Physiological Role of Dedifferentiating Dermal Adipose Tissue

摘要 去分化真皮脂肪组织的生理作用 脂肪组织纤维化是功能失调脂肪组织的重要组成部分。这种纤维化会产生有害的影响 除了启动全身适应不良外，对脂肪组织内局部代谢反应的影响 回应。脂肪组织纤维化的确切原因(S)仍然存在争议，因此 定义得很清楚。在这里，我们的目标是关注“真皮脂肪组织纤维化”，主要是因为它容易患上 可访问性，2)我们为专门检查真皮而建立的新的遗传小鼠模型 脂肪组织功能障碍和，3)我们的初步观察发现广泛的真皮脂肪细胞 分化和去分化。我们认为，后一种进程是 脂肪组织纤维化的病理之路。真皮脂肪组织是直接定位于皮肤的脂肪 在网状真皮下。与其他定义明确的脂肪垫相比，真皮脂肪组织显示出更高的 可塑性程度。在各种生理条件下，真皮脂肪组织具有 要么在当地迅速扩张，要么减少其规模。我们在体内的初步研究表明，真皮 脂肪组织与皮肤成纤维细胞中胶原的产生呈负相关。更重要的是， 我们实验室最近的研究证实，皮肤脂肪细胞的高度动态性质使它们 1)去分化为前脂肪细胞或2)转化为α-SMA阳性的肌成纤维细胞 (在博莱霉素诱导的纤维化模型中进行检查时)。在这里，我们建议检查以下内容 假设：脂肪细胞本身是预防脂肪组织纤维化的主要参与者。 对高脂饮食或博莱霉素诱导的代谢挑战的反应。我们将解决我们的 三个具体目标的假设：i)我们将通过异位或异位方式将脂肪细胞保留在完全分化的状态 使皮肤脂肪细胞暴露于PPARγ激动剂。同时，我们的目标是通过基因过量表达PPARGamma，然后 评估对纤维化反应的影响。除此之外，我们还将研究一个完整的 消除脂肪细胞对皮肤局部纤维化反应的影响。Ii)通过血统追溯，我们的目标是 在成熟脂肪细胞去分化为前脂肪细胞时对其进行基因标记和跟踪。其中一些前- 脂肪细胞可以转化为肌成纤维细胞。我们已经开发出一种基因方法来选择性地消除 起源于成熟脂肪细胞的肌成纤维细胞。这将使我们第一次能够检查 脂肪细胞来源的肌成纤维细胞与脂肪组织纤维化反应的功能相关性。 Iii)通过新开发的“分离CRE”系统，我们利用了双推广器系统，以确保 在真皮脂肪细胞中唯一表达。我们将在局部控制瘦素和脂联素水平，然后 阐述局部脂肪因子在皮肤脂肪组织微环境中的作用对 纤维化反应。虽然我们专注于真皮脂肪组织，但拟议研究的结果也将 对理解其他脂肪库中的纤维化反应有深远的影响。

Abstract Physiological Role of De-differentiating Dermal Adipose Tissue Adipose tissue fibrosis is an integral component of dysfunctional fat tissue. This fibrosis exerts detrimental effects on local metabolic responses within adipose tissue, in addition to initiating maladaptive systemic responses. The exact cause(s) of fibrosis in adipose tissue are still a matter of debate and as such, are not well defined. Here, we aim to focus on “dermal adipose tissue fibrosis”, primarily due to its 1) ease of accessibility, 2) our new genetic mouse models that we generated to specifically examine dermal adipose tissue dysfunction and, 3) our initial observation that identified extensive dermal adipocyte differentiation and de-differentiation. We believe that the latter processes are a key aspect of the pathological road to adipose tissue fibrosis. Dermal adipose tissue is skin-associated fat located directly under the reticular dermis. Compared to other well-defined fat pads, dermal adipose tissue displays a high degree of plasticity. Under a variety of physiological conditions, dermal adipose tissue has the capacity to either rapidly and locally expand, or reduce its volume. Our in vivo preliminary studies showed that dermal adipose tissue is negatively associated with collagen production in skin fibroblasts. Importantly, more recent studies in our laboratory identified that the highly dynamic nature of dermal adipocytes allows them to 1) undergo de-differentiation into pre-adipocytes or, 2) convert into alpha-SMA-positive myofibroblasts (when examined in a bleomycin-induced fibrosis model). Here, we propose to examine the following hypothesis: that the adipocyte itself is the major player in preventing adipose tissue fibrosis in response to a metabolic challenge of high fat diet feeding, or bleomycin induction. We will address our hypothesis in three Specific Aims: I) We will retain fat cells in a fully differentiated state, by either ectopically exposing dermal adipocytes to PPARgamma agonists. In parallel, we aim to genetically overexpress PPARgamma then assess the impact on the fibrotic response. In addition to this, we will examine the impact of a complete elimination of adipocytes upon the local fibrotic response in the skin. II) Through lineage tracing, we aim to genetically label and track mature adipocytes as they de-differentiate into pre-adipocytes. Some of these pre- adipocytes can convert to myofibroblasts. We have developed a genetic approach to selectively eliminate myofibroblasts that originate from mature adipocytes. This will allow us, for the first time, to examine the functional relevance of these adipocyte-derived myofibroblasts towards the fibrotic response in adipose tissue. III) With a newly developed “Split Cre” system, we take advantage of a dual promoter system that ensures expression uniquely in the dermal adipocyte. We will manipulate leptin and adiponectin levels locally, then address the impact of local adipokine action in the microenvironment of the dermal adipose tissue on the fibrotic response. While we focus on dermal adipose tissue, results from the proposed studies will also have a profound impact on the understanding of the fibrotic response in other fat depots.