复合神经生长因子的纳米纤维导管促神经再生的初步研究

Nerve conduits of nanofibers combined with nerve growth factors

目的探讨应用同轴静电纺丝技术制备复合神经生长因子的神经导管的可行性，检测神经生长因子的活性及对神经再生的作用。方法应用同轴静电纺丝技术制备以可降解生物材料乳酸己内酯共聚物[P（LLA—CL）]为壳层材料、神经生长因子（NGF）和牛血清蛋白（BSA）为芯层材料的纳米纤维，纺织成神经导管复合体。模拟体内环境进行体外降解缓释8周，在不同时间点，应用PCI2细胞培养法检测缓释液中NGF的生物活性。构建大鼠坐骨神经10mm缺损模型，分别采用自体神经移植（A组）、P（LLA—CL）／BSA／NGF导管（B组）、P（LLA—CL）／BSA导管加一次性注射NGF（C组）、P（LIA—CL）／BSA导管（D组）桥接神经断端，术后12周进行再生神经形态学等观察。结果P（LLA—CL）／BSA／NGF导管在体外8周尚未完全降解，能够持续释放NGF，并保持生物活性。解剖观察可见再生神经均通过神经导管，B组再生神经的直径最均匀一致，达到正常神经的直径。透射电镜图片显示，A组和B组神经纤维数目多、大小均匀、成熟良好，C组和D组纤维结缔组织多、神经纤维细小、髓鞘薄。结论P（LLA—CL）／BSA／NGF导管具有良好的组织相容性和生物活性，能够诱导并促进神经再生，提高神经再生的质量，其移植效果接近于自体神经移植。

Objective To evaluate a nerve conduit made from biodegradable core-shell nanofibers encapsuling nerve growth factors （NGF） by coaxial clectrospinning and its bioactive effect on the sciatic nerve regeneration. Methods Firstly, the nerve conduits were developed from the core-shell structured biodegradable nanofibers, with Poly（L-lactide-co-e-caprolactone） [P（LLA-CL）] as a shell and bovine serum albumin （BSA） or BSA/NGF as a core by coaxial electrospinning. The in vivo NGF release was simulated in vitro for 8 weeks. At various time points, the NGF supernatant from the P（LLA-CL）/BSA/NGF conduits was added to serum-free RPMI to culture PC12 cells. According to the differentiation rate of PC12 cells, the bioactivity of released NGF was evaluated. Next, 48 male SD rats were randomly and equally divided into 4 groups. The middle segments （10 mm） of the sciatic nerves of the rats were excised and then repaired with the sciatic nerve autografis （Group A）, with the P（LLA-CL）/BSA/NGF conduits （Group B）, with the P（LLA-CL）/BSA conduits and an injection of NGF （50 ng） into the conduits （Group C）, and with the P（LLA-CL）/BSA conduits （Group D）, respectively. The morphologie parameters of the nerve regeneration were observed and evaluated 12 weeks after operation. Results The released NGF from the P（LLA-CL）/ BSA/NGF conduits retained bioactivity throughout 8 weeks by inducing the differentiation of PC12 cells into neuroeytes. After a partial biodegradation the conduits still remained intact in the outline, and the sciatic nerve regenerated through the conduit cavity. Based on the histological observation, the quantity, uniformity, and maturity or the nerve fiber regeneration in Groups A and B were better than those in Groups C and D. The diameters of the regenerated nerve in Group B were the most uniform and equal to the normal nerve diameter. Conclusions The P（LLA-CL）/BSA/NGF conduits can release NGF continuously and retain its bioactivity for at least 8 weeks. The NGF controlled-release conduits can effectively promote the regeneration and myelinization of rat sciatic nerve, with the morphological indexes similar to those of the nerve autografi.