Bioartificial interventions for organ senescence: Understanding and preventing senescence induced by liver toxins (SILT) in hepatocytes.

肝脏是受衰老影响的关键器官。它具有许多功能，包括血浆蛋白质合成和将氨转化为尿素。肝功能障碍的发生率随着年龄的增长而显着增加，可通过多种肝病和继发性原因(如代谢综合征)发生。例如，在65岁以上的年龄组中，非酒精性脂肪性肝病的频率和严重性都有所增加，酒精性和自身免疫性肝病也观察到了类似的模式。肝功能障碍中也存在实质性的社会经济和性别不平等，发病率随着年龄的增长而逐渐增加，从而在最年长的年龄组中产生最大的不平等。内源性毒素如胆红素和氨在患者血浆中的积聚是肝功能衰竭的一个普遍特征。这些反过来又在其他器官产生威胁生命的影响(例如肝性脑病)，从而导致与肝功能衰竭相关的高死亡率。移植是治疗肝功能衰竭的首选方法，但器官捐赠者严重短缺，年龄增加独立地预示着捐赠者和患者的移植结果都很差。因此，除非找到新的干预措施，否则随着全球人口的老龄化，这个问题将显著升级。一个有吸引力的替代方法是设计生物人工肝系统(BALS)。这些人工器官的目的要么是充当患者的紧急体外桥梁，直到有合适的供体器官可用，要么是在患者自己的肝脏再生之前支持内源性器官功能。为此，BAL依赖400-800克肝细胞来提供必要的生物转化和合成功能。然而，到目前为止测试的所有这些设备都失败了，因为与肝功能衰竭动物血清中存在的肝毒素接触会破坏肝细胞清除氨和合成白蛋白的能力，尽管细胞本身仍然活着。最近，我们发现内源性血浆肝毒素在数小时内诱导人肝细胞衰老，正是这一关键的衰老途径导致了其肝脏特异性功能的丧失。然而，我们也证明了使用我们小组合成的新的小分子(白藜芦醇)来保护细胞免受肝毒素(淤泥)诱导的衰老是可能的。白藜芦醇本身激活了多种途径，包括酶SIRT1(它可以促进啮齿类动物体内的肝脏再生)，但我们使用没有激活这种酶的新的类似物，发现了同样的保护淤泥的作用-这表明了一种新的机制。这些发现使BALS成为许多不同疾病的潜在临床干预措施，并提供了一个长期的前景，即老年人可能会恢复肝功能，无论是由于衰老还是急性疾病，可能完全避免移植，当他们因年龄而被排除在治疗之外时，可以考虑进行这种干预。采取这一办法的障碍依然存在，包括加强我们对安全装置全部保护能力的机械理解，以及建造原型装置所面临的工程挑战。然而，我们也开发了新型的多孔生物材料，这些材料具有很大的潜力来替代当前一代的BAL生物反应器。最初的8个月时间将用来扩大我们之前在人类肝细胞中的淤泥研究，以涵盖啮齿动物和猪系统(大量用作活体模型)，接下来我们将使用基因组学和Silco研究来确定resveraliges防止淤泥的主要途径，最后我们将优化一个包含新基质和细胞的原型设备，并在近距离模拟体内情况下评估其性能，当受到充满肝毒素的血浆挑战时。

The liver is a key organ affected by ageing. It performs many functions including plasma protein synthesis and the conversion of ammonia to urea. Liver dysfunction rates increase markedly with age and can occur both through multiple liver diseases and secondary causes such as metabolic syndrome. For example, non-alcoholic fatty liver disease increases in both frequency and severity in the over 65 age- groups and similar patterns are observed for both alcoholic and autoimmune liver diseases.Substantial socioeconomic and sex inequalities also exist within liver dysfunction with incidence rates increasing gradually with age to produce the largest inequalities in the oldest age-groups. The accumulation of endogenous toxins such as bilirubin and ammonia in patient plasma is a general feature of liver failure. These in turn produce life-threatening effects in other organs (e.g. hepatic encephalopathy) contributing to the high mortality associated with liver failure. Transplantation is the preferred treatment for liver failure but there is a serious shortage of organ donors and increasing age independently predicts poor transplant outcomes for both donor and patient. Thus, unless new interventions can be found, this problem will escalate markedly as the global population ages.One attractive alternative approach is to engineer bioartificial liver systems (BALS). These artificial organs are intended either to act as emergency extracorporeal bridges for patients until a suitable donor organ is available, or to support endogenous organ function until the patient's own liver regenerates. For this a BAL relies on 400-800g of hepatocytes to provide the necessary biotransformation and synthetic functions. However, all such devices tested to date have failed because contact with hepatotoxins present in the serum of animals with liver failure destroys the capacity of the hepatocytes to clear ammonia and synthesise albumin although the cells themselves remain viable. Recently, we discovered that endogenous plasma hepatotoxins induce cellular senescence in human hepatocytes within hours and it is this key ageing pathway which is responsible for their loss of liver specific functions. However, we have also shown that it is possible to protect cells from this Senescence Induced by Liver Toxins (SILT) using novel small molecules our group has synthesised (resveralogues). Resveratrol itself activates a variety of pathways including the enzyme SIRT1 (which enhances liver regeneration in rodents in vivo) but we have found equivalent protection from SILT using novel analogues with no capacity to activate this enzyme - indicating a novel mechanism.These discoveries render BALS a potential new clinical intervention for many different disorders and hold out the long-term prospect that older individuals may recover liver function, whether compromised through ageing or acute disease, perhaps avoid transplantation altogether and be considered for this intervention when before they would have been excluded from treatment because of their age. Obstacles to this approach remain, including enhancing our mechanistic understanding of the full protective capacities of our resveralogues, and the engineering challenges of building a prototype device. However, we have also developed novel porous biomaterials which hold great potential as replacements for the current generation of BAL bioreactors. An initial 8-month period will be spent in expanding our prior work in SILT in human hepatocytes to cover rodent and porcine systems (heavily used as in vivo models), next we will use genomics and in silco studies to identify the major pathways by which resveralogues protect against SILT and finally we will optimise a prototype device comprising novel matrices, and cells and evaluate its performance in a close mimic of the in vivo situation when challenged with plasma loaded with liver toxins.