单分子重编程诱导神经干细胞及其应用

Induced neural stem cells (iNSCs) are not tumor-prone and can be used as cell models to study the pathogenic mechanisms of neural diseases, to screen drugs, and as renewable cell resources for cell replacement therapies. As a result, rapid progress has been made toward generating iNSCs by the technique of somatic cell reprogramming. As both theoretical and technical breakthroughs, we have successfully reprogrammed mouse fibroblasts into mouse iNSCs (miNSCs) using a single non-neural progenitor transcription factor Ptf1a. Compared with past iNSC reprogramming approaches, Ptf1a reprogramming is easier, safer, highly repeatable, and more efficient. Ptf1a-induced miNSCs are more capable of self-renewal, have higher efficiency in directed differentiation, are more similar to endogenous NSCs, and have more advantages when compared with other miNSCs. We hypothesize that Ptf1a would also have these advantages in reprogramming human somatic cells into human iNSCs (hiNSCs). In this project, we plan to elucidate the signaling pathways and molecular mechanisms underlying Ptf1a reprogramming and to evaluate the therapeutic efficacy of transplanted hiNSCs on mouse models of neurodegenerative diseases and physical injury-induced neural system diseases. The proposed project will thus help to facilitate the application of somatic cell-reprogrammed iNSCs in preclinical and clinical studies.

体细胞重编程的诱导神经干细胞（iNSCs）不具有成瘤性，可以作为细胞模型应用于研究神经疾病发病机制以及药物筛选，也可以作为细胞替代治疗的细胞来源，因而成为一项高速发展的技术。我们利用Ptf1a成功地将小鼠成纤维细胞诱导成为miNSCs，在世界上首创了利用非神经前体细胞转录因子重编程体细胞为iNSCs，实现了理论和技术上的双重突破。和过去的方案相比较，单因子Ptf1a重编程方案更安全、更简单、更容易重复、诱导效率更高；而且诱导的miNSCs具有自我更新能力更强、定向分化效率更高、更接近体内组织分离的NSCs等优点。我们假设Ptf1a也能重编程人体细胞为hiNSCs并具有同样的多重优点。因此本项目拟分析Ptf1a重编程过程中内在的信号途径和分子机理，检验hiNSCs移植对于多种退行性及物理损伤导致的神经系统疾病小鼠模型的治疗作用。本课题的实施将有助于推广iNSCs在临床前试验以及临床上的应用。

神经干细胞在体内可以分化为神经元及胶质细胞，可以作为理想的移植细胞来源用于治疗老年性痴呆、帕金森病、舞蹈症、青光眼等神经退行性疾病，以及脊髓损伤等其它原因引起的各种神经系统疾病。 通过研究发现，利用单因子Ptf1a可以将小鼠和人的成纤维细胞在体外高效重编程为神经干细胞。由于Ptf1a是一个非神经前体细胞转录因子，该发现颠覆了体细胞重编程为神经干细胞需要依赖神经前体细胞转录因子参与的认知。经过Ptf1a重编程的神经干细胞在体外可以大量传代扩增，并能在体内外分化成为具有功能的、各种类型的神经元、星型胶质细胞和少突胶质细胞。当把这些诱导神经干细胞移植到患有老年痴呆的小鼠模型大脑中，其可以分化并整合到大脑中，和原有的脑细胞形成功能性连接。行为学测试表明，细胞移植可以明显改善患病小鼠的空间学习及记忆功能。 和早期的其它研究相比，Ptf1a更安全、更高效、得到的神经干细胞和体内的神经干细胞更接近，从而解决了自体神经干细胞的来源问题。重编程的神经干细胞可以用来作为细胞模型研究疾病的发病机理，筛选有效的药物，以及移植治疗各种神经疾病的细胞来源。