Langerhans细胞不同亚群在特应性皮炎中的作用及机制研究

Skin barrier dysfucntions, abberrant immune responses and environmental stimulations are the key contributors to the onset of atopic dermatitis (AD). Langerhans Cells (LC), specialized dendritic cells (DCs) in the epidermis of skin, connect the above major contributors and play important roles in the pathogenesis of AD. However, the precise roles and mechanism of LC in AD are not clear yet. It has been proved that LC participate in the epicutaneous immunization of AD by eliciating Th2 immune responses; whereas we and other groups discovered that LC also mediate skin tolerance and maintain the skin homeostasis. Currently the mechanism of skin-immunization versus skin-tolerance mediated by LC is the focus of extensive investigation. We hypothesize that the pro-inflammation and pro-tolerance functions of LC are carried out by two different LC subsets, monocyte-derived LC (moLC) and tissue-resident LC (cLC), which pursue pro-inflammation and pro-tolerance function in the inflammatory and steady state of skin respectively, and Notch signaling pathway might play important roles in the process of LC differentiation or immunization/tolerance induction. In the present proposal, we plan to analyze the role and mechanism of LC subsets in the pathogenesis of AD by ultilizing LC conditional knockout mice, based on our previous studies. We also plan to use mice deficient in molecules of Notch signaling pathway, and explore the function of Notch signaling in the development and function of LC. This study will further our understanding of the pathogenesis of AD, and place a foundation for the future targeting theray for AD.

特应性皮炎(AD)的发病机制包括皮肤屏障功能改变、免疫应答异常、环境因素刺激等，位于表皮的Langerhnas细胞(LC)是联系上述关键因素的纽带，在AD发病中居于核心地位，但确切的作用和机制尚不明确。一般认为LC参与AD经皮致敏并诱导Th2免疫应答，而我们和其他学者发现LC介导经皮免疫耐受。LC致免疫应答或致免疫耐受功能的调控机制是目前关注的焦点。我们提出假说认为LC的致耐受和致免疫功能由LC不同亚群——组织定居LC(cLC)和单核细胞来源LC(moLC)分别承担，Notch信号途径在调控LC两亚群的分化和功能中发挥关键作用。本研究拟在以往工作基础上，利用LC选择性标记模式小鼠进一步确认LC两亚群，深入分析LC不同亚群在AD炎症中的作用及机制，进一步利用条件性缺失Notch信号的小鼠，研究Notch信号途径在LC分化及功能中的作用，有望阐明LC在AD中的作用及机制、揭示AD治疗的新策略。

特应性皮炎(atopic dermatitis, AD)的发病机制包括皮肤屏障功能改变、免疫应答异常、皮肤菌群紊乱等，位于表皮的Langerhnas细胞(Langerhans cells, LC)是联系上述关键因素的纽带，在AD发病中居于核心地位，但确切的作用和机制尚不明确。一般认为LC参与AD经皮致敏并诱导Th2免疫应答，而我们和其他学者发现LC介导经皮免疫耐受。LC致免疫应答或致免疫耐受功能的调控机制是目前关注的焦点。我们提出假说认为LC的致耐受和致免疫功能由LC不同亚群——组织定居LC(cLC)和单核细胞来源LC(moLC)分别承担。我们应用Rosa报告小鼠与Lyz2-cre小鼠发现静息状态下表皮内LC分为MoLC和cLC两群；制备皮肤炎症后MoLC数量迅速增加，进一步证实了MoLC的存在。利用LC组成性缺失的Langerin-DTA小鼠，与WT小鼠进行交叉骨髓移植，建立只含有MoLC或cLC的小鼠模型，制备皮肤炎症模型后发现单纯缺失cLC小鼠皮肤炎症最重，缺失MoLC小鼠炎症最轻，提示cLC发挥负向免疫调节功能，而MoLC发挥促炎作用。将Lyz2-cre小鼠与RBP-Jf/-小鼠交配，获得Lyz2-cre/RBP-Jf/f小鼠，发现该小鼠的LC数量减少，表明Notch信号途径参与moLC发育；将Lyz2-cre/RBP-Jf/f小鼠骨髓移植给Langerin-DTA小鼠，发现受体小鼠表皮LC的数量显著低于对照移植小鼠，进一步支持Notch信号途径调控moLC发育。采用单细胞测序技术分析了人表皮LC的亚群，发现人表皮CD207+LC分为CD207hiCD1ahi (LC1)和CD207medCD1aloCD1b+CD1c+(LC2)的两个亚群，流式细胞仪分析证实这两个亚群的表型，并且包皮、躯干和头皮等不同部位皮肤都有这两群细胞存在；功能预测显示LC1特征性表达代谢和免疫稳定基因，LC2表达免疫应答基因。本项目首次揭示了小鼠和人LC的两个亚群，并初步揭示了其功能作用，为下一步有针对性地调控LC亚群的功能、治疗AD等炎症性皮肤病奠定了基础。

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