title: Histologic analysis of acellular dermal matrix in the treatment of anal fistula in an animal model.
abstract: BACKGROUND
  Human acellular dermal matrix (ADM) has been used successfully for the treatment of severe burns, ureter support, and abdominal wall reconstruction. This study was designed to evaluate the mechanism of ADM in the closure of anal fistula in an experimental porcine model.
  
  
  METHODS
  The fistula-in-ano model was created in the porcine model and treated with ADM in 14 animals. Fistula specimens were obtained at hours 12 and 24 and on days 3, 7, 14, 28, 60. Hematoxylin and eosin staining, Masson trichrome staining, and immunohistochemical staining for alpha smooth muscle actin and matrix metalloproteinase 9 were performed.
  
  
  RESULTS
  The cell density increased from hour 12 to day 7 and decreased from day 7 to day 28 (p < 0.001). Mature vessels stained with alpha smooth muscle actin were identified at day 7. Alpha smooth muscle actin-positive myofibroblasts were found in clusters at the edge of the ADM at day 7. The density of vessels (p < 0.001) and myofibroblasts (p < 0.001) increased from day 7 to day 14. The density of matrix metalloproteinase 9 increased from hour 12 to day 7 and decreased from day 14 to day 60 (p < 0.001). Partially organized bundles of muscle were found by day 60.
  
  
  CONCLUSIONS
  We suggest that ADM is a reasonable new option for closure of anal fistulas. Anal fistulas begin to heal as early as 12 hours, and day 7 may be an important time point to judge whether the fistula healed preliminarily or not. The ability of ADM to become vascularized and remodeled by autologous cells may be advantageous for anal fistula healing.
authors.affiliation: Department of General Surgery, Beijing Chaoyang Hospital, Capital Medical University, Beijing, PR China.
authors.forename: Jia Gang
authors.initials: JG
authors.lastname: Han
authors.forename: Hui Min
authors.initials: HM
authors.lastname: Xu
authors.forename: Wei Liang
authors.initials: WL
authors.lastname: Song
authors.forename: Mu Lan
authors.initials: ML
authors.lastname: Jin
authors.forename: Jia Sen
authors.initials: JS
authors.lastname: Gao
authors.forename: Zhen Jun
authors.initials: ZJ
authors.lastname: Wang
authors.forename: Xin Qing
authors.initials: XQ
authors.lastname: Yang
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D002465:Cell Movement; D049109:Cell Proliferation; D004195:Disease Models, Animal; D005347:Fibroblasts / Q000502:physiology; D006801:Humans; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis; D018919:Neovascularization, Physiologic / Q000502:physiology; D012003:Rectal Fistula / Q000473:pathology / Q000601:surgery*; D017768:Skin, Artificial; D013552:Swine; D054457:Tissue Scaffolds
chemical_list: D001672:Biocompatible Materials; D020780:Matrix Metalloproteinase 9