Effects of Detraining Followed by Aerobic Exercise on Cardiac Stem Cells in Aged Male Rats

Abstract

Introduction: The regenerative potential of cardiac stem and progenitor cells is affected by aging and detraining, with the C-Kit cardiac stem cell expressing the Nkx2.5 transcription factor playing a crucial role. Exercise is known to enhance organ regeneration during aging, but the mechanisms involved in new cardiomyocyte formation during physiological cardiac remodeling remain unclear. Material & Methods: Eighteen aged Wistar rats (~440g) were divided into three groups: Control (CO), aerobic training (AT) (5 days per week, 50-75% of maximum speed) for six weeks, and detraining (DT) for four weeks. RT-PCR analysis determined Nkx2.5 gene expression, while immunohistochemical staining identified C-kit-positive and Ki67-positive cardiac progenitor cells. Results: In heart tissue, C-Kit and Ki67 values significantly differed between the control–training (P=0.001) and training-detraining (P=0.001) groups but not between the control and detraining groups for C-Kit (P=0.502) and Ki67 (P=0.475). Nkx2.5 exhibited a significant difference between control-training (P=0.001), training-detraining (P=0.001), and control-detraining (P=0.006). Conclusion: Exercise increased the proliferation of heart stem cells, activating C-Kit differentiation and elevating Nkx2.5 expression, thereby delaying the effects of aging. However, detraining significantly impacted heart stem cell function, emphasizing the importance of sustained exercise for optimal cardiac health.

Keywords

• physical activity
• aging process
• physical deconditioning
• myocardial regeneration
• stem cells