title: Mesenchymal stem cells improve cardiac conduction by upregulation of connexin 43 through paracrine signaling.
abstract: Mesenchymal stem cells (MSCs) were shown to improve cell survival and alleviate cardiac arrhythmias when transplanted into cardiac tissue; however, little is known about the mechanism by which MSCs modify the electrophysiological properties of cardiac tissue. We aimed to distinguish the influence of cell-cell coupling between myocytes and MSCs from that of MSC-derived paracrine factors on the spontaneous activity and conduction velocity (θ) of multicellular cardiomyocyte preparations. HL-1 cells were plated on microelectrode arrays and their spontaneous activity and θ was determined from field potential recordings. In heterocellular cultures of MSCs and HL-1 cells the beating frequency was attenuated (t(0h): 2.26 ± 0.18 Hz; t(4h): 1.98 ± 0.26 Hz; P < 0.01) concomitant to the intercellular coupling between MSCs and cardiomyocytes. In HL-1 monolayers supplemented with MSC conditioned media (ConM) or tyrode (ConT) θ significantly increased in a time-dependent manner (ConT: t(0h): 2.4 cm/s ± 0.2; t(4h): 3.1 ± 0.4 cm/s), whereas the beating frequency remained constant. Connexin (Cx)43 mRNA and protein expression levels also increased after ConM or ConT treatment over the same time period. Enhanced low-density lipoprotein receptor-related protein 6 (LRP6) phosphorylation after ConT treatment implicates the Wnt signaling pathway. Suppression of Wnt secretion from MSCs (IWP-2; 5 μmol/l) reduced the efficacy of ConT to induce phospho-LRP6 and to increase θ. Inhibition of β-catenin (cardamonin; 10 μmol/l) or GSK3-α/β (LiCl; 5 mmol/l) also suppressed changes in θ, further supporting the hypothesis that MSC-mediated Cx43 upregulation occurs in part through secreted Wnt ligands and activation of the canonical Wnt signaling pathway.
authors.affiliation: Center for Cardiovascular Research, Department of Medicine, Section of Cardiology, University of Illinois at Chicago, Chicago, IL 60612, USA.
authors.forename: Shwetha
authors.initials: S
authors.lastname: Mureli
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Gans
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Bare
authors.forename: David L
authors.initials: DL
authors.lastname: Geenen
authors.forename: Nalin M
authors.initials: NM
authors.lastname: Kumar
authors.forename: Kathrin
authors.initials: K
authors.lastname: Banach
mesh_terms: D000818:Animals; D002460:Cell Line; D047188:Chalcones / Q000494:pharmacology; D018031:Connexin 43 / Q000096:biosynthesis*; D017077:Culture Media, Conditioned; D004791:Enzyme Inhibitors / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors; D000071679:Glycogen Synthase Kinase 3 beta; D006329:Heart Conduction System / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D018021:Lithium Chloride / Q000494:pharmacology; D060488:Low Density Lipoprotein Receptor-Related Protein-6 / Q000378:metabolism; D045164:Mesenchymal Stem Cell Transplantation; D051379:Mice; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D019899:Paracrine Communication / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D060449:Wnt Signaling Pathway / Q000187:drug effects / Q000502:physiology*; D051176:beta Catenin / Q000037:antagonists & inhibitors
chemical_list: C495267:CTNNB1 protein, mouse; D047188:Chalcones; D018031:Connexin 43; D017077:Culture Media, Conditioned; D004791:Enzyme Inhibitors; C543076:GJA1 protein, mouse; D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555476:Lrp6 protein, mouse; D051176:beta Catenin; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; C448021:glycogen synthase kinase 3 alpha; D018021:Lithium Chloride; C436747:cardamonin