Thymosin β4 enhances the healing of medial collateral ligament injury in rat.

The role played by thymosin β4 (Tβ4) in the process of wound healing was reported in several organs. However, there have been no reports that investigated the role of Tβ4 in the repair process after ligament injury. The purpose of this study was to determine whether administration of Tβ4 would improve ligament repair following injury. The medial collateral ligament (MCL) was sharply transected on the day of surgery. Then, the treatment group received 100 μL of fibrin sealant containing 1 μg of Tβ4 placed in the ligament gap. Healing tissues were evaluated by hematoxylin and eosin stain, transmission electron microscopy, and biomechanical test at 4 weeks after surgery. Histologically, healing tissues in Tβ4-treated group exhibited uniform and evenly spaced fiber bundles. However, the collagen fibers were not evenly spaced in control rats. Moreover, diameters of collagen fibrils within granulation tissue from the Tβ4-treated rats were significantly increased. In Tβ4-treated MCLs, the mechanical properties of these healing tissues were significantly higher at 4 weeks after surgery. In terms of the mechanical properties of the healing femur-medial collateral ligament-tibia complexes, the Tβ4-treated group had significantly better biomechanical properties than the control group at 4 weeks after surgery. Local administration of Tβ4 promotes the healing process of MCL, both histologically and mechanically, in a rat model. These findings provide a basis for potential clinical use of Tβ4 in repairing ligaments.