title: Morphofunctional integration between skeletal myoblasts and adult cardiomyocytes in coculture is favored by direct cell-cell contacts and relaxin treatment.
abstract: The success of cellular cardiomyoplasty, a novel therapy for the repair of postischemic myocardium, depends on the anatomical integration of the engrafted cells with the resident cardiomyocytes. Our aim was to investigate the interaction between undifferentiated mouse skeletal myoblasts (C2C12 cells) and adult rat ventricular cardiomyocytes in an in vitro coculture model. Connexin43 (Cx43) expression, Lucifer yellow microinjection, Ca2+ transient propagation, and electrophysiological analysis demonstrated that myoblasts and cardiomyocytes were coupled by functional gap junctions. We also showed that cardiomyocytes upregulated gap junctional communication and expression of Cx43 in myoblasts. This effect required direct cell-to-cell contact between the two cell types and was potentiated by treatment with relaxin, a cardiotropic hormone with potential effects on cardiac development. Analysis of the gating properties of gap junctions by dual cell patch clamping showed that the copresence of cardiomyocytes in the cultures significantly increased the transjunctional current and conductance between myoblasts. Relaxin enhanced this effect in both the myoblast-myoblast and myoblast-cardiomyocyte cell pairs, likely acting not only on gap junction formation but also on the electrical properties of the preexisting channels. Our findings suggest that myoblasts and cardiomyocytes interact actively through gap junctions and that relaxin potentiates the intercellular coupling. A potential role for gap junctional communication in favoring the intercellular exchange of regulatory molecules, including Ca2+, in the modulation of myoblast differentiation is discussed.
authors.affiliation: Dept. of Anatomy, Univ. of Florence, Viale Morgagni 85, I-50134 Florence, Italy. formigli@unifi.it
authors.forename: Lucia
authors.initials: L
authors.lastname: Formigli
authors.forename: Fabio
authors.initials: F
authors.lastname: Francini
authors.forename: Alessia
authors.initials: A
authors.lastname: Tani
authors.forename: Roberta
authors.initials: R
authors.lastname: Squecco
authors.forename: Daniele
authors.initials: D
authors.lastname: Nosi
authors.forename: Lucia
authors.initials: L
authors.lastname: Polidori
authors.forename: Silvia
authors.initials: S
authors.lastname: Nistri
authors.forename: Laura
authors.initials: L
authors.lastname: Chiappini
authors.forename: Valentina
authors.initials: V
authors.lastname: Cesati
authors.forename: Alessandra
authors.initials: A
authors.lastname: Pacini
authors.forename: Avio M
authors.initials: AM
authors.lastname: Perna
authors.forename: Giovanni E
authors.initials: GE
authors.lastname: Orlandini
authors.forename: Sandra
authors.initials: S
authors.lastname: Zecchi Orlandini
authors.forename: Daniele
authors.initials: D
authors.lastname: Bani
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D018920:Coculture Techniques; D018031:Connexin 43 / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects / Q000378:metabolism; D047468:Immunoprecipitation; D007546:Isoquinolines; D051379:Mice; D018613:Microscopy, Confocal; D032448:Myoblasts, Skeletal / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D051381:Rats; D012065:Relaxin / Q000494:pharmacology
chemical_list: D018031:Connexin 43; D007546:Isoquinolines; D012065:Relaxin; C017475:lucifer yellow