HST-1/FGF-4 gene activation induces spermatogenesis and prevents adriamycin-induced testicular toxicity

Activin and BMP Signalling in Human Testicular Cancer Cell Lines, and a Role for the Nucleocytoplasmic Transport Protein Importin-5 in their Crosstalk

Testicular germ cell tumours (TGCTs) are the most common malignancy in young men. Originating from foetal testicular germ cells that fail to differentiate correctly, TGCTs appear after puberty as germ cell neoplasia in situ cells that transform through unknown mechanisms into distinct seminoma and non-seminoma tumour types. A balance between activin and BMP signalling may influence TGCT emergence and progression, and we investigated this using human cell line models of seminoma (TCam-2) and non-seminoma (NT2/D1). Activin A- and BMP4-regulated transcripts measured at 6 h post-treatment by RNA-sequencing revealed fewer altered transcripts in TCam-2 cells but a greater responsiveness to activin A, while BMP4 altered more transcripts in NT2/D1 cells. Activin significantly elevated transcripts linked to pluripotency, cancer, TGF-β, Notch, p53, and Hippo signalling in both lines, whereas BMP4 altered TGF-β, pluripotency, Hippo and Wnt signalling components. Dose-dependent antagonism of BMP4 signalling by activin A in TCam-2 cells demonstrated signalling crosstalk between these two TGF-β superfamily arms. Levels of the nuclear transport protein, IPO5, implicated in BMP4 and WNT signalling, are highly regulated in the foetal mouse germline. IPO5 knockdown in TCam-2 cells using siRNA blunted BMP4-induced transcript changes, indicating that IPO5 levels could determine TGF-β signalling pathway outcomes in TGCTs.

The potential of sertoli cells (SCs) derived exosomes and its therapeutic efficacy in male reproductive disorders

In the male reproductive system, seminiferous tubules in testis are lined by a complex stratified epithelium containing two distinct populations of cells, spermatogenic cells that develop into spermatozoa, and sertoli cells (SCs) that mainly support and nourish spermatogenic cell lineage as well as exerting powerful effect on men reproductive capacity. Different varieties of proteins, hormones, exosomes and growth factors are secreted by SCs. There are different kinds of junctions found between SCs called BTB. It was elucidated that complete absence of BTB or its dysfunction leads to infertility. To promote spermatogenesis, crosstalk of SCs with spermatogenic cells plays an important role. The ability of SCs to support germ cell productivity and development is related to its various products carrying out several functions. Exosomes (EXOs) are one of the main EVs with 30-100 nm size generating from endocytic pathway. They are produced in different parts of male reproductive system including epididymis, prostate and SCs. The most prominent characteristics of SC-based exosomes is considered mutual interaction of sertoli cells with spermatogonial stem cells and Leydig cells mainly through establishment of intercellular communication. Exosomes have gotten a lot of interest because of their role in pathobiological processes and as a cell free therapy which led to developing multiple exosome isolation methods based on different principles. Transmission of nucleic acids, proteins, and growth factors via SC-based exosomes and exosomal miRNAs are proved to have potential to be valuable biomarkers in male reproductive disease. Among testicular abnormalities, non-obstructive azoospermia and testicular cancer have been more contributed with SCs performance. The identification of key proteins and miRNAs involved in the signaling pathways related with spermatogenesis, can serve as diagnostic and regenerative targets in male infertility.

Dysregulation of Notch-FGF signaling axis in germ cells results in cystic dilation of the rete testis in mice

Numb (Nb) and Numb-like (Nbl) are functionally redundant adaptor proteins that critically regulate cell fate and morphogenesis in a variety of organs. We selectively deleted Nb and Nbl in testicular germ cells by breeding Nb/Nbl floxed mice with a transgenic mouse line Tex101-Cre. The mutant mice developed unilateral or bilateral cystic dilation in the rete testis (RT). Dye trace indicated partial blockages in the testicular hilum. Morphological and immunohistochemical evaluations revealed that the lining epithelium of the cysts possessed similar characteristics of RT epithelium, suggesting that the cyst originated from dilation of the RT lumen. Spermatogenesis and the efferent ducts were unaffected. In comparisons of isolated germ cells from mutants to control mice, the Notch activity considerably increased and the expression of Notch target gene Hey1 significantly elevated. Further studies identified that germ cell Fgf4 expression negatively correlated the Notch activity and demonstrated that blockade of FGF receptors mediated FGF4 signaling induced enlargement of the RT lumen in vitro. The crucial role of the FGF4 signaling in modulation of RT development was verified by the selective germ cell Fgf4 ablation, which displayed a phenotype similar to that of germ cell Nb/Nbl null mutant males. These findings indicate that aberrant over-activation of the Notch signaling in germ cells due to Nb/Nbl abrogation impairs the RT development, which is through the suppressing germ cell Fgf4 expression. The present study uncovers the presence of a lumicrine signal pathway in which secreted/diffusible protein FGF4 produced by germ cells is essential for normal RT development.

The testicular protective effects of standardised hydroalcoholic extract of Ziziphus jujuba Mill against adriamycin-induced toxicity

In this study, because of the anti-inflammatory and antioxidant effect of the Ziziphus jujuba (ZJ), we assessed the protective properties of the ZJ extract against testis toxicity caused by Adriamycin in the rat. Twenty rats were grouped into (a) control, (b) Adriamycin, (c) ZJ group and (d) treatment group in which Adriamycin was administrated and the ZJ hydroalcoholic extract was used for three weeks. On the 21st day, two testes were removed to determine the oxidation markers and pathological evaluation. The levels of sex hormones were determined. Epididymis also was crushed, and its spermatozoa were evaluated as concentration, motility and normality. Adriamycin increased oxidative stress markers as well as Luteinising hormone, and follicle-stimulating hormone and decreased testosterone levels compared to control. In the treated group, the levels of the above markers improved. The decreased number and motility of spermatozoa in treatment group increased, and the increased rate of abnormal spermatozoa in this group decreased. Pathological evaluations also show the healing process of damaged testicular tissue in the group receiving the ZJ extract. The ZJ extract relatively improves oxidative stress, sperm characteristics, hormonal alternation and pathological changes. These findings reveal the probable role of ZJ effective compounds in repairing tissue damage.

FGF9 promotes mouse spermatogonial stem cell proliferation mediated by p38 MAPK signalling

Objectives

Fibroblast growth factor 9 (FGF9) is expressed by somatic cells in the seminiferous tubules, yet little information exists about its role in regulating spermatogonial stem cells (SSCs).

Materials and Methods

Fgf9 overexpression lentivirus was injected into mouse testes, and PLZF immunostaining was performed to investigate the effect of FGF9 on spermatogonia in vivo. Effect of FGF9 on SSCs was detected by transplanting cultured germ cells into tubules of testes. RNA‐seq of bulk RNA and single cell was performed to explore FGF9 working mechanisms. SB203580 was used to disrupt p38 MAPK pathway. p38 MAPK protein expression was detected by Western blot and qPCR was performed to determine different gene expression. Small interfering RNA (siRNA) was used to knock down Etv5 gene expression in germ cells.

Results

Overexpression of Fgf9 in vivo resulted in arrested spermatogenesis and accumulation of undifferentiated spermatogonia. Exposure of germ cell cultures to FGF9 resulted in larger numbers of SSCs over time. Inhibition of p38 MAPK phosphorylation negated the SSC growth advantage provided by FGF9. Etv5 and Bcl6b gene expressions were enhanced by FGF9 treatment. Gene knockdown of Etv5 disrupted the growth effect of FGF9 in cultured SSCs along with downstream expression of Bcl6b.

Conclusions

Taken together, these data indicate that FGF9 is an important regulator of SSC proliferation, operating through p38 MAPK phosphorylation and upregulating Etv5 and Bcl6b in turn.

Homology modeling and virtual screening studies of FGF-7 protein-a structure-based approach to design new molecules against tumor angiogenesis

Keratinocyte growth factor (KGF) protein is a member of the fibroblast growth factor (FGF) family, which is also known as FGF-7. The FGF-7 plays an important role in tumor angiogenesis. In the present work, FGF-7 is treated as a potential therapeutic target to prevent angiogenesis in cancerous tissue. Computational techniques are applied to evaluate and validate the 3D structure of FGF-7 protein. The active site region of the FGF-7 protein is identified based on hydrophobicity calculations using CASTp and Q-site Finder active site prediction tools. The protein-protein docking study of FGF-7 with its natural receptor FGFR2b is carried out to confirm the active site region in FGF-7. The amino acid residues Asp34, Arg67, Glu116, and Thr194 in FGF-7 interact with the receptor protein (FGFR2b). A grid is generated at the active site region of FGF-7 using Glide module of Schrödinger suite. Subsequently, a virtual screening study is carried out at the active site using small molecular structural databases to identify the ligand molecules. The binding interactions of the ligand molecules, with piperazine moiety as a pharmacophore, are observed at Arg67 and Glu149 residues of the FGF-7 protein. The identified ligand molecules against the FGF-7 protein show permissible pharmacokinetic properties (ADME). The ligand molecules with good docking scores and satisfactory pharmacokinetic properties are prioritized and identified as novel ligands for the FGF-7 protein in cancer therapy.

Protective effect of FGF21 on type 1 diabetes-induced testicular apoptotic cell death probably via both mitochondrial- and endoplasmic reticulum stress-dependent pathways in the mouse model

Fibroblast growth factor 21 (FGF21) is a novel member identified and was reported to express predominantly in pancreas, liver and adipose tissue, and relatively less in other organs, such as the testis. However, the role of FGF21 in the testis has never been addressed. The present study examined FGF21 expression at mRNA level by real-time RT-PCR assay in the testis of fasting and non-fasting mice or mice with type 1 diabetes that was induced with streptozotocin. We also examined the effect of Fgf21 gene deletion or supplementation of the exogenous FGF21 on the testicular apoptotic cell death spontaneously or induced by type 1 diabetes in FGF21 knockout (FGF21-KO) mice. Deletion of Fgf21 gene does not affect testicular cell proliferation, but significantly increases the spontaneous incidence of testicular TUNEL positive cells with increases in the Bax/Bcl2 expression ratio and apoptosis-inducing factor (AIF) expression. Diabetes induced significant increases in testicular TUNEL positive cells, Bax/Bcl2 expression ratio, AIF expression, CHOP and cleaved caspase-12 expression, and oxidative damage, but did not change the expression of cleaved caspase-3 and caspase-8. Deletion of Fgf21 gene also significantly enhances diabetes-induced TUNEL positive cells along with the increased expression of Bax/Bcl2 ratio, AIF, CHOP, cleaved caspase-12, and oxidative damage, which was significantly prevented by the supplementation of exogenous FGF21. These results suggest that Fgf21 gene may involve in maintaining normal spermatogenesis and also protect the germ cells from diabetes-induced apoptotic cell death probably via the prevention of diabetes-induced oxidative damage.

The roles of fibroblast growth factors in the testicular development and tumor

Fibroblast growth factors (FGFs) are classically known as hormonal factors and recent studies have revealed that FGFs have a key role in regulating growth and development of several reproductive organs, including the testis. The testis is mainly consisted of germ cells, Sertoli cells and Leydig cells to develop and maintain the male phenotype and reproduction. This review summarizes the structure and fuctions of testis, the roles of FGFs on testicular development and potential involvement in testicular tumor and its regulatory mechanism. Among 23 members of FGFs, the FGF-1, FGF-2, FGF-4, FGF-8, FGF-9, and FGF-21 were involved and describe in details. Understanding the roles and mechanism of FGFs is the foundation to modeling testicular development and treatments in testicular disease. Therefore, in the last part, the potential therapy with FGFs for the testis of cancer and diabetes was also discussed.

FGF2 mediates mouse spermatogonial stem cell self-renewal via upregulation of Etv5 and Bcl6b through MAP2K1 activation

Fibroblast growth factor 2 (FGF2) and glial cell line-derived neurotrophic factor (GDNF) are required to recapitulate spermatogonial stem cell (SSC) self-renewal in vitro. Although studies have revealed the role of the GDNF signaling pathway in SSCs, little is known about how FGF2 is involved. In the present study, we assessed the role of the FGF2 signaling pathway using a mouse germline stem (GS) cell culture system that allows in vitro expansion of SSCs. Adding GDNF or FGF2 induced phosphorylation of MAPK1/3, and adding the MAP2K1 inhibitor PD0325091 reduced GS cell proliferation and MAPK1/3 phosphorylation. Moreover, GS cells transfected with an activated form of Map2k1 not only upregulated Etv5 and Bcl6b gene expression, but also proliferated in an FGF2-independent manner, suggesting that they act downstream of MAP2K1 signaling to drive SSC self-renewal. Although GS cells transfected with Map2k1, Etv5 or Bcl6b showed normal spermatogonial markers, transplanting GS cells expressing Bcl6b into infertile mouse testes resulted in the formation of a germ cell tumor, suggesting that excessive self-renewal signals causes tumorigenic conversion. These results show that FGF2 depends on MAP2K1 signaling to drive SSC self-renewal via upregulation of the Etv5 and Bcl6b genes.

Proanthocyanidins produce significant attenuation of doxorubicin-induced mutagenicity via suppression of oxidative stress

This study has been initiated to determine whether proanthocyanidins can protect against doxorubicin-induced mutagenicity in mice and to elucidate the potential mechanism of this protection. Pretreatment of mice with proanthocyanidins (100 mg/kg/day, orally) for 7 days and simultaneously with doxorubicin (12 mg/kg, i.p.) for another day, significantly reduced the frequency of bone marrow DNA strand breaks and micronucleated polychromatic erythrocytes compared to doxorubicin-treated mice alone. Furthermore, proanthocyanidins caused a reduction in bone marrow suppression induced by doxorubicin treatment. In male germline, orally administration of proanthocyanidins (100 mg/kg/day, orally) for 7 consecutive days before and 7 consecutive days after treatment with doxorubicin (12 mg/kg, i.p.), significantly elevated the levels of sperm count and motility reduced by doxorubicin treatment. Furthermore, proanthocyanidins significantly decreased the elevated levels of spermatogonial and spermatocyte chromosomal aberrations and sperm head abnormality induced by doxorubicin. Prior administration of proanthocyanidins ahead of doxorubicin reduced the doxorubicin induced testicular lipid peroxidation and prevented the reduction in testicular non-protein sulfhydryl significantly. Conclusively, this study provides for the first time that proanthocyanidins have a protective role in the abatement of doxorubicin-induced mutagenesis and cell proliferation changes in germinal cells of mice that reside, at least in part, in their radical scavenger activity. Therefore, proanthocyanidins can be a promising chemopreventive agent to avert secondary malignancy and abnormal reproductive outcomes risks in cancer patients receiving doxorubicin-involved treatment.

Pleiotropic function of FGF-4: its role in development and stem cells

Fibroblast growth factors (FGFs) were initially recognized as fibroblast-specific growth factor, and it is now apparent that these growth factors regulate multiple biological functions. The diversity of FGFs function is paralleled by the emerging diversity of interactions between FGF ligands and their receptors. FGF-4 is a member of the FGF superfamily and is a mitogen exhibiting strong action on numerous different cell types. It plays a role in various stages of development and morphogenesis, as well as in a variety of biological processes. Recent studies reveal the molecular mechanisms of FGF-4 gene regulation in mammalian cells, which is involved in the developmental process. Furthermore, FGF-4 also acts on the regulation of proliferation and differentiation in embryonic stem cells and tissue stem cells. In this review, we focus on the diverse biological functions of FGF-4 in the developmental process and also discuss its putative roles in stem cell biology.

FGF-4 regulates neural progenitor cell proliferation and neuronal differentiation

The FGF-4 (fibroblast growth factor 4, known as HST-1) protein is an important mitogen for a variety of cell types. However, only limited information is available concerning tissue distribution and the biological role of FGF-4 in the brain. In situ hybridization analysis revealed localization of mouse Fgf-4 mRNA in the normal postnatal mouse hippocampus, subventricular zone (SVZ), and the rostral migratory stream where new neurons generate, migrate, and become incorporated into the functional circuitry of the brain. We also investigated whether FGF-4 could promote both proliferation and differentiation of the neural progenitor cells by using an in vitro neurosphere assay. The addition of recombinant FGF-4 generated large proliferative spheres that have a multipotent differentiation ability. Furthermore, recombinant FGF-4 significantly promotes neuronal differentiation in attached clonal neurosphere culture. These findings suggest that FGF-4 has an ability to promote neural stem cell proliferation and neuronal differentiation in the postnatal brain.

Regulation of testicular function by cell-to-cell interaction

Cell-to-cell interactions in the testis play important roles in regulating testicular function. Investigating the mechanism of such interactions is essential to elucidate the cause of spermatogenic dysfunction and to create a new treatment. (Reprod Med Biol 2006; 5: 9-17).

Cytokines and junction restructuring during spermatogenesis—a lesson to learn from the testis

In the mammalian testis, preleptotene and leptotene spermatocytes residing in the basal compartment of the seminiferous epithelium must traverse the blood-testis barrier (BTB) at late stage VIII through early stage IX of the epithelial cycle during spermatogenesis, entering the adluminal compartment for further development. However, until recently the regulatory mechanisms that regulate BTB dynamics remained largely unknown. We provide a critical review regarding the significance of cytokines in regulating the 'opening' and 'closing' of the BTB. We also discuss how cytokines may be working in concert with adaptors that selectively govern the downstream signaling pathways. This process, in turn, regulates the dynamics of either Sertoli-Sertoli tight junction (TJ), Sertoli-germ cell adherens junction (AJ), or both junction types in the epithelium, thereby permitting TJ opening without compromising AJs, and vice versa. We also discuss how adaptors alter their protein-protein association with the integral membrane proteins at the cell-cell interface via changes in their phosphorylation status, thereby altering adhesion function at AJ. These findings illustrate that the testis is a novel in vivo model to study the biology of junction restructuring. Furthermore, a molecular model is presented regarding how cytokines selectively regulate TJ/AJ restructuring in the epithelium during spermatogenesis.

Antisense oligodeoxynucleotide against HST-1/FGF-4 suppresses tumorigenicity of an orthotopic model for human germ cell tumor in nude mice

BACKGROUND

Overexpression of the fibroblast growth factor HST-1/FGF-4 gene is thought to mediate growth properties and malignancy in human testicular germ cell tumors. We have studied the effect that an antisense oligodeoxynucleotide against HST-1/FGF-4 suppresses tumorigenicity of a human germ cell tumor.

METHODS AND RESULTS

To test whether HST-1/FGF-4 could be the target of gene therapy for testicular carcinoma, 20-mer phosphorothioate oligodeoxynucleotides (ODNs) directed against human HST-1/FGF-4 were analyzed for their antitumor activity. The antisense HST-1/FGF-4 ODNs suppressed HST-1/FGF-4 production by NEC8 human nonseminomatous germ cells and inhibited their cell growth in vitro. Furthermore, after orthotopic implantation of NEC8 cells, combined treatment with antisense HST-1/FGF-4 ODNs and Atelocollagen significantly inhibited the growth of testicular tumors as well as the incidence of lymph node metastasis. In contrast, administration of antisense ODNs alone was less effective.

CONCLUSIONS

Collectively, these results indicate that the antisense method against HST-1/FGF-4 gene expression will be a novel therapeutic approach for male germ cell tumors. The use of Atelocollagen-mediated administration of the antisense HST-1/FGF-4 ODNs may be useful in enhancing the effects of antisense therapy.

HST-1/FGF-4 protects male germ cells from apoptosis under heat-stress condition

Apoptosis plays an important role in controlling the number of male germ cells and eliminating defective germ cells during testicular development and spermatogenesis. We show here that fibroblast growth factor-4 (HST-1/FGF-4) may play a critical role as a survival factor for germ cells, protecting them from apoptosis. Testes of adult male mice that received an adenovirus carrying human HST-1/FGF-4 (AxHST-1) or a control adenovirus (AxCAwt) were exposed to mild hyperthermia, which causes germ cell apoptosis. An in situ terminal-deoxynucleotidyl transferase-mediated deoxy-UTP nick end-labeling (TUNEL) assay characterized germ cell apoptosis. The results indicated that HST-1/FGF-4 significantly reduced the apoptotic death of germ cells and prevented testicular weight loss and sperm count reduction. We also found that Hst-1/Fgf-4 present in testes is up-regulated in vivo when the testes are exposed to mild hyperthermia, and that endogenous Hst-1/Fgf-4 mRNA expression in Sertoli cells are also induced when the cells are exposed to mild hyperthermia in vitro. In addition, the MAPK cascade, which could increase an FGF-dependent survival signal, is activated by HST-1/FGF-4 stimuli in germ cells. On the other hand, upon HST-1/FGF-4 stimulation, lactate production from Sertoli cells were induced, which is indispensable nutrient for germ cell survival. These results suggest that HST-1/FGF-4 can act as an important physiological anti-apoptotic factor for male germ cells in stimulating lactate production of Sertoli cells upon heat stress, thereby promoting germ cell survival.

Oct-3/4 is a dose-dependent oncogenic fate determinant

The Oct-3/4 transcription factor sustains embryonic stem (ES) cell self-renewal and is a dose-dependent cell fate determinant. In the adult male, its expression is restricted to type A spermatogonia. We show that Oct-3/4 is expressed in all human testicular germ cell tumors (GCTs) tested, even in the early premalignant component. We demonstrate that Oct-3/4 dictates ES cells' oncogenic potential in a dose-dependent manner; high levels increase the malignant potential of ES cell-derived tumors while Oct-3/4 inactivation induces regression of the malignant component. Oct-3/4 expression in a heterologous cell system transforms nontumorigenic cells and endows tumorigenicity in nude mice. Our findings suggest that Oct-3/4 is not only a distinctive immunohistochemical marker for GCTs, but also plays a critical role in the genesis of these tumors.

2,5-hexanedione-induced testicular injury

Now in its third decade of mechanistic investigation, testicular injury caused by 2,5-hexanedione (2,5-HD) exposure is a well-studied model with a rich database. The development of this model reflects the larger changes that have moved biology from a branch of chemistry into the molecular age. Critically examined in this review is the proposed mechanism for 2,5-HD-induced testicular injury in which germ cell maturation is disrupted owing to alterations in Sertoli cell microtubule-mediated functions. The goal is to evaluate the technical and conceptual approaches used to assess 2,5-HD-induced testicular injury, to highlight unanswered questions, and to identify fruitful avenues of future research.