Interdependence of lineages within the mammalian skin

项目摘要 哺乳动物皮肤中的一系列不同类型的细胞共同保护生物免受侮辱、感染和 脱水。最近的研究已经开始阐明不同类型的细胞之间的相互依存关系，以及 细胞间的交流对于发育和维护一个功能齐全的皮肤非常重要。头发 毛囊是表皮的重要附属物，在生长期和休止期之间循环。 (泰勒根)。毛囊细胞并不是再生皮肤和再生皮肤之间唯一不同的细胞类型： 在生长期进入后，真皮通过胚胎真皮成纤维细胞的增殖而显著增加。 以及出生后真皮脂肪层的扩张，导致皮肤更厚，更有弹性 特罗根皮肤。生长期皮肤也表现出比休止期皮肤更快的伤口愈合。尽管有这些已知的 然而，不同的是，在对信号通路和 导致这些变化的特定细胞间通讯。这一差距严重阻碍了 在各种领域进行有效的治疗干预，包括伤口修复、先天性皮肤疾病和 化疗或植皮后皮肤萎缩。过境放大细胞(TAC)是由长时间的 将干细胞称为产生下游后代的中间群体。毛囊TAC(HF-TACs) 是一个特定于生长期的群体。我们的初步数据表明，HF-TAC在这些过程中起着关键作用 生长期特异性皮肤通过一种涉及Sonic Hedgehog(SHH)的机制发生变化。总的目标是 本建议旨在阐明HF-TAC特异性SHH介导生长期特异性的细胞机制。 皮肤变化，并确定负责真皮增厚和更快的信号接收细胞 生长期皮肤的伤口愈合。我们的中心假设是SHH信号，通过钥匙运作 下游调节剂，光滑的，协调的变化，使生长期皮肤更厚，更有弹性， 而且愈合得更快。为了严格检验这一假说，我们将采用系统的活体方法进行检验。 敲除必需下游基因对皮肤不同细胞类型SHH信号的直接需求 并将这些突变体的表型与Shh基因敲除皮肤的表型进行比较。这个 检查的细胞类型包括毛囊、真皮成纤维细胞、成熟脂肪细胞和脂肪细胞 先驱物。我们将使用我们已经广泛验证的细胞类型特定的、可诱导的或构成的Cre系 表达方式和效果。我们期望这项提案中概述的实验将阐明 生理学上相关的途径，使生长期皮肤变厚和愈合更好。我们预料到 所获得的知识将确定关键细胞类型和/或信号，这些细胞和/或信号可能在治疗中被利用 病理情况。研究结果还可能确定TAC对细胞的新调节功能 周围的微环境，这可能会影响对其他系统中TAC的研究。

Project Summary A diverse array of cell types in mammalian skin together protects the organisms from insults, infection, and dehydration. Recent studies have begun to elucidate the interdependency of different cell types and the importance of cell-cell communication for the development and maintenance of a fully functional skin. Hair follicles, important appendages of the epidermis, cycle between a growth phase (anagen) and a rest phase (telogen). Hair follicle cells are not the only cell type that is different between an anagen and a telogen skin: upon anagen entry, the dermis increases significantly through proliferation of dermal fibroblasts embryonically and expansion of the dermal adipose layer postnatally, resulting in skin that is thicker and more resilient than telogen skin. Anagen skin also exhibits faster wound-healing than telogen skin. Despite these known differences, however, there remains a fundamental gap in understanding of the signaling pathways and specific cell-cell communications that lead to these changes. This gap poses a significant impediment to effective therapeutic intervention in a variety of areas including wound repair, congenital dermal disorders, and atrophic skin following chemotherapy or skin grafting. Transit-amplifying cells (TACs) are generated by long- term stem cells as an intermediate population that produce downstream progeny. Hair follicle TACs (HF-TACs) are an anagen-specific population. Our preliminary data indicate that HF-TACs play a key role in these anagen-specific skin changes through a mechanism involving Sonic Hedgehog (SHH). The overall objective of this proposal is to elucidate the cellular mechanisms by which HF-TAC-specific SHH mediates anagen-specific skin changes and to identify the signal-receiving cells that are responsible for dermal thickening and faster wound healing in anagen skin. Our central hypothesis is that the SHH signaling, operating through the key downstream mediator, Smoothened, orchestrates the changes that make anagen skin thicker, more resilient, and faster healing. To test this hypothesis rigorously, a systematic in vivo approach will be taken to examine the direct requirement of SHH signaling in different cell types in the skin by knocking-out essential downstream mediators of SHH and comparing the phenotypes of these mutants to phenotypes of Shh knockout skin. The cell types to be examined include hair follicles, dermal fibroblasts, mature adipocytes, and adipocyte precursors. We will use cell-type specific inducible or constitutive Cre lines that we have verified extensively for expression patterns and effectiveness. We expect that the experiments outlined in this proposal will elucidate a physiologically relevant pathway by which anagen skin becomes thicker and heals better. We anticipate that the knowledge gained will identify critical cell types and/or signals that might be harnessed therapeutically in pathological conditions. The results may also identify novel regulatory functions exerted by TACs on the surrounding microenvironment, which would likely impact studies of TACs in other systems.