Tubular Epithelial Cell Senescence Associated Secretory Phenotype: Impact on Regeneration in Acute and Chronic Kidney Disease

急性肾损伤（acute kidney injury，阿基）是一种常见且严重的临床问题，发病率高。阿基的发病率正在稳步上升，这在很大程度上是由于人口老龄化的增加。这一点特别令人担忧，因为随着年龄的增长，阿基后的恢复率显着下降。老年人更有可能发展为慢性肾衰竭，并在阿基后成为透析依赖者。已经确定了几个不同的年龄依赖性机制，可能是这个问题的基础。在这些机制中，体细胞衰老（SCS）已成为最强大的途径之一。SCS是一种不可逆的细胞周期停滞状态，其中细胞保持活力，但功能和代谢活性发生改变。这包括被称为衰老相关分泌表型（SASP）的分泌蛋白的特异性表达模式。最近的研究表明，SASP是负责显着旁分泌的细胞微环境的变化，导致正常组织的稳态的深刻破坏。在肾脏中，迄今为止还没有对SASP的作用进行研究。在初步的研究中，我们发现，肾小管细胞开发一个显着改变分泌组时，SCS诱导。肾成纤维细胞与衰老肾小管细胞的共培养引起快速活化成产生肌成纤维细胞的促纤维化基质。基于这些发现，我们假设肾小管SCS，特别是肾小管上皮细胞- SASP（TEC-SASP）是适应不良肾修复的重要贡献者。这是拟议项目的目标，调查这一假设使用体外和体内策略的组合。作为概念研究的证明，我们将研究允许在阿基后选择性消除衰老细胞的转基因小鼠。我们的假设是SCS的清除将改善促衰老和促纤维化机制，并将改善肾脏修复。聚焦于衰老的肾小管细胞与浸润的白细胞的串扰，我们将研究TEC-SASP对AKI损伤的肾脏中的巨噬细胞极化的影响。此外，我们将研究新的候选因素，差异调控的微阵列研究衰老肾小管细胞。特别是，我们将研究纤溶酶原激活因子-2（派-2）和Klotho的作用，使用体外基因过表达或敲低策略，用于共培养系统和靶向基因缺失的小鼠进行体内分析。最终，我们将把我们的数据与当地肾移植项目的患者肾活检相关联。我们提案的长期目标不仅是更好地了解SCS和SASP的生物学特性，而且还将确定新的分子靶点，这些靶点可能具有改善急性和慢性肾脏疾病肾脏结局的潜在治疗用途。

Acute kidney injury (AKI) is a common and serious clinical problem which is associated with a high morbidity. The incidence of AKI is steadily rising, which is largely due to an increase in the aging population. This is of particular concern because the recovery rate after AKI is significantly worse with advancing age. Older people are more likely to develop chronic renal failure and to become dialysis dependent after AKI. Several distinct age-dependent mechanisms have been identified that might underlie this problem. Among these mechanisms, Somatic Cellular Senescence (SCS) has emerged as one of the most powerful pathways. SCS is a state of irreversible cell cycle arrest in which the cell remains viable but develops altered functional and metabolic activity. This includes a specific expression pattern of secreted proteins which is referred to as the Senescence-Associated-Secretory-Phenotype (SASP). Recent studies have shown that the SASP is responsible for significant paracrine changes in the cellular microenvironment leading to a profound disruption of normal tissue homeostasis. In the kidney, no research on the role of the SASP has been conducted so far. In preliminary studies, we found that renal tubular cells develop a significantly altered secretome when SCS is induced. Co-culturing of kidney fibroblasts with senescent tubular cells caused a rapid activation into pro-fibrotic matrix producing myofibroblasts. Based on these findings we hypothesize that tubular SCS and in particular the Tubular Epithelial Cell - SASP (TEC-SASP) are important contributors to maladaptive renal repair. It is the goal of the proposed project to investigate this hypothesis using a combination of in vitro and in vivo strategies. As a proof of concept study we will investigate transgenic mice which allow for a selective elimination of senescent cells after AKI. Our hypothesis is that the clearance of SCS will ameliorate pro-aging and pro-fibrotic mechanisms and will improve kidney repair. Focussing on the cross-talk of senescent tubular cells with infiltrating leukocytes we will study the effects of TEC-SASP on macrophage polarization in AKI-damaged kidneys. Moreover, we will study novel candidate factors that were differentially regulated in a microarray study of senescent tubular cells. In particular, we will study the role of plasminogen-activating-factor-2 (PAI-2) and of Klotho using in vitro genetic overexpression or knock-down strategies for co-culture systems and mice with targeted gene deletion for in vivo analysis. Ultimately, we will correlate our data to patient renal biopsies from the local kidney transplant program. The long-term objective of our proposal will not only be a better biological understanding of SCS and SASP but also the identification of new molecular targets that could be of potential therapeutic use for improving renal outcome in acute and chronic kidney disease.