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Lu W.,ZhongDa Hospital affiliated with Southeast University | Xie Z.,Nanjing Southeast University | Tang Y.,ZhongDa Hospital affiliated with Southeast University | Yao L.B.,Nanjing Southeast University | And 2 more authors.
Theranostics | Year: 2015

Background: Despite the benefits of mesenchymal stromal cell (MSC) transplantation in cardiac tissue, detailed in vivo observations have shown that MSCs only survive for a brief period after transplantation due to harsh microenvironmental conditions, including ischemia, inflammation and anoikis, in the infarcted myocardium. Thus, new strategies are needed to enhance MSC survival and inhibit cardiac remodeling. Studies have now demonstrated that chemokine [C-C motif] ligand 2 (CCL2) and its cognate receptor C-C chemokine receptor 2 (CCR2) promote excessive Ly6Chigh inflammatory monocyte infiltration at the infarct in response to ischemic myocardial injury. Therefore, decreasing the activities of these monocytes immediately after acute myocardial infarction (AMI) could be beneficial for AMI patients. Objectives: This study tested the hypothesis that therapeutic siRNA-loaded photoluminescent mesoporous silicon nanoparticles (PMSNs) targeting CCR2 expression in Ly6Chigh inflammatory monocytes decrease the accumulation of these cells in the infarct, improve the efficacy of MSC transplantation and attenuate myocardial remodeling. Methods: PMSNs carrying therapeutic siCCR2 were first synthesized without the inclusion of fluorescent materials or dyes. After AMI BALB/c mice were established, 105 5-ethynyl-2'- deoxyuridine (EdU)-labeled MSCs suspended in 100μl of phosphate buffered saline (PBS) were injected into the border zone of the infarct of each mouse. PMSNs-siCCR2 (25μg/g) were also intravenously injected via the tail vein immediately following AMI induction. Control mice were injected with an equal amount of PMSNs without siCCR2. PMSNs-siCCR2 were examined in vivo using near-infrared imaging technology. The therapeutic effects of PMSNs-siCCR2 for MSC transplantation were determined at the mRNA, protein and functional levels. Results: PMSNs-siCCR2 circulated freely in vivo and were cleared in a relatively short period of time (t1/2=37min) with no evidence of toxicity. The therapeutic PMSNs-siCCR2 showed higher levels of cellular accumulation in Ly6Chigh monocytes in the spleen and more efficient degradation of CCR2 compared with the control (8.04%±2.17% vs. 20.02%±4.55%, p<0.001). Subsequently, the PMSNs-siCCR2 decreased the accumulation of CD11b-positive monocytes at the infarct (49.3%±17.34% vs. 61.32%±22.43%, p<0.001) on day 1. Increased survival of transplanted MSCs (13±3/mm2 vs. 4±1/mm2, p<0.001) and significantly decreased TdT-mediated dUTP nick end la-beling (TUNEL)+ cardiac myocytes (17.44%±6.26% vs. 39.49%±13.28%, p<0.001) were then identified in the infarct zone three days after AMI induction in the PMSNs-siCCR2 group. Three weeks after MSC injection, significant increases were observed in the vascular density (235.5±39.6/mm2 vs. 147.4±20.3/mm2, p<0.001) and the cardiac myosin-positive area (21.7%±8.4% vs. 13.2%±4.4%, p<0.001) of the infarct border zone. In addition, significant amelioration of left ventricular (LV) remodeling (thickness of the LV posterior walls) (0.84±0.11mm vs. 0.61±0.08mm, p<0.001) was also observed at the same time compared with the control group. Conclusions: PMSNs-siCCR2-mediated CCR2 gene silencing in Ly6Chigh monocytes improved the effectiveness of MSC transplantation and selectively ameliorated myocardial remodeling after AMI. These results suggest that PMSNs-siCCR2 could potentially be used to develop an anti-inflammatory therapy for post-AMI MSC transplantation. © 2015 Ivyspring International Publisher.

Lu W.,ZhongDa Hospital affiliated with Southeast University | Lu W.,The Second Hospital Affiliated with Southeast University | Tang Y.,ZhongDa Hospital affiliated with Southeast University | Tang Y.,The Second Hospital Affiliated with Southeast University | And 7 more authors.
American Journal of Translational Research | Year: 2015

Background: Ischemia related inflammation is the most critical factor for the survival of transplanted mesenchymal stem cells (MSCs), and strategies for controlling excessive inflammation after acute myocardial infarction (AMI) are essential and necessary for cell transplantation therapy. Our present study tested the effect of decreased Ly6Chigh monocytes on mouse MSCs transplantation after AMI. Methods: BALB/c AMI mice were treated systemically with a CCR2 antagonist (RS 504393, 2 mg/kg, subcutaneously) or normal saline (control group). Next, 105 EdU-labeled MSCs were administered by intramyocardial injection to the mice in each group. TUNEL kits were used to identify the apoptotic cardiomyocytes in the infarct. The slides of the infarct border zone were stained with wheat germ agglutinin to measure the vessel density, and anti-myosin heavy chain eFluor 660 was used to measure the cardiac myosin-positive area. A transwell chamber was used to examine the interactions between Ly6Chigh monocytes and MSCs. The inflammatory cytokines expressed by Ly6Chigh monocytes and the SDF-1 expressed by MSCs were detected using ELISA kits. MSC viability was further examined by MTT and mitochondrial membrane potential assays by flow cytometry using JC-1 kits. Results: We first observed the increased survival of transplanted MSCs (11.2 ± 3.4/mm2 vs. 3.5 ± 1.6/mm2, p < 0.001), and the decreased apoptosis of cardiomyocytes (11.20% ± 3.55% vs. 20.51% ± 8.17%, p < 0.001) in the infarcts at 3 days in the CCR2 antagonist group. An increased number of capillaries and small arterioles (139.6 ± 21.7/mm2 vs. 95.4 ± 17.6/mm2, p < 0.001) and an increased cardiac myosin-positive area (17.9% ± 6.6% vs. 11.8% ± 3.5%, p < 0.001) were also observed in the infarct zone at 21 days post MSC infusion in the CCR2 antagonist group. In addition, a significantly increased LvEF% (50.17 ± 10.06 vs. 45.44 ± 9.45, p < 0.001) was detected at the same time compared to the control mice. We further demonstrated that both the mitochondrial membrane potential of the MSCs (0.45 ± 0.11 vs. 3.4 ± 0.3, p < 0.001) and stromal cell-derived factor-1 (SDF-1) secreted by the MSCs significantly decreased (80.77 ± 39.02 pg/ml vs. 435.5 ± 77.41 pg/ml, p < 0.001) when co-cultured with Ly6Chigh monocytes. This is possibly mediated by the over-expressed cytokines secreted by the Ly6Chigh monocytes compared to the Ly6Clow monocytes, including IL-1 (139.45 ± 30.44 vs. 80.05 ± 19.33, p < 0.001), IL-6 (187.82 ± 40.43 vs. 135.5 ± 22.09, p < 0.001), TNF-α (121.77 ± 31.65 vs. 75.3 ± 22.14, p < 0.001) and IFN-γ (142.46 ± 27.55 vs. 88.25 ± 19.91, p < 0.001). © 2015, E-Century Publishing Corporation. All right reserved.

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