ACTIVATION OF PURIFIED HEMATOPOIETIC STEM CELLS

血细胞来源于一群造血干细胞 通常被定义为具有自我更新能力的多能细胞 容量。尽管造血细胞的再生能力 系统令人印象深刻，干细胞的复制潜力 然而，这似乎是有限的。因为有很多次 细胞能否分裂是发育过程中的一个重要考虑因素 新的治疗策略，包括干细胞移植， 体外扩增和基因治疗，可能有助于确定 干细胞的复制潜力是人们普遍关心的问题。 之前对纯化的人类“候选”干细胞的研究已经 显示出它们的功能特性在 在个体发育过程中，它们增殖潜力的丧失与 端粒重复数的可测量变化以及 它们表达低水平的端粒酶。在这里，我们建议研究 正常和恶性造血干细胞的生物学特性 细胞端粒酶表达与端粒长度的关系 单个染色体。在这些研究中，克隆传播 正常和白血病前体细胞将通过新的 定量荧光原位杂交技术。这个 拟议研究的具体目的是：1)分析 染色体特异的、依赖复制的端粒缩短 脐带胎肝CD34+CD38-细胞的(亚)克隆 血液和成人骨髓；2)比较端粒核型 正常、骨髓增生异常和白血病细胞来自相同的 为了研究端粒在骨髓增生异常中的作用 疾病和白血病转化；以及3)研究 端粒酶、端粒酶mRNA及相关因子在乳腺癌组织中的表达 正常和恶性干细胞“候选者”与其 增殖潜能及端粒酶作用的检测 染色体特异性端粒长度的抑制物和 这类细胞的增殖特性。总而言之，这些研究 应阐明端粒在正常细胞增殖中的作用 恶性造血干细胞和白血病特异性 染色体异常。

Blood cells originate from a population of hematopoietic stem cells which are typically defined as pluripotent cells with self-renewal capacity. Although the regenerative capacity of the hematopoietic system is impressive, the replicative potential of stem cells nevertheless appears finite. Because the number of times stem cells can divide is an important consideration in the development of novel therapeutic strategies, including stem cell transplantation, ex vivo expansion and gene therapy, studies that may help define the replicative potential of stem cells are of general interest. Previous studies with purified human "candidate" stem cells have shown that their functional properties change dramatically during ontogeny, that loss in their proliferative potential correlates with measurable changes in the number of telomere repeats and that they express low levels of telomerase. Here we propose to study biological properties of normal and malignant hematopoietic stem cells in relation to telomerase expression and telomere length on individual chromosomes. For these studies, clonally propagated normal and leukemic precursor cells will be analyzed by novel quantitative fluorescence in situ hybridization techniques. The specific aims of the proposed studies are: 1) To analyze chromosome specific, replication-dependent telomere shortening in (sub-) clones of purified CD34+CD38- cells from fetal liver, cord blood and adult bone marrow; 2) to compare telomere karyograms of normal, myelodysplastic and leukemic cells from the same patient in order to study the role of telomeres in myelodysplastic disease and leukemic transformation; and 3) To study the expression of telomerase, telomerase mRNA and related factors in normal and malignant stem cell "candidates" in relation to their proliferative potential and examine the effect of telomerase inhibitors on chromosome specific telomere length and the proliferative properties of such cells. Taken together, these studies should clarify the role of telomeraes in the proliferation of normal and malignant hematopoietic stem cells and leukemia specific chromosomal abnormalities.