Department of Orthopaedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, PR China.
Cell Transplant. 2012;21(6):1177-97. doi: 10.3727/096368911X612503. Epub 2012 Jan 10.
Adult central mammalian axons show minimal regeneration after spinal cord injury due to loss of oligodendrocytes, demyelination of surviving axons, absence of growth-promoting molecules, and inhibitors of axonal outgrowth. In the present study, we attempted to address these impediments to regeneration by using a combinatory strategy to enhance cell survival and regeneration after complete spinal cord transection (SCT) in adult rats. The strategy comprised: 1) adult rat brain-derived neural stem/progenitor cells (NSPCs) preseeded on laminin-coated chitosan channels; 2) extramedullary chitosan channels to promote axonal regrowth and reduce the barrier caused by scarring; 3) local delivery of a novel rat soluble Nogo-66 receptor protein [NgR(310)ecto-Fc, referred to as NgR] to block the inhibitory effect of myelin-based inhibitors; and 4) local delivery of basic fibroblast growth factor, epidermal growth factor, and platelet-derived growth factor to enhance survival and promote differentiation of transplanted cells. Compared with our previous studies where brain-derived NSPCs preseeded in extramedullary chitosan channels were implanted in the same SCT model but without growth factors and NgR, the present channel-growth factor combination produced greater numbers of surviving NSPCs after SCT. Also, the growth factors promoted preferential differentiation of NSPCs toward oligodendrocytes, while NgR significantly decreased astrocytic differentiation of NSPCs. NgR alone or in combination with NSPCs significantly enhanced the total number of myelinated fibers in the bridge and increased the area of the bridging tissue between the cord stumps. The combination of NgR, growth factors, and NSPCs had synergistic effect on bridge formation. However, only a small number of descending corticospinal tract axons grew into the central portions of the bridges as shown by anterograde tracing of the corticospinal tract with BDA. The majority of the regenerated axons in the channels originated from local host neurons adjacent to the tissue bridges. In conclusion, we showed that growth factors increased survival of transplanted NSPCs whereas NgR enhanced axonal regeneration, but the combination did not have additive effects on functional recovery or regeneration.
成年哺乳动物中枢轴突在脊髓损伤后再生能力非常有限，这主要是由于少突胶质细胞的丧失、存活轴突的脱髓鞘、缺乏促生长分子以及轴突生长抑制因子所致。在本研究中，我们尝试通过使用组合策略来解决这些再生障碍，以增强成年大鼠完全脊髓横断（SCT）后细胞的存活和再生。该策略包括：1）预先在层粘连蛋白包被的壳聚糖通道上播种成年大鼠脑源性神经干细胞/祖细胞（NSPCs）；2）外髓鞘壳聚糖通道促进轴突再生并减少瘢痕引起的障碍；3）局部给予新型大鼠可溶性 Nogo-66 受体蛋白 [NgR（310）ecto-Fc，简称 NgR] 以阻断髓鞘相关抑制剂的抑制作用；4）局部给予碱性成纤维细胞生长因子、表皮生长因子和血小板衍生生长因子以增强移植细胞的存活和促进分化。与我们之前的研究相比，在相同的 SCT 模型中，将预先播种在髓外壳聚糖通道中的脑源性 NSPCs 植入，但没有生长因子和 NgR，本研究中的通道-生长因子组合在 SCT 后产生了更多数量的存活 NSPCs。此外，生长因子促进 NSPC 向少突胶质细胞的优先分化，而 NgR 则显著降低 NSPC 的星形胶质细胞分化。单独使用 NgR 或与 NSPC 联合使用可显著增加桥接组织中髓鞘纤维的总数，并增加脊髓断端之间桥接组织的面积。NgR、生长因子和 NSPC 联合使用对桥接形成具有协同作用。然而，只有少数下行皮质脊髓束轴突通过 BDA 对皮质脊髓束进行顺行追踪进入桥接的中央部分。通道中的再生轴突大多数源自与组织桥相邻的局部宿主神经元。总之，我们表明生长因子增加了移植 NSPC 的存活，而 NgR 增强了轴突再生，但联合使用对功能恢复或再生没有相加作用。
