title: Inhibiting the mobilization of Ly6C(high) monocytes after acute myocardial infarction enhances the efficiency of mesenchymal stromal cell transplantation and curbs myocardial remodeling.
abstract: 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 Ly6C(high) 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, 10(5) 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 Ly6C(high) monocytes and MSCs. The inflammatory cytokines expressed by Ly6C(high) 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/mm(2) vs. 3.5 ± 1.6/mm(2), 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/mm(2) vs. 95.4 ± 17.6/mm(2), 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 Ly6C(high) monocytes. This is possibly mediated by the over-expressed cytokines secreted by the Ly6C(high) monocytes compared to the Ly6C(low) 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).
authors.affiliation: Department of Cardiology, Zhongda Hospital Affiliated with Southeast University China ; Department of Cardiology, The Second Hospital Affiliated with Southeast University China.
authors.forename: Wenbin
authors.initials: W
authors.lastname: Lu
authors.affiliation: Department of Cardiology, Zhongda Hospital Affiliated with Southeast University China ; Department of Cardiology, The Second Hospital Affiliated with Southeast University China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Tang
authors.affiliation: Department of Cardiology, Zhongda Hospital Affiliated with Southeast University China.
authors.forename: Ziwei
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Cardiology, Zhongda Hospital Affiliated with Southeast University China ; Department of Cardiology, The Second Hospital Affiliated with Southeast University China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Cardiology, Zhongda Hospital Affiliated with Southeast University China.
authors.forename: Yuyu
authors.initials: Y
authors.lastname: Yao
authors.affiliation: Department of Cardiology, Zhongda Hospital Affiliated with Southeast University China.
authors.forename: Cong
authors.initials: C
authors.lastname: Fu
authors.affiliation: Department of Cardiology, Zhongda Hospital Affiliated with Southeast University China.
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Cardiology, Zhongda Hospital Affiliated with Southeast University China.
authors.forename: Genshan
authors.initials: G
authors.lastname: Ma
keywords: AMI; CCR2; Ly6Chigh monocytes; MSCs