Spermatogenesis is a continuous and productive process supported by the self-renewal and differentiation of spermatogonial stem cells (SSCs), which arise from undifferentiated precursors known as gonocytes and are strictly controlled in a special ‘niche’ microenvironment in the seminiferous tubules. Sertoli cells, the only somatic cell type in the tubules, directly interact with SSCs to control their proliferation and differentiation through the secretion of specific factors. Spermatocyte meiosis is another key step of spermatogenesis, which is regulated by Sertoli cells on the luminal side of the blood–testis barrier through paracrine signaling. In this review, we mainly focus on the role of Sertoli cells in the regulation of SSC self-renewal and spermatocyte meiosis, with particular emphasis on paracrine and endocrine-mediated signaling pathways. Sertoli cell growth factors, such as glial cell line-derived neurotrophic factor (GDNF) and fibroblast growth factor 2 (FGF2), as well as Sertoli cell transcription factors, such as ETS variant 5 (ERM; also known as ETV5), nociceptin, neuregulin 1 (NRG1), and androgen receptor (AR), have been identified as the most important upstream factors that regulate SSC self-renewal and spermatocyte meiosis. Other transcription factors and signaling pathways (GDNF–RET–GFRA1 signaling, FGF2–MAP2K1 signaling, CXCL12–CXCR4 signaling, CCL9–CCR1 signaling, FSH–nociceptin/OPRL1, retinoic acid/FSH–NRG/ERBB4, and AR/RB–ARID4A/ARID4B) are also addressed.
Su-Ren Chen and Yi-Xun Liu
Yu-Qian Wang, Aalia Batool, Su-Ren Chen and Yi-Xun Liu
Reduced contractility of the testicular peritubular myoid (PTM) cells may contribute to human male subfertility or infertility. Transcription factor GATA4 in Sertoli and Leydig cells is essential for murine spermatogenesis, but limited attention has been paid to the potential role of GATA4 in PTM cells. In primary cultures of mouse PTM cells, siRNA knockdown of GATA4 increased the contractile activity, while GATA4 overexpression significantly attenuated the contractility of PTM cells using a collagen gel contraction assay. Using RNA sequencing and qRT-PCR, we identified a set of genes that exhibited opposite expressional alternation between Gata4 siRNA vs nontargeting siRNA-treated PTM cells and Gata4 adenovirus vs control adenovirus-treated PTM cells. Notably, ion channels, smooth muscle function, cytokines and chemokines, cytoskeleton, adhesion and extracellular matrix were the top four enriched pathways, as revealed by cluster analysis. Natriuretic peptide type B (NPPB) content was significantly upregulated by GATA4 overexpression in both PTM cells and their culture supernatant. More importantly, the addition of 100 μM NPPB could abolish the promoting effect of Gata4 silencing on PTM cell contraction. Taken together, we suggest that the inhibitory action of GATA4 on PTM cell contraction is mediated at least partly by regulating genes belonging to smooth muscle contraction pathway (e.g. Nppb).
Su Liu, Hongxia Wei, Yuye Li, Lianghui Diao, Ruochun Lian, Xu Zhang and Yong Zeng
During pregnancy, the maternal immune system must tolerate the persistence of semi-allogeneic fetus in the maternal tissue. Inadequate recognition of fetal antigens may lead to pregnancy complications, such as recurrent miscarriage (RM) and recurrent implantation failure (RIF). Dendritic cells (DCs) are key regulators of protective immune responses and the development and maintenance of tolerance. Regarding that DCs are important in the establishment of immune tolerance in human pregnancy, it would be important to study the microenvironment in which DCs reside or are activated may affect their functions toward tolerance rather than active immune response. IL-10 plays a critical role in the maintenance of normal pregnancy, and the increased production of IL-10 is associated with successful pregnancy. In this study, we provide an in-depth comparison of the phenotype and cytokine production by DC-10 and other DC subsets, such as iDC and mDC. CD14+ monocyte-derived DCs were differentiated in the presence of IL-10 (DC-10) in vitro from ten normal fertile controls, six RM women and seven RIF women, and characterized for relevant markers. DC-10 was characterized by relatively low expression of costimulatory molecule CD86, as well as MHC class II molecule HLA-DR, high expression of tolerance molecules HLA-G, ILT2, ILT4 and immunosuppressive cytokine IL-10, but produced little or no proinflammatory cytokines, such as TNF-α, IL-6 and IL-12p70. Our study provides a better understanding of the phenotypical properties of DC-10, which may participate in the complex orchestration that leads to maternal immune tolerance and homeostatic environment in human pregnancy.
Cheng Jin, Yan Zhang, Zhi-Peng Wang, Xiu-Xia Wang, Tie-Cheng Sun, Xiao-Yu Li, Ji-Xin Tang, Jin-Mei Cheng, Jian Li, Su-Ren Chen, Shou-Long Deng and Yi-Xun Liu
Spermatogenesis is crucial for male fertility and is therefore tightly controlled by a variety of epigenetic regulators. However, the function of enhancer of zeste homolog 2 (EZH2) in spermatogenesis and the molecular mechanisms underlying its activity remain poorly defined. Here, we demonstrate that deleting EZH2 promoted spermatogonial differentiation and apoptosis. EZH2 is expressed in spermatogonia, spermatocytes and round and elongated spermatids from stage 9 to 11 but not in leptotene and zygotene spermatocytes. Knocking down Ezh2 in vitro using a lentivirus impaired self-renewal in spermatogonial stem cells (SSCs), and the conditional knockout of Ezh2 in spermatogonial progenitors promoted precocious spermatogonial differentiation. EZH2 functions to balance self-renewal and differentiation in spermatogonia by suppressing NEUROG3 and KIT via a direct interaction that is independent of its histone methyltransferase activity. Moreover, deleting Ezh2 enhanced the activation of CASP3 in spermatids, resulting in reduced spermatozoa production. Collectively, these data demonstrate that EZH2 plays a nonclassical role in the regulation of spermatogonial differentiation and apoptosis in murine spermatogenesis.
Qiao-Song Zheng, Xiao-Na Wang, Qing Wen, Yan Zhang, Su-Ren Chen, Jun Zhang, Xi-Xia Li, Ri-Na Sha, Zhao-Yuan Hu, Fei Gao and Yi-Xun Liu
Spermatogenesis is a complex process involving the regulation of multiple cell types. As the only somatic cell type in the seminiferous tubules, Sertoli cells are essential for spermatogenesis throughout the spermatogenic cycle. The Wilms tumor gene, Wt1, is specifically expressed in the Sertoli cells of the mouse testes. In this study, we demonstrated that Wt1 is required for germ cell differentiation in the developing mouse testes. At 10 days post partum, Wt1-deficient testes exhibited clear meiotic arrest and undifferentiated spermatogonia accumulation in the seminiferous tubules. In addition, the expression of claudin11, a marker and indispensable component of Sertoli cell integrity, was impaired in Wt1 −/flox; Cre-ER TM testes. This observation was confirmed in in vitro testis cultures. However, the basal membrane of the seminiferous tubules in Wt1-deficient testes was not affected. Based on these findings, we propose that Sertoli cells' status is affected in Wt1-deficient mice, resulting in spermatogenesis failure.