Abstract 3126: The Pattern, Quantity and Possible Mechanism of Migration of Bone Marrow Cells into the Myocardium after Intracoronary Injection
Background: Intracoronary injection of bone marrow mononuclear cells (BMMC) is the most widely used clinical protocol of cell therapy for treating heart failure. However, the efficiency and pattern of engraftment of BMMC into the myocardium and the mechanism for BMMC to adhere and/or cross the endothelium are largely unknown. It is hypothesized that such adhesion and/or migration takes place through a similar mechanism to the leukocyte-endothelial interaction where a set of distinct adhesion molecules play a role
Methods and Results: Wild-type mouse hearts were perfused under constant pressure with a modified Langendorff apparatus. One million BMMC from syngeneic GFP-transgenic mice were slowly injected into the coronary arteries of the perfused heart. The number of GFP+ cells in the coronary effluent was counted and the difference from the total cell number infused was regarded to be the number of BMMC entrapped (adhered or migrated) in the heart. The efficiency of entrapment in the intact heart was only 14.4±1.1%, which increased to 33.8±1.1% (n=8, p<0.001) by inducing 30-minute global ischemia followed by 30-minute reperfusion prior to cell injection. The majority of BMMC passing through the heart occurred within 2 minutes after injection. Coronary flow was not affected by BMMC injection. BMMC entrapment in ischemia-reperfused heart was markedly attenuated by injection of anti-P-selectin antibody (150 μg/kg) prior to cell injection (9.5±0.6%, p<0.001), but not by injection of anti-ICAM-1 antibody (200 μg/kg; 33.8±3.4%). Thirty minutes after cell injection, the hearts were enzymatically digested and the GFP+ cells entrapped in the heart were characterized by flow cytometry. The ratio of CD18 (ligand for ICAM-1) positive cells was 2-fold larger in entrapped BMMC compared to BMMC before injection (24.9±2.7%). Further, the ratio of Sca-1 positive cells was 8-fold larger in the entrapped BMMC compared to BMMC before injection (4.1±0.4%).
Conclusions: More than 60% of BMMC infused into the coronary arteries failed to be retained in the myocardium. Entrapment of BMMC was dependent on P-selectin, though ICAM-I was also involved via a different mechanism. Sca-1+ BMMC were preferentially entrapped within the myocardium.