Effect of tanning agent on tissue reaction to tissue implanted collagen sponge

Pure collagen, isolated from bovine skin, was reconstituted into the form of a sponge in the presence of either glutaraldehyde (GTA) or hexamethylene diisocyanate (DIC). Extensively washed sponges were implanted subcutaneously in rats and harvested 5 and 17 days later. Histology showed that at 5 days, the GTA-crosslinked sponge induced more cellular reaction at the outer layer of the sponge than the DIC-tanned sponge. After 17 days, the cellular infiltration of the GTA-tanned sponge remained at the periphery of the implant while the DIC-tanned sponge was completely infiltrated by inflammatory cells, including fibroblasts. Quantitative morphometry and determination of cellular DNA in sponges harvested at 17 days support the morphological finding. We conclude that GTA-tanned sponges are cytotoxic as evidenced by more pronounced tissue reaction soon after tissue implantation, and no cellular infiltration at later stages into the implant. Hexamethylene diisocyanate seems to be a more adequate tanning agent for sponges designed as a tissue substitute.