Erythropoiesis - Injury and Recovery

描述（由申请人提供）：我们每秒从骨髓中合成和释放超过200万个红细胞，以维持循环稳态水平。红细胞生成系统的这种大量输出使其成为正常生理功能所必需的过程，但也是对辐射等直接损伤非常敏感的过程。辐射损伤为研究红系细胞损伤、恢复和调控机制提供了一个独特的模型，并使我们能够更全面地了解红细胞生成作为一个动态过程。这项建议的总体目标是更好地了解损伤和恢复的机制后，异种毒性暴露的红系亚致死辐射模拟。通过传统的集落测定结合新的多光谱成像流式细胞术（MIFC）分析获得的初步数据表明，红系祖细胞和前体细胞在4Gy照射后48小时严重耗尽，随后在照射后5天开始快速增加。目的1研究将进一步确定红系祖细胞和前体细胞群体的差异放射敏感性和恢复的时间过程，以及探索亚致死辐射损伤后红系损失的潜在凋亡机制。有趣的是，初步研究结果表明，晚期红系祖细胞（CFU-E）可以独立于更不成熟的（BFU-E）祖细胞恢复。基于这些数据，假设晚期红系祖细胞在修饰的应激红细胞生成反应中增殖，该反应负责辐射后红系恢复波。因此，目标2将研究在传统的应激红细胞反应中重要的内源性化合物的作用，如促红细胞生成素（EPO），干细胞因子（SCF）和糖皮质激素，以及它们各自的信号通路对CFU-E细胞的刺激和随后的增殖在红细胞系从辐射中恢复期间。最后，目标3将联合收割机结合目标1中提出的损伤和目标2中提出的恢复的潜在机制，通过确定外源性给予细胞因子如EPO和SCF是否可以减少损伤和增强红系细胞系的恢复。 总的来说，这些实验将提供一个更彻底的了解正常的造血，通过调查其潜在的敏感性辐射和其恢复后的反应损伤的机制。这些研究将最终导致新的治疗方法，以保护和减轻造血系统从致染色体断裂剂，如辐射和化疗。

DESCRIPTION (provided by applicant): We synthesize and release more than 2 million red blood cells per second from our bone marrow to maintain circulating steady-state levels. This massive output of the erythropoietic system makes it a process that is essential for normal physiological function but also one that is exquisitely sensitive to direct injury such as radiation. Radiation injury provides a unique model for study of erythroid lineage injury, recovery, and regulation mechanisms and allows for a more thorough understanding of erythropoiesis as a dynamic process. The overall aim of this proposal is to better understand the mechanisms of injury and recovery of the erythroid lineage following xenotoxic exposure as modeled by sublethal radiation. Preliminary data obtained through traditional colony assays in combination with a novel multispectral imaging flow cytometry (MIFC) analysis indicate that erythroid progenitors and precursors are severely depleted at 48 hours post 4 Grey irradiation followed by a rapid increase beginning at 5 days post- irradiation. Aim 1 studies will further define the time course of differential radiosensitivity and recovery of erythroid progenitor and precursor populations as well as explore potential apoptotic mechanisms underlying erythroid loss following sublethal radiation injury. Interestingly, preliminary findings suggest that late-stage erythroid progenitors (CFU-E) may recover independent of more immature (BFU-E) progenitors. Based on these data, late-stage erythroid progenitors are hypothesized to proliferate in a modified stress erythropoiesis response that is responsible for the wave of erythroid recovery post-radiation. Therefore, Aim 2 will investigate the role of endogenous compounds important in the traditional stress erythroid response, such as erythropoietin (EPO), stem cell factor (SCF), and glucocorticoids, and their respective signaling pathways on the stimulation and subsequent proliferation of CFU-E cells during the recovery of the erythroid lineage from radiation. Finally, Aim 3 will combine proposed mechanisms underlying injury in Aim 1 and recovery in Aim 2 by determining if exogenous administration of cytokines such as EPO and SCF can reduce injury and enhance recovery of the erythroid lineage. Overall, these experiments will provide a more thorough understanding of normal hematopoiesis by investigating both its underlying sensitivity to radiation and the mechanisms of its recovery response following injury. These studies will ultimately lead to new treatments to protect and mitigate the hematopoietic system from clastogenic agents such as radiation and chemotherapy.