title: Evaluation of formation of granulation tissue caused by metallic stent placement in a rat urethral model.
abstract: OBJECTIVE
  To evaluate the feasibility of metallic stent placement and the formation of granulation tissue caused by stent placement in a rat urethral model.
  
  
  METHODS
  A bare self-expanding metallic stent was inserted in the urethra under fluoroscopic guidance in 20 male Sprague-Dawley rats. Ten rats were euthanized at 4 weeks (group A), and the other 10 were euthanized at 8 weeks after stent placement (group B). Stenosis diameter, number of epithelial layers, degree of inflammatory cell infiltration, thickness of submucosal fibrosis, and percentage of granulation tissue area were assessed.
  
  
  RESULTS
  Stent placement was technically successful in all rats. Urethrograms showed perforation in three rats, partial migration in three, and stone formation in four. Granulation tissue formation was observed in all rats at the stent-implanted urethra, and the average percentage of granulation tissue area accounted for 41% and 45% of the original urethral lumen area in groups A and B, respectively. Urethrograms and urethral specimens showed significantly less stenosis diameter, less thickness of submucosal fibrosis, and lower percentage of granulation tissue area in the proximal urethra than in the distal urethra in both groups (P < .05). Histologic results demonstrated significantly fewer epithelial layers in group B compared with group A (P = .028).
  
  
  CONCLUSIONS
  Placement of a self-expandable metallic stent proved to be feasible in the rat urethra and an efficient approach to stimulate granulation tissue formation as a potential model for reproducing the mechanisms of restenosis.
authors.affiliation: Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.
authors.forename: Yong-Dong
authors.initials: YD
authors.lastname: Li
authors.forename: Ho-Young
authors.initials: HY
authors.lastname: Song
authors.forename: Jin Hyoung
authors.initials: JH
authors.lastname: Kim
authors.forename: Cheol-Woong
authors.initials: CW
authors.lastname: Woo
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Park
authors.forename: Tae-Hyung
authors.initials: TH
authors.lastname: Kim
authors.forename: Gyungyub
authors.initials: G
authors.lastname: Gong
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005240:Feasibility Studies; D005355:Fibrosis; D006097:Granulation Tissue / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D008670:Metals; D011474:Prosthesis Design; D011859:Radiography; D051381:Rats; D017207:Rats, Sprague-Dawley; D015607:Stents / Q000009:adverse effects*; D013997:Time Factors; D014521:Urethra / Q000000981:diagnostic imaging / Q000473:pathology*; D014525:Urethral Stricture / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology*
chemical_list: D008670:Metals