以外泌体介导的microRNA体内传输机制为基础开发新型的骨肉瘤治疗方式

microRNAs (miRNAs) are endogenous small non-coding RNAs of 22 nucleotides in length. They play an important role in regulation of gene expression, and are considered as a promising drug for cancer and other human diseases. However, current techniques using virus, bacterial or artificial liposome as delivery vehicles for miRNAs have toxicity and side effect on human bodies. It is urgently needed to develop a biocompatible and effective system to overcome the disadvantage of the currently available approaches. The aim of this project is, therefore, to design a novel targeted delivery system for miRNAs. Exosomes are lipid bilayer vesicles naturally secreted by endogenous cells, playing crucial roles in transport of bioactive molecules including miRNAs between cells. Given their intrinsic role as natural transporter of miRNAs, exosomes potentially represent a novel and exciting miRNA carrier for therapeutic purpose. As therapeutic delivery agents, exosomes will potentially be better tolerated by the immune system. Thus, exosomes may be capable of delivering miRNAs to local cellular environment without causing cytotoxicity and immune response. In this project, by expressing targeting protein on the surface of exosomes, filling exosomes with miRNAs and injecting the modified exosomes into the cultured osteosarcoma cells or bloodstream of animal model of osteosarcoma, we will test if our system can deliver miRNAs to osteosarcoma cells and inhibit cell proliferation and tumor growth. Our project will open up new avenues for therapeutic applications of miRNA and exosome in the treatment of osteosarcoma.

microRNA（miRNA）是一类长约22个核苷酸的非编码单链小RNA，被认为是一类能够对抗多种疾病的新型药物。对miRNA进行高效递送，是其成功应用于临床的关键。目前，运输miRNA的载体一般是病毒或脂质体，若载体替换为低毒且高效的新媒介，将大大提高miRNA作为药物治疗疾病的可能。外泌体是由细胞分泌的天然纳米颗粒，对于免疫系统有更好的耐受性。研究表明，外泌体（exosome）能自由穿越细胞膜屏障，并在细胞间传递miRNA。提示外泌体可能是一类新型miRNA递送载体。本研究中，拟利用外泌体作为一种天然的生物相容性材料，使其充当载体的功效，研究外泌体介导的miRNA的传输是否在体外细胞实验上显示抑制骨肉瘤细胞增殖的作用，以及在体内骨肉瘤动物模型上显示抑制骨肉瘤生长的作用。这项研究将为骨肉瘤治疗提供新的思路，为将miRNA作为抗癌药物、将外泌体作为媒介在体内进行给药治疗骨肉瘤提供理论依据。

本项目以骨肉瘤为研究对象，确定了骨肉瘤中EGFR的高表达，并验证了EGFR的高表达会促进骨肉瘤细胞的增殖。为了对其进行治疗，我们设计了一种新的质粒传输系统，以肝脏作为天然的反应器，高效便捷地合成组装siRNA，并且随血液循环运送的身体各处。我们通过该递送系统，设计了沉默EGFR的质粒，并在小鼠上得到了验证。综上，本项目将为骨肉瘤诊断治疗及抗肿瘤药物的研制提供新的思路和手段。