It was demonstrated that physiological ischemia training increased EPCs in the ischemic limb. However, what about the EPCs levels in the rabbits with myocardial ischemia under physiological ischemia training? We checked and traced endogenous endothelial progenitor cells (EPCs) during physiological ischemia training.

Rabbits were randomly divided into 4 groups: a myocardial ischemia group (subjected to myocardial ischemia only); a physiological ischemia training group (subjected to physiological ischemia training only); a physiological ischemia training-myocardial ischemia group (subjected to both myocardial ischemia and physiological ischemia training); and a sham-operated group. Myocardial ischemia was induced experimentally by a 2-min ischemia, followed by a 1-h reperfusion. Physiological ischemia training involved a 4-min isometric contraction elicited by electrical stimulation (biphase square wave, 40 Hz, 1 ms), which generated a contraction force at 40% of the maximal isometric contraction force. Myocardial ischemia and/or physiological ischemia training were performed twice a day, 5 days a week for 4 weeks. EPCs were counted by FACS and traced by double-labelling with super paramagnetic iron oxide and chloromethyl-benzamidodialkylcarbocyanine.

EPC levels in the blood and the ischemic heart region both improved significantly in the physiological ischemia training-myocardial ischemia group [mean 0.046% (standard deviation [SD] 0.007), 0.013% (SD 0.005)] and group myocardial ischemia [mean 0.038% (SD 0.016), 0.008% (SD 0.004)]. The dual-labelled EPCs in the ischemic heart region were confirmed. Pearson's analysis demonstrated that there is a positive correlation between EPC levels in the blood and the heart region ( P < 0.05) in the physiological ischemia training-myocardial ischemia group.

Physiological ischemia training can effectively improve endogenous EPCs. Their homing process from the circulating blood to the ischemic myocardium was clearly traced in this study. This homing process is of great importance for remote neovascularization.