Scientific Resources

BACKGROUND Human (h) embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) serve as a potential unlimited ex vivo source of cardiomyocytes (CMs). However,a well-accepted roadblock has been their immature phenotype. hESC/iPSC-derived ventricular (v) CMs and their engineered cardiac microtissues (hvCMTs) similarly displayed positive chronotropic but null inotropic responses to $\$-adrenergic stimulation. Given that phospholamban (PLB) is robustly present in adult but poorly expressed in hESC/iPSC-vCMs and its defined biological role in $\$-adrenergic signaling,we investigated the functional consequences of PLB expression in hESC/iPSC-vCMs and hvCMTs. METHODS AND RESULTS First,we confirmed that PLB protein was differentially expressed in hESC (HES2,H9)- and iPSC-derived and adult vCMs. We then transduced hES2-vCMs with the recombinant adenoviruses (Ad) Ad-PLB or Ad-S16E-PLB to overexpress wild-type PLB or the pseudophosphorylated point-mutated variant,respectively. As anticipated from the inhibitory effect of unphosphorylated PLB on sarco/endoplasmic reticulum Ca2+-ATPase,Ad-PLB transduction significantly attenuated electrically evoked Ca2+ transient amplitude and prolonged the 50% decay time. Importantly,Ad-PLB-transduced hES2-vCMs uniquely responded to isoproterenol. Ad-S16E-PLB-transduced hES2-vCMs displayed an intermediate phenotype. The same trends were observed with H9- and iPSC-vCMs. Directionally,similar results were also seen with Ad-PLB-transduced and Ad-S16E-transduced hvCMTs. However,Ad-PLB altered neither the global transcriptome nor ICa,L,implicating a PLB-specific effect. CONCLUSIONS Engineered upregulation of PLB expression in hESC/iPSC-vCMs restores a positive inotropic response to $\$-adrenergic stimulation. These results not only provide a better mechanistic understanding of the immaturity of hESC/iPSC-vCMs but will also lead to improved disease models and transplantable prototypes with adult-like physiological responses. View Publication

Human induced pluripotent stem cells (hiPSCs) have potential applications in cell replacement therapy and regenerative medicine. However,limited information is available regarding the immunologic features of iPSCs. In this study,expression of MHC and T cell co-stimulatory molecules in hiPSCs,and the effects on activation,proliferation and cytokine production in allogeneic human peripheral blood mononuclear cells were examined. We found that no-integrate hiPSCs had no MHC-II and T cell co-stimulatory molecules expressions but had moderate level of MHC-I and HLA-G expressions. In contrast to human skin fibroblasts (HSFs) which significantly induced allogeneic T cell activation and proliferation,hiPSCs failed to induce allogeneic CD45+ lymphocyte and CD8+ T cell activation and proliferation but could induce a low level of allogeneic CD4+ T cell proliferation. Unlike HSFs which induced allogeneic lymphocytes to produce high levels of IFN-γ,TNF-α and IL-17,hiPSCs only induced allogeneic lymphocytes to produce IL-2 and IL-10,and promote IL-10-secreting regulatory T cell (Treg) generation. Our study suggests that the integration-free hiPSCs had low or negligible immunogenicity,which may result from their induction of IL-10-secreting Treg. View Publication

Rapid technological advances have made the acquisition of large numbers of spectra not only feasible,but also routine. As a result,a significant research effort is focused on semi-automated and fully automated spectral processing techniques. However,the need to provide initial estimates of the number of peaks,their band shapes,and the initial parameters of these bands presents an obstacle to the full automation of peak fitting and its incorporation into fully automated spectral-preprocessing workflows. Moreover,the sensitivity of peak-fit routines to initial parameter settings and the resultant variations in solution quality further impede user-free operation. We have developed a technique to perform fully automated peak fitting on fully automated preconditioned spectra-specifically,baseline-corrected and smoothed spectra that are free of cosmic-ray-induced spikes. Briefly,the tallest peak in a spectrum is located and a Gaussian peak-fit is performed. The fitted peak is then subtracted from the spectrum,and the procedure is repeated until the entire spectrum has been processed. In second and third passes,all the peaks in the spectrum are fitted concurrently,but are fitted to a Pearson Type VII model using the parameters for the model established in the prior pass. The technique is applied to a synthetic spectrum with several peaks,some of which have substantial overlap,to test the ability of the method to recover the correct number of peaks,their true shape,and their appropriate parameters. Finally the method is tested on measured Raman spectra collected from human embryonic stem cells and samples of red blood cells. View Publication

A simple,scalable,and reproducible technology that allows direct formation of large numbers of homogeneous and synchronized embryoid bodies (EBs) of defined sizes from dissociated human induced pluripotent stem cells (hiPSCs) was developed. Non-cell-adhesive hydrogels were used to create round-bottom microwells to host dissociated hiPSCs. No Rho-associated kinase inhibitor (ROCK-i),or centrifugation was needed and the side effects of ROCK-i can be avoided. The key requirement for the successful EB formation in addition to the non-cell-adhesive round-bottom microwells is the input cell density per microwell. Too few or too many cells loaded into the microwells will compromise the EB formation process. In parallel,we have tested our microwell-based system for homogeneous hEB formation from dissociated human embryonic stem cells (hESCs). Successful production of homogeneous hEBs from dissociated hESCs in the absence of ROCK-i and centrifugation was achieved within an optimal range of input cell density per microwell. Both the hiPSC- and hESC-derived hEBs expressed key proteins characteristic of all the three developmental germ layers,confirming their EB identity. This novel EB production technology may represent a versatile platform for the production of homogeneous EBs from dissociated human pluripotent stem cells (hPSCs). View Publication

Human induced pluripotent stem cells (hiPSCs) can be generated with lentiviral-based reprogramming methodologies. However,traces of potentially oncogenic genes remaining in actively transcribed regions of the genome,limit their potential for use in human therapeutic applications. Additionally,non-human antigens derived from stem cell reprogramming or differentiation into therapeutically relevant derivatives preclude these hiPSCs from being used in a human clinical context. In this video,we present a procedure for reprogramming and analyzing factor-free hiPSCs free of exogenous transgenes. These hiPSCs then can be analyzed for gene expression abnormalities in the specific intron containing the lentivirus. This analysis may be conducted using sensitive quantitative polymerase chain reaction (PCR),which has an advantage over less sensitive techniques previously used to detect gene expression differences. Full conversion into clinical-grade good manufacturing practice (GMP) conditions,allows human clinical relevance. Our protocol offers another methodology--provided that current safe-harbor criteria will expand and include factor-free characterized hiPSC-based derivatives for human therapeutic applications--for deriving GMP-grade hiPSCs,which should eliminate any immunogenicity risk due to non-human antigens. This protocol is broadly applicable to lentiviral reprogrammed cells of any type and provides a reproducible method for converting reprogrammed cells into GMP-grade conditions. View Publication

Human embryonic stem cells (hESCs) are pluripotent and capable of generating new $\$-cells,but current in vitro differentiation protocols generally fail to produce mature,glucose-responsive,unihormonal $\$-cells. Instead,these methods tend to produce immature polyhormonal endocrine cells which mature in vivo into glucagon-positive $\$-cells. PAX4 is an established transcription factor in $\$-cell development and function,and is capable of converting glucagon-positive cells to insulin-positive cells in mice. Work in human and mouse ESCs has shown that constitutive PAX4 expression promotes the development of insulin-positive cells,but whether acute PAX4 expression is sufficient to guide specific endocrine cell fates has not been addressed in hESCs. In this study,we applied recombinant adenovirus to ectopically express human PAX4 in hESC-derived pancreatic progenitors,with the aim of influencing the endocrine developmental cascade away from polyhormonal cells toward unihormonal insulin-positive cells. Gene delivery to pancreatic progenitors was efficient and dose-dependent. By the end of in vitro differentiation,PAX4 reduced ARX expression,but only the high dose tested significantly reduced glucagon release. Single cell analysis revealed that while PAX4 did not alter the proportion of endocrine cells,it did reduce the number of glucagon-positive cells and increased the number of unihormonal insulin-positive cells. These data suggest that acute PAX4 overexpression can reduce expression of ARX and glucagon resulting in improved numbers of unihormonal insulin-positive cells. 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

As cyclin-dependent kinases (CDKs) regulate cell cycle progression and RNA transcription,CDKs are attractive targets for creating cancer cell treatments. In this study we investigated the effects of the small molecular agent NU6140 (inhibits CDK2 and cyclin A interaction) on human embryonic stem (hES) cells and embryonal carcinoma-derived (hEC) cells via the expression of transcription factors responsible for pluripotency. A multiparameter flow cytometric method was used to follow changes in the expression of NANOG,OCT4,and SOX2 together in single cells. Both hES and hEC cells responded to NU6140 treatment by induced apoptosis and a decreased expression of NANOG,OCT4,and SOX2 in surviving cells. A higher sensitivity to NU6140 application in hES than hEC cells was detected. NU6140 treatment arrested hES and hEC cells in the G2 phase and inhibited entry into the M phase as evidenced by no significant increase in histone 3 phosphorylation. When embryoid bodies (EBs) formed from NU6104 treated hES cells were compared to EBs from untreated hES cells differences in ectodermal,endodermal,and mesodermal lineages were found. The results of this study highlight the importance of CDK2 activity in maintaining pluripotency of hES and hEC cells and in differentiation of hES cells. View Publication

Human sensory neurons are inaccessible for functional examination,and thus little is known about the mechanisms mediating touch sensation in humans. Here we demonstrate that the mechanosensitivity of human embryonic stem (hES) cell-derived touch receptors depends on PIEZO2. To recapitulate sensory neuron development in vitro,we established a multistep differentiation protocol and generated sensory neurons via the intermediate production of neural crest cells derived from hES cells or human induced pluripotent stem (hiPS) cells. The generated neurons express a distinct set of touch receptor-specific genes and convert mechanical stimuli into electrical signals,their most salient characteristic in vivo. Strikingly,mechanosensitivity is lost after CRISPR/Cas9-mediated PIEZO2 gene deletion. Our work establishes a model system that resembles human touch receptors,which may facilitate mechanistic analysis of other sensory subtypes and provide insight into developmental programs underlying sensory neuron diversity. View Publication

Neural crest cells (NCCs) are an embryonic migratory cell population with the ability to differentiate into a wide variety of cell types that contribute to the craniofacial skeleton,cornea,peripheral nervous system,and skin pigmentation. This ability suggests the promising role of NCCs as a source for cell-based therapy. Although several methods have been used to induce human NCCs (hNCCs) from human pluripotent stem cells (hPSCs),such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs),further modifications are required to improve the robustness,efficacy,and simplicity of these methods. Chemically defined medium (CDM) was used as the basal medium in the induction and maintenance steps. By optimizing the culture conditions,the combination of the GSK3β inhibitor and TGFβ inhibitor with a minimum growth factor (insulin) very efficiently induced hNCCs (70-80%) from hPSCs. The induced hNCCs expressed cranial NCC-related genes and stably proliferated in CDM supplemented with EGF and FGF2 up to at least 10 passages without changes being observed in the major gene expression profiles. Differentiation properties were confirmed for peripheral neurons,glia,melanocytes,and corneal endothelial cells. In addition,cells with differentiation characteristics similar to multipotent mesenchymal stromal cells (MSCs) were induced from hNCCs using CDM specific for human MSCs. Our simple and robust induction protocol using small molecule compounds with defined media enabled the generation of hNCCs as an intermediate material producing terminally differentiated cells for cell-based innovative medicine. View Publication

To harness the potential of human pluripotent stem cells (hPSCs),an abundant supply of their progenies is required. Here,hPSC expansion as matrix-independent aggregates in suspension culture was combined with cardiomyogenic differentiation using chemical Wnt pathway modulators. A multiwell screen was scaled up to stirred Erlenmeyer flasks and subsequently to tank bioreactors,applying controlled feeding strategies (batch and cyclic perfusion). Cardiomyogenesis was sensitive to the GSK3 inhibitor CHIR99021 concentration,whereas the aggregate size was no prevailing factor across culture platforms. However,in bioreactors,the pattern of aggregate formation in the expansion phase dominated subsequent differentiation. Global profiling revealed a culture-dependent expression of BMP agonists/antagonists,suggesting their decisive role in cell-fate determination. Furthermore,metallothionein was discovered as a potentially stress-related marker in hPSCs. In 100 ml bioreactors,the production of 40 million predominantly ventricular-like cardiomyocytes (up to 85% purity) was enabled that were directly applicable to bioartificial cardiac tissue formation. View Publication

The recent identification of hemogenic endothelium (HE) in human pluripotent stem cell (hPSC) cultures presents opportunities to investigate signaling pathways that are essential for blood development from endothelium and provides an exploratory platform for de novo generation of hematopoietic stem cells (HSCs). However,the use of poorly defined human or animal components limits the utility of the current differentiation systems for studying specific growth factors required for HE induction and manufacturing clinical-grade therapeutic blood cells. Here,we identified chemically defined conditions required to produce HE from hPSCs growing in Essential 8 (E8) medium and showed that Tenascin C (TenC),an extracellular matrix protein associated with HSC niches,strongly promotes HE and definitive hematopoiesis in this system. hPSCs differentiated in chemically defined conditions undergo stages of development similar to those previously described in hPSCs cocultured on OP9 feeders,including the formation of VE-Cadherin(+)CD73(-)CD235a/CD43(-) HE and hematopoietic progenitors with myeloid and T lymphoid potential. View Publication