Adeno-associated virus-2-mediated TGF-β1 microRNA transfection inhibits adhesion formation after digital flexor tendon injury.

Adhesion formation after digital flexor tendon injury greatly affects gliding function of the tendon, which is a major clinical complication after hand surgery. Transforming growth factor beta 1 (TGF-β1) has a critical role in adhesion formation during tendon healing. Persistent regulation of TGF-β1 through application of microRNA (miRNA) specifically inhibiting the function of TGF-β1 (TGF-β1-miRNA) holds promise for treatment of such a complication. Adeno-associated virus (AAV) was used to transfer TGF-β1-miRNA to the chicken digital flexor tendons, which had been injured and surgically repaired. Four doses of AAV2-TGF-β1-miRNA (2 × 10¹¹, 2 × 10¹⁰, 2 × 10⁹ and 2 × 10⁸ vector genomes (vg)) were used to determine the transfection efficiency. At postoperative 3 weeks, we found a positive correlation between the administered AAV2-TGF-β1-miRNA doses and transfection efficiency. The transfection rate ranged from 10% to 77% as the doses increased. Production of TGF-β1 protein in the tendons decreased on increasing vector dosage. When 2 × 10¹¹ and 2 × 10¹⁰) vg were injected into the tendon, gliding excursion of the repaired tendon and work of flexion of chicken toes were significantly increased and adhesion score decreased 6 and 8 weeks later, indicating the improvement of tendon gliding and decreases in adhesion formations. However, the ultimate strength of the tendons transfected at the dose of 2 × 10¹⁰ vg was 12-24% lower than that of the control tendons. The results of this study demonstrate that application of TGF-β1-miRNA had a mixed impact on tendon healing: adhesion around the tendon is reduced but strength of the tendon healing is adversely affected. Future studies should aim at maintaining the beneficial effects of reducing tendon adhesions, while eliminating the adverse effects of decreasing the healing strength.