Objectives: To verify the effects and mechanisms of natural MSC-exosome in treating acute GVHD in mice, explore and establish a method for targeted modification of MSC-exosome, and verify the functions of the modified MSC-exosome. Methods: In different doses of MSC-exosome groups and MSC group, weight loss in acute GVHD mice was observed; then the proliferation levels of activated T cells were measured through T cell activation experiment in vitro and OVA antigen-specific T cell activation experiment in vivo. AAV2YF3 mutants carrying PD-L1 and PD-L1-ITGB1 were obtained after the construction of recombinant expression vectors and were then applied to infect human MSC to modify their exosome. The immunoregulatory functions of the modified MSC-exosome were measured with the abovementioned methods. Results: ①Mouse MSC-exosome (300 μg×3 times) and MSC (1×10(6)×3 times) effectively alleviated the weight loss in acute GVHD mice. ②Compared with IL-2, 10, 25 and 50 μg human MSC-exosome inhibited the proliferation of activated T cells in vitro, respectively, 86.0% (IL-2) , 40.0%, 39.6%, and 42.8%; compared with PBS, 50, 100 and 200 μg mouse MSC-exosome inhibited the proliferation of antigen-specific activated OT-1 cells in vivo, respectively, 42.6%, 33.1%, 14.2%, and 10.6%. ③After the infection of AAV2YF3 mutant carrying PD-L1 or PD-L1-ITGB1, the positive proportion of MSC-exosome exceeds 40% and 60%, respectively. ④Compared with the natural state, MSC-exosome modified by PD-L1 or PD-L1-ITGB1 showed better proliferation inhibitory effect in vivo and increased the proportion of Treg cells in vitro. Conclusions: MSC-exosome exhibited similar immunomodulatory effects with MSC. MSC-exosome after PD-L1 and PD-L1-ITGB1-targeted modification effectively inhibited the proliferation of activated T cells and increased the proportion of Treg cells.
目的： 验证天然状态间充质干细胞来源的外泌体（MSC-exosome）治疗小鼠急性移植物抗宿主病（GVHD）的效果和可能机制，探索并建立定向基因修饰MSC-exosome的方法并验证修饰后MSC-exosome的功能。 方法： 构建小鼠急性GVHD模型，观察比较不同剂量MSC-exosome组和MSC组的生理指标评分、生存和体重减低程度；进而通过体外T细胞活化实验和体内OVA抗原特异性T细胞活化实验检测比较组间活化T细胞的增殖水平。构建重组表达载体，获得携带PD-L1和PD-L1-ITGB1的AAV2YF3突变体，进而感染人MSC，分离获得其外泌体。检测比较天然状态和修饰后MSC-exosome在体外和体内对活化T细胞的增殖水平和调节性T细胞（Treg）比例的影响。 结果： ①MSC-exosome（300 μg×3次）和小鼠MSC（1×10(6)×3次）均能够有效改善急性GVHD小鼠的生理指标评分、生存和体重减低程度。②相比IL-2对照组，10、25、50 μg人MSC-exosome和1×10(6)人MSC体外共孵育处理均能够抑制活化T细胞的增殖，增殖比例分别为86.0%（IL-2）、40.0%、39.6%、42.8%和41.0%；相比PBS对照组，50、100、200 μg小鼠MSC-exosome和1×10(6)小鼠MSC在体内均能够抑制抗原特异性活化的OT-1细胞的增殖，增殖比例分别为42.6%、33.1%、14.2%、10.6%和14.6%。③携带PD-L1和PD-L1-ITGB1的AAV2YF3突变体定向修饰人MSC-exosome的表达率分别超过40%和60%。④相比天然状态，PD-L1和PD-L1-ITGB1定向修饰后MSC-exosome在体内对抗原特异性活化的OT-1细胞具有更好的增殖抑制效果；在体外亦能明显抑制活化T细胞的增殖，并诱导提高Treg的比例。 结论： MSC-exosome具有与MSC相似的免疫调节作用。经过PD-L1和PD-L1-ITGB1修饰后的MSC-exosome能够有效抑制活化T细胞的增殖，并且能够诱导提高Treg的比例。.
Keywords: Adeno-associated virus; Exosome; Genetic modification; Graft-versus-host disease; Mesenchymal stem cells.