HSC Diversity, in aging, ontogeny, and transformation

 描述(申请人提供)：血液系统为身体提供氧气和营养，也包含防止感染、癌症和失血的细胞。所有血细胞的适当产生来自成人骨髓中一小部分[~20,000]造血细胞，称为造血干细胞。这些干细胞是唯一可以制造更多造血干细胞的造血细胞，这种特性被称为自我更新。干细胞经过许多中间步骤才形成成熟的血细胞类型--通常分为两类：髓样细胞(红细胞、血小板、粒细胞和巨噬细胞)和淋巴样细胞(B、T和NK细胞)。在每一个连续的步骤中，都有一个细胞通过包含一些命运而排除其他命运而变得越来越专业化。我们想要了解为什么在幼年小鼠和人类中占主导地位的某些造血干细胞在单细胞水平上产生大致相同数量的淋巴样细胞和髓系细胞(平衡)；为什么在老年小鼠和人类中占主导地位的其他单个干细胞产生非常少的新淋巴样细胞，而产生更多的髓系细胞(髓系偏向)。我们的初步证据支持这样的假设，即无论个人的年龄如何，平衡的干细胞总是平衡的，而偏向髓系的干细胞总是偏向的；这些偏向髓系的干细胞在老年个体中具有选择性优势。我们描述的实验在人类和老鼠身上提供了多种方法来回答这个问题。例如，在老鼠身上，我们已经开发出一种方法，在这种方法中，我们可以确定单个细胞及其克隆后代的位置和生活史，而不需要在体外分离它们来研究它们的性质。我们使用所有这些方法来研究干细胞如何获得偏向，如何在体内移动，它们是如何受到影响的--以及它们的祖细胞在正常的血液形成、血液遗传疾病以及白血病前期和白血病的发展过程中是如何受到影响的。通常由于遗传或后天遗传异常，可能会发生许多血液疾病，如携带红细胞的氧气丧失，或关键的凝血元素，或抗感染细胞。例如，我们已经证明，在人类白血病前期，表征这些疾病的基因变化都发生在单个干细胞中，其中一些干细胞扩张形成克隆。一些克隆最终积累了更多的突变，因此有可能确定特定患者和患者疾病的突变顺序。在一些白血病前期，例如在骨髓增生异常综合征[MDS]中，存在一种或多种类型的成熟血细胞缺陷，这些突变的个体突变和添加顺序为该细胞缺陷的原因提供了强有力的线索。当白血病前期MDS克隆进展为急性白血病时，我们已经确定了与白血病进展和疯狂生长一致的突变类型。因此，跟踪正常血细胞发育的各个阶段并分析相关的基因变化可以更好地了解癌症[或其他血液疾病]，并导致新的有效治疗方法。

 DESCRIPTION (provided by applicant): The blood system provides oxygen and nourishment to the body, and also contains cells that protect against infections, cancers, and blood loss. The appropriate production of all blood cells derives from a tiny fraction [~1 in 20,000] of blood forming cells in the adult bone marrow called blood forming stem cells. These stem cells are the only blood forming cells that can make more blood forming stem cells, a property called self-renewal. The stem cell transitions through many intermediate steps before giving rise to mature blood cell types-which are generally classified into two groups: myeloid (red blood cells [RBCs], platelets, granulocytes and macrophages) and lymphoid (B, T and NK cells) cells. At each successive step, there is a cell that becomes increasingly specialized by including some fates and excluding others. We wish to inquire why some blood forming stem cells, predominant in young mice and people, at the single cell level make roughly equivalent numbers of lymphoid and myeloid cells (balanced); and why other single stem cells, predominant in aged mice and humans, make very few new lymphoid cells, and make many more myeloid cells (myeloid-bias). Our preliminary evidence favors the hypothesis that a balanced stem cell is always balanced, no matter the age of the individual, while a myeloid biased stem cell is always biased; and these myeloid biased stem cells have a selective advantage in the aging individual. The experiments we describe provide multiple ways to answer this question in humans and mice. For example, in mice we have developed a method wherein we can determine the location and life history of single cells and their clonal progeny without the need to isolate them outside the body to study their properties. We bring all of these approaches to study how stem cells get their bias, move through the body, and how they are affected-and how their progenitor daughter cells are affected in normal blood formation, in genetic diseases of the blood, and in the development of preleukemias and leukemias. A number of blood diseases such as loss of oxygen carrying RBCs, or critical blood-clotting elements, or infection fighting cells can occur, usually due to inherited or acquired genetic abnormalities. We have shown, for example, that in human preleukemias the genetic changes that characterize these diseases, all occur in the single stem cells, some of which expand to make clones. Some clones eventually accumulate more mutations, so it is possible to determine the order of mutations for a particular patient and the patient's disease. In some preleukemias, such as in myelodysplastic syndrome [MDS], where there is a deficiency of one or more types of the mature blood cells, the individual mutations and order of addition of those mutations give strong clues about the cause of that cell's deficiency. When the preleukemic MDS clone progresses to acute leukemia, we have identified the kinds of mutations consistent with the progression and wild growth of the leukemia. Thus following the stages of normal blood cell development and analyzing the associated genetic changes can lead to better understanding of the cancer [or other blood diseases] and lead to new effective therapies.