title: Significant role for microRNA-21 affecting toll-like receptor pathway in primary graft dysfunction after human lung transplantation.
abstract: BACKGROUND
  MicroRNAs (miRNAs) were recently identified as modulators of immune responses after human lung transplantation (LTx). This study was undertaken to assess the contribution of miRNAs to the pathogenesis of primary graft dysfunction (PGD) after LTx.
  
  
  METHODS
  Of the 39 recipients, 14 (35.9%) developed Grade 3 PGD (i.e., severe PGD) within the first 72 hours of LTx. The remaining 25 recipients (64.1%) had Grade 2 or less PGD, and served as the control group. miRNAs were isolated from cells purified by bronchoalveolar lavage (BAL). Bioinformatic prediction and validation by luciferase reporter assays were performed to identify targets regulated by miR-21. Transfection of human monocytic cell line (THP-1) was conducted to determine miR-21's cellular function.
  
  
  RESULTS
  Pilot miRNA profiling of donor BAL samples before implantation in PGD (n = 6) revealed significant upregulation in 44 miRNAs and downregulation in 80 miRNAs compared with control (n = 6). Validation using a separate cohort demonstrated significant underexpression of miR-21 in patients with severe PGD. Furthermore, underexpression of miR-21 levels was negatively correlated with clinical PGD grades (Grade 2 PGD vs Grade 0 PGD: p = 0.042; Grade 3 PGD vs Grade 0 PGD: p = 0.004). Molecular analysis demonstrated that miR-21 targeted key components in the toll-like receptor (TLR) signaling pathway, including TLR4, IRAK3 and CXCL10. Further, incubation of THP-1 cells with cell-free BAL from severe PGD resulted in transactivation of inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). In contrast, increased expression of miR-21 resulted in marked suppression of IL-1-β and TNF-α production.
  
  
  CONCLUSIONS
  Underexpression of miR-21 may lead to the development of severe PGD by activating key components of the TLR pathway.
authors: Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA; Norton Thoracic Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors: Zhongping
authors: Z
authors: Xu
authors: Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA; Norton Thoracic Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors: Monal
authors: M
authors: Sharma
authors: Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.
authors: Andrew
authors: A
authors: Gelman
authors: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, USA.
authors: Ramsey
authors: R
authors: Hachem
authors: Department of Surgery, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA; Norton Thoracic Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA. Electronic address: tm.kumar@dignityhealth.org.
authors: Thalachallour
authors: T
authors: Mohanakumar
mesh_terms: D000328:Adult; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid; D015331:Cohort Studies; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D016040:Lung Transplantation / Q000009:adverse effects* / Q000379:methods; D008297:Male; D035683:MicroRNAs / Q000235:genetics*; D008875:Middle Aged; D055031:Primary Graft Dysfunction / Q000235:genetics* / Q000503:physiopathology; D011379:Prognosis; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D015398:Signal Transduction / Q000235:genetics; D051193:Toll-Like Receptors / Q000235:genetics*
chemical_list: C524940:MIRN21 microRNA, human; D035683:MicroRNAs; D051193:Toll-Like Receptors
keywords: lung transplantation; microRNAs; primary graft dysfunction