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3问题和展望
由于眼部的特殊组织结构，一直作为基因治疗理想的靶器官。眼是一个相对隔离的组织空间，在眼局部应用siRNA可避免其与身体其他部位的直接接触，同时也可相应的减少siRNA的用量。有研究发现[32]，将siRNA注射于玻璃体中很快就在眼组织内扩散开，并且直到注射后5d仍能检测到siRNA的表达，等到siRNA扩散出眼组织之外时，它已经被高度稀释，很难再对其他组织的同一基因发挥效应，这样它对身体其他组织基因的作用微乎其微。相对于系统的应用siRNA来说，眼组织的这种特点使得在眼部应用RNAi治疗可以有效的沉默眼部基因，从而避免对身体其他部位同种基因的“远达效应”，这种缘于siRNA序列特异性和眼组织相对独立性的局部siRNA应用，为研究眼组织局部“基因敲除”提供了便利的途径。尽管RNAi在研究基因功能、基因治疗中表现出相当的优越性，但是仍然有很多问题亟待解决。如RNAi具体的分子机制，如何确定有效RNAi的位点，如何高效导入siRNA，怎样保证导入siRNA的稳定性，如何有效延长RNAi的作用时间，各类表达载体及合成RNA的毒副作用等。然而，RNAi独特的作用机制及其简便的操作流程和对靶基因表达抑制的高效性使其在肿瘤基因治疗方面显示出了广阔的应用前景。相信随着研究的广泛细致深入，越来越多的与肿瘤生长增殖密切相关的高特异性靶基因及能使外源性治疗基因高效表达载体的发现，RNAi技术将可能成为视网膜母细胞瘤基因治疗的一种新手段。
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