A live model to study mucociliary clearance in health and disease

人体的肺部是气体交换的场所，在这里，含氧的空气被吸入，二氧化碳被呼出。这种与外界的直接互动使肺部特别容易受到污染物、细菌、病毒和真菌等有害外来物质的侵入。为了防止它们进入人体，一个保护性屏障保护了暴露在外的肺部表面。这个屏障是由粘液组成的，粘液是一种凝胶状物质，它的作用就像一个“分子筛”，可以捕获吸入的传染性病原体和污染物。一旦被困住，这些异物需要在它们造成损害之前从肺部取出。特定的肺细胞，称为纤毛细胞，将微小的毛发状结构（纤毛）投射到上面的黏液层。纤毛以一种协调的方式一起运动，从而产生一种定向流动，将粘液和任何被困的物质从肺部带走。这个过程被称为粘液纤毛清除，如果它有缺陷，就会导致疾病。粘液纤毛清除缺陷的疾病包括囊性纤维化，其中粘液粘稠且不能移动；哮喘，粘液分泌过多会导致气道阻塞；原发性纤毛运动障碍纤毛运动受损，粘液无法清除。这些疾病，特别是囊性纤维化和原发性纤毛运动障碍，会增加感染的易感性，这可能是致命的。为了有效地治疗这些疾病，我们需要准确地了解粘膜纤毛清除是如何工作的，这样我们就可以设计药物来改善患者的预后。科学家经常使用模式生物来了解生物过程的细节，这些过程很难在人类身上进行研究，或者在伦理上是不合适的。对于粘液纤毛清除，哺乳动物模型，特别是小鼠，通常用于模拟疾病或了解特定基因在该过程中的作用。然而，肺在体内的解剖位置意味着很难研究粘膜纤毛清除的动力学，并且经常涉及可能对小鼠有害的侵入性技术。在本研究计划中，我们引入了一种替代模型，即热带爪蟾（Xenopus tropicalis）的蝌蚪，以取代小鼠在这些研究中的使用。重要的是，它们的皮肤表面产生粘液，并有纤毛细胞移动粘液，就像人类的肺一样。通过该模型可以阐明特定基因在纤毛清除中的功能，以及粘液如何与纤毛和其他物质（如细菌）相互作用，从而扩展我们对人类纤毛清除的理解。至关重要的是，我们使用的蝌蚪处于早期发育阶段，被认为是没有知觉的。我们这个项目的目的是开发和验证这个使用蝌蚪皮肤的粘液纤毛清除的活体模型，以便在取代和减少对小鼠的依赖的同时获得新的科学见解。

The human lungs are the sites of gaseous exchange where air, containing oxygen, is breathed in and carbon dioxide is breathed out. This direct interaction with the outside world makes the lungs particularly vulnerable to the entry of harmful foreign agents such as pollutants and bacteria, viruses and fungi. In order to prevent their entry into the body, a protective barrier shields the exposed surfaces of the lungs. This barrier is composed of mucus, a gel-like material that acts like a 'molecular sieve' to trap inhaled infectious agents and pollutants. Once trapped, these foreign bodies need to be removed from the lung before they cause damage. Specific lung cells, called ciliated cells, project tiny hair-like structures (cilia) into the overlying mucus layer. The cilia move together in a coordinated manner so as to generate a directional flow that takes the mucus, and any trapped material, away from the lungs. This process is known as mucociliary clearance and if it is defective this can lead to disease. Examples of diseases with defective mucociliary clearance includes cystic fibrosis, where mucus is thick and sticky and cannot be moved; asthma, where an overproduction of mucus can cause airway obstruction; and primary ciliary dyskinesia where cilia movement is impaired and so mucus cannot be cleared. These diseases, particularly cystic fibrosis and primary ciliary dyskinesia, lead to increase vulnerability to infection, which can prove fatal.In order to effectively treat these diseases, we need to understand precisely how mucociliary clearance works so that we can design drugs to improve outcomes for patients. Scientists often employ model organisms to understand the details of a biological process that is difficult, or ethically improper, to study in humans. With mucociliary clearance, mammalian models, particularly mice, are commonly used to either mimic diseases or to understand the role of particular genes in the process. However, the anatomical location of the lungs within the body means that it is difficult to study the dynamics of mucociliary clearance and often involves invasive techniques that can be harmful to the mice. In this research proposal, we introduce an alternative model, the tadpole of the frog species, Xenopus tropicalis, to replace the use of mice in these studies. Importantly, their skin surface produces mucus and has ciliated cells that move the mucus, just like in the human lungs. Details about the function of particular genes in mucociliary clearance and how mucus interacts with cilia and with other agents (e.g. bacteria) can be elucidated with this model, extending our understanding of mucociliary clearance in humans. Crucially, the tadpoles that we use are at an early developmental stage and are considered to be non-sentient. Our aim for this project is to develop and validate this live model of mucociliary clearance using the tadpole skin in order to gain new scientific insight at the same time as replacing, and reducing the reliance on, mice.