Project 2

项目2：项目概要 贫血是早产最常见的并发症之一。新生儿贫血的治疗 主要基于测量的血红蛋白浓度（Hb）。由于患者血液管理实践 变得更加保守，血液学家已经利用较低的Hb阈值来触发输血， 最近的研究引起了对限制性输血做法的健康后果的关注。 与此一致，我们最近的多中心前瞻性队列研究表明， 早产儿（Hb ≤ 8 g/dL）与坏死性小肠结肠炎（NEC）的发生有关， 肠道疾病和早产儿主要死亡原因。我们的长期目标是确定 调节贫血相关肠道损伤和NEC的机制。我们的核心假设是 贫血引起巨噬细胞功能的改变，直接使新生儿易受肠损伤， NEC。我们的假设是建立在我们最近发现的基础上的，即早产儿的贫血可以 导致肠氧合受损，如通过肠系膜区域的近红外光谱（NIRS）测量的 氧饱和度（MES-rSO 2）。贫血的早产儿也可表现出血清中 促炎干扰素γ（IFNγ）。使用临床前模型，我们的初步数据也表明， 严重贫血不仅诱导肠道缺氧，还驱动肠道巨噬细胞产生IFNγ。 由于贫血可诱导巨噬细胞中的缺氧诱导因子1α（HIF 1 α），而HIF 1 α可驱动巨噬细胞-巨噬细胞复合物， IFNγ的产生，这些结果表明贫血诱导的肠道氧合变化驱动HIF 1 α- 诱导肠巨噬细胞产生IFNγ。此外，我们的初步数据表明， 贫血导致肠损伤，先前的研究表明IFNγ可以直接损害上皮细胞， 屏障功能，贫血诱导的巨噬细胞产生IFNγ可能直接损害细胞的完整性。 肠粘膜除了驱动额外的促炎单核细胞的正反馈回路之外， 巨噬细胞分化、巨噬细胞IFNγ产生、屏障功能障碍、肠损伤和最终 NEC。为了检验我们的中心假设，从而实现项目2的总体目标，我们将 追求以下具体目标：目标1：确定贫血及其治疗（红细胞输血）对 早产儿血清细胞因子和单核细胞分化。目的2：定义贫血及其 治疗（RBC输注或重组人促红细胞生成素（rHuEPO）给药） 巨噬细胞细胞因子分泌和肠损伤。我们认为这些平行的目标 提供了一个独特的机会来确定贫血对肠损伤和NEC的影响，因此将有助于 为未来的验证研究和试验提供信息，以优化新生儿贫血的管理。

PROJECT 2: PROJECT SUMMARY Anemia represents one of the most common complications of preterm birth. Treatment of neonatal anemia is largely based on measured hemoglobin concentrations (Hb). As patient blood management practices have become more conservative, and neonatologists have utilized lower Hb thresholds to trigger transfusions, recent studies have raised concerns regarding the health consequences of restrictive transfusion practices. Consistent with this, our recent multicenter prospective cohort investigation demonstrated that anemia in preterm infants (Hb ≤8g/dL) is associated with the development of necrotizing enterocolitis (NEC), a serious intestinal disease and major cause of death in preterm neonates. Our long-term objective is to identify key mechanisms that regulate anemia-associated gut injury and NEC. Our central hypothesis is that severe anemia induces alterations in macrophage function that directly predisposes neonates to intestinal injury and NEC. Our hypothesis is formulated on the basis of our recent discovery that anemia in preterm infants can result in impaired gut oxygenation as measured by near infrared spectroscopy (NIRS) of mesenteric regional saturation of oxygen (MES-rSO2). Anemic preterm infants can also display significant increases in serum levels of proinflammatory interferon gamma (IFNγ). Using a preclinical model, our preliminary data also demonstrate that severe anemia not only induces gut hypoxia, but also drives IFNγ production by intestinal macrophages. As anemia can induce hypoxia-inducible factor 1α (HIF1α) in macrophages and HIF1α can drive macrophage- production of IFNγ, these results suggest that anemia-induced changes in gut oxygenation drive HIF1α- induced IFNγ production by intestinal macrophages. Furthermore, as our preliminary data demonstrate that anemia induces intestinal injury and previous studies demonstrate that IFNγ can directly compromise epithelial barrier function, anemia-induced production of IFNγ by macrophages may directly compromise the integrity of the gut mucosa in addition to driving a positive feedback loop of additional proinflammatory monocyte and macrophage differentiation, macrophage IFNγ production, barrier dysfunction, intestinal injury and ultimately NEC. To test our central hypothesis and therefore accomplish the overall objectives of Project 2, we will pursue the following specific aims: Aim 1: Define the impact of anemia and its treatment (RBC transfusion) on serum cytokines and monocyte differentiation in pre-term infants. Aim 2: Define the impact of anemia and its treatment (RBC transfusion or recombinant human erythropoietin (rHuEPO) administration) on gut macrophage cytokine secretion and intestinal injury using a preclinical model. We think these parallel aims provide a unique opportunity to define the impact of anemia on intestinal injury and NEC and therefore will help inform future validation studies and trials designed to optimally manage neonatal anemia.