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重要器官。它执行许多功能，包括血浆蛋白质合成和氨转化为尿素。随着年龄的增长，肝功能障碍的发生率显着增加，并且可能通过多种肝脏疾病和继发性原因（如代谢综合征）发生。例如，非酒精性脂肪性肝病在65岁以上人群中的发病率和严重程度都有所增加，酒精性肝病和自身免疫性肝病的发病率和严重程度也有类似的变化。在肝功能障碍中，社会经济和性别不平等也很严重，发病率随着年龄的增长而逐渐增加，在最老的年龄组中，不平等程度最大。患者血浆中胆红素和氨等内源性毒素的蓄积是肝衰竭的一般特征。这些反过来在其他器官中产生危及生命的影响（例如肝性脑病），导致与肝衰竭相关的高死亡率。移植是肝衰竭的首选治疗方法，但器官供体严重短缺，年龄增加独立预测供体和患者的移植结果均不佳。因此，除非能找到新的干预措施，否则随着全球人口老龄化，这一问题将显著升级。一种有吸引力的替代方法是设计生物人工肝系统（巴尔斯）。这些人工器官旨在作为患者的紧急体外桥梁，直到有合适的供体器官可用，或支持内源性器官功能，直到患者自己的肝脏再生。为此，BAL依赖于400- 800 g肝细胞来提供必要的生物转化和合成功能。然而，迄今为止测试的所有这些装置都失败了，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，尽管细胞本身仍然存活。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的细胞衰老，正是这一关键的衰老途径导致了肝特异性功能的丧失。然而，我们还表明，使用我们小组合成的新型小分子（resveralogues）可以保护细胞免受肝毒素诱导的衰老（SILT）。白藜芦醇本身激活多种途径，包括SIRT 1酶（其增强啮齿类动物体内的肝再生），但我们已经发现使用没有能力激活这种酶的新型类似物对SILT的等效保护-这表明了一种新的机制。这些发现使巴尔斯成为许多不同疾病的潜在新临床干预措施，并提出了老年人可能恢复肝功能的长期前景，无论是由于衰老或急性疾病而受到损害，也许可以完全避免移植，并考虑在他们因年龄而被排除在治疗之外时进行这种干预。这种方法仍然存在障碍，包括提高我们对我们的resveralogues的完整保护能力的机械理解，以及构建原型设备的工程挑战。然而，我们还开发了新型多孔生物材料，作为当前一代BAL生物反应器的替代品具有很大的潜力。最初的8个月将用于扩展我们先前在人肝细胞中SILT的工作，以涵盖啮齿动物和猪系统（大量用作体内模型），接下来我们将使用基因组学和芯片研究来鉴定resveralogue保护对抗SILT的主要途径，最后我们将优化包含新基质的原型装置，和细胞，并评估其在接近模拟体内情况下用负载有肝毒素的血浆攻击时的性能。

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.