Establishment of a long-surviving murine model of myocardial infarction: Qualitative and quantitative conventional microscopic findings during pathological evolution

Ongoing basic molecular analyses are being performed in mice, and a simple long-surviving murine model of myocardial infarction (MI) would be very use ful in this regard. Although a few studies have induced hll in mice by coro nary artery ligation, the induction involves a complex technique and has a relatively high mortality rate. In addition, the identification of the basi c pathological sequence is essential to the interpretation of experimental results. We developed a simple technique for the induction of MI in mice an d examined qualitative and quantitative conventional microscopic findings d uring the pathological evolution over a 28-day observation period, Male BAL B/c mice weighing approximately 25 - 30 g were anesthetized and then ventil ated with a positive pressure ventilator. The heart was exposed by thoracot omy. Left coronary artery occlusion was performed by thermocoagulation usin g a thermocoagulation knife at the level of the tip of the left atrium, Aft er establishing this surgical method, we used it to induce hll in 71 mice. The operative and postoperative mortality rates of this model were 5.6 % (4 /71) and 12.6% (9/71), respectively. In 3 (5.2 %) of the 58 surviving mice, the area of infarct was not sufficient. The infarct area in the remaining 55 mise was 40 +/- 9 % of the entire perimeter of the left ventricle. Conve ntional microscopic examinations with hematoxylin-eosin and Masson-trichrom e staining disclosed that all of the characteristic histopathological featu res of MI occurred 1 - 2 days earlier than those in rats. Our surgical tech nique provides a sufficient infarct area. with an acceptable mortality rate . The present study clarified the histopathological sequence in this long s urviving murine MI model.