血管化树枝肽组织工程模块促进损伤脊髓再生研究

The three primary difficulties were the limited access to the tissue engineering approaches to spinal cord injury (SCI) treatment. 1 The functional microcirculatory impairment and unsuccessful anastomosis with host vasculature in SCI, 2 The disruption of spinal cord matrices,3 the devoid of functional neural cells and neurotrophic factor secretion. The branched peptide amphiphile containing cyclic RGD and IKVAV motif synthesized was self-assembled into nanoscale hydrogel. BMSCs modified genetically with VEGF and Ang-1 and NT-3 were located within hydrogel and formed into hierarchically tissue-engineered vascular constructs. These vascularized constructs with sustained overexpression of VEGF and Ang-1and NT-3 implanted into the location in SCI could develop vascular networks, blood-spinal cord barrier (BSCB) integrity and anastomosize to the host vasculatures, which was able to transport enough nutrients and metabolic waste for local cells.BMSCs induced with IKVAV and NT-3 could be transdifferentiated into neural cells, which promoted repair after SCI. This design was not reported, which opened up new paths for spinal-cord injury therapy.

组织工程技术运用于脊髓损伤治疗，面临三个问题：1脊髓损伤局部缺乏有效微循环、与宿主微循环融合困难；2 脊髓基质支架崩解；3 神经细胞及营养因子不足。本课题合成含有环RGD及IKVAV树枝肽,自组装为纳米级凝胶,将VEGF及Ang-1及NT-3基因转染髓基质干细胞（BMSCs）,转染后细胞运送到自组装凝胶内部,构建有序血管化组织工程模块。模块移植到损伤局部，持续高效表达VEGF、Ang-1及NT-3,形成新生血管网、完整血脊髓屏障，与宿主建立有效微循环，为损伤局部细胞提供营养及排泄废物,细胞在IKVAV及NT-3诱导下转分化为神经细胞，促进损伤脊髓修复。此设计未见报道,为脊髓损伤治疗开辟了崭新途径。

向神经元分化的种子细胞，营养因子和支架材料是脊髓损伤后再生需要三个基本条件。首先我们设计的多肽同时带有 RGD 和 IKVAV 两个功能位点的两亲性多肽，能够增加种子细胞的粘附并促进其向神经元样细胞分化。第二：我们利用腺病毒携带 NT-3和vegf 基因修饰骨髓间质干细胞，促进分泌神经营养因子，吸引神经干细胞项损伤区迁移。第三利用种子细胞分泌营养因子有效改善损伤微环境，利用支架为损伤细胞提供空间，从而减少损伤区神经元的凋亡。VEGF 通过与 Flk1 结合，促进骨髓间充质细.胞（BMSCs）向内皮细胞（ECs）分化及内皮细胞浸润，诱导血管再生。第四：利用小分子多肽能够有效形成凝胶，将种子细胞均匀分布在胶中。 即：种子细胞在 NT-3、vegf、 RGD 及 IKVAV 协同作用下于三维凝胶内部分化为功能性神经元，或吸引神经前体细胞到达损伤区，改善损伤微环境，从而促进或改善神经网络形成，促进功能恢复,为促进脊髓损伤修复探索新的治疗方法。