Signaling Mechanisms in Stem Cell Plasticity

描述（由申请人提供）：造血干细胞（HSC）长期以来被认为仅限于形成淋巴和骨髓谱系的血细胞。驻留在骨髓微环境中的HSC可以在动物的一生中重新填充受照射的移植受体的造血系统，使HSC成为基因治疗应用的重要靶点。然而，最近的研究表明，HSC的亚组分可能有能力促进不同的细胞类型，如神经元，肝细胞和肌细胞。这些令人惊讶的发现与长期存在的教条相矛盾，并为这些潜在的多能干细胞的鉴定和表征开辟了一个重要的新研究领域。最近的研究表明，诱导心肌梗死后骨髓细胞群的治疗效果。虽然这些研究表明，HSC有潜力成为功能性心肌细胞后，直接注射，骨髓移植，或苦参碱诱导的动员，这些研究是高度侵入性的，需要微妙的小鼠手术。我们建议建立一个更简单的方法，诱导心肌病后注射阿霉素的小鼠，从而提供一个损伤模型，也是临床相关的癌症化疗与蒽环类药物。这种方法将用于测试造血干细胞的心脏分化潜力，并将确定gp 130/STAT 3信号通路的激活是否促进HSC对心肌细胞再生的贡献。gp 130/STAT 3通路激活胚胎基因表达程序，导致心脏肥大和心脏营养素和血管内皮生长因子水平升高。目的#1将确定在心脏细胞中过表达STAT 3的转基因小鼠是否将提供最佳微环境以刺激骨髓来源的前体细胞的最大心脏分化。目的#2将确定供体骨髓细胞中STAT 3的过表达是否将为心脏分化提供细胞内在选择性优势。对具有这种潜力的细胞的前瞻性鉴定可以避免使用人类胚胎干细胞的担忧。由于这种发育可塑性可能被利用来创造新的干细胞疗法，因此需要产生用于有效测定转分化潜力的系统。干细胞介导的组织再生中涉及的信号机制的表征代表了一个新的研究领域，这对于理解干细胞对不同环境刺激的反应背后的调节机制至关重要。

DESCRIPTION (provided by applicant): Hematopoietic stem cells (HSCs) have long been regarded as restricted to formation of blood cells of both the lymphoid and myeloid lineages. HSCs residing in the bone marrow microenvironment can repopulate the hematopoietic system of irradiated transplant recipients for the lifetime of the animal making HSCs important targets for gene therapy applications. However, recent studies have suggested that a subfraction of HSCs may have the ability to contribute to diverse cell types such as neurons, hepatocytes, and myocytes. These surprising findings contradict the long-standing dogma and have opened an important new field of investigation into identification and characterization of these potential pluripotent stem cells. Recent studies have shown the therapeutic efficacy of bone marrow cell populations following induced myocardial infarction. While these studies have suggested that HSCs have potential to become functional cardiomyocytes following direct injection, bone marrow transplant, or cytokine-induced mobilization, these studies are highly invasive and require delicate mouse surgery. We propose to establish a simpler method by inducing cardiomyopathy following injection of mice with doxorubicin, thus providing an injury model that is also clinically relevant for cancer chemotherapy with anthracycline drugs. This approach will be used to test for hematopoietic stem cell cardiac differentiation potential and will determine whether activation of the gp130/STAT3 signaling pathway promotes HSC contribution to cardiomyocyte regeneration. The gp130/STAT3 pathway activates an embryonic gene expression program resulting in hypertrophy and increased levels of cardiotrophin and vascular endothelial growth factor in the heart. Aim #1 will determine whether transgenic mice overexpressing STAT3 in cardiac cells will provide an optimal microenvironment to stimulate maximal cardiac differentiation from bone marrow derived precursor cells. Aim #2 will determine whether overexpression of STAT3 in donor bone marrow cells will provide a cell intrinsic selective advantage for cardiac differentiation. Prospective identification of cells with this potential could circumvent concerns about using human embryonic stem cells. Generation of systems for efficient assay of transdifferentiation potential are needed since this developmental plasticity might be exploited to create new stem cell therapies. Characterization of signaling mechanisms involved in stem cell-mediated tissue regeneration represents a new area of research that will be critical for understanding the regulatory mechanisms behind the response of stem cells to diverse environmental stimuli.