmrt1), which is expressed in goat male germline stem cells (mGSCs) and Sertoli cells, is one of the most conserved transcription factors involved in sex determination. In this study, we highlighted the role of Dmrt1 in balancing the innate immune response in goat mGSCs. Dmrt1 recruited promyelocytic leukemia zinc finger (Plzf), also known as zinc finger and BTB domain-containing protein 16 (Zbtb16), to repress the Toll-like receptor 4 (TLR4)-dependent inflammatory signaling pathway and nuclear factor (NF)-κB. Knockdown of Dmrt1 in seminiferous tubules resulted in widespread degeneration of germ and somatic cells, while the expression of proinflammatory factors were significantly enhanced. We also demonstrated that Dmrt1 stimulated proliferation of mGSCs, but repressed apoptosis caused by the immune response. Thus, Dmrt1 is sufficient to reduce inflammation in the testes, thereby establishing the stability of spermatogenesis and the testicular microenvironment.

Interaction between DMRT1 and PLZF protein regulates self-renewal and proliferation in male germline stem cells

Double sex and mab-3 related transcription factor 1 (DMRT1) encodes a double sex/mab-3 (DM) domain, which is the most conserved structure that involved in sex determination both in vertebrates and invertebrates. This study revealed important roles of DMRT1 in maintaining self-renewal of male germline stem cells (mGSCs). Our results showed that insufficient expression of DMRT1 in mice testes resulted in decreased number of spermatogonial cells and collapse of testicular niche in vivo. Self-renewal and proliferation of mGSCs were inhibited. Based on the bimolecular fluorescence complementation (BiFC) and co-immunoprecipitation (co-IP) assay, it was finally revealed that the interaction between DMRT1 and promyelocytic leukemia zinc finger (PLZF) protein was essential for maintaining self-renewal of mGSCs. Moreover, BTB domain of PLZF, DM and DMRT1 domain of DMRT1 were indispensable in mGSC, which were responsible for preserving the quantity of germ cells. Our research provided a new scientific basis for studying the mechanism of self-renewal and spermatogenesis in goat mGSCs.

Activation of Wnt/β-Catenin Signaling Pathway Enhances the Derivation of Buffalo (Bubalus bubalis) Embryonic Stem Cell-Like Cells

Wnt/β-Catenin signaling pathway plays an important role in maintaining self-renewal and pluripotency of human and mouse embryonic stem cells (ESCs). Activation of Wnt/β-Catenin signaling pathway by glycogen synthase kinase-3 (GSK3) inhibitor, the Wnt signaling agonist, could maintain the pluripotency of human and mouse ESCs in the presence of serum. However, the role of signaling pathway in the derivation of buffalo ESCs remains unclear. In this study, we used GSK3 inhibitors (6-bromoindirubin-3'-oxime [BIO] and CHIR99021) and investigated the effect of Wnt/β-Catenin activation on colony formation, proliferation, self-renewal, and pluripotency of Chinese swamp buffalo (buffalo) embryonic stem cell-like cells (ES-like cells), which were isolated from blastocysts. The results showed that buffalo ES-like cells displayed typical morphological characteristics of pluripotent stem cells: positive for alkaline phosphatase staining, expression of pluripotent markers, including OCT4, SOX2, SSEA-1, SSEA-4, LIN28, CH1, NANOG, and the proliferative markers, PCNA and C-MYC. Furthermore, activation of Wnt/β-Catenin signaling pathway by GSK3 inhibitors could promote colony formation and proliferation of buffalo ES-like cells and maintain their undifferentiated state, and upregulate the expression levels of pluripotent-related genes and proliferation-related genes. These results indicated that Wnt/β-Catenin signaling pathway plays an important role in the derivation and pluripotency of buffalo ES-like cells.

p53 inhibits the proliferation of male germline stem cells from dairy goat cultured on poly-L-lysine

Male germline stem cells (mGSCs) can transmit genetic materials to the next generation and dedifferentiate into pluripotent stem cells. However, in livestock, mGSC lines are difficult to establish, because of the factors that affect their isolation and culture. The extracellular matrix serves as a substrate for attachment and affects the fate of these stem cells. Poly-L-lysine (PL), an extracellular matrix of choice, inhibits and/or kills cancer cells, and promotes the attachment of stem cells in culture. However, how it affects the characteristics and potentials of these stem cells in culture needs to be elucidated. Here, we isolated, enriched and cultured dairy goat mGSCs on five types of extracellular matrices. To explore the best extracellular matrix to use for culturing them, the characteristics and proliferation ability of the cells were determined. Results showed that the cells shared several characteristics with previously reported mGSCs, including the poor effect of PL on their proliferative and colony-forming abilities. Further examination showed upregulation of p53 expression in these cells, which could be inhibiting their proliferation. When a p53 inhibitor was included in the culture medium, it was confirmed to be responsible for the inhibition of proliferation in mGSCs. Optimal concentration of the inhibitor in the culture of these cells was 5 µM. Furthermore, addition of the p53 inhibitor increased the expression of the markers of self-renewal and cell cycle in goat mGSCs. In summary, suppressing p53 is beneficial for the proliferation of dairy goat mGSCs, cultured on PL.

Previously claimed male germline stem cells from porcine testis are actually progenitor Leydig cells

Background

Male germline stem cells (mGSCs) offer great promise in regenerative medicine and animal breeding due to their capacity to maintain self-renewal and to transmit genetic information to the next generation following spermatogenesis. Human testis-derived embryonic stem cell-like cells have been shown to possess potential of mesenchymal progenitors, but there remains confusion about the characteristics and origin of porcine testis-derived stem cells.

Methods

Porcine testis-derived stem cells were obtained from primary testicular cultures of 5-day old piglets, and selectively expanded using culture conditions for long-term culture and induction differentiation. The stem cell properties of porcine testis-derived stem cells were subsequently assessed by determining the expression of pluripotency-associated markers, alkaline phosphatase (AP) activity, and capacity for sperm and multilineage differentiation in vitro. The gene expression profile was compared via microarray analysis.

Results

We identified two different types of testis-derived stem cells (termed as C1 and C2 here) during porcine testicular cell culture. The gene expression microarray analysis showed that the transcriptome profile of C1 and C2 differed significantly from each other. The C1 appeared to be morphologically similar to the previously described mouse mGSCs, expressed pluripotency- and germ cell-associated markers, maintained the paternal imprinted pattern of H19, displayed alkaline phosphatase activity, and could differentiate into sperm. Together, these data suggest that C1 represent the porcine mGSC population. Conversely, the C2 appeared similar to the previously described porcine mGSCs with three-dimensional morphology, abundantly expressed Leydig cell lineage and mesenchymal cell-specific markers, and could differentiate into testosterone-producing Leydig cells, suggesting that they are progenitor Leydig cells (PLCs).

Conclusion

Collectively, we have established the expected characteristics and markers of authentic porcine mGSCs (C1). We found for the first time that, the C2, equivalent to previously claimed porcine mGSCs, are actually progenitor Leydig cells (PLCs). These findings provide new insights into the discrepancies among previous reports and future identification and analyses of testis-derived stem cells.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0931-0) contains supplementary material, which is available to authorized users.

The Modification of Tet1 in Male Germline Stem Cells and Interact with PCNA, HDAC1 to promote their Self-renewal and Proliferation

Epigenetic modification plays key roles in spermatogenesis, especially DNA methylation dynamic is important in sustaining normal spermatogenesis. Ten-eleven translocation 1 (Tet1) is not only a key demethylase, which works in specific gene regions, but also crosstalks with partners to regulate epigenetic progress as protein complexes. Dairy goat is an important livestock in China, while the unstable culture system in vitro inhibits optimization of new dairy goat species. The study of epigenetic modification in male germline stem cells (mGSCs) is beneficial to the optimization of adult stem cell culture system in vitro, and the improvement of sperm quality and breeding of selected livestock. In our study, we not only analyzed the morphology, gene expression, DNA methylation and histone methylation dynamic in mouse Tet1 (mTet1) modified mGSCs, we also analyzed the stemness ability by in vivo transplantation and explored the functional mechanism of Tet1 in dairy goat mGSCs. The results showed mTet1 modified mGSCs had better self-renewal and proliferation ability than wild-type mGSCs, mTet1 could also up-regulate JMJD3 to decrease H3K27me3, which also showed to suppress the MEK-ERK pathway. Furthermore, Co-IP analysis demonstrated that TET1 interact with PCNA and HDAC1 by forming protein complexes to comprehensively regulate dairy goat mGSCs and spermatogenesis.

Modification of Tet1 and histone methylation dynamics in dairy goat male germline stem cells

OBJECTIVES

Tet (ten-eleven translocation) protein 1 is a key enzyme for DNA demethylation, which modulates DNA methylation and gene transcription. DNA methylation and histone methylation are critical elements in self-renewal of male germline stem cells (mGSCs) and spermatogenesis. mGSCs are the only type of adult stem cells able to achieve intergenerational transfer of genetic information, which is accomplished through differentiated sperm cells. However, numerous epigenetic obstacles including incomplete DNA methylation and histone methylation dynamics make establishment of stable livestock mGSC cell lines difficult. The present study was conducted to detect effects of DNA methylation and histone methylation dynamics in dairy goat mGSCs self-renewal and proliferation, through overexpression of Tet1.

MATERIALS AND METHODS

An immortalized dairy goat mGSC cell line bearing mouse Tet1 (mTet1) gene was screened and characteristics of the cells were assayed by quantitative real-time PCR (qRT-PCR), immunofluorescence assay, western blotting, fluorescence activated cell sorting (FACS) and use of the cell counting kit (CCK8) assay.

RESULTS

The screened immortalized dairy goat mGSC cell line bearing mTet1, called mGSC-mTet1 cells was treated with optimal doxycycline (Dox) concentration to maintain Tet1 gene expression. mGSC-mTet1 cells proliferated at a significantly greater rate than wild-type mGSCs, and mGSCs-specific markers such as proliferating cell nuclear antigen (PCNA), cyclinD1 (CCND1), GDNF family receptor alpha 1 (Gfra1) and endogenic Tet1, Tet2 were upregulated. The cells exhibited not only reduction in level of histone methylation but also changes in nuclear location of that methylation marker. While H3K9me3 was uniformly distributed throughout the nucleus of mGSC-mTet1 cells, it was present in only particular locations in mGSCs. H3K27me3 was distributed surrounding the edges of nuclei of mGSC-mTet1 cells, while it was uniformly distributed throughout nuclei of mGSCs. Our results conclusively demonstrate that modification of mGSCs with mTet1 affected mGSC maintenance and seemed to promote establishment of stable goat mGSC cell lines.

CONCLUSIONS

Taken together, our data suggest that Tet1 had novel and dynamic roles for regulating maintenance of pluripotency and proliferation of mGSCs by forming complexes with PCNA and histone methylation dynamics. This may provide new solutions for mGSCs stability and livestock mGSC cell line establishment.

Bovine male germline stem-like cells cultured in serum- and feeder-free medium

Male germline stem cells (mGSCs) presented in male testis are responsible for spermatogenesis during their whole life. However, little information can be found on the culture of bovine mGSCs, and the current culture system needs to be improved. In this study, we compared the effects of several commercial serum-free media and different extra-cellular matrix on the enrichment and cultivation of mGSCs. To find out the best culture condition, the biological characteristics of the cultured cells were evaluated by morphological observation, RT-PCR and immunofluorescent staining. According to the cells' condition in different experiment groups, we found out an efficient cultivation system for bovine mGSCs derived from neonate testis. In this serum- and feeder-free medium, the cultured cells maintained the typical morphology, and expressed specific surface markers of both pluripotent ES cells and mGSCs, including SSEA-1, CD49f, C-MYC, PLZF, GFRα1, LIN28, NANOG, Oct4 and SOX2 in commercial human ESCs medium PeproGrow-hESC + BIO (6-bromoindirubin-3'-oxime). Embryoid bodies, derived from the bovine mGSCs, and were formed by ganging drop culture. The retinoic acid induced bovine mGSCs were positive for Stra8, SCP3, DZAL, EMA1 and VASA, and resembled spermatid cells morphologically. Thus, we found an efficient bovine mGSCs-cultivation system, which is lack in serum and feeder.

Characterization of immortalized dairy goat male germline stem cells (mGSCs)

Male germline stem cells (mGSCs), in charge for the fertility in male testis, are the only kind of adult stem cells that transmit genetic information to next generation, with promising prospects in germplasm resources preservation and optimization, and production of transgenic animals. Mouse male germline stem cell lines have been established and are valuable for studying the mechanisms of spermatogenesis. However, there is a lack of stable mGSC cell lines in livestock, which restricts the progress of transgenic research and related biotechnology. Here, we firstly established an immortalized dairy goat mGSC cell line to study the biological properties and the signaling pathways associated with mGSCs self-renewal and differentiation. The ectopic factors SV40 large T antigen and Bmi1 genes were transduced into dairy goat mGSCs, and the results showed that the proliferation of these cells that were named mGSCs-I-SB was improved significantly. They maintained the typical characteristics including the expression of mGSC markers, and the potential to differentiate into all three germ layers, sperm-like cells in vitro. Additionally, mGSCs-I-SB survived and differentiated into three germ layer cell types when they were transplanted into chicken embryos. Importantly, the cells also survived in mouse spermatogenesis deficiency model testis which seemed to be the golden standard to examine mGSCs. Conclusively, our results demonstrate that mGSCs-I-SB present the characteristics of mGSCs and may promote the future study on goat mGSCs.

Ras/ERK1/2 pathway regulates the self-renewal of dairy goat spermatogonia stem cells

Spermatogonia stem cells (SSCs), also named the male germline stem cells (mGSCs), which is located at the base of the seminiferous tubules of testis, is the basis for generating sperm steadily in male animals. Currently, there are some preliminary study on the self-renewal and differentiation of SSCs, but further mechanism, especially in large animals, has not been clearly understood. Ras/ERK1/2 pathway is widely distributed in multiple cells in vivo. It plays an important role in cell proliferation, differentiation and so on. However, the study on the function for the self-renewal of dairy goats SSCs has not been investigated. In this study, the dairy goat SSCs characterization were evaluated by semi-RT-PCR, alkaline phosphatase (AP) staining, and immunofluorescence staining. Then, Ras/ERK1/2 pathway was blocked by specific MEK1/2 inhibitor PD0325901. We analyzed the proliferation by cell number, cell growth curve, Brdu incorporation assay, and cell cycle analysis. The results showed that the proliferation was significantly inhibited by PD0325901. Cell apoptosis induced by blocking the Ras/ERK1/2 pathway was analyzed by TUNEL. The expression of ETV5 and BCL6B, the downstream gene of Ras/ERK1/2 pathway, was downregulated. This study suggest that the Ras/ERK1/2 pathway plays a critical role in maintaining the self-renewal of dairy goat SSCs via regulation of ETV5 and BCL6B. This study laid a foundation for insights into the mechanism of SSCs self-renewal comprehensively.

The Tet1 and histone methylation expression pattern in dairy goat testis

DNA methylation and histone methylation are critical for mammalian development. Ten-eleven translocation (Tet1), a key regulator of DNA methylation, has been identified as a key enzyme for the activation of DNA demethylation; histone H3 lysine 9 (H3K9) and 27 (H3K27) methylation repress gene expression. Significant progress on the biological functions of Tet proteins has been made in mice and humans. However, their expression pattern and function in the male germ cells in the dairy goat testis are still unclear. The present study described the expression pattern of Tet1, H3K9, and H3K27 in the dairy goat testis and cultured goat spermatogonia stem cells (gSSCs). The results showed that Tet1 was weakly expressed in the dairy goat's testis compared to other organ tissues. Tet1, 5-hydroxymethylcytosine, H3K9, and H3K27 expressions were positive and dynamically changing during spermatogenesis; however, they showed weak expression in neonate stage in vivo. Tet1 and 5-hydroxymethylcytosine showed low expression in gSSCs in vitro in differentiated cultures. These will provide new perspectives for DNA methylation/demethylation and better regulation of epigenetic modifications in gSSCs.

Expression profile of Nanos2 gene in dairy goat and its inhibitory effect on Stra8 during meiosis

OBJECTIVES

Nanos2, an RNA-binding protein, belongs to the Nanos gene-coding family and contains two CCHC zinc-finger motifs. In mouse, it plays a pivotal role in male germ cell development, and self-renewal of spermatogonial stem cells. However, little is known of its expression pattern and functions in dairy goat testis.

MATERIALS AND METHODS

Immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were used to generate the expression profile of Nanos2 in dairy goat testis. Furthermore, its overexpression effects on male germline stem cells (mGSCs) were studied using qRT-PCR, immunofluorescence, dual-luciferase reporter assay and western blotting.

RESULTS

Nanos2 is a conservative gene expressed widely in various tissues, especially in pancreas, and it displays higher expression in adult testes than in other age groups. Overexpression of Nanos2 significantly downregulated meiosis-related genes, including Stra8 and Scp3, which induced inhibition of meiosis. Results from dual-luciferase reporter assay and western blotting indicated that Nanos2 directly downregulated Stra8 in goat GmGSCs.

CONCLUSIONS

Taken together, these results suggest that Nanos2 plays an important role in spermatogonia and that its overexpression restrained meiosis in the dairy goat.

miR-34c enhances mouse spermatogonial stem cells differentiation by targeting Nanos2

miRNAs are expressed in many mammalian cells, acting specific roles in regulating gene expression or mediating special mRNAs cleavage by targeting their 3'-untranslated region (3'UTR). Some miRNAs are essential and important for animal development. However, it is still unclear what the relationship is between miR-34c and mammalian spermatogonial stem cells (SSCs). We found that a conserved microRNA-34c through its target-Nanos2, regulating SSCs' differentiation in mouse. Immunohistochemistry analysis of Nanos2 and miR-34c FISH results revealed the opposite expression trends between them. Seven bioinformatics websites and programs predicted that miR-34c has interaction sites in Nanos2's 3'UTR. Dual-luciferase reporter vector and mutated dual-luciferase reporter vector analysis validated that they are interacted. After transfection miR-34c mimics into mouse SSCs, or miR-34c lentiviral vector in vitro co-cultivation with seminiferous tubules, and Western blot analysis demonstrated that miR-34c over-expression could suppress Nanos2 expression in post-transcription level. Our experiments identified that miR-34c may promote meiosis process by interacting with Nanos2 leading up-regulation of Stra8 in mouse spermatogonial stem cells.

Promyelocytic leukaemia zinc finger maintains self-renewal of male germline stem cells (mGSCs) and its expression pattern in dairy goat testis

OBJECTIVES

Previous studies have shown that promyelocytic leukaemia zinc finger (PLZF) is a spermatogonia-specific transcription factor in the testis, required to regulate self-renewal and maintenance of the spermatogonia stem cell. Up to now, expression and function of PLZF in the goat testis has not been known. The objectives of this study were to investigate PLZF expression pattern in the dairy goat and its effect on male goat germline stem cell (mGSC) self-renewal and differentiation.

MATERIALS AND METHODS

Testis development and expression patterns of PLZF in the dairy goat were analysed by haematoxylin and eosin staining, immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, effects of PLZF overexpression on mGSC self-renewal and differentiation were evaluated by quantitative RT-PCR (QRT-PCR), immunofluorescence and BrdU incorporation assay.

RESULTS

Promyelocytic leukaemia zinc finger was essential for dairy goat testis development and expression of several proliferation and pluripotency-associated proteins including OCT4, C-MYC were upregulated by PLZF overexpression. The study demonstrated that PLZF played a key role in maintaining self-renewal of mGSCs and its overexpression enhanced expression of proliferation-associated genes.

CONCLUSIONS

Promyelocytic leukaemia zinc finger could function in the dairy goat as well as in other species in maintaining self-renewal of germline stem cells and this study provides a model to study the mechanism on self-renewal and differentiation of mGSCs in livestock.

Expression pattern of Ngn3 in dairy goat testis and its function in promoting meiosis by upregulating Stra8

OBJECTIVES

Ngn3 is a typical transcription factor and marker of differentiating spermatogonial stem cells (SSCs) in mouse, belonging to the basic helix-loop-helix (bHLH) family. Its gene is specifically expressed in A type spermatogonia in mouse testis, thus plays a critical role in controlling differentiation of SSCs. However, roles of Ngn3 and its protein in dairy goat testis remain unknown.

MATERIALS AND METHODS

Testis development and expression patterns of Ngn3 were analysed by immunofluorescence and quantitative reverse transcription-polymerase chain reaction (QRT-PCR) in the dairy goat. Furthermore, effects of its overexpression on male germline stem cells (mGSCs) were evaluated by QRT-PCR, immunofluorescence, luciferase reporter assay and western blotting.

RESULTS

Revealed that Ngn3 was expressed more highly during puberty and in the adult than in testis of other ages. Overexpression of Ngn3 promoted expression of meiosis-related gene Stra8 and stem-cell differentiation marker CD117, but suppressed expression of Plzf, a classical marker of SSCs. Furthermore, Ngn3 did not promote expression of Stra8 directly as shown in transcription and translation levels detected by luciferase reporter assay and western blotting.

CONCLUSIONS

Taken together, these results suggest that Ngn3 plays an important role in spermatogenesis and that overexpression of Ngn3 can promote meiosis in testis of the dairy goat.

Effect of vitamin C on growth of caprine spermatogonial stem cells in vitro

The genetic manipulation of spermatogonial stem cells (SSCs) can be used for the production of transgenic animals in a wide range of species. However, this technology is limited by the absence of an ideal culture system in which SSCs can be maintained and proliferated, especially in domestic animals like the goat. The aim of this study therefore was to investigate whether the addition of vitamin C (Vc) in cell culture influences the growth of caprine SSCs. Various concentrations of Vc (0, 5, 10, 25, 40, and 50 μg/mL(-1)) were added to SSC culture media, and their effect on morphology and alkaline phosphatase activity was studied. The number of caprine SSC colonies and area covered by them were measured at 10 days of culture. The expression of various germ cell and somatic cell markers such as VASA, integrins, Oct-4, GATA-4, α-SMA, vimentin, and Thy-1 was studied to identify the proliferated cells using immunostaining analyses. Further, the intracellular reactive oxygen species (ROS) level was measured at the 3rd, 6th, and 9th day after culture, and expression of Bax, Bcl-2, and P53, factors involved in the regulation of apoptosis, were analyzed on the 7th day after culture using reverse transcription polymerase chain reaction and quantitative real-time polymerase chain reaction. The results showed that the SSCs formed compact colonies and had unclear borders in the different Vc-supplemented groups at 10 days, and there were no major morphologic differences between the groups. The number and area of colonies were both the highest in the 40 μg/mL(-1) Vc group. Differential expression of markers for germ cells, undifferentiated spermatogonia, and testis somatic cells was observed. Cultured germ cell clumps were found to have alkaline phosphatase activity regardless of the Vc dose. The number of Thy-1- and Oct-4-positive cells was the most in the 40 μg/mL(-1) Vc group. Moreover, the level of ROS was dependent on the Vc dose and culture time. The Vc dose 40 μg/mL(-1) was found to be optimum with regard to decreasing ROS generation, and increasing the expression of the antiapoptotic gene Bcl-2 and decreasing the expression of the proapoptotic genes Bax and P53. In conclusion, the addition of 40 μg/mL(-1) Vc can maintain a certain physiological level of ROS, trigger the expression of the antiapoptosis gene Bcl-2, suppress the proapoptotic gene P53 and Bax pathway, and further promote the proliferation of caprine SSCs in vitro.

Expression pattern of Boule in dairy goat testis and its function in promoting the meiosis in male germline stem cells (mGSCs)

Boule is a conserved gene in meiosis, which encodes RNA binding protein required for spermatocyte meiosis. Deletion of Boule was found to block meiosis in spermatogenesis, which contributes to infertility. Up to date, the expression and function of Boule in the goat testis are not known. The objectives of this study were to investigate the expression pattern of Boule in dairy goat testis and their function in male germline stem cells (mGSCs). The results first revealed that the expression level of Boule in adult testes was significantly higher than younger and immature goats, and azoospermia and male intersex testis. Over-expression of Boule promoted the expression of meiosis-related genes in dairy goat mGSCs. The expression of Stra8 was up-regulated by over-expression of Boule analyzed by Western blotting and Luciferase reporter assay. While, Cdc25a, the downstream regulator of Boule, was found not to affect the expression of Stra8, and our data illustrated that Cdc25a did not regulate meiosis via Stra8. The expression of Stra8 and Boule was up-regulated by RA induction. Taken together, results suggest the Boule plays an important role in dairy goat spermatogenesis and that over-expression of Boule may promote spermatogenesis and meiosis in dairy goat.

Pluripotent cells in farm animals: state of the art and future perspectives

Pluripotent cells, such as embryonic stem (ES) cells, embryonic germ cells and embryonic carcinoma cells are a unique type of cell because they remain undifferentiated indefinitely in in vitro culture, show self-renewal and possess the ability to differentiate into derivatives of the three germ layers. These capabilities make them a unique in vitro model for studying development, differentiation and for targeted modification of the genome. True pluripotent ESCs have only been described in the laboratory mouse and rat. However, rodent physiology and anatomy differ substantially from that of humans, detracting from the value of the rodent model for studies of human diseases and the development of cellular therapies in regenerative medicine. Recently, progress in the isolation of pluripotent cells in farm animals has been made and new technologies for reprogramming of somatic cells into a pluripotent state have been developed. Prior to clinical application of therapeutic cells differentiated from pluripotent stem cells in human patients, their survival and the absence of tumourigenic potential must be assessed in suitable preclinical large animal models. The establishment of pluripotent cell lines in farm animals may provide new opportunities for the production of transgenic animals, would facilitate development and validation of large animal models for evaluating ESC-based therapies and would thus contribute to the improvement of human and animal health. This review summarises the recent progress in the derivation of pluripotent and reprogrammed cells from farm animals. We refer to our recent review on this area, to which this article is complementary.

The effects of Nanos2 on Boule and Stra8 in male germline stem cells (mGSCs)

The mitosis-meiosis switch is a key event in the differentiation of germ cells. Meiosis is important in development biology, however, it has not been clear what is the regulation mechanism in mammals. Our previous study showed that Boule could activate Stra8 directly and result in the meiosis initiation of dairy goat male germline stem cells (mGSCs). Nanos2, a RNA-binding protein, plays critical roles in the suppression of meiosis by preventing Stra8 expression and maintain the male germ cell development. The main purpose of this study was to explore whether Nanos2 represses Stra8 transcription through Boule or not. We found ectopic over-expression of Nanos2 in GC-1 and mGSCs down-regulated Stra8 transcription and translation, and Boule expression was not affected. It was in consistent with our expectation that RA could up-regulate Boule and Stra8 expression, but down-regulate Nanos2 expression in mGSCs. In dairy goat, the expression levels of Boule and Stra8 would rise with the increase of age, but the expression level of Nanos2 in 90 dpp and adult testis had not shown a clear change. In conclusion, Nanos2 represses Stra8 expression but not through Boule in dairy goat mGSCs.

miR-34c works downstream of p53 leading to dairy goat male germline stem-cell (mGSCs) apoptosis

OBJECTIVES

Recent lines of evidence have indicated that miR-34c can play important roles in regulation of the cell cycle, cell senescence and apoptosis of mouse and human tumour cells, spermatogenesis, and male germ-cell apoptosis. However, there is little information on the effects of miR-34c on proliferation and apoptosis of livestock male germ cells. The dairy goat is a convenient domestic species for biological investigation and application. The purpose of this study was to investigate the effects of miR-34c on apoptosis and proliferation of dairy goat male germline stem cells (mGSCs), as well as to determine the relationship between p53 and miR-34c in this species.

MATERIALS AND METHODS

Morphological observation, miRNA in situ hybridisation (ISH), bromodeoxyuridine staining, flow cytometry, quantitative-RT-PCR (Q-RT-PCR) and western blotting were utilized to ascertain apoptosis and proliferation of mGSCs, through transfection of miR-34c mimics (miR-34c), miR-34c inhibitor (anti-miR-34c), miR-34c mimics and inhibitors co-transfected (mixture) compared to control groups.

RESULTS

Results manifested that miR-34c over-expression promoted mGSCs apoptosis and suppressed their proliferation. Simultaneously, a variety of apoptosis-related gene expression was increased while some proliferation-related genes were downregulated. Accordingly, miR-34c promoted apoptosis in mGSCs and reduced their proliferation; moreover, expression of miR-34c was p53-dependent.

CONCLUSIONS

This study is the first to provide a model for study of miRNAs and mechanisms of proliferation and apoptosis in male dairy goat germ cells.

Optimization of the conditions of isolation and culture of dairy goat male germline stem cells (mGSC)

Male germline stem cells (mGSC) reside in the basement of seminiferous tubules of the testis and have the capacity of self-renewal and differentiation into sperm throughout the life of animals. Reports on mice and human mGSC have demonstrated that mGSC are an unlimited resource of pluripotent stem cells for sperm production. The conditions of isolation and culture of mouse and human mGSC are well developed; however, the systematic culture conditions of dairy goat mGSC are still deficient although there have been several reports of successful cultures. With the present research, several key elements of isolation and culture of dairy goat mGSC have been determined. Details for the conditions of isolation of dairy testicular spermatogonium cells were optimized, and effects of several extracellular matrix types, ages of dairy goat, and cytokines on enrichment and culture of mGSC were compared. Biological characteristics of the cells were also evaluated by RT-PCR and immunofluorescent staining. The results indicated there is one kind of enzyme cocktail (CTHD (1mg/ml collagenase, 10μg/ml DNase, 1mg/ml hyaluronidase and 1mg/ml trypsin) combined TD (0.25% trypsin and 10mg/ml DNaseI)) that can be used to successfully isolate dairy goat testicular spermatogonium cells efficiently; and fibronectin as well as laminin were efficient extracellular matrix to enrich mGSC among the extracellular matrix types evaluated. Age of dairy goat clearly influenced the cultures of dairy goat mGSC with the efficiency of establishment of an mGSC line being greater if the age of the dairy goat is younger. Some cytokines e.g. BIO (A GSK3 inhibitor, 6-bromoindirubin-3'-oxime) and basic fibroblast growth factor (bFGF) acted positively on the maintenance of proliferation and pluripotency of mGSC. Leukemia inhibitory factor (LIF) might, however, inhibit the proliferation of dairy goat mGSC. These cultured mGSC maintained similar characteristics as mouse and human mGSC. These results provide an efficient system to isolate and culture of dairy goat mGSC.