Evidence for fusion between cardiac and skeletal muscle cells.
Cardiomyoplasty with skeletal myoblasts may benefit cardiac function after infarction. Recent reports indicate that adult stem cells can fuse with other cell types. Because myoblasts are "fusigenic" cells by nature, we hypothesized they might be particularly likely to fuse with cardiomyocytes. To test this, neonatal rat cardiomyocytes labeled with LacZ and green fluorescent protein (GFP) were cocultured with unlabeled C2C12 myoblasts. After 3 days, we observed a small population of skeletal myotubes that expressed LacZ and GFP, indicating cell fusion. To test whether such fusion occurred in vivo, LacZ-expressing C2C12 myoblasts were grafted into normal nude mouse hearts. At 2 weeks after grafting, cells at the graft-host interface expressed both LacZ and cardiac-specific myosin light chain 2v (MLC2v). To test more definitively whether fusion between skeletal and cardiac muscle could occur, we used a Cre/lox reporter system that activated LacZ only upon cell fusion. When neonatal cardiomyocytes from -myosin heavy chain promoter (-MHC)-Cre mice were cocultured with myoblasts from floxed-lacZ reporter mice, LacZ was activated in a subset of cells, indicating cell fusion occurred in vitro. Finally, we grafted the floxed-lacZ myoblasts into normal hearts of -MHC-Cre+ and -MHC-Cre- mice (n=5 each). Hearts analyzed at 4 days and 1 week after transplantation demonstrated activation of LacZ when the skeletal muscle cells were implanted into hearts of -MHC-Cre+ mice, but not after implantation into -MHC-Cre- mice. These data indicate that skeletal muscle cell grafting gives rise to a subpopulation of skeletal-cardiac hybrid cells with a currently unknown phenotype. The full text of this article is available online at http://circres.ahajournals.org.
Reinecke
Hans
H
Department of Pathology, University of Washington, Box 357470, HSB Room D-514. Seattle, Wash 98195-7470, USA. hreineck@u.washington.edu
Minami
Elina
E
Poppa
Veronica
V
Murry
Charles E
CE
D000818:Animals; D000831:Animals, Newborn; D002459:Cell Fusion; D002478:Cells, Cultured / Q000166:cytology; D018920:Coculture Techniques; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006822:Hybrid Cells / Q000737:chemistry / Q000166:cytology; D007763:Lac Operon; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008819:Mice, Nude; D018485:Muscle Fibers, Skeletal / Q000166:cytology*; D032446:Myoblasts / Q000637:transplantation; D032383:Myocytes, Cardiac / Q000166:cytology*; D018995:Myosin Heavy Chains / Q000235:genetics; D011401:Promoter Regions, Genetic; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000032:analysis; D011995:Recombination, Genetic; D024723:Ventricular Myosins / Q000235:genetics; D001616:beta-Galactosidase / Q000032:analysis
D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D001616:beta-Galactosidase; D024723:Ventricular Myosins; D018995:Myosin Heavy Chains