PirB在视神经损伤修复中的作用及机制研究

The elevation of neuronal growth inhibitory factor such as Nogo, MAG and OMgp in injury microenvironment is an important reason for the difficulty of optic nerve regeneration. Previous studies showed that these three kinds of inhibitory factor played their role through a common receptor NgR. Our previous study showed that NgR inhibition was not very efficient for optic nerve regeneration, suggesting that there may be other inhibitory signal. Recent studies showed that pirB was another common receptor for the three factors, and modulated the downstream signaling pathway molecules of PirB,such as SHP-1/2 and POSH, could promote neuritis elongation. We hypothesize that PirB may also play an important role in the repair after optic nerve injury. This project will compare the effect on retina ganglion cells growth in vitro and optic nerve regrowth in vivo by inhibiting PirB and NgR respectively, and observe the change of PirB downstream signals such as SHP-1/2 and POSH signals. By doing so, we want to clarify the roles of PirB to inhibit the regeneration of optic nerve and to elucidate its molecular mechanism, in addition, we also want to know whether or not to get a more powerful promotion for the optic nerve regeneration if inhibition of both PirB and NgR at the same time, and the effect of combining with application of neurotrophic factor. Our research will lay the foundation for establishing an efficient and powerful scheme for promoting optic nerve regeneration by regulating PirB and NgR.

微环境中的神经生长抑制因子如Nogo、MAG和OMgp在损伤后的水平升高是视神经再生困难的重要原因。既往研究认为这三种因子主要是通过共同受体NgR 发挥作用。我们前期研究表明：阻抑NgR后视神经再生仍然十分困难，提示可能还存在其它抑制途径。近年研究发现,pirB是这三种因子的另一共同受体，调节PirB 信号通路下游关键分子SHP-1/2和POSH可明显促进神经元突起延伸。我们推测PirB可能在视神经损伤修复中同样发挥着重要作用。本项目拟通过体内和体外试验观察阻抑PirB的促视神经再生效应和下游SHP-1/2、POSH信号的变化，以期确定PirB阻碍视神经再生的作用并阐明其分子机制，并通过观察同时阻抑PirB和NgR及联合应用神经营养因子在视神经再生中的作用，为制定通过调节PirB和NgR以高效地促视神经再生方案奠定基础，研究结果为视神经的再生提供新的治疗策略和理论依据。

中枢神经系统（central nervous system，CNS）损伤后再生十分困难，CNS的修复与再生，一直是医学研究的难点和热点。视神经是特殊的CNS，常作为研究CNS的代表。视神经的损伤修复研究，不仅对视相关疾病意义重大，也对CNS相关疾病有很好的借鉴意义。髓磷脂相关抑制因子（myelin associatedinhibitors，MAI）对CNS再生的抑制，是视神经损伤后再生困难的关键因素之一。配对免疫球蛋白样受体B (paired immunoglobulin-like receptor B，PirB)是三种主要的MAI的共同受体，许多研究发现 PirB在包括视神经在内的CNS中广泛表达，并参与调控神经元发育、生长导向及可塑性等作用。. 我们的研究发现，在体外试验中将原代RGC转染AD shRNA PirB后，对其轴突生长无明显影响。同时我们还发现网膜的Müller细胞也表达PirB，且随着钳夹伤时间的延长而表达增强。体外用AD shRNA PirB干扰原代培养的Müller细胞，Müller细胞的JAK/Stat3通路激活，CNTF表达升高，再将其与损伤的RGC共培养，发现其可以促进共培养的RGC轴突再生，而同时加入SiRNA CNTF干扰，这种促再生作用被抑制。本研究发现了PirB在CNS中独立于MAI的另一个新功能，即调控Müller细胞的PirB可以通过JAK/Stat3信号通路影响CNTF的表达，间接促进损伤后RGC的再生。