Lufino Michele M P, Edser Pauline A H, Wade-Martins Richard
Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, UK.
Mol Ther. 2008 Sep;16(9):1525-38. doi: 10.1038/mt.2008.156. Epub 2008 Jul 15.
Recent developments in extrachromosomal vector technology have offered new ways of designing safer, physiologically regulated vectors for gene therapy. Extrachromosomal, or episomal, persistence in the nucleus of transduced cells offers a safer alternative to integrating vectors which have become the subject of safety concerns following serious adverse events in recent clinical trials. Extrachromosomal vectors do not cause physical disruption in the host genome, making these vectors safe and suitable tools for several gene therapy targets, including stem cells. Moreover, the high insert capacity of extrachromosomal vectors allows expression of a therapeutic transgene from the context of its genomic DNA sequence, providing an elegant way to express normal splice variants and achieve physiologically regulated levels of expression. Here, we describe past and recent advances in the development of several different extrachromosomal systems, discuss their retention mechanisms, and evaluate their use as expression vectors to deliver and express genomic DNA loci. We also discuss a variety of delivery systems, viral and nonviral, which have been used to deliver episomal vectors to target cells in vitro and in vivo. Finally, we explore the potential for the delivery and expression of extrachromosomal transgenes in stem cells. The long-term persistence of extrachromosomal vectors combined with the potential for stem cell proliferation and differentiation into a wide range of cell types offers an exciting prospect for therapeutic interventions.
染色体外载体技术的最新进展为设计更安全、生理调控的基因治疗载体提供了新方法。转导细胞中染色体外或附加型的核内持续存在为整合型载体提供了一种更安全的替代方案，在近期临床试验中出现严重不良事件后，整合型载体已成为安全问题的焦点。染色体外载体不会对宿主基因组造成物理破坏，使其成为包括干细胞在内的多种基因治疗靶点的安全且合适的工具。此外，染色体外载体的高插入容量允许从其基因组DNA序列的背景下表达治疗性转基因，提供了一种表达正常剪接变体并实现生理调控表达水平的巧妙方法。在此，我们描述了几种不同染色体外系统开发过程中的过去和近期进展，讨论了它们的保留机制，并评估了它们作为表达载体来递送和表达基因组DNA位点的用途。我们还讨论了多种用于在体外和体内将附加型载体递送至靶细胞的递送系统，包括病毒和非病毒递送系统。最后，我们探讨了染色体外转基因在干细胞中递送和表达的潜力。染色体外载体的长期持续存在，再加上干细胞增殖和分化为多种细胞类型的潜力，为治疗干预提供了令人兴奋的前景。
