title: Roles of microRNA-34a targeting SIRT1 in mesenchymal stem cells.
abstract: BACKGROUND
  Mesenchymal stem cell (MSC)-based therapies have had positive outcomes both in animal models of cardiovascular diseases and in clinical patients. However, the number and function of MSCs decline during hypoxia and serum deprivation (H/SD), reducing their ability to contribute to endogenous injury repair. MicroRNA-34a (miR-34a) is originally identified as a TP53-targeted miRNA that modulates cell functions, including apoptosis, proliferation, and senescence via several signaling pathways, and hence is an appealing target for MSC-based therapy for myocardial infarction.
  
  
  METHODS
  Bone marrow-derived MSCs were isolated from 60-80 g male donor rats. Expression levels of miR-34a were determined by qRT-PCR. The roles of miR-34a in regulating cell vitality, apoptosis and senescence were investigated using the cell counting kit (CCK-8) assay, flow cytometric analysis of Annexin V-FITC/PI staining and senescence-associated β-galactosidase (SA-β-gal) staining, respectively. The expression of silent information regulator 1 (SIRT1) and forkhead box class O 3a (FOXO3a) and of apoptosis- and senescence-associated proteins in MSCs were analyzed by western blotting.
  
  
  RESULTS
  The results of the current study showed that miR-34a was significantly up-regulated under H/SD conditions in MSCs, while overexpression of miR-34a was significantly associated with increased apoptosis, impaired cell vitality and aggravated senescence. Moreover, we found that the mechanism underlying the proapoptotic function of miR-34a involves activation of the SIRT1/FOXO3a pathway, mitochondrial dysfunction and finally, activation of the intrinsic apoptosis pathway. Further study showed that miR-34a can also aggravate MSC senescence, an effect which was partly abolished by the reactive oxygen species (ROS) scavenger, N-acetylcysteine (NAC).
  
  
  CONCLUSIONS
  Our study demonstrates for the first time that miR-34a plays pro-apoptotic and pro-senescence roles in MSCs by targeting SIRT1. Thus, inhibition of miR-34a might have important therapeutic implications in MSC-based therapy for myocardial infarction.
authors.affiliation: Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 805137949@qq.com.|Department of Cardiology, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 805137949@qq.com.
authors.forename: Fengyun
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 281642428@qq.com.|Department of Cardiology, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 281642428@qq.com.
authors.forename: Jinjin
authors.initials: J
authors.lastname: Cui
authors.affiliation: Department of Cardiology, Mudanjiang Forestry Central Hospital, 50 XinhuaRoad, Mudanjiang, 157000, P.R. China. zy6216298@163.com.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Liu
authors.affiliation: Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 2855928554@qq.com.|Department of Cardiology, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 2855928554@qq.com.
authors.forename: Bo
authors.initials: B
authors.lastname: Lv
authors.affiliation: Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 1003032116@qq.com.|Department of Cardiology, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 1003032116@qq.com.
authors.forename: Xinxin
authors.initials: X
authors.lastname: Liu
authors.affiliation: Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 523781601@qq.com.|Department of Cardiology, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. 523781601@qq.com.
authors.forename: Zulong
authors.initials: Z
authors.lastname: Xie
authors.affiliation: Key Laboratories of Education Ministry for Myocardial Ischemia Mechanism, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. dryu_hmu@163.com.|Department of Cardiology, The Second Affiliated Hospital of Harbin Medical University, 148 Baojian Road, Harbin, 150086, P.R. China. dryu_hmu@163.com.
authors.forename: Bo
authors.initials: B
authors.lastname: Yu
mesh_terms: D000818:Animals; D017209:Apoptosis; D002478:Cells, Cultured; D016922:Cellular Senescence; D008297:Male; D059630:Mesenchymal Stem Cells / Q000378:metabolism* / Q000502:physiology; D035683:MicroRNAs / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D056564:Sirtuin 1 / Q000235:genetics* / Q000378:metabolism
chemical_list: C560944:MIRN34 microRNA, rat; D035683:MicroRNAs; C488368:Sirt1 protein, rat; D056564:Sirtuin 1