The Hillock: A Newly Discovered Airway Epithelial Structure and its Relationship with Squamous Metaplasia

小丘：新发现的气道上皮结构及其与鳞状上皮化生的关系

• 批准号: 10665873
• 负责人: Chaim Zev Chernoff
• 金额: $ 3.81万
• 依托单位: HARVARD MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-30 至 2026-09-29
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10665873
• 关键词: Ablation; Adult; Alleles; Alveolus; Asthma; Atmosphere; Basal Cell; Biological Assay; Biology; Cells; Cellular Structures; Cervix Uteri; Chemicals; Chronic Obstructive Pulmonary Disease; Cystic Fibrosis; Cytokeratin; Data; Differentiation and Growth; Disease; Distal; Dominant-Negative Mutation; Environment; Epithelium; Gases; Genetic; Gland; Homeostasis; Human; Injury; Lesion; Lung; Maintenance; Malignant Squamous Cell Neoplasm; Mediating; Modeling; Molecular; Mus; Myoepithelial; Naphthalene; Natural regeneration; Nature; Oxygen; Pathologic; Pathway interactions; Population; Process; Proliferating; Pseudostratified Epithelium; Reagent; Renal pelvis; Reporting; Reproducibility; Reserve Stem Cell; Resistance; Retinoic Acid Receptor; Role; Signal Transduction; Smoking; Source; Squamous Cell Lung Carcinoma; Squamous Epithelium; Squamous Metaplasia; Structure; Sulfur Dioxide; Surface; Testing; Tissues; Tobacco smoke; Trachea; Tracheal Epithelium; Tretinoin; Vitamin A; Vitamin A Deficiency; Work; airway epithelium; airway regeneration; cell type; cigarette smoke; epithelial repair; epithelial stem cell; epithelium regeneration; inhibitor; injured airway; injury and repair; novel; premalignant; response; single-cell RNA sequencing; small molecule; stem cells

Abstract Four years ago, the Rajagopal lab identified the airway hillock, a novel murine airway epithelial structure of unknown function. Hillocks have since been reported in human airways, suggesting that they are evolutionarily conserved. Most of the airway is covered by pseudostratified epithelium, composed primarily of basal cells, secretory club cells, and ciliated cells. The hillock is distinguished from this epithelium in three major ways: (1) the presence of stratified-appearing layers of flat KRT13+ (a cytokeratin) cells which sit atop hillock basal stem cells (2) the lack of ciliated cells, and (3) the enhanced replication of the hillock basal stem cells. We have preliminary data demonstrating that the hillock is resistant to multiple forms of airway injury including naphthalene, a key component of tobacco smoke, and sulfur dioxide gas. We have evidence to suggest that hillocks serve as a source of reserve stem cells. The stratified nature of the hillock resembles the pathologic finding of squamous metaplasia that is also characteristically stratified, and which is thought to be a precursor of squamous lung cancer. Vitamin A deficiency represents a reproducible model of squamous metaplasia in the trachea, uterine cervix, and renal pelvis in mice and humans. In the setting of vitamin A deficiency, trachea develop flat non-ciliated cell clusters that express the classic hillock marker KRT13. I therefore hypothesize that hillocks are the previously unidentified source of squamous metaplasia. I will use genetic lineage tracing of different cell types including the hillock in the setting of vitamin A deficiency to determine the cell of origin of vitamin A deficiency-induced squamous metaplasia. Since retinoic acid (RA) is the active metabolite of vitamin A, I will define the role of RA on hillock expansion and differentiation. To investigate whether hillocks expand in response to RA deficiency, I will express a dominant negative allele of the RA receptor using a hillock specific lineage driver. I will also add RA and RA receptor inhibitor to regeneration assays to examine the effects of RA on hillock-mediated injury repair. Finally, I hypothesize that hillocks are the primary stem cell that re-epithelializes the airway post-injury. Indeed, previous work has shown a variety of cell populations capable of expanding to resurface the injured airway. Therefore, it is unclear if hillocks are required for efficient epithelial repair and if they are the primary reserve stem cell of the epithelium. To investigate this hypothesis, I will genetically ablate hillocks prior to naphthalene injury, a chemical found in cigarette smoke, to determine if hillocks are necessary for proper regeneration.

抽象的 四年前，拉贾戈帕尔实验室发现了气道小丘，这是一种新型的小鼠气道上皮结构 未知功能。此后在人类呼吸道中发现了小丘，这表明它们在进化上 保守的。大部分气道被假复层上​​皮覆盖，主要由基底细胞组成， 分泌棒细胞和纤毛细胞。小丘与上皮的区别主要体现在三个方面：(1) 位于小丘基底茎顶部的扁平 KRT13+（细胞角蛋白）细胞的分层出现层 细胞（2）缺乏纤毛细胞，（3）小丘基底干细胞的复制增强。我们有 初步数据表明，小丘能够抵抗多种形式的气道损伤，包括 萘（烟草烟雾的主要成分）和二氧化硫气体。我们有证据表明 小丘是储备干细胞的来源。小丘的分层性质类似于病理性的 发现鳞状上皮化生，其也具有特征性分层，并且被认为是以下现象的先兆： 鳞状肺癌。 维生素 A 缺乏代表气管、子宫颈、 以及小鼠和人类的肾盂。在维生素 A 缺乏的情况下，气管会发育出扁平的非纤毛细胞 表达经典小丘标记 KRT13 的簇。因此我推测小丘是以前的 来源不明的鳞状化生。我将使用不同细胞类型的遗传谱系追踪，包括 维生素A缺乏症中的小丘确定维生素A缺乏症引起的细胞起源 鳞状化生。由于视黄酸（RA）是维生素A的活性代谢物，我将定义RA的作用 关于小丘的扩张和分化。为了研究小丘是否因 RA 缺乏而扩大，我 将使用 Hillock 特异性谱系驱动程序表达 RA 受体的显性负等位基因。我也会添加 RA 和 RA 受体抑制剂再生测定，以检查 RA 对小丘介导损伤的影响 维修。 最后，我假设小丘是损伤后使气道上皮重新形成的主要干细胞。的确， 之前的研究表明，多种细胞群能够扩张以重塑受损气道的表面。 因此，尚不清楚小丘是否是有效上皮修复所必需的以及它们是否是主要储备 上皮干细胞。为了研究这个假设，我将在萘之前通过基因方式消融小丘 损伤是香烟烟雾中发现的一种化学物质，以确定小丘是否是正常再生所必需的。