Therapeutic Strategies for Repairing Optic Nerve Injury

描述（由申请人提供）：这是一项使用新颖的、系统可递送的小抑制肽来确定联合靶向神经元内抑制因子和细胞外抑制因子是否显著改善视神经损伤（ONI）后视网膜神经节细胞（RGC）轴突再生和存活的提案。切断的视轴突不能再生，ONI导致患者终身视力丧失。除了轴突切开术后的RGC凋亡外，内在生长能力的降低和抑制分子环境都是成熟CNS神经元轴突再生失败的原因。使用条件敲除（KO）小鼠的研究表明，肿瘤抑制基因PTEN是一种严重限制成年RGCs再生能力的神经元内在因子。PTEN的缺失增强了ONI后RGC轴突的生长和存活。胶质瘢痕中产生的硫酸软骨素蛋白聚糖（CSPGs）是强烈抑制轴突延伸的外在因素。最近，我们和其他实验室发现LAR和PTP磷酸酶是介导CSPG抑制的受体。它们中的任何一个的缺失部分克服了CSPGs的抑制，刺激了受损中枢神经系统轴突的生长。一些PTPs，包括LAR，也可以激活半胱天冬酶，诱导细胞凋亡。抑制PTEN和CSPG信号对于促进中枢神经系统轴突再生是非常有希望的，但转基因删除PTEN、LAR或PTP -对于治疗患者是不可行的。我们设计了小的模拟肽来阻断这些抑制分子的功能，并证明了它们在体外和体内促进轴突生长的效率。由于CSPG受体似乎通过不同于PTEN信号通路调节神经元功能，我们假设联合抑制PTEN和CSPG信号通路比单独抑制任何一种都能更好地促进RGC轴突的再生和存活。为了验证这个假设，我们将使用

DESCRIPTION (provided by applicant): This is a proposal that uses novel, systemically deliverable, small inhibitory peptides to determine whether combined targeting of neuron-intrinsic and extracellular inhibitory factors markedly improves retinal ganglion cell (RGC) axon regeneration and survival after optic nerve injury (ONI). Severed optic axons fail to regenerate and ONI leads to life-long visual loss in patients. In addition to apoptotic RGC death following axotomy, both a reduced intrinsic growth capacity and an inhibitory molecular environment contribute to failure of mature CNS neurons to regenerate their axons. Studies using conditional knockout (KO) mice suggest that the tumor suppressor gene PTEN is one neuron-intrinsic factor that critically restricts the regenerative capacity of adult RGCs. Deletion of PTEN enhanced RGC axon growth and survival after ONI. Chondroitin sulfate proteoglycans (CSPGs) generated in glial scars are extrinsic factors that strongly suppress axon extension. Recently, we and other labs identified LAR and PTP� phosphatases as receptors that mediate CSPG inhibition. Deletion of either of them partially overcomes suppression by CSPGs and stimulates growth of injured CNS axons. Some PTPs, including LAR, can also activate caspases and induce cell apoptosis. Suppressing PTEN and CSPG signaling is very promising for promoting CNS axon regeneration, but transgenic deletion of PTEN, LAR or PTP� is not feasible for treating patients. We have designed small mimetic peptides to block functions of these inhibitory molecules and demonstrated their efficiency in promoting axon growth in vitro and in vivo. Because CSPG receptors appear to regulate neuronal functions via pathways different from PTEN signaling, we hypothesize that combining inhibition of PTEN and CSPG signaling promotes RGC axon regeneration and survival better than inhibiting either alone. To test this hypothesis, we will use small peptide inhibitors alone and in combinations, validating the peptide efficacy by comparison to results with KO mice available in our lab. We propose to address 3 Specific Aims by determining whether: 1) peptide blockade of PTEN promotes similar RGC axon regeneration and survival as transgenic deletion in KO mice; 2) peptide blockade of two CSPG receptors promotes greater RGC axon regeneration and survival than inhibiting one receptor; and 3) blocking both PTEN and CSPG signaling with peptides promotes greater RGC axon regeneration and survival than targeting either one alone. By simultaneously targeting neuron-intrinsic and environmental inhibitory factors with small blocking peptides, we attempt to promote axon regeneration and to reduce axotomy-induced RGC loss to greater degrees than by targeting either signal individually. Our novel strategy of administering small, systemically deliverable compounds post-injury may facilitate development of practical combinatorial therapy for optic nerve injury.