Epigenetic regulation of stem cell senescence in aging

描述（由申请人提供）：美国85岁或以上的人口数量预计将在2000年至2050年间增加约4倍（www.census.gov）。衰老与包括胃肠道在内的大多数器官的功能下降有关。胃肠道中与便秘相关的变化包括胃食管反流增加、肠易激综合征、便秘和大便失禁，以及更微妙的功能障碍，如无法摄入大量食物。总之，这些变化对总体福祉、生活质量、保持独立的能力产生了负面影响，并构成了重大的医疗保健负担。胃肠道老化的机制仍不清楚。肠道功能由胃肠道中的许多细胞类型之间的动态相互作用控制，包括上皮细胞、免疫细胞、平滑肌细胞、神经元和神经胶质以及Cajal间质细胞（ICC）。直到最近，神经肌肉功能障碍被认为是由于肠神经系统和平滑肌的变性而导致的与年龄相关的GI问题的主要原因。然而，对肠道起搏细胞ICC的年龄相关变化知之甚少。在这里，我建议研究ICC损失由于ICC干细胞的衰老作为一个关键机制，有助于GI老化。我的中心假设是，控制干细胞自我更新的分子通路的表观遗传调节的变化是ICC干细胞衰老和随之而来的衰老中成熟ICC的丧失的原因。我的具体目标是测试新的假设，减少表观遗传控制Wnt表达的polycomb组转录辅阻遏物的基础ICC干细胞衰老。我将通过流式细胞术定量klotho小鼠（一种早衰模型）胃肌中的ICC和ICC前体。在两个已建立的ICC干细胞系中，我将研究基因表达和Wnt信号传导的作用及其通过polycomb蛋白质的表观遗传控制，使用实时RT-PCR，Western免疫印迹和RNA干扰。该项目的结果可能揭示新的治疗靶点，以恢复ICC干细胞并改善衰老中的GI健康。此外，这项研究将强调成体干细胞在衰老中的作用，并可能提供针对衰老表型和改善快速扩大的老年人口生活质量的策略。 公共卫生相关性：老年相关的胃肠道疾病，包括便秘、大便失禁、胃食管反流和食物摄入量减少，在老年人中经常发生，并构成重大的医疗保健负担。在这里，我建议研究衰老的干细胞间质细胞的卡哈尔，细胞类型的关键胃肠动力，作为一种机制，胃肠老化。这项研究的结果可能会发现恢复老年人胃肠道功能的新工具，并可能导致新的疗法来减缓或管理衰老的一般影响。

DESCRIPTION (provided by applicant): The number of people in the US aged 85 or older is expected to increase ~4-fold between 2000 and 2050 (www.census.gov). Aging is associated with a decline decline in the function of most organs including the gastrointestinal (GI) tract. Age-related changes in the GI tract include increased gastroesophageal reflux, irritable bowel syndrome, constipation and fecal incontinence, as well as more subtle dysfunctions such as inability to consume large volumes of food. Together, these changes negatively affect general well-being, quality of life, the ability to maintain independence, and represent a significant health care burden. The mechanisms of GI aging remain obscure. Gut function is governed by a dynamic interaction between the many cell types in the GI tract including epithelial cells, immune cells, smooth muscle cells, neurons and glia, and interstitial cells of Cajal (ICC). Until recently, neuromuscular dysfunction was believed to be the major contributor to age-related GI problems due to degeneration of the enteric nervous system and smooth muscles. However, little is known of age-related changes to ICC, the pacemaker cells of the gut. Here I propose to study ICC loss due to senescence of ICC stem cells as a key mechanism contributing to GI aging. My central hypothesis is that changes in epigenetic regulation of molecular pathways controlling stem cell self- renewal are responsible for ICC stem cell senescence and consequent loss of mature ICC in aging. My specific aim is to test the novel hypothesis that reduced epigenetic control of Wnt expression by polycomb group transcriptional co-repressors underlies ICC stem cell senescence. I will quantify ICC and ICC precursors in gastric muscles from the klotho mouse, a model of premature aging, by flow cytometry. In two established ICC stem cell lines, I will study gene expression and the role of Wnt signaling and its epigenetic control by polycomb proteins using real-time RT-PCR, Western immunoblotting and RNA interference. Results from this project may reveal new therapeutic targets to restore ICC stem cells and improve GI health in aging. Moreover, this study will emphasize the role of adult stem cells in aging, and may provide strategies to target aging phenotypes and improve quality of life in a rapidly expanding population of aged people. PUBLIC HEALTH RELEVANCE: Aging-related gastrointestinal disorders including constipation, fecal incontinence, gastroesophageal reflux and reduced food intake occur frequently in the elderly and constitute a significant healthcare burden. Here I propose to study senescence of stem cells for interstitial cells of Cajal, a cell type critical for gastrointestinal motility, as a mechanism of gastrointestinal aging. The results of this study may uncover new tools to restore gastrointestinal function in aged individuals and may lead to new therapies to slow or manage general effects of aging.