Instructor, Pediatrics - Cardiology
β-adrenergic signaling pathways mediate key aspects of cardiac function. Its dysregulation is associated with a range of cardiac diseases, including dilated cardiomyopathy (DCM). Previously, we established an iPSC model of familial DCM from patients with a mutation in TNNT2, a sarcomeric protein. Here, we found that the β-adrenergic agonist isoproterenol induced mature β-adrenergic signaling in iPSC-derived cardiomyocytes (iPSC-CMs) but that this pathway was blunted in DCM iPSC-CMs. Although expression levels of several β-adrenergic signaling components were unaltered between control and DCM iPSC-CMs, we found that phosphodiesterases (PDEs) 2A and PDE3A were upregulated in DCM iPSC-CMs and that PDE2A was also upregulated in DCM patient tissue. We further discovered increased nuclear localization of mutant TNNT2 and epigenetic modifications of PDE genes in both DCM iPSC-CMs and patient tissue. Notably, pharmacologic inhibition of PDE2A and PDE3A restored cAMP levels and ameliorated the impaired β-adrenergic signaling of DCM iPSC-CMs, suggesting therapeutic potential.
View details for DOI 10.1016/j.stem.2015.04.020
View details for Web of Science ID 000361877600011
High-fat diet-induced obesity (DIO) is a major contributor to type II diabetes and micro- and macro-vascular complications leading to peripheral vascular disease (PVD). Metabolic abnormalities of induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) from obese individuals could potentially limit their therapeutic efficacy for PVD. The aim of this study was to compare the function of iPSC-ECs from normal and DIO mice using comprehensive in vitro and in vivo assays.Six-week-old C57Bl/6 mice were fed with a normal or high-fat diet. At 24 weeks, iPSCs were generated from tail tip fibroblasts and differentiated into iPSC-ECs using a directed monolayer approach. In vitro functional analysis revealed that iPSC-ECs from DIO mice had significantly decreased capacity to form capillary-like networks, diminished migration, and lower proliferation. Microarray and ELISA confirmed elevated apoptotic, inflammatory, and oxidative stress pathways in DIO iPSC-ECs. Following hindlimb ischaemia, mice receiving intramuscular injections of DIO iPSC-ECs had significantly decreased reperfusion compared with mice injected with control healthy iPSC-ECs. Hindlimb sections revealed increased muscle atrophy and presence of inflammatory cells in mice receiving DIO iPSC-ECs. When pravastatin was co-administered to mice receiving DIO iPSC-ECs, a significant increase in reperfusion was observed; however, this beneficial effect was blunted by co-administration of the nitric oxide synthase inhibitor, N(ω)-nitro-l-arginine methyl ester.This is the first study to provide evidence that iPSC-ECs from DIO mice exhibit signs of endothelial dysfunction and have suboptimal efficacy following transplantation in a hindlimb ischaemia model. These findings may have important implications for future treatment of PVD using iPSC-ECs in the obese population.
View details for DOI 10.1093/eurheartj/ehu411
View details for Web of Science ID 000353539800012
View details for PubMedID 25368203
Human induced pluripotent stem cells (iPSCs) play an important role in disease modeling and drug testing. However, the current methods are time-consuming and lack an isogenic control.This study sought to establish an efficient technology to generate human PSC-based disease models with isogenic control.The ion channel genes KCNQ1 and KCNH2 with dominant negative mutations causing long QT syndrome types 1 and 2, respectively, were stably integrated into a safe harbor AAVS1 locus using zinc finger nuclease technology.Patch-clamp recording revealed that the edited iPSC-derived cardiomyocytes (iPSC-CMs) displayed characteristic long QT syndrome phenotype and significant prolongation of the action potential duration compared with the unedited control cells. Finally, addition of nifedipine (L-type calcium channel blocker) or pinacidil (KATP-channel opener) shortened the action potential duration of iPSC-CMs, confirming the validity of isogenic iPSC lines for drug testing in the future.Our study demonstrates that iPSC-CM-based disease models can be rapidly generated by overexpression of dominant negative gene mutants.
View details for DOI 10.1016/j.jacc.2014.04.057
View details for Web of Science ID 000340241100005
Induced pluripotent stem cells (iPSCs) hold great promise for the development of patient-specific therapies for cardiovascular disease. However, clinical translation will require preclinical optimization and validation of large-animal iPSC models.To successfully derive endothelial cells from porcine iPSCs and demonstrate their potential utility for the treatment of myocardial ischemia.Porcine adipose stromal cells were reprogrammed to generate porcine iPSCs (piPSCs). Immunohistochemistry, quantitative PCR, microarray hybridization, and angiogenic assays confirmed that piPSC-derived endothelial cells (piPSC-ECs) shared similar morphological and functional properties as endothelial cells isolated from the autologous pig aorta. To demonstrate their therapeutic potential, piPSC-ECs were transplanted into mice with myocardial infarction. Compared with control, animals transplanted with piPSC-ECs showed significant functional improvement measured by echocardiography (fractional shortening at week 4: 27.2±1.3% versus 22.3±1.1%; P<0.001) and MRI (ejection fraction at week 4: 45.8±1.3% versus 42.3±0.9%; P<0.05). Quantitative protein assays and microfluidic single-cell PCR profiling showed that piPSC-ECs released proangiogenic and antiapoptotic factors in the ischemic microenvironment, which promoted neovascularization and cardiomyocyte survival, respectively. Release of paracrine factors varied significantly among subpopulations of transplanted cells, suggesting that transplantation of specific cell populations may result in greater functional recovery.In summary, this is the first study to successfully differentiate piPSCs-ECs from piPSCs and demonstrate that transplantation of piPSC-ECs improved cardiac function after myocardial infarction via paracrine activation. Further development of these large animal iPSC models will yield significant insights into their therapeutic potential and accelerate the clinical translation of autologous iPSC-based therapy.
View details for DOI 10.1161/CIRCRESAHA.112.269001
View details for Web of Science ID 000308868800015
View details for PubMedID 22821929
As inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, statins have pleiotropic vascular-protective effects, such as anti-inflammatory and antioxidative effects. We investigated the short-term beneficial effects of statins on modulating the translocation of lipid-raft-related proteins in endothelial cells (ECs). Human umbilical vein ECs were treated with atorvastatin for 30 min or 2 h; lipid-raft proteins were isolated and examined by quantitative proteome assay. Functional classification of identified proteins in lipid rafts revealed upregulated antioxidative proteins; downregulated proteins were associated with inflammation and cell adhesion. Among proteins verified by Western blot analysis, endoplasmic reticulum protein 46 (ERp46) showed increased level in lipid rafts with atorvastatin. Further, atorvastatin inhibited the activation of membrane-bound NADPH oxidase in both untreated and angiotensin II-treated ECs, as shown by reduced reactive oxygen species production. Co-immunoprecipitation and immunofluorescence experiments revealed that atorvastatin increased the association of ERp46 and Nox2, an NADPH oxidase isoform, in lipid rafts, thereby inhibiting Nox2 assembly with its regulatory subunits, such as p47phox and p67phox. Our results reveal a novel antioxidative role of atorvastatin by promoting the membrane translocation of ERp46 and its binding with Nox2 to inhibit Nox2 activity in ECs, which may offer another insight into the pleiotropic functions of statins.
View details for DOI 10.1021/pr300098f
View details for Web of Science ID 000302388100028
View details for PubMedID 22428589
Endothelial cells (ECs) have distinct mechanotransduction mechanisms responding to laminar versus disturbed flow patterns. Endothelial dysfunction, affected by imposed flow, is one of the earliest events leading to atherogenesis. The involvement of γ/δ T lymphocytes in endothelial dysfunction under flow is largely unknown.To investigate whether shear stress regulates membrane translocation of ATP synthase β chain (ATPSβ) in ECs, leading to the increased γ/δ T-lymphocyte adhesion and the related functions.We applied different flow patterns to cultured ECs. Laminar flow decreased the level of membrane-bound ATPSβ (ecto-ATPSβ) and depleted membrane cholesterol, whereas oscillatory flow increased the level of ecto-ATPSβ and membrane cholesterol. Incubating ECs with cholesterol or depleting cellular cholesterol with β-cyclodextrin mimicked the effect of oscillatory or laminar flow, respectively. Knockdown caveolin-1 by small interfering RNA prevented ATPSβ translocation in response to laminar flow. Importantly, oscillatory flow or cholesterol treatment elevated the number of γ/δ T cells binding to ECs, which was blocked by anti-ATPSβ antibody. Furthermore, the incubation of γ/δ T cells with ECs increased tumor necrosis fact α and interferon-γ secretion from T cells and vascular cell adhesion molecule-1 expression in ECs. In vivo, γ/δ T-cell adhesion and ATPSβ membrane translocation was elevated in the aortic inner curvature and disturbed flow areas in partially ligated carotid arteries of ApoE(-/-) mice fed a high-fat diet.This study provides evidence that disturbed flow and hypercholesterolemia synergistically promote γ/δ T-lymphocyte activation by the membrane translocation of ATPSβ in ECs and in vivo in mice, which is a novel mechanism of endothelial activation.
View details for DOI 10.1161/CIRCRESAHA.110.230151
View details for Web of Science ID 000287484200007
View details for PubMedID 21193741
Brugada syndrome (BrS), a disorder associated with characteristic electrocardiogram precordial ST-segment elevation, predisposes afflicted patients to ventricular fibrillation and sudden cardiac death. Despite marked achievements in outlining the organ level pathophysiology of the disorder, the understanding of human cellular phenotype has lagged due to a lack of adequate human cellular models of the disorder.The objective of this study was to examine single cell mechanism of Brugada syndrome using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs).This study recruited 2 patients with type 1 BrS carrying 2 different sodium voltage-gated channel alpha subunit 5 variants as well as 2 healthy control subjects. We generated iPSCs from their skin fibroblasts by using integration-free Sendai virus. We used directed differentiation to create purified populations of iPSC-CMs.BrS iPSC-CMs showed reductions in inward sodium current density and reduced maximal upstroke velocity of action potential compared with healthy control iPSC-CMs. Furthermore, BrS iPSC-CMs demonstrated increased burden of triggered activity, abnormal calcium (Ca(2+)) transients, and beating interval variation. Correction of the causative variant by genome editing was performed, and resultant iPSC-CMs showed resolution of triggered activity and abnormal Ca(2+) transients. Gene expression profiling of iPSC-CMs showed clustering of BrS compared with control subjects. Furthermore, BrS iPSC-CM gene expression correlated with gene expression from BrS human cardiac tissue gene expression.Patient-specific iPSC-CMs were able to recapitulate single-cell phenotype features of BrS, including blunted inward sodium current, increased triggered activity, and abnormal Ca(2+) handling. This novel human cellular model creates future opportunities to further elucidate the cellular disease mechanism and identify novel therapeutic targets.
View details for DOI 10.1016/j.jacc.2016.07.779
View details for PubMedID 27810048
Idiopathic or heritable pulmonary arterial hypertension is characterized by loss and obliteration of lung vasculature. Endothelial cell dysfunction is pivotal to the pathophysiology but different causal mechanisms may reflect a need for patient-tailored therapies.Endothelial cells differentiated from induced pluripotent stem cells were compared to pulmonary arterial endothelial cells from the same patients with idiopathic or heritable pulmonary arterial hypertension, to determine whether they shared functional abnormalities and altered gene expression patterns, that differed from those in unused donor cells. We then investigated whether endothelial cells differentiated from pluripotent cells could serve as surrogates to test emerging therapies.Functional changes assessed included adhesion, migration, tube formation, and propensity to apoptosis. Expression of BMPR2 and its target, collagen IV, pSMAD1/5 signaling and transcriptomic profiles were also analyzed.Native pulmonary arterial and induced pluripotent stem cell-derived endothelial cells from idiopathic and heritable pulmonary arterial hypertension patients compared to controls, showed a similar reduction in adhesion, migration, survival, and tube formation, decreased BMPR2 and downstream signaling and collagen IV expression. Transcriptomic profiling revealed high KISS1 related to reduced migration and low CES1, to impaired survival in patient cells. A beneficial angiogenic response to potential therapies, FK-506 and Elafin, was related to reduced SLIT3, an anti-migratory factor.Despite the site of disease in the lung our study indicates that induced pluripotent stem cell derived endothelial cells are useful surrogates to uncover novel features related to disease mechanisms and to better match patients to therapies.
View details for PubMedID 27779452
-We previously reported high-throughput RNA sequencing analyses that identified heightened expression of the chromatin architectural factor High Mobility Group AT-hook 1 (HMGA1) in pulmonary arterial (PA) endothelial cells (ECs) from idiopathic PA hypertension (IPAH) patients compared to controls. Since HMGA1 promotes epithelial to mesenchymal transition in cancer, we hypothesized that increased HMGA1 could induce transition of PAECs to a smooth muscle (SM)-like mesenchymal phenotype (EndMT), explaining both dysregulation of PAEC function and possible cellular contribution to the occlusive remodeling that characterizes advanced IPAH.-We documented increased HMGA1 in PAECs cultured from IPAH vs. donor control lungs. Confocal microscopy of lung explants localized the increase in HMGA1 consistently to PA endothelium, and identified many cells double-positive for HMGA1 and smooth muscle 22 alpha (SM22α) in occlusive and plexogenic lesions. Since decreased expression and function of bone morphogenetic protein receptor (BMPR)2 is observed in PAH, we reduced BMPR2 by siRNA in control PAECs and documented an increase in HMGA1 protein. Consistent with transition of PAECs by HMGA1, we detected reduced PECAM-1 (CD31) and increased EndMT markers, αSMA, SM22α, calponin, phospho-vimentin and Slug. The transition was associated with spindle SM-like morphology, and the increase in αSMA was largely reversed by joint knockdown of BMPR2 and HMGA1 or Slug. Pulmonary ECs from mice with EC-specific loss of BMPR2 showed similar gene and protein changes.-Increased HMGA1 in PAECs resulting from dysfunctional BMPR2 signaling can transition endothelium to SM-like cells associated with PAH.
View details for DOI 10.1161/CIRCULATIONAHA.115.020617
View details for Web of Science ID 000375604400008
View details for PubMedID 27045138
Pulmonary arterial hypertension is characterized by endothelial dysregulation, but global changes in gene expression have not been related to perturbations in function.RNA sequencing was utilized to discriminate changes in transcriptomes of endothelial cells cultured from lungs of patients with idiopathic pulmonary arterial hypertension vs. controls and to assess the functional significance of major differentially expressed transcripts.The endothelial transcriptomes from seven control and six idiopathic pulmonary arterial hypertension patients' lungs were analyzed. Differentially expressed genes were related to BMPR2 signaling. Those downregulated were assessed for function in cultured cells, and in a transgenic mouse.Fold-differences in ten genes were significant (p<0.05), four increased and six decreased in patients vs.No patient was mutant for BMPR2. However, knockdown of BMPR2 by siRNA in control pulmonary arterial endothelial cells recapitulated six/ten patient-related gene changes, including decreased collagen IV (COL4A1, COL4A2) and ephrinA1 (EFNA1). Reduction of BMPR2 regulated transcripts was related to decreased β-catenin. Reducing COL4A1, COL4A2 and EFNA1 by siRNA inhibited pulmonary endothelial adhesion, migration and tube formation. In mice null for the EFNA1 receptor, EphA2, vs. controls, VEGF receptor blockade and hypoxia caused more severe pulmonary hypertension, judged by elevated right ventricular systolic pressure, right ventricular hypertrophy and loss of small arteries.The novel relationship between BMPR2 dysfunction and reduced expression of endothelial COL4 and EFNA1 may underlie vulnerability to injury in pulmonary arterial hypertension.
View details for DOI 10.1164/rccm.201408-1528OC
View details for Web of Science ID 000359178500017
View details for PubMedID 26030479
Pulmonary arterial hypertension is characterized by endothelial cell dysfunction, impaired BMPR2 signaling, and increased elastase activity. Synthetic elastase inhibitors reverse experimental pulmonary hypertension but cause hepatotoxicity in clinical studies. The endogenous elastase inhibitor elafin attenuates the development of hypoxic pulmonary hypertension in mice, but its potential to improve endothelial cell function and BMPR2 signaling, and to reverse severe experimental pulmonary hypertension or vascular pathology in the human disease was unknown.To assess elafin-mediated regression of pulmonary vascular pathology in rats with pulmonary hypertension induced by VEGF receptor blockade and hypoxia (Sugen/Hypoxia), and in lung explants from pulmonary hypertension patients. To determine if elafin amplifies BMPR2 signaling in pulmonary artery endothelial cells from controls and patients, and to elucidate the underlying mechanism. Methods, Measurements and Main Results: In Sugen/Hypoxia rats, elafin reduced elastase activity and reversed pulmonary hypertension, judged by regression of right ventricular systolic pressure and hypertrophy and pulmonary artery occlusive changes. Elafin improved endothelial function by increasing apelin, a product of BMPR2 signaling. Elafin induced apoptosis in human pulmonary arterial smooth muscle cells and in lung organ culture elafin decreased neointimal lesions. In normal and patient pulmonary artery endothelial cells, elafin enhanced survival and promoted angiogenesis by increasing pSMAD dependent and independent BMPR2 signaling. This was linked mechanistically to augmented interaction of BMPR2 with caveolin-1 via elafin-mediated stabilization of caveolin-1 on endothelial surfaces.Elafin reverses obliterative changes in rat and human pulmonary arteries via elastase inhibition and caveolin-1 dependent amplification of BMPR2 signaling.
View details for DOI 10.1164/rccm.201412-2291OC
View details for Web of Science ID 000356105000014
The path to induced pluripotency Discovery of a pan-species pluripotency network Animal iPSCs and disease modelling Issues with large animal iPSCs Conclusions The derivation of human embryonic stem cells and subsequently human induced pluripotent stem cells (iPSCs) has energized regenerative medicine research and enabled seemingly limitless applications. Although small animal models, such as mouse models, have played an important role in the progression of the field, typically, they are poor representations of the human disease phenotype. As an alternative, large animal models should be explored as a potentially better approach for clinical translation of cellular therapies. However, only fragmented information regarding the derivation, characterization and clinical usefulness of pluripotent large animal cells is currently available. Here, we briefly review the latest advances regarding the derivation and use of large animal iPSCs.
View details for DOI 10.1111/j.1582-4934.2012.01521.x
View details for Web of Science ID 000304468600005
View details for PubMedID 22212700