| Part Ⅰ Expansion of Circulating Myeloid-derived Suppressor Cells in Patients with Acute Coronary SyndromeObjective Myeloid-derived suppressor cells(MDSCs)are a phenotypically diverse population of bone marrow derived myeloid progenitor cells and immature myeloid cells with defects in differentiation.MDSCs are the main cell type produced to negatively regulate the immune response which have been demonstrated to function under a variety of pathological conditions,such as tumor,infection,autoimmune,and chronic inflammation et.al.However,little is known about the role of MDSCs in the pathological process of AS.The purpose of this study is to investigate whether the circulating frequency and function of MDSCs are altered in patients with acute coronary syndrome(ACS).Methods In total,169 subjects were enrolled in this study,including 73 ACS patients,40 stable angina(SA)patients and 56 control patients.The blood samples were obtained,and then the plasma was stored at-20℃ for later use.Peripheral blood mononuclear cells(PBMCs)in the blood were isolated by Ficoll-Hypaque density gradient centrifugation.The frequency of MDSCs in PBMCs was detennined by flow cytometry.CD14+HLA-DR/low MDSCs and T cells were purified by magnetic activated cell sorting in sterile conditions.The mRNA expression in purified MDSCs was analyzed by real-time reverse transcription polymerase chain reaction(RT-PCR).T cells proliferation and cytokine secretion were respectively determined by using a scintillation counter and enzyme-linked immunosorbent assay(ELISA)in MDSCs-T cells co-culture system.The plasma levels of certain cytokines were determined using Bio-Plex ProTM Human Cytokine Assays.Results The frequency of circulating CD14+HLA-DR-/low MDSCs were markedly increased in ACS patients compared to stable angina(SA)or control patients.The arginase-1(Arg-1)mRNA expression in MDSCs purified from ACS patients was also significantly upregulated compared with these from stable angina(SA)or control patients.Furthermore,MDSCs from ACS patients were more potent suppressors of T-cell proliferation and IFN-γ production than those from the SA or control groups,which could be partially abrogated after administration of the Arg-1 inhibitor nor-NOHA.In addition,the plasma levels of interleukin(IL)-1β,IL-6,tumor necrosis factor(TNF)-a,and IL-33 were markedly increased in ACS patients compared to stable angina(SA)or control patients.Importantly,the frequency of MDSCs was positively correlated with plasma levels of IL-6,IL-33,and TNF-α.Conclusions The frequency of circulating CD14+HLA-DR-/low MDSCs were markedly increased in ACS patients,and the immunosuppressive effect of MDSCs was also elevated in ACS patients which was partially mediated by Arg-1.The expansion of MDSCs may be associated with the expression levels of cytokines.The results suggest the involvement of MDSCs in the pathological development and progression of ACS.Part Ⅱ Myeloid-derived Suppressor Cells ameliorate Cardiac Function and Ventricular Remodeling after Acute Myocardial InfractionObjective Ventricular remodeling is a basic pathophysiological mechanismin the development of chronic heart failure after acute myocardial infarction(AMI),in which innate and acquired immunity both play a pivotal role.The aim of this study is to explore the effect of MDSCs on the cardiac function and ventricular remodeling after AMI.Methods Ligation of the left anterior descending(LAD)coronary artery was performed to induce AMI in C57BL/6 mice.The same procedure without ligation of LAD coronary artery was carried out in sham-operated mice.The frequency of Gr-1+CD11b+MDSCs in bone marrow,spleen,blood,lymph nodes and infiltrating cells in heart tissueat at different time points was determined by flow cytometry.Gr-1+MDSCs were purified by magnetic sorting.AMI mice were randomly placed into three experimental groups:1)AMI+MDSCs,in which mice were adoptively transferred with 5×105Gr-1+MDSCs;2)AMI+Con,in which mice were adoptively transferred with 5×105Gr-1-cells;3)AMI,in which mice were received equal volume of normal saline(NS).Infarct size,cardiac function and fibrosis in the peri-infarct zone(PIZ)andnon-infarct zone(NIZ)were respectively evaluated by using TTC staining,echocardiography analysis and Masson’s trichrome.Results It showed a dynamic change of Gr-1+CD1b+MDSCs frequency in different immune organs.Compared with AMI group and AMI+Con group mice,the infract size on day 1 after AMI was decreased in AMI+MDSCs group mice.The cardiac function analysis revealed that mice in the AMI+MDSCs group showed increased left ventricular ejection fraction(LVEF)and elevated left ventricular fractional shortening(LVFS).Furthermore,interstitial fibrosis in PIZ and NIZ was markedly attenuated in mice of AMI+MDSCs group as compared with those from AMI and AMI+Con group.In addition,mice in AMI+MDSCs group showed higher survival rates than mice in AMI and AMI+Con group.Conclusions The dynamic change of Gr-1+CD11b+MDSCs frequency existed in mice after AMI.Mice receiving adoptively transferred MDSCs demonstrated improved cardiac function and ameliorated ventricular remodeling.MDSCs may serve as an endogenous protective mechanism,thus against adverse ventricular remodeling after myocardial infarction.Part Ⅲ Myeloid-derived Suppressor Cells inhibit Inflammatory Response and Cardiomyocyte Apoptosis after Acute Myocardial InfractionObjective Infarction-induced inflammatory response mediates apoptosis of survival cardiomyocyte,and promotes the development of adverse ventricular remodeling.This study aims to test the hypothesis that the role of MDSCs on ventricular remodeling is associated with its inhibition on inflammatory response and cardiomyocyte apoptosis.Methods Ligation of the left anterior descending(LAD)coronary artery was performed to induce AMI in C57BL/6 mice.The same procedure without ligation of LAD coronary artery was carried out in sham-operated mice.Gr-1+MDSCs were purified by magnetic sorting.AMI mice were randomly placed into three experimental groups:1)AMI+MDSCs,in which mice were adoptively transferred with 5×105Gr-1+MDSCs;2)AMI+Con,in which mice were adoptively transferred with 5×105Gr-1-cells;3)AMI,in which mice were received equal volume of normal saline(NS).Inflammatory cytokines mRNA expression levels in heart on day 7 were measured by using RT-PCR.The frequency of Thl,Th2,Th17 and regulatory T cells(Tregs)in CD4+ T cells of spleen was analyzed by flow cytometry.CD3+T cells infiltrationin the PIZ ofhearts was determined using immunehistochemistry.Neonatal cardiomyocytes were isolated and co-cultured with MDSCs.TUNEL staining was conducted to test cardiomyocyte apoptosis for heart slices and co-cultured NCMs.Results It showed decreased mRNA expression levels of pro-inflammatory cytokines(TNF-α、IL-1β、IL-17)and chemokines(Cxcl-1、Cxcl-1)in infracted heart of mice from AMI+MDSCs group,compared with those from AMI and AMI+Con groups.However,anti-inflammatory cytokine TGF-β1 and IL-10 mRNA expression in the infracted hearts was markedly up-regulated in AMI+MDSCs group mice.The number of CD3+T cells infiltration in the PIZ of hearts was also decreased in AMI+MDSCs group mice.Meanwhile,there was no significant difference of T cell subsets including Thl,Th2,Th17,and Tregs among mice in different groups.Furthermore,increased number of TUNEL-positive cardiomyocytes in PIZ of infracted heart was demonstrated in AMI+MDSCs group mice.In addition,MDSCs inhibit LPS induced cardiomyocyte apoptosis in the NCMs and MDSCs co-culture system,which can be partially abolished by the block of cell-to-cell contact.Conclusions MDSCs inhibit infarction-induced inflammatory response and had anti-apoptosis effect on cardiomyocytes,thus against adverse ventricular remodeling after myocardial infarction. |
