title: Fibroplasia after polypropylene mesh implantation for abdominal wall hernia repair in rats.
abstract: OBJECTIVE
  This study assessed the collagen deposition and correlated it with local inflammatory responses to evaluate the length of time required for fibroplasia when polypropylene meshes are used to repair incisional abdominal wall hernias in rats.
  
  
  METHODS
  Thirty-six male Wistar rats underwent longitudinal resection of a peritoneal and musculoaponeurotic tissue segment (3x2 cm) of the abdominal wall followed by defect reconstruction with polypropylene mesh bridging over aponeurosis. The animals were divided into 6 groups according to the time points for the analysis of fibroplasia: 1, 2, 3, 7, 21 and 30 days post-implantation. Animals were sacrificed at each time point, and the site where the polypropylene mesh was implanted was evaluated histologically to assess inflammatory response and percentage of collagen using computer-assisted videomorphometry.
  
  
  RESULTS
  Total collagen was found at the mesh site on the 3rd day post-implantation, and increased progressively on all subsequent days up to the 21st day, when it reached its highest percentage (p<0.001). Type III collagen increased progressively from the 3rd to the 21st days, when it reached its highest percentage (p<0.001); on the 30th day, it decreased significantly (p>0.001). Type I collagen was first found between the 7th and 21st days; it reached its highest percentage on the 21st day and then remained stable until the 30th day. The type I to type III collagen ratio increased significantly and progressively up to the 30th day (p<0.001). Neutrophils were found at the mesh site from the 1st to the 21st day post-implantation. Macrophages, giant cells and lymphocytes were seen on the 2nd day. Thirty days after mesh implantation, neutrophils disappeared, but the percentages of macrophages, giant cells and lymphocytes remained stable (p<0.001).
  
  
  CONCLUSIONS
  This study showed that total collagen was first seen on the 3rd day post-implantation, with a higher percentage of type I collagen at the last observational time point. The prolonged healing inflammatory response and the persistence of chronic inflammation surrounding to the mesh did not affect the length of time required for fibroplasia.
authors.affiliation: Department of Surgery, Division of Gastrointestinal Surgery, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil. marvaz@terra.com.br
authors.forename: Márcia
authors.initials: M
authors.lastname: Vaz
authors.forename: Rodrigo Ketzer
authors.initials: RK
authors.lastname: Krebs
authors.forename: Eduardo Neubarth
authors.initials: EN
authors.lastname: Trindade
authors.forename: Manoel Roberto Maciel
authors.initials: MR
authors.lastname: Trindade
mesh_terms: D000818:Animals; D003094:Collagen / Q000032:analysis*; D024042:Collagen Type I / Q000032:analysis; D024061:Collagen Type III / Q000032:analysis; D006555:Hernia, Ventral / Q000601:surgery*; D020007:Implants, Experimental; D007249:Inflammation / Q000473:pathology; D008297:Male; D008422:Materials Testing; D009504:Neutrophils / Q000737:chemistry; D011126:Polypropylenes; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013526:Surgical Mesh / Q000009:adverse effects; D013530:Surgical Wound Infection / Q000209:etiology; D013997:Time Factors; D014945:Wound Healing / Q000502:physiology*
chemical_list: D024042:Collagen Type I; D024061:Collagen Type III; D011126:Polypropylenes; D003094:Collagen