骨骼肌电刺激通过Erk/Cdk5上调LRP4信号促进周围神经选择性再生和功能恢复

Promoting preferential motor nerve regeneration (PMR) and function recovery are the core issues in regard of periphery nerve repair. The muscle-derived signals play the key role in this process. Our previous study indicated that electrical muscle stimulation enhanced muscle-derived signals, promoted PMR and improved function recovery of the target organs. However, the mechanism involved is elusive. LRP4 expressed in muscle cells, as a bi-directional signaling molecule, combines with Agrin secreted by motor neurons to regulate the growth and differentiation of the pre- and post-synaptic membranes in the neuromuscular junctions through anterograde or retrograde signals. Our previous work has proved that electrical stimulation promoted the expression of LRP4 and this effect was inhibited by Cdk5 inhibitor. The Erk/Cdk5 signals are involved in regulating synaptic plasticity. Therefore, we hypothesize that electrical muscle stimulation upregulates LRP4 through Erk/Cdk5 signal pathway, and LRP4 combines with Agrin to promote selective regeneration and function recovery of periphery nerve. The femoral and sciatic nerve injury model, neuron and muscle cell co-culture system, shRNA and retrograde tracing technology are applied to prove the above hypothesis. This study will provide theoretical basis for the clinical application of electrical muscle stimulation to promote PMR and function recovery.

促进周围神经选择性再生(PMR)和功能恢复是周围神经损伤(PNI)修复再生的核心问题。肌源性信号在PMR中具有至关重要的作用。申请人前期研究显示电刺激能提高肌源性信号，促进PMR，改善靶器官功能。但是其机制尚不清楚。肌细胞上的低密度脂蛋白受体相关蛋白4(LRP4)是一个具有双向信号作用的分子，与运动神经元分泌的Agrin结合后以顺、逆向信号调节神经肌肉突触前后膜生长分化。预实验发现电刺激能上调肌细胞LRP4表达，且此作用可被细胞周期蛋白依赖性激酶5(Cdk5)抑制剂阻断。而Erk /Cdk5信号参与调节突触可塑性。因此我们推测骨骼肌电刺激可能通过Erk/Cdk5信号上调肌细胞LRP4，后者与Agrin结合促进PMR和功能恢复。本研究拟采用股、坐骨神经损伤模型和神经元肌细胞共培养体系，应用shRNA和逆向追踪等技术证明此假说，为临床应用骨骼肌电刺激促进PMR和功能恢复提供理论基础和实验依据。

促进周围神经选择性再生(PMR)和功能恢复是周围神经损伤(PNI)修复再生的核心问题。肌源性信号在PMR中具有至关重要的作用。电刺激能提高肌源性信号，促进PMR，改善靶器官功能。但是其机制尚不清楚。肌细胞上的低密度脂蛋白受体相关蛋白4(LRP4)是一个具有双向信号作用的分子，与运动神经元分泌的Agrin结合后以顺、逆向信号调节神经肌肉突触前后膜生长分化。而且Erk /Cdk5信号参与调节突触可塑性。本研究以Erk /Cdk5信号为切入点，以LRP4为靶点，观察电刺激调节肌细胞内LRP4的信号分子，同时分析探讨神经元肌细胞Agrin/LRP4信号在周围神经选择性再生和功能恢复中的作用。本研究结果显示电刺激可逆转神经损伤后LRP4、AchR、Agrin、GAP43表达减少以及Erk、Cdk5的活性下降；其中神经内Agrin、肌肉内LRP4信号可促进周围神经损伤后选择性再生、提高再生轴突数量、直径以及功能恢复；而且Erk、Cdk5信号调控电刺激诱导LRP4、AchR、Agrin、GAP43表达，且影响神经损伤后神经再生和功能恢复。本项目的研究阐明了促进神经选择性再生和功能恢复的分子基础，为临床电刺激治疗周围神经损伤、促进神经功能恢复提供了理论基础和实验依据。