Effect of Tβ4 shRNA on eEPC-mediated cardioprotection in vivo. A, Example of infarct size (percentage of AAR) 24 hours after ischemia and retroinfusion of 5×106 eEPCs with Tβ4 shRNA. B, Quantification revealed a significant decrease in infarct size after eEPC retroinfusion with or without scrambled (s.c.) shRNA (n=9 per group; #P<0.01 vs control). C, AAR/left ventricle (LV) did not differ significantly between groups. D, Subendocardial segment shortening (SES) in the apical LAD perfused region (percentage of the nonischemic right circumflex region) at rest and at 120- and 150-bpm atrial pacing (n=9 per group; §P<0.05 vs control; #P<0.05 vs control and eEPC plus Tβ4 shRNA). E, Contraction velocity (dP/dtmax) at the given heart rates (P=0.052, 2-way ANOVA).