CHBP诱导的MDSC极化在器官移植免疫耐受中的作用及机制

Myeloid-derived suppressor cells (MDSCs) play an important role in anti-graft rejection and immune tolerance induction. EPOR is a target receptor of cyclic helix B peptide (CHBP) that is expressed on the surface of MDSCs. We attempted to co-culture pre-sensitized MDSCs with CHBP in vitro. The MDSCs were then injected into mice that underwent skin transplantation, results revealing that CHBP is capable of altering the polarity of MDSCs, regulating the differentiation of MDSCs into M-MDSCs, enhancing immunosuppressive function, and improving graft survival. Runx1 is an essential target for regulation of MDSC differentiation. The accumulation of 5-oxo-ETE, a product of MDSCs, is closely related to change of cell polarity. Thus, whether CHBP contributes to the accumulation of intracellular metabolites by influencing the Runx1 signaling pathway, further promoting MDSC differentiation into M-MDSCs and leading to immunoinhibition or tolerance through regulation of Tregs remains to be studied. In this project, mouse skin transplantation model and in vitro experiments were used to elucidate the molecular mechanism of CHBP in influencing intracellular metabolism-mediated cell polarization and inducing immune tolerance of MDSCs through the Runx1 signaling pathway. Such findings may provide theoretical basis for clinical cell therapy and organ transplantation.

髓系来源的抑制细胞（MDSCs）在抗移植物排斥和诱导免疫耐受中发挥重要作用。MDSCs表面存在EPOR受体，是本项目组具有自主知识产权的环肽CHBP的作用靶点，因此我们将CHBP与同种异体皮肤移植预致敏的受体小鼠MDSCs共培养并过继回输体内发现CHBP改变MDSCs极性并调控其向M-MDSCs分化、增强免疫抑制功能，提高移植物存活率。MDSCs代谢产物5-oxo-ETE累积与细胞极性变化密切相关，且Runx1是调控MDSCs分化的重要靶点。因此，CHBP可能通过影响Runx1信号通路调控MDSCs的免疫代谢，进而促进MDSCs向M-MDSCs分化，并诱导Treg形成免疫抑制或免疫耐受状态。本项目拟利用小鼠皮肤移植模型及体外实验，阐明CHBP通过Runx1信号通路改变MDSCs免疫代谢介导的细胞极化，从而诱导免疫耐受的分子机制，为细胞治疗在器官移植中的应用提供理论基础和实验依据。

移植物的排斥反应是器官移植中最为棘手的问题之一。近年来，基于细胞治疗抗排斥反应的研究取得了良好效果。髓系来源的抑制性细胞（MDSC）属于固有免疫细胞，具有免疫抑制和免疫调节功能。在该项目的研究中，我们应用促红细胞生成素的衍生物环状螺旋B肽（CHBP）对MDSC诱导进行体外干预，发现可增加单核系MDSC（M-MDSC）的比例并增强其免疫抑制功能。将CHBP干预的M-MDSC过继输注到小鼠皮肤移植受体中发现，移植物的存活时间明显延长并有长期存活的趋势。受体体内和移植物内的T细胞比例明显减少但调节性T细胞数量增加，表明CHBP的干预可促进M-MDSC的抗移植物排斥能力。通过EporΔlyz小鼠，证实了CHBP对MDSC的作用主要依赖于其细胞表面的EPO受体EPOR。机制研究发现，CHBP主要通过细胞内EPOR下游的JAK2/STAT3/GATA3信号通路发挥作用；并进一步发现CHBP可诱导MDSC分化为一群具有更强抑制功能、表型为CD127+的M-MDSC。通过本研究，确立了具有更强免疫抑制功能的M-MDSC新亚群，并揭示了EPOR介导的JAK2/GATA3/STAT3途径在促进M-MDSC免疫抑制功能及抗移植排斥中的重要作用。