NR4A1 and myocardial infarction: However, we further found that CD31-positive endothelial cells in the elevated NR4A1 group increased greatly at day 21 (0.193 ± 0.036 vs. 0.075 ± 0.019, p < 0.001) (Figure 5(a)), which indicated a very positive role of NR4A1 for myocardial repair after MI.