Bmi‐1 high‐expressing cells enrich cardiac stem/progenitor cells and respond to heart injury

Bmi‐1 gene is well recognized as an oncogene, but has been recently demonstrated to play a role in the self‐renewal of tissue‐specific stem cells. By using Bmi‐1(GFP) (/+) mice, we investigated the role of Bmi‐1 in cardiac stem/progenitor cells and myocardial repair. RT‐PCR and flow cytometry analysis indicated that the expression of Bmi‐1 was significantly higher in cardiac side population than the main population from CD45(−)Ter119(−) CD31(−) heart cells. More Sca‐1(+) cardiac stem/progenitor cells were found in Bmi‐1 GFP (hi) subpopulation, and these Bmi‐1 GFP (hi) heart cells showed the potential of differentiation into SMM (+) smooth muscle‐like cells and TnT(+) cardiomyocyte‐like cells in vitro. The silencing of Bmi‐1 significantly inhibited the proliferation and differentiation of heart cells. Otherwise, myocardial infarction induced a significantly increase (2.7‐folds) of Bmi‐1 GFP (hi) population, mainly within the infarction and border zones. These preliminary data suggest that Bmi‐1(hi) heart cells are enriched in cardiac stem/progenitor cells and may play a role in myocardial repair.