Development of an in vivo ischemia-reperfusion model in heterotopically transplanted rat hearts

BACKGROUND: Heart transplantation has been extensively used in animal models, including studies on gene therapy for myocardial preservation. We investigated the feasibility of in situ left coronary artery (LCA) ligation as a physiological system for the examination of strategies to modulate myocardial tolerance against ischemia-reperfusion injury, such as gene therapy, using heterotopically transplanted rat hearts. METHODS: Lewis rat hearts that had been transplanted into syngeneic recipients' abdomens were subjected to 30-min ischemia, by occluding the LCA, and subsequent blood reperfusion by releasing the suture in situ (I/R group). Transplanted hearts in the sham group underwent laparotomy only. RESULTS: At 24 hr of reperfusion, the size of the ischemic region was 40.1+/-3.1% of the total left ventricular mass, and the infarct size was 47.5+/-3.3% of the area at risk in the I/R group. Cardiac function was reduced in the I/R group compared with the sham group, associated with higher myeloperoxidase activity (5.12+/-1.35 vs. 0.97+/-0.33 U/g wt) and higher incidence of apoptosis as defined by TUNEL (29.8+/-3.2 vs. 3.8+/-0.7%) and DNA ladder. In the I/R group, up-regulation of Bax, Bak, and caspase-3 was observed. CONCLUSIONS: These data on myocardial damage of transplanted hearts are consistent and equivalent to those of the usual LCA occlusion model, suggesting that this method is useful to investigate strategies for modulating myocardial tolerance against ischemia-reperfusion injury using heterotopically transplanted rat hearts in a more physiological blood-perfused model.