RESUMO
Objective: To analyze the effects and mechanisms of three commonly used epidural coverings, gelatin sponge, bovine Achilles tendon extract collagen and polyester urethane fiber, in preventing epidural scar adhesions after laminectomy in rats. Methods: Forty-eight adult Wistar rats were excised from L2 to L5 lamina to establish laminectomy models, and were divided into four groups with random number table according to different covering materials (12 rats in each group): blank group (group A), gelatin sponge group (absorbable, group B), polyester urethane fiber group (non-absorbable, group C) and bovine Achilles tendon extract collagen group (absorbable, group D). At 4 and 12 weeks postoperatively, the spinal tissues of the operated area were taken for gross observation (Rydell scar adhesion rating criteria) and histological observation (Nussbaum criteria); and the expression of three scar proliferation-related cytokines, basic fibroblast growth factor (bFGF), growth transforming factor ß1 (TGF-ß1) and vascular endothelial growth factor (VEGF), were measured in the peridural tissues. The differences between the indices in each group were analyzed and compared. Results: All 48 rats survived, and gross and histological findings at 4 and 12 weeks showed no dural adhesions in the gelatin sponge and bovine Achilles tendon extract collagen groups, adhesions in the polyester urethane fiber group, and heavy adhesions and spinal cord compression in the blank control group. There were significant differences in the Rydell grade and Nussbaum histological score between the absorbable material group and the non-absorbable group (both P<0.05). Western protein blotting at 4 and 12 weeks confirmed that the expression levels of three cytokines, including bFGF, TGF-ß1, and VEGF, were lower in the absorbable material group than those in the non-absorbable group (all P<0.01). Immunofluorescence tests at 12 weeks confirmed that the expression of bFGF, TGF-ß1 and VEGF were all lower in the gelatin sponge group (9.81±0.81, 12.42±2.35, 8.63±1.76) and the bovine Achilles tendon extract collagen group (12.70±2.02, 8.23±1.03, 10.19±2.67) than those in the polyester urethane fiber group (33.94±2.03, 30.29±2.76, 25.79±1.21) (all P<0.01). Conclusions: Bovine achilles tendon extract collagen and gelatin sponge can effectively reduce the hyperplasia of scar and dural adhesions after spinal surgery.