title: Fetal bladder wall regeneration with a collagen biomatrix and histological evaluation of bladder exstrophy in a fetal sheep model.
abstract: OBJECTIVE
  To evaluate histological changes in an animal model for bladder exstrophy and fetal repair of the bladder defect with a molecular-defined dual-layer collagen biomatrix to induce fetal bladder wall regeneration.
  
  
  METHODS
  In 12 fetal lambs the abdominal wall and bladder were opened by a midline incision at 79 days' gestation. In 6 of these lambs an uncorrected bladder exstrophy was created by suturing the edges of the opened bladder to the abdominal wall (group 1). The other 6 lambs served as a repair group, where a dual-layer collagen biomatrix was sutured into the bladder wall and the abdominal wall was closed (group 2). A caesarean section was performed at 140 days' gestation, followed by macroscopic and histological examination.
  
  
  RESULTS
  Group 1 showed inflammatory and maturational changes in the mucosa, submucosa and detrusor muscle of all the bladders. In group 2, bladder regeneration was observed, with urothelial coverage, ingrowth of fibroblasts and smooth muscle cells, deposition of collagen, neovascularization and nerve fibre formation. This tissue replaced the collagen biomatrix. No structural changes of the bladder were seen in group 2.
  
  
  CONCLUSIONS
  The animal model, as in group 1, for bladder exstrophy shows remarkable histological resemblance with the naturally occurring anomaly in humans. This model can be used to develop new methods to salvage or regenerate bladder tissue in bladder exstrophy patients. Fetal bladder wall regeneration with a collagen biomatrix is feasible in this model, resulting in renewed formation of urothelium, blood vessels, nerve fibres, ingrowth of smooth muscle cells and salvage of the native bladder.
authors.affiliation: Department of Urology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. L.Roelofs@uro.umcn.nl
authors.forename: Luc A J
authors.initials: LA
authors.lastname: Roelofs
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Eggink
authors.forename: Christina A
authors.initials: CA
authors.lastname: Hulsbergen-van de Kaa
authors.forename: Rene M H
authors.initials: RM
authors.lastname: Wijnen
authors.forename: Toin H
authors.initials: TH
authors.lastname: van Kuppevelt
authors.forename: Herman T B
authors.initials: HT
authors.lastname: van Moerkerk
authors.forename: A Jane
authors.initials: AJ
authors.lastname: Crevels
authors.forename: Alex
authors.initials: A
authors.lastname: Hanssen
authors.forename: Fred K
authors.initials: FK
authors.lastname: Lotgering
authors.forename: Paul P
authors.initials: PP
authors.lastname: van den Berg
authors.forename: Wout F J
authors.initials: WF
authors.lastname: Feitz
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000627:therapeutic use*; D001746:Bladder Exstrophy / Q000196:embryology / Q000473:pathology / Q000601:surgery*; D003094:Collagen / Q000627:therapeutic use*; D004195:Disease Models, Animal; D005315:Fetal Diseases / Q000473:pathology / Q000601:surgery*; D005333:Fetus / Q000473:pathology / Q000601:surgery*; D048091:Guided Tissue Regeneration; D012756:Sheep / Q000196:embryology; D054457:Tissue Scaffolds
chemical_list: D001672:Biocompatible Materials; D003094:Collagen