Myocardial Production and Release of Stem Cell Factor Following Myocardial Infarction

Background: Stem cell homing to the heart is mediated by the release of chemo-attractant cytokines, including stem cell factor (SCF). SCF is detectable in peripheral blood in patients early after myocardial infarction (MI). However, whether the increased circulating SCF in these patients is released from the heart or another source remains unknown. Methods: Murine hearts were studied for the expression of SCF at day 3 following MI. The coronary artery and coronary sinus (venous) blood from patients following MI was used to determine whether SCF is released from the heart into the systemic circulation following MI. Patients with normal coronary arteries, stable coronary artery disease (CAD) and unstable angina served as controls. Results: In mice, SCF mRNA was constitutively expressed in the left ventricular myocardium at baseline. Following MI, SCF expression was suppressed in the infarct zone and border zone, but unchanged in the myocardium remote from the MI. In humans, SCF was not released from the heart at baseline, but was increased in response to MI. Interestingly, SCF was also released from the heart in stable CAD and in unstable angina without infarction. However, there was no significant correlation between the heart release of SCF and myocardial damage, and human cardiac release of SCF did not change with time following MI. Conclusions: Release of SCF from the heart into the circulation is increased in humans in all stages of CAD. Myocardial damage, per se, does not result in increased release of SCF into the circulation. This is consistent with the mouse model where SCF production does not increase after MI. Our findings suggest that the damaged myocardium does not contribute to human cardiac release of SCF.