title: Stent implantation into the tracheo-bronchial system in rabbits: histopathologic sequelae in bare metal vs. drug-eluting stents.
abstract: BACKGROUND
  Stent implantation into the tracheo-bronchial system may be life-saving in selected pediatric patients with otherwise intractable stenosis of the upper airways. Following implantation, significant tissue proliferation may occur, requiring re-interventions. We sought to evaluate the effect of immunosuppressive coating of the stents on the extent of tissue proliferation in an animal model.
  
  
  METHODS
  Bare metal and sirolimus-coated stents (Bx Sonic and Cypher Select, Johnson & Johnson, Cordis) were implanted into non-stenotic lower airways of New Zealand white rabbits (weight 3.1 to 4.8 kg). Three stents with sirolimus coating and six bare metal stents could be analyzed by means of histology and immunohistochemistry 12 months after implantation.
  
  
  RESULTS
  On a macroscopic evaluation, all stents were partially covered with a considerable amount of whitish tissue. Histologically, these proliferations contained fiber-rich connective tissue and some fibromuscular cells without significant differences between both stent types. The superficial tissue layer was formed by typical respiratory epithelium and polygonal cells. Abundant lymphocyte infiltrations and moderate granulocyte infiltrations were found in both groups correspondingly, whereas foreign-body reaction was more pronounced around sirolimus-eluting stents.
  
  
  CONCLUSIONS
  After stent implantation in the tracheo-bronchial system of rabbits, we found tissue reactions comparable to those seen after stent implantation into the vascular system. There was no difference between coated and uncoated stents with regard to quality and quantity of tissue proliferation. We found, however, a significantly different inflammatory reaction with a more pronounced foreign-body reaction in sirolimus-coated stents. In our small series, drug-eluting stents did not exhibit any benefit over bare metal stents in an experimental setting.
authors.affiliation: Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University Göttingen, Robert Koch Strasse 40, D 37075, Göttingen, Germany. msigler@gwdg.de.
authors.forename: Matthias
authors.identifier: http://orcid.org/0000-0002-4110-7694
authors.initials: M
authors.lastname: Sigler
authors.affiliation: Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University Göttingen, Robert Koch Strasse 40, D 37075, Göttingen, Germany. JuliaKloetzer@gmx.de.
authors.forename: Julia
authors.initials: J
authors.lastname: Klötzer
authors.affiliation: Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University Göttingen, Robert Koch Strasse 40, D 37075, Göttingen, Germany. tquentin@gmx.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Quentin
authors.affiliation: Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University Göttingen, Robert Koch Strasse 40, D 37075, Göttingen, Germany. tpaul@gwdg.de.
authors.forename: Thomas
authors.initials: T
authors.lastname: Paul
authors.affiliation: Department of Pediatric Cardiology and Intensive Care Medicine, University Medical Center, Georg August University Göttingen, Robert Koch Strasse 40, D 37075, Göttingen, Germany. o.moeller@eichsfeld-klinikum.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Möller
keywords: Airway stent; Drug-eluting stent; Granulation tissue; Histology; Tracheomalacia