Introduction: Aging is accompanied by anatomical and physiological changes in most tissues and organs, especially the reduction of cells, tissues, and vascular levels. Endothelial progenitor cells are involved in maintaining endothelial health, preventing endothelial dysfunction, and increasing neovascularization process. Cardiac stem cells are effective in the regeneration and repair of heart tissue. Regular exercise training increases both of these cells. We aimed to investigate the effect of eight weeks of moderate and intense interval training on gene expression of endothelial progenitor cells and cardiac stem cells in aged rats.
 
Materials and Methods: Twenty-one Wistar female rats with the mean age of 24±1 months and the mean weight of 265±44 g were randomly divided into three groups of control (n=7), moderate exercise (n=7), and intense exercise (n=7) groups. Both exercise groups were trained for 8 weeks, 3 sessions a week, each session for 40 minutes with 28 meters per minute in the moderate intensity exercise group and 34 meters per minute in the high intensity group. Forty-eight hours after the last training session, the rats were anesthetized and their cardiac tissue was isolated. CD34 and KDR gene expression for endothelial progenitor cells and c-Kit expression for cardiac stem cells were measured.
 
 
 
Findings: The results showed that the level of c-Kit gene expression in both groups of moderate (P=0.0001) and intense (P=0.0001) training significantly increased compared to the control group. This increase was significantly higher in the intense training group (P=0.0001). Eight weeks of moderate interval training significantly increased the expression level of CD34 (P=0.0001) and KDR (P=0.0001) genes. Also, eight weeks of high intensity interval training resulted in a significant increase in the level of gene expression of CD34 (P=0.0001) and KDR (P=0.0001). This accumulative effect in the intense training group was significantly higher compared to the moderate group (CD34: P=0.0001 and KDR: P=0.0001).
 
Conclusion: The results of this study showed that regular interval training with two different intensity levels raises the level of gene expression of endothelial progenitor cells and cardiac stem cells. This increase is dependent on the intensity of training. High intensity interval training seems to stimulate the regeneration of heart tissue and development of coronary artery. These findings can be used to improve cell therapy and cardiac rehabilitation after injury and myocardial dysfunction, especially in the elderly.