Abstract 1013: Depleting Bone Marrow Mononuclear Cells of Apoptotic Cells Improves Efficiency of Cell Therapy in a Rabbit Model of Myocardial Infarction.
Purpose: Although associated with interesting preliminary results, the efficiency of cardiac cell therapy is limited by high rate of early death of engrafted cells. We hypothesized that the presence of apoptotic cells could play a role in this issue. The aim of this study was to quantify the number of apoptotic cells among bone marrow mononuclear cells (BMMC) and to analyse their impact on left ventricular (LV) function and remodelling in a rabbit model of cell therapy for myocardial infarction (MI).
Methods and results: The rate of apoptotic cells among BMMC was measured by flow cytometry after Annexin V labelling. Depletion of apoptotic BMMC was performed using Annexin V labelled-magnetic microbeads. Cell survival was determined in vitro and functional impact determined in vivo. MI was induced by 1 hour ischemia-reperfusion. Seven days later, injection of placebo (n=4), unselected BMMC (ApoHigh n=4) or apoptotic cell depleted BMMC (ApoLow n=4) was performed in the infarct area. Two months later, MI scar size was analysed by histology. LV remodelling and LVEF were analysed by echocardiography. The rate of Apoptotic cells among BMMC was 33.9% [27.3%–39.5%] (=ApoHigh) as compared to 17.3% [12.5%–24.4%] after depletion (=ApoLow, p<0.001). In vitro assays revealed that hypoxia-induced cell death was markedly increased in ApoHigh as compared to ApoLow BMMC (1.15.106 [1.08 –1.22] vs. 0.92.106 [0.9 – 0.95], p=0.04). The impact of depletion of apoptotic BMMC on cardiac function is presented in the table⇓ below. Injection of ApoHigh BMMC decreased scar size by 18%, LV dilatation by 7% and increased LVEF by 6% as compared to placebo. Injection of ApoLow BMMC further decreased scar size by 20%, LV dilatation by 13% and further increased LVEF by 16% as compared to ApoHigh BMMC.
Conclusion: Rabbit BMMC contain about one third of apoptotic cells. Depletion of apoptotic cells significantly improves BMMC therapy efficiency. It remains to be seen whether similar results are observed in humans.