Differentiation Of Marrow Stromal Cells Transplanted Into Infarcted And Non-Ischemic Myocardium

Objective: To investigate the effects of the acute myocardial infarction (AMI) environment on myocardial differentiation.of adult marrow stromal cells(MSC).Methods: MSCs were isolated from adult inbred Wistar rats' femurs and tibias, cultured in high glucose Dulbecco's modified eagle medium (DMEM) with 20% fetal bovine serum (FBS), in 37 C, 5% CO2 condition. MSCs were purified by differential attachment technique, expanded in vitro, and labeled with DAPI. Animal model of AMI was established by ligation of the left anterodecendant arteries ( LAD ) in the rats of the same species, one week after operation, equal numbers of MSCs were injected into infarcted and non-ischemic areas respectively. Heart tissues were taken 1, 2 and 4 weeks after cell transplantation and cryo-sectioned in series. Numbers and distributions of MSCs were observed under fluorescent microscope. The expression of cardiac troponin T (TnT) of MSCs were detected by immuno-fluorescent histochemistry.Results: The cultured total marrow cells proliferated rapidly. Cells could be passaged 4-6 days after primary culture or 3-4 days after sub-culture. After 2-3 passages, highly purified uniform fibroblast-like MSCs were obtained. The rates of DAPI labeled approached 100%. After LAD ligation, the left ventricle of model rats formed infarcted lesion. Labeled MSCs could be found with blue fluorescence in both infarcted and in non-ischemia myocardium. Host myocardium appeared bright green fluorescence with obvious striation. one week after transplantation, the cell numbers and TnT positive rates of MSCs were not significantly differ in two sites(5l70.25 548.51 vs 5695.00 631.43, 1.41% 0.34 vs 2.32% 0.76, P>0.05). Two weeks after transplantation, most MSCs in non-ischemia area still located arround the injection site without obvious migration. In infarcted area, however, MSCs proliferated and migrated quickly, some MSCs infiltrated into host myocardium. The cell numbers and TnT positive rates of MSCs in infarcted area (15022.25 991.29 and 9.17% 2.48) were significantly higher than those in non-ischemia area(7566.88 839.98 and 4.29% 0.74 P<0.01). Four weeks after transplantation, visible MSCs were obviouslydecrease. Numbers of MSCs in infarcted and non-ischemia area were not significant different (805.57 218.28 vs 686.33 140.81, P>0.05). The TnT positve rates of MSCs, however, in infarcted area were still higher than that in non-ischemia area(14.76% 3.32 vs 8.97% 1.12, P<0.05)Conclusion: MSC can survive in AMI environment. Furthermore, AMI environment can stimulate MSC proliferation and migration, and is more in favor of MSC differentiation into cardiac myocytes.