Epigenetic regulation of stem cell senescence in aging

描述（由申请人提供）：在2000年至2050年期间，美国85岁及以上的人口预计将增加~4倍（www.census.gov）。衰老与包括胃肠道在内的大多数器官功能的衰退有关。与年龄相关的胃肠道变化包括胃食管反流、肠易激综合征、便秘和大便失禁增加，以及更细微的功能障碍，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，并构成了重大的卫生保健负担。GI老化的机制尚不清楚。肠道功能是由胃肠道中多种细胞类型（包括上皮细胞、免疫细胞、平滑肌细胞、神经元和胶质细胞以及Cajal间质细胞）之间的动态相互作用所控制的。直到最近，由于肠神经系统和平滑肌的退化，神经肌肉功能障碍被认为是与年龄相关的胃肠道问题的主要原因。然而，人们对肠道起搏器细胞ICC的年龄相关变化知之甚少。在这里，我建议研究ICC干细胞衰老导致的ICC损失作为促进GI衰老的关键机制。我的主要假设是，控制干细胞自我更新的分子途径的表观遗传调控的变化是导致ICC干细胞衰老和成熟ICC在衰老过程中随之丧失的原因。我的具体目的是验证一个新的假设，即通过多梳组转录共抑制因子减少Wnt表达的表观遗传控制是ICC干细胞衰老的基础。我将通过流式细胞术量化klotho小鼠胃肌肉中的ICC和ICC前体，klotho小鼠是一种早衰模型。在两个已建立的ICC干细胞系中，我将利用real-time RT-PCR、Western immunoblotting和RNA干扰技术，利用polycomb蛋白研究Wnt信号的基因表达和作用及其表观遗传控制。该研究结果可能揭示新的治疗靶点，以恢复ICC干细胞和改善GI健康。此外，该研究将强调成体干细胞在衰老中的作用，并可能为快速增长的老年人群体提供针对衰老表型和改善生活质量的策略。

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.