Laliberte Alex M, Karadimas Spyridon K, Vidal Pia M, Satkunendrarajah Kajana, Fehlings Michael G
Division of Genetics and Development, Krembil Research Institute, University Health Network, Toronto, ON M5T2S8, Canada.
Brain Commun. 2021 Jan 21;3(1):fcaa234. doi: 10.1093/braincomms/fcaa234. eCollection 2021.
Degenerative cervical myelopathy is a common condition resulting from chronic compression of the spinal cord by degenerating structures of the spine. Degenerative cervical myelopathy present a wide range of outcomes, and the biological factors underlying this variability are poorly understood. Previous studies have found elevated MIR21-5p in the sub-acute and chronic neuroinflammatory environment after spinal cord injury. As chronic spinal cord neuroinflammation is a major feature of degenerative cervical myelopathy, we hypothesized that MIR21-5p may be particularly relevant to disease pathobiology, and could serve as a potential biomarker. A prospective cohort study of 69 human degenerative cervical myelopathy patients (36 male:33 female) between the ages of 30 and 78 years was performed to identify the relationship between MIR21-5p expression, symptom severity and treatment outcomes. Results from this study identified a positive correlation between elevated plasma MIR21-5p expression, initial symptom severity and poor treatment outcomes. Subsequent validation of these relationships using a mouse model of degenerative cervical myelopathy identified a similar elevation of MIR21-5p expression at 6 and 12 weeks after onset, corresponding to moderate to severe neurological deficits. To further determine how MIR21-5p affects cervical myelopathy pathobiology, this mouse model was applied to a knockout mouse line. Deletion of the gene preserved locomotor function on rotarod and forced swim tests, but also resulted in increased nociception based on tail flick, Von Frey filament and electrophysiological testing. Critically, knockout mice also had reduced spinal cord inflammation, demonstrated by the reduction of Iba1+ microglia by ∼50% relative to wild-type controls. experiments using primary microglial cultures confirmed that MIR21-5p expression was greatly increased after exposure to lipopolysaccharide (pro-inflammatory), Il4 (anti-inflammatory) and hypoxia. knockout did not appear to alter the ability of microglia to respond to these stimuli, as expression of key pro- and anti-inflammatory response genes was not significantly altered. However, target prediction algorithms identified the IL6/STAT3 pathway as a potential downstream target of MIR21-5p, and subsequent testing found that expression of components of the IL6 receptor complex, and were significantly higher in knockout microglia. In aggregate, these data show that plays a role in the progression of motor deficits and neuroinflammatory modulation in degenerative cervical myelopathy. Given this role in neuroinflammation, and its association with poor patient outcomes, MIR21-5p represents a potential therapeutic target and a new marker for prognostication.
退行性颈椎脊髓病是一种常见病症，由脊柱退变结构对脊髓的慢性压迫所致。退行性颈椎脊髓病呈现出广泛的结果，而这种变异性背后的生物学因素却知之甚少。先前的研究发现，在脊髓损伤后的亚急性和慢性神经炎症环境中，MIR21 - 5p水平升高。由于慢性脊髓神经炎症是退行性颈椎脊髓病的主要特征，我们推测MIR21 - 5p可能与疾病病理生物学特别相关，并可作为一种潜在的生物标志物。对69例年龄在30至78岁之间的人类退行性颈椎脊髓病患者（36例男性：33例女性）进行了一项前瞻性队列研究，以确定MIR21 - 5p表达、症状严重程度和治疗结果之间的关系。这项研究的结果表明，血浆MIR21 - 5p表达升高、初始症状严重程度与治疗效果不佳之间存在正相关。随后使用退行性颈椎脊髓病小鼠模型对这些关系进行验证，发现在发病后6周和12周时MIR21 - 5p表达有类似升高，对应中度至重度神经功能缺损。为了进一步确定MIR21 - 5p如何影响颈椎脊髓病的病理生物学，将该小鼠模型应用于基因敲除小鼠品系。基因敲除在转棒试验和强迫游泳试验中保留了运动功能，但基于甩尾、von Frey细丝和电生理测试，也导致痛觉过敏增加。至关重要的是，基因敲除小鼠的脊髓炎症也有所减轻，相对于野生型对照，Iba1 +小胶质细胞减少了约50%。使用原代小胶质细胞培养的实验证实，暴露于脂多糖（促炎）、Il4（抗炎）和缺氧后，MIR21 - 5p表达大幅增加。基因敲除似乎并未改变小胶质细胞对这些刺激的反应能力，因为关键的促炎和抗炎反应基因的表达没有显著改变。然而，靶标预测算法确定IL6/STAT3途径是MIR21 - 5p的潜在下游靶标，随后的测试发现，在基因敲除的小胶质细胞中，IL6受体复合物的组成成分、的表达显著更高。总体而言，这些数据表明在退行性颈椎脊髓病的运动功能障碍进展和神经炎症调节中起作用。鉴于其在神经炎症中的作用及其与患者不良预后的关联，MIR21 - 5p代表了一个潜在的治疗靶点和一种新的预后标志物。
