title: Modeling of Friedreich ataxia-related iron overloading cardiomyopathy using patient-specific-induced pluripotent stem cells.
abstract: 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 Ca(2+) 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.
authors: Cardiology Division, Department of Medicine, Li Ka Shing Faculty of Medicine, the University of Hong Kong, Hong Kong, China.
authors: Yee-Ki
authors: YK
authors: Lee
authors: Philip Wing-Lok
authors: PW
authors: Ho
authors: Revital
authors: R
authors: Schick
authors: Yee-Man
authors: YM
authors: Lau
authors: Wing-Hon
authors: WH
authors: Lai
authors: Ting
authors: T
authors: Zhou
authors: Yanhua
authors: Y
authors: Li
authors: Kwong-Man
authors: KM
authors: Ng
authors: Shu-Leung
authors: SL
authors: Ho
authors: Miguel Angel
authors: MA
authors: Esteban
authors: Ofer
authors: O
authors: Binah
authors: Hung-Fat
authors: HF
authors: Tse
authors: Chung-Wah
authors: CW
authors: Siu
mesh_terms: D000328:Adult; D009202:Cardiomyopathies / Q000209:etiology; D005260:Female; D005621:Friedreich Ataxia / Q000150:complications* / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D019190:Iron Overload / Q000150:complications; D033862:Iron-Binding Proteins / Q000235:genetics; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology; D039904:Pluripotent Stem Cells; D000096923:Frataxin
chemical_list: D033862:Iron-Binding Proteins; D000096923:Frataxin