Epithelial stem cells in Meibomian gland development and homeostasis

上皮干细胞在睑板腺发育和稳态中的作用

• 批准号: 10341666
• 负责人: Lu Le
• 金额: $ 41万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-30 至 2026-07-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10341666
• 关键词: Ablation; Acinus organ component; Address; Adult; Affect; Aging; Atrophic; Biological Process; Blindness; Capsid Proteins; Cells; Congenital Disorders; Contact Lenses; Cornea; Corneal Abrasion; Data; Development; Disease; Dropout; Dry Eye Syndromes; Duct (organ) structure; EGR2 gene; Embryo; Epithelial; Epithelial Cells; Excessive tearing; Eye; Eyelid structure; Genes; Genetic; Genetic Transcription; Gland; Hair; Hair follicle structure; Hair shaft structure; Homeostasis; Human; Inflammation; Knowledge; Label; Laboratories; Lead; Left; Life; Lipids; Lubrication; Mesenchyme; Modeling; Molecular; Morphogenesis; Morphology; Mus; Mutant Strains Mice; Oils; Pathway interactions; Persons; Pharmacotherapy; Physiological; Population; Pre-Clinical Model; Prevalence; Process; Proteins; Reporting; Research; Risk Factors; Role; Sebaceous Glands; Secondary to; Structural defect; System; Testing; base; clinical application; epithelial stem cell; evaporation; exhaustion; follow-up; gland development; in vivo; innovation; insight; keratinization; meibomian gland; meibomian gland dysfunction; mouse model; novel; ocular surface; postnatal; prevent; screening; stem cell biology; stem cell differentiation; stem cell population; stem cells; tool; transcription factor

Project Summary Dry eye disease (DED), which occurs when there is inadequate lubrication of the eyes due to insufficient tears or excessive tear evaporation, affects over 16 million adults in the U.S., and the prevalence continues to increase. If left untreated, DED can lead to serious problems including inflammation of the eye, corneal abrasions, and even vision loss. While DED can be due to a variety of causes, ~90% of cases are due to Meibomian gland dysfunction (MGD). The Meibomian glands (MGs) are holocrine sebaceous glands located in the eyelids. Differentiated meibocytes within the MGs secrete meibum, a mixture of lipids and proteins that coats the ocular surface and prevents tear evaporation. MGD can be due to reduced meibum secretion, resulting from abnormal MG activity, blockage of the MG orifice due to hyper-keratinization, or structural defects such as MG atrophy or dropout. Another possible cause of MGD is stem cell exhaustion, in which MG resident stem cells are unable to replenish meibocytes due to dysregulated stem cell differentiation. MG development is well-conserved in mice and humans. In mice, MGs begin to develop at embryonic day 18.5 from the ectodermal epithelium; the MG anlage grows out of the eyelid mesenchyme, elongates, branches, and differentiates into ductules that form the acini; one MG contains clusters of these secretory acini which contain the meibocytes. MGs are fully formed by postnatal day 15. Throughout life, meibocytes are replenished from a stem cell population within the acini. While MG morphological development has been well described, the identity of the stem cell population(s) that gives rise to the MG remains controversial. Additionally, the resident stem cell population responsible for replenishing meibocytes after holocrine secretion in mature MG has not been definitively identified. Previous studies indicate there is a limited number of precursor meibocytes, which may be the cause of stem cell exhaustion that can occur with aging. Thus, the stem cell origin(s) and molecular mechanisms underlying MG development and homeostasis, i.e. replacement of acinar meibocytes throughout life, remain major knowledge gaps in the field. A recent study from our laboratory identified Krox20 as a marker of a stem cell population in the hair follicle that differentiates into hair shaft progenitor cells in the hair matrix, and ultimately constitutes the structural component of the hair shaft (Liao, G&D, 2017). Follow-up preliminary studies revealed that a population of Krox20+ cells also gives rise to the MG and depletion of these Krox20+ cells or the KROX20 protein results in lack of MGs. These data highlight a critical role for Krox20 in MG development. We hypothesize that Krox20 marks a novel stem cell population that gives rise to the MG. Our objectives in this proposal are to investigate the role of these Krox20+ cells in MG morphogenesis and homeostasis, and delineate the mechanisms by which KROX20 exerts its biological function in MG. The identification, isolation, and study of this previously unidentified MG stem cell will provide insights that will advance the field, filling a current knowledge gap, as well as providing a novel murine model of MGD-based DED that offers a platform for testing potential therapies for DED.

项目摘要 干眼症(DED)，由于泪水不足导致眼睛润滑不足而发生 或过度的泪水蒸发，在美国影响着1600多万成年人，而且患病率还在继续上升。 如果不进行治疗，DED可能会导致严重的问题，包括眼部炎症、角膜擦伤和 甚至失明。虽然DED可以由多种原因引起，但约90%的病例是由于眉毛腺 功能障碍(MGD)。眉板腺(MG)是位于眼睑的全分泌性皮脂腺。 MG内分化的巨噬细胞分泌MEIBUM，这是一种包裹在眼球上的脂质和蛋白质的混合物 并防止泪水蒸发。MGD可归因于糖胺分泌减少，由异常引起 MG活性，由于过度角化导致MG口堵塞，或结构缺陷，如MG萎缩或 辍学。MGD的另一个可能原因是干细胞耗尽，MG常驻干细胞无法 补充因干细胞分化失调所致的巨噬细胞。镁的发育在小鼠中保存得很好 和人类。在小鼠中，MGs在胚胎18.5天开始从外胚层上皮发育； 原生组织从眼皮间充质中长出，伸长，分枝，并分化成小导管，形成 腺泡；一个MG含有成簇的分泌性腺泡，这些腺泡含有小细胞。MGS完全由以下组成 出生后第15天。在整个生命过程中，巨噬细胞都是从腺泡内的干细胞群中补充过来的。而当 MG的形态发育已经被很好地描述了，干细胞群体的身份(S)给了 崛起为MG仍存在争议。此外，负责补充的常驻干细胞种群 成熟MG患者全分泌后的巨噬细胞尚未得到明确的鉴定。先前的研究表明 前体巨噬细胞数量有限，这可能是干细胞耗尽的原因，可以 随着年龄的增长而发生。因此，干细胞起源(S)和分子机制的基础上MG的发展和 动态平衡，即整个生命周期中腺泡巨噬细胞的更替，仍然是该领域的主要知识空白。 我们实验室最近的一项研究确定Krox20是毛囊中干细胞数量的标志 在毛发基质中分化为毛干前体细胞，并最终构成结构 毛轴的部件(廖，G&D，2017)。后续的初步研究显示， Krox20+细胞也会引起MG，这些Krox20+细胞或KROX20蛋白的耗尽会导致 缺少MGs。这些数据突显了Krox20在MG开发中的关键作用。我们假设Krox20 标志着一种新的干细胞群体，它产生了MG。我们在这份提案中的目标是调查 这些Krox20+细胞在MG形态发生和动态平衡中的作用，并描述了其机制 KROX20在MG中发挥其生物学功能。鉴定、分离和研究以前未被确认的这种生物 镁干细胞将提供推动该领域发展的见解，填补目前的知识空白，并提供 一种新的基于MGD的DED小鼠模型，为测试DED的潜在治疗方法提供了一个平台。