Preclinical Evaluation of Mesh Implants: The Pathologist's Perspective

Surgical and laparoscopic implantation of mesh devices is on the rise for a variety of applications. The complexity and range of evolving mesh designs calls for consistent and detailed pathologic evaluation in determining host responses and assessing overall safety. This review addresses the components of evaluation of mesh implants in animal models, with emphasis on histologic parameters, semiquantitative scoring matrices, and morphometric analyses that have been specifically adapted to this class of implants. Necropsy assessment should include implant persistence, architecture, and associated host responses such as exudation and adhesions. Microscopic evaluation should focus on primary relevant responses such as bioresorption, integration/tissue ingrowth, neovascularization, and inflammation. Selection of the best means of processing and evaluation can be complicated, as meshes may include one or more biologic components (e.g., collagen), synthetic polymer fibers, coatings, and other molecules. The architecture of some meshes can influence tissue responses and complicate sampling, sectioning, and evaluation. Recognition of specific study objectives and knowledge of anticipated responses helps to determine the appropriate histologic or immunochemical stains, while understanding of mesh composition and anticipated persistence in tissue determines the suitability of paraffin or resin embedding, and both guide the evaluation of mesh devices in the preclinical setting.