Activated Notch2 signaling inhibits differentiation of cerebellar granule neuron precursors by maintaining proliferation.

In the developing cerebellar cortex, granule neuron precursors (GNPs) proliferate and commence differentiation in a superficial zone, the external granule layer (EGL). The molecular basis of the transition from proliferating precursors to immature differentiating neurons remains unknown. Notch signaling is an evolutionarily conserved pathway regulating the differentiation of precursor cells of many lineages. Notch2 is specifically expressed in proliferating GNPs in the EGL. Treatment of GNPs with soluble Notch ligand Jagged1, or overexpression of activated Notch2 or its downstream target HES1, maintains precursor proliferation. The addition of GNP mitogens Jagged1 or Sonic Hedgehog (Shh) upregulates the expression of HES1, suggesting a role for HES1 in maintaining precursor proliferation.     

Direct effect of gonadotropins on decidualization of human endometrial stromal cells

Decidualization of stromal cells isolated from proliferative human endometrium was achieved by adding to the culture medium human gonadotropins (FSH, FSH + LH, hCG). In addition to changes in the morphology of the stromal cells to the decidual phenotype, decidualization was evident from the expression of prolactin (PRL), demonstrated immunocytochemically, by Western blotting analysis, and by measuring its output into the medium through solid phase enzyme immunoassay. Gonadotropins also induced cAMP formation in the endometrial stromal cells under the same experimental conditions. This finding suggests that the mechanism by which gonadotropins promote decidualization of human endometrial stromal cells in vitro involves the introduction of cAMP, a compound that we have found to elicit the expression of PRL in this system. PRL is likely to be a key intermediate in the process of decidualization since it is by itself capable of inducing differentiation of the endometrial stromal cells to the decidual phenotype. Awareness of direct actions of gonadotropins on the endometrial cells and, in particular, of the decidualizing effects of FSH (Metrodin), FSH + LH (Pergonal) and hCG may contribute to the understanding of physiologic as well as pathophysiologic conditions relevant to endometrial functions and fertility.     

人骨髓间充质干细胞向神经细胞分化过程中Notch通路信号分子表达的变化

本研究探讨Noah信号通路在人骨髓间充质干细胞（human mesenchymal stem cells,hMSCs）体外增殖及向神经细胞分化过程中的作用。采集健康自愿者骨髓,体外培养获得hMSCs,取第3代hMSCs,在诱导剂（β-ME,DMSO,BHA）作用下向神经细胞分化。诱导后用免疫细胞化学鉴定神经元特异性烯醇化酶（neuron-specific enolase,NSE）和尼氏体的表达以确定诱导效果：用流式细胞术检测细胞生长周期时相的变化。在诱导前后,用免疫荧光和RT-PCR方法检测Notch通路中Notch1受体蛋白、配体Jagged1（JAG1）、调节蛋白活化相关物早老素1（presenilin 1,PS1）、靶基因hairy and enhancer of split1（HES1）信号分子表达的变化。结果显示：诱导前,处于G0/G1期的hMSCs占58．5％,S＋G2/M期的细胞占41．5％;诱导后,G0/G1期细胞比例升高,而S＋G2/M期细胞比例下降,NSE阳性细胞率达（77±0．35）％,细胞质中可见深蓝色的块状或颗粒状尼氏体。免疫荧光显示,诱导前后hMSCs内Notch1和JAG1均呈阳性表达,但RT-PCR检测发现诱导后Notch1、JAG1、PSl和HES1 mRNA表达量较诱导前明显降低（均P〈0．05）。结果表明,诱导hMSCs向神经细胞分化能抑制Notch信号分子表达,低水平的Notch信号激活可能有利于神经细胞的分化。     

Murine and human hematopoietic progenitor cultures grown on stromal layers expressing Notch ligands

The ex vivo maintenance and expansion of hematopoietic stem cells and early progenitors is necessary for the successful treatment of hematopoietic and immune diseases. Multiple attempts to improve the expansion of hematopoietic stem cells (HSCs) by their cultivation in the presence of growth factor cocktails have so far failed. Novel approaches aimed at conserving the earliest precursors in their undifferentiated state are needed. These approaches should take into account local regulatory factors that are present in the HSC microenvironment and the three-dimensional architecture of their niche. In the present study, we compared the effects of two Notch ligands, i.e., Jagged1 and DLL1, on murine and human hematopoiesis in vitro. Our observations indicate that the stromal expression of Notch ligands increases the production of both the total and phenotypically early murine and human hematopoietic cells in the co-culture. On one hand, this study demonstrates the similarity of effects of stromal expression of Notch ligands on murine and human hematopoiesis in vitro. On the other hand, our study revealed a number of cell type and ligand-specific variations that are systematically described below. It seems that the effects of SCF cytokine addition on murine hematopoiesis in vitro depend on the stromal context and are oppositely directed for Jagged1 and DLL1.     

Autocrine prolactin inhibits human uterine decidualization: a novel role for prolactin

Human prolactin (PRL) and its receptor (PRLR) are markedly induced during human uterine decidualization, and large amounts of PRL are released by decidual cells as differentiation progresses. However, the role of PRL in decidualization is unknown. In order to determine whether PRL plays an autocrine role in decidualization, human uterine fibroblast cells that were decidualized in vitro with medroxyprogestrerone acetate (1 microM), estradiol (10 nM), and prostaglandin E(2) (1 microM) were exposed to exogenous PRL and/or the pure PRLR antagonist delta1-9-G129R-PRL. As measured by quantitative PCR, cells that were decidualized in the presence of exogenous PRL (0.25-2 microg/ml) expressed significantly lower levels of mRNA for the genes that encode insulin-like growth factor binding protein 1 (IGFBP1), left-right determination factor 2 (LEFTY2), PRL, decorin (DCN), and laminin alpha 1 (LAMA1), all of which are known to be induced during decidualization. These effects were blocked when the cells were exposed simultaneously to PRL and the PRLR antagonist, which confirms the specific inhibitory action of PRL on the expression of decidualization markers. In addition, cells exposed to the PRLR antagonist alone expressed higher levels of the marker gene mRNAs than cells that were decidualized in control media. Taken together, these results strongly suggest that PRL acts via an autocrine mechanism to regulate negatively the extent of differentiation (decidualization) of human uterine cells.     

Porphyromonas gingivalis lipopolysaccharide inhibits the osteoblastic differentiation of preosteoblasts by activating Notch1 signaling

Although Porphyromonas gingivalis lipopolysaccharide (P‐LPS) is known to inhibit osteoblast differentiation, the exact molecular mechanisms underlying this phenomenon remain unclear. Here, we investigated the role of Notch signaling in the osteoblastic differentiation of both MC3T3E‐1 cells and primary mouse bone marrow stromal cells (BMSCs). P‐LPS stimulation activated the Notch1 signaling cascade and increased expression of the Notch target genes HES1 and HEY1. P‐LPS can also act as an inhibitor because it is capable of suppressing Wnt/β‐catenin signaling in preosteoblasts by decreasing both glycogen synthase kinase‐3β (GSK‐3β) phosphorylation and the expression of nuclear β‐catenin. These effects were rescued, however, by inhibiting Notch1 signaling. Furthermore, P‐LPS treatment inhibited osteoblast differentiation in preosteoblasts as demonstrated by reductions in alkaline phosphatase activity, osteoblast gene expression, and mineralization, all of which were rescued by suppression of Notch1 signaling. Moreover, inhibition of GSK‐3β, HES1, or HEY1 partially reversed the P‐LPS‐induced inhibition of osteoblast differentiation. Together, these findings suggest that P‐LPS inhibits osteoblast differentiation by promoting the expression of Notch target genes and suppressing canonical Wnt/β‐catenin signaling. J. Cell. Physiol. 225: 106–114, 2010. © 2010 Wiley‐Liss, Inc.     

Phospholipase D1 as a key enzyme for decidualization in human endometrial stromal cells

Using primary cell cultures of human endometrial stromal cells (ES cells), we investigated the role of phospholipase D (PLD) in 8-Br-cAMP-induced decidualization, which involves morphological and biological differentiation processes. When treated with 0.5 mM 8-Br-cAMP for 12 days, ES cells were transformed into a decidualized morphology and produced significant amounts of prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP1). Simultaneously, the activity and expression levels of PLD1 increased. In addition, removal of 8-Br-cAMP from decidualized ES cells restored the undifferentiated state, and this was accompanied by decreases in PLD1 promoter activity and PLD1 expression. Overexpression of dominant negative (DN)-PLD1 inhibited the morphological changes induced by 0.5 mM 8-Br-cAMP, whereas PLD1 overexpression induced morphological changes in the absence of 0.5 mM 8-Br-cAMP treatment. Moreover, knockdown of PLD1 by siRNA and blockage of PLD by treatment with 0.3% 1-butanol decreased PRL/IGFBP1 mRNA expression, whereas PLD1 overexpression increased PRL/IGFBP1 mRNA expression. Treatment of ES cells with phosphatidic acid (PA) for 3 days induced PRL mRNA expression and morphological changes, which implies that PA is an end-product of PLD activation-induced decidualization. In addition, pretreatment of ES cells with mepacrine decreased PRL/IGFBP1 expression and inhibited morphological change, whereas pretreatment with propranolol caused no changes, as compared to cAMP-treated cells, which suggests that PA induces decidualization through phospholipase A2 (PLA2G1B). Taken together, these results suggest that PLD1 regulates 8-Br-cAMP-induced decidualization through PLA2G1B, and that PLD1 upregulation is essential for the decidualization of ES cells.     

miR-124 promotes proliferation and differentiation of neuronal stem cells through inactivating Notch pathway

Background

Neural stem cells (NSCs) are able to differentiate into neurons and astroglia. miRNAs have been demonstrated to be involved in NSC self-renewal, proliferation and differentiation. However, the exact role of miR-124 in the development of NSCs and its underlying mechanism remain to be explored.

Methods

Primary NSCs were isolated from embryos of Wistar rats. Immunocytochemistry was used to stain purified NSCs. miR-124, Delta-like 4 (DLL4), ki-67, Nestin, β-tubulin III, glial fibrillary acidic protein (GFAP), HES1, HEY2, and cyclin D1 (CCND1) expressions were detected by qRT-PCR and western blot. The interaction between miR-124 and DLL4 was confirmed by luciferase reporter assay. Cell proliferation was assessed by MTT assay.

Results

NSCs could self-proliferate and differentiate into neurons and astrocyte. miR-124 was up-regulated and DLL4 was down-regulated during NSC differentiation. DLL4 was identified as a target of miR-124 in NSCs. Ectopic expression of miR-124 or knockdown of DLL4 promoted the proliferation and the formation of NSCs to neurospheres. Moreover, miR-124 overexpression or DLL4 down-regulation improved β-tubulin III expression but decreased GFAP expression in NSCs. Furthermore, enforced expression of DLL4 partially reversed the effects of miR-124 on NSCs proliferation and differentiation. Elevated expression of miR-124 suppressed the expressions of HES1, HEY2, and CCND1 in NSCs, while these effects were attenuated following the enhancement of DLL4 expression.

Conclusion

miR-124 promoted proliferation and differentiation of NSCs through inactivating Notch pathway.

     

Hes1 Increases the Invasion Ability of Colorectal Cancer Cells via the STAT3-MMP14 Pathway

The Notch pathway contributes to self-renewal of tumor-initiating cell and inhibition of normal colonic epithelial cell differentiation. Deregulated expression of Notch1 and Jagged1 is observed in colorectal cancer. Hairy/enhancer of split (HES) family, the most characterized targets of Notch, involved in the development of many cancers. In this study, we explored the role of Hes1 in the tumorigenesis of colorectal cancer. Knocking down Hes1 induced CRC cell senescence and decreased the invasion ability, whereas over-expression of Hes1 increased STAT3 phosphorylation activity and up-regulated MMP14 protein level. We further explored the expression of Hes1 in human colorectal cancer and found high Hes1 mRNA expression is associated with poor prognosis in CRC patients. These findings suggest that Hes1 regulates the invasion ability through the STAT3-MMP14 pathway in CRC cells and high Hes1 expression is a predictor of poor prognosis of CRC.