Measurement of oxygenation at the site of stem cell therapy in a murine model of myocardial infarction

We have developed a noninvasive EPR (electron paramagnetic resonance) oximetry, based on a new class of oxygen-sensing nano-particulate probe (LiNc-BuO), for simultaneous monitoring of stem-cell therapy and in situ oxygenation (partial pressure of oxygen, pO(2)) in a mouse model of acute myocardial infarction (AMI). AMI was induced by a permanent occlusion of left-anterior-descending (LAD) coronary artery. Skeletal myoblast (SM) cells were used for therapy. The oximetry probe was implanted in the mid-ventricular region using a needle. Tissue histological studies after 3 weeks of implantation of the probe revealed significant fibrosis, which was solely due to the needle track and not due to the probe particles. The feasibility of long-term monitoring of pO(2) was established in control (non-infaret) group of hearts (> 3 months; pO(2) = 15.0 +/- 1.2 mmHg,). A mixture of the probe with/without SM cells (1 x 10(5)) was implanted as a single injection in the infarcted region and the myocardial tissue pO(2) at the site of cell therapy was measured for 4 weeks. The pO(2) was significantly higher in infarcted hearts treated with SM cells (pO(2) = 3.5 +/- 0.9 mmHg) compared to untreated hearts (pO(2) = 1.6 +/- 0.7 mmHg). We have demonstrated, for the first time, the feasibility of monitoring pO(2) in mouse hearts after stem cell therapy.