Tetracycline modulates collagen membrane degradation in vitro

Background: Structural integrity of implanted bioabsorbable barrier membran es should be preserved for a sufficient time to ensure expected results. Co llagen membranes are degraded by metalloproteinases (MMP). Their degradatio n rate can be altered either by enhancing structural integrity or by delayi ng the degradation process using MMP inhibitors. Tetracyclines (TTC) presen t inhibitory effects on matrix MMP. Immersing membranes in TTC solution bef ore implantation can delay their degradation. The purpose of the present st udy was to evaluate the effect of collagen membranes immersed in varying TT C concentration solutions on the rate of their degradation in vitro. Methods: Collagen bioabsorbable membranes were prepared as 5 mm diameter me mbrane discs. Membranes were then incubated at 4 degreesC for 24 hours, in either phosphate buffered saline (PBS, Ca2+ and Mg2+ free) or with TTC-HCl dissolved in PBS concentrations of 5 mg/ml, 50 mg/ml or 100 mg/ml. After ri nsing, membranes were incubated with either bacterial collagenase or cultur es of human bone lineage cells. Membrane degradation was studied on days 2, 4, 7, and 14. Two- and 3-way analysis of variance was used to analyze resu lts. Results: Samples supplemented with bacterial collagenase exhibited a statis tically significant interaction between changes of free protein in the medi um, antibiotic concentration used for the immersion, presence of collagenas e in the medium, and incubation time (P <0.0001). Membranes incubated with bone cells exhibited similar degradation trends. Conclusions: Collagen membranes immersed in 50 mg/ml TTC solution exhibited the longest degradation time, both in the clostridial collagenase and the human bone cell lineage assays. Immersion in a 50 mg/ml TTC solution before implantation will delay their degradation.