Pathological study of foreign body reaction on the implanted interface.

Abstract

Four kinds of polymer materials (polyurethane sheet, polyurethane beads, polysulfone powder, and polysulfone beads) were implanted into the subcutaneous tissue of F-344 male rats for 104 weeks. Subcutaneous tumors developed in 6 out of 20 rats with implanted polyurethane sheets. In the group with implanted polyurethane beads, 2 out of 20 rats also developed a subcutaneous tumor. All of these tumors were histologically diagnosed as malignant fibrous histiocytoma (MFH). No tumors were noted in the groups with implanted polysulfone powder or polysulfone beads. For investigation of early cellular reactions to implanted materials during foreign body carcinogenesis, polyurethane sheets were implanted into the subcutaneous tissue of F-344 male rats, and the implanted sites were examined by light and electron microscope at 2, 4, 8, and 12 weeks after implantation. Uptake of bromodeoxyuridine (BrdU) or 3H-thymidine was also studied with enzyme histochemistry or electron microscopic autoradiography. By 8 weeks after implantation, focal proliferation of atypical cells was observed in the subcutis adjacent to the polymer sheet. These atypical cells showed a high labeling index for BrdU as well as 3H-thymidine. These results indicate that atypical cell foci play the most important role as lesions in foreign body tumorigenesis.