Abstract 18544: A Critical Role of Src Family Kinase (SFK) in SDF-1/CXCR4-Mediated Bone-Marrow Progenitor-Cell Homing to Ischemic Cardiac Tissue
Introduction: The G protein-coupled receptor CXCR4 and its ligand stromal-cell derived factor 1 (SDF-1) play an important role in directing progenitor cells (PC) homing to ischemic tissue. The Src family protein kinases (SFK) can be activated by, and serve as effectors of, G proteins. However, whether SFK play a role in SDF-1/CXCR4-mediated PC homing is unknown.
Methods and Results: To investigate whether SDF-1-CXCR4 signaling activates SFK, we isolated mouse bone marrow mononuclear cells (BM MNCs) and applied onto VCAM1-coated plates, followed by addition of CXCR4 agonist SDF-1 and/or antagonist AMD3100. SDF-1 rapidly (in 2 min) and dose-dependently increased phosphorylation (activation) of Lyn, a major SFK in the BM; AMD3100 attenuated the SDF-1-induced Lyn phosphorylation. Notably, SDF-1 treatment did not increase Lyn phosphorylation in the BM MNCs isolated from Mx1-cre+CXCR4fl/fl mice in which the CXCR4 gene had been deleted. To investigate whether SFK play a role in SDF-1/CXCR4-mediated chemotaxis, we performed Boyden chamber assay; SFK inhibitor SU6656 significantly inhibited BM-MNC migration towards SDF-1 (P<0.001, n=4). To investigate whether SFK play a role in SDF-1/CXCR4-mediated BM-MNC homing to the ischemic heart, we isolated BM MNCs from CXCR4BAC:eGFP transgenic mice and injected 1x106 cells into WT and SDF-1BAC:SDF1-RFP transgenic mice (in which the expression of SDF1-RFP fusion protein is driven by the SDF-1 genomic regulatory sequence and the level of total SDF-1 protein is doubled) that had undergone surgical myocardial infarction 8h earlier. Some recipient mice also received two i.p. injections of SU6656 (6mg/kg) at the time of cell injection and again 4h later. We found a significantly greater amount of eGFP+ cells (1.6 fold, p<0.01, n=5) and eGFP+c-kit+ cells (1.9 fold, p<0.01, n=5) recruited in the infarct border area of the SDF-1BAC:SDF1-RFP recipients than in WT recipients. SU6656 treatments significantly reduced the amount of eGFP+ cells and eGFP+c-kit+ cells (P<0.01, n=5) in both WT and SDF-1BAC:RFP recipients and abrogate the difference between the 2 groups.
Conclusions: SFK play a critical role in SDF-1/CXCR4-mediated BM PC homing to the ischemic cardiac tissue thus may provide a target for modulation of tissue repair.
- Stem/progenitor cells
- Endothelial progenitor cell
- Ischemic heart disease
- Signal transduction
- Cardiac regeneration
- © 2010 by American Heart Association, Inc.