Pathophysiological significance of the cell cycle in acute kidney injury

急性肾损伤是一种严重的临床病症，其中肾功能突然下降，并且没有特异性治疗。在许多情况下，肾功能可以恢复，但也会发生永久性损伤，导致终末期肾病。肾脏恢复是否成功取决于几个因素。一个重要的组成部分是肾小管细胞增殖，这通常被认为有助于受损肾小管的修复。然而，在我们的初步工作中，我们观察到损伤诱导的增殖不仅可以是修复性的，而且是有害的。在近端小管中特别缺乏细胞周期蛋白cyclin D1的转基因小鼠中，我们观察到增殖能力的降低保护了肾脏。这些发现与其他药理学细胞周期抑制组的先前观察结果相符。在本申请中，我们将研究这种现象的基本过程，并测试细胞周期蛋白D1去磷酸化的原理是否可以用于治疗。为了解决后一点，我们将在小鼠模型中使用基于siRNA的敲低策略，该策略可以允许潜在的临床翻译。为了解决机制基础的问题，我们在初步工作中进行了转录组分析，其中我们检查了近端小管中有无细胞周期蛋白D1消融的差异。在这样做的过程中，我们正在寻找细胞周期蛋白D1与损害加重转录的关联。事实上，我们发现转录差异只针对细胞周期基因，因此我们假设保护机制直接来自细胞周期激活本身的抑制。作为一个关键因素，我们现在想测试“细胞能量假说”，其中我们假设细胞周期阻滞是通过保护细胞周期激活的过度能量消耗来保护肾。我们计划在细胞培养实验以及小鼠和斑马鱼胚胎中测试这一假设，通过使用不同的损伤模型和增殖干预来分析细胞和组织对细胞周期激活的反应。为此，我们将使用能量载体测量，基质辅助激光解吸/电离飞行时间质谱成像（MALDI-TOF-MSI）和细胞损伤分析。总之，预期的结果应该有助于更好地了解肾小管细胞增殖在急性肾功能衰竭中的作用。长期目标是建立一个基础，使新的治疗策略的推导。

Acute kidney injury is a serious clinical condition in which kidney function declines abruptly and for which there is no specific therapy. In many cases, kidney function can recover, but permanent damage also occurs, leading to end stage renal disease. Whether kidney recovery is successful depends on several factors. One important component is tubular cell proliferation, which is usually considered to contribute to the repair of damaged renal tubules. However, in our preliminary work, we observed that damage-induced proliferation can be not only reparative but also detrimental. In transgenic mice specifically lacking the cell cycle protein cyclin D1 in the proximal tubule, we observed that reduced proliferative capacity protects the kidney. These findings fit with previous observations from other groups with pharmacological cell cycle inhibition. In the present application, we will investigate the underlying processes of this phenomenon and we will test whether the principle of cyclin D1 antagonization can be exploited therapeutically. To address the latter point, we will use an siRNA-based knockdown strategy in a mouse model that could allow for potential clinical translation. To address the question of the mechanistic basis, we performed transcriptome analyses in preliminary work in which we examined differences in proximal tubules with and without cyclin D1 ablation. In doing so, we were looking for an association of cyclin D1 with damage-aggravating transcripts. Indeed, we found transcriptional differences exclusively for cell cycle genes, so we assume that the protective mechanism arises directly from inhibition of cell cycle activation per se. As a crucial factor, we now want to test the 'cellular energy hypothesis', in which we postulate that cell cycle blockade is nephroprotective by protecting against excessive energy expenditure of cell cycle activation. We plan to test this hypothesis in cell culture experiments as well as in mouse and zebrafish embryos by using different damage models and proliferation interventions to analyze cell and tissue responses in response to cell cycle activation. To this end we will use energy carrier measurements, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry imaging (MALDI-TOF-MSI), and cellular damage analysis. Together, the expected results should help to better understand the role of tubular cell proliferation in acute renal failure. The long-term goal is to establish a basis that will allow the derivation of new therapeutic strategies.