参考文献

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

Extracellular vesicles (EVs) are phospholipid-based particles endogenously produced by cells. Their natural composition and selective cell interactions make them promising drug carriers. However,in order to harness their properties,efficient exogenous drug encapsulation methods need to be investigated. Here,EVs from various cellular origins (endothelial,cancer and stem cells) were produced and characterised for size and composition. Porphyrins of different hydrophobicities were employed as model drugs and encapsulated into EVs using various passive and active methods (electroporation,saponin,extrusion and dialysis). Hydrophobic compounds loaded very efficiently into EVs and at significantly higher amounts than into standard liposomes composed of phosphocholine and cholesterol using passive incubation. Moreover,loading into EVs significantly increased the cellular uptake by textgreater60% and the photodynamic effect of hydrophobic porphyrins in vitro compared to free or liposome encapsulated drug. The active encapsulation techniques,with the saponin-assisted method in particular,allowed an up to 11 fold higher drug loading of hydrophilic porphyrins compared to passive methods. EVs loaded with hydrophilic porphyrins induced a stronger phototoxic effect than free drug in a cancer cell model. Our findings create a firm basis for the development of EVs as smart drug carriers based on straightforward and transferable methods. View Publication

Long interspersed element-1 (LINE-1 or L1) retrotransposition induces insertional mutations that can result in diseases. It was recently shown that the copy number of L1 and other retroelements is stable in induced pluripotent stem cells (iPSCs). However,by using an engineered reporter construct over-expressing L1,another study suggests that reprogramming activates L1 mobility in iPSCs. Given the potential of human iPSCs in therapeutic applications,it is important to clarify whether these cells harbor somatic insertions resulting from endogenous L1 retrotransposition. Here,we verified L1 expression during and after reprogramming as well as potential somatic insertions driven by the most active human endogenous L1 subfamily (L1Hs). Our results indicate that L1 over-expression is initiated during the reprogramming process and is subsequently sustained in isolated clones. To detect potential somatic insertions in iPSCs caused by L1Hs retotransposition,we used a novel sequencing strategy. As opposed to conventional sequencing direction,we sequenced from the 3' end of L1Hs to the genomic DNA,thus enabling the direct detection of the polyA tail signature of retrotransposition for verification of true insertions. Deep coverage sequencing thus allowed us to detect seven potential somatic insertions with low read counts from two iPSC clones. Negative PCR amplification in parental cells,presence of a polyA tail and absence from seven L1 germline insertion databases highly suggested true somatic insertions in iPSCs. Furthermore,these insertions could not be detected in iPSCs by PCR,likely due to low abundance. We conclude that L1Hs retrotransposes at low levels in iPSCs and therefore warrants careful analyses for genotoxic effects. View Publication

UNLABELLED: Due to continuous changes to its antigenic regions,influenza viruses can evade immune detection and cause a significant amount of morbidity and mortality around the world. Influenza vaccinations can protect against disease but must be annually reformulated to match the current circulating strains. In the development of a broad-spectrum influenza vaccine,the elucidation of conserved epitopes is paramount. To this end,we designed an immunization strategy in mice to boost the humoral response against conserved regions of the hemagglutinin (HA) glycoprotein. Of note,generation and identification of broadly neutralizing antibodies that target group 2 HAs are rare and thus far have yielded only a few monoclonal antibodies (MAbs). Here,we demonstrate that mouse MAb 9H10 has broad and potent in vitro neutralizing activity against H3 and H10 group 2 influenza A subtypes. In the mouse model,MAb 9H10 protects mice against two divergent mouse-adapted H3N2 strains,in both pre- and postexposure administration regimens. In vitro and cell-free assays suggest that MAb 9H10 inhibits viral replication by blocking HA-dependent fusion of the viral and endosomal membranes early in the replication cycle and by disrupting viral particle egress in the late stage of infection. Interestingly,electron microscopy reconstructions of MAb 9H10 bound to the HA reveal that it binds a similar binding footprint to MAbs CR8020 and CR8043.backslashnbackslashnIMPORTANCE: The influenza hemagglutinin is the major antigenic target of the humoral immune response. However,due to continuous antigenic changes that occur on the surface of this glycoprotein,influenza viruses can escape the immune system and cause significant disease to the host. Toward the development of broad-spectrum therapeutics and vaccines against influenza virus,elucidation of conserved regions of influenza viruses is crucial. Thus,defining these types of epitopes through the generation and characterization of broadly neutralizing monoclonal antibodies (MAbs) can greatly assist others in highlighting conserved regions of hemagglutinin. Here,we demonstrate that MAb 9H10 that targets the hemagglutinin stalk has broadly neutralizing activity against group 2 influenza A viruses in vitro and in vivo. View Publication

Human pluripotent stem cells (hPSCs) tend to acquire genomic aberrations in culture,the most common of which is trisomy of chromosome 12. Here we dissect the cellular and molecular implications of this trisomy in hPSCs. Global gene expression analyses reveal that trisomy 12 profoundly affects the gene expression profile of hPSCs,inducing a transcriptional programme similar to that of germ cell tumours. Comparison of proliferation,differentiation and apoptosis between diploid and aneuploid hPSCs shows that trisomy 12 significantly increases the proliferation rate of hPSCs,mainly as a consequence of increased replication. Furthermore,trisomy 12 increases the tumorigenicity of hPSCs in vivo,inducing transcriptionally distinct teratomas from which pluripotent cells can be recovered. Last,a chemical screen of 89 anticancer drugs discovers that trisomy 12 raises the sensitivity of hPSCs to several replication inhibitors. Together,these findings demonstrate the extensive effect of trisomy 12 and highlight its perils for successful hPSC applications. View Publication

Human induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM)-based assays are emerging as a promising tool for the in vitro preclinical screening of QT interval-prolonging side effects of drugs in development. A major impediment to the widespread use of human iPSC-CM assays is the low throughput of the currently available electrophysiological tools. To test the precision and applicability of the near-infrared fluorescent voltage-sensitive dye 1-(4-sulfanatobutyl)-4-β[2-(di-n-butylamino)-6-naphthyl]butadienylquinolinium betaine (di-4-ANBDQBS) for moderate-throughput electrophysiological analyses,we compared simultaneous transmembrane voltage and optical action potential (AP) recordings in human iPSC-CM loaded with di-4-ANBDQBS. Optical AP recordings tracked transmembrane voltage with high precision,generating nearly identical values for AP duration (AP durations at 10%,50%,and 90% repolarization). Human iPSC-CMs tolerated repeated laser exposure,with stable optical AP parameters recorded over a 30-min study period. Optical AP recordings appropriately tracked changes in repolarization induced by pharmacological manipulation. Finally,di-4-ANBDQBS allowed for moderate-throughput analyses,increasing throughput textgreater10-fold over the traditional patch-clamp technique. We conclude that the voltage-sensitive dye di-4-ANBDQBS allows for high-precision optical AP measurements that markedly increase the throughput for electrophysiological characterization of human iPSC-CMs. View Publication

AbstractBack to TopbackslashnNeurons produced from stem cells have emerged as a tool to identify new therapeutic targets for neurological diseases such as amyotrophic lateral sclerosis (ALS). However,it remains unclear to what extent these new mechanistic insights will translate to animal models,an important step in the validation of new targets. Previously,we found that glia from mice carrying the SOD1G93A mutation,a model of ALS,were toxic to stem cell–derived human motor neurons. We use pharmacological and genetic approaches to demonstrate that the prostanoid receptor DP1 mediates this glial toxicity. Furthermore,we validate the importance of this mechanism for neural degeneration in vivo. Genetic ablation of DP1 in SOD1G93A mice extended life span,decreased microglial activation,and reduced motor neuron loss. Our findings suggest that blocking DP1 may be a therapeutic strategy in ALS and demonstrate that discoveries from stem cell models of disease can be corroborated in vivo. View Publication

mAbs constitute an important biological tool for influenza virus haemagglutinin (HA) epitope mapping through the generation of escape mutants,which could provide insights into immune evasion mechanisms and may benefit the future development of vaccines. Several influenza A (H1N1) pandemic 2009 (pdm09) HA escape mutants have been recently described. However,the HA antigenic sites of the previous seasonal A/Brisbane/59/2007 (H1N1) (Bris07) virus remain poorly documented. Here,we produced mAbs against pdm09 and Bris07 HA proteins expressed in human HEK293 cells. Escape mutants were generated using mAbs that exhibited HA inhibition and neutralizing activities. The resulting epitope mapping of the pdm09 HA protein revealed 11 escape mutations including three that were previously described (G172E,N173D and K256E) and eight novel ones (T89R,F128L,G157E,K180E,A212E,R269K,N311T and G478E). Among the six HA mutations that were part of predicted antigenic sites (Ca1,Ca2,Cb,Sa or Sb),three (G172E,N173D and K180E) were within the Sa site. Eight escape mutations (H54N,N55D,N55K,L60H,N203D,A231T,V314I and K464E) were obtained for Bris07 HA,and all but one (N203D,Sb site) were outside the predicted antigenic sites. Our results suggest that the Sa antigenic site is immunodominant in pdm09 HA,whereas the N203D mutation (Sb site),present in three different Bris07 escape mutants,appears as the immunodominant epitope in that strain. The fact that some mutations were not part of predicted antigenic sites reinforces the necessity of further characterizing the HA of additional H1N1 strains. View Publication

Induced pluripotent stem cells (IPS) are an artificially derived type of pluripotent stem cell,showing many of the same characteristics as natural pluripotent stem cells. IPS are a hopeful therapeutic model; however there is a critical need to determine their response to environmental toxins. Effects of arsenic on cells have been studied extensively; however,its effect on IPS is yet to be elucidated. Arsenic trioxide (ATO) has been shown to inhibit cell proliferation,induce apoptosis and genotoxicity in many cells. Based on ATOs action in other cells,we hypothesize that it will induce alterations in morphology,inhibit cell viability and induce a genotoxic effect on IPS. Cells were treated for 24 hours with ATO (0-9 µg/mL). Cell morphology,viability and DNA damage were documented. Results indicated sufficient changes in morphology of cell colonies mainly in cell ability to maintain grouping and ability to remain adherent. Cell viability decreased in a dose dependent manner. There were significant increases in tail length and moment as well as destruction of intact DNA as concentration increased. Exposure to ATO resulted in a reproducible dose dependent sequence of events marked by changes in morphology,decrease of cell viability,and induction of genotoxicity in IPS. View Publication

The development of novel platforms for large scale production of human embryonic stem cells (hESC) derived cardiomyocytes (CM) becomes more crucial as the demand for CMs in preclinical trials,high throughput cardio toxicity assays and future regenerative therapeutics rises. To this end,we have designed a microcarrier (MC) suspension agitated platform that integrates pluripotent hESC expansion followed by CM differentiation in a continuous,homogenous process.Hydrodynamic shear stresses applied during the hESC expansion and CM differentiation steps drastically reduced the capability of the cells to differentiate into CMs. Applying vigorous stirring during pluripotent hESC expansion on Cytodex 1 MC in spinner cultures resulted in low CM yields in the following differentiation step (cardiac troponin-T (cTnT): 22.83. ??. 2.56%; myosin heavy chain (MHC): 19.30. ??. 5.31%). Whereas the lower shear experienced in side to side rocker (wave type) platform resulted in higher CM yields (cTNT: 47.50. ??. 7.35%; MHC: 42.85. ??. 2.64%). The efficiency of CM differentiation is also affected by the hydrodynamic shear stress applied during the first 3. days of the differentiation stage. Even low shear applied continuously by side to side rocker agitation resulted in very low CM differentiation efficiency (cTnT. textless. 5%; MHC. textless. 2%). Simply by applying intermittent agitation during these 3. days followed by continuous agitation for the subsequent 9. days,CM differentiation efficiency can be substantially increased (cTNT: 65.73. ??. 10.73%; MHC: 59.73. ??. 9.17%). These yields are 38.3% and 39.3% higher (for cTnT and MHC respectively) than static culture control.During the hESC expansion phase,cells grew on continuously agitated rocker platform as pluripotent cell/MC aggregates (166??88??105??m2) achieving a cell concentration of 3.74??0.55??106cells/mL (18.89??2.82 fold expansion) in 7days. These aggregates were further differentiated into CMs using a WNT modulation differentiation protocol for the subsequent 12days on a rocking platform with an intermittent agitation regime during the first 3days. Collectively,the integrated MC rocker platform produced 190.5??58.8??106 CMs per run (31.75??9.74 CM/hESC seeded). The robustness of the system was demonstrated by using 2 cells lines,hESC (HES-3) and human induced pluripotent stem cell (hiPSC) IMR-90. The CM/MC aggregates formed extensive sarcomeres that exhibited cross-striations confirming cardiac ontogeny. Functionality of the CMs was demonstrated by monitoring the effect of inotropic drug,Isoproterenol on beating frequency.In conclusion,we have developed a simple robust and scalable platform that integrates both hESC expansion and CM differentiation in one unit process which is capable of meeting the need for large amounts of CMs. ?? 2014. View Publication