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This placebo-controlled, double-blind trial compared the hemodynamic effects of sotalol and quinidine with the use of rest and exercise gated radionuclide angiography. Patients

Background and aims Omega-3 fatty acids suppress Thromboxane A2 (TxA2) generation via mechanisms independent to that of aspirin therapy. We sought to evaluate whether baseline omega-3 fatty acid levels influence arachidonic acid proven platelet-cyclooxygenase-1 (COX-1) independent TxA2 generation (TxA2 generation despite adequate aspirin use). Methods and results Subjects with acute myocardial infarction, stable CVD or at high risk for CVD, on adequate aspirin therapy were included in this study. Adequate aspirin action was defined as complete inhibition of platelet-COX-1 activity as assessed by <10% change in light transmission aggregometry to ≥1 mmol/L arachidonic acid. TxA2 production was measured via liquid chromatography–tandem mass spectrometry for the stable TxA2 metabolite 11-dehydro-thromboxane B2 (UTxB2) in urine. The relationship between baseline fatty acids, demographics and UTxB2 were evaluated. Baseline omega-3 fatty acid levels were not associated with UTxB2 concentration. However, smoking was associated with UTxB2 in this study. Conclusion Baseline omega-3 fatty acid levels do not influence TxA2 generation inpatients with or at high risk for CVD receiving adequate aspirin therapy. The association of smoking and TxA2 generation, in the absence of platelet COX-1 activity, among aspirin treated patients warrants further study.

Stem/progenitor cells are usually cultured at atmospheric O2 tension (21%); however, since physiologic O2 tension in the heart is ∼5%, using 21% O2 may cause oxidative stress and toxicity. Cardiac mesenchymal cells (CMCs), a newly discovered and promising type of progenitor cells, are effective in improving left ventricle (LV) function after myocardial infarction (MI). We have previously shown that, compared with 21% O2, culture at 5% O2 increases CMC proliferation, telomerase activity, telomere length, and resistance to severe hypoxia in vitro. However, it is unknown whether these beneficial effects of 5% O2in vitro translate into greater therapeutic efficacy in vivo in the treatment of heart failure. Thus, murine CMCs were cultured at 21% or 5% O2. Mice with heart failure caused by a 60-min coronary occlusion followed by 30 days of reperfusion received vehicle, 21% or 5% O2 CMCs via echocardiography-guided intraventricular injection. After 35 days, the improvement in LV ejection fraction effected by 5% O2 CMCs was &gt; 3 times greater than that afforded by 21% O2 CMCs (5.2 vs. 1.5 units, P &lt; 0.01). Hemodynamic studies (Millar catheter) yielded similar results both for load-dependent (LV dP/dt) and load-independent (end-systolic elastance) indices. Thus, two independent approaches (echo and hemodynamics) demonstrated the therapeutic superiority of 5% O2 CMCs. Further, 5% O2 CMCs, but not 21% O2 CMCs, significantly decreased scar size, increased viable myocardium, reduced LV hypertrophy and dilatation, and limited myocardial fibrosis both in the risk and non-infarcted regions. Taken together, these results show, for the first time, that culturing CMCs at physiologic (5%) O2 tension provides superior therapeutic efficacy in promoting cardiac repair in vivo. This concept may enhance the therapeutic potential of CMCs. Further, culture at 5% O2 enables greater numbers of cells to be produced in a shorter time, thereby reducing costs and effort and limiting cell senescence. Thus, the present study has potentially vast implications for the field of cell therapy.

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.

A major obstacle to using cell therapy for heart failure is the poor survival of transplanted cells. We have found that CMCs (a promising type of reparative cells) grown at 5% O 2 (the physiologic O 2 tension in the heart) are more resistant to severe hypoxia in vitro than CMCs grown at 21% O 2 , but the survival of these cells in vivo is unknown. Thus, female mice subjected to a 60-min coronary occlusion and 30 days of reperfusion received 1x10 6 male CMCs cultured at 21% O 2 or 5% O 2 (21%O 2 CMCs or 5%O 2 CMCs) via echo-guided injection into the LV cavity. Quantitative real-time PCR for single copy of a Y-chromosome-specific Sry gene sequence was performed using genomic DNA isolated from heart (right ventricle [RV], risk region [RR] and non-risk region [NR] of LV), lung, liver, spleen and kidney 24 h or 7 days after cell administration (Figure). Compared with 21% O 2 CMCs, culture at 5% O 2 markedly increased cell retention in RR > NR > RV at 24 h and up to 7 days after CMC administration (Figs. C-D). At 24 h, although 25% of all transplanted cells were present in the liver (Fig. E), the number of Sry + cells per mg of tissue was strikingly greater in RR (2131±248) > NR (1447±250) > RV (1047±156) compared with liver (274±131, P <0.01) and kidney (619±140, P <0.05) (n=6/group). These differences persisted up to 7 days (820±156 in RR, 667±156 in NR, 327±33 in RV vs. 103±45 in liver, P <0.01; 179±50 in kidney, P <0.05) (n=4-5/group). In summary, we provide a systematic, time-dependent, and highly quantitative analysis of cell retention and distribution after infusion of CMCs into the LV cavity of failing hearts. The results demonstrate that, compared with 21% O 2 , physiologic 5% O 2 tension greatly enhances the retention of CMCs in the heart at 24 h and 7 days after cell transplantation, especially in the scarred regions where O 2 is very low (1-2%). Thus, culture at 5% O 2 may improve the reparative properties of CMCs (and possibly other cell types) used for cell therapy, providing an approach that may be applicable in the clinic.