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 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 subpopulation, and these Bmi-1 GFP 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 population, mainly within the infarction and border zones. These preliminary data suggest that Bmi-1 heart cells are enriched in cardiac stem/progenitor cells and may play a role in myocardial repair.