Genetic deletion of Fas receptors or Fas ligands does not reduce infarct size after acute global ischemia-reperfusion in isolated mouse heart

Apoptosis has been shown in cardiac cells under divergent physiological and pathological conditions. However, there has been an ongoing debate upon the relative contribution of cardiomyocyte apoptosis to the myocardial infarct size after ischemia-reperfusion (I-R) injury. We tested the hypothesis that blocking the death receptor pathway of apoptosis through genetic deletion of Fas receptors or Fas ligands would reduce myocardial infarct size caused by acute I-R injury. The hearts isolated from Fas receptor or Fas ligand knockout (KO) mice as well as the C57BL/6j wild-type control mice (N = 6-8 per group) were subjected to 20 min of global ischemia and 30 min of reperfusion in Langendorff mode. Our results show that the infarct size, determined with triphenyltetrazolium chloride staining, was not significantly different between the three groups (i.e., 30.2 +/- 3.9% for wild-type controls, 30.0 +/- 2.1% for Fas ligand KOs, and 23.8 +/- 3.6% for Fas receptor KOs; mean SEM, p > 0.05). Postischemic leakage of lactate dehydrogenase, another marker of necrotic cellular injury, also was not significantly different between these groups (p > 0.05). In addition, postischernic ventricular contractile function as well as coronary flow were similar for all the experimental groups (p > 0.05). In conclusion, contrary to our original hypothesis, the present study in the gene KO mice suggests that the Fas ligand- and Fas receptor-mediated death receptor pathway of apoptosis is not the primary determinant of myocardial infarct size and ventricular dysfunction caused by acute global I-R injury in the isolated perfused mouse heart.