Regulation of p21-induced tubular senescence and impaired renal regeneration in the context of diabetic kidney disease: the role of coagulation factor FXII

糖尿病肾病(DKD)的一个尚未解决的医学问题是，尽管接受了治疗，但肾脏缺乏恢复(所谓的“高血糖记忆”)。肾细胞衰老和与不孕症炎症相关的表观固定基因失调被认为有助于高血糖记忆。这一假设得到了我们自己的数据的支持，这些数据表明，尽管糖尿病患者和糖尿病小鼠的代谢控制有所改善，但细胞周期调节因子和衰老相关基因p21的持续诱导。持续的p21表达受表观遗传调控，与肾小管衰老和无菌炎症有关，但可被DNMT1诱导逆转。然而，目前尚不清楚p21诱导是否足以诱导肾小管衰老和相关的无菌炎症，肾小管衰老的细胞后果是什么，相关的炎性细胞是否有助于疾病的解决，或者衰老细胞的消除是否对DKD的进程和/或肾脏的再生潜力产生积极影响。导致肾小管衰老的机制也不清楚。在更多未发表的数据中，我们能够显示DKD患者尿液和肾小管细胞中的酶原凝血因子XII(FXII)增加。此外，FXII有助于实验性DKD的发展，相关的衰老和无菌炎症。体外实验表明，酶原FXII通过受体介导的机制(通过uPAR)诱导这些效应。然而，目前尚不清楚FXII在肾小管上的表达有何病理意义(自身或旁分泌的FXII效应？)，哪些额外的受体传递FXII介导的效应(可能是整合素)，以及FXII是否是DKD的治疗靶点。我们推测，增加的肾小管FXII表达诱导(自身或旁分泌)p21相关的肾小管衰老，导致肾小管功能障碍和无菌炎症。这些机制抑制了DKD的肾脏修复机制。为了验证这一假说，我们打算研究以下目标：1.研究p21相关的肾小管衰老与DKD的致病相关性；2.研究FXII诱导肾小管衰老的机制。将使用最先进的方法来解决这些目标(例如，SnRNAseq、SnATACseq、新的小鼠模型，例如体内细胞跟踪或靶向消除衰老细胞)。这些研究将为肾小管衰老对DKD持续存在的重要性提供新的机制方面的见解，并将探索酶原FXII在DKD中的新作用。

An unsolved medical problem of diabetic kidney disease (DKD) is the lack of renal recovery despite therapy (the so-called "hyperglycaemic memory"). Renal cell senescence and epigenetically fixed gene dysregulation associated with sterile inflammation are thought to contribute to hyperglycaemic memory. This assumption is supported, among other things, by our own data, demonstrating a persistent induction of the cell cycle regulator and senescence-associated gene p21 despite improved metabolic control in people with diabetes and diabetic mice. Persistent p21 expression was epigenetically regulated, associated with tubular senescence and sterile inflammation, but could be reversed by DNMT1 induction. Yet, it remains unknown whether p21 induction is sufficient to induce tubular senescence and the associated sterile inflammation, what the cellular consequences of tubular senescence are, whether the associated profile of inflammatory cells contributes to failed disease resolution, or whether the elimination of senescent cells positively affects the course of DKD and/or the regeneration potential of the kidney. The mechanism leading to tubular senescence are also unclear. In further unpublished data, we were able to show that the zymogen coagulation factor XII (FXII) is increased in urine and in tubular cells in DKD. Additionally, FXII contributes to the development of experimental DKD, associated senescence and sterile inflammation. In vitro experiments suggest that the zymogen FXII induces these effects through a receptor-mediated mechanism (via uPAR). However, it is unclear what pathological relevance tubular FXII expression has (auto- or paracrine FXII effect?), which additional receptors convey the FXII-mediated effects (possibly integrins), and whether FXII is a therapeutic target in DKD. We postulate that increased tubular FXII expression induces (auto or paracrine) p21-associated tubular senescence, contributing to tubular dysfunction and sterile inflammation. These mechanisms inhibit renal repair mechanisms in DKD. In order to test this hypothesis, we intend to study the following aims: 1. Characterization of the pathogenetic relevance of p21-associated tubular senescence for the perpetuation of DKD; 2. Characterization of the mechanism by which FXII induces tubular senescence. State-of-the-art approaches will be used to address these aims (e.g. snRNAseq, snATACseq, new mouse models, e.g. in vivo cell tracing or targeted elimination of senescent cells). These studies will provide new and mechanistic insights into the importance of tubular senescence for the perpetuation of DKD and will investigate a novel role of the zymogen FXII in DKD.