Role of pro-oxidative connective tissue in skin aging – Molecular mechanisms and therapeutic strategies

为了了解成纤维细胞在器官衰老和组织衰退中的作用，我们将分析我们早期生成的描述增强衰老的结缔组织特异性小鼠模型，并将其与固有衰老的对照小鼠进行比较。先前建立的小鼠衰老模型与结缔组织特异性缺失的锰超氧化物歧化酶（SOD 2）揭示伴随上调p16 INK 4A，细胞周期抑制剂促进不可逆的成纤维细胞衰老，和胰岛素样生长因子1（IGF-1），一个重要的生长和组织维持因子的深刻下降。IGF-1的抑制释放构成衰老成纤维细胞的衰老相关分泌表型（SASP）的关键标志。这种老化程序的安装会导致严重的结缔组织老化和整体皮肤老化。我们实验室的间接证据表明，氧化还原依赖性转录因子伴随诱导p16 INK 4A，同时抑制IGF-1。我们在这里将遵循两个主要的相互关联的目标：1。建立氧化还原敏感性转录因子JunB/AP 1在皮肤老化中的作用，并阐明其在组织衰退中的作用模式，以及2.以评估具有降低的衰老成纤维细胞去除能力的先天免疫系统的细胞是否是衰老成纤维细胞在老年小鼠皮肤中进一步积累的原因。这两个研究热点是密切相关的，都有助于更好地理解增强积累的衰老细胞在结缔组织丰富的器官。使用结缔组织特异性双Sod 2/JunB缺陷小鼠，我们将剖析氧化还原依赖性JunB是否是皮肤老化的原因，以及这是否取决于IGF-1抑制的选择性翻译。通过缺乏自然杀伤细胞（NK细胞）或巨噬细胞的遗传操作的小鼠模型，我们将探索衰老细胞是否在结缔组织丰富的器官如皮肤中积累。此外，我们将采用策略，如年轻NK细胞/巨噬细胞（骨髓）和天然IgM的过继转移，以更有效地去除衰老细胞，并将研究SASP的重编程将减弱甚至恢复延迟衰老和皮肤稳态的可能性，包括干细胞更新和增强再生能力。该项目将有助于确定成纤维细胞衰老对皮肤衰老以及其他结缔组织丰富的器官（如骨骼和肌肉）的核心作用。预期的结果将为器官和有机体衰老/组织衰退的适当干预措施的发展带来前所未有的希望。

To understand the role of fibroblasts in organ aging and tissue decline, we will analyze our earlier generated connective tissue specific murine model depicting enhanced aging and compare it to intrinsically aged control mice. The previously established murine aging model with a connective tissue specific deletion of the manganese superoxide dismutase (SOD2) revealed concomitant up-regulation of p16INK4A, a cell cycle inhibitor promoting irreversible fibroblasts senescence, and a profound decline of Insulin-like Growth Factor 1 (IGF-1), an important growth and tissue maintenance factor. Suppressed release of IGF-1 constitutes a key hallmark of the senescence-associated secretory phenotype (SASP) of senescent fibroblasts. The installment of such an aging program enforces severe connective tissue aging and overall skin aging. Indirect evidence of our laboratory suggests that a redox-dependent transcription factor concomitantly induces p16INK4A, while suppressing IGF-1. We here will follow two main interconnected objectives: 1. to establish the role of the redox sensitive transcription factor JunB/AP1 in skin aging and to unravel its mode of action in tissue decline, and 2. to assess whether cells of the innate immune system with reduced removal capacity of senescent fibroblasts are responsible for further accumulation of senescent fibroblasts in the skin of aged mice. These two research foci are intimately interrelated, and both contribute to a better understanding of enhanced accumulation of senescent cells in connective tissue rich organs. Using connective tissue specific double Sod2/JunB deficient mice, we will dissect whether redox-dependent JunB is responsible for skin aging and whether this depends on selective translation with suppression of IGF-1. By means of genetically manipulated murine models which lack natural killer cells (NK cells) or macrophages, we will explore whether senescent cells accumulate in connective tissue rich organ like skin. In addition, we will employ strategies, like adoptive transfer of young NK cells/macrophages (bone marrow) and natural IgM to more efficiently remove senescent cells and will study the likely possibility that reprogramming of the SASP will attenuate or even restore delayed aging and skin homoeostasis including stem cell renewal and enhanced regenerative capacity. This project will help to define the central role of fibroblast senescence on skin aging, and on other connective tissue rich organs, such as bone and muscle. The expected results will hold unprecedented promise for the development of appropriate interventions for organ and organismal aging/tissue decline.