Dissecting the origins of fetal hemoglobin modulation of sickle cell vaso-occlusion

剖析胎儿血红蛋白调节镰状细胞血管闭塞的起源

• 批准号: 9258476
• 负责人: David Kevin Wood
• 金额: $ 19.21万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-10 至 2019-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9258476
• 关键词: Affect; Animal Model; Biological Assay; Biological Markers; Blood; Blood specimen; Caring; Cells; Cessation of life; Clinical; Clinical Trials; Cytometry; Development; Erythrocytes; Fetal Hemoglobin; Fiber; Flow Cytometry; Goals; Health Care Costs; Hemoglobin A; Hemoglobin F Disease; Hereditary Disease; High Pressure Liquid Chromatography; Human; In Vitro; Individual; Infarction; Link; Measurement; Measures; Microfluidics; Monitor; Organ; Oxygen; Patient Monitoring; Patient-Focused Outcomes; Patients; Polymers; Probability; Quality of life; Risk; Role; Sampling; Sickle Cell; Sickle Cell Anemia; Sickle Hemoglobin; Testing; Therapeutic; Tissues; Treatment Efficacy; Variant; Work; blood rheology; clinical efficacy; hydroxyurea; improved; in vivo; individual patient; mutant; novel therapeutics; patient stratification; polymerization; public health relevance; response; tool

 DESCRIPTION: Sickle cell disease (SCD) is a devastating hereditary disorder that affects more than 13 million people worldwide with health care costs in the U.S. alone exceeding $1 billion per year. The origin of SCD is the ability of a hemo- globin mutant (sickle hemoglobin or HbS) to polymerize into rigid fibers upon deoxygenation. These fibers reduce red blood cell deformability, which leads to large changes in blood rheology and can ultimately result in complete occlusion of the microvasculature, tissue infarction, organ damage, and even death. The only clinically approved therapeutic for SCD, hydroxyurea, is thought to work by inducing synthesis of fetal hemoglobin (HbF). HbF is known to inhibit HbS polymerization in vitro, but average HbF levels in blood correlate only weakly with patient outcomes, and hydroxyurea has widely variable clinical efficacy. Although new therapies have been proposed or are in development, the effect of these potential therapies on vaso-occlusion is difficult to predict without extensive trials in animal models and humans. Ultimately, the missing link is to understand the quantitative rela- tionship between cellular HbF levels and the likelihood of vaso-occlusion. This would allow us to predict the potential efficacy of new therapies and to clinically monitor patients who are receiving HbF inducing therapies such as hydroxyurea. In these studies, we will quantify the relationship between blood HbF levels and the risk of vaso-occlusion. Our primary hypothesis is that the therapeutic efficacy of HbF depends primarily on the distribu- tion of HbF among red blood cells (RBCs). If all RBCs contain more than a threshold percentage of HbF, patients are protected from vaso-occlusion, but having the majority of HbF segregated into only a few cells does not significantly improve patient outcomes. We propose to directly test this hypothesis using flow cytometry to quan- tify single RBC HbF distributions ("HbF heterocellularity"). We will correlate the HbF heterocellularity of patient blood with the risk of vaso-occlusion. Because vaso-occlusions are difficult to study or reproduce in vivo, we have developed a microfluidic platform to study vaso-occlusion in vitro. We will use this platform to quantify the likelihood of occlusion in a blood sample, and we will correlate this measurement with HbF heterocellularity measured from patient samples using quantitative flow cytometry. The result will be a clinical assay that can be used to monitor patien response to hydroxyurea and an assay for clinical trials of new therapies that induce HbF synthesis. Additionally, we anticipate that these studies will elucidate whether HbF is the primary therapeutic mechanism for hydroxyurea.

 描述：镰状细胞病 (SCD) 是一种毁灭性的遗传性疾病，影响全球超过 1300 万人，仅在美国每年的医疗费用就超过 10 亿美元。 SCD 的起源是血红蛋白突变体（镰状血红蛋白或 HbS）在脱氧时聚合成刚性纤维的能力。这些纤维降低了红细胞的变形能力，从而导致血液流变学发生巨大变化，最终导致微脉管系统完全闭塞、组织梗塞、器官损伤，甚至死亡。羟基脲是唯一获得临床批准的 SCD 治疗药物，被认为是通过诱导胎儿血红蛋白 (HbF) 的合成来发挥作用。众所周知，HbF 可以在体外抑制 HbS 聚合，但血液中的平均 HbF 水平与患者预后的相关性很弱，而且羟基脲的临床疗效差异很大。尽管已经提出或正在开发新的疗法，但如果没有在动物模型和人类中进行广泛的试验，很难预测这些潜在疗法对血管闭塞的影响。最终，缺少的环节是了解细胞 HbF 水平与血管闭塞可能性之间的定量关系。这将使我们能够预测新疗法的潜在功效并在临床上 监测正在接受 HbF 诱导疗法（如羟基脲）的患者。在这些研究中，我们将量化血液 HbF 水平与血管闭塞风险之间的关系。我们的主要假设是 HbF 的治疗效果主要取决于 HbF 在红细胞 (RBC) 中的分布。如果所有红细胞中 HbF 的含量超过阈值百分比，患者就可以免受血管闭塞的影响，但将大部分 HbF 分离到少数细胞中并不能显着改善患者的预后。我们建议使用流式细胞术直接检验这一假设，以量化单个红细胞 HbF 分布（“HbF 异细胞性”）。我们将患者血液的 HbF 异细胞性与血管闭塞风险相关联。由于血管闭塞很难在体内研究或重现，我们开发了一个微流体平台来研究体外血管闭塞。我们将使用该平台来量化血液样本中闭塞的可能性，并将该测量结果与使用定量流式细胞术从患者样本中测量到的 HbF 异细胞性相关联。其结果将是一种可用于监测患者对羟基脲反应的临床测定，以及一种用于诱导 HbF 合成的新疗法的临床试验的测定。此外，我们预计这些研究将阐明 HbF 是否是羟基脲的主要治疗机制。