参考文献

Precise,robust and scalable directed differentiation of pluripotent stem cells is an important goal with respect to disease modeling or future therapies. Using the AggreWell™400 system we have standardized the differentiation of human embryonic and induced pluripotent stem cells to a neuronal fate using defined conditions. This allows reproducibility in replicate experiments and facilitates the direct comparison of cell lines. Since the starting point for EB formation is a single cell suspension,this protocol is suitable for standard and novel methods of pluripotent stem cell culture. Moreover,an intermediate population of neural precursor cells,which are routinely textgreater95% NCAM(pos) and Tra-1-60(neg) by FACS analysis,may be expanded and frozen prior to differentiation allowing a convenient starting point for downstream experiments. View Publication

The generation of induced pluripotent stem cells (iPSCs) often results in aberrant epigenetic silencing of the imprinted Dlk1-Dio3 gene cluster,compromising the ability to generate entirely iPSC-derived adult mice ('all-iPSC mice'). Here,we show that reprogramming in the presence of ascorbic acid attenuates hypermethylation of Dlk1-Dio3 by enabling a chromatin configuration that interferes with binding of the de novo DNA methyltransferase Dnmt3a. This approach allowed us to generate all-iPSC mice from mature B cells,which have until now failed to support the development of exclusively iPSC-derived postnatal animals. Our data show that transcription factor-mediated reprogramming can endow a defined,terminally differentiated cell type with a developmental potential equivalent to that of embryonic stem cells. More generally,these findings indicate that culture conditions during cellular reprogramming can strongly influence the epigenetic and biological properties of the resultant iPSCs. View Publication

Enteroendocrine cells of the gastrointestinal (GI) tract play a central role in metabolism,digestion,satiety and lipid absorption,yet their development remains poorly understood. Here we show that Arx,a homeodomain-containing transcription factor,is required for the normal development of mouse and human enteroendocrine cells. Arx expression is detected in a subset of Neurogenin3 (Ngn3)-positive endocrine progenitors and is also found in a subset of hormone-producing cells. In mice,removal of Arx from the developing endoderm results in a decrease of enteroendocrine cell types including gastrin-,glucagon/GLP-1-,CCK-,secretin-producing cell populations and an increase of somatostatin-expressing cells. This phenotype is also observed in mice with endocrine-progenitor-specific Arx ablation suggesting that Arx is required in the progenitor for enteroendocrine cell development. In addition,depletion of human ARX in developing human intestinal tissue results in a profound deficit in expression of the enteroendocrine cell markers CCK,secretin and glucagon while expression of a pan-intestinal epithelial marker,CDX2,and other non-endocrine markers remained unchanged. Taken together,our findings uncover a novel and conserved role of Arx in mammalian endocrine cell development and provide a potential cause for the chronic diarrhea seen in both humans and mice carrying Arx mutations. View Publication

Herein we present a protocol of reprogramming human adult fibroblasts into human induced pluripotent stem cells (hiPSC) using retroviral vectors encoding Oct3/4,Sox2,Klf4 and c-myc (OSKM) in the presence of sodium butyrate (1-3). We used this method to reprogram late passage (textgreaterp10) human adult fibroblasts derived from Friedreich's ataxia patient (GM03665,Coriell Repository). The reprogramming approach includes highly efficient transduction protocol using repetitive centrifugation of fibroblasts in the presence of virus-containing media. The reprogrammed hiPSC colonies were identified using live immunostaining for Tra-1-81,a surface marker of pluripotent cells,separated from non-reprogrammed fibroblasts and manually passaged (4,5). These hiPSC were then transferred to Matrigel plates and grown in feeder-free conditions,directly from the reprogramming plate. Starting from the first passage,hiPSC colonies demonstrate characteristic hES-like morphology. Using this protocol more than 70% of selected colonies can be successfully expanded and established into cell lines. The established hiPSC lines displayed characteristic pluripotency markers including surface markers TRA-1-60 and SSEA-4,as well as nuclear markers Oct3/4,Sox2 and Nanog. The protocol presented here has been established and tested using adult fibroblasts obtained from Friedreich's ataxia patients and control individuals( 6),human newborn fibroblasts,as well as human keratinocytes. View Publication

Histone deacetylase (HDAC) inhibitors (HDI) induce endoplasmic reticulum (ER) stress and apoptosis,while promoting autophagy,which promotes cancer cell survival when apoptosis is compromised. Here,we determined the in vitro and in vivo activity of the combination of the pan-HDI panobinostat and the autophagy inhibitor chloroquine against human estrogen/progesterone receptor and HER2 (triple)-negative breast cancer (TNBC) cells. Treatment of MB-231 and SUM159PT cells with panobinostat disrupted the hsp90/histone deacetylase 6/HSF1/p97 complex,resulting in the upregulation of hsp. This was accompanied by the induction of enhanced autophagic flux as evidenced by increased expression of LC3B-II and the degradation of the autophagic substrate p62. Treatment with panobinostat also induced the accumulation and colocalization of p62 with LC3B-II in cytosolic foci as evidenced by immunofluorescent confocal microscopy. Inhibition of panobinostat-induced autophagic flux by chloroquine markedly induced the accumulation of polyubiquitylated proteins and p62,caused synergistic cell death of MB-231 and SUM159PT cells,and inhibited mammosphere formation in MB-231 cells,compared with treatment with each agent alone. Finally,in mouse mammary fat pad xenografts of MB-231 cells,a tumor size-dependent induction of heat shock response,ER stress and autophagy were observed. Cotreatment with panobinostat and chloroquine resulted in reduced tumor burden and increased the survival of MB-231 breast cancer xenografts. Collectively,our findings show that cotreatment with an autophagy inhibitor and pan-HDI,for example,chloroquine and panobinostat results in accumulation of toxic polyubiquitylated proteins,exerts superior inhibitory effects on TNBC cell growth,and increases the survival of TNBC xenografts. View Publication

Embryonic stem cell (ESC) identity and self-renewal is maintained by extrinsic signaling pathways and intrinsic gene regulatory networks. Here,we show that three members of the Ccr4-Not complex,Cnot1,Cnot2,and Cnot3,play critical roles in maintaining mouse and human ESC identity as a protein complex and inhibit differentiation into the extraembryonic lineages. Enriched in the inner cell mass of blastocysts,these Cnot genes are highly expressed in ESC and downregulated during differentiation. In mouse ESCs,Cnot1,Cnot2,and Cnot3 are important for maintenance in both normal conditions and the 2i/LIF medium that supports the ground state pluripotency. Genetic analysis indicated that they do not act through known self-renewal pathways or core transcription factors. Instead,they repress the expression of early trophectoderm (TE) transcription factors such as Cdx2. Importantly,these Cnot genes are also necessary for the maintenance of human ESCs,and silencing them mainly lead to TE and primitive endoderm differentiation. Together,our results indicate that Cnot1,Cnot2,and Cnot3 represent a novel component of the core self-renewal and pluripotency circuitry conserved in mouse and human ESCs. View Publication

In vitro exposure of neural progenitor cell (NPC) populations to reduced O(2) (e.g. 3% versus 20%) can increase their proliferation,survival and neuronal differentiation. Our objective was to determine if an acute (textless1hr),in vivo exposure to intermittent hypoxia (AIH) alters expansion and/or differentiation of subsequent in vitro cultures of NPC from the subventricular zone (SVZ). Neonatal C57BL/6 mice (postnatal day 4) were exposed to an AIH paradigm (20×1 minute; alternating 21% and 10% O(2)). Immediately after AIH,SVZ tissue was isolated and NPC populations were cultured and assayed either as neurospheres (NS) or as adherent monolayer cells (MASC). AIH markedly increased the capacity for expansion of cultured NS and MASC,and this was accompanied by increases in a proliferation maker (Ki67),MTT activity and hypoxia-inducible factor-1α (HIF-1α) signaling in NS cultures. Peptide blockade experiments confirmed that proteins downstream of HIF-1α are important for both proliferation and morphological changes associated with terminal differentiation in NS cultures. Finally,immunocytochemistry and Western blotting experiments demonstrated that AIH increased expression of the neuronal fate determination transcription factor Pax6 in SVZ tissue,and this was associated with increased neuronal differentiation in cultured NS and MASC. We conclude that in vivo AIH exposure can enhance the viability of subsequent in vitro SVZ-derived NPC cultures. AIH protocols may therefore provide a means to prime" NPC prior to transplantation into the injured central nervous system." View Publication

R848,also known as resiquimod,acts as a ligand for toll-like receptor 7 (TLR7) and activates immune cells. In this study,we examined the effects of R848 on differentiation,survival,and bone-resorbing function of osteoclasts. R848 inhibited osteoclast differentiation of mouse bone marrow-derived macrophages (BMMs) and human peripheral blood-derived monocytes induced by receptor activator of NF-κB ligand in a dose-dependent manner. In addition,it inhibited mouse osteoclast differentiation induced in cocultures of bone marrow cells and osteoblasts in the presence of dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]. However,R848 did not affect the survival or bone-resorbing activity of mouse mature osteoclasts. R848 also upregulated the mRNA expression levels of interleukin (IL)-6,IL-12,interferon (IFN)-γ,and inducible nitric oxide synthase in mouse BMMs expressing TLR7. IFN-β was consistently expressed in the BMMs and addition of neutralizing antibodies against IFN-β to the cultures partially recovered osteoclast differentiation inhibited by R848. These results suggest that R848 targets osteoclast precursors and inhibits their differentiation into osteoclasts via TLR7. View Publication

The detection of growth hormone (GH) and its receptor in germinal regions of the mammalian brain prompted our investigation of GH and its role in the regulation of endogenous neural precursor cell activity. Here we report that the addition of exogenous GH significantly increased the expansion rate in long-term neurosphere cultures derived from wild-type mice,while neurospheres derived from GH null mice exhibited a reduced expansion rate. We also detected a doubling in the frequency of large (i.e. stem cell-derived) colonies for up to 120 days following a 7-day intracerebroventricular infusion of GH suggesting the activation of endogenous stem cells. Moreover,gamma irradiation induced the ablation of normally quiescent stem cells in GH-infused mice,resulting in a decline in olfactory bulb neurogenesis. These results suggest that GH activates populations of resident stem and progenitor cells,and therefore may represent a novel therapeutic target for age-related neurodegeneration and associated cognitive decline. View Publication

The anti-diabetic drug metformin is rapidly emerging as a potential anti-cancer agent. Metformin,effective in treating type 2 diabetes and the insulin resistance syndromes,improves insulin resistance by reducing hepatic gluconeogenesis and by enhancing glucose uptake by skeletal muscle. Epidemiological studies have consistently associated metformin use with decreased cancer incidence and cancer-related mortality. Furthermore,numerous preclinical and clinical studies have demonstrated anti-cancer effects of metformin,leading to an explosion of interest in evaluating this agent in human cancer. The effects of metformin on circulating insulin levels indicate a potential efficacy towards cancers associated with hyperinsulinaemia; however,metformin may also directly inhibit tumour growth. In this review,we describe the mechanism of action of metformin and summarise the epidemiological,clinical and preclinical evidence supporting a role for metformin in the treatment of cancer. In addition,the challenges associated with translating preclinical results into therapeutic benefit in the clinical setting will be discussed. View Publication