参考文献

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

Data suggest that clinical applications of human induced pluripotent stem cells (hiPSCs) will be realized. Nonetheless,clinical applications will require hiPSCs that are free of exogenous DNA and that can be manufactured through Good Manufacturing Practice (GMP). Optimally,derivation of hiPSCs should be rapid and efficient in order to minimize manipulations,reduce potential for accumulation of mutations and minimize financial costs. Previous studies reported the use of modified synthetic mRNAs to reprogram fibroblasts to a pluripotent state. Here,we provide an optimized,fully chemically defined and feeder-free protocol for the derivation of hiPSCs using synthetic mRNAs. The protocol results in derivation of fully reprogrammed hiPSC lines from adult dermal fibroblasts in less than two weeks. The hiPSC lines were successfully tested for their identity,purity,stability and safety at a GMP facility and cryopreserved. To our knowledge,as a proof of principle,these are the first integration-free iPSCs lines that were reproducibly generated through synthetic mRNA reprogramming that could be putatively used for clinical purposes. View Publication

Induced pluripotent stem cells (iPSCs) derived from somatic cells of patients can be a good model for studying human diseases and for future therapeutic regenerative medicine. Current initiatives to establish human iPSC (hiPSC) banking face challenges in recruiting large numbers of donors with diverse diseased,genetic,and phenotypic representations. In this study,we describe the efficient derivation of transgene-free hiPSCs from human finger-prick blood. Finger-prick sample collection can be performed on a do-it-yourself" basis by donors and sent to the hiPSC facility for reprogramming. We show that single-drop volumes of finger-prick samples are sufficient for performing cellular reprogramming� View Publication

One of the differences between murine and human embryonic stem cells (ESCs) is the epigenetic state of the X chromosomes in female lines. Murine ESCs (mESCs) present two transcriptionally active Xs that will undergo the dosage compensation process of XCI upon differentiation,whereas most human ESCs (hESCs) spontaneously inactivate one X while keeping their pluripotency. Whether this reflects differences in embryonic development of mice and humans,or distinct culture requirements for the two kinds of pluripotent cells is not known. Recently it has been shown that hESCs established in physiological oxygen levels are in a stable pre-XCI state equivalent to that of mESCs,suggesting that culture in low oxygen concentration is enough to preserve that epigenetic state of the X chromosomes. Here we describe the establishment of two new lines of hESCs under physiological oxygen level and the characterization of the XCI state in the 46,XX line BR-5. We show that a fraction of undifferentiated cells present XIST RNA accumulation and single H3K27me foci,characteristic of the inactive X. Moreover,analysis of allele specific gene expression suggests that pluripotent BR-5 cells present completely skewed XCI. Our data indicate that physiological levels of oxygen are not sufficient for the stabilization of the pre-XCI state in hESCs. View Publication

Efficient derivation of large-scale motor neurons (MNs) from human pluripotent stem cells is central to the understanding of MN development,modelling of MN disorders in vitro and development of cell-replacement therapies. Here we develop a method for rapid (20 days) and highly efficient (˜70%) differentiation of mature and functional MNs from human pluripotent stem cells by tightly modulating neural patterning temporally at a previously undefined primitive neural progenitor stage. This method also allows high-yield (textgreater250%) MN production in chemically defined adherent cultures. Furthermore,we show that Islet-1 is essential for formation of mature and functional human MNs,but,unlike its mouse counterpart,does not regulate cell survival or suppress the V2a interneuron fate. Together,our discoveries improve the strategy for MN derivation,advance our understanding of human neural specification and MN development,and provide invaluable tools for human developmental studies,drug discovery and regenerative medicine. View Publication

Self-renewable human pluripotent stem cells (hPSCs) serve as a potential unlimited ex vivo source of human cardiomyocytes (CMs) for cell-based disease modeling and therapies. Although recent advances in directed differentiation protocols have enabled more efficient derivation of hPSC-derived CMs with an efficiency of ∼50%-80% CMs and a final yield of ∼1-20 CMs per starting undifferentiated hPSC,these protocols are often not readily transferrable across lines without first optimizing multiple parameters. Further,the resultant populations are undefined for chamber specificity or heterogeneous containing mixtures of atrial,ventricular (V),and pacemaker derivatives. Here we report a highly cost-effective and reproducibly efficient system for deriving hPSC-ventricular cardiomyocytes (VCMs) from all five human embryonic stem cell (HES2,H7,and H9) and human induced PSC (hiPSC) (reprogrammed from human adult peripheral blood CD34(+) cells using nonintegrating episomal vectors) lines tested. Cardiogenic embryoid bodies could be formed by the sequential addition of BMP4,Rho kinase inhibitor,activin-A,and IWR-1. Spontaneously contracting clusters appeared as early as day 8. At day 16,up to 95% of cells were cTnT(+). Of which,93%,94%,100%,92%,and 92% of cardiac derivatives from HES2,H7,H9,and two iPSC lines,respectively,were VCMs as gauged by signature ventricular action potential and ionic currents (INa(+)/ICa,L(+)/IKr(+)/IKATP(+)); Ca(2+) transients showed positive chronotropic responses to $\$-adrenergic stimulation. Our simple,cost-effective protocol required the least amounts of reagents and time compared with others. While the purity and percentage of PSC-VCMs were comparable to a recently published protocol,the present yield and efficiency with a final output of up to 70 hPSC-VCMs per hPSC was up to 5-fold higher and without the need of performing line-specific optimization. These differences were discussed. The results may lead to mass production of hPSC-VCMs in bioreactors. View Publication

Murine hybridomas producing neutralizing mAbs specific to the pandemic influenza virus A/California/07/2009 haemagglutinin (HA) were isolated. These antibodies recognized at least two different but overlapping new epitopes that were conserved in the HA of most Spanish pandemic isolates. However,one of these isolates (A/Extremadura/RR6530/2010) lacked reactivity with the mAbs and carried two unique mutations in the HA head (S88Y and K136N) that were required simultaneously to eliminate reactivity with the murine antibodies. This unusual requirement directly illustrates the phenomenon of enhanced antigenic change proposed previously for the accumulation of simultaneous amino acid substitutions at antigenic sites of the influenza A virus HA during virus evolution (Shih et al.,Proc Natl Acad Sci USA,104,6283-6288,2007). The changes found in the A/Extremadura/RR6530/2010 HA were not found in escape mutants selected in vitro with one of the mAbs,which contained instead nearby single amino acid changes in the HA head. Thus,either single or double point mutations may similarly alter epitopes of the new antigenic site identified in this work in the 2009 H1N1 pandemic virus HA. Moreover,this site is relevant for the human antibody response,as shown by competition of mAbs and human post-infection sera for virus binding. The results are discussed in the context of the HA antigenic structure and challenges posed for identification of sequence changes with possible antigenic impact during virus surveillance. View Publication

A rapid,ultrasensitive,and practical label-free impedimetric immunoassay for measuring trace levels of total polychlorinated biphenyls (PCBs) in insulating oil was developed. First,we developed a novel monoclonal antibody (RU6F9) for PCBs by using a designed immunogen and characterized its binding affinity for a commercial mixtures of PCBs and its main congeners. A micro comblike gold electrode was fabricated,and the antibody was covalently immobilized on the electrode through a self-assembled monolayer formed by dithiobis-N-succinimidyl propionate. The antigen-binding event on the surface of the functionalized electrode was determined as the change in charge transfer resistance by using electrochemical impedance spectroscopy. The resulting impedimetric immunoassay in aqueous solution achieved a wide determination range (0.01-10 μg/L) and a low detection limit (LOD) of 0.001 μg/L,which was 100-fold more sensitive than a conventional flow-based immunoassay for PCBs. By combining the impedimetric immunoassay with a cleanup procedure for insulating oil utilizing a multilayer cleanup column followed by DMSO partitioning,an LOD of 0.052 mg/kg-oil was achieved,which satisfied the Japanese regulation criterion of 0.5 mg/kg-oil. Finally,the immunoassay was employed to determine total PCB levels in actual used insulating oils (n = 33) sampled from a used transformer containing trace levels of PCBs,and the results agreed well with the Japanese official method (HRGC/HRMS). View Publication

Monoclonal antibodies (mAbs) have proven to be instrumental in the advancement of research,diagnostic,industrial vaccine,and therapeutic applications. The use of mAbs in laboratory protocols has been growing in an exponential fashion for the last four decades. Described herein are methods for the development of highly specific mAbs through traditional hybridoma fusion. For ultimate success,a series of simultaneously initiated protocols are to be undertaken with careful attention to cell health of both the myeloma fusion partner and immune splenocytes. Coordination and attention to detail will enable a researcher with basic tissue culture skills to generate mAbs from immunized rodents to a variety of antigens (including proteins,carbohydrates,DNA,and haptens) (see Note 1). Furthermore,in vivo and in vitro methods used for antigen sensitization of splenocytes prior to somatic fusion are described herein. View Publication

Translation of stem cell research to industrial and clinical settings mostly requires large quantities of cells,especially those involving large organs such as the liver. A scalable reactor system is desirable to ensure a reliable supply of sufficient quantities of differentiated cells. To increase the culture efficiency in bioreactor system,high surface to volume ratio needs to be achieved. We employed a microcarrier culture system for the expansion of undifferentiated human embryonic stem cells (hESCs) as well as for directed differentiation of these cells to hepatocyte-like cells. Cells in single cell suspension were attached to the bead surface in even distribution and were expanded to 1??106cells/ml within 2 days of hESC culture with maintenance of the level of pluripotency markers. Directed differentiation into hepatocyte-like cells on microcarriers,both in static culture and stirred bioreactors,induced similar levels of hepatocyte-like cell differentiation as observed with cells cultured in conventional tissue culture plates. The cells expressed both immature and mature hepatocyte-lineage genes and proteins such as asialoglycoprotein receptor-1 (ASGPR-1) and albumin. Differentiated cells exhibited functional characteristics such as secretion of albumin and urea,and CYP3A4 activity could be detected. Microcarriers thus offer the potential for large-scale expansion and differentiation of hESCs induced hepatocyte-like cells in a more controllable bioreactor environment. ?? 2014. View Publication

In February 2013,zoonotic transmission of a novel influenza A virus of the H7N9 subtype was reported in China. Although at present no sustained human-to-human transmission has been reported,a pandemic outbreak of this H7N9 virus is feared. Since neutralizing antibodies to the hemagglutinin (HA) globular head domain of the virus are virtually absent in the human population,there is interest in identifying other correlates of protection,such as cross-reactive CD8(+) T cells (cytotoxic T lymphocytes [CTLs]) elicited during seasonal influenza A virus infections. These virus-specific CD8(+) T cells are known to recognize conserved internal proteins of influenza A viruses predominantly,but it is unknown to what extent they cross-react with the newly emerging H7N9 virus. Here,we assessed the cross-reactivity of seasonal H3N2 and H1N1 and pandemic H1N1 influenza A virus-specific polyclonal CD8(+) T cells,obtained from HLA-typed study subjects,with the novel H7N9 virus. The cross-reactivity of CD8(+) T cells to H7N9 variants of known influenza A virus epitopes and H7N9 virus-infected cells was determined by their gamma interferon (IFN-γ) response and lytic activity. It was concluded that,apart from recognition of individual H7N9 variant epitopes,CD8(+) T cells to seasonal influenza viruses display considerable cross-reactivity with the novel H7N9 virus. The presence of these cross-reactive CD8(+) T cells may afford some protection against infection with the new virus. View Publication

A significant clinical need exists to differentiate human pluripotent stem cells (hPSCs) into cardiomyocytes,enabling tissue modeling for in vitro discovery of new drugs or cell-based therapies for heart repair in vivo. Chemical and mechanical microenvironmental factors are known to impact the efficiency of stem cell differentiation,but cardiac differentiation protocols in hPSCs are typically performed on rigid tissue culture polystyrene (TCPS) surfaces,which do not present a physiological mechanical setting. To investigate the temporal effects of mechanics on cardiac differentiation,we cultured human embryonic stem cells (hESCs) and their derivatives on polyacrylamide hydrogel substrates with a physiologically relevant range of stiffnesses. In directed differentiation and embryoid body culture systems,differentiation of hESCs to cardiac troponin T-expressing (cTnT+) cardiomyocytes peaked on hydrogels of intermediate stiffness. Brachyury expression also peaked on intermediate stiffness hydrogels at day 1 of directed differentiation,suggesting that stiffness impacted the initial differentiation trajectory of hESCs to mesendoderm. To investigate the impact of substrate mechanics during cardiac specification of mesodermal progenitors,we initiated directed cardiomyocyte differentiation on TCPS and transferred cells to hydrogels at the Nkx2.5/Isl1+ cardiac progenitor cell stage. No differences in cardiomyocyte purity with stiffness were observed on day 15. These experiments indicate that differentiation of hESCs is sensitive to substrate mechanics at early stages of mesodermal induction,and proper application of substrate mechanics can increase the propensity of hESCs to differentiate to cardiomyocytes. textcopyright 2013 Acta Materialia Inc. View Publication