Macrophages and vimentin in tissues adjacent to megaprostheses and mesh in reconstructive surgeries

In reconstructive surgery using artificial materials after wide resection, soft tissues are usually adjacent to metal surfaces or mesh. The purpose of this study was to provide histological evaluation of the soft tissues adjacent to the metal surfaces of megaprostheses and mesh. Tissues from revision surgery of megaprosthesis and from wide resection after recurrent thoracic wall sarcoma were used. Histological analysis was evaluated by hematoxylin/eosin (HE) and Masson's trichrome staining, and by immunohistochemical staining for markers including cluster of differentiation 68 (CD68), vimentin, collagen type and S100A4. Soft tissue adherence to the smooth metal surface of Ti alloy was not observed. On the surface of capsule, CD68- and vimentin-positive cells formed a thin layer. In contrast, soft tissue adherence to a rough-surface cobalt chrome alloy was observed. Capsule was not apparent for this tissue, in which CD68- and vimentin-positive cells were aggregated randomly. In the resected tissues of recurrent chest wall sarcoma, muscles showed connections to connective soft tissues but did not invade to the inside of the mesh. Around the polypropylene mesh, large numbers of CD68- and vimentin-positive cells were seen. On the ePTFE, small numbers of CD68-positive cells were observed, while a larger number of the cells were vimentin positive. High accumulation of S100A4-positive cells was observed at the metal surface and polypropylene surface. Cells were strongly positive for CD68 and vimentin in tissues adjacent to metal and mesh surfaces. Macrophages and vimentin may play important roles in the foreign body reaction to metal and mesh, and so may contribute to encapsulation and fibrosis.