技术资料

PURPOSE To determine the safety,survival,and functionality of human embryonic stem cell-derived RPE (hESC-RPE) cells seeded on a polymeric substrate (rCPCB-RPE1 implant) and implanted into the subretinal (SR) space of Royal College of Surgeons (RCS) rats. METHODS Monolayers of hESC-RPE cells cultured on parylene membrane were transplanted into the SR space of 4-week-old RCS rats. Group 1 (n = 46) received vitronectin-coated parylene membrane without cells (rMSPM+VN),group 2 (n = 59) received rCPCB-RPE1 implants,and group 3 (n = 13) served as the control group. Animals that are selected based on optical coherence tomography screening were subjected to visual function assays using optokinetic (OKN) testing and superior colliculus (SC) electrophysiology. At approximately 25 weeks of age (21 weeks after surgery),the eyes were examined histologically for cell survival,phagocytosis,and local toxicity. RESULTS Eighty-seven percent of the rCPCB-RPE1-implanted animals showed hESC-RPE survivability. Significant numbers of outer nuclear layer cells were rescued in both group 1 (rMSPM+VN) and group 2 (rCPCB-RPE1) animals. A significantly higher ratio of rod photoreceptor cells to cone photoreceptor cells was found in the rCPCB-RPE1-implanted group. Animals with rCPCB-RPE1 implant showed hESC-RPE cells containing rhodopsin-positive particles in immunohistochemistry,suggesting phagocytic function. Superior colliculus mapping data demonstrated that a significantly higher number of SC sites responded to light stimulus at a lower luminance threshold level in the rCPCB-RPE1-implanted group. Optokinetic data suggested both implantation groups showed improved visual acuity. CONCLUSIONS These results demonstrate the safety,survival,and functionality of the hESC-RPE monolayer transplantation in an RPE dysfunction rat model. View Publication

Monoclonal antibodies offer high specificity and this makes it an important tool for molecular biology,biochemistry and medicine. Typically,monoclonal antibodies are generated by fusing mouse spleen cells that have been immunized with the desired antigen with myeloma cells to create immortalized hybridomas. Here,we describe the generation of monoclonal antibodies that are specific to Chikungunya virus using ClonaCell-HY system. View Publication

The lipophilic statin lovastatin decreases cholesterol synthesis and is a safe and effective treatment for the prevention of cardiovascular diseases. Growing evidence points at antitumor potential of lovastatin. Therefore,understanding the molecular mechanism of lovastatin function in different cell types is critical to effective therapy design. In this study,we investigated the effects of lovastatin on the differentiation potential of human embryonic stem (hES) cells (H9 cell line). Multiparameter flow cytometric assay was used to detect changes in the expression of transcription factors characteristic of hES cells. We found that lovastatin treatment delayed NANOG downregulation during ectodermal and endodermal differentiation. Likewise,expression of ectodermal (SOX1 and OTX2) and endodermal (GATA4 and FOXA2) markers was higher in treated cells. Exposure of hES cells to lovastatin led to a minor decrease in the expression of SSEA-3 and a significant reduction in CD133 expression. Treated cells also formed fewer embryoid bodies than control cells. By analyzing hES with and without CD133,we discovered that CD133 expression is required for proper formation of embryoid bodies. In conclusion,lovastatin reduced the heterogeneity of hES cells and impaired their differentiation potential. View Publication

Mitochondrial DNA (mtDNA) mutations are maternally inherited and are associated with a broad range of debilitating and fatal diseases. Reproductive technologies designed to uncouple the inheritance of mtDNA from nuclear DNA may enable affected women to have a genetically related child with a greatly reduced risk of mtDNA disease. Here we report the first preclinical studies on pronuclear transplantation (PNT). Surprisingly,techniques used in proof-of-concept studies involving abnormally fertilized human zygotes were not well tolerated by normally fertilized zygotes. We have therefore developed an alternative approach based on transplanting pronuclei shortly after completion of meiosis rather than shortly before the first mitotic division. This promotes efficient development to the blastocyst stage with no detectable effect on aneuploidy or gene expression. After optimization,mtDNA carryover was reduced to textless2% in the majority (79%) of PNT blastocysts. The importance of reducing carryover to the lowest possible levels is highlighted by a progressive increase in heteroplasmy in a stem cell line derived from a PNT blastocyst with 4% mtDNA carryover. We conclude that PNT has the potential to reduce the risk of mtDNA disease,but it may not guarantee prevention. View Publication

Electrospun poly-l-lactic acid (PLLA) nanofiber mats carrying surface amine groups,previously introduced by nitrogen atmospheric pressure nonequilibrium plasma,are embedded into aqueous solutions of oligomeric acrylamide-end capped AGMA1,a biocompatible polyamidoamine with arg-gly-asp (RGD)-reminiscent repeating units. The resultant mixture is finally cured giving PLLA-AGMA1 hydrogel composites that absorb large amounts of water and,in the swollen state,are translucent,soft,and pliable,yet as strong as the parent PLLA mat. They do not split apart from each other when swollen in water and remain highly flexible and resistant,since the hydrogel portion is covalently grafted onto the PLLA nanofibers via the addition reaction of the surface amine groups to a part of the terminal acrylic double bonds of AGMA1 oligomers. Preliminary tested as scaffolds,the composites prove capable of maintaining short-term undifferentiated cultures of human pluripotent stem cells in feeder-free conditions. View Publication

How metabolism is reprogrammed during neuronal differentiation is unknown. We found that the loss of hexokinase (HK2) and lactate dehydrogenase (LDHA) expression,together with a switch in pyruvate kinase gene splicing from PKM2 to PKM1,marks the transition from aerobic glycolysis in neural progenitor cells (NPC) to neuronal oxidative phosphorylation. The protein levels of c-MYC and N-MYC,transcriptional activators of the HK2 and LDHA genes,decrease dramatically. Constitutive expression of HK2 and LDHA during differentiation leads to neuronal cell death,indicating that the shut-off aerobic glycolysis is essential for neuronal survival. The metabolic regulators PGC-1α and ERRγ increase significantly upon neuronal differentiation to sustain the transcription of metabolic and mitochondrial genes,whose levels are unchanged compared to NPCs,revealing distinct transcriptional regulation of metabolic genes in the proliferation and post-mitotic differentiation states. Mitochondrial mass increases proportionally with neuronal mass growth,indicating an unknown mechanism linking mitochondrial biogenesis to cell size. View Publication

Identification and quantification of the characteristics of stem cell preparations is critical for understanding stem cell biology and for the development and manufacturing of stem cell based therapies. We have developed image analysis and visualization software that allows effective use of time-lapse microscopy to provide spatial and dynamic information from large numbers of human embryonic stem cell colonies. To achieve statistically relevant sampling,we examined textgreater 680 colonies from 3 different preparations of cells over 5 days each,generating a total experimental dataset of 0.9 terabyte (TB). The 0.5 Giga-pixel images at each time point were represented by multi-resolution pyramids and visualized using the Deep Zoom Javascript library extended to support viewing Giga-pixel images over time and extracting data on individual colonies. We present a methodology that enables quantification of variations in nominally-identical preparations and between colonies,correlation of colony characteristics with Oct4 expression,and identification of rare events. View Publication

Stem cell-induced hepatocytes (SC-iHeps) have been suggested as a valuable model for evaluating drug toxicology. Here,human-induced pluripotent stem cells (QIA7) and embryonic stem cells (WA01) were differentiated into hepatocytes,and the hepatotoxic effects of acetaminophen (AAP) and aflatoxin B1 (AFB1) were compared with primary hepatocytes (p-Heps) and HepG2. In a cytotoxicity assay,the IC50 of SC-iHeps was similar to that in p-Heps and HepG2 in the AAP groups but different from that in p-Heps of the AFB1 groups. In a multi-parameter assay,phenotypic changes in mitochondrial membrane potential,calcium influx and oxidative stress were similar between QIA7-iHeps and p-Heps following AAP and AFB1 treatment but relatively low in WA01-iHeps and HepG2. Most hepatic functional markers (hepatocyte-specific genes,albumin/urea secretion,and the CYP450 enzyme activity) were decreased in a dose-dependent manner following AAP and AFB1 treatment in SC-iHeps and p-Heps but not in HepG2. Regarding CYP450 inhibition,the cell viability of SC-iHeps and p-Heps was increased by ketoconazole,a CYP3A4 inhibitor. Collectively,SC-iHeps and p-Heps showed similar cytotoxicity and hepatocyte functional effects for AAP and AFB1 compared with HepG2. Therefore,SC-iHeps have phenotypic characteristics and sensitivity to cytotoxic chemicals that are more similar to p-Heps than to HepG2 cells. View Publication

Recent advances in developmental biology and stem cell technology have led to the engineering of functional organs in a dish. However,the limited size of these organoids and absence of a large circulatory system poses limits to its clinical translation. To overcome these issues,decellularized whole kidney scaffolds with native microstructure and extracellular matrix (ECM) are employed for kidney bioengineering,using human-induced pluripotent-stem-cell-derived renal progenitor cells and endothelial cells. To demonstrate ECM-guided cellular assembly,the present work is focused on generating the functional unit of the kidney,the glomerulus. In the repopulated organ,the presence of endothelial cells broadly upregulates the expression level of genes related to renal development. When the cellularized native scaffolds are implanted in SCID mice,glomeruli assembly can be achieved by co-culture of the renal progenitors and endothelial cells. These individual glomerular units are shown to be functional in the context of the whole organ using a simulated bio-reactor set-up with urea and creatinine excretion and albumin reabsorption. Our results indicate that the repopulation of decellularized native kidney using clinically relevant,expandable patient-specific renal progenitors and endothelial cells may be a viable approach for the generation of a functional whole kidney. View Publication

As known from model organisms,such as frog,fish,mouse and chicken,the anterior-posterior patterning of the definitive endoderm (DE) into distinct domains is controlled by a variety of signaling interactions between the DE and its surrounding mesoderm. This includes Wnt/FGFs and BMPs in the posterior half and all-trans-retinoic acid,TGF-$$-ligands,Wnt- and BMP-inhibitors in the anterior half of the DE sheet. However,it is currently unclear how these embryonic tissue interactions can be translated into a defined differentiation protocol for human embryonic stem cells. Activin A has been proposed to direct DE into a SOX2-positive foregut-like cell type. Due to the pleiotropic nature of SOX2 in pluripotency and developing cells of the foregut we purified DE-cells by magnetic cell sorting and tested the effects of anteriorizing and posteriorizing factors on pure endoderm. We show in contrast to previous studies that the generation of the foregut marked by SOX2/FOXA2 double-positive cells does not depend on activin A/TGF-$$-signaling but is mediated by the inhibition of Wnt- and BMP-signaling. Retinoic acid can posteriorize and at the same time dorsalize the foregut towards a PDX1-positive pancreatic duodenal cell type whereas active Wnt/beta-catenin signaling synergistically with FGF-2,BMP-4 and RA induces the formation of CDX2-positive posterior endoderm. Thus,these results provide new insights into the mechanisms behind cell specification of human DE derived from pluripotent stem cells. This article is protected by copyright. All rights reserved. View Publication

Small molecules are powerful tools for investigating protein function and can serve as leads for new therapeutics. Most human proteins,however,lack small-molecule ligands,and entire protein classes are considered 'undruggable'. Fragment-based ligand discovery can identify small-molecule probes for proteins that have proven difficult to target using high-throughput screening of complex compound libraries. Although reversibly binding ligands are commonly pursued,covalent fragments provide an alternative route to small-molecule probes,including those that can access regions of proteins that are difficult to target through binding affinity alone. Here we report a quantitative analysis of cysteine-reactive small-molecule fragments screened against thousands of proteins in human proteomes and cells. Covalent ligands were identified for textgreater700 cysteines found in both druggable proteins and proteins deficient in chemical probes,including transcription factors,adaptor/scaffolding proteins,and uncharacterized proteins. Among the atypical ligand-protein interactions discovered were compounds that react preferentially with pro- (inactive) caspases. We used these ligands to distinguish extrinsic apoptosis pathways in human cell lines versus primary human T cells,showing that the former is largely mediated by caspase-8 while the latter depends on both caspase-8 and -10. Fragment-based covalent ligand discovery provides a greatly expanded portrait of the ligandable proteome and furnishes compounds that can illuminate protein functions in native biological systems. View Publication

Mechanisms determining intrinsic differentiation bias inherent to human pluripotent stem cells (hPSCs) toward cardiogenic fate remain elusive. We evaluated the interplay between ErbB4 and EGFR in determining cardiac differentiation in vitro as these receptor tyrosine kinases (RTKs) are key to heart and brain development in vivo. Our results demonstrate that during cardiac differentiation,cell fate biases exist in hPSCs due to cardiac/neuroectoderm divergence post cardiac mesoderm stage. Stage-specific up-regulation of EGFR in concert with persistent Wnt3a signaling post cardiac mesoderm favors commitment towards neural progenitor cells (NPCs). Inhibition of EGFR abrogates these effects with enhanced (textgreater2-fold) cardiac differentiation efficiencies by increasing proliferation of Nkx2-5 expressing cardiac progenitors while reducing proliferation of Sox2 expressing NPCs. Forced overexpression of ErbB4 rescued cardiac commitment by augmenting Wnt11 signaling. Convergence between EGFR/ErbB4 and canonical/non-canonical Wnt signaling determines cardiogenic fate in hPSCs. This article is protected by copyright. All rights reserved. View Publication