title: Mesenchymal stem cells modified with miR-126 release angiogenic factors             and activate Notch ligand Delta-like-4, enhancing ischemic angiogenesis and cell             survival.
abstract: The endothelial cell-specific microRNA (miRNA), miR-126, is considered a master regulator of physiological angiogenesis. Transplanted mesenchymal stem cells (MSCs) release soluble factors contributing to neoangiogenesis and cardiac repair. Therefore, we hypothesized that the over-expression of miR-126 may prolong MSC survival and enhance the cell secretome, thereby improving post-infarction angiogenesis and cardiac function. In this study, MSCs harvested from male C57BL/6 mouse bone marrow were infected in vitro with miR-126 (MSC(miR-126)) by using recombinant lentiviral vectors; the control cells were either non-transfected or transduced with mock vectors (MSC(null)). The results showed an increased secretion of angiogenic factors and a higher resistance against hypoxia in MSC(miR-126) compared with the control cells. The expression of the Notch ligand Delta-like (Dll)-4 in the MSC(miR-126) group was also increased. For in vivo experiments, MSC(miR-126) cultures were intramyocardially injected into the infarct region of the hearts of female C57BL/6 mice (an acute myocardial infarction model) who had undergone ligation of the left anterior descending coronary artery. The survival of MSC(miR-126) cultures, determined by Sry expression, was increased at 7 days after transplantation. MSC(miR-126)-treated animals showed significantly improved cardiac function as assessed by echocardiography 2 weeks later. The expression levels of angiogenic factors and Dll-4 in the infarcted myocardium were further increased by MSC(miR-126) compared with MSCs or MSC(null) cultures. Furthermore, fluorescent microsphere and histological studies revealed that myocardial blood flow and microvessel density were significantly increased in the MSC(miR-126)-transplanted animals. In addition, we found increased immature vessel proliferation following the transplantation of MSC(miR-126) cultures in which the expression of Dll-4 had been knocked down. However, blood vessels with lumen were barely detected, which indicated that Dll-4 plays a key role in tubulogenesis. We conclude that the transplantation of MSCs overexpressing miR-126 can further enhance functional angiogenesis in the ischemic myocardium possibly by the secretion of angiogenic factors and the activation of Dll-4, thus increasing MSC survival. Therefore, MSCs modified with miR-126 may represent a novel and efficient therapeutic approach for ischemic angiogenesis and the improvement of cardiac function.
authors.affiliation: Department of Cardiology, The Second Xiangya Hospital of Central                     South University, Changsha, Hunan 410011, P.R. China.
authors.forename: Feng
authors.initials: F
authors.lastname: Huang
authors.forename: Xiao
authors.initials: X
authors.lastname: Zhu
authors.forename: Xin-Qun
authors.initials: XQ
authors.lastname: Hu
authors.forename: Zhen-Fei
authors.initials: ZF
authors.lastname: Fang
authors.forename: Liang
authors.initials: L
authors.lastname: Tang
authors.forename: Xiao-Ling
authors.initials: XL
authors.lastname: Lu
authors.forename: Sheng-Hua
authors.initials: SH
authors.lastname: Zhou
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D043925:Angiogenesis Inducing Agents / Q000378:metabolism*; D000818:Animals; D002135:Calcium-Binding Proteins; D015687:Cell Hypoxia; D002470:Cell Survival; D002478:Cells, Cultured; D005260:Female; D006321:Heart / Q000503:physiopathology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods; D059630:Mesenchymal Stem Cells / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics*; D017202:Myocardial Ischemia / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D009206:Myocardium / Q000473:pathology; D018919:Neovascularization, Physiologic; D014162:Transfection; D015854:Up-Regulation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D043925:Angiogenesis Inducing Agents; D002135:Calcium-Binding Proteins; C519665:DLL4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; C545201:MIRN126 microRNA, mouse; D008565:Membrane Proteins; D035683:MicroRNAs