ABSTRACT
Electrophysiological properties of implanted mesenchymal stem cells (MSCs) in infarcted hearts remain unclear, and their proarrhythmic effect is still controversial. The intent of this study was to investigate electrophysiological properties and proarrhythmic effects of MSCs in infarcted hearts. Rats were randomly divided into a myocardial infarction (MI) group, a MI-DMEM group (received DMEM medium injection) and MI-MSCs group (received MSCs injection). Survival analysis showed that the majority of engrafted MSCs died at day 9 after transplantation. Engrafted MSCs expressed cardiac markers (MYH, cTnI, Cx43), cardiac ion channel genes (Kv1.4, Kv4.2 and Kir2.1) and potassium currents (I (to), I (K1) and I (KDR)), but did not express Nav1.5, Cav1.2, Na(+) current and Ca(2+) current during their survival. When induced by Ca(2+), implanted MSCs exhibited no contraction ability after being isolated from the heart. Following 8-week electrocardiography monitoring, the cumulative occurrence of ventricular arrhythmias (VAs) was not different among the three groups. However, the prolonged QRS duration in infarcted rats without VAs was significantly decreased in the MI-MSCs group compared with the other two groups. The inducibility of VAs in the MI-MSCs group was much lower than that in the MI and MI-DMEM groups (41.20 vs. 86.67 % and 92.86 %; P < 0.0125). The ventricular effective refractory period in MI-MSCs group was prolonged in comparison with that in the MI and MI-DMEM groups (56.0 ± 8.8 vs. 47.7 ± 8.8 ms and 45.7 ± 6.2 ms; P < 0.01). These results demonstrate that MSCs do not acquire the electrophysiological properties of mature cardiomyocytes during the survival period in the infarcted hearts. However, they can alleviate the electrical vulnerability and do not promote ventricular arrhythmias.
Subject(s)
Mesenchymal Stem Cell Transplantation , Mesenchymal Stem Cells/cytology , Mesenchymal Stem Cells/physiology , Myocardial Infarction/therapy , Animals , Arrhythmias, Cardiac , Cell Differentiation , Electrocardiography , Flow Cytometry , Fluorescent Antibody Technique , Laser Capture Microdissection , Myocardial Infarction/physiopathology , Myocytes, Cardiac/cytology , Myocytes, Cardiac/physiology , Rats , Rats, Sprague-Dawley , Real-Time Polymerase Chain ReactionABSTRACT
<p><b>BACKGROUND AND OBJECTIVE</b>Monitoring the therapeutic effects of radiotherapy for nasopharyngeal carcinoma (NPC) is critical to providing individualized treatment. This in-vivo study was initially designed to evaluate the therapeutic effect of radiotherapy using 18F-fluorodeoxyglucose positron emission tomography with computed tomography (18F-FDG PET-CT) imaging.</p><p><b>METHODS</b>18F-FDG PET-CT imaging was performed on all of the 10 nude mice bearing NPC xenografts before radiotherapy, and early-phase and delayed-phase PET-CT images were performed on 7 of the 10 mice. All mice were randomly divided into either a control group or a radiotherapy group. The 5 mice in the control group were immediately killed after the imaging and pathology were performed. After receiving radiotherapy of 12 Gy, 5 animals in the radiotherapy group were given 18F-FDG PET-CT imaging on days 2, 4, and 6, and then were killed for pathologic evaluation. Regions of interest (ROI) technology was used to measure the tumor target/non-target (T/NT) ratio and the volume of the tumors.</p><p><b>RESULTS</b>The average T/NT ratios of early- and delayed-phase imaging were 1.806 +/- 0.532 and 1.777 +/- 0.597, respectively, with no significance (P > 0.05). For the radiotherapy group, the average T/NT ratios for 18F-FDG PET-CT before radiotherapy, and on days 2, 4, and 6 after radiotherapy, were 1.735 +/- 0.466, 1.818 +/- 0.396, 1.096 +/- 0.101, and 0.604 +/- 0.108, respectively, The tumor volumes were (1.48 +/- 0.27) cm3, (1.57 +/- 0.31) cm3, (1.59 +/- 0.31) cm3 and (1.60 +/- 0.29) cm3, respectively. The average T/NT ratios of day 6 after radiotherapy and the other time points were significant (P < 0.05). The average death ratio of the tumor cells was (93.00 +/- 7.42)% after 6 days of post-radiotherapy.</p><p><b>CONCLUSIONS</b>18F-FDG PET-CT imaging can be used for the early assessment of radiotherapeutic effect of NPC in vivo. Day 6 after radiotherapy may be an appropriate time point for the imaging. However, the T/NT ratio measurement of delayed-phase imaging might make no sense for the diagnosis of NPC.</p>
