Background: Interruption of cardiac stromal cell derived factor 1 (SDF1)-CXCR4 axis by chronic AMD3100 administration increased myocardial injury after permanent coronary artery ligation demonstrating the important role of this chemokine in cardiac regeneration.
Hypothesis: Cardiomyocyte specific conditional overexpression of SDF1 prevents heart failure after permanent coronary ligation and facilitates cardiac regeneration.
Methods and Results: Tetracycline-controlled, αMyHC promoter directed overexpression of cardiac SDF1, resulted in a significant increase of SDF1 expression (SDF1: 8.1 ng/mg protein) compared to littermate WT mice (0.02 ng/mg protein) four weeks after doxycycline withdraw. SDF1 overexpression increased AKT and casein kinase 1 levels in the heart. Although there was no difference in cardiac function and scar size 1 week after infarction, SDF1 overexpression improved left ventricular (LV) ejection fraction (SDF1 [n=13]: 47±5% [mean±SEM] vs. WT [n=15]: 29±4%, p<0.05) decreased end-diastolic volume (78±10 vs. 158±30, p<0.05) and reduced infarct size measured by trichrome staining (13±3% vs. 23±3% of LV wall, p<0.05) 4 weeks after permanent ligation. Bromodeoxyuridine (BrdU) staining revealed increased regeneration indicated by a 5-fold increase in BrdU+cardiomyocyte (CM) nuclei in the borderzone of the infarct (22±3% vs. 5±1% CM nuclei, p<0.01). Increased proliferation in SDF1 mice was confirmed by a higher number of KI67+ cells compared to WT mice. Cardiomyocyte cross sectional area in the border zone was significantly reduced in SDF1 mice (365±13 μm2 vs. 434±10 μm2, p<0.001) while capillary density was unchanged (2348±151/ mm2 vs. 2498±153/ mm2) compared to WT mice.
Conclusion: This study demonstrates for the first time that cardiac specific overexpression of SDF1 increases myocardial regeneration and improves LV function 4 weeks after permanent coronary ligation.