技术资料

Many forms of blindness result from the dysfunction or loss of retinal photoreceptors. Induced pluripotent stem cells (iPSCs) hold great potential for the modelling of these diseases or as potential therapeutic agents. However,to fulfill this promise,a remaining challenge is to induce human iPSC to recreate in vitro key structural and functional features of the native retina,in particular the presence of photoreceptors with outer-segment discs and light sensitivity. Here we report that hiPSC can,in a highly autonomous manner,recapitulate spatiotemporally each of the main steps of retinal development observed in vivo and form three-dimensional retinal cups that contain all major retinal cell types arranged in their proper layers. Moreover,the photoreceptors in our hiPSC-derived retinal tissue achieve advanced maturation,showing the beginning of outer-segment disc formation and photosensitivity. This success brings us one step closer to the anticipated use of hiPSC for disease modelling and open possibilities for future therapies. View Publication

Chemical sensing on the nanoscale has been breaking new ground since the discovery of surface enhanced Raman scattering (SERS). For nanoparticles,controlled particle aggregation is necessary to achieve the largest SERS enhancements. Therefore,aggregating agents such as salts or linker molecules are used in conjunction with chemically sensitive reporters in order to develop robust environmentally sensitive SERS probes. While salt-induced colloidal nanosphere aggregates have produced robust SERS signals,their variability in aggregate size contributes significantly to poor SERS signal reproducibility,which can complicate their use in in vitro cellular studies. Such systems often also lack reproducibility in spectral measurements between different nanoparticle clusters. Preaggregation of colloids via linkers followed by surface functionalization with reporter molecules results in the linker occupying valuable SERS hotspot volume which could otherwise be utilized by additional reporter molecules. Ideally,both functionalities should be obtained from a single molecule. Here,we report the use of 3,5-dimercaptobenzoic acid,a single multifunctional molecule that creates SERS hotspots via the controlled aggregation of nanoparticles,and also reports pH values. We show that 3,5-dimercaptobenzoic acid bound to Au nanospheres results in an excellent pH nanoprobe,producing very robust,and highly reproducible SERS signals that can report pH across the entire physiological range with excellent pH resolution. To demonstrate the efficacy of our novel pH reporters,these probes were also used to image both the particle and pH distribution in the cytoplasm of human induced pluripotent stem cells (hiPSCs). View Publication

Receptor-interacting protein (RIP)3 is a critical regulator of necroptosis and has been demonstrated to be associated with various diseases,suggesting that its inhibitors are promising in the clinic. However,there have been few RIP3 inhibitors reported as yet. B-Raf(V600E) inhibitors are an important anticancer drug class for metastatic melanoma therapy. In this study,we found that 6 B-Raf inhibitors could inhibit RIP3 enzymatic activity in vitro. Among them,dabrafenib showed the most potent inhibition on RIP3,which was achieved by its ATP-competitive binding to the enzyme. Dabrafenib displayed highly selective inhibition on RIP3 over RIP1,RIP2 and RIP5. Moreover,only dabrafenib rescued cells from RIP3-mediated necroptosis induced by the necroptosis-induced combinations,that is,tumor necrosis factor (TNF)α,TNF-related apoptosis-inducing ligand or Fas ligand plus Smac mimetic and the caspase inhibitor z-VAD. Dabrafenib decreased the RIP3-mediated Ser358 phosphorylation of mixed lineage kinase domain-like protein (MLKL) and disrupted the interaction between RIP3 and MLKL. Notably,RIP3 inhibition of dabrafenib appeared to be independent of its B-Raf inhibition. Dabrafenib was further revealed to prevent acetaminophen-induced necrosis in normal human hepatocytes,which is considered to be mediated by RIP3. In acetaminophen-overdosed mouse models,dabrafenib was found to apparently ease the acetaminophen-caused liver damage. The results indicate that the anticancer B-Raf(V600E) inhibitor dabrafenib is a RIP3 inhibitor,which could serve as a sharp tool for probing the RIP3 biology and as a potential preventive or therapeutic agent for RIP3-involved necroptosis-related diseases such as acetaminophen-induced liver damage. View Publication

Nuclear factor,erythroid 2-like 2 (Nrf2) is a master transcription factor for cellular defense against endogenous and exogenous stresses by regulating expression of many antioxidant and detoxification genes. Here,we show that Nrf2 acts as a key pluripotency gene and a regulator of proteasome activity in human embryonic stem cells (hESCs). Nrf2 expression is highly enriched in hESCs and dramatically decreases upon differentiation. Nrf2 inhibition impairs both the self-renewal ability of hESCs and re-establishment of pluripotency during cellular reprogramming. Nrf2 activation can delay differentiation. During early hESC differentiation,Nrf2 closely colocalizes with OCT4 and NANOG. As an underlying mechanism,our data show that Nrf2 regulates proteasome activity in hESCs partially through proteasome maturation protein (POMP),a proteasome chaperone,which in turn controls the proliferation of self-renewing hESCs,three germ layer differentiation and cellular reprogramming. Even modest proteasome inhibition skews the balance of early differentiation toward mesendoderm at the expense of an ectodermal fate by decreasing the protein level of cyclin D1 and delaying the degradation of OCT4 and NANOG proteins. Taken together,our findings suggest a new potential link between environmental stress and stemness with Nrf2 and the proteasome coordinately positioned as key mediators. View Publication

Understanding the mechanisms that sustain pluripotency in human embryonic stem cells (hESCs) is an active area of research that may prove useful in regenerative medicine and will provide fundamental information relevant to development and cancer. hESCs and cancer cells share the unique ability to proliferate indefinitely and rapidly. Because the protein survivin is uniquely overexpressed in virtually all human cancers and in hESCs,we sought to investigate its role in supporting the distinctive capabilities of these cell types. Results presented here suggest that survivin contributes to the maintenance of pluripotency and that post-transcriptional control of survivin isoform expression is selectively regulated by microRNAs. miR-203 has been extensively studied in human tumors,but has not been characterized in hESCs. We show that miR-203 expression and activity is consistent with the expression and subcellular localization of survivin isoforms that in turn modulate expression of the Oct4 and Nanog transcription factors to sustain pluripotency. This study contributes to understanding of the complex regulatory mechanisms that govern whether hESCs proliferate or commit to lineages. textcopyright 2014 Wiley Periodicals,Inc. View Publication

Nonhomologous end-joining (NHEJ) is a key pathway for efficient repair of DNA double-strand breaks (DSBs) and V(D)J recombination. NHEJ defects in humans cause immunodeficiency and increased cellular sensitivity to ionizing irradiation (IR) and are variably associated with growth retardation,microcephaly,and neurodevelopmental delay. Repair of DNA DSBs is important for reprogramming of somatic cells into induced pluripotent stem cells (iPSCs). To compare the specific contribution of DNA ligase 4 (LIG4),Artemis,and DNA-protein kinase catalytic subunit (PKcs) in this process and to gain insights into phenotypic variability associated with these disorders,we reprogrammed patient-derived fibroblast cell lines with NHEJ defects. Deficiencies of LIG4 and of DNA-PK catalytic activity,but not Artemis deficiency,were associated with markedly reduced reprogramming efficiency,which could be partially rescued by genetic complementation. Moreover,we identified increased genomic instability in LIG4-deficient iPSCs. Cell cycle synchronization revealed a severe defect of DNA repair and a G0/G1 cell cycle arrest,particularly in LIG4- and DNA-PK catalytically deficient iPSCs. Impaired myeloid differentiation was observed in LIG4-,but not Artemis- or DNA-PK-mutated iPSCs. These results indicate a critical importance of the NHEJ pathway for somatic cell reprogramming,with a major role for LIG4 and DNA-PKcs and a minor,if any,for Artemis. View Publication

Background: Human induced pluripotent stem cells,which can be differentiated into hepatocyte-like cells,could provide a source for liver regeneration and bio-artificial liver devices. However,the functionality of hepatocyte-like cells is significantly lower than that of primary hepatocytes. Aims: To investigate whether serum from patients undergoing hepatectomy might promote differentiation from human induced pluripotent stem cells to hepatocyte-like cells. Methods: Serum from patients undergoing hepatectomy (acquired pre-hepatectomy and 3. hours,1 day and 3 days post-hepatectomy) was used to replace foetal bovine serum when differentiating human induced pluripotent stem cells into hepatocyte-like cells. Properties of hepatocyte-like cells were assessed and compared with cells cultured in foetal bovine serum. Results: The differentiation efficiency and functionality of hepatocyte-like cells cultured in human serum 3. hours and 1 day post-hepatectomy were superior to those cultured in foetal bovine serum and human serum pre-hepatectomy. Human serum 3 days post-hepatectomy had an equal effect to that of human serum pre-hepatectomy. Some cytochrome P450 isozyme transcript levels of hepatocyte-like cells cultured in human serum were higher than those cultured in foetal bovine serum. Conclusion: Human serum,particularly that acquired relatively soon after hepatectomy,can enhance the differentiation efficiency and functionality of hepatocyte-like cells derived from human induced pluripotent stem cells. textcopyright 2014 Editrice Gastroenterologica Italiana S.r.l. View Publication

The pluripotent property of hESCs makes them attractive for treatment of degenerative diseases such as diabetes. We have developed a stage-wise directed differentiation protocol to produce alginate-encapsulated islet-like cells derived from hESCs,which can be directly implanted for diabetes therapy. The advantage of alginate encapsulation lies in its capability to immunoisolate,along with the added possibility of scalable culture. We have evaluated the possibility of encapsulating hESCs at different stages of differentiation. Encapsulation of predifferentiated cells resulted in insufficient cellular yield and differentiation. On the other hand,encapsulation of undifferentiated hESCs followed by differentiation induction upon encapsulation,resulted in the highest viability and differentiation. More striking was that alginate encapsulation resulted in a much stronger differentiation compared to parallel 2D cultures,resulting in 20-fold increase in c-peptide protein synthesis. To elucidate the mechanism contributing to encapsulation-mediated enhancement in hESC maturation,investigation of the signaling pathways revealed interesting insight. While the phospho-protein levels of all the tested signaling molecules were lower under encapsulation,the ratio of pSMAD/pAKT was significantly higher,indicating a more efficient signal transduction under encapsulation. These results clearly demonstrate that alginate encapsulation of hESCs and differentiation to islet-cells types provides a potentially translatable treatment option for type1 diabetes. View Publication

BACKGROUND: Airway remodeling might explain lung function decline among asthmatic children. Extracellular matrix (ECM) deposition by human lung fibroblasts (HLFs) is implicated in airway remodeling. Airway epithelial cell (AEC) signaling might regulate HLF ECM expression. OBJECTIVES: We sought to determine whether AECs from asthmatic children differentially regulate HLF expression of ECM constituents. METHODS: Primary AECs were obtained from well-characterized atopic asthmatic (n = 10) and healthy (n = 10) children intubated during anesthesia for an elective surgical procedure. AECs were differentiated at an air-liquid interface for 3 weeks and then cocultured with HLFs from a healthy child for 96 hours. Collagen I (COL1A1),collagen III (COL3A1),hyaluronan synthase (HAS) 2,and fibronectin expression by HLFs and prostaglandin E2 synthase (PGE2S) expression by AECs were assessed by using RT-PCR. TGF-$$1 and TGF-$$2 concentrations in media were measured by using ELISA. RESULTS: COL1A1 and COL3A1 expression by HLFs cocultured with AECs from asthmatic patients was greater than that by HLFs cocultured with AECs from healthy subjects (2.2-fold,P textless .02; 10.8-fold,P textless .02). HAS2 expression by HLFs cocultured with AECs from asthmatic patients was 2.5-fold higher than that by HLFs cocultured with AECs from healthy subjects (P textless .002). Fibronectin expression by HLFs cocultured with AECs from asthmatic patients was significantly greater than that by HLFs alone. TGF-$$2 activity was increased in cocultures of HLFs with AECs from asthmatic patients (P textless .05),whereas PGES2 was downregulated in AEC-HLF cocultures (2.2-fold,P textless .006). CONCLUSIONS: HLFs cocultured with AECs from asthmatic patients showed differential expression of the ECM constituents COL1A1 and COL3A1 and HAS2 compared with HLFs cocultured with AECs from healthy subjects. These findings support a role for altered ECM production in asthmatic airway remodeling,possibly regulated by unbalanced AEC signaling. View Publication

Human endothelial cells (ECs) and pericytes are of great interest for research on vascular development and disease,as well as for future therapy. This protocol describes the efficient generation of ECs and pericytes from human pluripotent stem cells (hPSCs) under defined conditions. Essential steps for hPSC culture,differentiation,isolation and functional characterization of ECs and pericytes are described. Substantial numbers of both cell types can be derived in only 2-3 weeks: this involves differentiation (10 d),isolation (1 d) and 4 or 10 d of expansion of ECs and pericytes,respectively. We also describe two assays for functional evaluation of hPSC-derived ECs: (i) primary vascular plexus formation upon coculture with hPSC-derived pericytes and (ii) incorporation in the vasculature of zebrafish xenografts in vivo. These assays can be used to test the quality and drug sensitivity of hPSC-derived ECs and model vascular diseases with patient-derived hPSCs. View Publication

Recent methodological advances have improved the ease and efficiency of generating human induced pluripotent stem cells (hiPSCs),but this now typically results in a greater number of hiPSC clones being derived than can be wholly characterized. It is therefore imperative that methods are developed which facilitate rapid selection of hiPSC clones most suited for the downstream research aims. Here we describe a combination of procedures enabling the simultaneous screening of multiple clones to determine their genomic integrity as well as their cardiac differentiation potential within two weeks of the putative reprogrammed colonies initially appearing. By coupling splinkerette-PCR with Ion Torrent sequencing,we could ascertain the number and map the proviral integration sites in lentiviral-reprogrammed hiPSCs. In parallel,we developed an effective cardiac differentiation protocol that generated functional cardiomyocytes within 10 days without requiring line-specific optimization for any of the six independent human pluripotent stem cell lines tested. Finally,to demonstrate the scalable potential of these procedures,we picked 20 nascent iPSC clones and performed these independent assays concurrently. Before the clones required passaging,we were able to identify clones with a single integrated copy of the reprogramming vector and robust cardiac differentiation potential for further analysis. View Publication

Human induced pluripotent stem (hiPS) cell lines with tissue-specific or ubiquitous reporter genes are extremely useful for optimizing in vitro differentiation conditions as well as for monitoring transplanted cells in vivo. The adeno-associated virus integration site 1 (AAVS1) locus has been used as a safe harbor" locus for inserting transgenes because of its open chromatin structure� View Publication