Immunohistochemical study of the biological fate of a subcutaneous bovine collagen implant in rat.

The biological fate of a bovine collagen implant (Zyderm Collagen Implant ZCI), injected subcutaneously into rats, was studied by the immunoperoxidase technique using specific antibodies against the bovine implant and against types I, III, IV, V collagens, fibronectin and elastin. The implant remained in the animals until the end of the experiment (90 days), with no visible modification, as demonstrated by immunoperoxidase labelling and scanning electron microscopy. A slight inflammatory reaction was visible around the implant 24 h after injection and within the implant 3 days after injection. Fibroblast invasion began 7 days after injection. The chronology of the deposition in the implant of the host (rat) extracellular matrix components was as follows: by 24 h after injection, fibronectin was observed throughout the implant; types I and V collagens appeared on the 7th day, and, in contrast to surrounding connective tissue, type V collagen labelling was obtained without acid pretreatment of the section. Types III and IV collagens were detected inside the implant only 30 days after injection. At the end of the experiment (90 days), there was abundant types I and IV collagens after fibroblast migration, and abundant type IV collagen demonstrating an important vascularization. No elastic fibres could be detected inside the implant but they appeared as a dense network around the implant in host connective tissue.