Comparison of the effects of fetal cardiomyocyte and skeletal myoblast transplantation on postinfarction left ventricular function

Objectives: Transplantation of fetal cardiomyocytes improves function of in farcted myocardium but raises availability, immunologic, and ethical issues that justify the investigation of alternate cell types, among which skelet al myoblasts are attractive candidates. Methods: Myocardial infarction was created in rats by means of coronary art ery ligation. One week later, the animals were reoperated on and intramyoca rdially injected with culture growth medium alone (controls, n = 15), fetal cardiomyocytes (5 x 10(6) cells, n = 11), or neonatal skeletal myoblasts ( 5 x 106 cells, n = 16). The injections consisted of a 150-mu L volume and w ere made in the core of the infarct, and the animals were immunosuppressed. Left ventricular function was assessed by echocardiography immediately bef ore transplantation and 1 month thereafter. Myoblast-transplanted hearts we re then immunohistologically processed for the expression of skeletal muscl e-specific embryonic myosin heavy chain and cardiac-specific connexin 43. Results: The left ventricular ejection fraction markedly increased in the f etal and myoblast groups from 39.3% +/- 3.9% to 45% +/- 3.4% (P = .086) and from 40.4% +/- 3.6% to 47.3% +/- 4.4% (P = .034), respectively, whereas it decreased in untreated animals from 40.6% +/- 4% to 36.7% +/- 2.7%. Transp lanted myoblasts could be identified in all animals by the positive stainin g for skeletal muscle myosin. Conversely, clusters of connexin 43 were not observed on these skeletal muscle cells. Conclusions: These results support the hypothesis that skeletal myoblasts a re as effective as fetal cardiomyocytes for improving postinfarction left v entricular function. The clinical relevance of these findings is based on t he possibility for skeletal myoblasts to be harvested from the patient hims elf.