Aging Effect on Genome Maintenance during Hepatocyte Regeneration

项目摘要 肝脏是一个重要的器官，具有独特的能力，通过双重机制在损伤后再生。这种能力， 然而，老化会严重损害其性能。大多数研究调查了衰老对肝脏的影响 再生的重点是信号转导途径，驱动细胞周期重新进入和生长的再生 肝细胞正如我的实验室最近的一项研究所显示的那样，这个难题中缺少但关键的一块是， 通过保护肝细胞免于复制来维持肝细胞再生潜力的机制- 导致DNA损伤。这个项目的关键驱动力是一种富含干细胞和癌细胞的蛋白质--核干细胞蛋白 （NS）。到目前为止，尚不清楚NS通路是否在年龄相关性糖尿病中起决定性作用。 衰老过程中肝脏再生的衰退及其表达和活性如何在肝脏中调节 过程为了解决衰老如何影响肝再生的难题，迫切需要确定 衰老调节肝脏NS功能的机制。我的长期目标是确定如何自我- 更新程序有助于衰老过程中成体组织的再生和体内平衡。 本提案的目的是确定NS在与年龄相关的肝再生下降中的作用， 在衰老过程中，它的表达在再生肝细胞中是如何下调的。我们的中央 一种假说认为，通过C/EBPα控制的机制，年龄相关的NS下调设定了阈值， （决定性）水平，限制肝脏的再生潜力。这一假设是基于以下几点提出的：1） NS在再生肝细胞重新进入细胞周期时或之前上调，并发挥重要作用 2）NS缺失损害损伤后的肝再生; 3)NS和Ki 67在静息状态和再生状态下均下调 4）NS启动子含有同源的C/EBPα结合位点， 转录活性被C/EBPα抑制; 5）已知C/EBPα抑制衰老的再生。 肝脏为了检验我们的假设，我们将追求两个具体目标。目的1将确定NS在年龄中的作用- 相关的肝再生下降。目的2将确定驱动NS的转录机制 在肝脏衰老过程中下调。在完成时，我们预计已经确定了NS在 设定一个阈值水平，限制老年肝脏的再生潜力， 在衰老过程中促使NS下调。这些结果将满足理解 支持与年龄相关的肝再生下降的分子和可能促使肝再生的机制 或减轻衰老对肝脏再生的影响。因此，成功完成这项建议将 对解决由年龄依赖性肝再生下降引起的健康问题有直接影响， 对推进衰老对其他成人组织再生影响的研究产生广泛影响。

PROJECT SUMMARY Liver is a vital organ with a unique capability to regenerate after injuries via a dual mechanism. This ability, however, is significantly compromised by aging. Most studies that investigate the aging effect on liver regeneration focus on the signaling pathways that drive the cell cycle reentry and growth of regenerating hepatocytes. A missing but critical piece of the puzzle, as a recent study from my lab has shown, is the mechanism that maintains the regenerative potential of hepatocytes by safeguarding them from replication- induced DNA damage. The key driver of this program is a stem and cancer cell-enriched protein, nucleostemin (NS). To date, it remains unclear whether the NS pathway plays a determinant role in the age-associated decline of liver regeneration and how its expression and activity is regulated in the liver during the aging process. To solve the puzzle of how aging affects liver regeneration, there is a critical need to determine the mechanism by which aging regulates NS function in the liver. My long-term goal is to determine how self- renewal programs contribute to the regeneration and homeostasis of adult tissues during the aging process. The objective of this proposal is to determine the role of NS in age-associated decline of liver regeneration and how its expression is down-regulated in regenerating hepatocytes during the aging process. Our central hypothesis states that age-related NS down-regulation via a C/EBPα-controlled mechanism sets a threshold (determinant) level that limits the regenerative potential of the liver. This hypothesis is formulated based on: 1) NS is up-regulated on or before the cell cycle reentry of regenerating hepatocytes and serves an essential role in protecting them from replicative DNA damage; 2) NS deletion compromises liver regeneration after injuries; 3) the levels of NS and Ki67 are both down-regulated in aged livers under the resting and regenerating conditions compared to young livers; 4) NS promoter contains cognate C/EBPα-binding sites, and its transcriptional activity is inhibited by C/EBPα; and 5) C/EBPα is known to inhibit the regeneration of aged livers. To test our hypothesis, two specific aims will be pursued. Aim 1 will determine the role of NS in age- associated decline of liver regeneration. Aim 2 will determine the transcriptional mechanism that drives NS down-regulation during liver aging. At the completion, we expect to have determined the importance of NS in setting a threshold level that caps the regenerative potential of aged livers, and the transcriptional program that drives the down-regulation of NS during the aging process. These outcomes will fill the need to understand the molecules that underpin the age-related decline of liver regeneration and the mechanisms that may precipitate or alleviate the effect of aging on liver regeneration. A successful completion of this proposal will therefore have a direct impact on resolving the health issues caused by age-dependent decline of liver regeneration and a broad impact on advancing research on the aging effect on the regeneration of other adult tissues.