Chimeric proteins for the treatment of spinal cord injury

描述（由申请人提供）：脊髓损伤（SCI）对中枢神经系统的细胞和组织造成创伤，并导致个体严重和衰弱的状况。脊髓损伤后，受损神经元的有限再生导致永久性残疾，其特征是部分感觉丧失、瘫痪和自主神经功能障碍。神经元无法再生的一个原因是它们无法穿越脊髓损伤后形成的神经胶质疤痕。胶质瘢痕含有细胞外基质分子，包括硫酸软骨素蛋白聚糖（CSPGs）。体外研究表明，神经元无法在CSPG包被表面上扩展过程，而体内数据将再生失败与CSPG表达区域相关联。软骨素酶ABCI是一种细菌酶，催化硫酸软骨素碳水化合物链的降解，如在CSPG上发现的那些。研究发现，软骨素酶治疗可以改善啮齿类动物背柱/皮质-脊髓通路手术损伤后的功能结果。此外，还发现软骨素酶可以恢复啮齿动物视觉皮层的一段可塑性。我们最近已经证明，软骨素酶ABC I治疗可以改善挫伤性脊髓损伤模型的空地运动功能和自主神经功能。尽管在动物模型中的效果是显著的，但脊髓损伤后神经功能的临床相关改善可能需要联合治疗。例如，软骨素酶治疗可与NOGO抑制剂（如诱饵NOGO受体（NgR））联合使用，以促进再生。这项拨款提案的目标是在遗传水平上将软骨素酶与NgR结合起来，创造一种双功能治疗蛋白（Chase-NgR）。除了提供单一药物的联合治疗外，NgR对髓磷脂相关抑制剂的亲和力将赋予Chase-NgR的靶向机制，其中软骨素酶治疗主要集中在中枢神经系统中富含抑制剂的区域。此外，我们已经表明，软骨素酶促进扩散到CMS可能是通过创建扩散途径，通过消化CSPG。因此，Chase-NgR的软骨素酶段可能促进NgR向中枢神经系统实质的扩散，其程度远高于没有CSPG消化的情况。这些研究将为第二阶段拨款提供依据，以资助Chase-NgR作为脊髓损伤治疗的进一步开发。

DESCRIPTION (provided by applicant): Spinal cord injury (SCI) inflicts trauma to the cells and tissues of the central nervous system and causes a severe and debilitating condition in the individual. Following SCI, limited regeneration of injured neurons results in permanent disability characterized by some loss of sensation, paralysis and autonomic dysfunction. One reason that neurons fail to regenerate is their inability to traverse the glial scar that develops following SCI. This glial scar contains extracellular matrix molecules including chondroitin sulfate proteoglycans (CSPGs). In vitro studies show that neurons fail to extend processes over CSPG coated surfaces, while in vivo data correlate failure of regeneration with areas of CSPG expression. Chondroitinase ABCI is a bacterial enzyme that catalyzes the degradation of chondroitin sulfate carbohydrate chains such as those found on CSPG. Chondroitinase treatment was found to improve functional outcome following surgical lesion of the dorsal column / cortico-spinal pathways in rodents. In addition, Chondroitinase was found to restore a period of plasticity in the visual cortex of rodents. We have recently demonstrated that Chondroitinase ABC I treatment improves open-field locomotor function and autonomic function in a contusion SCI model. Although the effects in animal models are significant, clinically relevant improvements in neurological function following SCI may require combinatorial therapies. For example, Chondroitinase treatment may be combined with an inhibitor of NOGO such as the decoy NOGO receptor (NgR) to promote regeneration. The objective of this grant proposal is to combine Chondroitinase with NgR at the genetic level to create a bi-functional therapeutic protein (Chase-NgR). In addition to providing combinatorial therapy with a single drug the affinity of the NgR for myelin associated inhibitors would confer a targeting mechanism to Chase-NgR wherein Chondroitinase treatment is focused on inhibitor rich regions in the CNS. In addition, we have shown that Chondroitinase facilitates diffusion into the CMS presumably by creating pathways for diffusion via digestion of CSPG. Therefore, Chondroitinase segment of Chase-NgR may promote diffusion of the NgR into the parenchyma of the CNS to a much greater extent than can be achieved without CSPG digestion. These studies will provide justification for a Phase II grant to fund further development of Chase-NgR as a therapeutic for SCI.