Background: Myocardial regeneration after myocardial infarction can occur via stem cell recruitment. Stromal cell-derived factor 1alpha (SDF-1alpha) has been shown to be critical for stem cell homing to injured tissue.
Methods: Myocardial infarction was induced in pigs via microembolization of the distal left anterior descending artery. Two weeks after myocardial infarction animals underwent catheter-based transendocardial injection of SDF-1alpha into the periinfarct myocardium (18 injections, 5 ìg per injection) (n = 12) or sham-intervention (n = 8). Tc99m sestamibi single-photon emission computed tomography (SPECT) and electromechanical mapping (EMM) of the left ventricle were performed two and seven weeks after myocardial infarction.
Results: Infarct size by tetrazolium staining was similar in both groups (8.9 +/-1.2% of left ventricle vs. 8.9 +/- 2.6%). Vessel density in the periinfarct area was significantly higher in SDF-1alpha treated animals than in controls (349 +/- 17/mm2 vs. 276 +/- 21/mm2, p < 0.05). Myocardial perfusion (SPECT) did not change in either group. Ejection fraction and stroke volume (EMM) decreased in SDF-1alpha animals and increased in controls (difference between groups p = 0.05 for ejection fraction and p < 0.05 for stroke volume). Linear local shortening (EMM) did not change in controls (11.4 +/- 1.3% to 11.5 +/- 0.5%) but decreased significantly in SDF-1alpha treated animals (12.1 +/- 0.9% to 8.4 +/- 0.9%, p < 0.05, p < 0.05 for difference between groups). SDF-1 delivery was associated with a substantial loss of collagen in the periinfarct area (32+/-5% vs. 61+/-6% in control animals, p < 0.005).
Conclusion: A strategy to augment stem cell homing by catheter-based transendocardial delivery of SDF-1alpha in experimental myocardial infarction increases periinfarct vessel density, fails to improve myocardial perfusion, is associated with loss of collagen in the periinfarct area and impairs left ventricular function.