Laboratorio de Neurología Molecular, Hospital Nacional de Parapléjicos, Toledo, Spain.
PLoS One. 2011;6(11):e27000. doi: 10.1371/journal.pone.0027000. Epub 2011 Nov 2.
Spinal cord injury is a major cause of disability that has no clinically accepted treatment. Functional decline following spinal cord injury is caused by mechanical damage, secondary cell death, reactive gliosis and a poor regenerative capacity of damaged axons. Wnt proteins are a family of secreted glycoproteins that play key roles in different developmental processes although little is known of the expression patterns and functions of Wnts in the adult central nervous system in normal or diseased states.
Using qRT-PCR analysis, we demonstrate that mRNA encoding most Wnt ligands and soluble inhibitors are constitutively expressed in the healthy adult spinal cord. Strikingly, contusion spinal cord injury induced a time-dependent increase in Wnt mRNA expression from 6 hours until 28 days post-injury, and a narrow peak in the expression of soluble Wnt inhibitors between 1 and 3 days post-injury. These results are consistent with the increase in the migration shift, from day 1 to 7, of the intracellular Wnt signalling component, Dishevelled-3. Moreover, after an initial decrease by 1 day, we also found an increase in phosphorylation of the Wnt co-receptor, low-density lipoprotein receptor-related protein 6, and an increase in active β-catenin protein, both of which suffer a dramatic change, from a homogeneous expression pattern in the grey matter to a disorganized injury-induced pattern.
Our results suggest a role for Wnts in spinal cord homeostasis and injury. We demonstrate that after injury Wnt signalling is activated via the Wnt/β-catenin and possibly other pathways. These findings provide an important foundation to further address the function of individual Wnt proteins in vivo and the pathophysiology of spinal cord injury.
脊髓损伤是一种导致残疾的主要原因，目前尚无临床认可的治疗方法。脊髓损伤后的功能下降是由机械损伤、继发细胞死亡、反应性神经胶质增生和受损轴突的再生能力差引起的。Wnt 蛋白是一类分泌糖蛋白，它们在不同的发育过程中发挥关键作用，尽管在正常或疾病状态下，Wnt 在成年中枢神经系统中的表达模式和功能知之甚少。
我们通过 qRT-PCR 分析表明，编码大多数 Wnt 配体和可溶性抑制剂的 mRNA 在健康成年脊髓中持续表达。引人注目的是，挫伤性脊髓损伤诱导 Wnt mRNA 表达在损伤后 6 小时至 28 天内呈时间依赖性增加，而可溶性 Wnt 抑制剂的表达在损伤后 1 至 3 天内出现狭窄峰。这些结果与细胞内 Wnt 信号成分 Dishevelled-3 的迁移移位从第 1 天增加到第 7 天一致。此外，我们还发现 Wnt 共受体低密度脂蛋白受体相关蛋白 6 的磷酸化在第 1 天减少后也增加，并且活性 β-连环蛋白蛋白增加，这两种蛋白都发生了剧烈变化，从灰质中的均匀表达模式转变为紊乱的损伤诱导模式。
我们的结果表明 Wnts 在脊髓内稳态和损伤中起作用。我们证明，损伤后 Wnt 信号通过 Wnt/β-连环蛋白和可能的其他途径被激活。这些发现为进一步研究体内单个 Wnt 蛋白的功能和脊髓损伤的病理生理学提供了重要基础。
