Endothelial microparticles in patients with kidney transplants

描述(由申请人提供)：这项建议寻求建立循环内皮微粒(EMP)水平作为肾移植环境中同种异体移植排斥反应的新生物标记物。内皮细胞(EC)在同种异体移植功能障碍和排斥反应的发病机制中起重要作用。随着免疫抑制和外科技术的改进，移植物存活率显著提高。然而，同种异体移植排斥反应仍然是同种异体移植失败的主要原因之一。内皮细胞是同种异体移植排斥反应的主要靶点之一，尤其是抗体介导的排斥反应。通常，移植肾的功能是通过血清肌酐(SC)水平来评估的。不幸的是，SC水平升高是移植肾功能障碍的非特异性标记物，它可能在许多不同的情况下发生。评估同种异体移植排斥反应的“金标准”是移植肾活检，这是一种侵入性的、昂贵的和相对危险的程序。急性细胞排斥反应(ACR)的模式有很好的文献记载和广泛的认识。然而，AMR的诊断是肾脏病理学中最具挑战性的问题之一。肾小管周围毛细血管(PTC)C4D染色是AMR的标志物之一。尽管如此，一些肾活检显示C4D染色，但没有AMR或ACR的组织学结果。最近，有证据表明某些形式的AMR对PTC C4D染色可能是阴性的。基于这些数据，对同种异体移植排斥反应的可靠和有临床意义的标记物的需求正在显现。微粒是由不同类型的细胞脱落的小的膜泡，含有原始细胞的细胞表面蛋白和细胞质成分。微粒子的产生是正常细胞功能的一部分，但随着细胞的凋亡和应激，微粒子的产生会增加。其他人和我们之前已经证明，循环中的EMP水平可以作为EC功能障碍的替代标志。最近的研究表明，包括肾脏在内的实体器官移植患者循环中的EMP水平发生了变化。我们证明，丙型肝炎肝硬变患者最初升高的循环EMP水平，在肝移植后两周下降到健康人的水平。这一数据表明，循环EMP水平可作为实体器官移植患者EC功能的生物标志物。根据这些发现，我们推测：1)循环EMP水平的升高可能是移植肾排斥反应的一个新的标志物；2)移植肾内皮细胞产生的EMP与受体内皮细胞产生的EMP的蛋白质组成不同，因此前者可作为移植肾EC功能的生物标志物。我们的假设将在两个特定目标下进行检验：1)评估循环内皮细胞微粒水平是否可以作为肾移植患者排斥反应的标志；2)进行一项初步研究，以调查循环EMP池是否可以进一步分离，以区分受者和同种异体内皮细胞产生的微粒。结论：R21是进一步研究EMP作为肾移植患者排斥反应的新标记物的关键步骤。

DESCRIPTION (provided by applicant): This proposal seeks to establish levels of circulating endothelial microparticles (EMP) as a novel biomarker of allograft rejection in the setting of kidney transplantation. Endothelial cells (EC) play an important role in the pathogenesis of allograft dysfunction and rejection. With improved immunosuppression and surgical technique, graft survival has significantly increased. Nevertheless, allograft rejection remains one of the main causes for allograft failure. The endothelium is one of the main targets in allograft rejection, especially antibody-mediated rejection (AMR). Typically, renal allograft function is evaluated by serum creatinine (SC) levels. Unfortunately, SC level elevation is a non-specific marker of renal allograft dysfunction, and it may occur in many different conditions. The "gold standard" test for the assessment of allograft rejection is renal allograft biopsy, which is an invasive, expensive and relatively risky procedure. The patterns of acute cellular rejection (ACR) are well-documented and broadly recognized. However, diagnosis of AMR is one of the most challenging in renal pathology. Peritubular capillary (PTC) C4d staining is one of the markers of AMR. Still, some kidney biopsies show C4d staining without histologic findings of AMR or ACR. Recently, evidence that some forms of AMR may be negative for PTC C4d staining has been described. Based on these data, the need for a reliable and clinically significant marker of allograft rejection is emerging. Microparticles are small membrane vesicles shed by different cell types, which contain cell surface proteins and cytoplasmic components of the original cell. The microparticle production is a part of normal cell function, but it increases by apoptotic cells and cells under stress. Others and we had previously demonstrated that levels of circulating EMP may be used as a surrogate marker of EC dysfunction. Recent studies have indicated changes in circulating EMP levels in patients with solid organ transplants, including kidneys. We demonstrated that circulating EMP levels, initially elevated in patients with Hepatitis C cirrhosis, were decreased to the levels seen in healthy people two weeks after liver transplantation. This data suggests that the levels of circulating EMP may be useful as a biomarker of EC function in patients with solid organ transplants. Based on these findings, we hypothesize that 1) an elevation in circulating EMP levels may be a novel marker of renal allograft rejection; 2) EMP produced by the renal allograft endothelium are different by their protein composition from EMP produced by the recipient endothelium; therefore, the former may be used as the biomarker of EC function of the renal allograft. Our hypotheses will be tested under two specific aims: 1) evaluate if the levels of circulating endothelial microparticles can be used as a marker of allograft rejection in patients with kidney transplants; 2) undertake a pilot study to investigate if the pool of circulating EMP may be further separated in order to distinguish between the microparticles produced by the recipient and allograft endothelium. Conclusions: This R21 is the essential step to advance the study of EMP as the novel marker of rejection in renal transplant patients.