Histologic response to intradermal Zyderm and Zyplast (glutaraldehyde cross-linked) collagen in humans.

Biopsies were periodically taken over 6 months from sites injected intradermally with purified bovine collagen, Zyderm collagen implant, and a similar collagen, cross-linked with glutaraldehyde, Zyplast implant. The ultimate fate of the implants differed. Zyderm collagen was dispersed among host collagen fibers and gradually lost the appearance of a cohesive implant. By 90 days, the injected material could not be detected and was presumably resorbed, without becoming colonized by host fibroblasts. In contrast, the cross-linked implant remained as distinct foci for 3 to 6 months accompanied by massing of fibroblasts around the periphery. These fibroblasts subsequently invaded the implant and provoked an inflammatory reaction which replaced the implant by new host collagen. The fine collagen bundles in parallel arrays along with many small blood vessels were deposited in the site formerly occupied by the implant. These findings indicate that Zyplast collagen might provide longer-lasting correction of soft tissue defects.