Morphofunctional integration between skeletal myoblasts and adult cardiomyocytes in coculture is favored by direct cell-cell contacts and relaxin treatment

• Published in: American Journal of Physiology: Cell Physiology 2005-04, Vol.288 (4), p.C795-C804
• Main Authors: Formigli, Lucia, Francini, Fabio, Tani, Alessia, Squecco, Roberta, Nosi, Daniele, Polidori, Lucia, Nistri, Silvia, Chiappini, Laura, Cesati, Valentina, Pacini, Alessandra, Perna, Avio M, Orlandini, Giovanni E, Zecchi Orlandini, Sandra, Bani, Daniele
• Format: Article
• Language: English
• Subjects: Animals; Blotting, Western; Cell Communication - drug effects; Cell Communication - physiology; Cells, Cultured; Coculture Techniques; Connexin 43 - metabolism; Gap Junctions - drug effects; Gap Junctions - metabolism; Immunoprecipitation; Isoquinolines; Mice; Microscopy, Confocal; Myoblasts, Skeletal - drug effects; Myoblasts, Skeletal - metabolism; Myoblasts, Skeletal - ultrastructure; Myocytes, Cardiac - drug effects; Myocytes, Cardiac - metabolism; Myocytes, Cardiac - ultrastructure; Patch-Clamp Techniques; Rats; Relaxin - pharmacology
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00345.2004

Departments of 1 Anatomy, Histology, and Forensic Medicine and 2 Physiological Sciences, University of Florence; and 3 Experimental Surgery Unit, Careggi Hospital, Florence, Italy Submitted 16 July 2004 ; accepted in final form 15 October 2004 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 (C 2 C 12 cells) and adult rat ventricular cardiomyocytes in an in vitro coculture model. Connexin43 (Cx43) expression, Lucifer yellow microinjection, Ca 2+ 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 Ca 2+ , in the modulation of myoblast differentiation is discussed. gap junctions; connexin43 Address for reprint requests and other correspondence: L. Formigli, Dept. of Anatomy, Histology, and Forensic Medicine, Univ. of Florence, Viale Morgagni 85, I-50134 Florence, Italy (E-mail: formigli{at}unifi.it )