Repetitive subcutaneous implantation of different types of (biodegradable)biomaterials alters the foreign body reaction

In the present study two biodegradable materials (cross-linked collagens) a nd two non-biodegradable materials (polyurethane and silicone) were applied in a repetitive subcutaneous implantation model in rats. In contrast to th e first challenge, the second challenge with the same type of material, but at a different subcutaneous site of the same animal, induced an increase o f macrophages and giant cells inside the biodegradable materials. Additiona lly, only after the second challenge clusters and accumulations of plasma c ells were present in the surrounding tissue of each type of material. Tn th e same areas an increase of MHC II expression was measured by immunocytoche mistry. Differences in the numbers of macrophages and T cells were not obse rved around the explants. Undifferentiated B cells or NK cells were not pre sent at any time point. The results indicate that alterations observed afte r the second challenge did not depend on biodegradation of the materials. S ignificance of these Endings should be considered in view of increased and repetitive use of the same type of biomaterial (possibly for different appl ication sites) for implantation in patients. (C) 2001 Elsevier Science Ltd. All rights reserved.