Bone Marrow Niche dysfunction in sickle cell disease

总结/摘要 背景镰状细胞病（SCD）是由β-珠蛋白基因的单一突变引起的，是最常见的镰状细胞病。 一种常见的遗传性血液病。在美国，大约有10万美国人受到影响。 SCD患者患有反复的红细胞镰状化和血管闭塞发作，从幼年开始， 导致急性和慢性疼痛、中风、贫血、感染、器官衰竭和过早死亡。血管闭塞 发作引起缺血再灌注损伤，激活内皮细胞，免疫细胞和凝血 级联。这些过程导致SCD中的慢性炎症状态，与增加的前炎症相关。 炎症细胞因子、TLR4活化和所有器官（包括骨髓（BM））中的氧化应激。 迄今为止，关于炎症如何影响SCD中的BM微环境和HSC功能知之甚少 患者值得注意的是，对人体样本进行的研究很少且有限。初步结果。 我们以前使用不同动物模型的研究表明，TLR4激活和上调 炎症过程中miR155和NF-kB信号转导导致BM生态位、髓系 造血干细胞自我更新的偏斜和丧失。我们在SCD患者中获得的初步结果 在City of Hope参加HSC移植（HSCT）临床试验的样本显示， CD34+祖细胞的频率和数量，产生集落的能力降低， SCD BM衍生的间充质细胞（MSC）中的miR155和NF-kB信号传导。假说.我们假设 SCD诱导的慢性炎症重塑BM生态位并损害SCD患者的HSC功能， 并且这些变化影响移植期间供体HSC的植入。目标和战略。这 将对SCD患者（n = 21）在HSCT前和第+15、+30和+1年时的BM标本进行研究 HSCT后将在BM上进行细胞组分和炎症通路的表征 通过使用互补方法如多参数流式细胞术分析， 免疫组织化学和nanostring测定;将在基线时分离CD34+细胞，用于RNA-seq 并测试集落形成测定和体内移植NSG小鼠的能力; BM和外周血清 将探测炎性细胞因子; MSC将是体外BM衍生的，并分析表征， 持续的炎症信号结果将与HSCT结局相关。年龄匹配 健康供体将用作对照。本案无关这项研究提供了一个独特的机会， 了解人体标本中SCD的生物学。重要的是，解剖参与的机制， 严重SCD的BM生态位功能障碍和炎症状态应提供治疗干预的途径 改善SCD患者的植入和造血重建。

SUMMARY/ABSTRACT Background. Sickle cell disease (SCD) is caused by a single mutation of the -globin gene and is the most common form of inherited blood disorder. In the US, approximately 100,000 of Americans are affected. Patients with SCD suffer from repeated red cell sickling and vaso-occlusion episodes, which, since early age, lead to acute and chronic pain, stroke, anemia, infections, organ failure and premature death. Vaso-occlusion episodes cause ischemia-reperfusion injury, activation of endothelial cells, immune cells and the coagulation cascade. These processes lead to a state of chronic inflammation in SCD, associated with increased pro- inflammatory cytokines, TLR4 activation and oxidative stress in all organs, including the bone marrow (BM). To date, little is known about how inflammation impacts the BM microenvironment and HSC functions in SCD patients. Notably, few and limited studies have been conducted on human samples. Preliminary results. Our previous studies using different animal models have shown that TLR4 activation and upregulation of miR155 and NF-kB signaling during inflammation results in the remodeling of the BM niche, myeloid lineage skewing and loss of hematopoietic stem cell self-renewal. Preliminary results that we obtained in SCD patient samples enrolled in a HSC transplantation (HSCT) clinical trial at City of Hope demonstrated a decrease in frequency and number of CD34+ progenitor cells, decreased ability to generate colonies and increased miR155 and NF-kB signaling in SCD BM-derived mesenchymal cells (MSC). Hypothesis. We hypothesize that SCD-induced chronic inflammation remodels the BM niche and impairs HSC function in SCD patients, and that these changes impact the engraftment of donor HSC during transplant. Aims and Strategy. This study will be conducted on BM specimens of SCD patients (n=21) prior HSCT and at day +15, +30 and +1yr after HSCT. Characterization of the cellular components and inflammatory pathways will be carried on BM biopsies and aspirates by using complementary approaches such as multiparametric flow cytometry analysis, immunohistochemistry and nanostring assays; CD34+ cells will be isolated at baseline, used for RNA-seq and tested for colony-forming assay and ability to engraft NSG mice in vivo; BM and peripheral blood serum will be probed for inflammatory cytokines; MSC will be BM derived in vitro and analyzed characterization and persistence of the inflammatory signature. Results will be correlated with HSCT outcomes. Aged matched healthy donors will be used as controls. Relevance. This study represents a unique opportunity to better understand the biology of SCD in human specimens. Important, the dissection of the mechanisms involved in BM niche dysfunction and inflammatory state in severe SCD should offer avenues for therapeutic intervention to improve engraftment and hematopoietic reconstitution in patients with SCD.