Cardiac stem cells (CSCs) are being evaluated for their efficacy in the treatment of heart failure. However, numerous factors impair the exogenously delivered cells' regenerative capabilities. Hypoxia is one stress that contributes to inadequate tissue repair. Here, we tested the hypothesis that hypoxia impairs cell proliferation, survival, and migration of human CSCs relative to physiological and room air oxygen concentrations. Human endomyocardial biopsy-derived CSCs were isolated, selected for c-Kit expression, and expanded in vitro at room air (21% O2). To assess the effect on proliferation, survival, and migration, CSCs were transferred to physiologic (5%) or hypoxic (0.5%) O2 concentrations. Physiologic O2 levels increased proliferation (P<0.05), but did not affect survival of CSCs. Although similar growth rates were observed in room air and hypoxia, a significant reduction of beta-galactosidase activity (-4203 fluorescent units, P<0.05), p16 protein expression (0.58-fold, P<0.001), and mitochondrial content (0.18-fold, P<0.001) in hypoxia suggests that transition from high (21%) to low (0.5%) O2 reduces senescence and promotes quiescence. Furthermore, physiologic O2 levels increased migration (P<0.05) compared to room air and hypoxia, and treatment with mesenchymal stem cell conditioned media rescued CSC migration under hypoxia to levels comparable to physiologic O2migration (2-fold, P<0.05 relative to CSC media control). Our finding that physiologic O2 concentration is optimal for in vitro parameters of CSC biology suggests that standard room air may diminish cell regenerative potential. This study provides novel insights into the modulatory effects of O2 concentration on CSC biology and has important implications for refining stem cell therapies.
- Cardiovascular progenitor/stem cells
- Regenerative medicine
- Cardiovascular disease
- Cell transplantation
- Copyright © 2016, American Journal of Physiology-Heart and Circulatory Physiology