title: Skeletal myoblasts overexpressing relaxin improve differentiation and communication of primary murine cardiomyocyte cell cultures.
abstract: The possibility that resident myocardial progenitor cells may be re-activated by transplantation of exogenous stem cells into the post-infarcted heart has been suggested as a possible mechanism to explain the heart's functional improvement after stem cell therapy. Here we studied whether differentiation of mouse neonatal immature cardiomyocytes in vitro was influenced by mouse skeletal myoblasts C2C12, wild type or engineered to secrete the cardiotropic hormone relaxin. The cultured cardiomyocytes formed spontaneously beating clusters and temporally exhibited cardiac immunophenotypical (cKit, atrial natriuretic peptide, troponin T, connexin-43, HCN4) and electrical features (inward voltage-dependent Na(+), T- and L-type Ca(2+) currents, outward and inward K(+) currents, I(f) pacemaker current). These clusters were functionally connected through nanotubular structures and undifferentiated cardiac cells in the form of flattened stripes, bridging the clusters through connexin-43-containing gap junctions. These findings suggested the existence of long distance cell-to-cell communications among the cardiomyocyte aggregates involved in the intercellular transfer of Ca(2+) signals and organelles, likely required for coordination of myocardial differentiation. Co-presence of the myoblasts greatly increased cardiomyocyte differentiation and the amount of intercellular connections. In fact, these cells formed a structural support guiding elongation of nanotubules and stripe-like cells. The secretion of relaxin by the engineered myoblasts accelerated and enhanced the cardiomyogenic potential of the co-culture. These findings underscore the possibility that grafted myoblasts and cardiotropic factors, such as relaxin, may influence regeneration of resident immature cardiac cells, thus adding a tile to the mosaic of mechanisms involved in the functional benefits of cell transplantation for cardiac repair.
authors.affiliation: Department of Anatomy, Histology and Forensic Medicine, University of Florence, viale G. 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: Silvia
authors.initials: S
authors.lastname: Nistri
authors.forename: Martina
authors.initials: M
authors.lastname: Margheri
authors.forename: Giorgia
authors.initials: G
authors.lastname: Luciani
authors.forename: Fabio
authors.initials: F
authors.lastname: Naro
authors.forename: Josh D
authors.initials: JD
authors.lastname: Silvertown
authors.forename: Sandra Zecchi
authors.initials: SZ
authors.lastname: Orlandini
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Meacci
authors.forename: Daniele
authors.initials: D
authors.lastname: Bani
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002450:Cell Communication; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D018031:Connexin 43 / Q000378:metabolism; D055724:Electrophysiological Phenomena; D016130:Immunophenotyping; D015640:Ion Channel Gating; D051379:Mice; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000378:metabolism / Q000648:ultrastructure; D012065:Relaxin / Q000378:metabolism*; D013997:Time Factors
chemical_list: D018031:Connexin 43; D012065:Relaxin