技术资料

Neural precursor (NP) cells derived from human induced pluripotent stem cells (hiPSCs),and their neuronal progeny,will play an important role in disease modeling,drug screening tests,central nervous system development studies,and may even become valuable for regenerative medicine treatments. Nonetheless,it is challenging to obtain homogeneous and synchronously differentiated NP populations from hiPSCs,and after neural commitment many pluripotent stem cells remain in the differentiated cultures. Here,we describe an efficient and simple protocol to differentiate hiPSC-derived NPs in 12 days,and we include a final purification stage where Tra-1-60+ pluripotent stem cells (PSCs) are removed using magnetic activated cell sorting (MACS),leaving the NP population nearly free of PSCs. View Publication

Emerging hepatic models for the study of drug-induced toxicity include pluripotent stem cell-derived hepatocyte-like cells (HLCs) and complex hepatocyte-non-parenchymal cellular coculture to mimic the complex multicellular interactions that recapitulate the niche environment in the human liver. However,a specific marker of hepatocyte perturbation,required to discriminate hepatocyte damage from non-specific cellular toxicity contributed by non-hepatocyte cell types or immature differentiated cells is currently lacking,as the cytotoxicity assays routinely used in in vitro toxicology research depend on intracellular molecules which are ubiquitously present in all eukaryotic cell types. In this study,we demonstrate that microRNA-122 (miR-122) detection in cell culture media can be used as a hepatocyte-enriched in vitro marker of drug-induced toxicity in homogeneous cultures of hepatic cells,and a cell-specific marker of toxicity of hepatic cells in heterogeneous cultures such as HLCs generated from various differentiation protocols and pluripotent stem cell lines,where conventional cytotoxicity assays using generic cellular markers may not be appropriate. We show that the sensitivity of the miR-122 cytotoxicity assay is similar to conventional assays that measure lactate dehydrogenase activity and intracellular adenosine triphosphate when applied in hepatic models with high levels of intracellular miR-122,and can be multiplexed with other assays. MiR-122 as a biomarker also has the potential to bridge results in in vitro experiments to in vivo animal models and human samples using the same assay,and to link findings from clinical studies in determining the relevance of in vitro models being developed for the study of drug-induced liver injury. View Publication

Alcohol consumption has long been associated with a majority of liver diseases and has been found to influence both fetal and adult liver functions. In spite of being one of the major causes of morbidity and mortality in the world,currently,there are no effective strategies that can prevent or treat alcoholic liver disease (ALD),due to a lack of human-relevant research models. Recent success in generation of functionally active mature hepatocyte-like cells from human-induced pluripotent cells (iPSCs) enables us to better understand the effects of alcohol on liver functions. Here,we describe the method and effect of alcohol exposure on multistage hepatic cell types derived from human iPSCs,in an attempt to recapitulate the early stages of liver tissue injury associated with ALD. We exposed different stages of iPSC-induced hepatic cells to ethanol at a pathophysiological concentration. In addition to stage-specific molecular markers,we measured several key cellular parameters of hepatocyte injury,including apoptosis,proliferation,and lipid accumulation. View Publication

Embryonic stem cells are self-renewing pluripotent cells with competency to differentiate into all three-germ lineages. Many studies have demonstrated the importance of genetic and epigenetic molecular mechanisms in the maintenance of self-renewal and pluripotency. Stem cells are under unique molecular and cellular regulations different from somatic cells. Proper regulation should be ensured to maintain their unique self-renewal and undifferentiated characteristics. Understanding key mechanisms in stem cell biology will be important for the successful application of stem cells for regenerative therapeutic medicine. More importantly practical use of stem cells will require our knowledge on how to properly direct and differentiate stem cells into the necessary type of cells. Embryonic stem cells and adult stem cells have been used as study models to unveil molecular and cellular mechanisms in various signaling pathways. They are especially beneficial to developmental studies where in vivo molecular/cellular study models are not available. We have derived neural stem cells from human embryonic stem cells as a model to study the effect of teratogen in neural development. We have tested commercial neural differentiation system and successfully derived neural precursor cells exhibiting key molecular features of neural stem cells,which will be useful for experimental application. View Publication

Pluripotent human embryonic stem cells (hESCs) can be efficiently directed to become immature neuroepithelial precursor cells (NPCs) and functional mature neural cells,including neurotransmitter-secreting neurons and glial cells. Investigating the susceptibility of these hESCs-derived neural cells to neurotrophic viruses,such as Japanese encephalitis virus (JEV),provides insight into the viral cell tropism in the infected human brain. We demonstrate that hESC-derived NPCs are highly vulnerable to JEV infection at a low multiplicity of infection (MOI). In addition,glial fibrillary acid protein (GFAP)-expressing glial cells are also susceptible to JEV infection. In contrast,only a few mature neurons were infected at MOI 10 or higher on the third day post-infection. In addition,functional neurotransmitter-secreting neurons are also resistant to JEV infection at high MOI. Moreover,we discover that vimentin intermediate filament,reported as a putative neurovirulent JEV receptor,is highly expressed in NPCs and glial cells,but not mature neurons. These results indicate that the expression of vimentin in neural cells correlates to the cell tropism of JEV. Finally,we further demonstrate that membranous vimentin is necessary for the susceptibility of hESC-derived NPCs to JEV infection. View Publication

The generation of beta-thalassemia (β-Thal) patient-specific induced pluripotent stem cells (iPSCs),subsequent homologous recombination-based gene correction of disease-causing mutations/deletions in the β-globin gene (HBB),and their derived hematopoietic stem cell (HSC) transplantation offers an ideal therapeutic solution for treating this disease. However,the hematopoietic differentiation efficiency of gene-corrected β-Thal iPSCs has not been well evaluated in the previous studies. In this study,we used the latest gene-editing tool,clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9),to correct β-Thal iPSCs; gene-corrected cells exhibit normal karyotypes and full pluripotency as human embryonic stem cells (hESCs) showed no off-targeting effects. Then,we evaluated the differentiation efficiency of the gene-corrected β-Thal iPSCs. We found that during hematopoietic differentiation,gene-corrected β-Thal iPSCs showed an increased embryoid body ratio and various hematopoietic progenitor cell percentages. More importantly,the gene-corrected β-Thal iPSC lines restored HBB expression and reduced reactive oxygen species production compared with the uncorrected group. Our study suggested that hematopoietic differentiation efficiency of β-Thal iPSCs was greatly improved once corrected by the CRISPR/Cas9 system,and the information gained from our study would greatly promote the clinical application of β-Thal iPSC-derived HSCs in transplantation. View Publication

Rho-kinase (ROCK) has been well documented to play a key role in RhoA-induced actin remodeling. ROCK activation results in myosin light chain (MLC) phosphorylation either by direct action on MLC kinase (MLCK) or by inhibition of MLC phosphatase (MLCP),modulating actin-myosin contraction. We found that inhibition of the ROCK pathway in induced pluripotent stem cells,leads to nuclear export of HDAC7 and transcriptional activation of the orphan nuclear receptor NR4A1 while in cells with constitutive ROCK hyperactivity due to loss of function of the RhoGTPase activating protein Oligophrenin-1 (OPHN1),the orphan nuclear receptor NR4A1 is downregulated. Our study identify a new target of ROCK signaling via myosin phosphatase subunit (MYPT1) and Histone Deacetylase (HDAC7) at the nuclear level and provide new insights in the cellular functions of ROCK. View Publication

The Mesenchymal-to-Epithelial Transition (MET) has been recognized as a crucial step for successful reprogramming of fibroblasts to induced pluripotent stem cells (iPSCs). Thus,it has been demonstrated,that the efficiency of reprogramming can be enhanced by promoting an epithelial expression program in cells,with a concomitant repression of key mesenchymal genes. However,a detailed characterization of the epithelial transition associated with the acquisition of a pluripotent phenotype is still lacking to this date. Here,we integrate a panel of morphological approaches with gene expression analyses to visualize the dynamics of episomal reprogramming of human fibroblasts to iPSCs. We provide the first ultrastructural analysis of human fibroblasts at various stages of episomal iPSC reprogramming,as well as the first real-time live cell visualization of a MET occurring during reprogramming. The results indicate that the MET manifests itself approximately 6-12. days after electroporation,in synchrony with the upregulation of early pluripotency markers,and resembles a reversal of the Epithelial-to-Mesenchymal Transition (EMT) which takes place during mammalian gastrulation. View Publication

In this study,we have identified a novel member of the AMPK family,namely Sucrose non-fermenting related kinase (Snrk),that is responsible for maintaining cardiac metabolism in mammals. SNRK is expressed in the heart,and brain,and in cell types such as endothelial cells,smooth muscle cells and cardiomyocytes (CMs). Snrk knockout (KO) mice display enlarged hearts,and die at postnatal day 0. Microarray analysis of embryonic day 17.5 Snrk hearts,and blood profile of neonates display defect in lipid metabolic pathways. SNRK knockdown CMs showed altered phospho-acetyl-coA carboxylase and phospho-AMPK levels similar to global and endothelial conditional KO mouse. Finally,adult cardiac conditional KO mouse displays severe cardiac functional defects and lethality. Our results suggest that Snrk is essential for maintaining cardiac metabolic homeostasis,and shows an autonomous role for SNRK during mammalian development. View Publication

BACKGROUND Human (h) embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) serve as a potential unlimited ex vivo source of cardiomyocytes (CMs). However,a well-accepted roadblock has been their immature phenotype. hESC/iPSC-derived ventricular (v) CMs and their engineered cardiac microtissues (hvCMTs) similarly displayed positive chronotropic but null inotropic responses to $\$-adrenergic stimulation. Given that phospholamban (PLB) is robustly present in adult but poorly expressed in hESC/iPSC-vCMs and its defined biological role in $\$-adrenergic signaling,we investigated the functional consequences of PLB expression in hESC/iPSC-vCMs and hvCMTs. METHODS AND RESULTS First,we confirmed that PLB protein was differentially expressed in hESC (HES2,H9)- and iPSC-derived and adult vCMs. We then transduced hES2-vCMs with the recombinant adenoviruses (Ad) Ad-PLB or Ad-S16E-PLB to overexpress wild-type PLB or the pseudophosphorylated point-mutated variant,respectively. As anticipated from the inhibitory effect of unphosphorylated PLB on sarco/endoplasmic reticulum Ca2+-ATPase,Ad-PLB transduction significantly attenuated electrically evoked Ca2+ transient amplitude and prolonged the 50% decay time. Importantly,Ad-PLB-transduced hES2-vCMs uniquely responded to isoproterenol. Ad-S16E-PLB-transduced hES2-vCMs displayed an intermediate phenotype. The same trends were observed with H9- and iPSC-vCMs. Directionally,similar results were also seen with Ad-PLB-transduced and Ad-S16E-transduced hvCMTs. However,Ad-PLB altered neither the global transcriptome nor ICa,L,implicating a PLB-specific effect. CONCLUSIONS Engineered upregulation of PLB expression in hESC/iPSC-vCMs restores a positive inotropic response to $\$-adrenergic stimulation. These results not only provide a better mechanistic understanding of the immaturity of hESC/iPSC-vCMs but will also lead to improved disease models and transplantable prototypes with adult-like physiological responses. View Publication

Human induced pluripotent stem cells (hiPSCs) have potential applications in cell replacement therapy and regenerative medicine. However,limited information is available regarding the immunologic features of iPSCs. In this study,expression of MHC and T cell co-stimulatory molecules in hiPSCs,and the effects on activation,proliferation and cytokine production in allogeneic human peripheral blood mononuclear cells were examined. We found that no-integrate hiPSCs had no MHC-II and T cell co-stimulatory molecules expressions but had moderate level of MHC-I and HLA-G expressions. In contrast to human skin fibroblasts (HSFs) which significantly induced allogeneic T cell activation and proliferation,hiPSCs failed to induce allogeneic CD45+ lymphocyte and CD8+ T cell activation and proliferation but could induce a low level of allogeneic CD4+ T cell proliferation. Unlike HSFs which induced allogeneic lymphocytes to produce high levels of IFN-γ,TNF-α and IL-17,hiPSCs only induced allogeneic lymphocytes to produce IL-2 and IL-10,and promote IL-10-secreting regulatory T cell (Treg) generation. Our study suggests that the integration-free hiPSCs had low or negligible immunogenicity,which may result from their induction of IL-10-secreting Treg. View Publication

Rapid technological advances have made the acquisition of large numbers of spectra not only feasible,but also routine. As a result,a significant research effort is focused on semi-automated and fully automated spectral processing techniques. However,the need to provide initial estimates of the number of peaks,their band shapes,and the initial parameters of these bands presents an obstacle to the full automation of peak fitting and its incorporation into fully automated spectral-preprocessing workflows. Moreover,the sensitivity of peak-fit routines to initial parameter settings and the resultant variations in solution quality further impede user-free operation. We have developed a technique to perform fully automated peak fitting on fully automated preconditioned spectra-specifically,baseline-corrected and smoothed spectra that are free of cosmic-ray-induced spikes. Briefly,the tallest peak in a spectrum is located and a Gaussian peak-fit is performed. The fitted peak is then subtracted from the spectrum,and the procedure is repeated until the entire spectrum has been processed. In second and third passes,all the peaks in the spectrum are fitted concurrently,but are fitted to a Pearson Type VII model using the parameters for the model established in the prior pass. The technique is applied to a synthetic spectrum with several peaks,some of which have substantial overlap,to test the ability of the method to recover the correct number of peaks,their true shape,and their appropriate parameters. Finally the method is tested on measured Raman spectra collected from human embryonic stem cells and samples of red blood cells. View Publication