Polycaprolactone (PCL) 導管對神經再生的效應

Abstract

我們以組織病理學及神經生理學的方法來評估不同設計的polycaprolactone (PCL) 導管: 空管(hollow) vs.多層管(laminated)何者可達到和自體神經移植 (autologous nerve graft)同樣的效果。 我們以免疫組織化學染色法 (immunohistochemistry)來檢視導管植入後, 空管及多層管中許旺細胞上的抗原變化以及神經再生的情形。 結果,在多層管中,神經生長因子受體(nerve growth factor receptor) p75與神經膠纖維酸性蛋白(glial fibrillary acidic protein) GFAP的表現明顯提升, 同時伴有較少量的磷酸化神經絲蛋白(phosphorylated neurofilamants)表現。 而空管中的結果則是相反。 此結果顯示, 空管的效率比多層管好。 為了評估在導管植入後,長期性的神經再生及功能回復, 近一步的量化評估包括坐骨神經, 朏長肌的神經肌肉接合(neuromuscular junctions)的型態度量化分析(morphometric analysis)以及坐骨神經的神經傳導實驗分別在術後三個月及六個月後實行。 手術後六個月, 空管組的神經纖維密度和自體神經移植組的結果相似, 而多層管組只達到它們的 20%。 同樣的結果也反應在神經纖維直徑及有神經支配神經肌肉接合的百分比上。 以朏長肌纖維截面積(cross-sectional muscle fiber area) 與足底肌的複合動作電位(compound muscle action potentials)的結果而言, 在三組實驗組中, 仍然是空管組具有與自體神經移植組同樣的效率且明顯優於多層管組。 這些結果顯示, PCL空管可取代自體神經移植, 且本實驗也提供了一套多方面的評估系統來檢視導管在神經截斷後促進神經再生的效應。

We established histopathological and neurophysiological approaches to examine whether different designs of polycaprolactone-engineered nerve conduits (hollow versus laminated), could promote nerve regeneration as autologous grafts after transection of sciatic nerves. Changes of various antigen profiles in Schwann cells and regenerated axons within the hollow and the laminated conduits were examined by immunohistochemistry. Nerve growth factor receptor (p75) and glial fibrillary acidic protein (GFAP) were up-regulated in the laminated conduit with fewer expressions of phosphorylated neurofilaments. Different results with down-regulations of p75 and GFAP and abundant expressions of phosphorylated neurofilaments were observed in the hollow conduit and the autologous graft. The findings revealed that the hollow conduit had better regeneration efficacy than the laminated one. For evaluating the long-term axonal regeneration and the functional recovery after conduit grafting, further quantitative assessments included morphometric analysis at the level of sciatic nerve, neuromuscular junction (NMJ) and gastrocnemius muscle, and nerve conduction studies on sciatic nerves were performed at POM 3 and POM 6. Six months after nerve grafting, the nerve fiber density in the hollow-conduit group was similar to that in the autologous-graft group; the laminated-conduit group only achieved ~20% of these values. The consequences of these differences were reflected in nerve growth into muscular targets; this was demonstrated by combined cholinesterase histochemistry for NMJ and immunohistochemistry for nerve fibers innervating NMJ with an axonal marker, protein gene product 9.5. Hollow conduits had similar index of NMJ innervation as autologous grafts; the values were higher than those of laminated conduits. Among the three groups, there were same patterns of differences in the cross-sectional area of muscle fibers and amplitudes of compound muscle action potential. These results indicate that hollow conduits were as efficient as autologous grafts to facilitate nerve regeneration, and provide a multidisciplinary approach to quantitatively evaluate muscular reinnervation after nerve injury.