| Objective: Preliminary study the changes of series effects of bone marrow mesenchymal stem cells (MSCs) pretreatment by stromal cell-derived factor-1 (SDF-1); then transplanted SDF-1 preconditioning-stem cells into rat myocardial infarction model, in order to observe the stem cell homing, proliferation, angiogenesis, and cell apoptosis in myocardial ischemia zone, left ventricular remodeling, cardiac function, and to explore the mechanism of stem cell treatment of ischemic heart disease.Materials and methods: In vitro part: Isolated and cultured bone marrow mesenchymal stem cells (MSCs) by using SD rat tibia and femur bone marrow, and conduct phenotypic identification. Incubated the MSCs for 60 minutes with (SDF-1 pretreatment group) or without (control group) stromal cell-derived factor (SDF-1) serum-free medium respectively, then analysis the vascular endothelial growth factor (VEGF) level in nutrient medium, and to detect the expression of CXCR-4 receptor changes on cell surface after treatment; finally, mark MSCs by Brd U, and make climbing films, detected the cell labeling rate by immunohistochemistry, in order to meet the needs of tracing and observation transplanted cells.In vivo Part: Establish 48 rat myocardial infarction models and divid into three groups randomly: A group is blank group; B group is stem cells group, the control; C group is SDF-1 preconditioning. 24 hours after their myocardial infarction, inject normal saline (A group) , MSCs(B group) or the SDF-1 preconditioning MSCs (C group) via the tail vein respectively; 24 hours after transplantation , detect the cardiomyocyte apoptosis in infarct border zone; 1 week later, detect the homing and proliferation Brd U-positive cells in infarct border zone; four weeks later, the detection of heart function, calculation of infarct size will be take; and fluorescence perfusion imaging of the blood vessels will be take for neovascularization density of infarction-surrounding area.Results: The use of adherent culture method can obtain stable SD rat bone marrow-derived mesenchymal stem cells, the cell phenotype detection proved it as CD29 ~+ CD90 ~+ CD34~-cells; incubated MSCs with 10umol / L Brd U for 24 hours, the marking rate is above 98%; preconditioning MSCs with recombinant chemokine SDF-1 can significantly increase the capabilities of release of VEGF (68.92±5.03 pg/ml vs 38.79±3.16 pg/ml,P<0.05)and receptor CXCR-4 occurs endocytosis rapidly, showing decreased expression in the membrane. Thoracotomy-LAD ligation method can be used to build a successful model of rat myocardial infarction; after MSCs transplanted, hearts HE staining histological examination indicated: in C group, infarct border zone tissue section muscle fibers are more orderly, nuclear morphology is more uniform, and have more small vessel-like structures around infracted zone compared with B group; the number of apoptotic cells significantly reduced (25.75±4.43 vs 39.70±4.10, P <0.05), Brd U-positive cells significantly increased (44.78±6.21 vs 31.14±6.48, P <0.05); 4 weeks after MSCs transplantation, cardiac ultrasound showed C group's left ventricular ejection fraction (LVEF) significantly improved (55.83±5.45 vs 42.14±6.17, P <0.005), LVDs rising trend significantly reduced (4.92±0.16 vs 5.75±0.39, P <0.005) when compared with B group; Left ventricular fibrosis in C group significantly minor, scar tissue area is reduced (23.71±2.49 vs 32.83±1.58, P <0.005); in the ischemic area, perfusion blood vessel density of C groups was significantly higher than B group (31.16±4.08 vs 19.91±3.87, P <0.05).Conclusions: 1 SDF-1 preconditioning MSCs can significantly increase their release of VEGF and CXCR-4 receptor occur endocytosis to enhance cell homing ability. 2 Transplanted SDF-1 preconditioning MSCs to treat myocardial infarction can reduce the apoptosis in infarct border zone, increase perfusion of the ischemic area, inhibit ventricular remodeling and improve cardiac function.
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