技术资料

Hyaluronic acid (HA) has been cross-linked to form hydrogel for potential applications in the self-renewal and differentiation of human pluripotent stem cells (hPSCs) for years. However,HA hydrogel with improved residence time and mechanical integrity that allows the survival of hPSCs under defined conditions is still much needed for clinical applications. In this study,HA was modified with methacrylate functional groups (MeHA) and cross-linked by photo-crosslinking method. After subsequent conjugation with adhesive peptide,these MeHA surfaces demonstrated performance in facilitating human induced pluripotent stem cells (hiPSCs) proliferation,and good pluripotency maintenance of hiPSCs under defined conditions. Moreover,MeHA films on glass-slides exhibited long residence time and mechanical stability throughout hiPSC culture. Our photo-crosslinkable MeHA possesses great value in accelerating the application of HA hydrogel in hiPSCs proliferation and differentiation with the conjugation of adhesive peptides. View Publication

Realization of clinical potential of human pluripotent stem cells (hPSCs) in bone regenerative medicine requires development of simple and safe biomaterials for expansion of hPSCs followed by directing their lineage commitment to osteoblasts. In the present study,a chemically defined peptide-decorated polycaprolactone (PCL) nanofibrous microenvironment was prepared through electrospinning technology and subsequent conjugation with vitronectin peptide to promote the culture and osteogenic potential of hPSCs in vitro. The results indicated that hPSCs successfully proliferated and maintained their pluripotency on the biointerface of peptide-conjugated nanofibers without Matrigel under defined conditions. Moreover,the prepared niche exhibited an appealing ability in promoting directed differentiation of hPSCs to osteoblastic phenotype without embryoid body formation step,determined from the cell morphological alteration,alkaline phosphate activity,and osteogenesis-related gene expression,as well as protein production. Such well-defined,xeno-free,and safe nanofiber scaffolds that allow the survival and facilitate osteo-differentiation of hPSCs provide a novel platform for hPSCs differentiation via cell-nanofiber interplay,and possess great value in accelerating the translational perspectives of hPSCs in bone tissue engineering. View Publication

Realization of the full potential of human induced pluripotent stem cells (hiPSCs) in clinical applications requires development of well-defined conditions for their growth and differentiation. A novel fully defined polyvinyl alcohol/hyaluronan (PVA/HA) polysaccharide nanofiber was developed for hiPSCs culture in commercially available xeno-free,chemically defined medium. Vitronectin peptide (VP) was immobilized to PVA/HA nanofibers through NHS/EDC chemistry. The hiPSCs successfully grew and proliferated on the VP-decorated PVA/HA nanofibers,similar to those on MatrigelTM. Such well-defined,xeno-free and safe nanofiber substrate that supports culture of hiPSCs will not only help to accelerate the translational perspectives of hiPSCs,but also provide a platform to investigate the cell-nanofiber interaction mechanisms that regulate stem cell proliferation and differentiation. ?? 2013 Elsevier Ltd. All rights reserved. View Publication

A comprehensive genetics-based precision medicine strategy to selectively and permanently inactivate only mutant,not normal allele,could benefit many dominantly inherited disorders. Here,we demonstrate the power of our novel strategy of inactivating the mutant allele using haplotype-specific CRISPR/Cas9 target sites in Huntington's disease (HD),a late-onset neurodegenerative disorder due to a toxic dominant gain-of-function CAG expansion mutation. Focusing on improving allele specificity,we combined extensive knowledge of huntingtin (HTT) gene haplotype structure with a novel personalized allele-selective CRISPR/Cas9 strategy based on Protospacer Adjacent Motif (PAM)-altering SNPs to target patient-specific CRISPR/Cas9 sites,aiming at the mutant HTT allele-specific inactivation for a given diplotype. As proof-of-principle,simultaneously using two CRISPR/Cas9 guide RNAs (gRNAs) that depend on PAM sites generated by SNP alleles on the mutant chromosome,we selectively excised ∼44 kb DNA spanning promoter region,transcription start site,and the CAG expansion mutation of the mutant HTT gene,resulting in complete inactivation of the mutant allele without impacting the normal allele. This excision on the disease chromosome completely prevented the generation of mutant HTT mRNA and protein,unequivocally indicating permanent mutant allele-specific inactivation of the HD mutant allele. The perfect allele selectivity with broad applicability of our strategy in disorders with diverse disease haplotypes should also support precision medicine through inactivation of many other gain-of-function mutations. View Publication

Development of pharmaceutical agents for cardiac indication demands elaborate safety screening in which assessing repolarization of cardiac cells remains a critical path in risk evaluations. An efficient platform for evaluating cardiac repolarization in vitro significantly facilitates drug developmental programs. In a proof of principle study,we examined the effect of antiarrhythmogenic drugs (Vaughan Williams class I-IV) and noncardiac active drugs (terfenadine and cisapride) on the repolarization profile of viral-free human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Extracellular field potential (FP) recording using microelectrode arrays demonstrated significant delayed repolarization as prolonged corrected FP durations (cFPDs) by class I (quinidine and flecainide),class III (sotalol and amiodarone),and class IV (verapamil),whereas class II drugs (propranolol and nadolol) had no effects. Consistent with their sodium channel-blocking ability,class I drugs also significantly reduced FPmin and conduction velocity. Although lidocaine (class IB) had no effects on cFPDs,verapamil shortened cFPD and FPmin by 25 and 50%,respectively. Furthermore,verapamil reduced beating frequencies drastically. Importantly,the examined drugs exhibited dose-response curve on prolongation of cFPDs at an effective range that correlated significantly with therapeutic plasma concentrations achieved clinically. Consistent with clinical outcomes,drug-induced arrhythmia of tachycardia and bigeminy-like waveforms by quinidine,flecainide,and sotalol was demonstrated at supraphysiological concentrations. Furthermore,off-target effects of terfenadine and cisapride on cFPD and Na( + ) channel blockage were similarly revealed. These results suggest that hiPSC-CMs may be useful for safety evaluation of cardioactive and noncardiac acting drugs for personalized medicine. View Publication

Cockayne syndrome (CS) is a severe neurodevelopmental disorder characterized by growth abnormalities,premature aging,and photosensitivity. Mutation of Cockayne syndrome B (CSB) affects neuronal gene expression and differentiation,so we attempted to bypass its function by expressing downstream target genes. Intriguingly,ectopic expression of Synaptotagmin 9 (SYT9),a key component of the machinery controlling neurotrophin release,bypasses the need for CSB in neuritogenesis. Importantly,brain-derived neurotrophic factor (BDNF),a neurotrophin implicated in neuronal differentiation and synaptic modulation,and pharmacological mimics such as 7,8-dihydroxyflavone and amitriptyline can compensate for CSB deficiency in cell models of neuronal differentiation as well. SYT9 and BDNF are downregulated in CS patient brain tissue,further indicating that sub-optimal neurotrophin signaling underlies neurological defects in CS. In addition to shedding light on cellular mechanisms underlying CS and pointing to future avenues for pharmacological intervention,these data suggest an important role for SYT9 in neuronal differentiation. View Publication

Mobilization of hematopoietic stem and progenitor cells (HSPCs) from bone marrow into peripheral blood by the cytokine granulocyte colony-stimulating factor (G-CSF) has become the preferred source of HSPCs for stem cell transplants. However,G-CSF fails to mobilize sufficient numbers of stem cells in up to 10% of donors,precluding autologous transplantation in those donors or substantially delaying transplant recovery time. Consequently,new regimens are needed to increase the number of stem cells in peripheral blood upon mobilization. Using a forward genetic approach in mice,we mapped the gene encoding the epidermal growth factor receptor (Egfr) to a genetic region modifying G-CSF-mediated HSPC mobilization. Amounts of EGFR in HSPCs inversely correlated with the cells' ability to be mobilized by G-CSF,implying a negative role for EGFR signaling in mobilization. In combination with G-CSF treatment,genetic reduction of EGFR activity in HSPCs (in waved-2 mutant mice) or treatment with the EGFR inhibitor erlotinib increased mobilization. Increased mobilization due to suppression of EGFR activity correlated with reduced activity of cell division control protein-42 (Cdc42),and genetic Cdc42 deficiency in vivo also enhanced G-CSF-induced mobilization. Our findings reveal a previously unknown signaling pathway regulating stem cell mobilization and provide a new pharmacological approach for improving HSPC mobilization and thereby transplantation outcomes. View Publication

AIMS: Generation of human induced pluripotent stem cell (hiPSC) lines by reprogramming of fibroblast cells with virus-free methods offers unique opportunities for translational cardiovascular medicine. The aim of the study was to reprogramme fibroblast cells to hiPSCs and to study cardiomyogenic properties and ion channel characteristics of the virus-free hiPSC-derived cardiomyocytes. METHODS AND RESULTS: The hiPSCs generated by episomal vectors generated teratomas in severe combined immunodeficient mice,readily formed embryoid bodies,and differentiated into cardiomyocytes with comparable efficiency to human embryonic stem cells. Temporal gene expression of these hiPSCs indicated that differentiation of cardiomyocytes was initiated by increasing expression of cardio/mesodermal markers followed by cardiac-specific transcription factors,structural,and ion channel genes. Furthermore,the cardiomyocytes showed characteristic cross-striations of sarcomeric proteins and expressed calcium-handling and ion channel proteins,confirming their cardiac ontogeny. Microelectrode array recordings established the electrotonic development of a functional syncytium that responded predictably to pharmacologically active drugs. The cardiomyocytes showed a chronotropic dose-response (0.1-10 µM) to isoprenaline and Bay K 8644. Furthermore,carbamycholine (5 µM) suppressed the response to isoprenaline,while verapamil (2.5 µM) blocked Bay K 8644-induced inotropic activity. Moreover,verapamil (1 µM) reduced the corrected field potential duration by 45%,tetrodotoxin (10 µM) shortened the minimal field potential by 40%,and E-4031 (50 nM) prolonged field repolarization. CONCLUSION: Virus-free hiPSCs differentiate efficiently into cardiomyocytes with cardiac-specific molecular,structural,and functional properties that recapitulate the developmental ontogeny of cardiogenesis. These results,coupled with the potential to generate patient-specific hiPSC lines,hold great promise for the development of an in vitro platform for drug pharmacogenomics,disease modelling,and regenerative medicine. View Publication

Cardiomyocytes (CMs) derived from human pluripotent stem cells (hPSCs) offer immense value in studying cardiovascular regenerative medicine. However,intrinsic biases and differential responsiveness of hPSCs towards cardiac differentiation pose significant technical and logistic hurdles that hamper human cardiomyocyte studies. Tandem modulation of canonical and non-canonical Wnt signaling pathways may play a crucial role in cardiac development that can efficiently generate cardiomyocytes from pluripotent stem cells. Our Wnt signaling expression profiles revealed that phasic modulation of canonical/non-canonical axis enabled orderly recapitulation of cardiac developmental ontogeny. Moreover,evaluation of 8 hPSC lines showed marked commitment towards cardiac-mesoderm during the early phase of differentiation,with elevated levels of canonical Wnts (Wnt3 and 3a) and Mesp1. Whereas continued activation of canonical Wnts was counterproductive,its discrete inhibition during the later phase of cardiac differentiation was accompanied by significant up-regulation of non-canonical Wnt expression (Wnt5a and 11) and enhanced Nkx2.5(+) (up to 98%) populations. These Nkx2.5(+) populations transited to contracting cardiac troponin T-positive CMs with up to 80% efficiency. Our results suggest that timely modulation of Wnt pathways would transcend intrinsic differentiation biases of hPSCs to consistently generate functional CMs that could facilitate their scalable production for meaningful clinical translation towards personalized regenerative medicine. View Publication

The chromatin landscape and cellular metabolism both contribute to cell fate determination,but their interplay remains poorly understood. Using genome-wide siRNA screening,we have identified prohibitin (PHB) as an essential factor in self-renewal of human embryonic stem cells (hESCs). Mechanistically,PHB forms protein complexes with HIRA,a histone H3.3 chaperone,and stabilizes the protein levels of HIRA complex components. Like PHB,HIRA is required for hESC self-renewal. PHB and HIRA act together to control global deposition of histone H3.3 and gene expression in hESCs. Of particular note,PHB and HIRA regulate the chromatin architecture at the promoters of isocitrate dehydrogenase genes to promote transcription and,thus,production of α-ketoglutarate,a key metabolite in the regulation of ESC fate. Our study shows that PHB has an unexpected nuclear role in hESCs that is required for self-renewal and that it acts with HIRA in chromatin organization to link epigenetic organization to a metabolic circuit. View Publication

Phosphoinositide 3-kinase (PI3K)-dependent signalling regulates a wide variety of cellular functions including proliferation and differentiation. Disruption of class I(A) PI3K isoforms has implicated PI3K-mediated signalling in development of the early embryo and lymphohaemopoietic system. We have used embryonic stem (ES) cells as an in vitro model to study the involvement of PI3K-dependent signalling during early development and haemopoiesis. Both pharmacological inhibition and genetic manipulation of PI3K-dependent signalling demonstrate that PI3K-mediated signals,most likely via 3-phosphoinositide-dependent protein kinase 1 (PDK1),are required for proliferation of cells within developing embryoid bodies (EBs). Surprisingly,the haemopoietic potential of EB-derived cells was not blocked upon PI3K inhibition but rather enhanced,correlating with modest increases in expression of haemopoietic marker genes. By contrast,PDK1-deficient EB-derived progeny failed to generate terminally differentiated haemopoietic lineages. This deficiency appeared to be due to a requirement for PI3K signalling during the proliferative phase of blast-colony-forming cell (BL-CFC) expansion,rather than as a result of effects on differentiation per se. We also demonstrate that PI3K-dependent signalling is required for optimal generation of erythroid and myeloid progenitors and their differentiation into mature haemopoietic colony types. These data demonstrate that PI3K-dependent signals play important roles at different stages of haemopoietic development. View Publication