Direct conversion of cardiac fibroblasts (CFs) to cardiomyocytes (CMs) in vivo to regenerate heart tissue is an attractive approach. After myocardial infarction (MI), heart repair proceeds with an inflammation stage initiated by monocytes infiltration of the infarct zone establishing an immune microenvironment. However, whether and how the MI microenvironment influences the reprogramming of CFs remains unclear. Here, we found that in comparison with cardiac fibroblasts (CFs) cultured in vitro, CFs that transplanted into infarct region of MI mouse models resisted to cardiac reprogramming. RNA-seq analysis revealed upregulation of interferon (IFN) response genes in transplanted CFs, and subsequent inhibition of the IFN receptors increased reprogramming efficiency in vivo. Macrophage-secreted IFN-β was identified as the dominant upstream signaling factor after MI. CFs treated with macrophage-conditioned medium containing IFN-β displayed reduced reprogramming efficiency, while macrophage depletion or blocking the IFN signaling pathway after MI increased reprogramming efficiency in vivo. Co-IP, BiFC and Cut-tag assays showed that phosphorylated STAT1 downstream of IFN signaling in CFs could interact with the reprogramming factor GATA4 and inhibit the GATA4 chromatin occupancy in cardiac genes. Furthermore, upregulation of IFN-IFNAR-p-STAT1 signaling could stimulate CFs secretion of CCL2/7/12 chemokines, subsequently recruiting IFN-β-secreting macrophages. Together, these immune cells further activate STAT1 phosphorylation, enhancing CCL2/7/12 secretion and immune cell recruitment, ultimately forming a self-reinforcing positive feedback loop between CFs and macrophages via IFN-IFNAR-p-STAT1 that inhibits cardiac reprogramming in vivo. Cumulatively, our findings uncover an intercellular self-stimulating inflammatory circuit as a microenvironmental molecular barrier of in situ cardiac reprogramming that needs to be overcome for regenerative medicine applications.
Animals ; Mice ; Macrophages/immunology* ; Fibroblasts/cytology* ; Cellular Reprogramming ; STAT1 Transcription Factor/genetics* ; Signal Transduction ; Interferon-beta/genetics* ; Myocardial Infarction/pathology* ; Myocytes, Cardiac/cytology* ; Mice, Inbred C57BL ; GATA4 Transcription Factor/genetics* ; Male ; Cells, Cultured

OBJECTIVETo investigate the effect of immune response mediated by antigen (oxidized low density lipoprotein, oxLDL)-specific T cells on plaque stability in coronary heart disease.

METHODSTwenty patients with acute myocardial infarction (AMI), 34 with unstable angina pectoris (UAP), 27 with stable angina pectoris (SAP) and 22 control subjects were enrolled in this study. MTS/PMS colorimetric assay was used to measure the proliferative response of the T cells to stimulation to 5 microg/ml oxLDL and detect IFN-gamma concentration produced in the proliferative response. The effect of C-reactive protein (CRP) on the proliferative response of the T cells to oxLDL and IFN-gamma concentration produced was examined in AMI group and UAP group.

RESULTSThe proliferative response of T cells to stimulation to 5 microg/ml oxLDL was significantly higher in AMI group and UAP group than in SAP group and the control group (P<0.05). IFN-gamma concentration produced in the proliferative response of the T cells was also significantly higher in AMI group and UAP group than in the other two groups (P<0.05). CRP at 10 microg/ml significantly increased the proliferative response of the T cells to oxLDL and IFN-gamma production in ACS group (P<0.001).

CONCLUSIONThe immune response mediated by the antigen-specific T cells, especially that mediated by type 1 T helper cells secreting IFN-gamma, may play an important role in the instability of plaques, and CRP may promote the inflammation of atherosclerosis through the effects on the specific immune response to oxLDL.

Aged ; Angina Pectoris ; immunology ; metabolism ; pathology ; Angina, Unstable ; immunology ; metabolism ; pathology ; C-Reactive Protein ; metabolism ; Case-Control Studies ; Coronary Disease ; immunology ; metabolism ; pathology ; Female ; Humans ; Male ; Middle Aged ; Myocardial Infarction ; immunology ; metabolism ; pathology ; Plaque, Atherosclerotic ; immunology ; metabolism ; pathology ; T-Lymphocytes ; metabolism

Endomyocardial biopsy often fails to show myocardial inflammation for patients with clinically suspected myocarditis. The serum isoforms of troponin T (cTnT) level is a very sensitive marker of myocardial injury and it is elevated even in the absence of myocardial inflammation. We investigated the correlations for myocardial injury, virus titers and inflammation in acute viral infection. Using the murine coxsackievirus group B3 (CVB3) myocarditis model, the histopathologic findings and virus titers in mouse hearts were compared with the serum cTnT levels measured by ELISA at various time points. Viable virus titers in the hearts peaked at 3 days after infection (8.22+/-0.13 log10 PFU/100 mg of heart); they decreased at day 7 and no viable virus was detected from day 14. Myocardial inflammation was minimal at day 3, peaked at day 7 and markedly decreased at day 14. The individual serum TnT levels were significantly increased at day 3 (7.37+/-1.46 ng/ml), persisted to day 7 (0.73+/-0.08 ng/ml), and normalized at day 14. Serum cTnT levels were correlatable with virus titers in the heart (r=0.744, P <0.01), but the serum cTnT levels were not correlated with the degrees of inflammation. Using the less myocarditic strain of CVB3, similar relationships were observed between the changes for the serum cTnT levels and the heart virus titers. During the course of viral infection, myocardial injury precedes the pathologic evidence of inflammation, and the elevated cTnT levels provide evidence of myocardial injury even in the absence of any histologic findings of myocarditis.
Acute Disease ; Animals ; Coxsackievirus Infections/*pathology ; Enterovirus B, Human/isolation & purification/pathogenicity/*physiology ; Female ; Heart/*virology ; Hela Cells ; Humans ; Inflammation/*immunology ; Mice ; Mice, Inbred BALB C ; Myocardial Infarction/immunology/*pathology ; Myocarditis/immunology/pathology/*virology ; *Myocardium/immunology/pathology ; Research Support, Non-U.S. Gov't ; Troponin T/blood ; Virus Replication

This study was designed to investigate the increase in the number of circulating CD34+ cells after acute myocardial infarction (MI) and the differentiation of these cells to cardiomyocytes after transplantation into infarcted myocardium. The study involved five donor groups: MI (n=27), sham (n=26), granulocyte-colony stimulating factor (GCSF) (n=26), MI+GCSF (n=25), and control (n=25). Acute MI was induced by ligating the left anterior descending coronary arteries (LAD) of donor rats, and LAD of recipient rats were ligated on the same day. Seven days after ligation, CD34+ cells in donor rats were counted and then were directly injected into the infarcted myocardium of recipient rats. Eight weeks after the transplantation, significant differences (p<0.001) were observed in the CD34+cell counts among the 5 donor groups with the greatest increase in the MI+GCSF donor group. In rats receiving CD34+ cells, the size of the scar area smaller (p<0.001) and the thickness of the scar was greater (p=0.001) than in CD34- and saline-transplanted rats. The transplanted CD34+ cells differentiated into cardiomyocytes in the scar. This study suggests that CD34+ cells may be a potential source of stem cells and that they may be useful in strategies aimed at the regeneration of infarcted myocardium.
Animals ; Antigens, CD34/*analysis ; Body Weight ; Cell Differentiation ; Heart/*physiology ; Myocardial Infarction ; Myocardium/*cytology/pathology ; Myocytes, Cardiac/*physiology ; Rats ; *Regeneration ; *Stem Cell Transplantation ; Stem Cells/*immunology/metabolism ; Support, Non-U.S. Gov't