Effects of separate application of three growth factors (TGF-beta1, EGF, and PDGF-BB) on mechanical properties of the in situ frozen–thawed anterior cruciate ligament

Objective. To clarify effects of a separate application of TGF-beta1, EGF, and PDGF-BB on the material properties of the in situ frozen–thawed anterior cruciate ligament. Design. Twenty-eight rabbits were divided into four groups after undergoing the in situ freeze–thaw treatment in the right anterior cruciate ligament. In 3 of the 4 groups, 4 ng TGF-beta1, 20 ng EGF, and 4 μg PDGF-BB was applied to the frozen anterior cruciate ligament, respectively. In the remaining sham treatment group, only fibrin sealant as a vehicle was applied. Each animal was sacrificed at 12 weeks after surgery. Background. If the role of growth factors in ligament healing and remodeling is understood, better therapies can be designed for ligament trauma. Methods. The freeze–thaw treatment was performed three times using the originally developed cryo-probe. The cross-sectional area of the anterior cruciate ligament was measured by the optical non-contact method. After preconditioning, each specimen was stretched to failure. The ligament strain was determined with a video dimension analyzer. Results. The tensile strength and the tangent modulus of the anterior cruciate ligament in the TGF-beta1 group was significantly higher than in the sham group, but significantly lower than in the normal control group. There were no significant differences in the strength and the modulus between the EGF group, the PDGF-BB group, and the sham group. Conclusions. In this model, an application of 4 ng TGF-beta1 significantly inhibited some of the material deterioration that occurs in the in situ frozen–thawed anterior cruciate ligament, while an application of 20 ng EGF or 4 μg PDGF-BB did not significantly affect the deterioration.