Myocardial Layer-Specific Effect of Myoblast Cell-Sheet Implantation Evaluated by Tissue Strain Imaging

BACKGROUND: The implantation of skeletal myoblast (SMB) cell-sheets over the damaged area of a myocardial infarction (MI) has been shown to improve global left ventricular (LV) function through a paracrine effect. However, the regeneration process has not been fully evaluated. We hypothesized that the use of tissue Doppler strain M-mode imaging to assess myocardial layer-specific strain might enable detailed visual evaluation of the regenerative ability of SMBs. METHODS AND RESULTS: SMBs were cultured on temperature-responsive culture dishes to generate cell-sheets. At 4 weeks after inducing anterior MI, the animals were divided into 2 groups: SMB cell-sheet implantation and sham operation (n=6 in each). A total of 30 cell-sheets (1.5×10(7) cells/sheet) were placed on the epicardium, covering the infarct and border regions. Subendocardial and subepicardial strain values were measured in the infarct, border, and remote regions by tissue Doppler strain analysis. SMB cell-sheet implantation produced the following major effects: progression of LV remodeling was prevented and global LV ejection fraction increased; the subendocardial strain was significantly greater than the subepicardial strain in the treated border region; vascular density in the subendocardium was significantly higher than in the subepicardium in the treated region; the expression of vascular endothelial growth factor was significantly increased. CONCLUSIONS: Tissue Doppler strain analysis allows precise evaluation of the effect of cell-sheet implantation on layer-specific myocardial function.