Timing of administration of transforming growth factor-beta and epidermal growth factor influences the effect on material properties of the in situ frozen-thawed anterior cruciate ligament

One of the future goals in ligament reconstruction is to prevent graft deterioration after transplantation. The aim of this study is to clarify whether an administration of TGF-beta1 and EGF significantly affect biomechanical properties of the in situ frozen-thawed anterior cruciate ligament (ACL), an ACL autograft model, and to elucidate whether the timing of this administration may influence its effect. Rabbits were randomly divided into 4 groups after the freeze-thaw treatment with liquid nitrogen was applied to the right knee. In 2 groups, 4-ng TGF-beta1 and 100-ng EGF mixed with 0.2-ml fibrin sealant were applied around the ACL at 3 and 6 weeks after the treatment, respectively. In the remaining two groups, only 0.2-ml fibrin sealant was applied around the ACL at 3 and 6 weeks, respectively. In each group, all animals were sacrificed at 12 weeks after the freeze-thaw treatment. These growth factors applied at 3 weeks significantly inhibited not only the increase of water content and the cross-sectional area of the ACL but also reduction of the tensile strength and the tangent modulus of the ACL (p<0.0001), which were induced by the freeze-thaw treatment. However, the application at 6 weeks did not significantly affect the changes of these parameters after the treatment. This study demonstrated that the timing of administration of TGF-beta and EGF after the freeze-thaw treatment significantly influences its effect on the biomechanical properties of the frozen-thawed ACL.