A Mathematical-Experimental Strategy to Discern the Molecular Basis of "Successful Mucus"

在人类的呼吸道中，粘液屏障是防御的前线，而免疫系统是次要的。“成功的粘液”有效地捕获侵入的货物(病原体和微粒)，并不断地将粘液和货物从呼吸道清除到喉部，在那里它被吞咽到肠道，并在粘液屏障穿透之前被化学解除武装，防止暴露在细胞或血液中。现在许多疾病和病理都与“不成功的粘液”有关。从囊性纤维化等遗传性疾病到慢性阻塞性肺疾病(COPD)等后天性疾病。粘液已成为肺部健康的矿工金丝雀。这项研究中概述的实验数学项目提出了一种战略，用严格、稳健的科学指标取代肺部疾病的生活质量指标，将新的实验技术与数据分析、模型选择和预测计算的数学相结合。这些进展有望为粘液生物学提供新的标准，有可能将临床实践从患者症状转变为预防性监测和评估粘液传输特性，再到识别可能的成败来源。对本科生、研究生和博士后学者进行教育和培训，将生物学、生物物理学、应用数学、统计学和医学的知识和技术整合在一起，有助于丰富所有学科和领域，进而有助于学术界和公共和私营部门的未来一代研究人员和从业者。每个器官的粘液都有一个可在细胞培养中复制的基线组成(粘蛋白大分子、蛋白质、电解质和水的光谱)，然后是一大批“活的”分子物种(病原体和副产品、免疫反应试剂、死亡细胞的DNA，以及来自环境和生活方式因素的物质)。这种分子组成向健康的粘液传达了阻止物种从纳米到微米的扩散的能力，以及被激活(从而被清除)到单个纤毛的皮牛顿力的能力。所有通过显微镜跟踪的颗粒在粘液中的扩散是非正常的，其扩散的统计数字随着颗粒大小和表面化学的变化而变化；所有的流变学数据都指向非线性粘弹性行为，这种行为取决于肺内推进机制的频率、长度和压力水平的不同。成功粘液的这种惊人的能力，对不同的损伤和纤毛和空气阻力清除它的反应是惊人的，这混淆了粘液生物学的科学。因此，没有粘液运输特性的评估标准，没有对成功的粘液进行确凿的测试，没有了解什么分子物种或串联物种决定粘液运输特性的成败，也没有严格的基础来测试潜在的补救措施来恢复健康的运输特性。在这个项目中，将探索根据粘液的分子基础分解粘液的实验技术，将临床粘液自上而下地解构为基线和生活诱导成分，并从无菌细胞培养基线与受控的生活诱导成分叠加进行自下而上的重建。将开发数学技术来评估整个粘液样本空间内与生理相关的扩散和粘弹性特性，包括解决关于异常扩散和非线性粘弹性的公开数学问题的策略。

In human airways, the mucus barrier is the front line of defense whereas the immune system is secondary.  "Successful mucus" efficiently traps invasive cargo (pathogens and particulates) and continuously clears mucus and cargo from the airways to the larynx where it is swallowed to the gut and chemically disarmed before penetration of the mucus barrier, preventing exposure to cells or the blood stream.  Many diseases and pathologies are now associated with "unsuccessful mucus," from genetic diseases like cystic fibrosis to acquired conditions such as chronic obstructive pulmonary disease (COPD).  Mucus has become the miner's canary of lung health.  The experimental-mathematical projects outlined in this research present a strategy to replace quality-of-life metrics of lung disorders with rigorous, robust scientific metrics that integrate novel experimental technique with the mathematics of data analytics, model selection, and predictive computation.  These advances promise a new standard for mucus biology, with the potential to transform clinical practice from patient symptoms to preemptive monitoring and assessment of mucus transport properties, to identification of likely sources of success and failure, and to test impact and duration of therapeutics.  The education and training of undergraduates, graduate students, and postdoctoral scholars in the integration of knowledge and techniques from biology, biophysics, applied mathematics, statistics, and medicine contributes to the enrichment of all disciplines and fields, and furthermore to the future generation of researchers and practitioners in academia and the public and private sector.    Mucus in every organ has a baseline composition (a spectrum of mucin macromolecules, proteins, electrolytes, and water) that is reproducible in cell cultures, and then a host of "living-induced" molecular species (pathogens and by-products, immune response agents, DNA from dead cells, and substances from environmental and lifestyle factors).  This molecular composition conveys to healthy mucus the ability to impede the diffusion of species from nanometer to micron size, and the ability to be activated (thereby cleared) down to pico-Newton forces of single cilia.  All particles tracked via microscopy in mucus diffuse "non-normally" and the statistics of their diffusion varies with particle size and surface chemistry; all rheology data point to nonlinear viscoelastic behavior that differs depending on the frequency, lengthscale, and stress level of the propulsion mechanisms in the lung.  This striking capacity of successful mucus to respond simultaneously yet differently to the diversity of insults and to its clearance by cilia and air drag has confounded the science of mucus biology.  Consequently, there has been no assessment standard of transport properties for mucus, no conclusive test for successful mucus, no understanding of what molecular species or tandem species determine mucus success or failure in either transport property, and no rigorous basis to test potential remedies to reinstate healthy transport properties.  In this project, experimental techniques will be explored to decompose mucus with respect to its molecular basis, with top-down deconstruction of clinical mucus into baseline and living-induced components, and bottom-up reconstruction from a sterile cell culture baseline superimposed with controlled living-induced components.  Mathematical techniques will be developed to assess diffusive and viscoelastic properties of physiological relevance over this entire mucus sample space, including strategies to resolve open mathematical questions about anomalous diffusion and nonlinear viscoelasticity.