神經接合術於大鼠臂神經叢損傷修補之研究

Abstract

臂神經叢損傷為常見的上肢神經傷害，臨床上多利用神經轉移手術助其恢復功能。本研究以大鼠尺神經為捐贈者，肌皮神經為接受者，探討end-to-end neurorrhaphy (EEN) 和end-to-side neurorrhaphy (ESN)兩種臂神經叢修復術的效果。EEN組的捐贈神經以截斷的方式與肌皮神經點對點接合；ESN組之捐贈神經則於神經外膜切口，以利肌皮神經吻合。 實驗結果顯示EEN手術3-4個月後，再生的軸突直徑變粗並恢復至正常大小、神經再支配運動終板的密度恢復至正常值；而ESN手術後6個月，再生軸突仍較正常組細，神經再支配運動終板的比例仍低。另一方面，電生理檢查顯示EEN手術3個月後，刺激修復位置上方的神經時，大鼠的二頭肌複合肌肉動作電位振幅高、傳導潛期 (delay) 短；而ESN術後6個月的大鼠的複合肌肉動作電位振幅則仍無法恢復至正常值。行為測試上，EEN手術後3個月及ESN術後6個月，大白鼠之梳洗行為測試 (grooming test)結果皆恢復正常，但EEN組動物功能復原較快。 然而臨床上最重要大的關鍵在於受傷後再生神經纖維需要長的距離、導引與支持神經纖維生長的環境。因此我們接著探討外加促進神經再生的藥物如甲基鈷胺 (methylcobalamin)、類固醇藥(methylprednisolone) 及血管生長因子(pleiotrophin)等是否能增進恢復的速度，我們以既有的系統，亦即同樣以尺神經-肌皮神經EEN的接合模式來加以探討。評估外加PBS, methylcobalamin、methylprednisolone, pleiotrophin以及同時外加methylcobalamin與pleiotrophin等五種方式加以評估。結果顯示這三種藥物皆不影響術後運動神經元中表現與生長相關的蛋白GAP-43之情形。觀察EEN接合手術後一個月的動物，顯示外加methylprednisolone抑制了受傷運動神經元細胞體周圍神經膠細胞活化的反應 (perineuronal glial reaction) 與軸突旁巨噬細胞增生等發炎反應，但伴有暫時性壓抑神經再生的狀況。而外加pleiotrophin則如預期的增加血管的密度與再生神經的數量。methylcobalamin促使再生神經纖維的直徑及髓鞘明顯增厚、史旺氏細胞增生，複合肌肉動作電位振幅大幅上升；methylcobalamin與pleiotrophin併用組也有相同的結果。這個結果顯示methylcobalamin能有效的加速受傷神經在EEN接合後的恢復：一個月後就能恢復到與PBS組三個月的情形相當。綜合這些結果，methylcobalamin促進EEN神經接合術後的神經再生的效用最為明顯。本研究的結果顯示，EEN術後，可以考慮給予methylcobalamin來促進修復的周邊神經的復原。

Injury to peripheral nerves often resorts to nerve transfer for restoring function. Here we evaluated the efficacy of end-to-end (EEN) and end-to-side neurorrhaphy (ESN) of rat musculocutaneous nerve, the recipient, to ulnar nerve, the donor. The donor was transected for EEN and exposed an epineurial window for ESN of the recipient. In EEN, regenerating axons started thick and regained control diameters in 3–4 months while ESN induced slow sprouting of mostly thin collaterals that barely approached control diameters by 6 months. Motor end plates regained control density 4 months following EEN but remained low by 6 months after ESN. The short-latency compound muscle action potential typical of control was quickly restored at 3 months following nerve reconnection. On the other hand, the responses of the ESN started with low amplitude and variable latencies and failed to regain control sizes even by 6 months after surgery Grooming test scores, nevertheless, recovered successfully in both the 3 month-EEN and the 6 month-ESN groups. In short, both neurorrhaphies resulted in functional recovery but EEN appeared quicker and better at the expense of donor function. Since the distance that the regenerating axons have to travel remains as the key determinant, we then explored whether regeneration/myelination-enhancing agent- methylcobalamin, anti-inflammatory drug- methylprednisolone, and neurite growth-enhancing and angiogenic factor- pleiotrophin accelerated the recovery following neurorrhaphy. We explored the administration of PBS, methylcobalamin, methylprednisolone and pleiotrophin alone and combined administration methylcobalamin and pleiotrophin on the same rat ulno-musculocutaneous nerve EEN model that we described above. None of the three drugs applied affected the expression of the neurite-growth associated protein GAP-43 demonstrating that they did not interfere with the regenerating attempt of the injured cell bodies. As expected, methylprednisolone suppressed the perineuronal microglial reaction, periaxonal ED-1 expression and resulted in transiently suppression of the enumeration of regenerated axons and pleiotrophin increased the blood vessel density and nerve fiber densities in the reconnected nerve. Interestingly, methylcobalamin was found to enhance the recovery of compound muscle action potentials and augmented the diameters and myelin thicknesses of the regenerated axons and enhance the expression of S100(+) in Schwann cells 1 month following EEN. Simultaneous methylcobalamin and pleiotrophin treatment resulted in quick and persistent supernumerary reinnervation but failed to enhance the recovery over that of the former alone. In conclusion, methylcobalamin may be preferred over methylprednisolone to facilitate the recovery of peripheral nerves following end-to-end neurorrhaphy.