Establishment of chronic myocardial infarction model with minimally invasive methods in mice

AIM:To establish a chronic myocardial infarction model with minimally invasive methods in mouse and to provide a model for observing effects of stem cell transplantation on infarcted heart. METHODS: Seventy mice were randomly divided into six groups: five operation groups and one sham operation group. A 1-cm incision was made 0.8 cm away from the left side of sternum with the operated mice group. The fourth and fifth intercostal space was exposed via blunt dissection and the heart was squeezed out through the intercostal space. The left anterior descending coronary artery was ligated using #5 suture, and the heart was then returned to the chest. The incision was sutured in a purse-string manner. The left anterior descending coronary artery of mice of the sham operation group did not ligate. General shapes, electrocardiogram and morphologic changes of the heart were observed postoperatively in each group. RESULTS: The color of the infarct area was dark brown, which became translucent after perfusion of a fixative solution. During the first 30 min after LAD ligation, elevation of ECG ST-segment was >0.2 mV. Pathologic Q wave and lowering ST-segment appeared 3 days after ligation. Pathological section suggested infiltration of many inflammatory cells and broken cardiomyocytes 3 or 5 days after ligation. The changes were more obvious 5 days after ligation. Ruptured or lysed myofibers, necrosis of myocardiac cells, and infiltration of fewer inflammatory cells were observed 7 or 14 days after the ligation. The infarcted area was replaced by fibrous tissue 21 days after ligation. CONCLUSION: The model of myocardial infarction in mice is successfully established via a minimally invasive method. The model we introduced in this experiment is time-saving, stable and easily repeatable.