Mechanisms that Regulate Thymic Involution and Age-Assoc

免疫系统老化的后果之一是胸腺退化。由于胸腺上皮萎缩和胸腺功能减少，胸腺的结构发生了深刻的变化，胸腺的大小逐渐减小。这种下降是系统性的，随之而来的是循环初始T细胞和细胞介导的免疫反应数量的减少，这可能在衰老宿主中观察到的肿瘤发生、自身免疫和传染病的增加中发挥作用。尽管对胸腺衰老的病理生理进行了广泛的研究，但参与衰老过程的精确分子机制仍不清楚。为了研究衰老胸腺中发生的分子变化，使用从不同年龄小鼠胸腺分离的RNA进行了微阵列分析。利用来自2、4、6、12和18月龄BALB/c小鼠胸腺的mRNA，使用我们实验室开发的三种不同的定制cDNA微阵列以及22K寡核苷酸小鼠阵列进行微阵列分析。这个项目的成功依赖于来自确定的衰老来源的衰老细胞的分子谱分析的可靠性，包括来自培养和新分离的衰老细胞。第一个里程碑将是胸腺退化相关基因的明确表征和选择。我们对不同年龄的小鼠胸腺和脾脏的基因表达进行了一系列分析，并开始研究不同H-2和遗传背景的小鼠以及已知的老年性小鼠模型的表达差异。我们目前的数据表明，胸腺退化可能与压力和性别有关，可能部分与不同的营养和压力相关因素有关，而不仅仅是衰老。许多与DNA修复、氧化应激、细胞凋亡和炎症相关的基因被发现随着胸腺衰老而显著上调。我们目前正在分析老龄小鼠的脾脏、胸腺、骨髓、免疫细胞亚群和胸腺细胞的基因谱，这些基因谱来自不同年龄的小鼠，给予自由或热量限制饮食，以及注入生长激素、饥饿素、瘦素和白细胞介素-7的老龄小鼠。我们最近发现，胃促生长素和瘦素输注可以逆转与年龄相关的胸腺退化。对这些处理过的小鼠胸腺进行阵列分析，可能会对涉及胸腺再生的常见分子过程产生有价值的数据。目前尚不清楚某些淋巴器官或细胞成分是否在长寿和寿命中起关键作用。该项目的总体目标是在衰老过程中产生胸腺、脾脏和淋巴结的全面基因表达谱，以确定在这些不同器官系统中以年龄依赖方式表达的独特和常见基因以及功能相关的基因群。我们最初的研究重点是胸腺，因为它的退化被认为是解决与衰老相关的免疫缺陷最重要的障碍之一。

One of the consequences of an aging immune system is the process of thymic involution. The thymus undergoes a progressive reduction in size due to profound changes in its architecture associated with thymic epithelia atrophy and decreased thymopoiesis. This decline is systemically followed by decreased numbers of circulating naive T cells and cell-mediated immune responses which may play a role in the increased tumorigenesis, autoimmunity, and infectious diseases observed within an aging host. Despite the extensive study of the pathophysiology of the aging thymus, the precise molecular mechanism involved in the involution process remains unclear. In an effort to profile molecular changes that occur within the aging thymus, microarray analysis was performed using RNA derived from thymus isolated from mice of varying ages. Using mRNA derived from the thymi of 2, 4, 6, 12 and 18 month old BALB/c mice, microarray analysis was performed using three distinct custom-made cDNA microarrays developed within our laboratory as well as 22K oligonucleotide murine arrays. The success of this project relies upon the reliability of the molecular profiling aged cells from defined aged sources, both from culture and freshly isolated aged cells. The first milestone will be the definitive characterization and selection of genes associated with thymic involution. We have performed a series analysis of gene expression in the thymi and spleens of mice of varying ages and have initiated studies examining expression differences in mice of distinct H-2 and genetic backgrounds as well as known involution mouse models. Our current data would suggest that thymic involution may be strain- and gender-dependent and may in part be associated with distinct nutritional and stress-related factors rather than simply aging. A number of genes associated with DNA repair, oxidative stress, apoptosis, and inflammation were found to be significantly upregulated with thymic aging. We are currently analyzing the data obtained from the gene profiles of aged spleens, thymi, bone marrow, immune cell subsets and thymocytes from mice of various ages given ad libitum or caloric restricted diets as well as from aged mice infused with GH, ghrelin, leptin and interleukin-7. We have recently found that ghrelin and leptin infusions reverse age-associated thymic involution. Array analysis of the thymi of such treated mice may yield valuable data on the common molecular processes involved in thymic regeneration. It is unclear whether certain lymphoid organs or cellular components play a critical role in longevity and lifespan. The overall goal of this project is to produce a comprehensive gene expression profile in the thymus, spleen, and lymph nodes during the aging process to identify unique and common genes and functionally related groups of genes that are expressed in age-dependent manner in these different organ systems. We have initially focused our efforts on the thymus, as its involution is believed to be one of the most significant obstacles to overcome in addressing the immunological deficits associated with aging.