Progranulin通过TNFR2介导巨噬细胞自噬促进脊髓损伤修复的作用及机制

Spinal cord injury (SCI) causes disturbances of motor skills and seriously reduces patient’s quality of life. Macrophage-mediated inflammatory response is an important regulatory mechanism of spinal cord injury. Progranulin（PGRN） is a secreted glycoprotein that promotes neuronal survival and axonal growth, but its role and mechanism in acute inflammation and nerve repair of spinal cord injury have not been elucidated. Our previous study found that after spinal cord injury in Grn-/- mice, the recovery of neurological function slowed down, with the increased level of local inflammation and neuron apoptosis. The autophagic flow was blocked in Grn-/- macrophage, which may depend on the activated TNFR2/AMPK pathway. Based on this, we hypothesize that PGRN enhances macrophage autophagy by activating the AMPK pathway via TNFR2, thereby attenuating local inflammation and inhibiting neuronal apoptosis after spinal cord injury. In this study, we will investigate ①the effects of PGRN on macrophage autophagy and neuronal survival after spinal cord injury in vivo and in vitro; ②the mechanism of PGRN promoting macrophage autophagy using knockout mice, bone marrow transplantation and cell co-culture models; ③the correlation between PGRN expression level and patient prognosis in patients with spinal cord injury. This study will explore new mechanisms of inflammation regulation and neuro restoration after spinal cord injury, providing new potential therapeutic targets for clinical treatment of acute spinal cord injury.

巨噬细胞介导的炎症反应是脊髓损伤重要的调控机制。Progranulin（PGRN）是一种分泌型糖蛋白，可促进神经元存活和轴突生长，但其在脊髓损伤急性炎症和神经修复中的作用及机制尚未阐明。我们前期研究发现Grn-/-小鼠脊髓损伤后，神经功能恢复减慢，损伤局部炎症水平和神经细胞凋亡增加；Grn-/-巨噬细胞中自噬流受阻，AMPK通路被抑制，该作用可能依赖TNFR2。据此我们提出假设：PGRN通过TNFR2激活AMPK通路增强巨噬细胞自噬，从而减轻脊髓损伤局部炎症并抑制神经元凋亡。我们拟从体内和体外水平系统研究脊髓损伤后PGRN对巨噬细胞自噬和神经元的保护作用；利用基因敲除小鼠、骨髓移植和细胞共培养模型，明确PGRN通过TNFR2促进巨噬细胞自噬的作用机制；探讨脊髓损伤患者PGRN表达水平与预后的相关性。本研究将探索脊髓损伤后炎症调控和神经修复新机制，为临床治疗急性脊髓损伤提供新的潜在治疗靶点。

Progranulin（PGRN）是一种分泌型糖蛋白，可促进神经元存活和轴突生长，但其在脊髓损伤急性炎症和神经修复中的作用及机制尚未阐明。本研究从体内和体外水平系统研究脊髓损伤后PGRN对MΦ自噬和神经元的保护作用；利用Tnfrsf1a-/-、Tnfrsf1b-/-基因敲除小鼠和细胞共培养模型，明确PGRN通过TNFR2促进MΦ自噬的作用机制；并探讨了脊髓损伤患者PGRN表达水平与疾病的相关性。本研究发现Grn-/-小鼠脊髓损伤后，神经功能恢复减慢，损伤局部炎症水平和神经细胞凋亡增加；Grn-/-MΦ中LC3和p62明显富集，提示自噬流受阻。以rhPGRN水凝胶分别注射治疗脊髓损伤后的WT、Tnfrsf1a-/-、Tnfrsf1b-/-小鼠，观察神经功能恢复情况及自噬、凋亡和炎症指标。我们发现，rhPGRN水凝胶椎管内注射能够明显改善WT小鼠和Tnfrsf1a-/-脊髓损伤后神经恢复情况，BMS评分明显增高，斜栅实验踩空率明显降低，小鼠爬行拖拽距离百分比明显下降，但是在Tnfrsf1b-/-小鼠中，rhPGRN水凝胶注射没有明显改善神经功能恢复情况，说明PGRN可能通过受体Tnfrsf1b促进脊髓损伤修复。自噬标记蛋白检测同样提示PGRN至少部分通过Tnfrsf1b促进MΦ细胞自噬。研究结果表明PGRN通过TNFR2增强MΦ自噬，从而减轻脊髓损伤局部炎症并抑制神经元凋亡。本研究阐述脊髓损伤后炎症调控和神经修复新机制，期待为临床治疗急性脊髓损伤提供新的潜在治疗靶点。