MHCI、PirB和CD3ζ蛋白对臂丛损伤后脑运动皮层功能重塑影响的实验研究

Clinically, we found by resting-state fMRI test that brachial plexus injuries induced dynamic imaging changes in representations of the brachial plexus of brain cortex, which suggested functional re-organization in that area. Till now, however, no study has been reported of the machnism of the dynamic plasticity in the motor cortex caused by brachial plexus injuries per se. As some studies have showed that MHCI, PirB and CD3 zeta proteins can regulate the plasticity of visual cortex, we hypothesize that during the early stage of brachial plexus injuries,the deafferentation can make representations of the brachial plexus in the brain cortex inhibited, so that the neural excitbility is enhanced of the adjacent non-deafferented cortices; MHCI, PirB and CD3 zeta proteins in these adjacent areas, therefore, are also functionally activated to a higher level for the purpose of preventing "take-over" of surrounding cortices to representations of the brachial plexus. But as compensatory actions of the torso and shoulder increase, new neural network is still gradually established between representations of the brachial plexus and adjacent non-deafferented cortices, so that the expression level of three proteins metioned above returns to baseline. After constructiion of the rat model simulating functional re- organization of the motor cortex of the brachial plexus, qPCR and Western Blot are used to quantify the expression level of the target proteins, and in situ hybridization and immunofluorescence staining are applied to locate the changing areas of the these proteins in brain tissue slices. If molecular and electrical stimulating results were well matched in the rat model, it is reasonable to believe that clinical dynamic imaging changes in cortical representations of the brachial plexus after brachial plexopathy, mean the occurranve of neural plasticity in these areas. This will provide theoretical basis for application of rehabilitation measures to inhibit this "harmful" plasticity.

我们临床上发现，臂丛损伤导致大脑皮层发生动态影像学改变，提示发生了功能重塑，但目前没有臂丛损伤本身所致运动皮层动态重塑机制的报道。鉴于已有研究显示MHCI、PirB、CD3ζ蛋白可调控视觉皮层重塑，因此假设，在臂丛损伤早期，去传入冲动在抑制臂丛皮层代表区和增加其周围兴奋性同时，也使周围皮层上述3个蛋白活性增加，这在一定程度上抑制了周围皮层对臂丛代表区的"侵占"。但随着躯干和肩部等代偿性动作增加，功能活跃的周围皮层与臂丛代表区仍逐渐形成新的神经连接网络，从而使前者区域内上述蛋白回到基线水平。将在皮层重塑的大鼠模型上，用qPCR和Western Blot定量检测上述蛋白的表达量，用原位杂交和免疫荧光染色定位脑组织切片中目标蛋白变化区域所处位置。如果能在分子层面上得到与电刺激相对应的检测结果，就有理由确认临床有影像学改变的臂丛代表区域发生了功能重塑，这将为制定抑制有害重塑的康复措施提供理论依据。

全臂丛根性撕脱伤后，患肢功能无自发恢复可能且治疗效果不佳。近年研究提示患肢功能恢复与受损神经对应的中枢神经系统重塑有关。本研究主要探讨：1，通过切断大脑半球间胼胝体以观察大脑半球间同源皮层相互抑制对大鼠全臂丛根性撕脱伤后前肢运动皮层重塑的影响,2，定位、定量观察主要组织相容性复合物I类 、配对性免疫球蛋白样受体B 和白细胞分化抗原3 ζ在全臂丛根性撕脱伤后运动皮层重塑中的表达规律。结果提示：1，实验组1组和2组的胡须、颈部、后肢的大脑皮层运动代表区显著大于对照组，且运动代表区在伤后3个月较伤后7天显著扩大。分别在术后7天和3个月，实验2组的胡须和后肢运动皮层代表区显著大于实验1组。单纯切断胼胝体对运动皮层代表区面积变化无影响。2，在原臂丛运动皮层代表区内，与对照组相比，实验组的 MHCI、 PirB、CD3ζ 的mRNA和蛋白表达水平在术后7天显著降低；而在术后3个月，实验组的 MHCI、 PirB、CD3ζ 的mRNA和蛋白表达水平较术后7天时显著恢复。这提示：1，切断胼胝体本身不导致大鼠运动障碍及运动皮层显著重塑，但全臂丛根性撕脱伤后切断胼胝体，可加快患肢运动皮层代表区被周围其它运动皮层侵占。对于损伤神经的运动皮层代表区而言，邻近皮层的对侧同源皮层可通过跨胼胝体交互抑制作用，减缓受损神经运动皮层代表区的重塑进程。2，大鼠全臂丛根性撕脱后，大脑臂丛运动皮层代表区内MHCI、PirB和CD3ζ参与了神经重塑。 MHCI、PirB和CD3ζ在相应运动皮层内的表达规律，与直接皮层电刺激所揭示的重塑规律一致，提示MHCI、PirB和CD3ζ参与负性调控全臂丛根性撕脱伤后运动皮层的重塑过程。研究结果进一步阐明了全臂从撕脱伤后大脑皮层重塑的发生机制，为采取调控大脑重塑以促进患肢功能恢复的治疗措施提供理论依据。