Abstract 18115: A Novel Mechanism Underlying SDF-1/CXCR4-mediated Bone-Marrow Progenitor Cell Homing to the Ischemic Heart: The Role of Src Family Kinase (SFK)
Background: The chemokine SDF-1 and its G protein-coupled receptor CXCR4 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. Here we sought to determine whether SFK play a role in SDF-1/CXCR4-mediated PC homing.
Methods and Results: We firstly investigated whether SDF-1-CXCR4 signaling activates SFK. Mouse bone marrow mononuclear cells (BM-MNCs) were isolated and treated with SDF-1 and/or CXCR4 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. We then investigated whether SFK is involved in SDF-1/CXCR4-mediated chemotaxis. In a Boyden chamber assay, pretreatment of BM-MNCs with SFK inhibitor SU6656 significantly inhibited their migration towards SDF-1 (P<0.001, n=4); however, when BM-MNCs from CSK-knockout mice (with elevated SFK activity) were used, the migration was significantly enhanced (P<0.01, n=6). We finally investigated whether SFK is important for SDF-1/CXCR4-mediated BM-MNC homing to ischemic heart tissue. BM-MNCs isolated from CXCR4BAC:eGFP transgenic mice were i.v. injected (1x106 cells/mouse) into WT and SDF-1BAC:SDF1-RFP transgenic mice that had undergone surgical myocardial infarction 8h earlier. Some recipient mice also received two i.p. injections of SU6656 (6 mg/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: SDF-1/CXCR4-mediated BM PC homing to the ischemic cardiac tissue is critically dependent on SFK activity; SFK may provide a target for enhancement of tissue repair.
- © 2012 by American Heart Association, Inc.