HO-1高表达未成熟树突状细胞来源的外泌体在同种移植中的致耐受作用及其机制研究

Induction of donor-specific immune tolerance is one of the ultimate goals of organ transplantation. So far, it has been proved that the maturation state of dendritic cells (DCs) determines which effect they have in rejections. Heme oxygenase 1 (HO-1) in tolerogenic immature dendritic cells (imDCs) plays a key role. Previous studies show that imDCs with upregulation of HO-1 (HO-1hi-imDCs) exhibit a remarkable negative immunomodulatory effect in allograft transplantation. In further studies, we have come across that HO-1hi-imDCs, when co-cultured with allogenic T cells after separation by Transwell membrane, still could inhibit T cell proliferation, and furthermore we have demonstrated that exosomes derived from HO-1hi-imDCs play a key role in this process. In this study, based on previous work, donor imDCs with high HO-1 expression are induced in vitro and exosomes extracted, and it is intended to study (1) the function of exosomes derived from HO-1hi-imDCs in allogeneic immune reactions, and (2) the mechanism of homograft tolerance induction by exosomes derived from HO-1hi-imDCs, thus to provide a new train of thought for antigen-specific therapy of transplantation immunity.

诱导供者特异性免疫耐受是器官移植的终极目标之一。迄今已证明，在排斥反应中树突状细胞（Dendritic cell，DC）的成熟状态决定了其发挥何种作用，未成熟DC（imDC）具致耐受性，其中血红素加氧酶1（HO-1）作用关键。前期研究表明，上调HO-1高表达的imDC（HO-1hi-imDC）在同种移植中具有显著的免疫负调节作用。在进一步机制研究中，我们偶然发现HO-1hi-imDC与同种T细胞被Transwell膜隔离共培养时依然能抑制T细胞增殖，而后证实HO-1hi-imDC来源的外泌体在这一过程中发挥关键作用。本研究拟在相关前期工作基础上，在体外诱导高表达HO-1的供者imDC并提取外泌体，研究（1）HO-1hi-imDC来源的外泌体在同种异体免疫反应中的功能；（2）HO-1hi-imDC来源的外泌体诱导同种移植耐受的机制，为移植免疫抗原特异性治疗提供新的思路。

未成熟DC（imDC）具有致T细胞免疫耐受的作用，在高表达HO-1后不仅可增强其在体外同种免疫反应中的负调节能力，且在体内也可增强其诱导移植物耐受的作用。研究表明，imDC来源的外泌体(imDC-EXO)在大鼠同种异体肝移植模型中诱导免疫耐受，并获得长期生存。然而imDC-EXO对于小鼠同种异体心脏移植是否有保护作用仍不清楚，因此本项目旨在探讨imDC-EXO及HO-1hi-imDC-EXO对于小鼠异体心脏移植排斥的保护作用及相关机制。体外诱导Balb/c小鼠骨髓来源的imDC，分别用CoPP（HO-1诱导剂）、SnPP（HO-1阻断剂）及LPS处理后获取相应的外泌体。分别在体内体外检测HO-1hi-imDC-EXO诱导免疫耐受的能力及相关机制。我们的研究表明，HO-1hi-imDC来源的外泌体能够上调同种异体imDC高表达HO-1、增强同种异体imDC抵御成熟的能力、抑制同种异体T淋巴细胞增殖、诱导同种异体naïve CD4+ T细胞向Treg细胞分化增殖；将其输注至受者体内后，能够延长移植物存活，降低排斥反应并抑制受者淋巴细胞增殖及激活；imDC和mDC来源的外泌体MicroRNA具有明显差异，且imDC外泌体中T细胞活化相关MicroRNA水平上调。本研究在体外诱导高表达HO-1的供者imDC并提取外泌体，探讨了其诱导同种异体移植耐受的机制，为移植免疫的无细胞疗法提供新的思路。