Quantifying Age-related Changes in the Mechanical Properties of Tissues

随着人们年龄的增长，身体的机械特性发生了变化，心血管系统的许多组成部分变得更加僵硬。动脉硬化与心力衰竭、中风和动脉瘤的死亡率增加有关。动脉硬化也可通过其他与年龄有关的疾病发生，例如血压升高、糖尿病和肾衰竭。总的来说，这些心血管系统的衰竭是西方世界最常见的死亡原因。身体内的其他组织也会随着时间的推移而恶化，虽然不会危及生命，但会严重影响生活质量，例如使人衰弱的腰痛与椎间盘的机械退化有关。随着年龄增长而改变的外表对个人健康也很重要，到2015年，全球抗衰老治疗市场预计将超过2500亿美元；这类个人护理产品的开发是英国经济的重要组成部分。因此，了解衰老过程如何导致组织硬化对于提高预期寿命非常重要，而且重要的是，随着越来越多的人口寿命延长，改善人口的福祉也很重要。我们理解衰老如何改变组织的机械特性的一个障碍是目前用于测量它们的相对原始的方法。它们最初是用来测量工程材料（如金属和聚合物）的性能；它们比生物材料坚硬得多，成分也更简单。然而，机械测试方法的最新发展使我们现在可以使用一种叫做纳米压痕的技术，它不仅可以用来测量组织的机械性能，还可以用来测量导致性能随年龄变化的微观成分。通过进一步开发这项新技术，我们将能够探索这些部件在老化过程中发生的变化，这些变化可以通过显微镜观察来监测，从而降低刚度和其他机械性能。由于取样材料的体积非常小，这项技术将使我们能够使用微创方法测量人体组织的特性。然后，这可以用来监测衰老和慢性疾病的进展，以及用于缓解症状的任何治疗。

As people get older the mechanical properties of the body change and many components of the cardiovascular system become stiffer. Stiffening of the arteries has been implicated in increased mortality from heart failure, stroke and aneurysms. Arterial stiffening can also occur through the action of other age-related conditions, e.g. raised blood pressure, diabetes and kidney failure. Collectively, these failures of the cardiovascular system are the most common cause of death in the western world. Other tissues within the body can also deteriorate with time and although not life threatening, can seriously affect the quality of life, e.g. debilitating lower back pain is associated with the mechanical deterioration of the intervertebral disc. Cosmetic changes with age are also important for personal well being and the global market in anti-ageing treatments is forecast to exceed $250 billion by 2015; development of such personal care products is an important part of the British economy. Thus understanding how the ageing process leads to the stiffening of tissue is important in improving life expectancy and importantly, improving the well being of the population as a greater proportion of the population is living longer.One obstacle to our understanding of how ageing changes the mechanical properties of tissue is the relatively primitive methods currently used to measure them. These were originally developed to measure the properties of engineering materials such as metals and polymers; these are much stiffer than biological materials and are simpler in composition. However, recent developments in mechanical testing methods allow us to now use a technique called nanoindentation that can be used to measure the mechanical properties, not only of tissue but also of the microscopic components that cause the changes in properties with age. By further developing this new technique we will be able to explore how changes in these components that occur during ageing, which can be monitored using microscope observation, degrade the stiffness and other mechanical properties. Because the volumes of material sampled are so small, the technique will allow us to measure the properties of human tissue using a minimally invasive approach. This can then be used to monitor the progress of ageing and chronic disease and any treatment used to alleviate symptoms.