Abstract 1068: Non-invasive Tracking of Cells and Monitoring of In Situ pO2 during Engraftment of Skeletal Myoblasts in Infarct Mouse Heart
One of the major limitations of cell-based therapies for the treatment of ischemic heart disease has been the inability to monitor the distribution of the implanted cells and their effect on the local tissue oxygen concentration (pO2) over a long term. The goal of this study was to use an EPR (electron paramagnetic resonance)-detectable oxygen-sensing nanoparticulate probe (LiNc-BuO) to label skeletal myoblasts (SM) and to monitor the cell migration as well as in situ pO2 in the infarct myocardium for several weeks post-implantation.
Methods: Myocardial infarction was created by ligation of the LAD artery in mice. Mouse SM (75% purity, CD56+ cells by FACS) were labeled with the probe by incubating in culture for 72 h. A single intra-myocardial injection of the labeled SM (10 μl, 1x105 cells) was given using a 29½-guage needle in the infarct region. The retention and redistribution of the injected cells and in situ myocardial pO2 were monitored by EPR. Immuno-histological studies of the skeletal muscle-specific marker, MY-32, were used at different time periods during engraftment.
Results: The EPR signals obtained in mouse hearts implanted with the labeled SM cells clearly established the retention of the probe at the site of implantation for up to 4 weeks. The differentiation of the SM into skeletal muscle cells were confirmed by MY-32 staining starting 1 week after implantation. The baseline myocardial pO2 was 15.8±1.2 mmHg (n=6). Immediately after permanent LAD ligation, the tissue pO2 in the ischemic region decreased to 1.7±0.7 mmHg. The myocardial pO2 immediately after the cell therapy was 2.5±1.0 mmHg. The pO2 was significantly higher at 1, 2, and 3 weeks (Table 1⇓) after SM cell therapy.
Conclusion: The studies clearly established our ability to track the SM cell engraftment, in vivo and showed increased pO2 levels at the therapeutic site.