Identifying effective therapies to prevent paralysis after aortic aneurysm repair surgery

项目摘要 在美国，每年诊断出大约24，000例胸腹主动脉瘤（TAAA）新病例。 美国. TAAA开放修复术最可怕的并发症是截瘫（5-10%的患者）， 手术后缺血性脊髓（SC）损伤。因此，迫切需要鉴定新的分子， 将补充现有的非药物预防战略。为此，我们开发了一个 TAAA开放修复的小鼠和狗模型，其中主动脉交叉阻断（ACC）导致中央索 水肿灰质损伤和后肢瘫痪 microRNA是短的非编码RNA，其负调节多个靶基因的表达， 与许多病理学有关。我们已经证明，miR-155，一种由 我们和其他人是高度促炎性的，是诱发炎症加剧的原因， 血-SC屏障渗漏、中央脊髓水肿发展、灰质损伤和瘫痪。即，我们 发现miR-155全缺失小鼠的瘫痪率为野生型小鼠的62.5%， 与减少灰质损伤有关。 此外，我们发现，在缺血条件下，miR-155损害Mfsd 2a的表达（主要是由于miR-155抑制了Mfsd 2a的表达）。 易化超家族结构域，包含2a），编码ω-3内皮转运蛋白的基因 二十二碳六烯酸（DHA，22：6 n-3），也涉及维持血液的完整性- 脑屏障重要的是，大脑的磷脂含有15%的DHA，但不能合成这种物质。 DHA是一种重要的维生素，因此需要持续的供应。DHA是大脑和大脑功能的关键。 生产对大脑至关重要的强效抗炎衍生物（二十二烷和elovanoids） 体内平衡因此，我们发现非瘫痪小鼠的SC表达Mfsd 2a水平显著高于正常小鼠。 高于ACC后瘫痪小鼠。 因此，我们提出了两种独立的方法来降低缺血后瘫痪的发生率： (1)使用miR-155反义寡核苷酸直接阻断miR-155有害活性;和（2） 增加SC的DHA供应。这两种治疗方法都会损害局部和全身的 炎症，减少中央脊髓水肿和灰质损伤的发展， 降低瘫痪率。 虽然先前已经在中风模型中研究了miR-155和DHA的作用，从而为miR-155和DHA的作用提供了有力的基础。 我们的策略从未在我们的小鼠ACC模型中进行过测试。由于TAAA维修遵循程序 外科手术，为预防性干预提供了一个机会窗口，我们的策略具有很强的 TAAA开放性修复手术中的翻译潜力。在未来，它们也可以在我们的狗身上进行测试， 主动脉腔内修复术的小鼠模型（正在开发中）。

PROJECT SUMMARY Approximately 24,000 new cases of thoraco-abdominal aortic aneurysms (TAAAs) are diagnosed each year in the USA. The most feared complication of TAAA open repair is paraplegia (5-10% of patients) caused by ischemic spinal cord (SC) injury following surgery. Therefore, there is urgency to identify new molecules that would complement existent, non-pharmacological preventive strategies. With this aim, we developed a mouse and a dog model of TAAA open repair where aortic cross-clamping (ACC) results in central cord edema, gray matter damage, and hindlimb paralysis. MicroRNAs are short, non-coding RNAs that negatively regulate the expression of multiple target genes and have been implicated in a number of pathologies. We have shown that miR-155, a microRNA established by us and others to be highly pro-inflammatory, is causal in inducing exacerbated inflammation that leads to blood-SC barrier leakage, central cord edema development, gray matter damage, and paralysis. Namely, we found that mice with miR-155 global deletion present a rate of paralysis 62.5% of that of wild-type mice, associated with reduced gray matter damage. In addition, we found that, under ischemic conditions, miR-155 impairs the expression of Mfsd2a (Major facilitator superfamily domain containing 2a), a gene that encodes an endothelial transporter of omega-3 docosahexaenoic acid (DHA, 22:6n-3) that is also implicated in the maintenance of the integrity of the blood- brain barrier. Importantly, the brain, whose phospholipids contain 15% of DHA, however cannot synthesize this compound and therefore needs a constant supply of it. DHA is key for both the function of the brain and the production of powerful anti-inflammatory derivatives (docosanoids and elovanoids) that are critical to brain homeostasis. Accordingly, we found that the SC of non-paralyzed mice express Mfsd2a levels significantly higher than paralyzed mice after ACC. Therefore, we propose two independent approaches to reduce the rate of paralysis following ischemia: (1) Directly blocking miR-155 deleterious activity using a miR-155 antisense oligonucleotide; and (2) Increasing DHA supply to the SC. Both treatments will impair the development of local and systemic inflammation, reduce the development of central cord edema and gray matter damage, and consequently decrease the rate of paralysis. While miR-155 and DHA effects has been previously studied in stroke models, thus providing strong ground for our strategies, they were never tested in our mouse ACC model. As TAAA repair follows a programmed surgical procedure, providing a window of opportunity for preventive intervention, our strategies hold a strong translational potential in TAAA open repair surgery. In the future, they could also be tested in our canine and mouse models (under development) of endovascular aortic repair.