携带脐带间充质干细胞并交联BDNF的复合支架在创伤性脑损伤中的神经修复作用

Nerve repair after traumatic brain injury (TBI) remains to be a challenging clinical problem which compels us to explore new ways of treatment to minimize the death of neurons and loss of neurological function after TBI.It is well known that neurons cannot effectively carry out the regeneration and repair after TBI, therefor, the research of cell replacement therapy in TBI has become a rapidly progressing field. Umbilical cord mesenchymal stem cells (ucMSCs) as an exogenous seed cells appear to have many useful properties such as extensive sources, low immunogenicity and ease in obtaining material. However, an effective transfer of hUC-MSCs to the brain lesion area after TBI is still a technical challenge. Therefore chosing a suitable biomaterial scaffold which can effectively transport the cells to the target area may be a key step for the cellular treatment of TBI. In our preliminary studies we found chitosan scaffolds(CS) had a good compatibility with ucMSCs in vitro.On the basis above, we planed to transfect CXC chemokine receptor (CXCR4) into ucMSCs to promote ucMSCs migration in the brain damage area, and then construct a columnar composite CS which adhere the CXCR4-ucMSCs and cross-link brain-derived neurotrophic factor (BDNF) by genipin (GP). For the further study, we assessed the characterization and toxicity of the composite CS, and evaluated the affect of BDNF released from composite CS on the neural stem cells (NSCs) and ucMSCs differentiation.Finally,this study was designed to transplant the composite CS to damaged cortext area after TBI, evaluate the transplanted CXCR4-ucMSCs and endogenous NSCs proliferation, migration and differentiation, and neuron apoptosis in the brain damaged area and hippocampus through neuroimaging, histological examination and behavioral test.The aims of this study were to produce a composite scaffold for ucMSCs using a well-defined chitosan biomaterial blended with BDNF, to provide a new tissue engineering material for the future clinical application to minimize the neurological deficit after TBI.

由于创伤性脑损伤（TBI）后损伤神经元不能有效地进行再生修复，因此TBI后细胞替代治疗修复神经功能缺损是目前TBI的研究热点。脐带间充质干细胞（ucMSCs）作为外源性种子细胞自身具有许多独特之处，同时我们的前期研究发现壳聚糖支架与ucMSCs具有良好相容性。本研究以此为基础拟通过在ucMSCs中转染CXC趋化因子受体（CXCR4）来促进ucMSCs迁徙；构建携带CXCR4-ucMSCs并通过京尼平（GP）交联BDNF的柱状复合壳聚糖支架，观察复合支架表征，评估复合支架对携带细胞的影响，以及支架释放BDNF对神经干细胞（NSCs）、ucMSCs分化的作用；进而将复合支架移植到大鼠TBI皮层缺损区，体内观察支架移植细胞ucMSCs及内源性神经干细胞的增殖、迁徙及分化情况，并通过神经影像、组织学及行为学综合评价复合支架在TBI神经修复中的作用，从而为TBI后细胞替代治疗提供新的组织工程支架。

TBI后通过干细胞替代的组织工程技术促进神经再生修复是当前研究方向。本项目在前期研究基础上，以hUC-MSCs作为移植干细胞，优化干细胞移植方案，探索更具优势的新型带细胞复合支架。.课题研究证实过表达CXCR4可促进支架中移植hUC-MSCs向损伤区周边迁移；TBI后通过交联BDNF的壳聚糖支架（CGB支架）移植hUC-MSCsCXCR4，可促进hUC-MSCsCXCR4向神经元分化，并一定程度上促进TBI后损伤脑皮层的修复。.同时，课题组进一步研究优化hUC-MSCs移植方案，发现hUC-MSCs与Activated astrocytes联合移植可促进hUC-MSCs增殖、提高hUC-MSCs移植效率，并有利于调动内源性神经干细胞参与神经修复。.此外课题组在研究CGB支架的同时，原创性的设计了RADA16-BDNF水凝胶多肽支架，证实该支架具有易于降解、可塑性强、生物免疫源性低、组织细胞相容性好的优点；同时支架降解产物有利于所携带的hUC-MSCs存活及向神经元分化。课题组研究证实携带hUC-MSCs联合Activated astrocytes的RADA16-BDNF多肽水凝胶支架能促进TBI后的中、小型皮层缺损的再生修复并重建神经细胞间联系。.综上所述，本项目对TBI后hUC-MSCs移植设计了新型携带干细胞复合支架，获得了理想的神经再生修复实验结果，相关研究内容国内外未见类似报道，具有明确的原创性，为TBI后干细胞移植实现神经再生修复提供了新的途径。