Direct Reprogramming of Mouse Fibroblasts toward Leydig-like Cells by Defined Factors. Stem Cell Reports. 2017;8:39-53. [PMID: 28017657 PMCID: PMC5233410 DOI: 10.1016/j.stemcr.2016.11.010]

High resolution tissue and cell type identification via single cell transcriptomic profiling

Tissue identification can be instrumental in reconstructing a crime scene but remains a challenging task in forensic investigations. Conventionally, identifying the presence of certain tissue from tissue mixture by predefined cell type markers in bulk fashion is challenging due to limitations in sensitivity and accuracy. In contrast, single-cell RNA sequencing (scRNA-Seq) is a promising technology that has the potential to enhance or even revolutionize tissue and cell type identification. In this study, we developed a high sensitive general purpose single cell annotation pipeline, scTissueID, to accurately evaluate the single cell profile quality and precisely determine the cell and tissue types based on scRNA profiles. By incorporating a crucial and unique reference cell quality differentiation phase of targeting only high confident cells as reference, scTissueID achieved better and consistent performance in determining cell and tissue types compared to 8 state-of-art single cell annotation pipelines and 6 widely adopted machine learning algorithms, as demonstrated through a large-scale and comprehensive comparison study using both forensic-relevant and Human Cell Atlas (HCA) data. We highlighted the significance of cell quality differentiation, a previously undervalued factor. Thus, this study offers a tool capable of accurately and efficiently identifying cell and tissue types, with broad applicability to forensic investigations and other biomedical research endeavors.

Generation of glucocorticoid-producing cells derived from human pluripotent stem cells

Adrenal insufficiency is a life-threatening condition resulting from the inability to produce adrenal hormones in a dose- and time-dependent manner. Establishing a cell-based therapy would provide a physiologically responsive approach for the treatment of this condition. We report the generation of large numbers of human-induced steroidogenic cells (hiSCs) from human pluripotent stem cells (hPSCs). Directed differentiation of hPSCs into hiSCs recapitulates the initial stages of human adrenal development. Following expression of steroidogenic factor 1, activation of protein kinase A signaling drives a steroidogenic gene expression profile most comparable to human fetal adrenal cells, and leads to dynamic secretion of steroid hormones, in vitro. Moreover, expression of the adrenocorticotrophic hormone (ACTH) receptor/co-receptor (MC2R/MRAP) results in dose-dependent ACTH responsiveness. This protocol recapitulates adrenal insufficiency resulting from loss-of-function mutations in AAAS, which cause the enigmatic triple A syndrome. Our differentiation protocol generates sufficient numbers of hiSCs for cell-based therapy and offers a platform to study disorders causing adrenal insufficiency.

Small Molecule Cocktails Promote Fibroblast-to-Leydig-like Cell Conversion for Hypogonadism Therapy

Male hypogonadism arises from the inadequate production of testosterone (T) by the testes, primarily due to Leydig cell (LC) dysfunction. Small molecules possess several advantages, including high cell permeability, ease of synthesis, standardization, and low effective concentration. Recent investigations have illuminated the potential of small molecule combinations to facilitate direct lineage reprogramming, removing the need for transgenes by modulating cellular signaling pathways and epigenetic modifications. In this study, we have identified a specific cocktail of small molecules, comprising forskolin, DAPT, purmorphamine, 8-Br-cAMP, 20α-hydroxycholesterol, and SAG, capable of promoting the conversion of fibroblasts into Leydig-like cells (LLCs). These LLCs expressed key genes involved in testosterone synthesis, such as Star, Cyp11a1, and Hsd3b1, and exhibited the ability to secrete testosterone in vitro. Furthermore, they successfully restored serum testosterone levels in testosterone-castrated mice in vivo. The small molecule cocktails also induced alterations in the epigenetic marks, specifically H3K4me3, and enhanced chromosomal accessibility on core steroidogenesis genes. This study presents a reliable methodology for generating Leydig-like seed cells that holds promise as a novel therapeutic approach for hypogonadism.

Epigenome editing based on CRISPR/dCas9p300 facilitates transdifferentiation of human fibroblasts into Leydig-like cells

Recently, Leydig cell (LCs) transplantation has a promising potential to treat male hypogonadism. However, the scarcity of seed cells is the actual barrier impeding the application of LCs transplantation. Utilizing the cutting-edge CRISPR/dCas9^VP64 technology, human foreskin fibroblasts (HFFs) were transdifferentiated into Leydig-like cells（iLCs） in previous study, but the efficiency of transdifferentiation is not very satisfactory. Therefore, this study was conducted to further optimize the CRISPR/dCas9 system for obtaining sufficient iLCs. First, the stable CYP11A1-Promoter-GFP-HFFs cell line was established by infecting HFFs with CYP11A1-Promoter-GFP lentiviral vectors, and then co-infected with dCas9^p300 and the combination of sgRNAs targeted to NR5A1, GATA4 and DMRT1. Next, this study adopted quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blot, and immunofluorescence to determine the efficiency of transdifferentiation, the generation of testosterone, the expression levels of steroidogenic biomarkers. Moreover, we utilized chromatin immuno-precipitation (ChIP) followed by quantitative polymerase chain reaction (ChIP-qPCR) to measure the levels of acetylation of targeted H3K27. The results revealed that advanced dCas9^p300 facilitated generation of iLCs. Moreover, the dCas9^p300-mediated iLCs significantly expressed the steroidogenic biomarkers and produced more testosterone with or without LH treatment than the dCas9^VP64-mediated. Additionally, preferred enrichment in H3K27ac at the promoters was detected only with dCas9^p300 treatment. The data provided here imply that the improved version of dCas9 can aid in the harvesting of iLCs, and will provide sufficient seed cells for cell transplantation treatment of androgen deficiency in the future.

Emerging concepts on Leydig cell development in fetal and adult testis

Leydig cells (Lc) reside in the interstitial compartment of the testis and are the target of Luteinising hormone (LH) for Testosterone (T) production, thus critically regulates male fertility. Classical histological studies have identified two morphologically different populations of Lc during testicular development [fetal (FLc) and adult (ALc)]. Recent progress in ex vivo cell/organ culture, genome-wide analysis, genetically manipulated mouse models, lineage tracing, and single-cell RNA-seq experiments have revealed the diverse cellular origins with differential transcriptomic and distinct steroidogenic outputs of these populations. FLc originates from both coelomic epithelium and notch-active Nestin-positive perivascular cells located at the gonad-mesonephros borders, and get specified as Nr5a1 (previously known as Ad4BP/SF-1) expressing cells by embryonic age (E) 12.5 days in fetal mouse testes. These cells produce androstenedione (precursor of T, due to lack of HSD17β3 enzyme) and play critical a role in initial virilization and patterning of the male external genitalia. However, in neonatal testis, FLc undergoes massive regression/dedifferentiation and gradually gets replaced by T-producing ALc. Very recent studies suggest a small fraction (5-20%) of FLc still persists in adult testis. Both Nestin-positive perivascular cells and FLc are considered to be the progenitor populations for ALc. This minireview article summarizes the current understanding of Lc development in fetal and adult testes highlighting their common or diverse cellular (progenitor/stem) origins with respective functional significance in both rodents and primates. (227 words).

High-fidelity reprogramming into Leydig-like cells by CRISPR activation and paracrine factors

Androgen deficiency is a common medical conditions that affects males of all ages. Transplantation of testosterone-producing cells is a promising treatment for male hypogonadism. However, getting a cell source with the characteristics of Leydig cells (LCs) is still a challenge. Here, a high-efficiency reprogramming of skin-derived fibroblasts into functional Leydig-like cells (LLCs) based on epigenetic mechanism was described. By performing an integrated analysis of genome-wide DNA methylation and transcriptome profiling in LCs and fibroblasts, the potentially epigenetic-regulating steroidogenic genes and signaling pathways were identified. Then by using CRISPR/dCas9 activation system and signaling pathway regulators, the male- or female-derived fibroblasts were reprogrammed into LLCs with main LC-specific traits. Transcriptomic analysis further indicated that the correlation coefficients of global genes and transcription factors between LLCs and LCs were higher than 0.81 and 0.96, respectively. After transplantation in the testes of hypogonadal rodent models, LLCs increased serum testosterone concentration significantly. In type 2 diabetic rats model, LLCs which were transplanted in armpit, have the capability to restore the serum testosterone level and improve the hyperglycemia status. In conclusion, our approach enables skin-derived fibroblasts reprogramming into LLCs with high fidelity, providing a potential cell source for the therapeutics of male hypogonadism and metabolic-related comorbidities.

COUP-TFII interacts and functionally cooperates with GATA4 to regulate Amhr2 transcription in mouse MA-10 Leydig cells

BACKGROUND

Leydig cells produce testosterone and insulin-like 3, two hormones essential for male sex differentiation and reproductive function. The orphan nuclear receptor COUP-TFII and the zinc finger factor GATA4 are two transcription factors involved in Leydig cell differentiation, gene expression and function.

OBJECTIVES

Several Leydig cell gene promoters contain binding motifs for both GATA factors and nuclear receptors. The goal of present study is to determine whether GATA4 and COUP-TFII cooperate to regulate gene expression in Leydig cells.

MATERIALS AND METHODS

The transcriptomes from GATA4- and COUP-TFII-depleted MA-10 Leydig cells were analyzed using bioinformatic tools. Functional cooperation between GATA4 and COUP-TFII, and other related family members, was assessed by transient transfections in Leydig (MA-10 and MLTC-1) and fibroblast (CV-1) cell lines on several gene promoters. Recruitment of GATA4 and COUP-TFII to gene promoters was investigated by chromatin immunoprecipitation. Co-immunoprecipitation was used to determine whether GATA4 and COUP-TFII interact in MA-10 Leydig cells.

RESULTS

Transcriptomic analyses of GATA4- and COUP-TFII-depleted MA-10 Leydig cells revealed 44 commonly regulated genes including the anti-Müllerian hormone receptor (Amhr2) gene. GATA4 and COUP-TFII independently activated the Amhr2 promoter, and their combination led to a stronger activation. A GC-rich element, located in the proximal Amhr2 promoter was found to be essential for GATA4- and COUP-TFII-dependent activation as well as for the COUP-TFII/GATA4 cooperation. COUP-TFII and GATA4 directly interacted in MA-10 Leydig cell extracts. Chromatin immunoprecipitation revealed that GATA4 and COUP-TFII are recruited to the proximal Amhr2 promoter, which contains binding sites for both factors in addition to the GC-rich element. Cooperation between COUP-TFII and GATA6, but not GATA1 and GATA3, was also observed.

DISCUSSION AND CONCLUSION

Our results establish the importance of a physical and functional cooperation between COUP-TFII/GATA4 in the regulation of gene expression in MA-10 Leydig cells, and more specifically the Amhr2 gene. This article is protected by copyright. All rights reserved.

Transcription Factors in the Regulation of Leydig Cell Gene Expression and Function

Cell differentiation and acquisition of specialized functions are inherent steps in events that lead to normal tissue development and function. These processes require accurate temporal, tissue, and cell-specific activation or repression of gene transcription. This is achieved by complex interactions between transcription factors that form a unique combinatorial code in each specialized cell type and in response to different physiological signals. Transcription factors typically act by binding to short, nucleotide-specific DNA sequences located in the promoter region of target genes. In males, Leydig cells play a crucial role in sex differentiation, health, and reproductive function from embryonic life to adulthood. To better understand the molecular mechanisms regulating Leydig cell differentiation and function, several transcription factors important to Leydig cells have been identified, including some previously unknown to this specialized cell type. This mini review summarizes the current knowledge on transcription factors in fetal and adult Leydig cells, describing their roles and mechanisms of action.

Differentiation of Human Induced Pluripotent Stem Cells Into Testosterone-Producing Leydig-like Cells

Late-onset hypogonadism (LOH) syndrome, due to a partial lack of testosterone, decreases the quality of life of older men. Testosterone is mainly secreted by Leydig cells in the testes. Leydig cell transplantation is expected to be a promising alternative to conventional testosterone replacement therapy for LOH syndrome. We herein report a simple and robust protocol for directed differentiation of human induced pluripotent stem cells (hiPSCs) into Leydig-like cells by doxycycline-inducible overexpression of NR5A1 and treatment with a combination of 8-bromoadenosine-3',5'-cyclic monophosphate (8-Br-cAMP) and forskolin. The differentiated cells expressed the steroidogenic enzyme genes STAR, CYP11A1, CYP17A1, and HSD3B2 and the specific markers of adult Leydig cells HSD17B3, INSL3, and LHCGR. Furthermore, we confirmed the secretion of functional testosterone from the cells into the culture supernatant by a testosterone-sensitive cell proliferation assay. These findings showed that the hiPSCs were able to be differentiated into Leydig-like cells, supporting the expectation that hiPSC-derived Leydig-like cells can be novel tools for treating LOH syndrome.

An autofluorescence-based isolation of Leydig cells for testosterone deficiency treatment

Effective procedures for the purification of Leydig cells (LCs) can facilitate functional studies and transplantation therapies. However, current methods to purify LCs from testes are still far from satisfactory. Here, we found that testicular autofluorescence existed in the interstitium along with the gradual maturation of LCs from birth to adulthood. These autofluorescent cells were further isolated by fluorescence-activated cell sorting (FACS) and determined to be composed of LCs and macrophages. To further purify LCs, we combined two fluorescence channels of FACS and successfully separated LCs and macrophages. Of note, we confirmed that the obtained LCs not only possessed high purity, viability and quantity but also had intact steroidogenic activity and excellent responsiveness to luteinizing hormone. Moreover, subcutaneous transplantation of isolated LCs could alleviate the symptoms of testosterone deficiency in castrated mice. In summary, we established an effective autofluorescence-based method for isolating LCs. This method will aid in the future success of using LCs for basic and translational applications.

The Desert Hedgehog Signalling Pathway in Human Gonadal Development and Differences of Sex Development

While the Hedgehog signalling pathway is implicated in numerous developmental processes and maladies, variants in the Desert Hedgehog (DHH) ligand underlie a condition characterised by 46,XY gonadal dysgenesis with or without peripheral neuropathy. We discuss here the role and regulation of DHH and its signalling pathway in the developing gonads and examine the current understanding of how disruption to this pathway causes this difference of sex development (DSD) in humans.

Advances in stem cell research for the treatment of primary hypogonadism

In Leydig cell dysfunction, cells respond weakly to stimulation by pituitary luteinizing hormone, and, therefore, produce less testosterone, leading to primary hypogonadism. The most widely used treatment for primary hypogonadism is testosterone replacement therapy (TRT). However, TRT causes infertility and has been associated with other adverse effects, such as causing erythrocytosis and gynaecomastia, worsening obstructive sleep apnoea and increasing cardiovascular morbidity and mortality risks. Stem-cell-based therapy that re-establishes testosterone-producing cell lineages in the body has, therefore, become a promising prospect for treating primary hypogonadism. Over the past two decades, substantial advances have been made in the identification of Leydig cell sources for use in transplantation surgery, including the artificial induction of Leydig-like cells from different types of stem cells, for example, stem Leydig cells, mesenchymal stem cells, and pluripotent stem cells (PSCs). PSC-derived Leydig-like cells have already provided a powerful in vitro model to study the molecular mechanisms underlying Leydig cell differentiation and could be used to treat men with primary hypogonadism in a more specific and personalized approach.

Perfluorotridecanoic acid inhibits fetal Leydig cell differentiation after in utero exposure in rats via increasing oxidative stress and autophagy

Perfluorotridecanoic acid (PFTrDA) is a long-chain perfluoroalkyl substance, and its effect on the differentiation of fetal Leydig cells remains unclear. The objective of this study is to explore the effect of in utero PFTrDA exposure on the differentiation of fetal Leydig cells and investigate its underlying mechanisms. Pregnant Sprague-Dawley female rats were daily administered by gavage of PFTrDA at doses of 0, 1, 5, and 10 mg/kg from gestational day 14 to 21. PFTrDA had no effect on the body weight of dams, but significantly reduced the body weight and anogenital distance of male pups at birth at a dose of 10 mg/kg. PFTrDA significantly decreased serum testosterone levels as low as 1 mg/kg. PFTrDA did not affect fetal Leydig cell number, but promoted abnormal aggregation of fetal Leydig cells at doses of 5 and 10 mg/kg. PFTrDA down-regulated the expression of Insl3, Lhcgr, Scarb1, Star, Hsd3b1, Cyp17a1, Nr5a1, and Dhh as well as their proteins. PFTrDA lowered the levels of antioxidants (SOD1, CAT, and GPX1), induced autophagy as shown by increased levels of LC3II and beclin1, and reduced the phosphorylation of mTOR. In conclusion, PFTrDA inhibits the differentiation of fetal Leydig cells in male pups after in utero exposure mainly through increasing oxidative stress and inducing autophagy.

Bisphenol B stimulates Leydig cell proliferation but inhibits maturation in late pubertal rats

Bisphenol B (BPB) has been used as a substitute for bisphenol A (BPA) in plastic materials. Whether BPB disrupts the male reproductive system remains unknown. Here, we report the effect of BPB on Leydig cell maturation in late puberty. Male Sprague-Dawley (35 days old) rats were gavaged with BPB at 0, 10, 100, and 200 mg/kg/day for 21 days. BPB significantly reduced body and epididymis weight at 200 mg/kg. BPB markedly decreased serum testosterone levels at 100 and 200 mg/kg and serum luteinizing hormone and follicle-stimulating hormone levels at 200 mg/kg. BPB significantly increased Leydig cell number at 100 and 200 mg/kg, while down-regulating the expression of Leydig cell genes (Cyp11a1 and Hsd3b1) at ≥100 mg/kg and up-regulating the expression of Sertoli cell genes (Pdgfra, Fshr, Sox9) and cell cycle regulators (Pcna, Ccnb1, Cdk2, and Cdk4) at 10-200 mg/kg. BPB markedly increased the phosphorylation of AKT1, AKT2, and ERK1/2 at 200 mg/kg. BPB increased the proliferation of rat immature Leydig cells via promoting the S/M2 phase shift at 100 and 1000 nM after 24-h culture in vitro. In conclusion, BPB disrupts Leydig cell maturation in late puberty by increasing Leydig cell number while inhibiting its maturation.

Coordination of Multiple Cellular Processes by NR5A1/Nr5a1

The agenesis of the gonads and adrenal gland in revealed by knockout mouse studies strongly suggested a crucial role for Nr5a1 (SF-1 or Ad4BP) in organ development. In relation to these striking phenotypes, NR5A1/Nr5a1 has the potential to reprogram cells to steroidogenic cells, endow pluripotency, and regulate cell proliferation. However, due to limited knowledge regarding NR5A1 target genes, the mechanism by which NR5A1/Nr5a1 regulates these fundamental processes has remained unknown. Recently, newlyestablished technologies have enabled the identification of NR5A1 target genes related to multiple metabolic processes, as well as the aforementioned biological processes. Considering that active cellular processes are expected to be accompanied by active metabolism, NR5A1 may act as a key factor for processes such as cell differentiation, proliferation, and survival by coordinating these processes with cellular metabolism. A complete and definite picture of the cellular processes coordinated by NR5A1/Nr5a1 could be depicted by accumulating evidence of the potential target genes through whole genome studies.

An In Vitro Differentiation Protocol for Human Embryonic Bipotential Gonad and Testis Cell Development

Currently an in vitro model that fully recapitulates the human embryonic gonad is lacking. Here we describe a fully defined feeder-free protocol to generate early testis-like cells with the ability to be cultured as an organoid, from human induced pluripotent stem cells. This stepwise approach uses small molecules to mimic embryonic development, with upregulation of bipotential gonad markers (LHX9, EMX2, GATA4, and WT1) at day 10 of culture, followed by induction of testis Sertoli cell markers (SOX9, WT1, and AMH) by day 15. Aggregation into 3D structures and extended culture on Transwell filters yielded organoids with defined tissue structures and distinct Sertoli cell marker expression. These studies provide insight into human gonadal development, suggesting that a population of precursor cells may originate from a more lateral region of the mesoderm. Our protocol represents a significant advance toward generating a much-needed human gonad organoid for studying disorders/differences of sex development.

Stem cell-based therapies for fertility preservation in males: Current status and future prospects

With the decline in male fertility in recent years, strategies for male fertility preservation have received increasing attention. In this study, by reviewing current treatments and recent publications, we describe research progress in and the future directions of stem cell-based therapies for male fertility preservation, focusing on the use of spermatogonial stem cells (SSCs), SSC niches, SSC-based testicular organoids, other stem cell types such as mesenchymal stem cells, and stem cell-derived extracellular vesicles. In conclusion, a more comprehensive understanding of the germ cell microenvironment, stem cell-derived extracellular vesicles, and testicular organoids will play an important role in achieving male fertility preservation.

Conversion of Fibroblast into Functional Leydig-like Cell Using Defined Small Molecules

Recent studies have demonstrated that fibroblasts can be directly converted into functional Leydig cells by transcription factors. However, the transgenic approach used in these studies raises safety concerns for its future application. Here, we report that fibroblasts can be directly reprogrammed into Leydig-like cells by exposure to a combination of forskolin, 20α-hydroxycholesterol, luteinizing hormone, and SB431542. These chemical compound-induced Leydig-like cells (CiLCs) express steroidogenic genes and have a global gene expression profile similar to that of progenitor Leydig cells, although not identical. In addition, these cells can survive in testis and produce testosterone in a circadian rhythm. This induction strategy is applicable to reprogramming human periodontal ligament fibroblasts toward Leydig-like cells. These findings demonstrated fibroblasts can be directly converted into Leydig-like cells by pure chemical compounds. This strategy overcomes the limitations of conventional transgenic-based reprogramming and provides a simple, effective approach for Leydig cell-based therapy while simultaneously preserving the hypothalamic-pituitary-gonadal axis.

•

Direct induction of fibroblasts into Leydig-like cells (CiLCs) by chemicals

•

CiLCs were modulated by HPG axis and produced testosterone in a diurnal rhythm

•

Conversion process toward CiLCs did not pass through an intermediate state

Characterization of rodent Sertoli cell primary cultures

Sertoli cells play a vital role in spermatogenesis by offering physical and nutritional support to the differentiating male germ cells. They form the blood-testis barrier and secrete growth factors essential for germ cell differentiation. Sertoli cell primary cultures are critical for understanding the regulation of spermatogenesis; however, obtaining pure cultures has been a challenge. Rodent Sertoli cell isolation protocols do not rule out contamination by the interstitial or connective tissue cells. Sertoli cell-specific markers could be helpful, but there is no consensus. Vimentin, the most commonly used marker, is not specific for Sertoli cells since its expression has been reported in peritubular myoid cells, mesenchymal stem cells, fibroblasts, macrophages, and endothelial cells, which contaminate Sertoli cell preparations. Markers based on transcription and growth factors also have limitations. Thus, the impediment to obtaining pure Sertoli cell cultures pertains to both the method of isolation and marker usage. The aim of this review is to discuss improvements to current methods of rodent Sertoli cell primary cultures, assess the properties of prepubertal versus mature Sertoli cell cultures, and propose steps to improve cellular characterization. Potential benefits of using contemporary approaches, including lineage tracing, specific cell ablation, and RNA-seq for obtaining Sertoli-specific transcript markers are discussed. Evaluating the specificity and applicability of these markers at the protein level to characterize Sertoli cells in culture would be critical. This review is expected to positively impact future work using primary cultures of rodent Sertoli cells.

Leydig-like cells derived from reprogrammed human foreskin fibroblasts by CRISPR/dCas9 increase the level of serum testosterone in castrated male rats

In the past few years, Leydig cell (LC) transplantation has been regarded as an effective strategy for providing physiological patterns of testosterone in vivo. Recently, we have successfully converted human foreskin fibroblasts (HFFs) into functional Leydig‐like cells (iLCs) in vitro by using the CRISPR/dCas9 system, which shows promising potential for seed cells. However, it is not known whether the reprogrammed iLCs can survive or restore serum testosterone levels in vivo. Therefore, in this study, we evaluate whether reprogrammed iLCs can restore the serum testosterone levels of castrated rats when they are transplanted into the fibrous capsule. We first developed the castrated Sprague Dawley rat model through bilateral orchiectomy and subsequently injected extracellular matrix gel containing transplanted cells into the fibrous capsule of castrated rats. Finally, we evaluated dynamic serum levels of testosterone and luteinizing hormone (LH) in castrated rats, the survival of implanted iLCs, and the expression levels of Leydig steroidogenic enzymes by immunofluorescence staining and Western blotting. Our results demonstrated that implanted iLCs could partially restore the serum testosterone level of castrated rats, weakly mimic the role of adult Leydig cells in the hypothalamic‐pituitary‐gonadal axis for a short period, and survive and secrete testosterone, through 6 weeks after transplantation. Therefore, this study may be valuable for treating male hypogonadism in the future.

Reprogramming of human fibroblasts into osteoblasts by insulin-like growth factor-binding protein 7

The induced pluripotent stem cell (iPSC) is a promising cell source for tissue regeneration. However, the therapeutic value of iPSC technology is limited due to the complexity of induction protocols and potential risks of teratoma formation. A trans-differentiation approach employing natural factors may allow better control over reprogramming and improved safety. We report here a novel approach to drive trans-differentiation of human fibroblasts into functional osteoblasts using insulin-like growth factor binding protein 7 (IGFBP7). We initially determined that media conditioned by human osteoblasts can induce reprogramming of human fibroblasts to functional osteoblasts. Proteomic analysis identified IGFBP7 as being significantly elevated in media conditioned with osteoblasts compared with those with fibroblasts. Recombinant IGFBP7 induced a phenotypic switch from fibroblasts to osteoblasts. The switch was associated with senescence and dependent on autocrine IL-6 signaling. Our study supports a novel strategy for regenerating bone by using IGFBP7 to trans-differentiate fibroblasts to osteoblasts.

Stem Leydig Cells in the Adult Testis: Characterization, Regulation and Potential Applications

Androgen deficiency (hypogonadism) affects males of all ages. Testosterone replacement therapy (TRT) is effective in restoring serum testosterone and relieving symptoms. TRT, however, is reported to have possible adverse effects in part because administered testosterone is not produced in response to the hypothalamic-pituitary-gonadal (HPG) axis. Progress in stem cell biology offers potential alternatives for treating hypogonadism. Adult Leydig cells (ALCs) are generated by stem Leydig cells (SLCs) during puberty. SLCs persist in the adult testis. Considerable progress has been made in the identification, isolation, expansion and differentiation of SLCs in vitro. In addition to forming ALCs, SLCs are multipotent, with the ability to give rise to all 3 major cell lineages of typical mesenchymal stem cells, including osteoblasts, adipocytes, and chondrocytes. Several regulatory factors, including Desert hedgehog and platelet-derived growth factor, have been reported to play key roles in the proliferation and differentiation of SLCs into the Leydig lineage. In addition, stem cells from several nonsteroidogenic sources, including embryonic stem cells, induced pluripotent stem cells, mature fibroblasts, and mesenchymal stem cells from bone marrow, adipose tissue, and umbilical cord have been transdifferentiated into Leydig-like cells under a variety of induction protocols. ALCs generated from SLCs in vitro, as well as Leydig-like cells, have been successfully transplanted into ALC-depleted animals, restoring serum testosterone levels under HPG control. However, important questions remain, including: How long will the transplanted cells continue to function? Which induction protocol is safest and most effective? For translational purposes, more work is needed with primate cells, especially human.

Sulfonated chitosan oligosaccharide alleviates the inhibitory effect of basic fibroblast growth factor on osteogenic differentiation of human periodontal ligament stem cells

BACKGROUND

Periodontal ligament stem cells (PDLSCs) play an essential role in periodontal tissue repair. Basic fibroblast growth factor (bFGF) has been used in the clinical treatment of periodontal disease. However, studies have shown that bFGF inhibits the osteogenic differentiation of PDLSCs, which is not conducive to alveolar bone repair. Sulfonated chitosan oligosaccharide (SCOS), a heparan-like compound, can maintain the conformation of bFGF and promote its proliferation activity. This study investigated the effects of bFGF in combination with SCOS on the osteogenic differentiation of hPDLSCs.

METHODS

hPDLSCs were isolated from healthy human periodontal ligament and identified by flow cytometry and immunofluorescence. The affinity between SCOS and bFGF was analyzed by surface plasmon resonance. Changes in osteogenic differentiation by combination of bFGF with SCOS were analyzed by alkaline phosphatase activity assay, Sirius Red staining, and Alizarin Red staining. Expression of genes and proteins was investigated by western blotting and reverse transcription-quantitative PCR.

RESULTS

Extracted hPDLSCs were mesenchymal stem cells with pluripotent differentiation potential. SCOS exhibited an affinity for bFGF. bFGF (20 ng/mL) promoted the proliferation of hPDLSCs, but inhibited their osteogenic differentiation. SCOS alleviated the inhibitory effect of bFGF on the osteogenic differentiation of hPDLSCs.

CONCLUSIONS

SCOS can reduce the inhibitory effect of bFGF on the osteogenic differentiation of hPDLSCs. This study provides evidence for the clinical use of bFGF to repair periodontal tissue.

Direct cell-fate conversion of somatic cells: Toward regenerative medicine and industries

Cells of multicellular organisms have diverse characteristics despite having the same genetic identity. The distinctive phenotype of each cell is determined by molecular mechanisms such as epigenetic changes that occur throughout the lifetime of an individual. Recently, technologies that enable modification of the fate of somatic cells have been developed, and the number of studies using these technologies has increased drastically in the last decade. Various cell types, including neuronal cells, cardiomyocytes, and hepatocytes, have been generated using these technologies. Although most direct reprogramming methods employ forced transduction of a defined sets of transcription factors to reprogram cells in a manner similar to induced pluripotent cell technology, many other strategies, such as methods utilizing chemical compounds and microRNAs to change the fate of somatic cells, have also been developed. In this review, we summarize transcription factor-based reprogramming and various other reprogramming methods. Additionally, we describe the various industrial applications of direct reprogramming technologies.

Potential use of stem cells for fertility preservation

BACKGROUND

Infertility and gonadal dysfunction can result from gonadotoxic therapies, environmental exposures, aging, or genetic conditions. In men, non-obstructive azoospermia (NOA) results from defects in the spermatogenic process that can be attributed to spermatogonial stem cells (SSC) or their niche, or both. While assisted reproductive technologies and sperm banking can enable fertility preservation (FP) in men of reproductive age who are at risk for infertility, FP for pre-pubertal patients remains experimental. Therapeutic options for NOA are limited. The rapid advance of stem cell research and of gene editing technologies could enable new FP options for these patients. Induced pluripotent stem cells (iPSC), SSC, and testicular niche cells, as well as mesenchymal stromal cells (aka medicinal signaling cells, MSCs), have been investigated for their potential use in male FP strategies.

OBJECTIVE

Here, we review the benefits and challenges for three types of stem cell-based approaches under investigation for male FP, focusing on the role that promising sources of MSC derived from human umbilical cord, specifically human umbilical cord perivascular cells (HUCPVC), could fulfill. These approaches are as follows: 1. isolation and ex vivo expansion of autologous SSC for in vivo transplantation or in vitro spermatogenesis; 2. in vitro differentiation toward germ cell and testicular somatic cell lineages using autologous SSC, or stem cells such iPSC or MSC; and 3. protection or regeneration of the spermatogenic niche after gonadotoxic insults in vivo.

CONCLUSION

Our studies suggest that HUCPVC are promising sources of cells that could be utilized in multiple aspects of male FP strategies.

CRISPR/dCas9-mediated activation of multiple endogenous target genes directly converts human foreskin fibroblasts into Leydig-like cells

Recently, Leydig cell (LC) transplantation has been revealed as a promising strategy for treating male hypogonadism; however, the key problem restricting the application of LC transplantation is a severe lack of seed cells. It seems that targeted activation of endogenous genes may provide a potential alternative. Therefore, the aim of this study was to determine whether targeted activation of Nr5a1, Gata4 and Dmrt1 (NGD) via the CRISPR/dCas9 synergistic activation mediator system could convert human foreskin fibroblasts (HFFs) into functional Leydig-like cells. We first constructed the stable Hsd3b-dCas9-MPH-HFF cell line using the Hsd3b-EGFP, dCas9-VP64 and MS2-P65-HSF1 lentiviral vectors and then infected it with single guide RNAs. Next, we evaluated the reprogrammed cells for their reprogramming efficiency, testosterone production characteristics and expression levels of Leydig steroidogenic markers by quantitative real-time polymerase chain reaction or Western blotting. Our results showed that the reprogramming efficiency was close to 10% and that the reprogrammed Leydig-like cells secreted testosterone rapidly and, more importantly, responded effectively to stimulation with human chorionic gonadotropin and expressed Leydig steroidogenic markers. Our findings demonstrate that simultaneous targeted activation of the endogenous NGD genes directly reprograms HFFs into functional Leydig-like cells, providing an innovative technology that may have promising potential for the treatment of male androgen deficiency diseases.

Fibroblast growth factor homologous factor 1 stimulates Leydig cell regeneration from stem cells in male rats

Fibroblast growth factor homologous factor 1 (FHF1) is an intracellular protein that does not bind to cell surface fibroblast growth factor receptor. Here, we report that FHF1 is abundantly present in Leydig cells with up‐regulation during its development. Adult male Sprague Dawley rats were intraperitoneally injected with 75 mg/kg ethane dimethane sulphonate (EDS) to ablate Leydig cells to initiate their regeneration. Then, rats daily received intratesticular injection of FHF1 (0, 10 and 100 ng/testis) from post‐EDS day 14 for 14 days. FHF1 increased serum testosterone levels without affecting the levels of luteinizing hormone and follicle‐stimulating hormone. FHF1 increased the cell number staining with HSD11B1, a biomarker for Leydig cells at the advanced stage, without affecting the cell number staining with CYP11A1, a biomarker for all Leydig cells. FHF1 did not affect PCNA‐labelling index in Leydig cells. FHF1 increased Leydig cell mRNA (Lhcgr, Scarb1, Star, Cyp11a1, Hsd3b1, Cyp17a1, Hsd17b3, Insl3, Nr5a1 and Hsd11b1) and their protein levels in vivo. FHF1 increased preadipocyte biomarker Dlk1 mRNA level and decreased fully differentiated adipocyte biomarker (Fabp4 and Lpl) mRNA and their protein levels. In conclusion, FHF1 promotes Leydig cell regeneration from stem cells while inhibiting the differentiation of preadipocyte/stem cells into adipocytes in EDS‐treated testis.

Conversion of human fibroblasts into functional Leydig-like cells by small molecules and a single factor

Reprogramming fibroblasts into Leydig cells (LCs) offers a promising source for cell-based therapy for male hypogonadism. Recently, it has been achieved by forced expression of multiple transcription factors (TFs). However, for ultimate safe and convenient application, small molecules would be a revolutionary and desirable method to reduce or eliminate the genetic manipulations. Here, we report a defined small-molecule cocktail that enables the highly efficient conversion of human fibroblasts into functional LCs with only one transcription factor. These induced cells resembled human LCs with respect to morphology, marker gene expression and secretary function of testosterone. This study lays a foundation for future pharmacological reprogramming and provides a unique venue for investigating mechanisms underlying reprogramming.

Dexamethasone suppresses the differentiation of stem Leydig cells in rats in vitro

BACKGROUND

It is an established fact that excess of glucocorticoids could cause the harmful effects, such as suppression on the male reproduction. Although glucocorticoids pharmacologically inhibit the Leydig cell function, their roles in Leydig cell development are unclear. Therefore, the present study was designed to investigate effects of synthetic glucocorticoid dexamethasone (DEX) on rat stem Leydig cell proliferation and differentiation.

METHODS

Male Sprague-Dawley rats received a single intraperitoneal injection of 75 mg/kg EDS to eliminate Leydig cells and an in vitro culture system of the seminiferous tubules was established from Leydig cell-depleted testis. Using basal medium and Leydig cell differentiation-inducing medium (LIM) in the culture system, we examined the effects of DEX (0-100 nM) on the proliferation and differentiation of the stem Leydig cells in vitro, respectively.

RESULTS

Results showed that LIM is a good agent to induce stem Leydig cell differentiation into Leydig cells that produce testosterone in vitro. DEX inhibited the differentiation of stem Leydig cells by reducing the expression levels of Cyp17a1 and Scarb1 and that NR3C1 antagonist RU38486 reversed the DEX-mediated effects. However, DEX are not involved with the proliferation of stem Leydig cells.

CONCLUSIONS

DEX suppressed the differentiation of rat Leydig cells in vitro and glucocorticoid-induced effects acted through NR3C1. This suppression partially targets on Cyp17a1 and Scarb1 gene expression.

Androgen receptor expression is required to ensure development of adult Leydig cells and to prevent development of steroidogenic cells with adrenal characteristics in the mouse testis

Background

The interstitium of the mouse testis contains Leydig cells and a small number of steroidogenic cells with adrenal characteristics which may be derived from the fetal adrenal during development or may be a normal subset of the developing fetal Leydig cells. Currently it is not known what regulates development and/or proliferation of this sub-population of steroidogenic cells in the mouse testis. Androgen receptors (AR) are essential for normal testicular function and in this study we have examined the role of the AR in regulating interstitial cell development.

Results

Using a mouse model which lacks gonadotropins and AR (hpg.ARKO), stimulation of luteinising hormone receptors in vivo with human chorionic gonadotropin (hCG) caused a marked increase in adrenal cell transcripts/protein in a group of testicular interstitial cells. hCG also induced testicular transcripts associated with basic steroidogenic function in these mice but had no effect on adult Leydig cell-specific transcript levels. In hpg mice with functional AR, treatment with hCG induced Leydig cell-specific function and had no effect on adrenal transcript levels. Examination of mice with cell-specific AR deletion and knockdown of AR in a mouse Leydig cell line suggests that AR in the Leydig cells are likely to regulate these effects.

Conclusions

This study shows that in the mouse the androgen receptor is required both to prevent development of testicular cells with adrenal characteristics and to ensure development of an adult Leydig cell phenotype.

Electronic supplementary material

The online version of this article (10.1186/s12861-019-0189-5) contains supplementary material, which is available to authorized users.

Long-term maintenance of luteinizing hormone-responsive testosterone formation by primary rat Leydig cells in vitro

The inability of cultured primary Leydig cells to maintain luteinizing hormone (LH)-responsive testosterone formation in vitro for more than 3-5 days has presented a major challenge in testing trophic effects of regulatory factors or environmental toxicants. Our primary objective was to establish culture conditions sufficient to maintain LH-responsive testosterone formation by Leydig cells for at least a month. When isolated rat adult Leydig cells were cultured in DMEM/F12 and M199 culture medium containing insulin (10μg/ml), PDGFAA (10 ng/ml), lipoprotein (0.25 mg/ml), horse serum (1%) and a submaximal concentration of LH (0.2 ng/ml), the cells retained the ability to produce testosterone in vitro for at least 4 weeks. By using the longer-term culture conditions of this system, we were able to detect suppressive effects on testosterone production by low levels of the toxicant MEHP (mono-(2-ethylhexyl) phthalate), an active metabolite of the plasticizer DEHP, that were not detected by short-term culture.

Ziram Delays Pubertal Development of Rat Leydig Cells

Ziram [zinc, bis (dimethyldithiocarbamate)] is an agricultural dithiocarbamate fungicide. By virtual screening, we have identified that ziram is a potential endocrine disruptor. To investigate its effects on pubertal development of Leydig cells, 35-day-old male Sprague Dawley rats orally received ziram (2 or 4 mg/kg/d) for 4 weeks and immature Leydig cells isolated from 35-day-old rat testes were treated with ziram (0.5-50 μM in vitro). Serum hormones, Leydig cell number and specific gene or protein expression levels after in vivo treatment were determined and medium androgen levels were measured as well as apoptosis of Leydig cells after in vitro treatment were determined. In vivo exposure to ziram lowered testosterone and follicle-stimulating hormone levels, and reduced Leydig cell number, and downregulated Leydig cell specific gene or protein expression levels. Ziram exposure in vitro inhibited androgen production and steroidogenic enzyme activities in Leydig cells by downregulating expression levels of P450 cholesterol side cleavage enzyme (Cyp11a1), 3β-hydroxysteroid dehydrogenase 1 (Hsd3b1), 17α-hydroxylase/17,20-lyase (Cyp17a1), and 17β-hydroxysteroid dehydrogenase 3 (Hsd17b3) via downregulating the steroidogenic factor 1 (Nr5a1) at a concentration as low as 5 μM. In conclusion, ziram exposure disrupts Leydig cell development during puberty possibly via downregulating Nr5a1.

Recent progress in understanding the mechanisms of Leydig cell differentiation

Leydig cells in fetal and adult testes play pivotal roles in eliciting male characteristics by producing androgen. Although numerous studies of Leydig cells have been performed, the mechanisms for differentiation of the two cell types (fetal Leydig and adult Leydig cells), their developmental and functional relationship, and their differential characteristics remain largely unclear. Based on recent technical progress in genome-wide analysis and in vitro investigation, novel and fascinating observations concerning the issues above have been obtained. Focusing on fetal and adult Leydig cells, this review summarizes the recent progress that has advanced our understanding of the cells.

GATA4 is a transcriptional regulator of R-spondin1 in Japanese flounder (Paralichthys olivaceus)

GATA4 is a well-known transcription factor of the GATA family implicated in regulation of sex determination and gonadal development in mammals. In this study, we cloned the full-length cDNA of Paralichthys olivaceus gata4 (Po-gata4). Phylogenetic, gene structure, and synteny analysis showed that Po-GATA4 is homologous to GATA4 of teleost and tetrapod. Po-gata4 transcripts were detected in Sertoli cells, spermatogonia, oogonia and oocytes, with higher transcript levels overall in the testis than the ovary. The promoter region of P. olivaceus R-spondin1was found to contain a GATA4-binding motif. Results of CBA (cleaved amplified polymorphic sequence-based binding assay) indicated that GATA4 could indeed bind to the promoter sequence of R-spondin1. Moreover, human GATA4 recombinant protein could upregulate R-spondin1 in P. olivaceus ovary cells and FBCs (flounder brain cell line). In FBCs, overexpression of Po-gata4 resulted in elevated transcript levels of R-spondin1. Taken together, our results indicate that Po-GATA4 is involved in gonadal development by regulating R-spondin1 expression.

Diverged Effects of Piperine on Testicular Development: Stimulating Leydig Cell Development but Inhibiting Spermatogenesis in Rats

Background: Piperine is the primary pungent alkaloid isolated from the fruit of black peppercorns. Piperine is used frequently in dietary supplements and traditional medicines. The objective of the present study was to investigate the effects of piperine on the testis development in the pubertal rat.

Methods: Piperine (0 or 5 or 10 mg/kg) was gavaged to 35-day-old male Sprague-Dawley rats for 30 days. Serum levels of testosterone (T), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were measured. The development of adult Leydig cell population was also analyzed 65 days postpartum. For in vitro studies, immature Leydig cells were isolated from 35-day-old male rats and treated with 50 μM piperine in the presence of different steroidogenic stimulators/substrates for 24 h.

Results: Thirty-day treatment of rats with piperine significantly increased serum T levels without affecting LH concentrations. However, piperine treatment reduced serum FSH levels. Consistent with increase in serum T, piperine increased Leydig cell number, cell size, and multiple steroidogenic pathway proteins, including steroidogenic acute regulatory protein, cholesterol side-chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase 1, 17α-hydroxylase/20-lyase, and steroidogenic factor 1 expression levels. Piperine significantly increased the ratio of phospho-AKT1 (pAKT1)/AKT1, phosphos-AKT2 (pAKT2)/AKT2, and phospho-ERK1/2 (pERK1/2)/ERK1/2 in the testis. Interestingly, piperine inhibited spermatogenesis. Piperine in vitro also increased androgen production and stimulated cholesterol side-chain cleavage enzyme and 17α-hydroxylase/20-lyase activities in immature Leydig cells.

Conclusion: Piperine stimulates pubertal Leydig cell development by increasing Leydig cell number and promoting its maturation while it inhibits spermatogenesis in the rat. ERK1/2 and AKT pathways may involve in the piperine-mediated stimulation of Leydig cell development.

Numeric and volumetric changes in Leydig cells during aging of rats

PURPOSE

To analyze the effects of aging in rats on the nuclear volume, cytoplasmic volume, and total volume of Leydig cells, as well as their number.

METHODS

Seventy-two Wistar rats were divided into six subgroups of 12 rats, which underwent right orchiectomy at 3, 6, 9, 12, 18, and 24 months of age. The weight and volume of the resected testicles were assessed. A stereological study of Leydig cells was conducted, which included measurements of cell number and nuclear, cytoplasmic, and total cell volumes.

RESULTS

The weight and volume of the resected testicles showed reductions with age. Only the subgroup composed of 24-month old rats showed a decrease in the nuclear volume of Leydig cells. Significant reductions in the cytoplasmic volume and total volume of Leydig cells were observed in 18- and 24-month old rats. The number of Leydig cells did not vary significantly with age.

CONCLUSIONS

Aging in rats resulted in reduction of the nuclear, cytoplasmic, and total cell volumes of Leydig cells. There was no change in the total number of these cells during aging.

Vitamin A Promotes Leydig Cell Differentiation via Alcohol Dehydrogenase 1

Vitamin A (retinol) is important for multiple functions in mammals. In testis, the role of vitamin A in the regulation of testicular functions is clearly involved in rodents. It is essential for sperm production. Vitamin A deficiency adversely affects testosterone secretion. Adult Leydig cells are responsible for testosterone production in male. The role of vitamin A in regulating the differentiation of Leydig cells is still unknown. In this study, we explored the roles and underlying mechanisms of vitamin A in Leydig cell differentiation. We found that vitamin A could regulate the Leydig cells differentiation. Leydig cell differentiation is adversely affected in mice maintained on a vitamin A-free diet. This effect is mediated by alcohol dehydrogenase 1 (ADH1). ADH1 could increase retinoic acid (RA) synthesis, then RA facilitates Leydig cell differentiation by activating the steroidogenic factor 1 gene (Nr5a1) promoter activity, which consequently promotes Leydig cell specific gene expression, resulting in progenitor Leydig cells differentiation into functional Leydig cells. This is the first study connecting a metabolic enzyme of retinol (ADH1) to the the regulation of Leydig cell differentiation, which will provide experimental evidence for the development of therapeutics to promote Leydig regeneration through the administration of a RA signaling regulator or a vitamin A supplement.

Probing GATA factor function in mouse Leydig cells via testicular injection of adenoviral vectors

Testicular Leydig cells produce androgens essential for proper male reproductive development and fertility. Here, we describe a new Leydig cell ablation model based on Cre/Lox recombination of mouse Gata4 and Gata6, two genes implicated in the transcriptional regulation of steroidogenesis. The testicular interstitium of adult Gata4flox/flox ; Gata6flox/flox mice was injected with adenoviral vectors encoding Cre + GFP (Ad-Cre-IRES-GFP) or GFP alone (Ad-GFP). The vectors efficiently and selectively transduced Leydig cells, as evidenced by GFP reporter expression. Three days after Ad-Cre-IRES-GFP injection, expression of androgen biosynthetic genes (Hsd3b1, Cyp17a1 and Hsd17b3) was reduced, whereas expression of another Leydig cell marker, Insl3, was unchanged. Six days after Ad-Cre-IRES-GFP treatment, the testicular interstitium was devoid of Leydig cells, and there was a concomitant loss of all Leydig cell markers. Chromatin condensation, nuclear fragmentation, mitochondrial swelling, and other ultrastructural changes were evident in the degenerating Leydig cells. Liquid chromatography-tandem mass spectrometry demonstrated reduced levels of androstenedione and testosterone in testes from mice injected with Ad-Cre-IRES-GFP. Late effects of treatment included testicular atrophy, infertility and the accumulation of lymphoid cells in the testicular interstitium. We conclude that adenoviral-mediated gene delivery is an expeditious way to probe Leydig cell function in vivo Our findings reinforce the notion that GATA factors are key regulators of steroidogenesis and testicular somatic cell survival.Free Finnish abstract: A Finnish translation of this abstract is freely available at http://www.reproduction-online.org/content/154/4/455/suppl/DC2.

Insights into the Development of the Adult Leydig Cell Lineage from Stem Leydig Cells

Adult Leydig cells (ALCs) are the steroidogenic cells in the testes that produce testosterone. ALCs develop postnatally from a pool of stem cells, referred to as stem Leydig cells (SLCs). SLCs are spindle-shaped cells that lack steroidogenic cell markers, including luteinizing hormone (LH) receptor and 3β-hydroxysteroid dehydrogenase. The commitment of SLCs into the progenitor Leydig cells (PLCs), the first stage in the lineage, requires growth factors, including Dessert Hedgehog (DHH) and platelet-derived growth factor-AA. PLCs are still spindle-shaped, but become steroidogenic and produce mainly androsterone. The next transition in the lineage is from PLC to the immature Leydig cell (ILC). This transition requires LH, DHH, and androgen. ILCs are ovoid cells that are competent for producing a different form of androgen, androstanediol. The final stage in the developmental lineage is ALC. The transition to ALC involves the reduced expression of 5α-reductase 1, a step that is necessary to make the cells to produce testosterone as the final product. The transitions along the Leydig cell lineage are associated with the progressive down-regulation of the proliferative activity, and the up-regulation of steroidogenic capacity, with each step requiring unique regulatory signaling.