定向纤维水凝胶递送多信号协同调控脊髓神经再生修复的研究

由于体内神经组织的高度分化以及在损伤后产生的抑制微环境使得脊髓组织的再生修复极其困难，而组织工程与再生医学方法为神经损伤修复带来新的希望。特别是，设计生物材料递送重要的物理、化学、生物学等调控信号，激活组织再生潜能，已成为组织再生修复的一个重要课题。本项目采用静电纺丝技术和分子自组装制备活性多肽改性的多级定向纤维蛋白/壳聚糖复合水凝胶，发挥“取向结构、低弹性模量、生物活性”三种材料信号的协同增效作用，诱导脊髓神经组织再生及功能重建，并阐释在材料诱导神经组织再生过程中的机制问题。采用血管内皮生长因子VEGF模拟多肽KLT和脑源性生长因子BDNF模拟多肽RGI功能化修饰水凝胶，发挥促血管和促神经的协同作用。构建大鼠和比格犬脊髓损伤模型，通过组织学、行为学、电生理、单细胞技术、高清核磁影像技术对材料促进脊髓修复作用进行评价，实现微观再生过程、组织学修复过程、影像学评价结果的相互印证。

The therapy of spinal cord injury (SCI) is still a worldwide clinical challenge because of the limited regeneration capacity of highly differentiated nerve tissue and an inhibitory microenvironment formed in the lesion area. Among the current repair strategy, tissue engineering and regenerative medicine has attracted more and more attentions. Especially, biomaterial-based strategies for nerve regeneration have attracted extensive attentions in recent years. The development of novel biomaterials that deliver physical, chemical, and biological regulatory signals to direct for nerve regeneration is the focus of current intensive research efforts. In this study, a hierarchically aligned fibrin/chitosan nanofiber hydrogel that was fabricated through electrospinning and the concurrent molecular self-assembly process mimics both the soft and oriented features of nerve tissue, thus providing hybrid biophysical cues to instruct cell behavior in vitro and in vivo. At the same time, bioactive peptides including vascular endothelial growth factor (VEGF)-mimetic peptide KLT and brain derived neurotrophic factor (BDNF)-mimetic peptide RGI were used to functionalize chitosan, exerting synergistic effects of angiogenesis and neurogenesis. Rat and canine spinal cord injury models were set up to evaluation the effect of the composite hydrogel on inducing nerve regeneration in vivo. Histological, motor functional, electrophysiological assessments were conducted. Besides, single-cell analysis and diffusion tensor imaging (DTI) of MRI are applied to investigate the regeneration processes and underlying mechanism.