Sip1干预BMP信号活性对少突胶质前体细胞移植治疗脊髓损伤的影响

The demyelination of white matter is one of critical factors to suppress the functional restoration after spinal cord injury.Transplantation of oligodendrocytes precursor cells(OPC) is becoming more highlighted for their advantaged ability to generate myelinating oligodendrocytes. While there exists some factors to inhibit the survival and myelinogenesis of transplanted OPC in the microenvironment of lesion. A lot of reports has demonstrated that the bone morphogenetic proteins (BMP) upregulated dramaticly post-injury were play the key roles on the myelination,our preliminary study indicated that both enhancing and blocking the BMP signaling inhibited the maturation and myelinogenesis of oligodendrocytes, it remind the downstream of the BMP signaling exsits the different target genes which play different functions on oligodendrocyte maturation and injury recovery.The recent reports showed that the smad interacting protein-1 (Sip1) could antagonize BMP signaling to promote the myelination through acting as a transcriptional repressor of Smad activity, and promoting activation of Olig1/Olig2 transcriptional activity.Therefore, the present project is designed to explore the effects of interfering BMP signaling via Sip1 gene modification on the activity of signal and ability to remyelination and rehabitation of injury spinal cord. The expected results will hopeful uncover the overall roles of BMP signaling on the genesis of oligodendrocyte and recovery of spinal cord injury, and then provide new therapeutic methods for OPC transplantation to remedy spinal cord injury.

脊髓损伤后由少突胶质细胞（OL）变性死亡引发的白质病变是影响功能恢复的关键原因之一，OL前体细胞(OPC)移植被认为是治疗新希望，但损伤微环境内存在不利于移植细胞存活和形成髓鞘的因素。研究显示，损伤后显著上调的BMP是影响OL分化成熟的关键分子。我们的前期研究表明，增强和阻断BMP信号均会抑制OL成熟和髓鞘形成，提示BMP信号下游存在功能不同的靶基因，可能对髓鞘形成和损伤修复发挥不同作用。新近研究发现，核转录因子Sip1可通过作用于下游靶基因，逆转BMP信号激活对OL形成的抑制作用。因此，本项目拟用Sip1干预OPC上的BMP信号，观察Sip1基因过表达或缺失对OPC细胞生物学活性及其内BMP信号活性的影响；并进一步在脊髓损伤模型上研究Sip1基因修饰的OPC移植后形成髓鞘和修复损伤的能力。研究结果将揭示BMP信号对OL形成和脊髓损伤修复的作用，为OPC移植治疗脊髓损伤开拓新思路。

脊髓损伤后，对损伤修复起作用的细胞可分为神经元和神经胶质细胞两大方面。近年来，越来越多的研究发现神经胶质细胞对整个脊髓损伤的修复起更加重要的作用。脊髓内的神经胶质细胞主要包括星形胶质细胞、少突胶质细胞和小胶质细胞。目前对脊髓损伤修复的研究也主要集中在干预和影响这三种胶质细胞上。本项目原计划主要着眼于干预少突胶质细胞的命运和功能上，而实际执行过程中，根据出现的问题和存在的困难，同时也考虑到项目的完整性和后期的可持续性研究，调整为对该三种胶质细胞分别进行相应的干预，观察对损伤修复的影响。结果发现：1.急性脊髓损伤后早期，损伤处脊髓内Sip1蛋白表达显著上调，至损伤后14天，已降至接近正常水平。Sip1主要表达于少突胶质细胞内，脊髓其它胶质细胞内也可见部分表达，而神经元内基本无表达。且损伤中心周缘出现部分形态异常增生的少突胶质细胞，这类细胞内Sip1的表达强度明显增加。提示脊髓损伤后Sip1表达的变化可能与少突胶质细胞的命运和脊髓损伤的修复有重要联系，干预其表达可能达到良好的预期效果。2.抑制影响星形胶质细胞活化的重要分子基质金属蛋白酶9（MMP-9）的活化能显著降低损伤脊髓内星形胶质细胞的活化，促进实验动物运动功能的恢复；3.急性脊髓损伤早期，抑制Rho/ROCK通路的关键活化分子，能显著降低损伤脊髓内小胶质细胞的活化，促进实验动物运动功能的恢复。后两项的结果提示在脊髓损伤后可通过降低星形胶质细胞和小胶质细胞的过度激活达到促进脊髓细胞存活功能恢复的效果。该项目的实验结果对后期进行脊髓损伤的联合干预策略提供重要的参考依据。