Nerve regeneration

A nerve regenerates better if it is repaired at a delayed interval after injury (Sunderland 1947). We investigated this "pre-degenerated" phenomenon in the S-D rat. A 1-cm. segment of a pre-degenerated ulnar nerve was used to repair a fresh median nerve gap. The ulnar nerve was previously sectioned at different time intervals. Contractions of the superficial flexor muscles of the forelimb by stimulating the median nerve and histology of the median nerve at the bridging nerve segment were compared. The grafts which were prepared 1-week prior to repair showed the best result. This time dependent phenomenon suggested important mechanisms of nerve regrowth and regeneration which require further investigation.;The temporal changes of morphology of the Schwann cells within the "pre-degenerated" nerve were studied. The number of the Schwann cells the "pre-degenerated" nerve changed with time. The number of Schwann cells increased after nerve transection. And after pre-degenerated for 1-week, the number of Schwann cells have reached a peak which was 3.52 +/- 0.27 x 107 cells/ml. We detected the thickness of myelin and found that the myelin thickness has increased. After pre-degenerated for 1-week, the myelin thickness was thickest at about 2.37 +/- 0.36 nm. The myelin thickness slowly decreased after wards.;We studied the temporal changes of BDNF and CNTF within the pre-degenerated nerve. It was found that changes of BDNF and CNTF had certain roles. The level of BDNF has increased in group 2 that was pre-degenerated for 3 days. The highest level of BDNF (BDNF/GADPH 5.88 +/- 3.03) was expressed in group 3 which was pre-degenerated for 7 days (1 week). After that, the level of BDNF was remained at high level for a long time. The level of CNTF had two peaks. One peak was in group 2 which was pre-degenerated for 3 days. After that, the level of CNTF increased slowly. The second peak was in group 5 that was pre-degenerated for 3 weeks. The level of CNTF has slow down after that time.;5) We found that Schwann cells were very important in peripheral nerve regeneration. The quantity and quality of Schwann cells important for the peripheral nerve regeneration. In this study, Schwann cells of different "pre-degeneration" time were filled into silicone tubes to repair a critical gap in the median nerve (12mm.), and compared to fresh nerve grafting or silicone tube without Schwann cells. It was found that Schwann cells filled tubes had better nerve regeneration and muscle tension recovery compared to other groups. Maybe, we have found a new and better method to repair the peripheral nerve gap.;We described a new technique of controlled enzyme digestion of peripheral nerves to obtain a highly purified suspension of Schwann cells. An average of 1.72 x 107 cells /ml was obtained from a 1-cm segment of ulner nerve in the grown-up SD rat. Comparison with conventional technique and simultaneous culture of adventitial tissues from the same nerve confirmed the lack of contamination by fibrocytes.