技术资料

Inactivation of the Pancreatic and Duodenal Homeobox 1 (PDX1) gene causes pancreatic agenesis,which places PDX1 high atop the regulatory network controlling development of this indispensable organ. However,little is known about the identity of PDX1 transcriptional targets. We simulated pancreatic development by differentiating human embryonic stem cells (hESCs) into early pancreatic progenitors and subjected this cell population to PDX1 chromatin immunoprecipitation sequencing (ChIP-seq). We identified more than 350 genes bound by PDX1,whose expression was upregulated on day 17 of differentiation. This group included known PDX1 targets and many genes not previously linked to pancreatic development. ChIP-seq also revealed PDX1 occupancy at hepatic genes. We hypothesized that simultaneous PDX1-driven activation of pancreatic and repression of hepatic programs underlie early divergence between pancreas and liver. In HepG2 cells and differentiating hESCs,we found that PDX1 binds and suppresses expression of endogenous liver genes. These findings rebrand PDX1 as a context-dependent transcriptional repressor and activator within the same cell type. View Publication

The incidence of cardiovascular disease represents a significant and growing health-care challenge to the developed and developing world. The ability of native heart muscle to regenerate in response to myocardial infarct is minimal. Tissue engineering and regenerative medicine approaches represent one promising response to this difficulty. Here,we present methods for the construction of a cell-seeded cardiac patch with the potential to promote regenerative outcomes in heart muscle with damage secondary to myocardial infarct. This method leverages iPS cells and a fibrin-based scaffold to create a simple and commercially viable tissue-engineered cardiac patch. Human-induced pluripotent stem cells (hiPSCs) can,in principle,be differentiated into cells of any lineage. However,most of the protocols used to generate hiPSC-derived endothelial cells (ECs) and cardiomyocytes (CMs) are unsatisfactory because the yield and phenotypic stability of the hiPSC-ECs are low,and the hiPSC-CMs are often purified via selection for expression of a promoter-reporter construct. In this chapter,we describe an hiPSC-EC differentiation protocol that generates large numbers of stable ECs and an hiPSC-CM differentiation protocol that does not require genetic manipulation,single-cell selection,or sorting with fluorescent dyes or other reagents. We also provide a simple but effective method that can be used to combine hiPSC-ECs and hiPSC-CMs with hiPSC-derived smooth muscle cells to engineer a contracting patch of cardiac cells. View Publication

There is ample evidence that the ubiquitin-proteasome system is an important regulator of transcription and its activity is necessary for maintaining pluripotency and promoting cellular reprogramming. Moreover,proteasome activity contributes to maintaining the open chromatin structure found in pluripotent stem cells,acting as a transcriptional inhibitor at specific gene loci generally associated with differentiation. The current study was designed to understand further the role of proteasome inhibition in reprogramming and its ability to modulate endogenous expression of pluripotency-related genes and induced pluripotent stem cells (iPSCs) colony formation. Herein,we demonstrate that acute combinatorial treatment with the proteasome inhibitors MG101 or MG132 and the histone deacetylase (HDAC) inhibitor valproic acid (VPA) increases gene expression of the pluripotency marker Oct3/4,and that MG101 alone is as effective as VPA in the induction of Oct3/4 mRNA expression in fibroblasts. Prolonged proteasome inhibition cyclically upregulates gene expression of Oct3/4 and Nanog,but reduces colony formation in the presence of the iPSC induction cocktail. In conclusion,our results demonstrate that the 26S proteasome is an essential modulator in the reprogramming process. Its inhibition enhances expression of pluripotency-related genes; however,efficient colony formation requires proteasome activity. Therefore,discovery of small molecules that increase proteasome activity might lead to more efficient cell reprogramming and generation of pluripotent cells. View Publication

Cardiac malformations and disease are the leading causes of death in the United States in live-born infants and adults,respectively. In both of these cases,a decrease in the number of functional cardiomyocytes often results in improper growth of heart tissue,wound healing complications,and poor tissue repair. The field of cardiac tissue engineering seeks to address these concerns by developing cardiac patches created from a variety of biomaterial scaffolds to be used in surgical repair of the heart. These scaffolds should be fully degradable biomaterial systems with tunable properties such that the materials can be altered to meet the needs of both in vitro culture (e.g. disease modeling) and in vivo application (e.g. cardiac patch). Current platforms do not utilize both structural anisotropy and proper cell-matrix contacts to promote functional cardiac phenotypes and thus there is still a need for critically sized scaffolds that mimic both the structural and adhesive properties of native tissue. To address this need,we have developed a silk-based scaffold platform containing cardiac tissue-derived extracellular matrix (cECM). These silk-cECM composite scaffolds have tunable architectures,degradation rates,and mechanical properties. Subcutaneous implantation in rats demonstrated that addition of the cECM to aligned silk scaffold led to 99% endogenous cell infiltration and promoted vascularization of a critically sized scaffold (10 × 5 × 2.5 mm) after 4 weeks in vivo. In vitro,silk-cECM scaffolds maintained the HL-1 atrial cardiomyocytes and human embryonic stem cell-derived cardiomyocytes and promoted a more functional phenotype in both cell types. This class of hybrid silk-cECM anisotropic scaffolds offers new opportunities for developing more physiologically relevant tissues for cardiac repair and disease modeling. View Publication

For diseases of the brain,the pig (Sus scrofa) is increasingly being used as a model organism that shares many anatomical and biological similarities with humans. We report that pig induced pluripotent stem cells (iPSC) can recapitulate events in early mammalian neural development. Pig iPSC line (POU5F1(high)/SSEA4(low)) had a higher potential to form neural rosettes (NR) containing neuroepithelial cells than either POU5F1(low)/SSEA4(low) or POU5F1(low)/SSEA4(high) lines. Thus,POU5F1 and SSEA4 pluripotency marker profiles in starting porcine iPSC populations can predict their propensity to form more robust NR populations in culture. The NR were isolated and expanded in vitro,retaining their NR morphology and neuroepithelial molecular properties. These cells expressed anterior central nervous system fate markers OTX2 and GBX2 through at least seven passages,and responded to retinoic acid,promoting a more posterior fate (HOXB4+,OTX2-,and GBX2-). These findings offer insight into pig iPSC development,which parallels the human iPSC in both anterior and posterior neural cell fates. These in vitro similarities in early neural differentiation processes support the use of pig iPSC and differentiated neural cells as a cell therapy in allogeneic porcine neural injury and degeneration models,providing relevant translational data for eventual human neural cell therapies. View Publication

Morpholino oligonucleotides (MO) are an innovative tool that provides a means for examining and modifying gene expression outcomes by antisense interaction with targeted RNA transcripts. The site-specific nature of their binding facilitates focused modulation to alter splice variant expression patterns. Here we describe the steric-blocking of human telomerase reverse transcriptase (hTERT) $$$$ and $$$$ splice variants using MO to examine cellular outcomes related to pluripotency and differentiation in human embryonic stem cells. View Publication

Nature Genetics 47,469 (2015). doi:10.1038/ng.3258 View Publication

The liver is the main organ responsible for the modification,clearance,and transformational toxicity of most xenobiotics owing to its abundance in cytochrome P450 (CYP450) enzymes. However,the scarcity and variability of primary hepatocytes currently limits their utility. Human pluripotent stem cells (hPSCs) represent an excellent source of differentiated hepatocytes; however,current protocols still produce fetal-like hepatocytes with limited mature function. Interestingly,fetal hepatocytes acquire mature CYP450 expression only postpartum,suggesting that nutritional cues may drive hepatic maturation. We show that vitamin K2 and lithocholic acid,a by-product of intestinal flora,activate pregnane X receptor (PXR) and subsequent CYP3A4 and CYP2C9 expression in hPSC-derived and isolated fetal hepatocytes. Differentiated cells produce albumin and apolipoprotein B100 at levels equivalent to primary human hepatocytes,while demonstrating an 8-fold induction of CYP450 activity in response to aryl hydrocarbon receptor (AhR) agonist omeprazole and a 10-fold induction in response to PXR agonist rifampicin. Flow cytometry showed that over 83% of cells were albumin and hepatocyte nuclear factor 4 alpha (HNF4α) positive,permitting high-content screening in a 96-well plate format. Analysis of 12 compounds showed an R(2) correlation of 0.94 between TC50 values obtained in stem cell-derived hepatocytes and primary cells,compared to 0.62 for HepG2 cells. Finally,stem cell-derived hepatocytes demonstrate all toxicological endpoints examined,including steatosis,apoptosis,and cholestasis,when exposed to nine known hepatotoxins. CONCLUSION: Our work provides fresh insights into liver development,suggesting that microbial-derived cues may drive the maturation of CYP450 enzymes postpartum. Addition of these cues results in the first functional,inducible,hPSC-derived hepatocyte for predictive toxicology. (Hepatology 2015). View Publication

Recent breakthroughs in 3-dimensional (3D) organoid cultures for many organ systems have led to new physiologically complex in vitro models to study human development and disease. Here,we report the step-wise differentiation of human pluripotent stem cells (hPSCs) (embryonic and induced) into lung organoids. By manipulating developmental signaling pathways hPSCs generate ventral-anterior foregut spheroids,which are then expanded into human lung organoids (HLOs). HLOs consist of epithelial and mesenchymal compartments of the lung,organized with structural features similar to the native lung. HLOs possess upper airway-like epithelium with basal cells and immature ciliated cells surrounded by smooth muscle and myofibroblasts as well as an alveolar-like domain with appropriate cell types. Using RNA-sequencing,we show that HLOs are remarkably similar to human fetal lung based on global transcriptional profiles,suggesting that HLOs are an excellent model to study human lung development,maturation and disease. View Publication

The generation of personalized induced pluripotent stem cells (iPSCs) followed by targeted genome editing provides an opportunity for developing customized effective cellular therapies for genetic disorders. However,it is critical to ascertain whether edited iPSCs harbor unfavorable genomic variations before their clinical application. To examine the mutation status of the edited iPSC genome and trace the origin of possible mutations at different steps,we have generated virus-free iPSCs from amniotic cells carrying homozygous point mutations in beta-hemoglobin gene (HBB) that cause severe beta-thalassemia (beta-Thal),corrected the mutations in both HBB alleles by zinc finger nuclease-aided gene targeting,and obtained the final HBB gene-corrected iPSCs by excising the exogenous drug resistance gene with Cre recombinase. Through comparative genomic hybridization and whole-exome sequencing,we uncovered seven copy number variations,five small insertions/deletions,and 64 single nucleotide variations (SNVs) in beta-Thal iPSCs before the gene targeting step and found a single small copy number variation,19 insertions/deletions,and 340 single nucleotide variations in the final gene-corrected beta-Thal iPSCs. Our data revealed that substantial but different genomic variations occurred at factor-induced somatic cell reprogramming and zinc finger nuclease-aided gene targeting steps,suggesting that stringent genomic monitoring and selection are needed both at the time of iPSC derivation and after gene targeting. View Publication

Neurodegenerative diseases are characterized by chronic and progressive structural or functional loss of neurons. Limitations related to the animal models of these human diseases have impeded the development of effective drugs. This emphasizes the need to establish disease models using human-derived cells. The discovery of induced pluripotent stem cell (iPSC) technology has provided novel opportunities in disease modeling,drug development,screening,and the potential for patient-matched" cellular therapies in neurodegenerative diseases. In this study� View Publication

Emerging evidence shows that glioblastoma multiforme (GBM) originates from cancer stem cells (CSCs). Characterization of CSC-specific signalling pathways would help identify new therapeutic targets and perhaps lead to the development of more efficient therapies selectively targeting CSCs. Here; we successfully dedifferentiated two patient-derived GBM cell lines into CSC-like cells (induced glioma stem cells,iGSCs) through expression of Oct4,Sox2 and Nanog transcription factors. Transformed cells exhibited significant suppression of epidermal growth factor receptor and its downstream pathways. Compared with parental GBM cells,iGSCs formed large neurospheres even in the absence of exogenous mitogens; they exhibited significant sensitivity to salinomycin and chemoresistance to temozolomide. Further characterization of iGSCs revealed induction of NOTCH1 and Wnt/β-catenin signalling and expression of CD133,CD44 and ALDH1A1. Our results indicate that iGSCs may help us understand CSC physiology and lead to development of potential therapeutic interventions aimed at differentiating tumour cells to render them more sensitive to chemotherapy or other standard agents. View Publication