To further investigate the influence of CD44 in angiogenesis in myocardial ischemic injury, endothelial marker CD31 immunofluorescence staining was performed and revealed that CD44 KO hearts had a lower density of capillaries in the border zone than WTMI hearts 1 week after MI (Fig. 2E, F), with excluding the potential impact of endothelial cell apoptosis in CD31 density and fluorescence intensity (Fig. 2G). This evidence concerns the gene PECAM1 and myocardial infarction.