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Mesenchymal stem cells (MSCs) possess tumor-tropic properties and consequently have been used to deliver therapeutic agents for cancer treatment. Their potential in cancer therapy highlights the need for a consistent and renewable source for the production of uniform human MSCs suitable for clinical applications. In this study,we seek to investigate whether human embryonic stem cells can be used as a cell source to fulfill this goal. We generated MSC-like cells from two human embryonic stem cell lines,HuES9 and H1,and observed that MSC-like cells derived from human embryonic stem cells were able to migrate into human glioma intracranial xenografts after being injected into the cerebral hemisphere contralateral to the tumor inoculation site. We engineered these cells with baculoviral and lentiviral vectors,respectively,for transient and stable expression of the herpes simplex virus thymidine kinase gene. In tumor-bearing mice the engineered MSC-like cells were capable of inhibiting tumor growth and prolonging survival in the presence of ganciclovir after they were injected either directly into the xenografts or into the opposite hemisphere. Our findings suggest that human embryonic stem cell-derived MSCs may be a viable and attractive alternative for large-scale derivation of targeting vehicles for cancer therapy. View Publication

: Induced pluripotent stem cells (iPSCs) offer an unlimited resource of cells to be used for the study of underlying molecular biology of disease,therapeutic drug screening,and transplant-based regenerative medicine. However,methods for the directed differentiation of skeletal muscle for these purposes remain scarce and incomplete. Here,we present a novel,small molecule-based protocol for the generation of multinucleated skeletal myotubes using eight independent iPSC lines. Through combinatorial inhibition of phosphoinositide 3-kinase (PI3K) and glycogen synthase kinase 3β (GSK3β) with addition of bone morphogenic protein 4 (BMP4) and fibroblast growth factor 2 (FGF2),we report up to 64% conversion of iPSCs into the myogenic program by day 36 as indicated by MYOG+ cell populations. These cells began to exhibit spontaneous contractions as early as 34 days in vitro in the presence of a serum-free medium formulation. We used this protocol to obtain iPSC-derived muscle cells from frontotemporal dementia (FTD) patients harboring C9orf72 hexanucleotide repeat expansions (rGGGGCC),sporadic FTD,and unaffected controls. iPSCs derived from rGGGGCC carriers contained RNA foci but did not vary in differentiation efficiency when compared to unaffected controls nor display mislocalized TDP-43 after as many as 120 days in vitro. This study presents a rapid,efficient,and transgene-free method for generating multinucleated skeletal myotubes from iPSCs and a resource for further modeling the role of skeletal muscle in amyotrophic lateral sclerosis and other motor neuron diseases. SIGNIFICANCE Protocols to produce skeletal myotubes for disease modeling or therapy are scarce and incomplete. The present study efficiently generates functional skeletal myotubes from human induced pluripotent stem cells using a small molecule-based approach. Using this strategy,terminal myogenic induction of up to 64% in 36 days and spontaneously contractile myotubes within 34 days were achieved. Myotubes derived from patients carrying the C9orf72 repeat expansion show no change in differentiation efficiency and normal TDP-43 localization after as many as 120 days in vitro when compared to unaffected controls. This study provides an efficient,novel protocol for the generation of skeletal myotubes from human induced pluripotent stem cells that may serve as a valuable tool in drug discovery and modeling of musculoskeletal and neuromuscular diseases. View Publication

Hepatocyte-like cells (HLCs) are derived from human pluripotent stem cells (hPSCs) in vitro,but differentiation protocols commonly give rise to a heterogeneous mixture of cells. This variability confounds the evaluation of in vitro functional assays performed using HLCs. Increased differentiation efficiency and more accurate approximation of the in vivo hepatocyte gene expression profile would improve the utility of hPSCs. Towards this goal,we demonstrate the purification of a subpopulation of functional HLCs using the hepatocyte surface marker asialoglycoprotein receptor 1 (ASGR1). We analyzed the expression profile of ASGR1-positive cells by microarray,and tested their ability to perform mature hepatocyte functions (albumin and urea secretion,cytochrome activity). By these measures,ASGR1-positive HLCs are enriched for the gene expression profile and functional characteristics of primary hepatocytes compared with unsorted HLCs. We have demonstrated that ASGR1-positive sorting isolates a functional subpopulation of HLCs from among the heterogeneous cellular population produced by directed differentiation. View Publication

Introduction Appropriate neural patterning of human induced pluripotent stem cells (hiPSCs) is critical to generate specific neural cells/tissues and even mini-brains that are physiologically relevant to model neurological diseases. However,the capacity of signaling factors that regulate 3-D neural tissue patterning in vitro and differential responses of the resulting neural populations to various biomolecules have not yet been fully understood. Methods By tuning neural patterning of hiPSCs with small molecules targeting sonic hedgehog (SHH) signaling,this study generated different 3-D neuronal cultures that were mainly comprised of either cortical glutamatergic neurons or motor neurons. Results Abundant glutamatergic neurons were observed following the treatment with an antagonist of SHH signaling,cyclopamine,while Islet-1 and HB9-expressing motor neurons were enriched by an SHH agonist,purmorphamine. In neurons derived with different neural patterning factors,whole-cell patch clamp recordings showed similar voltage-gated Na+/K+ currents,depolarization-evoked action potentials and spontaneous excitatory post-synaptic currents. Moreover,these different neuronal populations exhibited differential responses to three classes of biomolecules,including (1) matrix metalloproteinase inhibitors that affect extracellular matrix remodeling; (2) N-methyl-D-aspartate that induces general neurotoxicity; and (3) amyloid ?? (1???42) oligomers that cause neuronal subtype-specific neurotoxicity. Conclusions This study should advance our understanding of hiPSC self-organization and neural tissue development and provide a transformative approach to establish 3-D models for neurological disease modeling and drug discovery. Statement of Significance Appropriate neural patterning of human induced pluripotent stem cells (hiPSCs) is critical to generate specific neural cells,tissues and even mini-brains that are physiologically relevant to model neurological diseases. However,the capability of sonic hedgehog-related small molecules to tune different neuronal subtypes in 3-D differentiation from hiPSCs and the differential cellular responses of region-specific neuronal subtypes to various biomolecules have not been fully investigated. By tuning neural patterning of hiPSCs with small molecules targeting sonic hedgehog signaling,this study provides knowledge on the differential susceptibility of region-specific neuronal subtypes derived from hiPSCs to different biomolecules in extracellular matrix remodeling and neurotoxicity. The findings are significant for understanding 3-D neural patterning of hiPSCs for the applications in brain organoid formation,neurological disease modeling,and drug discovery. View Publication

Human induced pluripotent stem cells (hiPSCs) secrete essential autocrine factors that are removed along with toxic metabolites when the growth medium is exchanged daily. In this study,after determining the minimum inhibitory level of lactic acid for hiPSCs,a medium refining system was constructed by which toxic metabolites were removed from used culture medium and autocrine factors as well as other growth factors were recycled. Specifically,about 87 % of the basic fibroblast growth factor and 80 % of transforming growth factor beta 1 were retained in the refined medium after dialysis. The refined medium efficiently potentiated the proliferation of hiPS cells in adherent culture. When the refining system was used to refresh medium in suspension culture,a final cell density of (1.1 ± 0.1) × 10(6) cells mL(-1) was obtained,with 99.5 ± 0.2 % OCT 3/4 and 78.3 ± 1.1 % TRA-1-60 expression,on day 4 of culture. These levels of expression were similar to those observed in the conventional suspension culture. With this method,culture medium refinement by dialysis was established to remove toxic metabolites,recycle autocrine factors as well as other growth factors,and reduce the use of macromolecules for the expansion of hiPSCs in suspension culture. View Publication

The past two decades have witnessed significant strides in leukemia therapies through approval of therapeutic inhibitors targeting oncogene-driving dysregulated tyrosine kinase activities and key epigenetic and apoptosis regulators. Although these drugs have brought about complete remission in the majority of patients,many patients face relapse or have refractory disease. The main factor contributing to relapse is the presence of a small subpopulation of dormant drug-resistant leukemia cells that possess stem cell features (termed as leukemia stem cells or LSCs). Thus,overcoming drug resistance and targeting LSCs remain major challenges for curative treatment of human leukemia. Chronic myeloid leukemia (CML) is a good example,with rare,propagating LSCs and drug-resistant cells that cannot be eradicated by BCR-ABL-directed tyrosine kinase inhibitor (TKI) monotherapy and that are responsible for disease relapse/progression. Therefore,it is imperative to identify key players in regulating BCR-ABL1-dependent and independent drug-resistance mechanisms,and their key pathways,so that CML LSCs can be selectively targeted or sensitized to TKIs. Here,we describe several easily adaptable gene knockdown approaches in CD34+ CML stem/progenitor cells that can be used to investigate the biological properties of LSCs and molecular effects of genes of interest (GOI),which can be further explored as therapeutic modalities against LSCs in the context of human leukemia. View Publication

Cord blood (CB) cells are a useful source of hematopoietic cells for transplantation. The hematopoietic activities of CB cells are different from those of bone marrow and peripheral blood (PB) cells. Platelet recovery is significantly slower after transplantation with CB cells than with cells from other sources. However,the cellular mechanisms underlying these differences have not been elucidated. We compared the surface marker expression profiles of PB and CB hematopoietic cells. We focused on two surface markers of hematopoietic cell immaturity,i.e.,CD34 and AC133. In addition to differences in surface marker expression,the PB and CB cells showed nonidentical differentiation pathways from AC133(+)CD34(+) (immature) hematopoietic cells to terminally differentiated cells. The majority of the AC133(+)CD34(+) PB cells initially lost AC133 expression and eventually became AC133(-)CD34(-) cells. In contrast,the AC133(+)CD34(+) CB cells did not go through the intermediate AC133(-)CD34(+) stage and lost both markers simultaneously. Meanwhile,the vast majority of megakaryocyte progenitors were of the AC133(-)CD34(+) phenotype. We conclude that the delayed recovery of platelets after CB transplantation is due to both subpopulation distribution and the process of differentiation from AC133(+)CD34(+) cells. View Publication

Human (h) induced pluripotent stem cells (iPSCs) are a potentially abundant source of blood cells,but how best to select iPSC clones suitable for this purpose from among the many clones that can be simultaneously established from an identical source is not clear. Using an in vitro culture system yielding a hematopoietic niche that concentrates hematopoietic progenitors,we show that the pattern of c-MYC reactivation after reprogramming influences platelet generation from hiPSCs. During differentiation,reduction of c-MYC expression after initial reactivation of c-MYC expression in selected hiPSC clones was associated with more efficient in vitro generation of CD41a(+)CD42b(+) platelets. This effect was recapitulated in virus integration-free hiPSCs using a doxycycline-controlled c-MYC expression vector. In vivo imaging revealed that these CD42b(+) platelets were present in thrombi after laser-induced vessel wall injury. In contrast,sustained and excessive c-MYC expression in megakaryocytes was accompanied by increased p14 (ARF) and p16 (INK4A) expression,decreased GATA1 expression,and impaired production of functional platelets. These findings suggest that the pattern of c-MYC expression,particularly its later decline,is key to producing functional platelets from selected iPSC clones. View Publication

AIM: Dendritic cell (DC)-based vaccines are designed to exploit the intrinsic capacity of these highly effective antigen presenting cells to prime and boost antigen-specific T-cell immune responses. Successful development of DC-based vaccines will be dependent on the ability to utilize and harness the full potential of these potent immune stimulatory cells. Recent advances to generate DCs derived from human embryonic stem cells (hESCs) that are suitable for clinical use represent an alternative strategy from conventional approaches of using patient-specific DCs. Although the differentiation of hESC-derived DCs in serum-free defined conditions has been established,the stimulatory potential of these hESC-derived DCs have not been fully evaluated. METHODS: hESC-derived DCs were differentiated in serum-free defined culture conditions. The delivery of antigen into hESC-derived DCs was investigated using mRNA transfection and replication-deficient adenoviral vector transduction. hESC-derived DCs modified with antigen were evaluated for their capacity to stimulate antigen-specific T-cell responses with known HLA matching. Since IL-12 is a key cytokine that drives T-cell function,further enhancement of DC potency was evaluated by transfecting mRNA encoding the IL-12p70 protein into hESC-derived DCs. RESULTS: The transfection of mRNA into hESC-derived DCs was effective for heterologous protein expression. The efficiency of adenoviral vector transduction into hESC-derived DCs was poor. These mRNA-transfected DCs were capable of stimulating human telomerase reverse transcriptase antigen-specific T cells composed of varying degrees of HLA matching. In addition,we observed the transfection of mRNA encoding IL-12p70 enhanced the T-cell stimulation potency of hESC-derived DCs. CONCLUSION: These data provide support for the development and modification of hESC-derived DCs with mRNA as a potential strategy for the induction of T-cell-mediated immunity. View Publication

Efficient approaches for the precise genetic engineering of human pluripotent stem cells (hPSCs) can enhance both basic and applied stem cell research. Adeno- associated virus (AAV) vectors are of particular interest for their capacity to mediate efficient gene delivery to and gene targeting in various cells. However,natural AAV serotypes offer only modest transduction of human embryonic and induced pluripotent stem cells (hESCs and hiPSCs),which limits their utility for efficiently manipulating the hPSC genome. Directed evolution is a powerful means to generate viral vectors with novel capabilities,and we have applied this approach to create a novel AAV variant with high gene delivery efficiencies (˜50%) to hPSCs,which are importantly accompanied by a considerable increase in gene-targeting frequencies,up to 0.12%. While this level is likely sufficient for numerous applications,we also show that the gene-targeting efficiency mediated by an evolved AAV variant can be further enhanced (textgreater1%) in the presence of targeted double- stranded breaks (DSBs) generated by the co-delivery of artificial zinc finger nucleases (ZFNs). Thus,this study demonstrates that under appropriate selective pressures,AAV vectors can be created to mediate efficient gene targeting in hPSCs,alone or in the presence of ZFN- mediated double-stranded DNA breaks. View Publication

The advance in stem cell research relies largely on the efficiency and biocompatibility of technologies used to manipulate stem cells. In our previous study,we had designed an amphipathic peptide RV24 that can deliver proteins into cancer cell lines efficiently without significant side effects. Encouraged by this observation,we moved forward to test whether RV24 could be used to deliver proteins into human embryonic stem cells and human induced pluripotent stem cells. RV24 successfully mediated protein delivery into these pluripotent stem cells,as well as their derivatives including neural stem cells and dendritic cells. Based on NMR studies and particle surface charge measurements,we proposed that hydrophobic domain of RV24 interacts with ??-sheet structures of the proteins,followed by formation of peptide cage" to facilitate delivery across cellular membrane. These findings suggest the feasibility of using amphipathic peptide to deliver functional proteins intracellularly for stem cell research. ?? 2012 Elsevier Inc." View Publication

A prerequisite for the realization of human pluripotent stem cell (hPSC) therapies is the development of bioprocesses for generating clinically relevant quantities of undifferentiated hPSCs and their derivatives under xeno-free conditions. Microcarrier stirred-suspension bioreactors are an appealing modality for the scalable expansion and directed differentiation of hPSCs. Comparative analyses of commercially available microcarriers clearly show the need for developing synthetic substrates supporting the adhesion and growth of hPSCs in three-dimensional cultures under agitation-induced shear. Moreover,the low seeding efficiencies during microcarrier loading with hPSC clusters poses a significant process bottleneck. To that end,a novel protocol was developed increasing hPSC seeding efficiency from 30% to over 80% and substantially shortening the duration of microcarrier loading. Importantly,this method was combined with the engineering of polystyrene microcarriers by surface conjugation of a vitronectin-derived peptide,which was previously shown to support the growth of human embryonic stem cells. Cells proliferated on peptide-conjugated beads in static culture but widespread detachment was observed after exposure to stirring. This prompted additional treatment of the microcarriers with a synthetic polymer commonly used to enhance cell adhesion. hPSCs were successfully cultivated on these microcarriers in stirred suspension vessels for multiple consecutive passages with attachment efficiencies close to 40%. Cultured cells exhibited on average a 24-fold increase in concentration per 6-day passage,over 85% viability,and maintained a normal karyotype and the expression of pluripotency markers such as Nanog,Oct4,and SSEA4. When subjected to spontaneous differentiation in embryoid body cultures or directed differentiation to the three embryonic germ layers,the cells adopted respective fates displaying relevant markers. Lastly,engineered microcarriers were successfully utilized for the expansion and differentiation of hPSCs to mesoderm progeny in stirred suspension vessels. Hence,we demonstrate a strategy for the facile engineering of xeno-free microcarriers for stirred-suspension cultivation of hPSCs. Our findings support the use of microcarrier bioreactors for the scalable,xeno-free propagation and differentiation of human stem cells intended for therapies. View Publication