Neuroprotection and immunomodulation by dimethyl fumarate and a heterologous fibrin biopolymer after ventral root avulsion and reimplantation

Abstract Background: Ventral root avulsion (VRA) is an experimental approach in which there is an abrupt separation of the motor roots from the surface of the spinal cord. As a result, most of the axotomized motoneurons degenerate by the second week after injury, and the significant loss of synapses and increased glial reaction triggers a chronic inflammatory state. Pharmacological treatment associated with root reimplantation is thought to overcome the degenerative effects of VRA. Therefore, treatment with dimethyl fumarate (DMF), a drug with neuroprotective and immunomodulatory effects, in combination with a heterologous fibrin sealant/biopolymer (FS), a biological glue, may improve the regenerative response. Methods: Adult female Lewis rats were subjected to VRA of L4-L6 roots followed by reimplantation and daily treatment with DMF for four weeks. Survival times were evaluated 1, 4 or 12 weeks after surgery. Neuronal survival assessed by Nissl staining, glial reactivity (anti-GFAP for astrocytes and anti-Iba-1 for microglia) and synapse preservation (anti-VGLUT1 for glutamatergic inputs and anti-GAD65 for GABAergic inputs) evaluated by immunofluorescence, gene expression (pro- and anti-inflammatory molecules) and motor function recovery were measured. Results: Treatment with DMF at a dose of 15 mg/kg was found to be neuroprotective and immunomodulatory because it preserved motoneurons and synapses and decreased astrogliosis and microglial reactions, as well as downregulated the expression of pro-inflammatory gene transcripts. Conclusion: The pharmacological benefit was further enhanced when associated with root reimplantation with FS, in which animals recovered at least 50% of motor function, showing the efficacy of employing multiple regenerative approaches following spinal cord root injury.

摘要
背景：腹根撕脱（VRA）是一种实验性方法，其特征为运动神经根与脊髓表面的突然分离。因此，在受伤后第二周，大多数轴突损伤的运动神经元发生退化，显著的突触丧失和胶质反应增强引发了慢性炎症状态。与根再植相关的药物治疗被认为可以克服VRA的退化效应。因此，使用二甲基富马酸（DMF），一种具有神经保护和免疫调节作用的药物，与同种异体纤维蛋白粘合剂/生物聚合物（FS），一种生物胶，联合治疗可能改善再生反应。
方法：成年雌性Lewis大鼠接受L4-L6根的VRA处理，随后进行再植，并每日接受DMF治疗四周。在手术后的1、4或12周评估生存时间。通过尼氏染色评估神经元存活，通过免疫荧光评估胶质反应（抗GFAP用于星形胶质细胞和抗Iba-1用于小胶质细胞）和突触保存（抗VGLUT1用于谷氨酸能输入和抗GAD65用于GABA能输入），并通过基因表达（促炎和抗炎分子）以及运动功能恢复来测量。
结果：研究发现，15 mg/kg剂量的DMF治疗具有神经保护和免疫调节作用，因为它保护了运动神经元和突触，减少了星形胶质细胞和小胶质细胞的反应，以及下调了促炎基因转录物的表达。
结论：当与FS根再植相结合时，药物治疗的益处进一步得到增强，动物恢复了至少50%的运动功能，这表明在脊髓根损伤后采用多种再生方法的有效性。