Inhibition of Smad3 promotes the healing of rotator cuff injury in a rat model.

To investigate the effect of inhibiting transforming growth factor-β (TGF-β1)/Smad2/3 signaling on rotator cuff (RC) healing. A bilateral supraspinatus tendon detachment-repair model of Sprague-Dawley (SD) rats was utilized. A total of 120 SD rats were randomly assigned to six groups and each group received the subacromial injection of normal saline, empty vectors, or lentiviral vectors containing small interfering RNA against TGF-β1, Smad2, Smad3 at the bone-tendon junction. Biomechanical and histological analyses were performed to evaluate bone-tendon junction healing quality at 8 weeks after repair. Histologically, scar healing was found in all surgical groups. Animals with inhibited Smad3 exhibited better bone-tendon junction structures with higher density, parallel orientation, and collagen fiber continuity than other surgical group animals. Immunohistochemistry revealed that the protein expression level of collagen I in animals with inhibited Smad3 was more prominent compared with all other surgical groups. Biomechanically, Animals with inhibited Smad3 showed better results in the maximum load at 4, 6, and 8 weeks after surgery compared with other surgical groups. Besides, C3H10T1/2 (Smad3-) cells increased TT-D6 cell migration and tendon-associated genes expression (scleraxis, tenascin C, collagen I) in coculture system. We conclude that inhibition of Smad3 promotes RC tendon healing in the rat supraspinatus model.