Chronic AMD3100 antagonism of SDF-1α–CXCR4 exacerbates cardiac dysfunction and remodeling after myocardial infarction

The role of the SDF-1α–CXCR4 axis in response to myocardial infarction is unknown. We addressed it using the CXCR4 antagonist, AMD3100, to block SDF-1α interaction with CXCR4 after chronic coronary artery ligation. Chronic AMD3100 treatment decreased ejection fraction and fractional shortening in mice 20 days after myocardial infarction compared with vehicle-treated mice (echocardiography). Morphometric analysis showed hearts of AMD3100-treated infarcted mice to have expanded scar, to be hypertrophic (confirmed by myocyte cross-section area) and dilated, with increased LV end systolic and end diastolic dimensions, and to have decreased scar collagen content; p-AKT levels were attenuated and this was accompanied by increased apoptosis. Despite increased injury, c-kitpos cardiac progenitor cells (CPCs) were increased in the risk region of AMD3100-treated infarcted mice; CPCs were CD34neg/CD45neg with the majority undergoing symmetric cell division. c-kitpos/MHCpos CPCs also increased in the risk region of the AMD3100-treated infarcted group. In this group, GSK-3β signaling was attenuated compared to vehicle-treated, possibly accounting for increased proliferation and increased cardiac committed MHCpos CPCs. Increased proliferation following AMD3100 treatment was supported by increased levels of cyclin D1, a consequence of increased prolyl isomerase, Pin1, and decreased cyclin D1 phosphorylation. In summary, pharmacologic antagonism of CXCR4 demonstrates that SDF-1α–CXCR4 signaling plays an important role during and after myocardial infarction and that it exerts pleiotropic salubrious effects, protecting the myocardium from apoptotic cell death, facilitating scar formation, restricting CPC proliferation, and directing CPCs toward a cardiac fate.

Research Highlights
► SDF-1α–CXCR4 signaling is necessary during the myocardial response to infarction.
► CXCR4 activation affects signaling through AKT and GSK-3β dependent pathways.
► CXCR4 signaling facilitates myocardial survival, by attenuating cell death.
► CXCR4 promotes cardiac progenitor cells to contribute to myocardial infarction.
► CXCR4 promotes favorable remodeling after myocardial infarction.