Extracellular vesicles and their cargo in the pathogenesis of acute respiratory distress syndrome and pulmonary fibrosis sequelae

当一些人受到严重感染时，他们身体的防御系统会过度反应，并通过一种叫做炎症的过程对自己的器官造成损害。当肺部以这种方式受损时，称为急性呼吸窘迫综合征（ARDS）。这可能是由于各种各样的损害，最常见的是细菌和病毒感染。最近，COVID-19大流行已成为ARDS的主要原因。急性呼吸窘迫综合征会导致肺部充满水，使呼吸变得非常困难。因此，这些患者需要在重症监护室接受照顾，在那里，机器可以帮助支持他们的呼吸。与此相关的死亡率是40%即使那些存活下来的人也有相当长的恢复期，生活质量下降。存活的患者中每20人中就有1人会形成肺瘢痕（纤维化）。体内的细胞具有形成囊泡的能力，这些囊泡可以脱落形成细胞外囊泡（EVs）。这些电动汽车可以在不同的细胞类型之间携带各种蛋白质和遗传物质。如果另一个细胞吸收了EV，该细胞的活性和功能可能会发生变化。无论是健康还是生病，我们体内的细胞都在不断地释放和吸收电动汽车。一些电动汽车是有益的，可以帮助支持细胞的健康功能。然而，其他电动汽车可以携带有害的内容物到细胞，这样做会促进器官损伤和疾病。对小鼠的研究表明，损伤性ev参与了ARDS炎症的发展。我之前的工作表明，ARDS患者肺部的防御细胞（肺泡巨噬细胞）不如健康人工作得好。它们清除死细胞的能力降低，这可能导致肺部炎症增加，从而导致ARDS的发展。防御细胞的能力越弱，患有ARDS的患者就越有可能在呼吸机上停留更长时间或死亡。进一步的研究发现，肺防御细胞对ev的摄取导致这种较弱的活性。小鼠研究表明，在肺损伤期间，ev可以将遗传物质转移到防御细胞，导致炎症增加，并可能增加肺瘢痕形成的风险。我的理论是，在ARDS中，防御细胞摄取ev及其携带的遗传物质导致防御细胞功能减弱，从而导致ARDS中的炎症，并可能增加发生肺瘢痕的风险。为了进行研究，我将首先确定急性呼吸窘迫综合征和肺瘢痕患者气道内ev的大小、数量和起源细胞。我还将测定这些EVs的蛋白质含量，以确定某些炎症蛋白在ARDS患者中是否增加。然后，我将根据它们的细胞来源分离出这些EV，并用它们来治疗健康的防御细胞，以确定哪种类型的EV导致了防御细胞活性的缺陷。一旦我确定了相关的EVs损伤类型，我将研究它们的遗传含量，以确定哪些遗传物质片段（microrna）在这种类型的EVs中表达得更高。然后，在用ev治疗防御细胞之前，我将使用镜像片段（安塔戈米尔）选择性地阻断这些遗传物质片段；如果防御细胞功能因此而增强，那么这些microrna的转移很可能是防御细胞缺陷的根本原因。然后，我将在死亡患者捐赠的小鼠ARDS模型和人肺中使用安塔戈米来阻断这些microrna。如果这种干预在这些模型中减少了炎症，它将支持ev转移microrna导致ARDS中观察到的防御细胞功能缺陷的理论。它还将支持阻断这些microrna是一种可用于治疗ARDS患者和ARDS后肺瘢痕形成的策略的理论。

When some people have a severe infection, their body's defence systems can over-react and cause damage to their own organs through a process called inflammation. When the lungs are damaged in this way, it is called acute respiratory distress syndrome (ARDS). This can occur due to a variety of insults, the most common being bacterial and viral infections. Recently, the COVID-19 pandemic has been a major cause of ARDS. ARDS causes the lungs to fill up with water, making it very difficult to breathe. These patients therefore need to be looked after in the intensive care unit, where a machine can help support their breathing. The death rate associated with this is 40%. Even those who survive ARDS have considerable recuperation periods and reduced quality of life. 1 in 20 patients who survive develop scarring of lungs (fibrosis). Cell within the body have the ability to form outpouchings which can break off to form extracellular vesicles (EVs). These EVs can carry various proteins and genetic material between different cell types. If another cell absorbs an EV, the activity and function of that cell may change. EVs are being released and absorbed by cells in our body constantly, when we are healthy and when we are sick. Some EVs are beneficial and can help support the healthy functioning of a cell. However, other EVs can carry damaging contents to cells and in doing so promote organ damage and disease. Studies in mice have shown that damaging EVs are involved in the development of inflammation in ARDS. My previous work showed that defender cells (alveolar macrophages) in the lungs of patients with ARDS do not work as well as in healthy people. Their ability to clear away dead cells is reduced, and this can lead to increased inflammation in the lungs as a result, thereby contributing to the development of ARDS. The weaker the abilities of the defender cells, the more likely it was that patients with ARDS will remain on a ventilator for longer or die. Further work identified that uptake of EVs by lung defender cells leads to this weaker activity. Mouse studies have shown that during lung injury, EVs can transfer genetic material to defender cells, leading to increased inflammation and potentially an increased risk of lung scarring. My theory is that in ARDS, uptake of EVs and their cargo of genetic material by defender cells leads to weakening of the defender cell function, which contributes to the inflammation seen in ARDS, and may increase the risk of developing lung scarring.To investigate, I will first aim to determine the size, number and the originating cell of EVs in the airways of patients with ARDS and lung scarring. I will also aim to determine the protein content of these EVs to see if certain inflammatory proteins are increased in ARDS patients. I will then separate the EVs based on their cell of origin, and use these to treat healthy defender cells to determine which type of EV causes the defect in defender cell activity. Once I identify the relevant damaging type of EVs, I will investigate their genetic content, to determine which fragments of genetic material (microRNAs) are more highly expressed in this type of EV. I will then selectively block these fragments of genetic material using mirror-image fragments (antagomirs) before treating defender cells with EVs; if the defender cell function is stronger as a result then transfer of these microRNAs are likely to be the underlying cause of the defender cell defect. I will then aim to block these microRNAs by using antagomirs in models of ARDS in mice and in human lungs donated by deceased patients. If this intervention reduces inflammation in these models, it will support the theory that transfer of microRNAs by EVs causes the defect in defender cell function observed in ARDS. It will also support the theory that blocking these microRNAs is a strategy which could be applied as a treatment for patients with ARDS and post-ARDS lung scarring.