ADPKD: Understanding immunosuppression mechanisms and discovering treatment

总结 免疫系统在保护我们免受疾病方面起着重要作用。间质性炎症 在ADPKD的人类和动物模型中一直有报道，并且在囊肿期间可能会变得更糟。 扩张导致肾实质损害加重。除了巨噬细胞的增加 在囊膜和囊周区域，T淋巴细胞在囊性肾中也增加。然而，在这方面， PKD突变的囊性肾上皮细胞是否以及如何逃避囊性肾上皮细胞的免疫攻击？ 在包囊形成和扩展过程中的微环境仍然是难以捉摸的。在这项研究中，我们调查了 程序性细胞死亡蛋白1（PD-1）和程序性死亡配体-1（PD-L1），一种PD-1配体， ADPKD。我们发现，1）PD-1在Pkd 1突变肾的T细胞上上调; 2）PD-L1在Pkd 1突变肾的T细胞上上调。 在Pkd 1突变的肾上皮细胞和组织中上调，在囊性细胞来源的 3）Pd-l1敲除延迟囊肿生长并增加Pkd 1敲除小鼠的存活; 用抗体靶向PD 1和PD-L1延迟Pkd 1敲除肾脏中的囊肿生长; 5）用 从ADPKD患者的囊性肾上皮细胞和尿液中分离的外泌体增加了Pkd 1野生型 肾上皮细胞增殖，并诱导这些细胞中PKD相关信号的激活; 6） 用囊性肾上皮细胞衍生的外来体处理促进Pkd 1突变肾中的囊肿生长; 7） 用ADPKD尿外泌体处理的肾上皮细胞（NRK-52 E细胞）也发生了囊肿样 胶原蛋白凝胶中的结构;和8）用GW 4869抑制外泌体分泌延迟Pkd 1中的囊肿生长 漂亮的肾脏我们的中心假设是，在囊性肾上皮细胞上PD-L1的上调， T细胞上的PD-1通过抑制T细胞功能导致囊性细胞的免疫逃避，并且外泌体 由囊性肾上皮细胞分泌的免疫抑制因子通过邻近的T细胞调节免疫抑制， 其他邻近细胞，包括肾上皮细胞和成纤维细胞，有助于囊肿生长。我们测试 这个假设有三个具体目标。这项研究将首次确定PD-1和PD-L1是否 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泌体是否有助于免疫抑制， 其他蜂窝通信。此外，我们将确定PD 1和PD-L1是否是有效的靶点， 在临床前环境中减缓疾病进展。完成这项研究将有助于更好地了解 肾囊肿形成的免疫监视机制以及囊性细胞外泌体在肾囊肿形成中的作用 调节免疫抑制和其他细胞间通讯，这将提供新的治疗方法， ADPKD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.