The foreign body reaction to a biodegradable biomaterial differs between rats and mice

Before a biomaterial can be applied in the clinic, biocompatibility must be tested in in vivo models, by monitoring the foreign body reaction. In this study, we compared the foreign body reaction (EBR) to the biodegradable bi omaterial hexamethylenediisocyanate crosslinked dermal sheep collagen (HDSC ) between several strains of rats and mice HDSC disks were implanted subcut aneously on the backs of AO, BN, F344, LEW, and PVG rats and on the backs o f 129 SVEV, BALB/c, and C57BL/6 mice. Materials were explanted after 7, 14, 21, and 28 days and processed for (immuno) light and transmission electron microscopic evaluation. In all rat strains, giant cell formation and phago cytosis of HDSC bundles were comparable. In addition, in the PVG rat, many plasma cells infiltrated the HDSC disks. Only a few T cells were present in AO and PVG rats, whereas, in F344 and LEW rats, the presence of T cells wa s more pronounced. BN rats showed an intermediate T-cell infiltration. In m ice, the FBR to HDSC was comparable between the different strains. Compared with rats, giant cell formation was limited, whereas stroma formation was more abundant. Phagocytosis of HDSC bundles rarely occurred in mice, wherea s calcification was observed more often. It is concluded that the FBR to HD SC clearly differs between rats and mice. This has consequences for assessm ent studies on biocompatibility and also on fundamental biomaterial researc h. (C) 2000 John Wiley & Sons, Inc.