Defining the Hematopoietic Stem Cell Niche in the Fetal Liver

定义胎儿肝脏中的造血干细胞生态位

• 批准号: 8717379
• 负责人: Jalal Ahmed
• 金额: $ 3.53万
• 依托单位: ICAHN SCHOOL OF MEDICINE AT MOUNT SINAI
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-05-05 至 2015-05-04
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8717379
• 关键词: Address; Adult; Autologous; Autologous Bone Marrow Transplantation; Autologous Transplantation; Automobile Driving; Biological Assay; Blood; Bone Marrow; Breeding; CSPG4 gene; CXCL12 gene; Candidate Disease Gene; Cell Count; Cell Maintenance; Cell Proliferation; Cells; Characteristics; Clinic; Cryoultramicrotomy; Culture Techniques; Data; Development; Diphtheria Toxin; Dysmyelopoietic Syndromes; Embryo; Employee Strikes; Evaluation; Exhibits; Fetal Liver; Fetus; Gene Expression Profile; Genes; Genetic Markers; Growth; Growth Factor; Hematological Disease; Hematopoiesis; Hematopoietic stem cells; High Dose Chemotherapy; Homeostasis; In Vitro; Individual; Lead; Lymphoma; Maintenance; Mesenchymal Stem Cells; Modeling; Multiple Myeloma; Mus; Organ; Organ Culture Techniques; Patients; Pericytes; Physiological; Population; Process; Proliferating; Property; Protocols documentation; RNA Sequences; Regulation; Replacement Therapy; Research; Role; Signal Transduction; Site; Source; Stem cell transplant; Stem cells; System; Testing; Therapeutic; Time; Transplantation; Ursidae Family; arteriole; cell type; chemokine; clinically relevant; comparative; defined contribution; fetal; improved; in vitro Assay; in vivo; insight; leptin receptor; nestin protein; novel; novel strategies; progenitor; public health relevance; recombinase; self-renewal; spatial relationship; stem cell niche; stem cell population; success; tool; transcriptomics

Stem cell transplantation is an important tool to treat several hematological disorders11. Patients with lymphomas or multiple myeloma receive autologous transplantation of mobilized progenitors after receiving high-dose chemotherapy12. The numbers of mobilized progenitors may not be sufficient, especially when repeat autologous transplantations are required13. These data compel us to develop protocols to expand hematopoietic stem cells. Within the fetal liver (FL), hematopoietic stem cells expand dramatically and for this reason, we have focused our efforts on this organ. The HSC population has been highly characterized in the adult and the fetus, and it is clear that in the adult bone marrow (BM), HSCs are primarily non-cycling/quiescent. During development however, the entire hierarchy of blood lineages must grow to serve the needs of the growing embryo. In kind, all HSCs are cycling and the HSC population increases: self renewal of HSCs is evident. The differences in HSCs in the fetus and adult may be attributed to distinct microenvironmental, or niche, signals from the FL and BM. We wish to identify the fetal HSC niche and dissect the mechanisms employed to regulate HSC proliferation.We previously identified a Nestin+mesenchymal stem cell population in the BM that served as a HSC niche. By applying the tools we have used to identify the HSC niche in the BM, we have identified a candidate HSC niche cell in the Fetal Liver (FL), the major site of fetal hematopoiesis. Perhaps not-surprisingly, Nestin+ cells in the FL bear a striking resemblance to those in the BM. Here, we propose to characterize this population with several in vivo and in vitro assays. We will then demonstrate the importance of the FL Nestin+ cells in maintaining HSCs with both in vivo and in vitro approaches. We will use Cre-recombinase to delete a candidate gene, CXCL12, within our Nestin+ population to test for the importance of this chemokine in maintaining HSCs in the FL niche. We will perform RNA-sequencing of FL and BM Nestin+ cells to quantify the differences between BM and FL niches. Comparative transcriptomicsmay give insight into mechanisms by which FL and BM Nestin+ cells regulate HSC self-renewal, quiescence, and differentiation. Further study of the niche will help define how HSCs may be expanded for therapeutic purposes. The identification of niches in the adult and in the embryo allows us a unique opportunity to compare niches where stem cells are quiescent and where they are proliferating in physiological settings and may also give insight into non-physiological growths such as myelodysplastic syndrome. Our preliminary evidence suggests that we have identified a rare cell type in the FL that is enriched for growth factors necessary to support HSCs. By further characterizing this cell population among other potential candidates, we wish to study the mechanisms of HSC expansion.

干细胞移植是治疗多种血液疾病的重要工具11。 患者患有 淋巴瘤或多发性骨髓瘤在接受动员祖细胞后接受自体移植 高剂量化疗12. 动员的祖细胞数量可能不足，特别是当 需要重复自体移植13。 这些数据迫使我们开发协议来扩展 造血干细胞。在胎儿肝脏 (FL) 内，造血干细胞急剧扩增，为此 因此，我们把精力集中在这个机构上。 HSC 群体在成人和胎儿中具有高度特征，并且很明显，在 成人骨髓 (BM) 中的 HSC 主要是非循环/静止的。然而在开发过程中，整个 血统的等级制度必须不断发展以满足胚胎生长的需要。 实质上，所有 HSC 都在循环 HSC 数量增加：HSC 的自我更新是明显的。胎儿与胎儿HSC的差异 成人可能归因于来自 FL 和 BM 的不同微环境或生态位信号。 我们希望 确定胎儿 HSC 生态位并剖析用于调节 HSC 增殖的机制。我们之前 鉴定出BM中的巢蛋白+间充质干细胞群作​​为HSC生态位。 通过应用 我们使用工具来识别 BM 中的 HSC 生态位，我们已经在 BM 中识别出候选 HSC 生态位细胞 胎儿肝脏（FL），胎儿造血的主要场所。 也许并不奇怪，FL 中的 Nestin+ 细胞具有 与 BM 中的那些惊人相似。在这里，我们建议用几个体内特征来表征这个群体 和体外测定。然后我们将证明 FL Nestin+ 细胞在维持 HSC 方面的重要性 体内和体外方法。 我们将使用 Cre 重组酶删除候选基因 CXCL12， 我们的 Nestin+ 群体来测试这种趋化因子在维持 FL 生态位中 HSC 的重要性。 我们 将对 FL 和 BM Nestin+ 细胞进行 RNA 测序，以量化 BM 和 FL 之间的差异 利基市场。 比较转录组学可以深入了解 FL 和 BM Nestin+ 细胞的机制 调节 HSC 的自我更新、静止和分化。 对利基市场的进一步研究将有助于确定如何 HSC 可以出于治疗目的进行扩增。成人和胚胎中生态位的识别 为我们提供了一个独特的机会来比较干细胞静止的位置和它们所处的位置 在生理环境中增殖，也可以深入了解非生理生长，例如 骨髓增生异常综合症。我们的初步证据表明我们在 FL 中发现了一种罕见的细胞类型 富含支持 HSC 所需的生长因子。 通过进一步表征该细胞群 在其他潜在的候选者中，我们希望研究 HSC 扩展的机制。