An examination of the biologic response to injectable, glutaraldehyde cross‐linked collagen implants

Abstract

The biologic response to injectable, glutaraldehyde cross‐linked, fibrillar collagen implants in the rat subcutaneous model was shown to be a function of the concentration of glutaraldehyde used for cross‐linking. The collagen was prepared from bovine hide by pepsin solubilization and reconstituted as a fibrillar suspension of 35 mg collagen/mL. Fibrillar collagen implants cross‐linked with glutaraldehyde concentrations equal to or less than 0.01% exhibited a response characterized by fibroblast invasion, neovascularization and little, if any, evidence of inflammation. Implants cross‐linked with 0.1 and 1.0% glutaraldehyde elicited a foreign body/giant cell reaction and varying degrees of implant erosion. The interaction of human skin fibroblasts with 0.01% glutaraldehyde cross‐linked collagen in vitro was found to be dependent on the culture conditions utilized to evaluate the interaction. When the ratio of cell culture media to collagen was 20:1, cell invasion of the cross‐linked preparations was observed, whereas, when this ratio was reduced to 1:1, such interactions could not be detected. Noncross‐linked preparations were colonized by cells regardless of the experimental conditions used. Studies of implants in both the rat and guinea pig subcutaneous models indicated that glutaraldehyde cross‐linking concentrations as low as 0.0075% provided enhanced wet weight recovery (wet weight persistence) and resistence to biologic degradation (collagen persistence) as compared to noncross‐linked fibrillar collagen preparations. These cross‐linked implants also exhibited a greater degree of fibroblast infiltration and vascularization. Between 30 and 60 days, some degree of calcification developed in both collagen formulations implanted in rats and guinea pigs; however, the reaction occurred with greater frequency and intensity in cross‐linked preparations in guinea pigs. Calcification in the guinea pig was followed by the appearance of focal areas of ossification.