The Study of Nerve Conduction Time and TGF-beta After Sciatic Nerve Injury

ABSTRACT

The peripheral nerves can restore their impaired function after injuries from trauma or surgery. The known factors affecting the recovery of damaged peripheral nerves include the severity of damage, nerve growth factor(NGF) from the damaged area and the concentrations of fibrinogen and thrombin. One of polypeptides, transforming growth factors beta(TGF-beta) has been known to be related to inflammation and healing process of various wound. The TGF-beta has to three subtypes, TGF-beta(1), TGF-beta(2) and TGF-beta(3). This study was performed to explore the effects of TGF-beta subtypes on the recovery phase of damaged nerve. Sciatic nerves of rat were compressed 200 dyne/mm2. The latencies were measured by stimulation of proximal and distal portion of compression injury site and expression of TGF-beta isoforms was studied in proximal and distal nerve of compression site and spinal cord by using avidin-biotin complex immunoperoxidase technique. The latencies were increased at one week after nerve injury and then recovered progressively following 4 weeks. The latencies were restored to almost normal values at 4 weeks after nerve injury. TGF-beta(1) and TGF-beta(3) were expressed weakly at the cytoplasm of Schwann cell in the distal portion after 12 hours of injury. The values of TGF-beta(1) and TGF-beta(3) were increased at 3rd day after injury and lasted till the 4th week which was the end point of nerve regeneration. The changes of proximal portion were different from those of distal portion. TGF-beta(1) and TGF-beta(3) of proximal portion showed stronger positive reaction than that of distal portion and the reaction was peaked at 3rd day after injury. TGF-beta subtypes were rarely present at neuronal cells and astrocytes in spinal cord from 12th hour to 3rd day after injury. The TGF-beta subtypes were weakly appeared at the 1st week after injury and successively increased to 4th week at which the latencies were restored to almost normal value. The patterns of revelation of TGF-beta subtypes showed that TGF-beta(1) was predominant at neuronal cell and TGF-beta(2) was at glial cells. We suggest that TGF-beta subtypes might be related to the regeneration process of nerve injuery.