Kwong-Man Ng

Generation of induced pluripotent stem cells from urine

Forced expression of selected transcription factors can transform somatic cells into embryonic stem cell (ESC)-like cells, termed induced pluripotent stem cells (iPSCs). There is no consensus regarding the preferred tissue from which to harvest donor cells for reprogramming into iPSCs, and some donor cell types may be more prone than others to accumulation of epigenetic imprints and somatic cell mutations. Here, we present a simple, reproducible, noninvasive method for generating human iPSCs from renal tubular cells present in urine. This procedure eliminates many problems associated with other protocols, and the resulting iPSCs display an excellent ability to differentiate. These data suggest that urine may be a preferred source for generating iPSCs.

Chronic intermittent hypoxia induces local inflammation of the rat carotid body via functional upregulation of proinflammatory cytokine pathways

Maladaptive changes in the carotid body (CB) induced by chronic intermittent hypoxia (IH) account for the pathogenesis of cardiovascular morbidity in patients with sleep-disordered breathing. We postulated that the proinflammatory cytokines, namely interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α, and cytokine receptors (IL-1r1, gp130 and TNFr1) locally expressed in the rat CB play a pathophysiological role in IH-induced CB inflammation. Results showed increased levels of oxidative stress (serum 8-isoprostane and nitrotyrosine in the CB) in rats with 7-day IH treatment resembling recurrent apneic conditions when compared with the normoxic control. Local inflammation shown by the amount of ED1-containing cells (macrophage infiltration) and the gene transcripts of NADPH oxidase subunits (gp91phox and p22phox) and chemokines (MCP-1, CCR2, MIP-1α, MIP-1β and ICAM-1) in the CB were significantly more in the hypoxic group than in the control. In addition, the cytokines and receptors were expressed in the lobules of chemosensitive glomus cells containing tyrosine hydroxylase and the levels of expressions were significantly increased in the hypoxic group. Exogenous cytokines elevated the intracellular calcium ([Ca2+]i) response to acute hypoxia in the dissociated glomus cells. The effect of cytokines on the [Ca2+]i response was significantly greater in the hypoxic than in the normoxic group. Moreover, daily treatment of IH rats with anti-inflammatory drugs (dexamethasone or ibuprofen) attenuated the levels of oxidative stress, gp91phox expression and macrophage infiltration in the CB. Collectively, these results suggest that the upregulated expression of proinflammatory cytokine pathways could mediate the local inflammation and functional alteration of the CB under chronic IH conditions.

Effects of iron oxide nanoparticles on cardiac differentiation of embryonic stem cells

The therapeutic potential of transplantation of embryonic stem cells (ESCs) in animal model of myocardial infarction has been consistently demonstrated. The development of superparamagnetic iron oxide (SPIO) nanoparticles labeling and cardiac magnetic resonance imaging (MRI) have been increasingly used to track the migration of transplanted cells in vivo allowing cell fate determination. However, the impact of SPIO- labeling on cell phenotype and cardiac differentiation capacity of ESCs remains unclear. In this study, we demonstrated that ESCs labeled with SPIO compared to their unlabeled counterparts had similar cardiogenic capacity, and SPIO-labeling did not affect calcium-handling property of ESC-derived cardiomyocytes. Moreover, transplantation of SPIO-labeled ESCs via direct intra-myocardial injection to infarct myocardium resulted in significant improvement in heart function. These findings demonstrated the feasibility of in vivo ESC tracking using SPIO-labeling and cardiac MRI without affecting the cardiac differentiation potential and functional properties of ESCs.

Patient-specific induced-pluripotent stem cells-derived cardiomyocytes recapitulate the pathogenic phenotypes of dilated cardiomyopathy due to a novel DES mutation identified by whole exome sequencing

In this paper, we report a novel heterozygous mutation of A285V codon conversion on exon 4 of the desmin (DES), using whole exome sequencing (WES) in an isolated proband with documented dilated cardiomyopathy (DCM). This mutation is predicted to cause three-dimensional structure changes of DES. Immunohistological and electron microscopy studies demonstrated diffuse abnormal DES aggregations in DCM-induced-pluripotent stem cell (iPSC)-derived cardiomyocytes, and control-iPSC-derived cardiomyocytes transduced with A285V-DES. DCM-iPSC-derived cardiomyocytes also exhibited functional abnormalities in vitro. This is the first demonstration that patient-specific iPSC-derived cardiomyocytes can be used to provide histological and functional confirmation of a suspected genetic basis for DCM identified by WES.

Modeling abnormal early development with induced pluripotent stem cells from aneuploid syndromes

Many human diseases share a developmental origin that manifests during childhood or maturity. Aneuploid syndromes are caused by supernumerary or reduced number of chromosomes and represent an extreme example of developmental disease, as they have devastating consequences before and after birth. Investigating how alterations in gene dosage drive these conditions is relevant because it might help treat some clinical aspects. It may also provide explanations as to how quantitative differences in gene expression determine phenotypic diversity and disease susceptibility among natural populations. Here, we aimed to produce induced pluripotent stem cell (iPSC) lines that can be used to improve our understanding of aneuploid syndromes. We have generated iPSCs from monosomy X [Turner syndrome (TS)], trisomy 8 (Warkany syndrome 2), trisomy 13 (Patau syndrome) and partial trisomy 11;22 (Emanuel syndrome), using either skin fibroblasts from affected individuals or amniocytes from antenatal diagnostic tests. These cell lines stably maintain the karyotype of the donors and behave like embryonic stem cells in all tested assays. TS iPSCs were used for further studies including global gene expression analysis and tissue-specific directed differentiation. Multiple clones displayed lower levels of the pseudoautosomal genes ASMTL and PPP2R3B than the controls. Moreover, they could be transformed into neural-like, hepatocyte-like and heart-like cells, but displayed insufficient up-regulation of the pseudoautosomal placental gene CSF2RA during embryoid body formation. These data support that abnormal organogenesis and early lethality in TS are not caused by a tissue-specific differentiation blockade, but rather involves other abnormalities including impaired placentation.

Exogenous expression of HIF-1α promotes cardiac differentiation of embryonic stem cells

Hypoxia plays an important role in the proliferation, differentiation and maintenance of the cardiovascular system during development. While low oxygen tension appears to direct the cultured embryonic stem cells (ESCs) to differentiate into cardiomyocytes, the underlying molecular mechanism remains unclear. At a molecular level, hypoxia inducible factor-1 (HIF-1) plays an important role in handling the hypoxia signal. In the present study, we demonstrated that expression of exogenous HIF-1 alpha cDNA into murine ESCs significantly promoted cardiogenesis as indicated by a higher percentage of beating embryoid body and troponin-T positive cell counts as well as increased expression of early and late cardiac markers, such as GATA-binding protein 4 and 6, NK2 transcription factor related locus 5, alpha-myosin heavy chain, beta-myosin heavy chain and myosin light chain 2 ventricular transcripts. In addition, the transduced cells exhibited increased mRNA levels of cardiotrophin-1 and vascular endothelial growth factor, along with phosphorylation of eNOS [p-eNOS (ser1171)]. Application of NOS inhibitors, diphenyleneiodonium chloride (DPI), N(omega)-Nitro-L-arginine methyl ester hydrochloride (L-NAME) or N(omega)-Nitro-L-arginine (L-NNA) abolished the HIF-1 alpha stimulated cardiac differentiation. With the clues of upregulated mRNA expression of calcium handling proteins, ryanodine receptor 2, sodium calcium exchanger and sarcoplasmic/endoplasmic reticulum calcium ATPase, in the transduced HIF-1 alpha ESCs, further study indicated that the maximum upstroke and decay velocity was significantly increased in both non-caffeine and caffeine-induced calcium transient in ESCs-derived cardiomyocytes. This suggests a well developed function of the sarcoplasmic reticulum in ESC-derived cardiomyocytes. Electrophysiological study also indicated that a portion of the HIF-1 alpha-transduced cells exhibited prominent phase-4 depolarization. These findings suggest that keen activation of the HIF-1 pathway enhances differentiation and maturation of cardiomyocytes derived from ESCs.

Upregulation of a local renin–angiotensin system in the rat carotid body during chronic intermittent hypoxia

•  What is the central question of this study? Expression of the renin–angiotensin system (RAS) may play a pathogenic role in the augmented activity of carotid body chemosensitive cells and the carotid body (CB) inflammation in chronic intermittent hypoxia (IH). The aim of this study was to examine the expression and function of the RAS components in the CB during chronic IH resembling a severe sleep‐apnoeic condition. •  What is the main finding and its importance? Chronic IH induces a functional upregulation of the RAS expression in the CB. The upregulation of RAS expression could play a pathogenic role in the augmented CB excitability during IH, which is relevant to early pathogenesis in sleep‐disordered breathing.

ROCK Inhibition Facilitates the Generation of Human-Induced Pluripotent Stem Cells in a Defined, Feeder-, and Serum-Free System

Human-induced pluripotent stem cells (iPSCs) generated from human adult somatic cells through reprogramming hold great promises for future regenerative medicine. However, exposure of human iPSCs to animal feeder and serum in the process of their generation and maintenance imposes risk of transmitting animal pathogens to human subjects, thus hindering the potential therapeutic applications. Here, we report the successful generation of human iPSCs in a feeder-independent culture system with defined factors. Two stable human iPSC lines were established from primary human dermal fibroblasts of two healthy volunteers. These human iPSCs expressed a panel of pluripotency markers including stage-specific embryonic antigen (SSEA)-4, tumor-rejection antigen (TRA)-1-60, TRA-1-81, and alkaline phosphatase, while maintaining normal karyotypes and the exogenous reprogramming factors being silenced. In addition, these human iPSCs can differentiate along lineages representative of the three embryonic germ layers upon formation of embryoid bodies, indicating their pluripotency. Furthermore, subcutaneous transplantation of these cells into immunodeficient mice resulted in teratoma formation in 6 to 8 weeks. Our findings are an important step toward generating patient-specific iPSCs in a more clinically compliant manner by eliminating the need of animal feeder cells and animal serum.

Modeling of Friedreich ataxia-related iron overloading cardiomyopathy using patient-specific-induced pluripotent stem cells

Friedreich ataxia (FRDA), a recessive neurodegenerative disorder commonly associated with hypertrophic cardiomyopathy, is due to GAA repeat expansions within the first intron of the frataxin (FXN) gene encoding the mitochondrial protein involved in iron–sulfur cluster biosynthesis. The triplet codon repeats lead to heterochromatin-mediated gene silencing and loss of frataxin. Nevertheless, inadequacy of existing FRDA-cardiac cellular models limited cardiomyopathy studies. We tested the hypothesis that iron homeostasis deregulation accelerates reduction in energy synthesis dynamics which contributes to impaired cardiac calcium homeostasis and contractile force. Silencing of FXN expressions occurred both in somatic FRDA-skin fibroblasts and two of the induced pluripotent stem cells (iPSC) clones; a sign of stress condition was shown in FRDA-iPSC cardiomyocytes with disorganized mitochondrial network and mitochondrial DNA (mtDNA) depletion; hypertrophic cardiac stress responses were observed by an increase in α-actinin-positive cell sizes revealed by FACS analysis as well as elevation in brain natriuretic peptide (BNP) gene expression; the intracellular iron accumulated in FRDA cardiomyocytes might be due to attenuated negative feedback response of transferring receptor (TSFR) expression and positive feedback response of ferritin (FTH1); energy synthesis dynamics, in terms of ATP production rate, was impaired in FRDA-iPSC cardiomyocytes, which were prone to iron overload condition. Energetic insufficiency determined slower Ca2+ transients by retarding calcium reuptake to sarcoplasmic reticulum (SR) and impaired the positive inotropic and chronotropic responses to adrenergic stimulation. Our data showed for the first time that FRDA-iPSCs cardiac derivatives represent promising models to study cardiac stress response due to impaired iron homeostasis condition and mitochondrial damages. The cardiomyopathy phenotype was accelerated in an iron-overloaded condition early in calcium homeostasis aspect.

Exogenous Expression of Human apoA-I Enhances Cardiac Differentiation of Pluripotent Stem Cells

The cardioprotective effects of high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A1 (apoA-I) are well documented, but their effects in the direction of the cardiac differentiation of embryonic stem cells are unknown. We evaluated the effects of exogenous apoA-I expression on cardiac differentiation of ESCs and maturation of ESC-derived cardiomyocytes. We stably over-expressed full-length human apoA-I cDNA with lentivirus (LV)-mediated gene transfer in undifferentiated mouse ESCs and human induced pluripotent stem cells. Upon cardiac differentiation, we observed a significantly higher percentage of beating embryoid bodies, an increased number of cardiomyocytes as determined by flow cytometry, and expression of cardiac markers including α-myosin heavy chain, β-myosin heavy chain and myosin light chain 2 ventricular transcripts in LV-apoA-I transduced ESCs compared with control (LV-GFP). In the presence of noggin, a BMP4 antagonist, activation of BMP4-SMAD signaling cascade in apoA-I transduced ESCs completely abolished the apoA-I stimulated cardiac differentiation. Furthermore, co-application of recombinant apoA-I and BMP4 synergistically increased the percentage of beating EBs derived from untransduced D3 ESCs. These together suggests that that pro-cardiogenic apoA-I is mediated via the BMP4-SMAD signaling pathway. Functionally, cardiomyocytes derived from the apoA-I-transduced cells exhibited improved calcium handling properties in both non-caffeine and caffeine-induced calcium transient, suggesting that apoA-I plays a role in enhancing cardiac maturation. This increased cardiac differentiation and maturation has also been observed in human iPSCs, providing further evidence of the beneficial effects of apoA-I in promoting cardiac differentiation. In Conclusion, we present novel experimental evidence that apoA-I enhances cardiac differentiation of ESCs and iPSCs and promotes maturation of the calcium handling property of ESC-derived cardiomyocytes via the BMP4/SMAD signaling pathway.