Mesenchymal stem cells (MSCs) are potential sources of cells for tissue repair. However, little information is available about the time course of homing and differentiation of systemically delivered MSCs after acute myocardial ischemia (MI). In the present study, MSCs were isolated from male rat bone marrow and expanded in vitro. Female rats were divided randomly into three groups. Three hours after coronary ligation, the transplanted group received an infusion of MSCs through the tail vein; at the same time, a coronary-ligated control group was injected with culture medium, and a normal (unligated) group received MSCs. Homing of MSCs to the heart was assessed by expression of the Y chromosome sry gene using fluorescence in situ hybridization (FISH) at 3 days, 1, 4, and 8 weeks after transplantation. Immunofluorescent staining was used to examine markers for cardiomyocytes, endothelial cells, and smooth muscle cells. Hemodynamics in the hearts was also measured to assess cardiac function. At each time point, sry-positive cells were present in the cardiac tissue in transplanted group but not in the hearts of normal and control group animals. The number of sry-positive cells was significantly higher at 1 week compared to 3 days after transplantation. No significant difference was found in the number of sry-positive cells among those of 1, 4, and 8 weeks after transplantation. At 3 days and 1 week after transplantation, the sry-positive cells in the transplanted group lacked troponin, desmin, smooth muscle alpha-actin, and CD31. At the later time points, cardiomyocytes, smooth muscle cells, and endothelial cells bearing sry were identified in the transplanted group. The cardiac function in transplanted group showed higher improvement at 4 and 8 weeks compared to 1 week after transplantation. Our data suggest that intravenously delivered MSCs are capable of homing toward the ischemic myocardium, and the fastigium of homing appeared around 1 week after MI. The differentiation of MSCs to cardiomyocytes, smooth muscle cells, and endothelial cells shows to be time dependent and arises at 1 to 4 weeks after transplantation.

AimsThe late and persistent sodium current (I Na ) has been identified as a target for anti-arrhythmia drugs in patients with heart failure (HF). However, the underlying mechanism of late I Na (I NaL ) production remains uncertain. We hypothesized that transcriptional alteration among sodium channel (NaCh) isoforms may contribute to I NaL in failing cardiomyocytes. Methods and resultsPressure-overload rat models were created by 16-week constriction of the ascending aorta (HF). Haemodynamic and electrocardiographic variables were studied in sham operation and HF rats. Action potential (AP) and I Na were recorded using whole-cell patch-clamp techniques. The expression of various NaCh isoforms was evaluated by immunocytochemistry, RT-PCR, and western blot. The HF group exhibited left ventricular enlargement, systolic dysfunction, and prolongation of QTc intervals (P , 0.05). Current-clamp recording indicated that AP durations (APDs) were more sensitive to tetrodotoxin. Voltage-clamp recordings showed that I NaL was increased (21.54 + 0.43 vs. 21.08 + 0.38 pA/pF, P , 0.01) in HF, but transient I Na (I NaT ) density was decreased (214.61 + 2.30 vs. 226.15 + 5.17 pA/pF, P , 0.01). Correspondingly, the relative mRNA levels of the neuronal isoforms SCN1a and SCN8a increased 2.5-and 2.7-fold, respectively; SCN3a did not change, whereas SCN5a decreased by 60% in HF. Protein levels paralleled their mRNA expression. ConclusionThe up-regulated expression of the neuronal NaCh isoforms SCN1a and SCN8a could be one mechanism of I NaL production, which may contribute to prolongation of APD in the failing heart.--

Summary Mesenchymal stem cells (MSCs) are potential sources of cells for tissue repairing. However, little information is available regarding the therapeutic potency of intravenously transplanted MSCs for myocardial ischemia (MI). In the present study, MSCs were isolated from bone marrow of male rats and expanded in vitro. Three hours after ligation of left anterior descending artery, the transplanted group received an infusion of MSCs through the tail vein. At the same time, a coronary‐ligated control group was injected with culture medium. Homing of MSCs to the heart was assessed by expression of the Y chromosome sry gene using fluorescent in situ hybridization (FISH). At 1 week or 8 weeks after transplantation, sry positive cells were present in cardiac tissue in the transplanted group, but not in the hearts of control group. Cardiomyocytes, smooth muscle cells, and endothelial cells that bore sry gene were identified in transplanted group at 8 weeks after transplantation. Ultrastructural observation revealed that a large number of capillary and some immature myocytes were found to survive in the ischemia region. MSCs transplantation also decreased LVEDP pressure and −dP/dt, but increased LVSP and +dP/dt. The cardiac infarct size was significantly smaller in transplanted group than in control group. Our data suggest that intravenously transplanted MSCs improve cardiac performance and promote the regeneration of blood vessels and cardiomyocytes.