Proliferation in culture of primordial germ cells derived from embryonic stem cell: induction by retinoic acid

Melatonin promotes the proliferation of primordial germ cell-like cells derived from porcine skin-derived stem cells: A mechanistic analysis

In vitro differentiation of stem cells into functional gametes remains of great interest in the biomedical field. Skin-derived stem cells (SDSCs) are an adult stem cells that provides a wide range of clinical applications without inherent ethical restrictions. In this paper, porcine SDSCs were successfully differentiated into primordial germ cell-like cells (PGCLCs) in conditioned media. The PGCLCs were characterized in terms of cell morphology, marker gene expression, and epigenetic properties. Furthermore, we also found that 25 μM melatonin (MLT) significantly increased the proliferation of the SDSC-derived PGCLCs while acting through the MLT receptor type 1 (MT1). RNA-seq results found the mitogen-activated protein kinase (MAPK) signaling pathway was more active when PGCLCs were cultured with MLT. Moreover, the effect of MLT was attenuated by the use of S26131 (MT1 antagonist), crenolanib (platelet-derived growth factor receptor inhibitor), U0126 (mitogen-activated protein kinase kinase inhibitor), or CCG-1423 (serum response factor transcription inhibitor), suggesting that MLT promotes the proliferation processes through the MAPK pathway. Taken together, this study highlights the role of MLT in promoting PGCLCs proliferation. Importantly, this study provides a suitable in vitro model for use in translational studies and could help to answer numerous remaining questions related to germ cell physiology.

The proliferation role of LH on porcine primordial germ cell-like cells (pPGCLCs) through ceRNA network construction

BACKGROUND

The transdifferentiation of skin-derived stem cells (SDSCs) into primordial germ cell-like cells (PGCLCs) is one of the major breakthroughs in the field of stem cells research in recent years. This technology provides a new theoretical basis for the treatment of human infertility. However, the transdifferentiation efficiency of SDSCs to PGCLCs is very low, and scientists are still exploring ways to improve this efficiency or promote the proliferation of PGCLCs. This study aims to investigate the molecular mechanism of luteinising hormone (LH) to enhance porcine PGCLCs (pPGCLCs) proliferation.

RESULTS

In this study, we dissected the proliferation regulatory network of pPGCLCs by whole transcriptome sequencing, and the results showed that the pituitary-secreted reproductive hormone LH significantly promoted the proliferation of pPGCLCs. We combined whole transcriptome sequencing and related validation experiments to explore the mechanism of LH on the proliferation of pPGCLCs, and found that LH could affect the expression of Hippo signalling pathway-related mRNAs, miRNAs and lncRNAs in pPGCLCs.

CONCLUSIONS

For the first time, we found that LH promotes pPGCLCs proliferation through the competing endogenous RNA (ceRNA) regulatory networks and Hippo signalling pathway. This finding may help to elucidate the molecular mechanism by which LH promotes pPGCLCs proliferation.

In Utero Programming of Testicular Cancer

It is well established that the intrauterine biological environment plays important roles in fetal development. In this review, we re-visit the hypothesis that testicular germ cell cancer (TGCC), especially in adolescents and young adults, has been programmed in utero. The origin for extreme in utero environments is mostly maternal driven and may be due to nutritional, physical and psychological stressful conditions that alter the optimal molecular and biophysical in utero environments. Moreover, precursors for TGCC may originate as early as during fertilization or implantation of the blastocyst. Further investigations of human developmental biology, both in vivo and in vitro, are needed in order to establish better understanding of in utero programming of future wellbeing or diseases.

Derivation and propagation of spermatogonial stem cells from human pluripotent cells

OBJECTIVES

This study is designed to generate and propagate human spermatogonial stem cells (SSCs) derived from human pluripotent stem cells (hPSCs).

METHODS

hPSCs were differentiated into SSC-like cells (SSCLCs) by a three-step strategy. The biological characteristics of SSCLCs were detected by immunostaining with antibodies against SSC markers. The ability of self-renewal was measured by propagating for a long time and still maintaining SSCs morphological property. The differentiation potential of SSCLCs was determined by the generation of spermatocytes and haploid cells, which were identified by immunostaining and flow cytometry. The transcriptome analysis of SSCLCs was performed by RNA sequencing. The biological function of SSCLCs was assessed by xeno-transplantation into busulfan-treated mouse testes.

RESULTS

SSCLCs were efficiently generated by a 3-step strategy. The SSCLCs displayed a grape-like morphology and expressed SSC markers. Moreover, SSCLCs could be propagated for approximately 4 months and still maintained their morphological properties. Furthermore, SSCLCs could differentiate into spermatocytes and haploid cells. In addition, SSCLCs displayed a similar gene expression pattern as human GPR125⁺ spermatogonia derived from human testicular tissues. And more, SSCLCs could survive and home at the base membrane of seminiferous tubules.

CONCLUSION

SSCLCs were successfully derived from hPSCs and propagated for a long time. The SSCLCs resembled their counterpart human GPR125⁺ spermatogonia, as evidenced by the grape-like morphology, transcriptome, homing, and functional characteristics. Therefore, hPSC-derived SSCLCs may provide a reliable cell source for studying human SSCs biological properties, disease modeling, and drug toxicity screening.

Stem Cells as a Resource for Treatment of Infertility-related Diseases

Worldwide, infertility affects 8-12% of couples of reproductive age and has become a common problem. There are many ways to treat infertility, including medication, intrauterine insemination, and in vitro fertilization. In recent years, stem-cell therapy has raised new hope in the field of reproductive disability management. Stem cells are self-renewing, self-replicating undifferentiated cells that are capable of producing specialized cells under appropriate conditions. They exist throughout a human’s embryo, fetal, and adult stages and can proliferate into different cells. While many issues remain to be addressed concerning stem cells, stem cells have undeniably opened up new ways to treat infertility. In this review, we describe past, present, and future strategies for the use of stem cells in reproductive medicine

BMP4 and Neuregulin regulate the direction of mouse neural crest cell differentiation

The neural crest is a transient embryonic tissue that initially generates neural crest stem cells, which then migrate throughout the body to give rise to a variety of mature tissues. It was proposed that the fate of neural crest cells is gradually determined via environmental cues from the surrounding tissues. In the present study, neural crest cells were isolated and identified from mouse embryos. Bone morphogenetic protein 4 (BMP4) and Neuregulin (NRG) were employed to induce the differentiation of neural crest cells. Treatment with BMP4 revealed neuron-associated differentiation; cells treated with NRG exhibited differentiation into the Schwann cell lineage, a type of glia. Soft agar clonogenic and neurosphere formation assays were conducted to investigate the effects of N-Myc (MYCN) overexpression in neural crest cells; the number of colonies and neurospheres notably increased after 14 days. These findings demonstrated that the direction of cell differentiation may be affected by altering the factors present in the surrounding environment. In addition, MYCN may serve a key role in regulating neural crest cell differentiation.

RA promotes proliferation of primordial germ cell-like cells differentiated from porcine skin-derived stem cells

Previous studies have shown that primordial germ cell-like cells (PGCLCs) can be obtained from human, porcine and mouse skin-derived stem cells (SDSCs). In this paper, we found retinoic acid (RA), the active derivative of vitamin A, accelerated the growth of porcine primordial germ cells (pPGCs) and porcine PGCLCs (pPGCLCs) which were derived from porcine SDSCs (pSDSCs). Moreover, flow cytometry results revealed that the proliferation promoting effect of RA was attenuated by U0126, a specific inhibitor of extracellular signal-regulated kinase (ERK). Western blot analysis showed the protein level of ERK, phosphorylated ERK, cyclin D1 (CCND1), and cyclin-dependent kinase 2 (CDK2) increased after stimulation with RA, and this effect could also be abolished by U0126. Our data revealed that ablation of ERK expression by U0126 should significantly decrease proliferation of pPGCLCS. This reduction was because CCND1 and CDK2 proteins level decrease and subsequently the pPGCLCs were arrested in the G0/G1 phase. In addition, we also confirmed RA indeed promoted the proliferation of pPGCs isolated from porcine fetal genital ridges in vitro. Furthermore, our data indicated that DNA methylation pattern were changed in pPGCLCs and this pattern were more similar to pPGCs.

Interaction of the primordial germ cell-specific protein C2EIP with PTCH2 directs differentiation of embryonic stem cells via HH signaling activation

Although many marker genes for germ cell differentiation have been identified, genes that specifically regulate primordial germ cell (PGC) generation are more difficult to determine. In the current study, we confirmed that C2EIP is a PGC marker gene that regulates differentiation by influencing the expression of pluripotency-associated genes such as Oct4 and Sox2. Knockout of C2EIP during embryonic development reduced PGC generation efficiency 1.5-fold, whereas C2EIP overexpression nearly doubled the generation efficiency both in vitro and in vivo. C2EIP encodes a cytoplasmic protein that interacted with PTCH2 at the intracellular membrane, promoted PTCH2 ubiquitination, activated the Hedgehog (HH) signaling pathway via competitive inhibition of the GPCR-like protein SMO, and positively regulated PGC generation. Activation and expression of C2EIP are regulated by the transcription factor STAT1, histone acetylation, and promoter methylation. Our data suggest that C2EIP is a novel, specific indicator of PGC generation whose gene product regulates embryonic stem cell differentiation by activating the HH signaling pathway via PTCH2 modification.

Embryonic stem cell derived germ cells induce spermatogenesis after transplantation into the testes of an adult mouse azoospermia model

The present study aimed to: (i) identify the exogenous factors that allow in vitro differentiation of mouse spermatogonial stem cells (SSCs) from embryonic stem cells (ESCs); (ii) evaluate the effects of Sertoli cells in SSC enrichment; and (iii) assess the success of transplantation using in vitro differentiated SSCs in a mouse busulfan-treated azoospermia model. A 1-day-old embryoid body (EB) received 5 ng/ml of bone morphogenetic protein 4 (BMP4) for 4 days, 3 µM retinoic acid (RA) in a SIM mouse embryo-derived thioguanine and ouabain resistant (STO) co-culture system for 7 days, and was subsequently co-cultured for 2 days with Sertoli cells in the presence or absence of a leukaemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF) and RA composition, and in the presence of these factors in simple culture medium. Higher viability, proliferation and germ cell gene expression were seen in the presence of the LIF, bFGF and RA composition, on top of Sertoli cells. Immunocytochemistry results showed higher CDH1 expression in this group. Sertoli co-culture had no effects on SSC proliferation. Eight weeks after transplantation, injected cells were observed at the base of the seminiferous tubules and in the recipient testes. The number of spermatogonia and the mass of the testes were higher in transplanted testes relative to the control group. It seems that transplantation of these cells can be useful in infertility treatment.