靶向树突状细胞递送CD40 siRNA抑制移植免疫排斥的纳米药物递送系统的研究

Immune rejection remains the major complication in organ transplantation, the only effective therapy for many patients with end-stage organ failure. The best solution to overcome allograft rejection is to induce immune tolerance. CD40 expressed on dendritic cells (DC) plays an important role in transplant rejection. Anti-CD40 monoclonal antibody can significantly inhibit the function of CD40 on DC, but there are non-negligible side effects. Silencing the expression of CD40 on DC is considered to be a safe and effective strategy for suppressing ransplant rejection. Small interfering RNA (siRNA) has been shown to effectively reduce the expression of CD40 in DC, aid in tolerance induction. Nano drug carriers can enrich siRNA in cells, while free siRNA even cannot cross the cell membrane for RNAi activity because of its anionic property and stiff structure. Nanoparticles used as drug delivery sisytem has a vast application prospect. Self-assembled amphiphilic polymer micelles as drug delivery vehicles have attracted spotlight for they significantly enhanced the activity of gene drugs in cells. In this project, we will develop the biodegradable polymeric micelle drug carriers for targeted delivery siRNA into DC formed by the block copolymer of aliphatic polyester-polyphosphate, based on the results of our previous studies. The polyphosphoester has several advantages, such as the structure is controllable, and it’s easily functionalized and modified. In this project, we will investigate both the in vitro and in vivo effects of polymeric micelle delivered siRNA, and to understand the underlying mechanisms. This project is also expected to provide methodological and theoretical supports for the development of nano drug carriers for suppressing transplant rejection.

器官移植是治疗终末期脏器功能衰竭的唯一有效手段，但始终受免疫排斥反应困扰。最理想的解决方法是诱导受体对供体器官的免疫耐受。树突状细胞（DC）表达的CD40在移植排斥反应中起重要作用。抗CD40的单克隆抗体显示出不可忽视的毒副作用。借助RNA干扰技术有效地降低DC中CD40表达有望成为一种安全、有效地抑制移植免疫排斥的策略。纳米药物载体可在体内促进siRNA在细胞中富集，发挥作用，具有广阔的应用前景。两亲型高分子自组装纳米颗粒作为药物输送载体显著增强药物活性而备受关注。本项目将在已有预研结果基础上，结合聚磷酸酯结构可控、易官能化的特点，发展基于脂肪族聚酯-聚磷酸酯嵌段共聚物的生物可降解高分子纳米载体，靶向DC输送CD40 siRNA。本项目将从体内外不同水平对高分子纳米载体输送siRNA的体内外生物学效应和作用机制进行研究，为发展用于抑制免疫排斥的纳米药物载体提供方法学和理论上的依据及支持。

器官移植是治疗终末期器脏功能衰竭的唯一有效手段。但免疫排斥反应始终困扰着器官移植。最理想的解决方法是诱导受体对供体器官的免疫耐受。。近年来，人们已经认识到树突状细胞（dendritic cells， DC）能够用于诱导免疫耐受，是免疫调节中非常重要的一部分。DC通过共刺激信号通路对机体免疫应答进行调节，其中CD40/CD40L共刺激信号通路在移植排斥反应的致敏和效应阶段都发挥着重要作用，阻断这一通路将能够有效地抑制排斥反应的发生。借助RNA干扰技术有效地降低DC中CD40表达可有效诱导免疫耐受。纳米药物载体可促进siRNA在细胞中的富集，用纳米药物载体输送药物，具有广阔的应用前景。两亲型高分子自组装纳米胶束作为药物的输送载体显著增强药物的活性而备受关注，本项目发展基于两亲性生物可降解高分子的纳米胶束药物载体，靶向输送siRNA到DC中，调节DC功能，诱导免疫耐受。. 本项目我们已经成功发展了一种生物可降解纳米高分子(mPEG-PLGA)，通过双乳化法可制备高效包载siRNA的纳米载体，并证明了其在体外与体内环境中能够高效递送siRNA到DC细胞中，调节其功能。我们以抗原提呈细胞活化杀伤性T淋巴细胞过程中发挥关键作用的共刺激信号分子CD40作为靶点，利用CD40 siRNA成功降低DC细胞中的CD40表达。体外和体内实验证明了携载CD40 siRNA的纳米载体能够显著抑制DC细胞的活化与分化。此外，我们还发现该纳米载体同样对抗原提呈细胞中的巨噬细胞也有显著的活化和分化抑制效果。利用小鼠同种异基因皮肤移植模型和小鼠同种异基因造血干细胞移植模型证明了该纳米载体显著抑制移植免疫排斥反应，从分子、细胞和活体动物水平阐明其抑制移植免疫排斥反应的作用机制。. 我们所制备的PLGA/siCD40在小鼠模型中实现了显著抑制移植免疫排斥的目的，具有一定的临床转化前景，也为发展用于抑制免疫排斥的纳米药物载体提供方法学和理论上的依据及支持。