Age-Related Meibomian Gland Dysfunction

描述（由申请人提供）：本项目的长期目标是了解年龄相关性睑板腺功能障碍（MGD）和蒸发性干眼的机制。最近，我们已经表明，小鼠和人的睑板腺经历特定的年龄相关的变化，包括减少腺泡细胞增殖，腺泡萎缩，和改变过氧化物酶体增殖物激活受体γ（PPARg）定位从年轻的细胞质囊泡/核在老年小鼠和人类的核。由于PPARg是一种脂质敏感的核受体，参与调节脂肪细胞和皮脂细胞分化和脂肪生成，我们的研究结果表明，PPARg可能参与调节衰老过程中的睑板腺分化。基于这些研究结果，我们认为睑板腺的老化可能导致PPARg的下调，从而导致睑板细胞分化和脂质合成减少、腺体萎缩和分泌不足的MGD。目前，关于PPARg在睑板腺功能中的作用的知识存在重大空白。为了验证这一假设，我们开发了新的成像和细胞培养系统，以评估腺体体积，脂质合成和PPARg的调节。使用非线性光学（NLO）显微镜和阵列断层扫描，我们体积重建小鼠睑板腺和测量总，细胞和脂质体积在年轻和年老的腺体。初步研究表明，老化的睑板腺萎缩涉及脂质体积的显著损失，这表明睑板细胞分化减少。此外，我们已经使用相干反斯托克斯拉曼光谱（汽车），以确定区域内的睑板腺脂质分布，并初步表明，有一个年龄相关的变化，成熟的睑板腺脂质从腺泡进入导管。此外，我们已经开发了一种SV 40永生化小鼠睑板细胞系，其合成脂质并表达PPARg。利用这些新工具，我们提出以下具体目标。（一）.通过定量小鼠和人睑板腺中的亚细胞定位、翻译后修饰和下游反应基因表达模式，确定PPARg定位和相关基因表达模式的年龄相关变化。(2)通过使用NLO显微镜和阵列断层扫描定量体积和脂质合成来确定衰老对睑板腺的影响，以体积重建睑板腺和汽车，以评估小鼠和人睑板腺的腺泡、小管和导管中存在的脂质组分的区域变化。(3)通过定量培养的小鼠睑板细胞中的亚细胞定位、翻译后修饰和下游反应基因表达模式，评估天然和合成PPARg配体对脂质合成的影响。(4)通过定量年轻和老年小鼠睑板腺中PPARg表达、睑板细胞增殖、腺体体积和脂质合成的变化来测量PPARg配体对体内睑板细胞分化的影响。 公共卫生相关性：眼睑相关的睑板腺功能障碍（MGD）是一种常见的眼睑疾病，在美国人群中具有39-50%的广泛患病率，并且是老年人群中蒸发性干眼病的主要原因。迄今为止，我们的研究表明，在人类和小鼠中与年龄相关的MGD涉及改变过氧化物酶体增殖物激活受体γ（PPARg）的定位。由于PPARg已知调节脂肪生成和皮脂细胞分化，因此了解其在年龄相关性MGD中的作用可提供蒸发性干眼的机制理解，并提出治疗人类MGD的新治疗策略。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand the mechanism of age-related meibomian gland dysfunction (MGD) and evaporative Dry Eye. Recently we have shown that mouse and human meibomian glands undergo specific age-related changes including decreased acinar cell proliferation, acinar atrophy, and altered peroxisome proliferator-activated receptor gamma (PPARg) localization from cytoplasmic-vesicluar/nuclear in young to nuclear in old mice and humans. Since PPARg is a lipid sensitive, nuclear receptor implicated in regulating adipocyte and sebocyte differentiation and lipogenesis, our findings suggest that PPARg may be involved in modulating meibomian gland differentiation during aging. Based on these findings we propose that aging of the meibomian gland may result in down-regulation of PPARg leading to decreased meibocyte differentiation and lipid synthesis, gland atrophy, and a hyposecretory MGD. Currently, there is a MAJOR GAP in knowledge regarding the role of PPARg in meibomian gland function. To test this hypothesis we have develop novel imaging and cell culture systems to assess gland volume, lipid synthesis and their regulation by PPARg. Using non-linear optical (NLO) microscopy and array tomography we have volumetrically reconstructed the mouse meibomian gland and measured total, cellular and lipid volumes in young and old glands. Preliminary studies suggest that atrophy of aging meibomian glands involves a marked loss in the lipid volume suggesting decreased meibocyte differentiation. Additionally, we have used coherent anti-stokes raman spectroscopy (CARS) to identify the regional lipid profiles within the meibomian gland and have tentatively shown that there is an age-related change in the maturation of meibomian gland lipids moving from the acini into the duct. Furthermore, we have developed an SV40 immortalized mouse meibocyte cell line that synthesizes lipids and expresses PPARg. Using these novel tools we propose the following Specific Aims. (1). Establish the age-related changes in PPARg localization and associated gene expression patterns by quantifying the subcellular localization, post-translational modification and downstream response gene expression patterns in the mouse and human meibomian gland. (2) Determine the effects of aging on the meibomian gland by quantifying the volume and lipid synthesis using NLO microscopy and array tomography to volumetrically reconstruct the meibomian gland and CARS to assess regional changes in lipid components present in the acini, ductule and duct of the mouse and human meibomian gland. (3) Assess the effects of natural and synthetic PPARg ligands on lipid synthesis by quantifying the subcellular localization, post- translational modification and downstream response gene expression patterns in cultured mouse meibocytes. (4) Measure the effect of PPARg ligands on meibocyte differentiation in vivo by quantifying the changes in PPARg expression, meibocyte proliferation, gland volume and lipid synthesis in young and old mouse meibomian glands. PUBLIC HEALTH RELEVANCE: Age-Related meibomian gland dysfunction (MGD) is a common eyelid disorder having a widespread prevalence of 39-50% in the US population and is a major cause of evaporative dry eye disease in the aging population. Our studies thus far suggest that age-related MGD in humans and mice involve altered peroxisome proliferator-activated receptor gamma (PPARg) localization. Since PPARg is known to regulate lipogenesis and sebocyte differentiation, understanding its role in age-related MGD may provide a mechanistic understanding of evaporative dry eye as well as suggest novel therapeutic strategies for treating human MGD.