Epithelial Stem Cell Migration during Wound Repair

描述（由申请人提供）：皮肤表皮受伤后，必须立即进行修复机制，恢复其屏障功能，以防止脱水和有害病原体的入侵。皮肤表皮的创面修复涉及角质形成细胞的活化、迁移、增殖和分化。特别是，受伤区域的再上皮化需要皮肤上皮干细胞，这些干细胞可以从周围表皮和毛囊中迁移。然而，对于激活干细胞迁移的信号和在伤口修复过程中指导其迁移的分子机制知之甚少。毛囊干细胞如何对伤口信号作出反应？在伤口修复过程中，引导干细胞迁移的信号通路是什么？哪一群上皮干细胞负责修复表皮和生成新的毛囊？在本研究计划中，我建议：(1)鉴定毛囊内有助于伤口修复的细胞；(2)纯化和鉴定毛囊内有助于伤口修复的细胞；(3)监测和表征细胞在伤口修复过程中的迁移；(4)对创伤修复过程中可能参与细胞迁移和再上皮化的分子进行功能研究。我计划开发小鼠模型，允许在伤口愈合过程中对皮肤干细胞及其后代进行谱系追踪。这使得表征和分离有助于伤口修复和新毛囊生成的皮肤干细胞成为可能。将进行全基因组基因谱分析，以检查基因表达的变化，并确定可能参与皮肤干细胞迁移的分子和信号通路。我将进行进一步的功能分析，以验证候选分子在迁移过程中的参与。本研究计划的发现将有助于我们了解皮肤干细胞损伤后迁移的分子机制，并为干细胞领域的许多基本问题提供答案。

DESCRIPTION (provided by applicant): Upon injury, the skin epidermis must undergo immediate repair mechanism to restore its barrier function to prevent dehydration and invasion of harmful pathogens. Wound repair of the skin epidermis involves activation, migration, proliferation, and differentiation of keratinocytes. In particular, the re-epithelialization of the wounded area requires skin epithelial stem cells, which migrate in both from the surrounding epidermis and also from the hair follicle. However, very little is known about the signals that activate stem cell migration and the molecular mechanisms directing their migration during wound repair. How do hair follicle stem cells respond to wound signals? What are the signaling pathways that direct stem cell migration during wound repair? Which population(s) of epithelial stem cells is responsible for repairing the epidermis and generation of new hair follicles? In this research plan, I propose to: (1) Identify the cells within the hair follicle that contribute to wound repair; (2) Purify and characterize the cells within the hair follicle that contribute to wound repair; (3) Monitor and characterize cells as they migrate during wound repair; and (4) Perform functional studies on molecules that may be involved in cell migration and re-epithelialization during wound repair. I plan to exploit mouse models that allow lineage tracing of skin stem cells and their progeny during the process of wound healing. This enables characterization and isolation of skin stem cells that contribute to wound repair and generation of new hair follicles. A genome-wide gene profiling will be conducted to examine the changes in gene expression, and to identify molecules and signal pathways that may be involved in migration of the skin stem cells. I will perform further functional assays to validate the participation of the candidate molecules in the migration process. Findings from this research plan will contribute to our understanding of the molecular mechanism of skin stem cell migration upon injury and provide answers to many fundamental questions in the stem cell field. PUBLIC HEALTH RELEVANCE: The main focus of this research proposal is to understand the molecular mechanisms involved in the activation and migration of epithelial stem cells during wound repair and to study the population(s) of stem cells in the hair follicles that may contribute to epidermis regeneration and new hair follicle formation at the wound sites. Since the molecular interactions between tumor and its microenvironment are similar to a wounding situation in many aspects, it is plausible to hypothesize that many of the same signals mobilizing skin stem cells to leave their original niche upon wounding may as well mobilize cancer stem cells and cause tumor metastasis. Thus, this proposed research is likely to provide insights on mechanisms of cancer progression, and the knowledge acquired from this research plan will advance our current understanding of how tissues heal wounds, as well as have implications for regenerative medicine.