| Objective To study the expression of stromal cells-derived factor land CXC chemokine receptor 4 (SDF-1/CXCR4) in the acute infarct myocardium in rat after implanation of hypoxic preconditioning bone marrow mesenchymal stem cells (HPMSCs).Methods MSCs were isolated and purified for culture in vitro and serial passage by the attachment culture method. The morphological changes of the MSCs were continuously observed under the inverted microscope. The cell growth curve was measured by MTT method, and membrane antigens were detected with flow cytometry (FCM). MSCs were cultured by using the whole bone marrow adherence method. HPMSCs were cultured under hypoxic (0.5% O2 for 24 hrs) before transplantation. SD rats were anesthetized by intraperitoneal injection of pentobarbital sodium. After tracheotomy intubations, respiration machine was linked. Lefe anterior thoracotomy through 3,4 intercostals region was performed, and then the left anterior descending coronary arteries were ligated to produce acute myocardial infarction. The bone marrow mesenchymal stem cells and were injected into the area of acute infarct myocardium after the left anterior descending coronary artery been ligated 10 minutes. The different concentration and expression of SDF-1/CXCR4 in the area of acute myocardial infarction and left ventricular function were analyzed.Results The MSCs in primary culture which were adhered to plastic surface within 48 h after displacement took the oval, asteroid, short and fusiform shapes.7 to 12 days after culture in DMEM medium containing 10% FBS, the cells reached 90% confluence in single layers, taking a long and fusiform shape. Further purification was achieved by expansion at serial passages. MSCs were in latency for 2 days, converted into growth period on the 3rd day and entered the stationary phase on the 5th day. FCM results indicated that the positive rate of CD45, CD90 and CD29 was 1.50%, 99.18%,97.70%, respectively. The model of acute myocardial infarction was established successfully. Following the details were highlighted, survival rate was 95% after operation and 92.5% beyond three weeks. The left ventricle became larger and the endocardium of the survival rats showed fibrosis. Histopathology study could see the scar and the proliferation of the fibrous tissue.At 24h, first,2nd,4th week after transplantation, the vascular density respectively in the MSCs implant group and HPMSCs implant group, were significantly higher than that in the control group (p<0.05). At same time, the expression of SDF-1 and CXCR4 in topical injection sites of infarct myocardium respectively in the MSCs and HPMSCs implanted groups, were significantly higher than that in infarct site in the control group (p<0.05), and HPMSCs group were the highest group in those. The level of SDF-1/CXCR4 in the HPMSCs implanted group and MSCs implanted groups were highest at 24h after transplantation, then the level began to reduced.Conclusion The attachment culture method can be effectively used to isolate and purify SD rat MSCs. The cultured MSCs are stable in growth with active proliferation and share the general biological characteristics of MSCs, which will further make them ideal seed cells for tissue engineering. Rat acute myocardial infarction model can be made quickly by this way and the model's survival rate was improved effectively. The factors, including Correct applying of anesthetic, scientific using of artificial respiration, decreasing Of lung injury, exact ligating of left anterior descending coronary arteries, form the basis for making rat model with myocardial infarction. The MSCs, after being implanted into the acute infarct myocardium, showed the vascular regeneration and the level of SDF-1/CXCR4 increasing and play an positive effect on infarct myocardium. This study suggested that MSCs and HPMSCs, implanted into the region of acute infarct myocardium, had the ability of preservation of the myocardial structure and could improve left ventricular function, the effect of HPMSCs were better.HPMSCs and MSCs upgrades the expression of SDF-1/CXCR4 in the region of infarct myocardium, and forms microenvironments which stem cells are adapted to and grow in. SDF-1 increases the adhesion, migration and homing of circulating CXCR4-positive progenitor cells to ischemic tissue, and improved heart function.To sum up, the MSCs, after being implanted into the area of acute infarct myocardium, showed vascular regeneration and reduce the infarct size. In the mean time, the level of SDF-1/CXCR4 increased, which may be one of cause of infracted heart function improvement. The present study provided the potential application of regulation of level of SDF-1/CXCR4 in the treatment of myocardial diseases. |
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