The endothelial TM-PC system regulates tubular senescence and regeneration via p21 in diabetic nephropathy

内皮TM-PC系统通过p21调节糖尿病肾病的小管衰老和再生糖尿病肾病（dNP）是工业化国家终末期肾脏疾病的主要原因。小管间质纤维化比肾小球硬化更能预测肾功能下降。然而，肾小管损伤的病理机制在很大程度上仍然未知，这阻碍了新治疗方法的发展。后者在一定程度上反映了缺乏合适的动物模型。我们建立了一个小鼠模型，糖尿病小鼠的内皮细胞依赖性丝氨酸蛋白酶激活蛋白C （aPC，一种细胞保护和抗凝蛋白酶）水平降低，如果患有糖尿病，这些小鼠会出现明显的小管间质纤维化，这使我们能够研究糖尿病小管间质纤维化的调节机制。初步研究发现p21的表达增加，这些小鼠的小管衰老增加。体外研究表明，aPC调节p21的表达和小管衰老。管状p21的表达受表观遗传调控，因此可能有助于代谢记忆。重要的是，恢复apc依赖性信号可以逆转这些变化，这表明这种病理机制是可以治疗的。基于这些结果，我们假设内皮功能障碍和aPC的缺失导致p21的持续表达和小管衰老，从而损害dNP的小管再生能力。我们假设这将加重慢性肾小管损伤，但也会损害急性肾损伤后的肾小管修复。apc对肾小管衰老和小管再生的依赖性调节将为连接内皮功能障碍和肾小管损伤提供一个新的框架，并为慢性肾小管损伤和急性肾损伤后肾小管再生受损提供一个统一的机制。为了评估所提出的机制，我们打算解决以下目标：目的1：描述aPC和p21在dNP中控制管状细胞增殖和修复的机制相互作用。目的2：确定高血糖诱导和持续的肾小管p21表达与急性肾损伤后预后受损的机制相关性。目的3：确定aPC限制p21表达的机制。

The endothelial TM-PC system regulates tubular senescence and regeneration via p21 in diabetic nephropathyDiabetic nephropathy (dNP) is the leading cause of end stage renal disease in industrialized countries. Tubulointerstitial fibrosis predicts the decline of renal function better then glomerulosclerosis. The pathomechanisms of tubular injury remain, however, largely unknown, hampering the development of new therapeutic approaches. The latter reflects in part the lack of suitable animal models. We developed a mouse model, diabetic mice with reduced levels of the endothelial cell dependent serine protease activated protein C (aPC, a cytoprotective and anticoagulant protease), which develop marked tubulointerstitial fibrosis if diabetic, enabling us to study mechanisms regulating diabetic tubulointerstitial fibrosis. Preliminary work identified increased expression of p21 and increased tubular senescence in these mice. In vitro studies demonstrate that aPC regulates p21 expression and tubular senescence. Tubular p21 expression is epigenetic regulated, thus potentially contributing to the metabolic memory. Importantly, restoring aPC-dependent signalling can reverse these changes, demonstrating that this pathomechanisms is therapeutically amendable. Based on these results we hypothesize that endothelial dysfunction and loss aPC causes sustained p21 expression and tubular senescence, thus impairing the re-generative tubular capacity in dNP. We hypothesize that this will aggravate chronic tubular injury, but also impair tubular repair after an acute renal injury in pre-existing dNP (acute on chronic kidney injury). The aPC-dependent regulation of tubular senescence and hence tubular regeneration would provide a new framework linking endothelial dysfunction and tubular injury and would provide a unifying mechanism underlying the chronic tubular injury as well as the impaired tubular regeneration after acute kidney injury in dNP. To evaluate the proposed mechanism we intend to address the following aims: Aim 1: Delineate the mechanistic interaction of aPC and p21 in controlling tubular cell proliferation and repair in dNP.Aim 2: Define the mechanistic relevance of hyperglycaemia induced and sustained tubular p21 expression for impaired outcome following acute renal injury.Aim 3: Identify the mechanism through which aPC restricts p21 expression.