The blood–brain barrier (BBB) restricts the systemic delivery of messenger RNAs (mRNAs) into diseased neurons. Although leucocyte-derived extracellular vesicles (EVs) can cross the BBB at inflammatory sites, it is difficult to efficiently load long mRNAs into the EVs and to enhance their neuronal uptake. Here we show that the packaging of mRNA into leucocyte-derived EVs and the endocytosis of the EVs by neurons can be enhanced by engineering leucocytes to produce EVs that incorporate retrovirus-like mRNA-packaging capsids. We transfected immortalized and primary bone-marrow-derived leucocytes with DNA or RNA encoding the capsid-forming activity-regulated cytoskeleton-associated (Arc) protein as well as capsid-stabilizing Arc 5’-untranslated-region RNA elements. These engineered EVs inherit endothelial adhesion molecules from donor leukocytes, recruit endogenous enveloping proteins to their surface, cross the BBB, and enter the neurons in neuro-inflammatory sites. Produced from self-derived donor leukocytes, the EVs are immunologically inert, and enhanced the neuronal uptake of the packaged mRNA in a mouse model of low-grade chronic neuro-inflammation.

血脑屏障 (BBB) 限制信使 RNA (mRNA) 向患病神经元的全身递送。尽管白细胞来源的细胞外囊泡（EV）可以在炎症部位穿过血脑屏障，但很难有效地将长mRNA加载到EV中并增强其神经元摄取。在这里，我们表明，通过改造白细胞以产生包含逆转录病毒样 mRNA 包装衣壳的 EV，可以增强 mRNA 包装到白细胞来源的 EV 中以及神经元对 EV 的内吞作用。我们用编码衣壳形成活性调节的细胞骨架相关 (Arc) 蛋白以及衣壳稳定 Arc 5'非翻译区 RNA 元件的 DNA 或 RNA 转染永生化和原代骨髓来源的白细胞。这些工程化的 EV 继承了供体白细胞的内皮粘附分子，将内源性包膜蛋白募集到其表面，穿过血脑屏障，进入神经炎症部位的神经元。EV 由自体供体白细胞产生，具有免疫惰性，可增强低度慢性神经炎症小鼠模型中神经元对包装 mRNA 的摄取。