Regulation of development of rat stem and progenitor Leydig cells by activin

The role of platelet-derived growth factor BB signaling pathway in the regulation of stem and progenitor Leydig cell proliferation and steroidogenesis in male rats

Platelet-derived growth factor BB (BB) regulates cell proliferation and function. However, the roles of BB on proliferation and function of Leydig stem (LSCs) and progenitor cells (LPCs) and the underlying signaling pathways remain unclear. This study aimed to analyze the roles of PI3K and MAPK pathways in the regulation of proliferation-related and steroidogenesis-related gene expression in rat LSCs/LPCs. In this experiment, BB receptor antagonist, tyrosine kinase inhibitor IV (PKI), the PI3K inhibitor, LY294002, and the MEK inhibitor, U0126, were used to measure the effects of these pathways on the expression of cell cycle-related genes (Ccnd1 and Cdkn1b) and steroidogenesis-related genes (Star, Cyp11a1, Hsd3b1, Cyp17a1, and Srd5a1), as well as Leydig cell maturation gene Pdgfra [1]. These results showed that BB (10 ng/mL)-stimulated EdU-incorporation into LSCs and BB-mediated inhibition on its differentiation was mediated through the activation of its receptor, PDGFRB, as well as MAPK and PI3K pathways. The results of LPC experiment also showed that LY294002 and U0126 decreased BB (10 ng/mL)-upregulated Ccnd1 expression while only U0126 reversed BB (10 ng/mL)-downregulated Cdkn1b expression. U0126 significantly reversed BB (10 ng/mL)-mediated downregulation of Cyp11a1, Hsd3b1, and Cyp17a1 expression. On the other hand, LY294002 reversed the expression of Cyp17a1 and Abca1. In conclusion, BB-mediated induction of proliferation and suppression of steroidogenesis of LSCs/LPCs are dependent on the activation of both MAPK and PI3K pathways, which show distinct regulation of gene expression.

Ciliary neurotrophic factor stimulates stem/progenitor Leydig cell proliferation but inhibits differentiation into its lineage in rats

BACKGROUND

Ciliary neurotrophic factor is a member of the interleukin-6 family of cytokines. Ciliary neurotrophic factor drives many cells for their development. However, its effects on Leydig cell development remain unclear.

METHODS

In the current study, we used three-dimensional seminiferous tubule culture system to induce the proliferation and differentiation of tubule-associated stem Leydig cells and primary progenitor Leydig cells culture to address the effects of ciliary neurotrophic factor.

RESULTS

We found that ciliary neurotrophic factor stimulated the proliferation of stem Leydig cells but inhibited their development into the Leydig cell lineage. The ciliary neurotrophic factor-mediated effects can be reversed by signal transducer and activator 3 inhibitor S3I-201 and phosphatidylinositol 3-kinase inhibitor wortmannin, indicating that ciliary neurotrophic factor acts via signal transducer and activator 3-phosphatidylinositol 3-kinase signaling pathways to increase stem/progenitor Leydig cell proliferation. Ciliary neurotrophic factor at 1 and 10 ng/mL significantly decreased androgen production by progenitor Leydig cells. Microarray analysis of ciliary neurotrophic factor-treated progenitor Leydig cells showed that ciliary neurotrophic factor blocked steroidogenic pathways by downregulating Scarb1, Star, and Hsd3b1, possibly by downregulating the transcription factor Nr5a1 expression.

CONCLUSION

Ciliary neurotrophic factor stimulates proliferation but blocks the differentiation of stem/progenitor Leydig cells.

Insights into the Regulation on Proliferation and Differentiation of Stem Leydig Cells

Male hypogonadism is a clinical syndrome caused by testosterone deficiency. Hypogonadism can be caused by testicular disease (primary hypogonadism) or hypothalamic-pituitary dysfunction (secondary hypogonadism). The present strategy for treating hypogonadism is the administration of exogenous testosterone. But exogenous testosterone is reported to have negative side effects including adverse cardiovascular events and disruption of physiological spermatogenesis probably due to its inability to mimic the physiological circadian rhythm of testosterone secretion in vivo. In recent years, a growing number of articles demonstrated that stem Leydig cells (SLCs) can not only differentiate into functional Leydig cells (LCs) in vivo to replace chemically disrupted LCs, but also secrete testosterone in a physiological pattern. The proliferation and differentiation of SLCs are regulated by various factors. However, the mechanisms involved in regulating the development of SLCs remain to be summarized. Factors involved in the regulation of SLCs can be divided into environmental pollutants, growth factors, cytokine and hormones. Environmental pollutants such as Perfluorooctanoic acid (PFOA) and Triphenyltin (TPT) could suppress SLCs proliferation or differentiation. Growth factors including FGF1, FGF16, NGF and activin A are essential for the maintenance of SLCs self-renewal and differentiation. Interleukin 6 family could inhibit differentiation of SLCs. Among hormones, dexamethasone suppresses SLCs differentiation, while aldosterone suppresses their proliferation. The present review focuses on new progress about factors regulating SLC's proliferation and differentiation which will undoubtedly deepen our insights into SLCs and help make better clinical use of them. Different factors affect on the proliferation and differentiation of stem Leydig cells. Firstly, each rat was intraperitoneally injected EDS so as to deplete Leydig cells from the adult testis. Secondly, the CD51+ or CD90+ cells from the testis of rats are SLCs, and the p75+ cells from human adult testes are human SLCs. These SLCs in the testis start to proliferate and some of them differentiate into LCs. Thirdly, during the SLCs regeneration period, researchers could explore different function of those factors (pollutants, growth factors, cytokines and hormones) towards SLCs.

Stem Leydig cells: Current research and future prospects of regenerative medicine of male reproductive health

Stem cells are specialized cells that can renew themselves through cell division and can differentiate into multi-lineage cells. Mesenchymal stem cells are adult stem cells that exist in animal and human tissues. Mesenchymal stem cells have the ability to differentiate into mesodermal lineages, such as Leydig cells, adipocytes, osteocytes, and chondrocytes. Mesenchymal stem cells express cell surface markers, such as cluster of differentiation (CD) 29, CD44, CD73, CD90, CD105, and lack the expression of CD14, CD34, CD45 and HLA (human leukocyte antigen)-DR. Stem Leydig cells are one kind of mesenchymal stem cells, which are present in the interstitial compartment of testis. Stem Leydig cells are multipotent and can differentiate into Leydig cells, adipocytes, osteocytes, and chondrocytes. Stem Leydig cells have been isolated from rodent and human testes. Stem Leydig cells may have potential therapeutic values in several clinical applications, such as the treatment of male hypogonadism and infertility. In this review, we focus on the latest research on stem Leydig cells of both rodents and human, the expression of cell surface markers, culture, differentiation potential, and their applications.

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

Epidermal growth factor regulates the development of stem and progenitor Leydig cells in rats

Epidermal growth factor (EGF) has many physiological roles. However, its effects on stem and progenitor Leydig cell development remain unclear. Rat stem and progenitor Leydig cells were cultured with different concentrations of EGF alone or in combination with EGF antagonist, erlotinib or cetuximab. EGF (1 and 10 ng/mL) stimulated the proliferation of stem Leydig cells on the surface of seminiferous tubules and isolated CD90⁺ stem Leydig cells and progenitor Leydig cells but it blocked their differentiation. EGF also exerted anti‐apoptotic effects of progenitor Leydig cells. Erlotinib and cetuximab are able to reverse EGF‐mediated action. Gene microarray and qPCR of EGF‐treated progenitor Leydig cells revealed that the down‐regulation of steroidogenesis‐related proteins (Star and Hsd3b1) and antioxidative genes. It was found that EGF acted as a proliferative agent via increasing phosphorylation of AKT1. In conclusion, EGF stimulates the proliferation of rat stem and progenitor Leydig cells but blocks their differentiation.

Food components and environmental chemicals of inhibiting human placental aromatase

Human placental CYP19A1 catalyzes the estrogen synthesis from androgens. The enzyme is encoded by CYP19A1 gene located in chromosome 15q21. This enzyme is a monooxygenase in the smooth endoplasmic reticulum. The various promoters of the CYP19A1 gene determine its expression in different tissues and the distal promoter I.1 controls its expression in the placenta and retinoids can regulate the expression. Many food components and environmental chemicals inhibit CYP19A1 activity via different modes of action. These chemicals include gossypol, flavones, flavanones, chalconoids, resveratrol, and tobacco alkaloids derived from foods as well as phthalates, insecticides, fungicides, and biocides in the contaminated foods. The inhibition of placental CYP19A1 could impair pregnancy.

Modulation of the transcriptomic profile of the R2C tumor Leydig cell line by the adipose tissue derived hormone leptin

Leptin is an important adipose derived hormone being secreted by adipocytes and involved in appetite regulation. Disruption of normal plasma levels of leptin has been associated with the pathogenesis of obesity. It is now well established that obesity is associated to an increased risk of cancer development, including testicular cancers. Recently, we have shown that high levels of leptin have inhibitory effects on cAMP-dependent steroidogenic genes expression in MA-10 Leydig cells. Hence, we examined if leptin could alter the transcriptome of the constitutively steroidogenic rat tumor Leydig cell line R2C. These cells were treated with high levels of leptin (1000 ng/ml) for 4 h, followed by mRNA extraction and RNA-Seq analysis. Interestingly, leptin had no effect on steroidogenic gene expression or pathways promoting tumorigenesis of this cell line. Genes being upregulated or downregulated by leptin were enriched in biological processes that were non-relevant to Leydig cell function. Surprisingly, lepr isoforms were weakly expressed in R2C cells and may explain in part the low levels of leptin's response for tumor Leydig cells. Hence, the current findings suggest that acute treatments of tumor Leydig cells with high levels of leptin have negligible effects on transcriptomics and rather supports that leptin would have a central effect on the hypothalamus to influence testicular function.

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.

Effects of Fungicides on Rat's Neurosteroid Synthetic Enzymes

Exposure to environmental endocrine disruptors may interfere with nervous system's activity. Fungicides such as tebuconazole, triadimefon, and vinclozolin have antifungal activities and are used to prevent fungal infections in agricultural plants. In the present study, we studied effects of tebuconazole, triadimefon, and vinclozolin on rat's neurosteroidogenic 5α-reductase 1 (5α-Red1), 3α-hydroxysteroid dehydrogenase (3α-HSD), and retinol dehydrogenase 2 (RDH2). Rat's 5α-Red1, 3α-HSD, and RDH2 were cloned and expressed in COS-1 cells, and effects of these fungicides on them were measured. Tebuconazole and triadimefon competitively inhibited 5α-Red1, with IC50 values of 8.670 ± 0.771 × 10-6 M and 17.390 ± 0.079 × 10-6 M, respectively, while vinclozolin did not inhibit the enzyme at 100 × 10-6 M. Triadimefon competitively inhibited 3α-HSD, with IC50 value of 26.493 ± 0.076 × 10-6 M. Tebuconazole and vinclozolin weakly inhibited 3α-HSD, with IC50 values about 100 × 10-6 M, while vinclozolin did not inhibit the enzyme even at 100 × 10-6 M. Tebuconazole and triadimefon weakly inhibited RDH2 with IC50 values over 100 × 10-6 M and vinclozolin did not inhibit this enzyme at 100 × 10-6 M. Docking study showed that tebuconazole, triadimefon, and vinclozolin bound to the steroid-binding pocket of 3α-HSD. In conclusion, triadimefon potently inhibited rat's neurosteroidogenic enzymes, 5α-Red1 and 3α-HSD.

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.