Collagen-coated vs noncoated low-weight polypropylene meshes in a sheep model for vaginal surgery. A pilot study

The aims of this study were dual. First, to evaluate the feasibility of a sheep model as an animal model for vaginal surgery with meshes. Second, to compare host response to two low-weight polypropylene (PP) meshes, a noncoated (Soft Prolene™, Gynecare, Ethicon) and a coated mesh with an absorbable hydrophilic film (Ugytex™, Sofradim). Thirty-six 20×20 mm polypropylene meshes (18 coated and 18 noncoated) were surgically implanted by the vaginal route in 12 adult ewes. Meshes were implanted in the anterior (n=12) and the posterior vaginal compartments (n=24). Animals were killed 1 (n=6) and 12 (n=6) weeks after surgery. Postimplantation evaluation included macroscopical examination, histological and immunohistochemical analysis and histomorphometrical measures of the distance between the meshes and the vaginal epithelium. The experimental procedure was feasible in all cases. Vaginal erosions were observed twice as frequently with the noncoated-PP meshes (6/18, 33.3%) as with the coated-PP meshes (3/18, 16.7%), even if that difference was not significant (p=0.4). However, no differences were observed between the two meshes in terms of shrinkage, tissue ingrowth, inflammatory response, and position of the mesh in the vaginal wall. The mechanism involved in the reduction of vaginal erosion could be due to the lesser adhesion of the coated mesh on the vaginal wound during the early postoperative period.