Cellular and molecular mechanisms of hair follicle dermal papilla formation

描述(申请人提供)：组织动态平衡对维持器官的完整性和功能至关重要，但这些过程背后的分子机制和细胞动力学还没有很好的定义。对于在整个生命过程中不断更新的器官系统，多潜能“成体干细胞”的储存库会根据需要自我更新和分化，以产生组成每个复杂组织的不同类型的细胞。这些多能细胞由周围微环境或“小生境细胞”传递的信号维持。毛囊是一个很好的模型系统，可以用来探索驱动干细胞和壁龛细胞规范和维持的分子机制，因为在胚胎发育过程中形成的毛囊在几十年的生命中自然经历了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，继而发生脱发。毛囊生产力的下降可能是正常衰老的结果，也可能是皮肤病或全身疾病的后遗症，但无论潜在的问题是什么，导致脱发的形态和分子变化通常都是模糊的，而且几乎没有有效的药物治疗方法可用。由于干细胞和生态位细胞群体之间的相互作用推动了卵泡的循环，其中任何一个隔室的破坏都会导致卵泡衰老。更好地了解毛发形态发生和周期过程中壁龛内发生的动态分子和细胞变化，将揭示治疗年龄或疾病相关脱发的治疗目标，并更广泛地洞察推动其他持续补充组织中持续组织动态平衡的因素。这项建议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，毛囊中的间充质细胞为支持上皮干细胞提供关键的利基信号。我将利用命运映射技术 使用新的生态位特定的遗传工具，在形态发生期间和第一个毛发周期跟踪单个细胞，以表征毛囊间充质是如何形成的，并检测多潜能的生态位祖细胞。我将进一步使用BrdU脉冲/Chase标记来确定卵泡形成过程中与周期过程中利基细胞的增殖状态。最后，我将iSlate毛乳头细胞、相关真皮鞘细胞及其胚胎前体细胞用已建立的转基因报告小鼠。然后，我将严格分析这些样本的全球基因表达谱，以便为新生和活跃生长的毛囊中不同的间充质群体定义一组标志性基因。这将确定对建立和维持功能生态位具有内在重要性的关键分子特征，这反过来又 提供促进毛囊生产力的信号。这一建议的优势在于创新地使用独特的鼠标工具来定位毛囊内的间充质细胞，并有可能产生可翻译的结果用于未来的临床应用。

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.