CD44 and myocardial infarction: 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).