The Immunosuppressive Agent FK506 Prevents Subperineurial Degeneration and Demyelination on Ultrastructural and Functional Analysis

Several kinds of injury models, such as crush, transection and graft repair have been well studied in terms of neuroprotective effect of FK506. However, definitive experimental studies are lacking on focal degeneration or ischemia. In the present study, our goal was to investigate the effect of FK506 on functional recovery of the sciatic nerve after focal ischemia, produced by stripping of the epineurial vessels. A total number of 48 Wistar rats were used for this purpose and divided into four groups (control, sham-operated, FK506-treated, and Vehicle-treated). Sciatic nerves were approached by femoral and gluteal muscle splitting. Then, epineurial vessels around the sciatic nerve were stripped in the FK506-treated and Vehicle-treated groups. After operation, 5mg/kg/day FK506 administration was initiated by subcutaneous injection until animal sacrifice. The same volume of saline was administrated to the vehicle-treated group. The functional and sensory recoveries were tested by walking pattern analysis and pinch test in every postoperative week. The animals were sacrificed in the end of the fourth postoperative week and sciatic nerve samples were harvested and processed for electron microscopic evaluation. Our data revealed that FK506 administration showed beneficial effect on subperineurial degeneration/demyelinization from functional, sensorial, and ultrastructural points of view. The sciatic nerve samples in the FK506-treated group had several remyelinated fibers compared to the vehicle-treated group. Our literature searches revealed that FK506 administration has not, to our knowledge, been studied in focal ischemic degeneration produced by stripping of the epineurial vessels.