Cellular and molecular mechanisms of hair follicle dermal papilla formation

描述（由申请人提供）：组织稳态对于维持器官完整性和功能至关重要，但这些过程的分子机制和细胞动力学尚未明确。对于在整个生命过程中不断更新的器官系统，多能“成体干细胞”的储存库根据需要自我更新和分化，以产生组成每个复杂组织的单独细胞类型。这些多能细胞通过周围微环境或“小生境细胞”传递的信号来维持。毛囊代表了一个很好的模型系统，在其中探索驱动干细胞和小生境细胞的特化和维持的分子机制，因为在胚胎发育期间形成的毛囊在几十年的生命中自然地循环通过多个阶段的退化和再生长。当毛囊不能循环并进入休眠状态时，毛干的产生停止，脱发加剧。毛囊生产力的这种下降可作为正常衰老的结果或作为皮肤病或全身性疾病的后遗症而发生，但不管潜在的问题是什么，导致脱发的形态学和分子变化通常是不明确的，并且几乎没有有效的药理学疗法可用。由于干细胞和小生境细胞群之间的相互作用驱动卵泡循环，任何一个区室的破坏都会导致卵泡衰老。更好地理解在毛发形态发生和循环期间在生态位隔室中发生的动态分子和细胞变化将揭示用于治疗年龄或疾病相关脱发的治疗靶点，并且更广泛地提供对驱动其他持续补充组织中的持续组织稳态的因素的洞察。 该提案旨在探索毛囊内毛乳头形成和维持的细胞动力学和分子机制，其中这些间充质细胞提供关键的生态位信号以支持上皮干细胞。我会利用命运地图技术 采用新的生态位特异性遗传工具，以跟踪单细胞在形态发生和通过第一个头发周期，以表征如何毛囊间充质形成和检测多能生态位祖细胞。我将进一步使用BrdU脉冲/追踪标记来定义卵泡形成与周期过程中龛细胞的增殖状态。最后，利用已建立的转基因报告小鼠分离毛乳头细胞、毛鞘细胞及其胚胎前体细胞。然后，我将严格分析这些样本的全球基因表达谱，以定义一组新生和活跃生长卵泡中不同间充质群体的特征基因。这将确定关键的分子特征，这些特征对于建立和维持功能性生态位具有内在重要性， 提供促进毛囊生产力的信号。该提案的优势在于使用独特的小鼠工具来靶向毛囊内的间充质小生境细胞的创新，以及为未来临床应用产生可翻译结果的潜力。

DESCRIPTION (provided by applicant): Tissue homeostasis is crucial to maintain organ integrity and function, but the molecular mechanisms and cellular dynamics underlying these processes are not yet well-defined. For organ systems that are continuously renewing throughout life, reservoirs of multipotent "adult stem cells" self-renew and differentiate as needed to produce the separate cell types that compose each complex tissue. These multipotent cells are maintained by signals imparted from the surrounding microenvironment or "niche cells". The hair follicle represents an excellent model system in which to explore the molecular mechanisms driving the specification and maintenance of both stem and niche cells, since follicles that are formed during embryogenesis naturally cycle through multiple phases of degeneration and re-growth over decades of life. When follicles fail to cycle and become dormant, hair shaft production ceases and hair loss ensues. Such a decline in follicle productivity can occur as a consequence of normal aging or as a sequela of dermatological or systemic disease, but regardless of the underlying problem, the morphological and molecular changes leading to hair loss are generally ill- defined and there are few effective pharmacological therapies available. As interactions between the stem cell and niche cell populations drive follicle cycling, the breakdown of either compartment leads to follicle senescence. A better understanding of the dynamic molecular and cellular changes that occur in the niche compartment during hair morphogenesis and cycling will reveal therapeutic targets for treating age- or disease- associated hair loss and more broadly provide insight into the factors that drive continued tissue homeostasis in other continuously replenishing tissues. This proposal aims to explore the cellular dynamics and molecular mechanisms of dermal papilla formation and maintenance within the hair follicle, where these mesenchymal cells provide crucial niche signals to support epithelial stem cells. I will utilize fate mapping techniques that employ novel niche-specific genetic tools to trace single cells during morphogenesis and through the first hair cycle, in order to characterize how the hair follicle mesenchyme forms and to detect multipotent niche progenitor cells. I will further use BrdU pulse/chase labeling to defin the proliferative status of niche cells during follicle formation versus cycling. Finally I will islate dermal papilla cells, related dermal sheath cells and their embryonic precursors using established transgenic reporter mice. I will then rigorously analyze global gene expression profiles of these samples in order to define a set of signature genes for distinct mesenchymal populations in nascent and actively growing follicles. This will identify key molecular features that are intrinsically important for establishing and maintaining a functional niche, which in turn supplies signals to promote hair follicle productivity. The strengths of this proposal lie in the innovation of using unique mouse tools to target mesenchymal niche cells within the hair follicle, and the potential to generate translatable findings for future clinical application.