Tracheal cartilage regeneration by slow release of basic fibroblast growth factor from a gelatin sponge

Objective We investigated whether implantation of a gelatin sponge, releasing basic fibroblast growth factor slowly (b-FGF) into a tracheal cartilage defect, would induce regeneration of autologous tracheal cartilage. Methods We created a 1-cm defect in the midventral portion of each of 10 consecutive cervical tracheal cartilage rings in 12 experimental dogs. In the control group (n = 4), the resulting defects were left untreated. In the gelatin group (n = 4), empty gelatin sponges were implanted in the defects. In the basic fibroblast growth factor group (n = 4), gelatin sponges incorporating 100 μg of b-FGF solution were implanted in the defects. We killed the 4 dogs in each group at 1, 3, 6, and 12 months after implantation, respectively, and examined the implant sites macro- and microscopically. Results In the control and gelatin groups, no regenerated cartilage was observed in the tracheal cartilage defects, and the width of the gap between the host cartilage stumps had shrunk. In the b-FGF group, regenerated cartilage was observed in all dogs. The proportion of the defect in the host cartilage occupied by regenerated cartilage was 13%, 84%, 75%, and 69% at 1, 3, 6, and 12 months, respectively. The regenerated cartilage was fibrous cartilage covered with perichondrium, which grew from the host perichondrium and showed continuity with the host cartilage stumps. Conclusions Implantation of a gelatin sponge slowly releasing basic fibroblast growth factor induces tracheal cartilage regeneration, which subsequently fills a large proportion of experimentally created tracheal cartilage defects within 12 months after implantation.