ADPKD: Understanding immunosuppression mechanisms and discovering treatment

摘要 免疫系统在保护我们免受疾病侵袭方面发挥着重要作用。间质性炎症有 在人类和动物模型中一直有ADPKD的报道，在囊肿期可能会恶化 扩张，导致肾实质更多的损害。除了巨噬细胞的增加 在间质和囊周，囊性肾中的T淋巴细胞也增多。然而， PKD突变的囊性肾上皮细胞是否以及如何逃避免疫攻击 囊腔起始和扩张过程中的微环境仍然难以捉摸。在本研究中，我们调查了这些角色 程序性细胞死亡蛋白1(PD-1)和程序性死亡配体-1(PD-L1)，PD-1配体，在 ADPKD.我们发现，1)PD-1在PKD1突变肾脏的T细胞上表达上调；2)PD-L1上调 在突变的肾上皮细胞和组织中表达上调，在来源于囊性细胞的表达增加 3)PD-L1基因敲除延缓了PKD1基因敲除小鼠的包囊生长，提高了小鼠的存活率；4) 以PD1和PD-L1为靶点的抗体延缓了PKD1基因敲除肾脏的囊性生长；5)治疗 从ADPKD患者的囊性肾上皮细胞和尿液中分离的外切体使PKD1野生型增加 肾上皮细胞增殖，并诱导细胞内PKD相关信号的激活；6) 囊性肾上皮细胞来源的外切体治疗促进PKD1突变肾脏的囊性生长； ADPKD尿外切体处理的肾上皮细胞(NRK-52E细胞)也出现囊肿样 胶原蛋白凝胶中的结构；以及8)GW4869抑制外切体分泌延缓PKD1中的包囊生长 敲打出的肾脏。我们的中心假设是PD-L1上调囊性肾上皮细胞和 T细胞上的PD-1通过抑制T细胞功能和外切体导致囊性细胞的免疫逃逸 囊性肾上皮细胞分泌的T细胞通过相邻T细胞调节免疫抑制及其功能 其他邻近的细胞，包括肾上皮细胞和成纤维细胞，促进了囊肿的生长。我们测试 这一假设有三个具体目的。这项研究将首次确定PD-1和PD-L1 是囊性肾脏中的免疫抑制因子，有助于囊性上皮细胞逃避免疫攻击。 ADPKD，以及囊性上皮细胞分泌的外切体是否有助于免疫抑制和 其他蜂窝通信。此外，我们将确定PD1和PD-L1是否为有效的目标 在临床前环境中减缓疾病进展。完成这项研究将使我们更好地理解 肾囊肿形成过程中的免疫监视机制及囊性细胞外切体在肾小球疾病中的作用 调节免疫抑制和其他细胞间的通讯，这将提供新的治疗方法 ADPKD的治疗策略。

Summary The immune system plays an important role in protecting us from disease. Interstitial inflammation has been consistently reported in human and animal models of ADPKD, and it may become worse during cyst expansion which results in more damages in renal parenchyma. In addition to the increase of macrophages in the interstitium and pericystic areas, T lymphocytes are also increased in cystic kidneys. However, whether and how PKD mutant cystic renal epithelial cells escapes immune attacks in cystic microenvironment during cyst initiation and expansion remains elusive. In this study, we investigate the roles of programmed cell death protein 1 (PD-1) and programmed death ligand-1 (PD-L1), a PD-1 ligand, in ADPKD. We found that, 1) PD-1 was upregulated on T cells in Pkd1 mutant kidneys; 2) PD-L1 was upregulated in Pkd1 mutant renal epithelial cells and tissues, and was increased in cystic cell derived exosomes; 3) knockout of Pd-l1 delayed cyst growth and increased the survival of Pkd1 knockout mice; 4) targeting PD1 and PD-L1 with antibodies delayed cyst growth in Pkd1 knockout kidneys; 5) treatment with exosomes isolated from cystic renal epithelial cells and urine of ADPKD patients increased Pkd1 wild type renal epithelial cell proliferation, and induced the activation of PKD associated signaling in these cells; 6) treatment with cystic renal epithelial cell derived exosomes promoted cyst growth in Pkd1 mutant kidneys; 7) renal epithelial cells (NRK-52E cells) treated with ADPKD urinary exosomes also developed cysts-like structures in collagen gels; and 8) inhibition of exosome secretion with GW4869 delays cyst growth in Pkd1 knockout kidneys. Our central hypothesis is that upregulation of PD-L1 on cystic renal epithelial cells and PD-1 on T cells results in immune evasion of cystic cells via inhibition of T cell function, and exosomes secreted by cystic renal epithelial cell regulate immunosuppression via adjacent T cells and the function of other neighboring cells, including renal epithelial cells and fibroblasts, contributing to cyst growth. We test this hypothesis with three specific aims. This study will determine for the first time whether PD-1 and PD-L1 are immune-suppressors in cystic kidneys, which helps cystic epithelial cells to escape immune attack in ADPKD, and whether exosomes secreted by cystic epithelial cells contribute to immune suppression and other cellular communication. In addition, we will determine whether PD1 and PD-L1 are effective targets to slow disease progression in preclinical setting. Accomplishing this study will lead to a better understanding of the mechanism of immune surveillance in renal cyst formation and the roles of cystic cell exosomes in regulating immunosuppression and other cell-to-cell communication, which will provide novel therapeutic strategy for ADPKD treatment.