Leukemia Inhibitory Factor-Receptor is Dispensable for Prenatal Testis Development but is Required in Sertoli cells for Normal Spermatogenesis in Mice

Sertoli cells are the source of stem cell factor for spermatogenesis

Several cell types have been proposed to create the required microenvironment for spermatogenesis. However, expression patterns of the key growth factors produced by these somatic cells have not been systematically studied and no such factor has been conditionally deleted from its primary source(s), raising the question of which cell type(s) are the physiological sources of these growth factors. Here, using single-cell RNA sequencing and a series of fluorescent reporter mice, we found that stem cell factor (Scf), one of the essential growth factors for spermatogenesis, was broadly expressed in testicular stromal cells, including Sertoli, endothelial, Leydig, smooth muscle and Tcf21-CreER+ stromal cells. Both undifferentiated and differentiating spermatogonia were associated with Scf-expressing Sertoli cells in the seminiferous tubule. Conditional deletion of Scf from Sertoli cells, but not any other Scf-expressing cells, blocked the differentiation of spermatogonia, leading to complete male infertility. Conditional overexpression of Scf in Sertoli cells, but not endothelial cells, significantly increased spermatogenesis. Our data reveal the importance of anatomical localization for Sertoli cells in regulating spermatogenesis and that SCF produced specifically by Sertoli cells is essential for spermatogenesis.

Lhb-/-Lhr-/- Double Mutant Mice Phenocopy Lhb-/- or Lhr-/- Single Mutants and Display Defects in Leydig Cells and Steroidogenesis

In the mouse, two distinct populations of Leydig cells arise during testis development. Fetal Leydig cells arise from a stem cell population and produce T required for masculinization. It is debated whether they persist in the adult testis. A second adult Leydig stem cell population gives rise to progenitor-immature-mature adult type Leydig cells that produce T in response to LH to maintain spermatogenesis. In testis of adult null male mice lacking either only LH (Lhb^-/-) or LHR (Lhr^-/-), mature Leydig cells are absent but fetal Leydig cells persist. Thus, it is not clear whether other ligands signal via LHRs in Lhb null mice or LH signals via other receptors in the absence of LHR in Lhr null mice. Moreover, it is not clear whether truncated LHR isoforms generated from the same Lhr gene promoter encode functionally relevant LH receptors. To determine the in vivo roles of LH-LHR signaling pathway in the Leydig cell lineage, we generated double null mutant mice lacking both LH Ligand and all forms of LHR. Phenotypic analysis indicated testis morpho-histological characteristics are identical among double null and single mutants which all showed poorly developed interstitium with a reduction in Leydig cell number and absence of late stage spermatids. Gene expression analyses confirmed that the majority of the T biosynthesis pathway enzyme-encoding mRNAs expressed in Leydig cells were all suppressed. Expression of thrombospondin-2, a fetal Leydig cell marker gene was upregulated in single and double null mutants indicating that fetal Leydig cells originate and develop independent of LH-LHR signaling pathway in vivo. Serum and intratesticular T levels were similarly suppressed in single and double mutants. Consequently, expression of AR-regulated genes in Sertoli and germ cells were similarly affected in single and double mutants without any evidence of any additive effect in the combined absence of both LH and LHR. Our studies unequivocally provide genetic evidence that in the mouse testis, fetal Leydig cells do not require LH-LHR signaling pathway and a one-to-one LH ligand-LHR signaling pathway exists in vivo to regulate adult Leydig cell lineage and spermatogenesis.

Leukemia inhibitory factor-receptor signalling negatively regulates gonadotrophin-stimulated testosterone production in mouse Leydig Cells

Testicular Leydig cells (LCs) are the principal source of circulating testosterone in males. LC steroidogenesis maintains sexual function, fertility and general health, and is influenced by various paracrine factors. The leukemia inhibitory factor receptor (LIFR) is expressed in the testis and activated by different ligands, including leukemia inhibitory factor (LIF), produced by peritubular myoid cells. LIF can modulate LC testosterone production in vitro under certain circumstances, but the role of consolidated signalling through LIFR in adult LC function in vivo has not been established. We used a conditional Lifr allele in combination with adenoviral vectors expressing Cre-recombinase to generate an acute model of LC Lifr-KO in the adult mouse testis, and showed that LC Lifr is not required for short term LC survival or basal steroidogenesis. However, LIFR-signalling negatively regulates steroidogenic enzyme expression and maximal gonadotrophin-stimulated testosterone biosynthesis, expanding our understanding of the intricate regulation of LC steroidogenic function.

Culture supplementation of bFGF, GDNF, and LIF alters in vitro proliferation, colony formation, and pluripotency of neonatal porcine germ cells

Gonocytes in the neonatal testis have male germline stem cell properties and as such have important potential applications in fertility preservation and regenerative medicine. Such applications require further studies aimed at increasing gonocyte numbers and evaluating their pluripotency in vitro. The objective of the present study was to test the effects of basic fibroblast growth factor (bFGF), glial cell line-derived neurotrophic factor (GDNF), and leukemia inhibitory factor (LIF) on in vitro propagation, colony formation, and expression of pluripotency markers of neonatal porcine gonocytes. Testis cells from 1-week-old piglets were cultured in basic media (DMEM + 15% FBS), supplemented with various concentrations of bFGF, GDNF, and LIF, either individually or in combinations, in a stepwise experimental design. Gonocytes and/or their colonies were evaluated every 7 days and the gonocyte- (DBA) and pluripotency-specific markers (POU5F1, SSEA-1, E-cadherin, and NANOG) assessed on day 28. Greatest gonocyte numbers and largest colonies were found in media supplemented with 10 ng/mL bFGF and 10 ng/mL bFGF + 100 ng/mL GDNF + 1500 U/mL LIF, respectively. The resultant gonocytes and colonies expressed both germ cell- and pluripotency-specific markers. These results shed light on the growth hormone requirements of porcine gonocytes for in vitro proliferation and colony formation.

Comparative transcriptome analysis reveals potential testosterone function-related regulatory genes/pathways of Leydig cells in immature and mature buffalo (Bubalus bubalis) testes

Leydig cells (LCs) are testosterone-generating endocrine cells that are located outside the seminiferous tubules in the testis, and testosterone is fundamental for retaining spermatogenesis and male fertility. In buffalo, adult Leydig cells (ALCs) are developed by immature Leydig cells (ILCs) in the postnatal testes. However, the genes/pathways associated to the regulation of testosterone secretion function during the development of postnatal LCs remains comprehensively unidentified. The present study comparatively analyzed the transcriptome profiles of ILC and ALC in buffalo with significant differences in testosterone secretion. Differentially expressed genes (DEGs) analysis identified 972 and 1,091 annotated genes that were significantly up- and down-regulated in buffalo ALC. Functional enrichment analysis showed that cAMP signaling being the most significantly enriched pathway, and testosterone synthesis and lipid transport-related genes/pathways were upregulated in ALC. Furthermore, gene set enrichment analysis (GSEA) shows that cAMP signaling and steroid hormone biosynthesis were activated in ALC, demonstrating that cAMP signaling may serve as a positive regulatory pathway in the maintenance of testosterone function during postnatal development of LCs. Protein-protein interaction (PPI) networks analysis highlighted that ADCY8, ADCY2, POMC, CHRM2, SST, PTGER3, SSTR2, SSTR1, NPY1R, and HTR1D as hub genes in the cAMP signaling pathway. In conclusion, this study identified key genes and pathways associated in the regulation of testosterone secretion function during the ILC-ALC transition in buffalo based on bioinformatics analysis, and these key genes might be deeply involved in cAMP generation to influencing testosterone levels in LCs. The results suggest that ALCs might increase testosterone levels by enhancing cAMP production than ILCs. Our data will enhance the understanding of developmental mechanism studies related to testosterone function and provide preliminary evidence for molecular mechanisms of LCs regulating spermatogenesis.

Differentially expressed microRNA in testicular tissues of hyperuricaemia rats

This study is to identify the differentially expressed miRNAs in testicular tissues of rats with hyperuricaemia-induced male infertility. We found that the hyperuricaemia model group had significantly increased serum uric acid, while significantly decreased sperm concentration and motile sperm percentage than normal group (p < .05). A total of 39 differentially expressed miRNAs were identified in the testicular tissues of hyperuricaemia rats compared with the control rats, ten of which were validated by real-time PCR. The target mRNAs of 7 differentially expressed miRNAs (miR-10b-5p, miR-26a-5p, miR-136-5p, miR-151-3p, miR-183-5p, miR-362-3p and miR-509-5p) from 3'-untranslated region binding perspective were enriched in signalling pathways of Wnt, Jak-STAT, mTOR and MAPK. The target mRNAs of 6 differentially expressed miRNAs (miR-136-5p, miR-144-3p, miR-99a-5p, miR-509-5p, miR-451-5p and miR-362-3p) from coding sequence binding perspective were enriched in signalling pathways of Calcium, Notch and MAPK. The functions of miRNAs in testicular tissues of rats with hyperuricaemia were revealed by the differentially expressed miRNAs (miR-183-5p, miR-99a-5p, miR-10b-5p, miR-151-3p, miR-26a-5p, miR-451-5p, miR-362-3p, miR-136-5p, miR-144-3p and miR-509-5p)-mRNAs interaction network. The differentially expressed miRNAs in the testicular tissues of hyperuricaemia rats might shed light on the mechanism of hyperuricaemia-induced male infertility.

Effect of macrophages in semen on sperm quality

BACKGROUND

This was a cross-sectional study in China which analyzed the levels of macrophages (Mφ) in semen and evaluated the influence of Mφ levels in semen on sperm quality.

METHODS

The subjects involves 78 males, 25- to 35-year old. The samples were divided into a low group (Mφ < 6 × 105/ml) and a high group (Mφ > 6 × 105/ml). Evaluation included consideration of the influencing factors of male semen quality, macrophage concentration, sperm motility, morphology, membrane integrity DNA fragmentation index (DFI), anti-sperm antibodies (AsAb), IL-10, and IL-12 in semen.

RESULTS

There was no difference in the physical or chemical indices of the semen, sperm concentration, AsAb, IL-10, or IL-12 between the two groups (P > 0.05). The percentage of sperm forward motility (PR%), the rate of normal sperm shape, and the integrity of cell membranes in the low group were higher than those in the high group (P < 0.05), while the percentage of sperm inactivity (IM%), the rate of sperm head deformity, the rate of deformity in the neck and middle segment, the sperm deformity index (SDI), the teratozoospermia index (TZI), and the sperm DFI in the low group were lower than those in the high group (P < 0.05). The concentration of Mφ in the semen was linearly correlated with sperm concentration, sperm PR%, IM%, sperm normal shape rate, head deformity rate, neck and middle deformity rate, SDI, TZI, sperm DFI, and sperm cell membrane integrity (P < 0.05), but there was no linear correlation with IL-10 or IL-12 (P > 0.05).

CONCLUSIONS

The Mφ concentration in semen is not significantly correlated with semen volume or sperm concentration, but negatively correlated with sperm motility, morphology, cell membrane integrity, and DNA damage rate. There is no significant correlation between the macrophages and the concentration of IL-10 or IL-12.

Expression profile of microRNAs in the testes of patients with Klinefelter syndrome

Klinefelter syndrome (KS) is the most common sex chromosome aneuploidy. A distinctive characteristic of KS is oligozoospermia. Despite multiple studies that have described the natural history of the degenerative process of germ cells in patients with KS, the molecular mechanisms that initiate this process are not well characterized. MicroRNA (miRNA)-mediated post-transcriptional control mechanisms have been increasingly recognized as important regulators of spermatogenesis; however, only a few studies have evaluated the role of miRNAs in the gonadal failure of these patients. Here, we describe a differential expression profile for the miRNAs in testicular tissue samples taken from KS patients. We analysed testicular tissue samples from 4 KS patients and 5 control patients (obstructive azoospermia) through next-generation sequencing, which can provide information about the mechanisms involved in the degeneration of germ cells. A distinctive differential expression profile was identified for 166 miRNAs in the KS patients: 66 were upregulated, and 100 were downregulated. An interactome analysis was performed for 7 of the upregulated and the 20 downregulated miRNAs. The results showed that the target genes are involved in the development, proliferation, and differentiation processes of spermatogenesis, which may explain their role in the development of infertility. This is the first report of a miRNA expression profile generated from testicular tissue samples of KS patients.

Function of leukaemia inhibitory factor in spermatogenesis of a teleost fish, the medaka Oryzias latipes

In response to gonadotropins and androgens, testicular cells produce various molecules that control proper proliferation and differentiation of spermatogenic cells through their paracrine and autocrine actions. However, molecules functioning downstream of the hormonal stimulation are poorly understood. Leukaemia inhibitory factor (Lif) is known to maintain the pluripotency of stem cells including embryonic stem cells and primordial germ cells at least in vitro, but its actual roles in vivo remain to be elucidated. To clarify the function of Lif in teleost (medaka) testes, we examined the effects of Lif on spermatogenesis in a newly established cell culture system using a cell line (named Mtp1) derived from medaka testicular somatic cells as feeder cells. We found that addition of baculovirus-produced recombinant medaka Lif to the culture medium or co-culture with Lif-overexpressing Mtp1 cells increased the number of spermatogonia. In situ hybridization and immunohistochemical analyses of the medaka testes showed that mRNAs and proteins of Lif are expressed in spermatogonia and the surrounding Sertoli cells, with higher expression levels in type A (undifferentiated) spermatogonia than in type B (differentiated) spermatogonia. Our findings suggest that Lif regulates spermatogonial cell proliferation in the medaka.

The roles and mechanisms of Leydig cells and myoid cells in regulating spermatogenesis

Spermatogenesis is fundamental to the establishment and maintenance of male reproduction, whereas its abnormality results in male infertility. Somatic cells, including Leydig cells, myoid cells, and Sertoli cells, constitute the microenvironment or the niche of testis, which is essential for regulating normal spermatogenesis. Leydig cells are an important component of the testicular stroma, while peritubular myoid cells are one of the major cell types of seminiferous tubules. Here we addressed the roles and mechanisms of Leydig cells and myoid cells in the regulation of spermatogenesis. Specifically, we summarized the biological features of Leydig cells and peritubular myoid cells, and we introduced the process of testosterone production and its major regulation. We also discussed other hormones, cytokines, growth factors, transcription factors and receptors associated with Leydig cells and myoid cells in mediating spermatogenesis. Furthermore, we highlighted the issues that are worthy of further studies in the regulation of spermatogenesis by Leydig cells and peritubular myoid cells. This review would provide novel insights into molecular mechanisms of the somatic cells in controlling spermatogenesis, and it could offer new targets for developing therapeutic approaches of male infertility.

JAK/STAT signaling in stem cells and regeneration: from Drosophila to vertebrates

The JAK/STAT pathway is a conserved metazoan signaling system that transduces cues from extracellular cytokines into transcriptional changes in the nucleus. JAK/STAT signaling is best known for its roles in immunity. However, recent work has demonstrated that it also regulates critical homeostatic processes in germline and somatic stem cells, as well as regenerative processes in several tissues, including the gonad, intestine and appendages. Here, we provide an overview of JAK/STAT signaling in stem cells and regeneration, focusing on Drosophila and highlighting JAK/STAT pathway functions in proliferation, survival and cell competition that are conserved between Drosophila and vertebrates.