Scientific Resources

The development of dengue antivirals and vaccine has been hampered by the incomplete understanding of molecular mechanisms of dengue virus (DENV) infection and pathology,partly due to the limited suitable cell culture or animal models that can capture the comprehensive cellular changes induced by DENV. In this study,we differentiated human pluripotent stem cells (hPSCs) into hepatocytes,one of the target cells of DENV,to investigate various aspects of DENV-hepatocyte interaction. hPSC-derived hepatocyte-like cells (HLCs) supported persistent and productive DENV infection. The activation of interferon pathways by DENV protected bystander cells from infection and protected the infected cells from massive apoptosis. Furthermore,DENV infection activated the NF-$$B pathway,which led to production of proinflammatory cytokines and downregulated many liver-specific genes such as albumin and coagulation factor V. Our study demonstrates the utility of hPSC-derived hepatocytes as an in vitro model for DENV infection and reveals important aspects of DENV-host interactions. View Publication

BACKGROUND Immune activation predicts morbidity during HCV and HIV infection,though mechanisms underlying immune activation are unclear. Plasma autotaxin and its enzymatic product,lysophosphatidic-acid (LPA),are elevated during HCV infection,and LPA activates immunocytes,but whether this contributes to immune activation is unknown. METHODS We evaluated plasma autotaxin,IL-6,sCD14,sCD163,and Mac2-Binding Protein (Mac2BP) during HCV,HIV and HCV-HIV infection,and in uninfected controls,before and after HIV ART and IFN-free HCV therapy. RESULTS We observed greater plasma autotaxin levels in HCV and HCV-HIV-infected compared to uninfected participants,primarily those with higher AST/PLT ratio index. Autotaxin levels correlated with IL-6,sCD14,sCD163,Mac2BP,and LPA in HCV-infected,and with Mac2BP in HCV-HIV-infected participants,while in HIV infection sCD14 correlated with Mac2BP. Autotaxin,LPA and sCD14 levels normalized,while sCD163 and Mac2BP levels partially normalized within 6 months of starting IFN-free HCV therapy. sCD163 and IL-6 levels normalized within 6 months of starting HIV ART. In vitro,LPA activated monocytes. CONCLUSION These data indicate elevated autotaxin levels and soluble markers of immune activation during HCV infection are partially reversible within 6 months of IFN-free HCV treatment,and autotaxin may be causally linked to immune activation during HCV and HCV-HIV infection. View Publication

The ability to rationally target disease-causing mutations has been made possible with programmable nucleases with the CRISPR/Cas9 system representing a facile platform for individualized gene-based medicine. In this study we employed footprint free reprogramming of fibroblasts from a patient with mutations to the Fanconi anemia I (FANCI) gene to generate induced pluripotent stem cells (iPSC). This process was accomplished without gene complementation and the resultant iPSC were able to be gene corrected in a robust manner using the Cas9 nickase. The self-renewing iPSC that were maintained under feeder free conditions were differentiated into cells with characteristics of definitive hematopoiesis. This defined and highly efficient procedure employed small molecule modulation of the hematopoietic differentiation pathway and a vascular induction technique to generate hematopoietic progenitors. In sum,our results demonstrate the ability to induce patient derived FA cells to pluripotency for patient specific therapeutic cell derivation. View Publication

The U1 small nuclear (sn)RNA (U1) is a multifunctional ncRNA,known for its pivotal role in pre-mRNA splicing and regulation of RNA 3' end processing events. We recently demonstrated that a new class of human U1-like snRNAs,the variant (v)U1 snRNAs (vU1s),also participate in pre-mRNA processing events. In this study,we show that several human vU1 genes are specifically upregulated in stem cells and participate in the regulation of cell fate decisions. Significantly,ectopic expression of vU1 genes in human skin fibroblasts leads to increases in levels of key pluripotent stem cell mRNA markers,including NANOG and SOX2. These results reveal an important role for vU1s in the control of key regulatory networks orchestrating the transitions between stem cell maintenance and differentiation. Moreover,vU1 expression varies inversely with U1 expression during differentiation and cell re-programming and this pattern of expression is specifically de-regulated in iPSC-derived motor neurons from Spinal Muscular Atrophy (SMA) type 1 patient's. Accordingly,we suggest that an imbalance in the vU1/U1 ratio,rather than an overall reduction in Uridyl-rich (U)-snRNAs,may contribute to the specific neuromuscular disease phenotype associated with SMA. View Publication

BACKGROUND The Activin A and bone morphogenetic protein (BMP) pathways are critical regulators of the immune system and of bone formation. Inappropriate activation of these pathways,as in conditions of congenital heterotopic ossification,are thought to activate an osteogenic program in endothelial cells. However,if and how this occurs in human endothelial cells remains unclear. METHODS We used a new directed differentiation protocol to create human induced pluripotent stem cell (hiPSC)-derived endothelial cells (iECs) from patients with fibrodysplasia ossificans progressiva (FOP),a congenital disease of heterotopic ossification caused by an activating R206H mutation in the Activin A type I receptor (ACVR1). This strategy allowed the direct assay of the cell-autonomous effects of ACVR1 R206H in the endogenous locus without the use of transgenic expression. These cells were challenged with BMP or Activin A ligand,and tested for their ability to activate osteogenesis,extracellular matrix production,and differential downstream signaling in the BMP/Activin A pathways. RESULTS We found that FOP iECs could form in conditions with low or absent BMP4. These conditions are not normally permissive in control cells. FOP iECs cultured in mineralization media showed increased alkaline phosphatase staining,suggesting formation of immature osteoblasts,but failed to show mature osteoblastic features. However,FOP iECs expressed more fibroblastic genes and Collagen 1/2 compared to control iECs,suggesting a mechanism for the tissue fibrosis seen in early heterotopic lesions. Finally,FOP iECs showed increased SMAD1/5/8 signaling upon BMP4 stimulation. Contrary to FOP hiPSCs,FOP iECs did not show a significant increase in SMAD1/5/8 phosphorylation upon Activin A stimulation,suggesting that the ACVR1 R206H mutation has a cell type-specific effect. In addition,we found that the expression of ACVR1 and type II receptors were different in hiPSCs and iECs,which could explain the cell type-specific SMAD signaling. CONCLUSIONS Our results suggest that the ACVR1 R206H mutation may not directly increase the formation of mature chondrogenic or osteogenic cells by FOP iECs. Our results also show that BMP can induce endothelial cell dysfunction,increase expression of fibrogenic matrix proteins,and cause differential downstream signaling of the ACVR1 R206H mutation. This iPSC model provides new insight into how human endothelial cells may contribute to the pathogenesis of heterotopic ossification. View Publication

Cardiovascular progenitor cells (CPCs) expressing the ISL1-LIM-homeodomain transcription factor contribute developmentally to cardiomyocytes in all 4 chambers of the heart. Here,we show that ISL1-CPCs can be applied to myocardial regeneration following injury. We used a rapid 3D methylcellulose approach to form murine and human ISL1-CPC spheroids that engrafted after myocardial infarction in murine hearts,where they differentiated into cardiomyocytes and endothelial cells,integrating into the myocardium and forming new blood vessels. ISL1-CPC spheroid-treated mice exhibited reduced infarct area and increased blood vessel formation compared with control animals. Moreover,left ventricular (LV) contractile function was significantly better in mice transplanted with ISL1-CPCs 4 weeks after injury than that in control animals. These results provide proof-of-concept of a cardiac repair strategy employing ISL1-CPCs that,based on our previous lineage-tracing studies,are committed to forming heart tissue,in combination with a robust methylcellulose spheroid-based delivery approach. View Publication

Genome-wide association studies (GWASs) have increased our knowledge of loci associated with a range of human diseases. However,applying such findings to elucidate pathophysiology and promote drug discovery remains challenging. Here,we created isogenic human ESCs (hESCs) with mutations in GWAS-identified susceptibility genes for type 2 diabetes. In pancreatic beta-like cells differentiated from these lines,we found that mutations in CDKAL1,KCNQ1,and KCNJ11 led to impaired glucose secretion in vitro and in vivo,coinciding with defective glucose homeostasis. CDKAL1 mutant insulin+ cells were also hypersensitive to glucolipotoxicity. A high-content chemical screen identified a candidate drug that rescued CDKAL1-specific defects in vitro and in vivo by inhibiting the FOS/JUN pathway. Our approach of a proof-of-principle platform,which uses isogenic hESCs for functional evaluation of GWAS-identified loci and identification of a drug candidate that rescues gene-specific defects,paves the way for precision therapy of metabolic diseases. View Publication

A critical component of innate immune response to infection and tissue damage is the NACHT,LRR,and PYD domains-containing protein 3 (NLRP3) inflammasome,and this pathway and its activation products have been implicated in the pathophysiology of a variety of diseases. NLRP3 inflammasome activation leads to the cleavage of pro-IL-1β and pro-IL-18,as well as the subsequent release of biologically active IL-1β,IL-18,and other soluble mediators of inflammation. In this study,we further define the pharmacology of the previously reported NLRP3 inflammasome-selective,IL-1β processing inhibitor CP-456,773 (also known as MCC950),and we demonstrate its efficacy in two in vivo models of inflammation. Specifically,we show that in human and mouse innate immune cells CP-456,773 is an inhibitor of the cellular release of IL-1β,IL-1α,and IL-18,that CP-456,773 prevents inflammasome activation induced by disease-relevant soluble and crystalline NLRP3 stimuli,and that CP-456,773 inhibits R848- and imiquimod-induced IL-1β release. In mice,CP-456,773 demonstrates potent inhibition of the release of proinflammatory cytokines following acute i.p. challenge with LPS plus ATP in a manner that is proportional to the free/unbound concentrations of the drug,thereby establishing an in vivo pharmacokinetic/pharmacodynamic model for CP-456,773. Furthermore,CP-456,773 reduces ear swelling in an imiquimod cream-induced mouse model of skin inflammation,and it reduces airway inflammation in mice following acute challenge with house dust mite extract. These data implicate the NLRP3 inflammasome in the pathogenesis of dermal and airway inflammation,and they highlight the utility of CP-456,773 for interrogating the contribution of the NLRP3 inflammasome and its outputs in preclinical models of inflammation and disease. View Publication

Pantothenate kinase-associated neurodegeneration (PKAN) is an early onset and severely disabling neurodegenerative disease for which no therapy is available. PKAN is caused by mutations in PANK2,which encodes for the mitochondrial enzyme pantothenate kinase 2. Its function is to catalyze the first limiting step of Coenzyme A (CoA) biosynthesis. We generated induced pluripotent stem cells from PKAN patients and showed that their derived neurons exhibited premature death,increased ROS production,mitochondrial dysfunctions-including impairment of mitochondrial iron-dependent biosynthesis-and major membrane excitability defects. CoA supplementation prevented neuronal death and ROS formation by restoring mitochondrial and neuronal functionality. Our findings provide direct evidence that PANK2 malfunctioning is responsible for abnormal phenotypes in human neuronal cells and indicate CoA treatment as a possible therapeutic intervention. View Publication

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases,yet current therapeutic treatments are inadequate due to a complex disease pathogenesis. The plant polyphenol apigenin has been shown to have anti-inflammatory and neuroprotective properties in a number of cell and animal models; however a comprehensive assessment has not been performed in a human model of AD. Here we have used a human induced pluripotent stem cell (iPSC) model of familial and sporadic AD,in addition to healthy controls,to assess the neuroprotective activity of apigenin. The iPSC-derived AD neurons demonstrated a hyper-excitable calcium signalling phenotype,elevated levels of nitrite,increased cytotoxicity and apoptosis,reduced neurite length and increased susceptibility to inflammatory stress challenge from activated murine microglia,in comparison to control neurons. We identified that apigenin has potent anti-inflammatory properties with the ability to protect neurites and cell viability by promoting a global down-regulation of cytokine and nitric oxide (NO) release in inflammatory cells. In addition,we show that apigenin is able to protect iPSC-derived AD neurons via multiple means by reducing the frequency of spontaneous Ca(2+) signals and significantly reducing caspase-3/7 mediated apoptosis. These data demonstrate the broad neuroprotective action of apigenin against AD pathogenesis in a human disease model. View Publication

West Nile virus (WNV) infection is a mosquito-borne zoonosis with increasing prevalence in the United States. WNV infection begins in the skin,and the virus replicates initially in keratinocytes and dendritic cells (DCs). In the skin and cutaneous lymph nodes,infected DCs are likely to interact with invariant natural killer T cells (iNKTs). Bidirectional interactions between DCs and iNKTs amplify the innate immune response to viral infections,thus controlling viral load and regulating adaptive immunity. iNKTs are stimulated by CD1d-bound lipid antigens or activated indirectly by inflammatory cytokines. We exposed human monocyte-derived DCs to WNV Kunjin and determined their ability to activate isolated blood iNKTs. DCs became infected as judged by synthesis of viral mRNA and Envelope and NS-1 proteins,but did not undergo significant apoptosis. Infected DCs up-regulated the co-stimulatory molecules CD86 and CD40,but showed decreased expression of CD1d. WNV infection induced DC secretion of type I interferon (IFN),but no or minimal interleukin (IL)-12,IL-23,IL-18 or IL-10. Unexpectedly,we found that the WNV-infected DCs stimulated human iNKTs to up-regulate CD69 and produce low amounts of IL-10,but not proinflammatory cytokines such as IFN-γ or tumour necrosis factor (TNF)-α. Both CD1d and IFNAR blockade partially abrogated this iNKT response,suggesting involvement of a T cell receptor (TCR)-CD1d interaction and type I interferon receptor (IFNAR) signalling. Thus,WNV infection interferes with DC-iNKT interactions by preventing the production of proinflammatory cytokines. iNKTs may be a source of IL-10 observed in human flavivirus infections and initiate an anti-inflammatory innate response that limits adaptive immunity and immune pathology upon WNV infection. View Publication

The emerging models of human embryonic stem cell (hESC) self-organizing organoids provide a valuable in vitro platform for studying self-organizing processes that presumably mimic in vivo human developmental events. Here we report that through a chemical screen,we identified two novel and structurally similar small molecules BIR1 and BIR2 which robustly induced the self-organization of a balloon-shaped three-dimensional structure when applied to two-dimensional adherent hESC cultures in the absence of growth factors. Gene expression analyses and functional assays demonstrated an endothelial identity of this balloon-like structure,while cell surface marker analyses revealed a VE-cadherin+CD31+CD34+KDR+CD43???putative endothelial progenitor population. Furthermore,molecular marker labeling and morphological examinations characterized several other distinct DiI-Ac-LDL+multi-cellular modules and a VEGFR3+sprouting structure in the balloon cultures that likely represented intermediate structures of balloon-formation. View Publication