Abstract 13832: Cardiac Mesenchymal Cells (CMCs) Cultured at Physiologic Oxygen Tension Have Superior Therapeutic Efficacy in Mice With Heart Failure Caused by Myocardial Infarction

Abstract

Stem/progenitor cells are usually cultured at atmospheric O 2 tension (21%); however, since physiologic O 2 tension in the heart is ~5%, using 21% O 2 may cause oxidative stress and toxicity. CMCs, a newly-discovered and promising type of progenitor cells, are effective in improving LV function after myocardial infarction (MI). To determine if 5% O 2 enhances therapeutic efficacy of CMCs, murine CMCs were cultured at 21% or 5% O 2 . Compared with 21% O 2 , culture at 5% O 2 significantly ( P <0.001) increased cell proliferation, telomerase activity, telomere length, and resistance to severe hypoxia (1% O 2 for 24 h) in vitro . Then, LV dysfunction was produced in 48 mice by a 60 min MI; 30 days later, mice received vehicle or CMCs cultured at 21% O 2 or 5% O 2 . After 35 days, the improvement in LV ejection fraction effected by 5% O 2 CMCs was >3 times greater than by 21% O 2 CMCs (5.2 vs. 1.5 units, P <0.01) (Figs. A-B). Hemodynamic studies (Millar catheter) yielded similar results both for load-dependent (LV dP/dt) and load-independent (end-systolic elastance) indices (Figs. C-D). Thus, 2 independent methods (echo and hemodynamics) demonstrated that compared with 21% O 2 , using 5% O 2 to culture CMCs results in greater functional improvement in the failing heart. Further, 5% O 2 CMCs produced greater reduction in myocardial fibrosis and exhibited much longer survival after transplantation ( P <0.01 for both). In conclusion, culturing CMCs at physiologic (5%) O 2 tension results in more rapid proliferation (reducing time and cost to achieve target cell numbers), less senescence, greater resistance to severe hypoxia (making cells better able to survive in scarred regions where O 2 is very low [1-2%]), and superior therapeutic efficacy in promoting cardiac repair after MI. Thus far, almost all preclinical and clinical studies of cell therapy have used 21% O 2 to culture cells. Our data challenge this paradigm and support the need to change the methods used to culture CMCs and possibly other progenitor cells.