title: Novel insights on the relationship between T-tubular defects and contractile dysfunction in a mouse model of hypertrophic cardiomyopathy.
abstract: Abnormalities of cardiomyocyte Ca(2+) homeostasis and excitation-contraction (E-C) coupling are early events in the pathogenesis of hypertrophic cardiomyopathy (HCM) and concomitant determinants of the diastolic dysfunction and arrhythmias typical of the disease. T-tubule remodelling has been reported to occur in HCM but little is known about its role in the E-C coupling alterations of HCM. Here, the role of T-tubule remodelling in the electro-mechanical dysfunction associated to HCM is investigated in the Δ160E cTnT mouse model that expresses a clinically-relevant HCM mutation. Contractile function of intact ventricular trabeculae is assessed in Δ160E mice and wild-type siblings. As compared with wild-type, Δ160E trabeculae show prolonged kinetics of force development and relaxation, blunted force-frequency response with reduced active tension at high stimulation frequency, and increased occurrence of spontaneous contractions. Consistently, prolonged Ca(2+) transient in terms of rise and duration are also observed in Δ160E trabeculae and isolated cardiomyocytes. Confocal imaging in cells isolated from Δ160E mice reveals significant, though modest, remodelling of T-tubular architecture. A two-photon random access microscope is employed to dissect the spatio-temporal relationship between T-tubular electrical activity and local Ca(2+) release in isolated cardiomyocytes. In Δ160E cardiomyocytes, a significant number of T-tubules (>20%) fails to propagate action potentials, with consequent delay of local Ca(2+) release. At variance with wild-type, we also observe significantly increased variability of local Ca(2+) transient rise as well as higher Ca(2+)-spark frequency. Although T-tubule structural remodelling in Δ160E myocytes is modest, T-tubule functional defects determine non-homogeneous Ca(2+) release and delayed myofilament activation that significantly contribute to mechanical dysfunction.
authors.affiliation: European Laboratory for Non-Linear Spectroscopy, 50019 Florence, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Crocini
authors.affiliation: Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence, 50134 Florence, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Ferrantini
authors.affiliation: European Laboratory for Non-Linear Spectroscopy, 50019 Florence, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Scardigli
authors.affiliation: Division of Pharmacology, Department "NeuroFarBa", University of Florence, 50139 Florence, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Coppini
authors.affiliation: Division of Pharmacology, Department "NeuroFarBa", University of Florence, 50139 Florence, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Mazzoni
authors.affiliation: European Laboratory for Non-Linear Spectroscopy, 50019 Florence, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Lazzeri
authors.affiliation: Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence, 50134 Florence, Italy.
authors.forename: J M
authors.initials: JM
authors.lastname: Pioner
authors.affiliation: Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence, 50134 Florence, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Scellini
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and Francois M. Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: A
authors.initials: A
authors.lastname: Guo
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine and Francois M. Abboud Cardiovascular Research Center, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: L S
authors.initials: LS
authors.lastname: Song
authors.affiliation: R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030, USA.
authors.forename: P
authors.initials: P
authors.lastname: Yan
authors.affiliation: R. D. Berlin Center for Cell Analysis and Modeling, University of Connecticut Health Center, Farmington, CT 06030, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Loew
authors.affiliation: Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: J
authors.initials: J
authors.lastname: Tardiff
authors.affiliation: Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence, 50134 Florence, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Tesi
authors.affiliation: European Laboratory for Non-Linear Spectroscopy, 50019 Florence, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Vanzi
authors.affiliation: Division of Pharmacology, Department "NeuroFarBa", University of Florence, 50139 Florence, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Cerbai
authors.affiliation: European Laboratory for Non-Linear Spectroscopy, 50019 Florence, Italy; Department of Physics and Astronomy, University of Florence, 50019 Sesto Fiorentino, Italy; National Institute of Optics, National Research Council, 50125 Florence, Italy.
authors.forename: F S
authors.initials: FS
authors.lastname: Pavone
authors.affiliation: European Laboratory for Non-Linear Spectroscopy, 50019 Florence, Italy; National Institute of Optics, National Research Council, 50125 Florence, Italy. Electronic address: sacconi@lens.unifi.it.
authors.forename: L
authors.initials: L
authors.lastname: Sacconi
authors.affiliation: Division of Physiology, Department of Experimental and Clinical Medicine, University of Florence, 50134 Florence, Italy. Electronic address: corrado.poggesi@unifi.it.
authors.forename: C
authors.initials: C
authors.lastname: Poggesi
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D004195:Disease Models, Animal; D056966:Excitation Contraction Coupling; D015870:Gene Expression; D006801:Humans; D017136:Ion Transport; D051379:Mice; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009154:Mutation; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D009210:Myofibrils / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D061848:Optical Imaging; D012508:Sarcolemma / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D020107:Troponin T / Q000235:genetics / Q000378:metabolism
chemical_list: D020107:Troponin T; D002118:Calcium
keywords: Excitation–contraction coupling; Hypertrophic cardiomyopathy; Imaging; Non-linear microscopy; T-tubules