搜索结果: 'NeuroCult Proliferation'

BACKGROUND Alzheimer's disease (AD) is characterized by progressive memory loss and impaired cognitive function. Early-onset familial forms of the disease (FAD) are caused by inheritance of mutant genes encoding presenilin 1 (PS1) variants. We have demonstrated that prion promoter (PrP)-driven expression of human FAD-linked PS1 variants in mice leads to impairments in environmental enrichment (EE)-induced adult hippocampal neural progenitor cell (AHNPC) proliferation and neuronal differentiation,and have provided evidence that accessory cells in the hippocampal niche expressing PS1 variants may modulate AHNPC phenotypes,in vivo. While of significant interest,these latter studies relied on transgenic mice that express human PS1 variant transgenes ubiquitously and at high levels,and the consequences of wild type or mutant PS1 expressed under physiologically relevant levels on EE-mediated AHNPC phenotypes has not yet been tested. RESULTS To assess the impact of mutant PS1 on EE-induced AHNPC phenotypes when expressed under physiological levels,we exposed adult mice that constitutively express the PSEN1 M146V mutation driven by the endogenous PSEN1 promoter (PS1 M146V knock-in" (KI) mice) to standard or EE-housed conditions. We show that in comparison to wild type PS1 mice AHNPCs in mice carrying homozygous (PS1M146V/M146V) or heterozygous (PS1M146V/+) M146V mutant alleles fail to exhibit EE-induced proliferation and commitment towards neurogenic lineages. More importantly we report that the survival of newborn progenitors are diminished in PS1 M146V KI mice exposed to EE-conditions compared to respective EE wild type controls. CONCLUSIONS Our findings reveal that expression at physiological levels achieved by a single PS1 M146V allele is sufficient to impair EE-induced AHNPC proliferation survival and neuronal differentiation in vivo. These results and our finding that microglia expressing a single PS1 M146V allele impairs the proliferation of wild type AHNPCs in vitro argue that expression of mutant PS1 in the AHNPC niche impairs AHNPCs phenotypes in a dominant non-cell autonomous manner. View Publication

Mouse embryonic stem (mES) cells have short duration of their cell cycle and are capable of proliferating in the absence of growth factors. To find out which signaling pathways contribute to the regulation of the mES cell cycle,we used pharmacological inhibitors of MAP and PI3 kinase cascades. The MAP kinase inhibitors as well as serum withdrawal did not affect mES cell cycle distribution,whereas the inhibitor of PI3K activity,LY294002,induced accumulation of cells in G(1) phase followed by apoptotic cell death. Serum withdrawal also causes apoptosis,but it does not change the content and activity of cell cycle regulators. In contrast,in mES cells treated with LY294002,the activities of Cdk2 and E2F were significantly decreased. Interestingly,LY294002had a much stronger effect on cell cycle distribution in low serum conditions,implying that serum can promote G(1)--textgreaterS transition of mES cells by a LY294002-resistant mechanism. Thus,proliferation of mES cells is maintained by at least two separate mechanisms: a LY294002-sensitive pathway,which is active even in the absence of serum,and LY294002-resistant,but serum-dependent,pathway. View Publication

OBJECTIVES Histone deacetylase (HDAC) is an important therapeutic target in cancer. Two of the main anticancer mechanisms of HDAC inhibitors are induction of terminal differentiation and inhibition of cell proliferation. To investigate the role of HDAC in maintenance of self-renewal and cell proliferation,we treated mesenchymal stem cells (MSCs) that originated from adipose tissue or umbilical cord blood with valproic acid (VPA) and sodium butyrate (NaBu). MATERIALS AND METHODS Human MSCs were isolated from mammary fat tissue and cord blood. We performed MTT assay and flow cytometry-based cell cycle analysis to assess self-renewal of MSCs. In vitro differentiation assays into osteogenic,adipogenic,neurogenic and chondrogenic lineages were conducted to investigate MSC multipotency. Immunocytochemistry,Western blot and reverse transcription-polymerase chain reaction were used to interrogate molecular pathways. RESULTS VPA and NaBu flattened the morphology of MSCs and inhibited their growth. VPA and NaBu activated the transcription of p21(CIP1/WAF1) by increasing the acetylation of histone H3 and H4 and eventually blocked the cell cycle at G2/M phase. The expression level of p16(INK4A),a cdk inhibitor that is closely related to cellular senescence,was not changed by HDAC inhibitor treatment. We performed controlled differentiation into bone,fat,cartilage and nervous tissue to elucidate the role of HDAC in the pluripotency of MSC to differentiate into functional tissues. VPA and NaBu decreased the efficiency of adipogenic,chondrogenic,and neurogenic differentiation as visualized by specific staining and reverse transcription-polymerase chain reaction. In contrast,osteogenic differentiation was elevated by HDAC inhibitor treatment. CONCLUSION HDAC activity is essential for maintaining the self-renewal and pluripotency of MSCs. View Publication

Ab-mediated lymphoablation is commonly used in solid organ and hematopoietic cell transplantation. However,these strategies fail to control pathogenic memory T cells efficiently and to improve long-term transplant outcomes significantly. Understanding the mechanisms of T cell reconstitution is critical for enhancing the efficacy of Ab-mediated depletion in sensitized recipients. Using a murine analog of anti-thymocyte globulin (mATG) in a mouse model of cardiac transplantation,we previously showed that peritransplant lymphocyte depletion induces rapid memory T cell proliferation and only modestly prolongs allograft survival. We now report that T cell repertoire following depletion is dominated by memory CD4 T cells. Additional depletion of these residual CD4 T cells severely impairs the recovery of memory CD8 T cells after mATG treatment. The CD4 T cell help during CD8 T cell recovery depends on the presence of B cells expressing CD40 and intact CD40/CD154 interactions. The requirement for CD4 T cell help is not limited to the use of mATG in heart allograft recipients,and it is observed in nontransplanted mice and after CD8 T cell depletion with mAb instead of mATG. Most importantly,limiting helper signals increases the efficacy of mATG in controlling memory T cell expansion and significantly extends heart allograft survival in sensitized recipients. Our findings uncover the novel role for helper memory CD4 T cells during homeostatic CD8 T cell proliferation and open new avenues for optimizing lymphoablative therapies in allosensitized patients. View Publication

Inducing cardiomyocyte proliferation in post-mitotic adult heart tissue is attracting significant attention as a therapeutic strategy to regenerate the heart after injury. Model animal screens have identified several candidate signalling pathways,however,it remains unclear as to what extent these pathways can be exploited,either individually or in combination,in the human system. The advent of human cardiac cells from directed differentiation of human pluripotent stem cells (hPSCs) now provides the ability to interrogate human cardiac biology in vitro,but it remains difficult with existing culture formats to simply and rapidly elucidate signalling pathway penetrance and interplay. To facilitate high-throughput combinatorial screening of candidate biologicals or factors driving relevant molecular pathways,we developed a high-density microbioreactor array (HDMA) - a microfluidic cell culture array containing 8100 culture chambers. We used HDMAs to combinatorially screen Wnt,Hedgehog,IGF and FGF pathway agonists. The Wnt activator CHIR99021 was identified as the most potent molecular inducer of human cardiomyocyte proliferation,inducing cell cycle activity marked by Ki67,and an increase in cardiomyocyte numbers compared to controls. The combination of human cardiomyocytes with the HDMA provides a versatile and rapid tool for stratifying combinations of factors for heart regeneration. View Publication

AIMS: Mesenchymal stem cells (MSCs) are widely used for cell therapy,particularly for the treatment of ischaemic heart disease. Mechanisms underlying control of their metabolism and proliferation capacity,critical elements for their survival and differentiation,have not been fully characterized. AMP-activated protein kinase (AMPK) is a key regulator known to metabolically protect cardiomyocytes against ischaemic injuries and,more generally,to inhibit cell proliferation. We hypothesized that AMPK plays a role in control of MSC metabolism and proliferation. METHODS AND RESULTS: MSCs isolated from murine bone marrow exclusively expressed the AMPKα1 catalytic subunit. In contrast to cardiomyocytes,a chronic exposure of MSCs to hypoxia failed to induce cell death despite the absence of AMPK activation. This hypoxic tolerance was the consequence of a preference of MSC towards glycolytic metabolism independently of oxygen availability and AMPK signalling. On the other hand,A-769662,a well-characterized AMPK activator,was able to induce a robust and sustained AMPK activation. We showed that A-769662-induced AMPK activation inhibited MSC proliferation. Proliferation was not arrested in MSCs derived from AMPKα1-knockout mice,providing genetic evidence that AMPK is essential for this process. Among AMPK downstream targets proposed to regulate cell proliferation,we showed that neither the p70 ribosomal S6 protein kinase/eukaryotic elongation factor 2-dependent protein synthesis pathway nor p21 was involved,whereas p27 expression was increased by A-769662. Silencing p27 expression partially prevented the A-769662-dependent inhibition of MSC proliferation. CONCLUSION: MSCs resist hypoxia independently of AMPK whereas chronic AMPK activation inhibits MSC proliferation,p27 being involved in this regulation. View Publication

The placenta and umbilical cord are pre-eminent candidate sources of mesenchymal stem cells (MSCs). However,placenta-derived MSCs (P-MSCs) showed greater proliferation capacity than umbilical cord-derived MSCs (UC-MSCs) in our study. We investigated the drivers of this proliferation difference and elucidated the mechanisms of proliferation regulation. Proteomic profiling and Gene Ontology (GO) functional enrichment were conducted to identify candidate proteins that may influence proliferation. Using lentiviral or small interfering RNA infection,we established overexpression and knockdown models and observed changes in cell proliferation to examine whether a relationship exists between the candidate proteins and proliferation capacity. Real-time quantitative polymerase chain reaction,western blot analysis,and immunofluorescence assays were conducted to elucidate the mechanisms underlying proliferation. Six candidate proteins were selected based on the results of proteomic profiling and GO functional enrichment. Through further validation,yes-associated protein 1 (YAP1) and $\beta$-catenin were confirmed to affect MSCs proliferation rates. YAP1 and $\beta$-catenin showed increased nuclear colocalization during cell expansion. YAP1 overexpression significantly enhanced proliferation capacity and upregulated the expression of both $\beta$-catenin and the transcriptional targets of Wnt signaling,CCND1,and c-MYC,whereas silencing $\beta$-catenin attenuated this influence. We found that YAP1 directly interacts with $\beta$-catenin in the nucleus to form a transcriptional YAP/$\beta$-catenin/TCF4 complex. Our study revealed that YAP1 and $\beta$-catenin caused the different proliferation capacities of P-MSCs and UC-MSCs. Mechanism analysis showed that YAP1 stabilized the nuclear $\beta$-catenin protein,and also triggered the Wnt/$\beta$-catenin pathway,promoting proliferation. View Publication

Cystic fibrosis (CF) cells display a more cancer-like phenotype vs. non-CF cells. KLF4 overexpression has been described in CF and this transcriptional factor acts as a negative regulator of wt-CFTR. KLF4 is described as exerting its effects in a cell-context-dependent fashion,but it is generally considered a major regulator of proliferation,differentiation,and wound healing,all the processes that are also altered in CF. Therefore,it is relevant to characterize the differential role of KLF4 in these processes in CF vs. non-CF cells. To this end,we used wt- and F508del-CFTR CFBE cells and their respective KLF4 knockout (KO) counterparts to evaluate processes like cell proliferation,polarization,and wound healing,as well as to compare the expression of several epithelial differentiation markers. Our data indicate no major impact of KLF4 KO in proliferation and a differential impact of KLF4 KO in transepithelial electrical resistance (TEER) acquisition and wound healing in wt- vs. F508del-CFTR cells. In parallel,we also observed a differential impact on the levels of some differentiation markers and epithelial-mesencymal transition (EMT)-associated transcription factors. In conclusion,KLF4 impacts TEER acquisition,wound healing,and the expression of differentiation markers in a way that is partially dependent on the CFTR-status of the cell. View Publication

BACKGROUND AND OBJECTIVES: Interactions between acute myelogenous leukemia (AML) blasts and non-leukemic cells in the bone marrow seem to be important for both disease development and susceptibility to chemotherapy. Recent studies have focused on the endothelial cells,but other non-leukemic cells may also be involved. In the present study we investigated how osteoblasts affect native human AML blasts. DESIGN AND METHODS: AML cells were derived from a large group of consecutive patients. The AML blasts and osteoblastic sarcoma cell lines (Cal72,SJSA-1) were incubated together in different chambers separated by a semipermeable membrane. We investigated effects of co-culture on proliferation,apoptosis and cytokine release. RESULTS: The cross-talk between these two cell populations,achieved via release of soluble mediators,resulted in increased AML blast proliferation,including increased proliferation of clonogenic progenitors,but did not affect spontaneous in vitro apoptosis. Both interleukin (IL) 1-b and granulocyte-macrophage colony-stimulating factor were involved in this growth-enhancing cross-talk,and normal osteoblasts could also increase the AML blast proliferation. Furthermore,co-culture of AML blasts with osteoblastic sarcoma cells as well as normal osteoblasts increased the levels of the pro-angiogenic mediator IL8. INTERPRETATION AND CONCLUSIONS: Our in vitro results suggest that the release of soluble mediators by osteoblasts supports leukemic hematopoiesis through two major mechanisms: (i) direct enhancement of AML blast proliferation; and (ii) enhanced angiogenesis caused by increased IL8 levels. View Publication

PURPOSE Nonexudative (dry) age-related macular degeneration (AMD),a leading cause of blindness in the elderly,is associated with the loss of retinal pigmented epithelium (RPE) cells and the development of geographic atrophy,which are areas devoid of RPE cells and photoreceptors. One possible treatment option would be to stimulate RPE attachment and proliferation to replace dying/dysfunctional RPE and bring about wound repair. Clinical trials are underway testing injections of RPE cells derived from pluripotent stem cells to determine their safety and efficacy in treating AMD. However,the factors regulating RPE responses to AMD-associated lesions are not well understood. Here,we use cell culture to investigate the role of RhoA coiled coil kinases (ROCKs) in human embryonic stem cell-derived RPE (hESC-RPE) attachment,proliferation,and wound closure. METHODS H9 hESC were spontaneously differentiated into RPE cells. hESC-RPE cells were treated with a pan ROCK1/2 or a ROCK2 only inhibitor; attachment,and proliferation and cell size within an in vitro scratch assay were examined. RESULTS Pharmacological inhibition of ROCKs promoted hESC-RPE attachment and proliferation,and increased the rate of closure of in vitro wounds. ROCK inhibition decreased phosphorylation of cofilin and myosin light chain,suggesting that regulation of the cytoskeleton underlies the mechanism of action of ROCK inhibition. CONCLUSIONS ROCK inhibition promotes attachment,proliferation,and wound closure in H9 hESC-RPE cells. ROCK isoforms may have different roles in wound healing. TRANSLATIONAL RELEVANCE Modulation of the ROCK-cytoskeletal axis has potential in stimulating wound repair in transplanted RPE cells and attachment in cellular therapies. View Publication

BACKGROUND Mortality rates for leukemia are high despite considerable improvements in treatment. Since polyphenols exert pro-apoptotic effects in solid tumors,our study investigated the effects of polyphenols in haematological malignancies. The effect of eight polyphenols (quercetin,chrysin,apigenin,emodin,aloe-emodin,rhein,cis-stilbene and trans-stilbene) were studied on cell proliferation,cell cycle and apoptosis in four lymphoid and four myeloid leukemic cells lines,together with normal haematopoietic control cells. METHODS Cellular proliferation was measured by CellTiter-Glo(®) luminescent assay; and cell cycle arrest was assessed using flow cytometry of propidium iodide stained cells. Apoptosis was investigated by caspase-3 activity assay using flow cytometry and apoptotic morphology was confirmed by Hoescht 33342 staining. RESULTS Emodin,quercetin,and cis-stilbene were the most effective polyphenols at decreasing cell viability (IC50 values of 5-22 μM,8-33 μM,and 25-85 μM respectively) and inducing apoptosis (AP50 values (the concentration which 50% of cells undergo apoptosis) of 2-27 μM,19-50 μM,and 8-50 μM respectively). Generally,lymphoid cell lines were more sensitive to polyphenol treatment compared to myeloid cell lines,however the most resistant myeloid (KG-1a and K562) cell lines were still found to respond to emodin and quercetin treatment at low micromolar levels. Non-tumor cells were less sensitive to all polyphenols compared to the leukemia cells. CONCLUSIONS These findings suggest that polyphenols have anti-tumor activity against leukemia cells with differential effects. Importantly,the differential sensitivity of emodin,quercetin,and cis-stilbene between leukemia and normal cells suggests that polyphenols are potential therapeutic agents for leukemia. View Publication

Insulin resistance is central to diabetes and metabolic syndrome. To define the consequences of genetic insulin resistance distinct from those secondary to cellular differentiation or in vivo regulation,we generated induced pluripotent stem cells (iPSCs) from individuals with insulin receptor mutations and age-appropriate control subjects and studied insulin signaling and gene expression compared with the fibroblasts from which they were derived. iPSCs from patients with genetic insulin resistance exhibited altered insulin signaling,paralleling that seen in the original fibroblasts. Insulin-stimulated expression of immediate early genes and proliferation were also potently reduced in insulin resistant iPSCs. Global gene expression analysis revealed marked differences in both insulin-resistant iPSCs and corresponding fibroblasts compared with control iPSCs and fibroblasts. Patterns of gene expression in patients with genetic insulin resistance were particularly distinct in the two cell types,indicating dependence on not only receptor activity but also the cellular context of the mutant insulin receptor. Thus,iPSCs provide a novel approach to define effects of genetically determined insulin resistance. This study demonstrates that effects of insulin resistance on gene expression are modified by cellular context and differentiation state. Moreover,altered insulin receptor signaling and insulin resistance can modify proliferation and function of pluripotent stem cell populations. View Publication