Complete stress shielding of the Achilles tendon: ultrastructure and level of interleukin-1 and TGF-β.

Abstract

Few studies emphasize the collagen metabolism-related cytokines and ultrastructure of the completely stress-shielded Achilles tendon. In this study, we used a rat model with complete stress shielding of the Achilles tendon to observe the changes in the ultrastructure of the Achilles tendon and concentration of IL-1 and TGF-β 3 weeks after stress shielding. The model group comprised 12 male Sprague-Dawley rats. The stress of the Achilles tendon of the left hind limb was shielded through tendon cerclage combined with sciatic nerve transection, and the right served as a normal control. Three weeks later, the ultrastructure of the Achilles tendon was observed under electron microscopy and IL-1 and TGF-β levels were determined by enzyme-linked immunosorbent assay. Compared with the control side, collagen fibrils of the shielded Achilles tendons were irregularly arranged and loose. The number of small-diameter collagen fibrils increased significantly with the decrease of the average diameter of collagen fibrils. At the same time, IL-1 concentrations increased significantly in the model group as compared to that in the control group, but no significant difference was found in TGF-β levels. These results suggest that IL-1 may play an important role in the change of ultrastructure after stress shielding.